JP2020192700A - Manufacturing method of optical film - Google Patents

Abstract

To provide a manufacturing method of an optical film, which can smoothly extrude even a resin pellet having a large friction coefficient and can efficiently produce a good optical film.SOLUTION: A manufacturing method of an optical film includes: a supply process for supplying pellet type resin from a feed device to a single-screw extruder; and an extrusion process for extruding the supplied resin with the extruder. The feed device includes a metering feeder, the extruder includes a barrel and a screw provided within the barrel, and the extrusion process involves pushing the resin from an upstream side to a downstream side of the barrel by rotating the screw. The barrel includes a supply unit, a compression unit, and a measuring unit in this order from the upstream, and in the manufacturing method, a supply amount of the resin is adjusted so that a pressure inside the barrel in the compression unit is 40 MPa or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing an optical film.

One of the methods for manufacturing an optical film is a manufacturing method by melt extrusion molding. The general melt extrusion molding process includes a supply step of supplying the resin to the extruder and an extrusion step of extruding the supplied resin by the extruder. As the resin supplied in the supply process, a solid resin having a shape such as pellets that is easy to handle is used. In the extrusion process, the resin is melted in the extruder and the molten resin is extruded from the extruder. This is further passed through a molding device such as a die, whereby the resin is molded into the shape of a film.

Examples of general extruders include single-screw extruders and twin-screw extruders. In the production of an optical film by melt extrusion, a single-screw extruder is particularly preferably used from the viewpoint of suppressing deformation due to shearing of the resin and making it a simple device. A general single-screw extruder includes a barrel having a cylindrical cavity and a screw provided in the barrel, and has a structure for pushing resin from the upstream side to the downstream side of the barrel by rotating the screw. ..

Various resins are mentioned as the resin used as the material of the optical film, and various new resins have been proposed in recent years. For example, a resin containing a block copolymer containing a cyclic hydrocarbon group-containing compound hydride unit and a chain hydrocarbon compound hydride unit has high adhesive strength, low retardation, and flexibility. It has been proposed as a resin having characteristics such as height (for example, Patent Document 1).

JP-A-2018-97121

Some of the new resins proposed in recent years as materials for optical films have unprecedented properties. For example, when a resin pellet containing a specific block copolymer described above is extruded by a single-screw extruder, the screw pellet is due to the large coefficient of friction between the barrel inner wall and the pellet. The supply may be defective, making it difficult to carry out the extrusion process. Specifically, problems such as clogging of the resin in the compression section of the extruder and interruption of the extrusion operation due to excessive torque on the screw may occur.

Therefore, an object of the present invention is to provide a method for producing an optical film, which can smoothly extrude even a resin pellet having a large coefficient of friction and can efficiently produce a good optical film. There is.

As a result of studies for solving the above-mentioned problems, the present inventor has found that the above-mentioned problems can be solved by adopting a specific apparatus and extrusion conditions used in the extrusion process, and completes the present invention. It was.
That is, according to the present invention, the following are provided.

[1] A method for producing an optical film, comprising a supply step of supplying a pellet-shaped resin from a feeding device to a single-screw extruder and an extrusion step of extruding the supplied resin by the extruder.
The feed device includes a quantitative feeder.
The extruder includes a barrel and a screw provided within the barrel, the extrusion step comprising pushing the resin from the upstream side to the downstream side of the barrel by rotating the screw.
The barrel includes a supply part, a compression part, and a measuring part in this order from the upstream.
The temperature _TF of the inner wall of the barrel in the supply unit is the following formula (1):
Tg-60 ° C ≤ T _F ≤ Tg + 10 ° C ... (1)
However, Tg is the glass transition temperature of the resin.
At the temperature _TF , the coefficient of kinetic friction μ _F between the barrel inner wall material in the supply section and the pellet is 1.00 or more.
A production method comprising controlling the supply amount of the resin in the supply step by the quantitative feeder so that the pressure inside the barrel in the compression portion in the extrusion step is 40 MPa or less.
[2] The manufacturing method according to [1], wherein the arithmetic mean roughness of the inner wall of the barrel in the supply section is 0.5 μm or more and 10 μm or less.
[3] The length L _{F of} the supply portion of the barrel and the length L _{C of the} compression portion are expressed by the following equation (2):
L _F x 1.5 ≤ L _C ... (2)
The production method according to [1] or [2], which satisfies the above conditions.
[4] The supply step includes supplying the blocking prevention material together with the pellet-shaped resin, and the supply amount of the blocking prevention material is 100% by weight of the total of the pellet-shaped resin and the blocking prevention material. The production method according to any one of [1] to [3], which is 0.5% by weight or more.
[5] The resin contains a polymer selected from the group consisting of an alicyclic structure-containing polymer, a cellulosic polymer, a polyethylene terephthalate polymer, an acrylic polymer, and a mixture thereof [1]. The method for producing an optical film according to any one of [4].

According to the method for producing an optical film of the present invention, even a resin pellet having a large coefficient of friction can be smoothly extruded, and a good optical film can be efficiently produced.

FIG. 1 is a side view schematically showing an example of a melt extrusion molding machine used in the manufacturing method of the present invention. FIG. 2 is a vertical cross-sectional view schematically showing a measuring device having a coefficient of dynamic friction μ _F.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof.

[1. Outline of manufacturing method of optical film]
The method for producing an optical film of the present invention includes a supply step of supplying pellet-shaped resin from a feeding device to a single-screw extruder, and an extrusion step of extruding the supplied resin by an extruder. The feeding device includes a quantitative feeder. The extruder includes a barrel and a screw provided within the barrel. The extrusion process involves pushing the resin from the upstream side to the downstream side of the barrel by rotating the screw.

An example of a melt extrusion molding machine used in the production method of the present invention, and a supply process and an extrusion process using the melt extrusion molding machine will be described with reference to FIG.
FIG. 1 is a side view schematically showing an example of a melt extrusion molding machine used in the manufacturing method of the present invention. In FIG. 1, for convenience of illustration, among the components of the melt extrusion molding machine 100, the barrel 114 shows a vertical cross section cut along a plane passing through the central axis 113AX of the screw 113. Further, the members other than the screw 113, the barrel 114, and the screw 130 show a vertical cross section cut along a surface passing through the central axis 130AX of the screw 130.

In FIG. 1, the melt extruder 100 includes a feed device and an extruder connected to the feed device. The feeding device includes a hopper 110 and a metering feeder connected to the bottom of the hopper 110. The metering feeder is a device that can adjust the supply rate of pellets supplied to the extruder to a certain value. In this example, the quantitative feeder is a screw feeder that includes a barrel 114 and a screw 113 provided therein.

The extruder includes a barrel 120 and a screw 130 provided inside the barrel 120. In the following description, for convenience of distinction, the barrel and screw in the quantitative feeder may be referred to as "quantitative feeder barrel" and "quantitative feeder screw". Similarly, barrels and screws in extruders may be referred to as "extruder barrels" and "extruder screws."

The hopper 110 is provided with its lower portion fitted to the upstream portion of the metering feeder barrel 114. The resin pellet 201 introduced from the upper opening 111 of the hopper 110 flows out from the lower opening of the hopper 110 and is supplied into the quantitative feeder barrel 114. By rotating the metering feeder screw 113 around its central axis 113AX, the pellet 201 in the metering feeder barrel 114 can be conveyed downstream.

In FIG. 1, only one screw feeder is shown as a screw feeder constituting the metering feeder, but the mode of the metering feeder in the feed device is not limited to this, and for example, two or more screw feeders are provided. It may be, for example, a biaxial feeder including a combination of two screw feeders. By adopting the biaxial feeder, a large amount of pellets can be stably received from the hopper, and a smooth supply with a large variable width of the supply amount can be easily achieved. Further, unlike the melt extrusion process, the pellet supply process can be operated at a temperature sufficiently lower than the resin melt temperature, so that it is not necessary to consider the occurrence of defects such as modification due to resin shearing. ..

Further, the mode of the quantitative feeder is not limited to that having a screw feeder, and may be any mode in which the supply rate of pellets can be adjusted.

In the supply step, only the pellet-shaped resin may be supplied, but in addition to the pellet-shaped resin, any other material may be supplied together. Examples of such optional materials include additives for smooth extrusion. Examples of additives include anti-blocking materials. Examples of the blocking preventive material include talc, calcium carbonate, silica, zinc stearate, aluminum hydroxide, saturated fatty acid bisamide, calcium tertiary phosphate, dimethylsilicon and the like. Saturated fatty acid bisamide is preferable, and ethylene bisstearic acid amide is preferable. More preferred. Kao Wax EB-FF is a trade name for ethylene bisstearic acid amide. The supply amount of the blocking prevention material may be preferably 0.5% by weight or more, more preferably 0.55% by weight or more, based on 100% by weight of the total of the pellet-shaped resin and the blocking prevention material. The upper limit of the supply amount of the blocking prevention material is not particularly limited, but may be 1.0% by weight or less. Such an blocking prevention material may be contained in an optical film obtained by carrying out the production method of the present invention.

The pellet 201 transported downstream of the metering feeder barrel 114 falls from the downstream opening 112 of the feed device and flows into the extruder barrel 120 from the resin inlet 121 of the extruder barrel 120, whereby the feeding process is achieved. The barrel. The supplied pellets 201 are subjected to an extrusion process by the extruder barrel 120 and the extruder screw 130.

The extruder screw 130 includes a shaft 131 and blades 132 provided around the shaft. By rotating the extruder screw 130 around the central shaft 130AX, the pellet 201 in the extruder barrel 120 is pushed out from the upstream to the downstream in the extruder barrel. The blade 132 has a spiral structure so that the rotation of the extruder screw 130 can push the contents of the extruder barrel 120 downstream. In the example of FIG. 1, the spiral pitch of the blade 132 of the extruder screw 130 is constant.

In the extruder barrel 120, the supply section 120F, the compression section 120C, and the measuring section 120M are defined in this order from the upstream side, depending on the thickness of the shaft 131 of the extruder screw 130. The supply unit 120F is a unit that supplies the pellet 201 supplied into the extruder barrel by the supply process to the compression unit, and the compression unit 120C pressurizes and heats the pellet 201, whereby the pellet 201 is made uniform. The portion to be made into molten resin, and the measuring unit 120M is a portion for extruding the molten resin into a process further downstream from the extruder at a constant flow velocity.

In the compression unit 120C, the shaft 131 has a tapered shape that is thin on the upstream side and thick on the downstream side. In the compression unit 120C, the extruder screw 130 is provided with such a tapered shaft 131, and the spiral pitch of the blade 132 is constant, so that the resin is compressed as the resin is extruded downstream. The pellet-shaped resin is uniformly supplied from the supply unit 120F to the compression unit at a constant supply rate, and the compression unit performs compression and appropriate heating from the outside of the extruder barrel 120. It can be heated and melted. As a result, it is possible to achieve extrusion of a resin in a good molten state with less air contamination and less contamination of unmelted gel and the like.

In the supply unit 120F and the measuring unit 120M, the shaft 131 has a constant thickness. The configuration provided with a shaft having such a constant thickness is a configuration intended for extrusion at a constant flow rate. For example, in the measuring unit 120M, since the thickness of the shaft 131 is constant and the pitch of the spiral of the blade 132 is constant, the resin can be extruded from the extruder barrel discharge port 129 at a constant flow rate.

Unlike the device of FIG. 1, when the feeding device does not involve a metering feeder and the pellets are fed from the hopper to the extruder by their own weight, the pellets are filled into the feeder 120F of the barrel 120 of the extruder. Will be done. All of the filled pellets are subjected to extrusion from the supply unit 120F to the compression unit 120C. Therefore, for example, the feeding speed of the pellets from the hopper to the extruder cannot be set to be lower than the extrusion capacity of the screw in the feeding unit 120F. On the other hand, when the feeding device is provided with a fixed quantity feeder, the feeding speed of pellets from the feeding device to the extruder can be controlled regardless of the extrusion speed in the feeding section of the extruder. For example, from the feeding device. The speed at which the pellets are supplied to the extruder can be set to be lower than the screw extrusion capacity of the supply unit 120F.

Since the extrusion of the resin in the supply section 120F in the extruder barrel 120 is a process close to the extrusion with compression in the compression section 120C, it is affected by the extrusion conditions in the compression section 120C, whereas the pellets in the quantitative feeder The transport of 201 may set its conditions independently of compression. For example, the metering feeder barrel 114 and the extruder barrel 120 are provided as separate barrels so that their temperatures can be adjusted independently. Therefore, for the convenience of smooth transportation in the quantitative feeder, the transportation temperature in the quantitative feeder can be set to a temperature sufficiently lower than the glass transition temperature of the resin (for example, room temperature). Further, since these are provided so that the pellets quantitatively conveyed in the quantitative feeder barrel 114 fall into the extruder barrel 120, the quantitative feeder screw 113 can be used for high compression such as compression in the compression unit 120C. It does not have to have a shape and strength to withstand. Therefore, the quantitative feeder screw 113 may be a screw having a thin shaft as a shaft, or may be a shaftless screw. Therefore, the space for transporting the pellets in the fixed quantity feeder barrel 114 can be made a large space. As a result, stable transportation can be easily achieved.

[Characteristics of manufacturing method in supply process and extrusion process]
In the manufacturing method of the present invention, the temperature _TF of the inner wall of the barrel in the supply unit is the following formula (1):
Tg-60 ° C ≤ T _F ≤ Tg + 10 ° C ... (1)
Meet. In formula (1), Tg is the glass transition temperature of the resin.
Furthermore, in the manufacturing method of the present invention, at a temperature T _F, and the inner wall of the barrel material in the supply section, of a pellet, the dynamic friction coefficient mu _F is 1.00 or more.
Further, in the manufacturing method of the present invention, the supply amount of the resin in the supply step is controlled by a quantitative feeder so that the pressure inside the barrel in the compression section in the extrusion step is 40 MPa or less.

In the supply section, in order to achieve appropriate compression and heating in the compression section, the resin pellets are required to be extruded downstream at a constant flow rate and stably supplied to the compression section. However, among the new resins recently proposed as materials for optical films, the coefficient of dynamic friction with a material such as a metal material constituting the inner wall surface of the barrel when molded into pellets is a resin conventionally used. In some cases, the value may be 1.00 or more, which is very high compared to. When extruding such pellets, the extruding into the compression section can be excessive due to the high coefficient of friction between the barrel inner wall and the pellets. When such excessive extrusion occurs, undesired phenomena such as operation stop due to overload on the extruder screw and generation of unmelted gel due to incomplete melting of the resin may occur. According to what the present inventor has found, in such a case, a feed device including a quantitative feeder is adopted, and further, in the feeding step, the pressure in the barrel in the compression section in the extrusion step is 40 MPa or less. By controlling the amount of resin supplied by the quantitative feeder, excessive extrusion is suppressed and smooth extrusion becomes possible. The pressure inside the barrel in the compression portion can be preferably 35 MPa or less, more preferably 30 MPa or less. The lower limit of the pressure is not particularly limited, but may be, for example, 5 MPa or more. In the compression section, the pressure may not be constant from the upstream end to the downstream end, and the pressure on the downstream side where compression proceeds may be larger than the pressure on the upstream side. In this case, the pressure can be measured at the central portion at the same distance from both the upstream end and the downstream end of the compression portion, and the measured value can be adopted as the pressure inside the barrel of the compression portion.

More specifically with reference to the example of FIG. 1, by adjusting the operating speed of the quantitative feeder screw 113, the pellet feeding speed from the feed device to the extruder is made smaller than the screw extrusion capacity of the feeding unit 120F. It can be controlled to speed. By performing such control, it is possible to prevent excessive extrusion from the supply unit 120F to the compression unit 120C. Therefore, by adopting such a configuration, even when pellets having a large μ _{F and a} high tendency for excessive extrusion are used, excessive extrusion can be suppressed and smooth extrusion can be performed. Such control can be performed based on the pressure value in the barrel in the compression unit 120C detected by an appropriate pressure detecting device (not shown) provided in the barrel 120 and the pressure value detected by the device. Specifically, when the detected pressure value becomes higher than the set value, the pellet supply rate from the quantitative feeder is decreased, and when the detected pressure value becomes lower than the set value, the pellet supply rate from the quantitative feeder is increased. Can be control. By setting such a set value to a desired value of 40 MPa or less and performing control, the pressure inside the barrel in the compression unit can be set to a desired value.

With respect to the formula (1), the temperature _TF is (Tg-60) ° C., preferably (Tg-55) ° C. or higher, more preferably (Tg-50) ° C. or higher, and (Tg + 10) ° C. or lower. When the temperature _TF is within the above preferable range, the temperature of the pellet in the compression section can be smoothly raised to a desired temperature, and the resin is welded to the extruder screw in the supply section, and the compression section is used. Undesirable phenomena such as resin clogging can be further satisfactorily reduced.

The time of the extrusion process, the temperature T _C of the inner wall of the barrel in the compression _section, and the temperature T _M of the inner wall of the barrel in the metering unit is not particularly limited, it can be appropriately adjusted to a temperature suitable for carrying out the extrusion process. Specifically, the temperature _{T C} of the inner wall of the barrel in the compression unit is preferably (Tg-50) ℃ or higher, more preferably (Tg-40) ℃ or higher, preferably (Tg + 80) ℃ or less, more preferably It is (Tg + 50) ° C. or lower. Temperature _{T M} of the inner wall of the barrel in the metering section is preferably (Tg) ° C. or higher, more preferably (Tg + 30) ℃ or higher, preferably (Tg + 100) ℃ or less, more preferably (Tg + 80) ℃ or less.

The temperature of the inner wall of the barrel can be adjusted by heating from the outside of the barrel with a heating device. More specifically with reference to the example of FIG. 1, in each of the supply unit 120F, the compression unit 120C, and the measurement unit 120M of the barrel 120, an appropriate heating device (not shown) is arranged on the outside of the barrel. By heating the barrel thereby, the temperature of the inner wall of the barrel can be raised to a desired temperature. Further, a temperature measuring device such as a thermoelectric pair is provided on or near the surface of the inner wall of the barrel, the temperature of the inner wall of the barrel is monitored, and the output of the heating device is adjusted based on the monitored temperature to obtain the desired temperature of the inner wall of the barrel. Can be adjusted to a value.

In the manufacturing method of the present invention, the coefficient of kinetic friction μ _F is 1.00 or more, and can be 1.10 or more, 1.20 or more, or even 1.30 or more. Even if μ _F has such a large value, according to the present invention, smooth extrusion is possible, and therefore smooth optical film can be produced. The upper limit of the dynamic friction coefficient μ _F is not particularly limited, but may be, for example, 2.00 or less.

The dynamic friction coefficient μ _F is a dynamic friction coefficient at a temperature _TF , and is a dynamic friction coefficient between the barrel inner wall material in the supply portion and the pellets. The "barrel inner wall material in the supply part" is a material having the same properties as the barrel inner wall itself in the supply part or the barrel inner wall in the supply part in measuring the coefficient of dynamic friction with the pellets. For example, when most of the inner wall of the barrel is made of HCr stainless steel, a plate of HCr stainless steel can be used as the "barrel inner wall material in the supply section". The surface roughness can be defined by the arithmetic mean roughness. Since the arithmetic mean roughness Ra of the surface of the inner wall of the barrel can be preferably 0.5 to 10 μm, more preferably 0.8 to 1.6 μm, the arithmetic mean roughness Ra of the barrel inner wall material in the supply portion is also the same. Can be equivalent. The surface roughness can be measured with a roughness measuring instrument (for example, Mitutoyo's small surface roughness measuring instrument Surftest SJ310).

The dynamic friction coefficient μ _F can be measured in a measurement system using pellets used in carrying out the present invention and a barrel inner wall material having a surface shape having no groove in the supply section. The measurement system of the dynamic friction coefficient μ _F will be described with reference to FIG. FIG. 2 is a vertical cross-sectional view schematically showing a measuring device having a coefficient of dynamic friction μ _F. In FIG. 2, the measuring device 300 includes a disk-shaped rotary table 310, a disk-shaped metal plate 320 placed on the upper surface of the rotary table 310, and a probe 330 installed on the upper side of the metal plate 320. The rotary table 310 includes a base 311 and a gripper 312 for gripping the metal plate 320, and the plurality of grippers 312 are pressed against the metal plate 320 in a state of being urged toward the central axis 310AX, whereby the metal is pressed. The plate 320 is fixed to the rotary table 310. The turntable 310 further comprises a shaft 313. When a rotational force is applied to the rotary table 310 via the shaft 313 by an appropriate rotary device (not shown), the rotary table rotates about the central axis 310AX. The measuring device 300 further includes a temperature control device (not shown), whereby the temperature of the metal plate 320 is kept at a constant desired temperature. The metal plate 320 corresponds to the barrel inner wall material in the supply section. The probe 330 includes a cylinder 331 containing the pellet 201 and a load transducer 332 installed inside the cylinder 331, which brings the pellet 201 into contact with the metal plate 320 at a constant pressure. Keeping the temperature of the metal plate 320 at the temperature _TF , rotating the rotary table 310 around the shaft 310AX, applying pressure to the pellet 201 with the transducer 332, measuring the pressure and the torque to the shaft 313, and measuring these. From the result, the dynamic friction coefficient μ _F can be obtained.

The material constituting the barrel is usually a metal such as stainless steel, and in particular, HCr stainless steel (stainless steel having a hard chrome plating treatment on the surface) is preferable from the viewpoint of pressure resistance and scratch resistance on the surface. .. Further, for observing the inside of the barrel, a part of the barrel may be a transparent material such as hard glass or quartz glass.

As the internal dimensions of the extruder barrel, dimensions suitable for the extrusion process can be appropriately selected. The inner diameter D of the barrel can be 40 to 120 mm. The length L of the barrel can be 1,200 to 3,600 mm. The length of the barrel is the length of the lumen unless otherwise noted. The ratio of the barrel length L to the barrel diameter D, that is, L / D, can be 26 to 34. The length of the barrel, or part of the length of the barrel, can be expressed as a relative value to the diameter D of the barrel. For example, the length of a barrel with an L / D of 30 can be expressed as 30D. When the inner diameter D of the barrel is 40 mm, the barrel having a length of 30 D is a barrel having a length of 1,200 mm.

The length L _F of the feed section of the extruder _barrel, the length L _C of the compression _section, and the respective lengths of the metering unit L _M, as appropriate, may a length suitable for the extrusion process. For example, _{L F} is 5D~12D, _{L C} is 9D~14D, _{L M} may be a length within the range such 9D～13D.

The length L _F of the supply part of the extruder barrel and the length L _C of the compression part are preferably the following formula (2):
L _F x 1.5 ≤ L _C ... (2)
Meet. By L _F and L _C satisfies the equation (2), a barrel pressure in the compression unit, more easily, can be controlled to a desired value.

[Process downstream from extrusion process]
The resin melted and extruded in the extrusion process is further passed through an appropriate device such as a die connected to the barrel discharge port to form a film-like shape, thereby achieving the production of an optical film by melt extrusion. be able to. By continuously supplying the resin, the optical film can be continuously produced by melt extrusion molding, and as a result, a long film can be obtained as the optical film. The "long" film means a film having, for example, 5 times or more the width of the film, preferably 10 times or more, and specifically in a roll shape. A film that has a length that allows it to be wound up and stored or transported. The upper limit of the ratio of the length to the width of the film is not particularly limited, but may be, for example, 100,000 times or less.

In the production method of the present invention, since the extrusion process has the above-mentioned specific characteristics, smooth extrusion can be performed even for resin pellets having a large coefficient of friction, and a good optical film can be efficiently produced. be able to. Specifically, as a resin, while having good properties such as high adhesive strength, low phase difference expression, and high flexibility, a dynamic friction coefficient μ _F is large, and a stable resin in a supply section is used. Even when a resin that is difficult to transport is used as the material, the resin can be extruded smoothly from the supply section to the compression section without clogging of the resin, and unmelted gel or the like can be mixed. Extrusion of the resin in a low and good molten state can be achieved. By supplying the molten resin to the die by such smooth extrusion and performing molding, it is possible to efficiently produce a good optical film.

[Pellet-like resin]
In the production method of the present invention, a pellet-shaped resin is used as the material of the optical film. A "pellet-like" resin is a granular resin that is solid in the feeding process. The specific shape of the pellet is generally a substantially cylindrical shape obtained by cutting the strand, but the present invention is not limited to this, and pellets having any shape can be used. For example, it can be in various shapes such as spherical, elliptical spherical, rectangular parallelepiped, and mixtures thereof. Further, for example, crushed products generated when the resin is formed into these shapes may be included in the category of pellets.

The size of the pellet can be appropriately adjusted to a size suitable for the production method of the present invention. From the viewpoint of obtaining appropriate fluidity and ease of handling, the size of the pellet is preferably 2 mm to 5 mm on average in terms of the number of major axes thereof.

The resin having a pellet-like shape used in the present invention may contain a polymer and an optional component which may be contained if necessary. Examples of the polymer constituting the resin include a polymer selected from the group consisting of an alicyclic structure-containing polymer, a cellulosic polymer, a polyethylene terephthalate polymer, an acrylic polymer, and a mixture thereof. Be done.

Examples of the alicyclic structure-containing polymer include hydrides of copolymers containing aromatic vinyl monomer units and chain-conjugated diene monomer units. The structure of the copolymer that is the precursor of the hydride may be any of a block copolymer, a graft copolymer, a random copolymer, a tapered block copolymer, and the like. From the viewpoint of low-temperature impact strength and tensile strength of the obtained optical film, the copolymer mainly contains a polymer block [A] containing an aromatic vinyl monomer unit as a main component and a chain-conjugated diene monomer unit. It is preferably a block copolymer containing the polymer block [B] as a component.
When the copolymer "contains a monomer unit", it means that "a structural unit derived from the monomer is contained in the copolymer obtained by using the monomer". "Aromatic vinyl monomer unit" means "structural unit derived from aromatic vinyl monomer (aromatic vinyl compound)", and "chain-conjugated diene monomer unit" means "chain-conjugated". It means "a structural unit derived from a diene monomer (chain conjugated diene compound)". However, in the present application, the structural unit is not limited depending on the manufacturing method thereof.
"Mainly composed of aromatic vinyl monomer unit" means "containing more than 50% by weight of aromatic vinyl monomer unit", and "mainly composed of chain conjugated diene monomer unit". "To do" means "contains more than 50% by weight of the chain conjugated diene monomer unit".

The tapered block copolymer means a block copolymer containing not only a block copolymer portion but also a random copolymer portion, or a block copolymer in which the composition ratio of the block copolymer portion continuously changes. The tapered block copolymer may be a block copolymer containing a random copolymer having A and B compositions in a bonding portion between the block copolymer A and the block copolymer B, and may be a block copolymer. It may be a block copolymer in which the A and B compositions continuously change at the bonding portion between A and the block copolymer B.
Hereinafter, the composition and structure when the copolymer is the block copolymer described above will be described in detail, but the structure of the copolymer is not limited to the block copolymer, but is limited to this description. It's not a thing.

The weight average molecular weight (Mw) of the copolymer is preferably 7,000 or more, more preferably 10,000 or more, further preferably 12,000 or more, preferably 190000 or less, and preferably 150,000 or less. More preferably, it is more preferably 100,000 or less. The molecular weight distribution (Mw / Mn) of the copolymer is preferably 6 or less, preferably 5 or less, and even more preferably 4 or less. By having the polymerization average molecular weight and the molecular weight distribution within such a range, molding into a film can be facilitated, and the characteristics of the obtained film can be improved. The "weight average molecular weight" and "molecular weight distribution" of the polymer can be measured using the methods described in the examples herein.

Examples of the aromatic vinyl monomer capable of forming an aromatic vinyl monomer unit include styrene and derivatives thereof, and specifically, styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, and the like. 4-Methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 4-monochromostyrene, dichlorostyrene, 4-monofluorostyrene , And 4-phenylstyrene and the like. Among these, those containing no polar group in order to reduce hygroscopicity, specifically, styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropyl Styrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, and 4-phenylstyrene are preferable, and styrene is particularly preferable because of its easy availability in the industry. One of these may be used alone, or two or more of them may be used in combination at any ratio.

The chain-conjugated diene monomer capable of forming the chain-conjugated diene monomer unit is not particularly limited, but one that does not contain a polar group is preferable in order to reduce the hygroscopicity. Preferred examples thereof include 3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Among these, 1,3-butadiene and isoprene are particularly preferable because of their easy industrial availability. One of these may be used alone, or two or more of them may be used in combination at any ratio.

The content ratio of the aromatic vinyl monomer unit in the polymer block [A] is preferably 80% by weight or more, more preferably 80% by weight or more, when all the repeating units in the polymer block [A] are 100% by weight. It is 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 100% by weight. When the content ratio of the aromatic vinyl monomer unit in the polymer block [A] is 80% by weight or more, the microphase separation domain derived from the polymer block [A] in the copolymer hydride is maintained. It is possible to maintain the tensile strength and the heat resistance of the aromatic monomer block.

The polymer block [A] may contain monomer units other than the aromatic vinyl monomer unit, and such other monomer units are chain conjugated diene monomer units. May be good. Further, as the monomer capable of forming other monomer units, those containing no polar group are preferable in order to reduce the hygroscopicity, and for example, ethylene, propylene, 1-butene, 1-pentene, 1- Chain olefins such as hexene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-eicosene, 4-methyl-1-pentene, 4,6-dimethyl-1-heptene; vinyl Cyclic olefins such as cyclohexane can be mentioned.
When the copolymer which is a block copolymer has a plurality of polymer blocks [A], the monomer compositions of the plurality of polymer blocks [A] may be the same or different.

The content ratio of the chain-conjugated diene monomer unit in the polymer block [B] is preferably 60% by weight or more, more preferably 60% by weight or more, when all the repeating units in the polymer block [B] are 100% by weight. Is 80% by weight or more, more preferably 90% by weight or more, and particularly preferably 100% by weight. When the content ratio of the chain conjugated diene monomer unit in the polymer block [B] is 60% by weight or more, the glass transition temperature (Tg) derived from the polymer block [B] in the copolymer can be obtained. It is possible to maintain the impact strength at a low temperature at a preferable height.

The polymer block [B] may contain monomer units other than the chain-conjugated diene monomer unit, and such other monomer units are aromatic vinyl monomer units. Alternatively, the other monomer unit may be formed from the chain olefin and the cyclic olefin described in the section of "Polymer block [A]".
When the copolymer which is a block copolymer has a plurality of polymer blocks [B], the monomer compositions of the plurality of polymer blocks [B] may be the same or different.

The block copolymer can be a polymer containing two or more polymer blocks [A] and one or more polymer blocks [B]. The number of polymer blocks [A] in the block copolymer is usually 5 or less, preferably 4 or less, more preferably 3 or less, and even more preferably 2. The number of polymer blocks [B] in the block copolymer is usually 4 or less, preferably 3 or less, more preferably 2 or less, and even more preferably 1.

The weight fraction of the total aromatic vinyl monomer unit in the block copolymer in the entire block copolymer is wA, and the full-chain conjugated diene monomer unit in the block copolymer is the entire block copolymer. The ratio of wA to wB (wA: wB) is preferably 20:80 to 60:40, more preferably 25:75 to 60:40, and even more preferably 25:75 to 60:40, where wB is the weight component of the block. , 40:60 to 60:40. By setting wA: wB in this range, the low temperature impact resistance, rigidity, etc. of the obtained film can be improved.
wA: wB is the amount of aromatic vinyl monomer, chain-conjugated diene monomer and other vinyl-based compounds used in the polymerization of the block copolymer in the process of producing the block copolymer, and gas chromatography. The weight fraction of each monomer unit shall be calculated from the polymerization conversion rate of the monomer used at the completion stage of polymerization of each block of the block copolymer measured using Graffiti (GC) to the polymer. Can be done.

The block form of the copolymer, which is a block copolymer, may be a chain type block or a radial type block, but a chain type block is preferable because of its excellent mechanical strength. Further, the copolymer which is a block copolymer has one or more structures in which the polymer blocks [A] are bonded to both ends of the polymer block [B] (that is, a structure in which ABA is arranged in this order). It is preferable to have it in.
Particularly preferred forms of the copolymer, which is a block copolymer, are a triblock copolymer (ABA) in which a polymer block [A] is bonded to both ends of the polymer block [B], and a triblock copolymer (ABA). , The polymer block [B] is bonded to both ends of the polymer block [A], and the polymer block [A] is bonded to the other ends of the two polymer blocks [B]. Polymers (ABBA) are mentioned, with triblock copolymers (ABA) being the most preferred.

By hydrogenating the unsaturated bonds in the above-mentioned copolymers (including, for example, carbon-carbon unsaturated bonds in the main chain and side chains, and carbon-carbon unsaturated bonds in the aromatic ring), the copolymer weight is obtained. A coalesced hydride can be obtained. The copolymer hydride can be, for example, a block copolymer hydride having a structure obtained by hydrogenating a block copolymer.

The hydrogenation rate of the copolymer hydride obtained by hydrogenation is preferably 90 mol% or more, preferably 97 mol% or more, and more preferably 99 mol% or more. When the hydrogenation rate is 90 mol% or more, the weather resistance can be improved. The "hydrogenation rate" indicates the ratio of hydrogenated unsaturated bonds to the total unsaturated bonds contained in the copolymer. The hydrogenation rate of the entire hydride, the hydrogenation rate of the carbon-carbon unsaturated bond derived from the chain conjugated diene compound, and the hydrogenation rate of the carbon-carbon unsaturated bond derived from the aromatic vinyl compound are, for example, It can be determined by measuring ¹ H-NMR of a copolymer and a copolymer hydride.

The weight average molecular weight (Mw) of the copolymer hydride is preferably 7,000 or more, more preferably 10,000 or more, further preferably 12,000 or more, preferably 190000 or less, and 150,000 or less. It is more preferable that the amount is 100,000 or less. The molecular weight distribution (Mw / Mn) of the copolymer hydride is preferably 7 or less, preferably 6 or less, and even more preferably 5 or less. By having the polymerization average molecular weight and the molecular weight distribution within such a range, molding into a film can be facilitated, and the characteristics of the obtained film can be improved.

The block copolymer hydride may be a substance in which only the carbon-carbon unsaturated bonds of the main chain and the side chains derived from the chain-conjugated diene compound of the block copolymer are selectively hydrogenated, or a block. Even a substance obtained by hydrogenating the carbon-carbon unsaturated bond of the main chain and the side chain derived from the chain-conjugated diene compound of the copolymer and the carbon-carbon unsaturated bond of the aromatic ring derived from the aromatic vinyl compound. It may be a mixture thereof.

When only the main chain and side chain carbon-carbon unsaturated bonds derived from the chain-conjugated diene compound of the block copolymer are selectively hydrogenated, the main chain and side chain carbon-carbon unsaturated bonds are hydrogenated. The rate is usually 95% or more, preferably 97% or more, more preferably 99% or more, and the hydrogenation rate of the carbon-carbon unsaturated bond of the aromatic ring derived from the aromatic vinyl compound is usually 10% or less. It is preferably 5% or less, more preferably 3% or less.
Here, "hydrogenating the carbon-carbon unsaturated bond of the main chain and the side chain" means "hydrogenating the double bond derived from the chain-conjugated diene compound in the block copolymer". , "Hydrogenating the carbon-carbon unsaturated bond of an aromatic ring" means "hydrogenating a double bond derived from an aromatic ring in a block copolymer".

When hydrogenating the carbon-carbon unsaturated bonds of the main chain and side chains derived from the chain-conjugated diene compound of the block copolymer and the carbon-carbon unsaturated bonds of the aromatic ring derived from the aromatic vinyl compound, The hydrogenation rate is 90% or more, preferably 95% or more, more preferably 99% or more of the total carbon-carbon unsaturated bond.

The above-mentioned copolymer hydride and the ethylenically unsaturated silane compound may be reacted (silane-modified) in the presence of a peroxide to introduce an alkoxysilyl group into the copolymer hydride. ..
The alkoxysilyl group to be introduced can be a group having various structures corresponding to the ethylenically unsaturated silane compound used for silane modification, which will be described later. In particular, a methoxysilyl group and an ethoxysilyl group are preferable, and a methoxysilyl group is more preferable, from the viewpoint of favoring the adhesiveness between the obtained optical film and other members and other properties. Here, the alkoxysilyl group may be directly bonded to the copolymer hydride, or may be bonded via a divalent organic group such as an alkylene group or an alkyleneoxycarbonylalkylene group.

As the ethylenically unsaturated silane compound used for silane modification, a compound capable of introducing an alkoxysilyl group into the copolymer hydride by reacting with the copolymer hydride (for example, graft polymerization) can be appropriately selected. Examples of such ethylenically unsaturated silane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, p-styryltrimethoxysilane, and 3 − Methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane and the like. Among these, vinyltrimethoxysilane and vinyltriethoxysilane are preferable, and vinyltrimethoxysilane is more preferable. One of these may be used alone, or two or more of them may be used in combination at any ratio.
The amount of the ethylenically unsaturated silane compound used is usually 0.1 parts by weight or more and 10 parts by weight or less, preferably 0.2 parts by weight or more and 5 parts by weight or less, more preferably 0.% by weight, per 100 parts by weight of the copolymer hydride. It is 3 parts by weight or more and 3 parts by weight or less.

As the peroxide used for silane modification, a peroxide having a half-life temperature of 170 to 190 ° C. for 1 minute is preferably used. For example, t-butylcumyl peroxide, dicumyl peroxide, di-t-hexyl peroxide, 2 , 5-Dimethyl-2,5-di- (t-butylperoxy) hexane, di-t-butyl peroxide, di- (2-t-butylperoxyisopropyl) benzene and other organic peroxides. .. One of these may be used alone, or two or more of them may be used in combination at any ratio.
The amount of peroxide used is usually 0.05 parts by weight or more and 2 parts by weight or less, preferably 0.1 parts by weight or more and 1 part by weight or less, more preferably 0.2 parts by weight, per 100 parts by weight of the copolymer hydride. More than parts and less than 0.5 parts by weight.

The amount of alkoxysilyl group introduced into the copolymer hydride by performing silane modification is preferably 0.1 part by weight or more, preferably 0.5 part by weight or more, per 100 parts by weight of the copolymer hydride. It is more preferably 1 part by weight or more, further preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and further preferably 3 parts by weight or less.

The weight average molecular weight (Mw) of the copolymer hydride (silane modified product) obtained by the above silane modification is usually that of the copolymer hydride used as a raw material because the amount of alkoxysilyl group introduced is small. Not much different from that, it is preferably 7,000 or more, more preferably 10,000 or more, further preferably 12,000 or more, preferably 190000 or less, more preferably 150,000 or less, and more preferably 100,000. The following is more preferable. When the polymerization average molecular weight of the silane modified product is 7,000 or more, the mechanical strength of the silane modified product can be increased, and when it is 190000 or less, the processability of the silane modified product can be ensured.
The molecular weight distribution of the modified silane is preferably 7.5 or less, preferably 6.5 or less, and even more preferably 5.5 or less. When the molecular weight distribution is 7.5 or less, the processability and mechanical strength of the silane modified product obtained from the copolymer hydride can be improved.
The molecular weight distribution (Mw / Mn) of the silane modified product is such that the silane modification is performed in the presence of a peroxide, so that the cross-linking reaction and the cleavage reaction of the polymer occur at the same time, so that the copolymer hydride used as a raw material It tends to be larger than that.

The method for producing the copolymer hydride is not particularly limited, and a production method in which known methods are appropriately combined can be used. For example, the production method described in JP-A-2018-97121 or the production method may be appropriately modified as necessary.

The ratio of the alicyclic structure-containing polymer in the resin constituting the pellet can be adjusted to a desired ratio from the viewpoint of obtaining an optical film having desired characteristics. Such a ratio is preferably 80% by weight to 100% by weight, more preferably 90% by weight to 100% by weight, still more preferably 95% by weight to 100% by weight, and particularly preferably 98% by weight to 100% by weight.

Examples of cellulosic polymers include triacetyl cellulose (Tg (glass transition temperature): 160 to 180 ° C.). Examples of the polyethylene terephthalate-based polymer include polyethylene terephthalate (Tg: 70 ° C., Tc: 250 to 255 ° C.). Examples of the acrylic polymer include polymethyl methacrylate (Tg: 90 ° C.) and ethyl polymethyl methacrylate (Tg: 100 ° C.).

The resin constituting the pellet may contain an arbitrary component in combination with the above-mentioned polymer. Examples of arbitrary components include inorganic fine particles; stabilizers such as antioxidants, heat stabilizers, ultraviolet absorbers, and near-infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments. ; And antistatic agents. As these arbitrary components, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio. However, from the viewpoint of remarkably exerting the effect of the present invention, it is preferable that the content ratio of any component is small. For example, the total ratio of any components is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, further preferably 10 parts by weight or less, and particularly preferably 5 parts by weight or less, based on 100 parts by weight of the polymer. preferable. Further, since the amount of any component contained in the resin is small, bleed-out of any component can be suppressed.

[Optical film]
The optical film obtained by the manufacturing method of the present invention can be usefully used as a member constituting various optical devices such as a liquid crystal display device, a display device such as an organic electroluminescence display device, a display device with a touch panel, and a solar cell. ..

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof.
In the following description, "%" and "part" representing quantities are based on weight unless otherwise specified. Further, the operations described below were performed under normal temperature and pressure conditions unless otherwise specified.

〔Evaluation methods〕
(Weight average molecular weight and molecular weight distribution of copolymer and its hydride and GPC elution curve analysis)
It was measured at a rate of 0.6 cc / min at 40 ° C. as a standard polystyrene-equivalent value by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent. As a measuring device, HLC8320GPC manufactured by Tosoh Corporation was used, and three TSKgel SuperH G5000HLX, G4000HLX, and G2000HLX were connected in series as a column, and the concentration was adjusted to a polymer amount of 4 mg / 1 cc for measurement.

(Hydrogenation rate of copolymer hydride)
The hydrogenation rate (mol%) of the copolymer hydride was determined by ¹ H-NMR measurement (measurement solvent: CDCl ₃ ), and the unsaturated bonds that had disappeared from all the unsaturated bonds present in the copolymer were found. It was derived by calculating the ratio.

(Measurement of glass transition temperature)
According to JIS K 7121-1987 (method for measuring the transition temperature of plastics), the temperature was raised at 10 ° C./min using a differential scanning calorimeter (DSC) to determine the glass transition temperature Tg of the sample.

(Surface roughness)
The surface roughness was measured by a roughness measuring instrument (small surface roughness measuring instrument surf test SJ310 manufactured by Mitutoyo) according to JIS B0633: 2001.

[Production Example 1: Production of pellets]
550 parts of dehydrated cyclohexane, 25 parts of dehydrated styrene, and 0.475 parts of n-butyl ether were placed in a reactor equipped with a sufficiently nitrogen-substituted stirrer, and n-butyllithium (15% n-) was placed while stirring at 60 ° C. (Hexane solution) was added in an amount of 0.90 part to initiate polymerization. The polymerization reaction was carried out at 65 ° C. for 60 minutes. The polymerization addition rate at this point measured by gas chromatography was 99.9%. Next, 50.0 parts of dehydrated isoprene was added, and stirring was continued for 40 minutes as it was. The polymerization addition rate at this point was 99.6%. Then, 25.0 parts of dehydrated styrene was further added, and the mixture was reacted for 60 minutes. The polymerization addition rate at this point was almost 100%. Here, 2.0 parts of methanol was added to stop the reaction. By this reaction, a block copolymer solution was obtained.
The block copolymer in the obtained block copolymer solution has a weight average molecular weight (Mw) of 42900, a molecular weight distribution (Mw / Mn) of 1.03, and S-IS (styrene block-). It was a triblock copolymer of isoprene block-styrene block).

The obtained block copolymer solution is transferred to a pressure-resistant reaction vessel equipped with a stirrer, and a silica-alumina-supported nickel catalyst as a hydrogenation catalyst (product name: T-8400RL, manufactured by Clariant Catalyst Co., Ltd.). 5 parts and 100 parts of dehydrated cyclohexane were added and mixed. The temperature was raised to 180 ° C. in a state where the inside of the reaction was replaced with hydrogen gas at room temperature and pressurized by 2 MPa with a gauge pressure. When the internal temperature of the pressure-resistant reaction vessel reached 180 ° C., hydrogen was not supplied for 20 minutes, and the temperature at 180 ° C. was kept constant. After 20 minutes, the hydrogen pressure was increased to 4.5 MPa and a hydrogenation reaction was carried out for 6 hours (hydrogenation rate: 99.5%). As a result, a hydrogenated block copolymer solution was obtained.
The hydrogenated block copolymer in the obtained hydrogenated block copolymer solution has a molecular weight distribution (Mw / Mn) of 1.66, a weight average molecular weight (Mw) of 37800, and a glass transition temperature of 110. It was ° C.

100 parts of the obtained hydrogenated block copolymer is added with an antioxidant (tetrakis [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane; manufactured by BASF Japan Ltd. After mixing 1.1 parts of "Irganox (registered trademark) 1010"), it was put into a twin-screw extruder ("TEM-37B" manufactured by Toshiba Machine Co., Ltd.) equipped with four die holes having an inner diameter of 3 mmΦ. The resin was formed into a strand-shaped molded product by hot melt extrusion molding using a twin-screw extruder, and then shredded with a strand cutter to obtain pellets of the resin (a1).

The operating conditions of the twin-screw extruder were as follows.
・ Barrel set temperature = 220-230 ° C
・ Die set temperature = 200 ℃
-Screw rotation speed = 145 rpm.
-Feeder rotation speed = 50 rpm.

[Example 1]
The pellet of the resin (a1) obtained in Production Example 1 was supplied to the melt extrusion molding machine schematically shown in FIG. The melt extrusion molding machine 100 includes a feed device, an extruder connected to the feed device, and a T-die (not shown) connected downstream thereof. The feeding device includes a hopper 110 and a metering feeder connected to the bottom of the hopper 110. The quantitative feeder was a biaxial screw feeder including two screw feeders including a barrel 114 and a screw 113 provided inside the barrel 114 in parallel. However, since FIG. 1 is a side view, only one screw feeder on the front side is shown. The extruder includes a barrel 120 and a screw 130 provided inside the barrel 120.

As the extruder in the melt extruder 100, a uniaxial visualization extruder (manufactured by Plastic Engineering Laboratory, barrel inner diameter D = 40 mm, barrel inner length L = 1200 mm (that is, L / D = 30)) was used.

The extruder barrel 120, the supply part by the thickness of the shaft 131 of the extruder screw 130 120F, compression unit 120C, and the metering section 120M is defined, the length _{L F,} the length of the compression section 120C of the supply unit 120F L _C, and the length _{L M} of the metering unit 120M were respectively, 6D (i.e. 240 mm), 12D (i.e., 480 mm) and 12D (i.e., 480 mm).

The inner wall of the extruder barrel 120 is an observation window made of hard glass (Pyrex (registered trademark)) for observing the inside of the barrel, and most of the other (area 80% or more) is made of HCr stainless steel. there were. The arithmetic mean roughness Ra of the inner wall of the barrel 120 other than the groove 122 and the observation window portion was 1.2 μm.

A mixture of pellet 201 and a blocking preventive material (Kao wax EB-FF) was charged into the upper opening 111 of the hopper 110 of the feeding device. In the mixture, the amount of the blocking prevention material was 0.55% by weight based on 100% by weight of the total of the pellet 201 and the blocking prevention material. The charged mixture fell into the metering feeder barrel 114 and was filled in the upstream portion of the metering feeder barrel 114. By rotating the metering feeder screw 113, the mixture was transported from upstream to downstream of the metering feeder barrel 114. The mixture conveyed downstream of the quantitative feeder barrel 114 fell from the downstream opening 112 and flowed into the extruder barrel 120 from the resin inlet 121 of the extruder barrel 120 (supply step).

An extrusion step was performed in which the mixture of pellets 201 and anti-blocking material was extruded from the upstream side to the downstream side of the barrel 120 by rotating the screw 130 at 30 rpm. In the extrusion step, the pellet 201 was heated and melted by adjusting each of the supply unit 120F, the compression unit 120C, and the measurement unit 120M of the barrel 120 to a constant temperature. Temperature, 50 ° C. The inner wall of the barrel temperature _{T F} in the supply unit 120F, 90 ° C. The inner wall of the barrel temperature _{T C} in the compression section 120C, and the inner wall of the barrel temperature _{T M} in the metering section 120M and 160 ° C.. To adjust the temperature of the inner wall of the barrel in each part, the barrel is heated by a heating device provided on the outside of the barrel, the temperature of the inner wall of the barrel is monitored by a thermocouple provided near the surface of the inner wall of the barrel, and the temperature of the heating device is adjusted based on the monitored temperature. This was done by adjusting the output. At the center of the compression unit 120C (at a position equal to both the upstream end and the downstream end of the compression unit 120C), the pressure inside the barrel is measured by a pressure gauge provided on the inner wall of the barrel, and the value is larger than the set value. In this case, the rotation speed of the quantitative feeder screw 113 was decelerated, and if it was smaller than the set value, the rotation speed of the quantitative feeder screw 113 was accelerated, whereby the pressure in the compression unit 120C was kept at the set value. In this embodiment, the set value is 25 MPa. The molten resin was discharged from the barrel discharge port 129. An optical film was continuously produced by supplying the discharged resin to a die and extruding it from the die into a film shape. The thickness of the optical film was set to 100 μm by adjusting the die opening and other operating conditions.

In the extrusion step, the state of extrusion was observed and evaluated from the following viewpoints. The evaluation results are shown in Table 2.
(A) Presence or absence of resin clogging in the compression section 120C (B) Presence or absence of resin wrapping around the screw in the supply section 120F (C) Presence or absence of extruder stop due to screw overload (torque over 60 Nm) (D) Presence or absence of unmelted gel in the resin discharged from the barrel discharge port 129 (E) Surface shape of the obtained optical film: Per 10 cm ^{2 with a} CCD camera surface surface inspection device (MaxEye.CORE / 320C manufactured by FUTEC) Measure the number of foreign substances with a major axis of 5 μm or more.
⊚: 10 or less.
〇: More than 10 pieces to 30 pieces or less.
Δ: More than 30 pieces to 50 pieces or less.
X: Over 50 pieces.
(F) Film thickness accuracy: The film thickness was measured using an infrared film thickness meter (RX-100 manufactured by Kurabou Co., Ltd.), and the maximum value of the deviation between the measured value and the average film thickness was obtained. The measurement points were the film center (the center position in the width direction of the long film), and 10 points were measured at intervals of 10 m in the length direction.
⊚: Average film thickness within ± 0.1 μm.
〇: Average film thickness over ± 0.1 μm to within ± 0.5 μm.
Δ: Average film thickness of more than ± 0.5 μm to within ± 1 μm.
X: Average film thickness over ± 1 μm.
(G) Extrusion status:
〇: There is no screw stop due to overload, and there is no wrapping around the screw.
Δ: There is no screw stop due to overload, but there is winding around the screw.
×: There is a screw stop due to overload.
(H) Comprehensive evaluation:
⊚: Extrusion is good ((G) extrusion condition is ○ or Δ), and both (E) planar and (F) film thickness accuracy are ◎.
〇: Good extrusion, and both (E) planar and (F) film thickness accuracy are ◯ or higher (excluding cases where both (E) planar and (F) film thickness accuracy are ◎).
Δ: Good extrusion, and both (E) planar and (F) film thickness accuracy are Δ or higher (except when both (E) planar and (F) film thickness accuracy are ◯ or higher).
X: Extrusion failure ((G) Extrusion status is ×)

Further, the dynamic friction coefficient μ _F was measured using the measuring device schematically shown in FIG. In FIG. 3, the measuring device 300 includes a disk-shaped rotary table 310, a disk-shaped metal plate 320 placed on the upper surface of the rotary table 310, and a probe 330 installed on the upper side of the metal plate 320. The plurality of grippers 312 were pressed against the metal plate 320 in a state of being urged toward the central axis 310AX, whereby the metal plate 320 was fixed to the rotary table 310. As the metal plate 320, a material having the same material as the inner wall of the barrel 120 used in the extrusion step was selected with respect to the development of the coefficient of friction with respect to the pellet 201. That is, as the rotary table 320, a rotary table 320 having a hard chrome plating treatment on the upper surface thereof was used. The arithmetic average roughness Ra of the upper surface of the rotary table 320 was 1.2 μm, and the Vickers hardness was about 1,100 Hv. A temperature regulator (not shown) was used to keep the temperature of the metal plate 320 at _TF (ie, 50 ° C. in Example 1). A layer-sized pellet 201 was placed in the cylinder 331, a transducer 332 was set on the pellet 201, and a pressure of 2N was applied to the interface between the layer of the pellet 201 and the upper surface of the metal plate 320. In this state, the rotary table 310 was rotated at a peripheral speed of 0.03 cm / s. In this state, the coefficient of dynamic friction μ _F was measured by measuring the torque to the shaft portion 342.

[Examples 2 to 3]
Except for the following changes, the optical film was manufactured and evaluated and the friction coefficient was measured by the same operation as in Example 1. The results are shown in Table 2.
Barrel inner wall temperature _{T F} in the supply unit 120F, the length _{L F} of the supply unit 120F, the length _{L C} of the compression section 120C, the length _{L M} of the metering unit 120M, antiblocking material amount, and the pressure setting of the compression section 120C The values were changed as shown in Table 1. The temperature of the rotary table 320 when measuring the friction coefficient was set to the same temperature as the barrel inner wall temperature _TF in the supply unit 120F.

[Comparative Examples 1 to 3]
Except for the following changes, the optical film was manufactured and evaluated and the friction coefficient was measured by the same operation as in Example 1. The results are shown in Table 2.
-The barrel inner wall temperature _TF and the amount of blocking prevention material in the supply unit 120F were changed as shown in Table 1. The temperature of the rotary table 320 when measuring the friction coefficient was set to the same temperature as the barrel inner wall temperature _TF in the supply unit 120F.
As the feed device, a device having no fixed quantity feeder and having a structure in which pellets charged into the hopper directly flow into the resin input port 121 of the extruder barrel 120 from the opening at the lower part of the hopper was used. Therefore, the pressure inside the barrel was measured at the center of the compression unit 120C by a pressure gauge provided on the inner wall of the barrel without controlling the pressure by controlling the quantitative feeder.

1) Measured value obtained by measuring pressure without control.

As is clear from the results of Examples and Comparative Examples, even in extrusion when the friction coefficient between the barrel inner wall and the pellet is as high as 1.00 or more, the temperature _TF of the barrel inner wall in the supply section is adjusted to a specific range and By adjusting the pressure inside the barrel in the compression section to a specific range, good extrusion with few problems such as clogging of the resin in the compression section of the extruder and interruption of extrusion operation due to excessive torque to the screw can be achieved. Can be achieved.

100: Melt extruder 110: Hopper 111: Hopper upper opening 112: Feeding device downstream opening 113: Quantitative feeder screw 113AX: Central axis 114: Quantitative feeder barrel 120: Extruder barrel 120C: Compressor 120F: Supply unit 120M: Weighing Part 121: Resin inlet 129: Discharge port 130: Extruder screw 130AX: Central shaft 131: Shaft 132: Blade 201: Pellet 300: Measuring device 310: Rotating table 310AX: Central shaft 311: Base 312: Grip 313: Shaft 320: Metal plate 330: Probe 331: Cylindrical 332: Load transducer

Claims (5)

A method for producing an optical film, comprising a supply step of supplying pellet-shaped resin from a feeding device to a single-screw extruder and an extrusion step of extruding the supplied resin by the extruder.
The feed device includes a quantitative feeder.
The extruder includes a barrel and a screw provided within the barrel, the extrusion step comprising pushing the resin from the upstream side to the downstream side of the barrel by rotating the screw.
The barrel includes a supply part, a compression part, and a measuring part in this order from the upstream.
The temperature _TF of the inner wall of the barrel in the supply unit is the following formula (1):
Tg-60 ° C ≤ T _F ≤ Tg + 10 ° C ... (1)
However, Tg is the glass transition temperature of the resin.
At the temperature _TF , the coefficient of kinetic friction μ _F between the barrel inner wall material in the supply section and the pellet is 1.00 or more.
A production method comprising controlling the supply amount of the resin in the supply step by the quantitative feeder so that the pressure inside the barrel in the compression portion in the extrusion step is 40 MPa or less. The manufacturing method according to claim 1, wherein the arithmetic mean roughness of the inner wall of the barrel in the supply section is 0.5 μm or more and 10 μm or less. The length L _{F of} the supply portion of the barrel and the length L _{C of the} compression portion are expressed by the following equation (2):
L _F x 1.5 ≤ L _C ... (2)
The production method according to claim 1 or 2, which satisfies the above conditions. The supply step includes supplying the blocking prevention material together with the pellet-shaped resin, and the supply amount of the blocking prevention material is 0.5 in 100% by weight of the total of the pellet-shaped resin and the blocking prevention material. The production method according to any one of claims 1 to 3, wherein the weight is% by weight or more. The resin according to claim 1 to 4, wherein the resin contains a polymer selected from the group consisting of an alicyclic structure-containing polymer, a cellulosic polymer, a polyethylene terephthalate polymer, an acrylic polymer, and a mixture thereof. The method for producing an optical film according to any one of the following items.

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