JP6861182B2 - Optical film manufacturing method - Google Patents

Description

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

In recent years, the demand for optical films has been increasing. Typical optical films include retardation films, antireflection films, antiglare films and the like.

The optical film is manufactured by a roll-to-roll continuous process using a long film-like support (hereinafter, "continuous film support") in order to improve productivity.
As an example of a method for producing an optical film, a curable layer forming step of applying a coating liquid having a composition of being cured by active energy rays to the surface of a continuous film support and drying the film to form a curable layer was formed. A method is known which comprises a curing step of irradiating a curable layer with active energy rays to cure it, and forming a target optical functional layer on the surface of a continuous film support.
As described above, when the curable layer is cured by irradiating it with active energy rays, it is known that oxygen in the atmosphere is a factor that inhibits the curing reaction of the curable layer.

As a method for curing a coating film applied to a method for producing an optical film, for example, there is a method described in Patent Document 1.
In Patent Document 1, a coating film made of an active ray-curing resin formed on the surface of a traveling strip-shaped flexible support is irradiated with active rays by a plurality of active ray irradiating means to cure the coating film. In the method of curing a film, a coating film is kept in a deoxidized atmosphere until a flexible support irradiated with active rays by one or more active ray irradiation means is run on a next-stage active ray irradiation means. A method for curing a film is disclosed. Then, in Patent Document 1, a closed space is formed between a plurality of active ray irradiating means, an inert gas is supplied into the closed space, and the coating film is irradiated with the active ray. It is disclosed that the flexible support having the above is wound around a heated backup roll.

Further, Patent Document 2 is a method for producing an optical film including a long base film and a cured layer, which includes a base film and a pre-cured layer that can be cured by active energy rays. The base film of the film is cured in a specific state, and the heated base film is cured by irradiating the pre-curing layer with active energy rays in a state of being in contact with a back roll of 30 ° C. or higher. A method for producing an optical film including a step of curing a front layer to obtain a cured layer is disclosed. Further, Patent Document 2 also discloses that the pre-curing layer is irradiated with active energy rays in an inert gas atmosphere.

Further, in Patent Document 3, after providing an active energy ray-curable resin layer on a resin film, the active energy ray-curable resin layer is cured by irradiating the active energy ray-curable resin layer with active energy rays from a light source while transporting the resin film. A method for producing a hard coat film is disclosed, wherein an inert gas is supplied to the surface of an active energy ray-curable resin layer irradiated with active energy rays. Further, Patent Document 3 also discloses that while supporting and transporting a resin film on the back surface of the resin film with a backup roll, irradiation of active energy rays and supply of an inert gas are performed.

On the other hand, when manufacturing an optical film, a film called a long web is used. Since this long web is produced by connecting films to each other by joining, a joint portion which is a connecting portion of the films is formed in the longitudinal direction.
There are various forms of joints depending on the connection method. For example, when an adhesive material having an adhesive layer (so-called adhesive tape) is attached to one side of a base material and connected, each end of the two films to be connected is sandwiched between both sides with the adhesive tape and connected. The joint may differ significantly in rigidity or thermal expansion because the two films to be connected are joined at an unexpectedly small angle, or because the joint is thicker than the film.

Japanese Unexamined Patent Publication No. 2006-247530 Japanese Unexamined Patent Publication No. 2017-111394 JP-A-2009-240921

As described above, various techniques have been studied for the fact that oxygen in the atmosphere inhibits the curing reaction. For example, by supplying an inert gas such as nitrogen gas, the environment in which the curing reaction is performed has a nitrogen ratio. It is desirable to replace it with a highly inert atmosphere.

When nitrogen gas is supplied to the UV irradiation section (reaction chamber) that cures the curable layer (coating film) by irradiating it with active energy rays such as ultraviolet rays (UV) to form an inert atmosphere, it is transported indoors. The film is cooled by the supplied nitrogen gas, and the film temperature tends to decrease. For example, when the film is wound on a backup roll adjusted to a temperature equal to or higher than room temperature (for example, the temperature is adjusted to 120 ° C.) and conveyed to the UV irradiation unit, the surface of the film on the side in contact with the backup roll is, for example, 120 ° C. While the temperature is maintained in the vicinity, the curable layer forming surface of the film on the opposite side is cooled by the nitrogen gas at room temperature (for example, 25 ° C.) supplied to the UV irradiation part, and a temperature difference occurs between the front and back surfaces of the film. become. Due to this temperature difference, irreparable wrinkles may occur on the film.
The strong wrinkles that cannot be recovered here are wrinkles that are derived from twists that have continuous waveforms in the film width direction and are elongated in the film transport direction, and are folded on the surface of the backup roll (so-called "riding wrinkles"). (Riding up wrinkles) ").

In particular, when a long continuous film support (also referred to as "web" in the present specification) in which films are joined and connected to each other is used, an error in the connecting angle at the joint portion which is the connecting portion, or joining is used. Waveform deformation (so-called "") in which the waveform is continuous in the film width direction and the waveform extends long in the film transport direction before and after the joint due to the difference in rigidity or thermal expansion between the portion and the film. There is a tendency for "scratch wrinkles") to occur easily.
Normally, when the joint is separated from the backup roll, the film is stretched on the backup roll to eliminate the wrinkles, but the wrinkles are strong or not stretched well. When they overlap, they may turn into strong wrinkles that cannot be recovered.
In particular, in places other than the joint of the film where wrinkles are weakly generated, the effect on wrinkles does not matter even if there is a certain temperature difference between the front and back of the film (that is, it does not cause run-up wrinkles), but it is on the downstream side of the joint. If the film following the above is conveyed in a state where strong wrinkles are generated and the film with wrinkles has a temperature difference between the front and back due to the backup roll, stress may be applied to the wrinkles and the film may change to run-up wrinkles.

In relation to such a situation, the coating film curing method described in Patent Document 1 among the above-mentioned prior arts is flexible when the coating film of a flexible support having a coating film is irradiated with active rays. A temperature difference is likely to occur between the coating film forming surface side of the sex support and the side in contact with the heated backup roll, wrinkles are likely to occur, and eventually, riding wrinkles are likely to occur.

Further, also in the case of the method for producing an optical film described in Patent Document 2, when the pre-curing layer of the base film having the pre-curing layer is irradiated with active energy rays, the side on which the pre-curing layer of the base film is formed is formed. A temperature difference is likely to occur between the side that comes into contact with the heated back roll and the side that comes into contact with the heated back roll, and there is a concern that wrinkles may occur on the base film.
The method for producing a hard coat film described in Patent Document 3 is also a mode in which an inert gas is supplied to the surface of an active energy ray-curable resin layer irradiated with active energy rays, and there is a temperature difference between the front and back surfaces of the film. When this occurs, the film may have wrinkles on the film due to the temperature difference as described above.

The present disclosure has been made in view of the above.
An object to be solved by one embodiment of the present invention is the case where a curable layer on a continuous film support (web) having a joint portion which is a connecting portion of a film is cured in a state of being exposed to an inert atmosphere. The purpose of the present invention is to provide a method for producing an optical film in which the occurrence of wrinkles on the web is suppressed.

Specific means for solving the problem include the following aspects.
<1> The first step of transporting a continuous film support having a joint portion in which the films are joined and coated with a curable layer, and the inert gas being supplied at the first supply flow rate. It has a second step of irradiating the curable layer of the winding region of the continuous film support wound around the heated backup roll with the active energy ray in the active energy ray irradiation unit.
In the second step, the joint portion is formed at least a part of the time during which the joint portion passes through the active energy ray irradiation portion, and between the point where the continuous film support separates from the backup roll and the point 4 m downstream from this point in the transport direction. Production of an optical film in which the inert gas is supplied at a second supply flow rate for at least one of at least a part of the passage, and the first supply flow rate f1 and the second supply flow rate f2 satisfy the following formula 1. The method.
f1> f2 Equation 1
<2> The joint passes at least a part while the joint passes through the active energy ray irradiation part, and between a point where the continuous film support separates from the backup roll and a point 4 m downstream from this point in the transport direction. The method for producing an optical film according to <1>, wherein the ratio of the second supply flow rate f2 to the first supply flow rate f1 is 50% or less in at least one of at least a part of the space.
<3> The joint passes at least a part while the joint passes through the active energy ray irradiation part, and between a point where the continuous film support separates from the backup roll and a point 4 m downstream from this point in the transport direction. The method for producing an optical film according to <1> or <2>, wherein the ratio of the second supply flow rate f2 to the first supply flow rate f1 is 20% or less in at least one of at least a part of the space.
<4> The method for producing an optical film according to any one of <1> to <3>, wherein the surface temperature of the backup roll is 80 ° C. or higher and 160 ° C. or lower.
<5> In the second step, the supply flow rate of the inert gas is further adjusted within the range satisfying the above formula 1 before the joint portion of the conveyed continuous film support comes into contact with the backup roll. <1> The method for producing an optical film according to any one of <4>.

<6> In the second step, at least a part while the joint portion passes through the active energy ray irradiation portion, and between a point where the continuous film support separates from the backup roll and a point 4 m downstream from this point in the transport direction. The method for producing an optical film according to any one of <1> to <5>, wherein the second supply flow rate f2 is maintained at least for a part while the joint portion passes through.
<7> The method for producing an optical film according to any one of <1> to <6>, which has a third step of preheating a continuous film support coated with a curable layer before the second step. Is.
<8> The method for producing an optical film according to any one of <1> to <7>, wherein the width length of the continuous film support is 200 mm or more and 2000 mm or less.
<9> The method for producing an optical film according to any one of <1> to <8>, wherein the thickness of the continuous film support is 3 μm or more and 100 μm or less.
<10> The method for producing an optical film according to any one of <1> to <9>, wherein the first supply flow rate f1 of the inert gas is 5 m ³ / h or more and 300 m ^{3 / h or less.}
<11> The method for producing an optical film according to any one of <1> to <10>, wherein the total thickness of the laminated body in which the curable layer is formed on the continuous film support is 3.1 μm or more and 115 μm or less. ..

According to one embodiment of the present invention, when the curable layer on a continuous film support (web) having a joint portion which is a connecting portion of the film is cured in a state of being exposed to an inert atmosphere, the web rides on the web. A method for producing an optical film in which the generation of wrinkles is suppressed is provided.

It is the schematic which shows each process of the manufacturing method of the optical film of one Embodiment of this invention. It is the schematic which shows each step of the manufacturing method of the optical film of another embodiment of this invention.

Hereinafter, the method for producing the optical film of the present disclosure will be described in detail.

In the present specification, the term "process" in the first process, the second process, etc. is not limited to an independent process, and the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. If so, it is included in this term.

In the present specification, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively. In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

The method for producing an optical film of the present disclosure includes a first step of transporting a continuous film support having a joint portion to which the films are bonded and coated with a curable layer, and a first supply of an inert gas. It has a second step of irradiating the curable layer of the winding region of the continuous film support wound on the heated backup roll with the active energy ray in the active energy ray irradiation unit supplied by the flow rate.
In the second step, (1) at least a part while the joint portion passes through the active energy ray irradiation portion, and (2) a point where the continuous film support separates from the backup roll and a point 4 m downstream from this point in the transport direction. The inert gas is supplied at a second supply flow rate for at least one of at least a part of the gap between the joints, and the first supply flow rate f1 and the second supply flow rate f2 are expressed by the following equation 1. Meet.
f1> f2 ・ ・ ・ Equation 1

In the present disclosure, the first supply flow rate and the second supply flow rate refer to the volumetric flow rate supplied per hour, and are the amount of substance expressed in units of ^{"m 3 / h".}

Described in Patent Documents 1 to 3 described above in the case where the irradiated body is carried into the UV-irradiated portion where nitrogen gas is supplied to form an inert atmosphere and the curable curable layer is cured in the inert atmosphere. One side of the web is cooled by lowering the ambient temperature due to the supplied nitrogen gas, direct exposure to the supplied nitrogen gas, etc., and a temperature difference occurs between the front and back of the web. In some cases. When there is a temperature difference between the front and back of the web, the web tends to have irreparable wrinkles. In particular, when there is a joint portion that is a connecting portion in the longitudinal direction, such as a long web in which films are joined and connected to each other, wrinkles caused by the joint portion occur when a temperature difference occurs between the front and back of the film. The occurrence of wrinkles becomes remarkable, and wrinkles called wrinkles appear. Then, when the web is conveyed in a state where wrinkles are generated and the joint is separated from the backup roll, the subsequent film may cause irreparable run-up wrinkles on the backup roll triggered by the wrinkles.
Since it is not always easy to eliminate wrinkles after riding wrinkles occur, it is important to prepare an environment in which wrinkles are unlikely to occur before riding wrinkles occur.

In view of the above, in the method for producing an optical film of the present disclosure, a continuous film support (web) having a joint portion in which the films are bonded to each other and having a curable layer coated on the continuous film support (web) is used as a heated backup roll. When irradiating the curable layer in the wrapping region of the web with the active energy ray in the active energy ray irradiation section in which the wound and inert gas is supplied at the first supply flow rate f1, the active energy ray irradiation is particularly performed. At least one of the time during which the joint portion passes through the portion and the time during which the joint portion passes between the point where the continuous film support separates from the backup roll (separation point) and the point 4 m downstream from the separation point in the transport direction (separation point). In at least a part of (preferably both), the inert gas assumes that the first supply flow rate f1 and the second supply flow rate f2 satisfy a specific relationship (Equation 1).
As a result, when an optical film is produced using a web coated with a curable layer (preferably a thin film having a thickness of 3 μm to 100 μm), only one side of the web is cooled by the supplied nitrogen gas. A state in which the generated out-of-plane force is suppressed and wrinkles are likely to occur on the backup roll, for example, an error in the connection angle at the joint portion which is the connection portion of the film, or a difference in rigidity between the joint portion and the film. Alternatively, it is possible to alleviate a state in which the waveform is easily deformed due to a difference in thermal expansion or the like.
In particular, when transporting a web having a joint portion in which films are joined and connected to each other, a temperature difference is likely to occur while the joint portion is on a heated backup roll, that is, in the active energy ray irradiation portion. The effect of suppressing the temperature difference by satisfying is great. In addition, when a specific section after the joint is separated from the backup roll, that is, when the joint is between a point where the web is separated from the backup roll and a point 4 m downstream in the transport direction from this point, the waveform deformation (generally). Tsure wrinkles) tend to disappear. Therefore, if the temperature of the section up to the point 4 m downstream in the transport direction can be adjusted so as not to drop too much, it is possible to effectively prevent the wrinkles from changing to the riding wrinkles.
That is, in the method for producing an optical film of the present disclosure, by satisfying Equation 1 in a certain section, the effect of suppressing the temperature difference generated becomes large, and it is possible to prevent the development of riding wrinkles.

-First step-
In the first step of the present disclosure, a continuous film support having a joint portion in which films are bonded to each other and having a curable layer coated therein is conveyed.

The "continuous film support" refers to a support formed by joining the ends of a plurality of long films to each other to form a longer shape. Therefore, the continuous film support has a joint portion in the elongated direction in which the end portions of the plurality of long films are bonded and connected to each other.

The joint refers to a portion where the ends of a plurality of films are joined to each other and connected to each other, and may be formed on the web at arbitrary intervals.

The form of the joint is not particularly limited. For example, a portion in which the ends of the films to be bonded are overlapped with each other and bonded with an adhesive or the like, and two film ends are abutted against each other on the same plane. The film may be fixed with an adhesive tape (for example, one having an adhesive layer on a base material) on only one side or both sides, or two films may be overlapped and heat-sealed.

A known polymer film can be used as the continuous film support.
Examples of polymer film materials used as continuous film supports include cellulose acylate (eg, cellulose triacetate (triacetyl cellulose, refractive index 1.48; TAC), cellulose diacetate, cellulose acetate butyrate, cellulose acetate pro. Pionate), polyolefin (eg, polyethylene, polypropylene, etc.), polyester (eg, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.), polyether sulfone, acrylic resin (eg, polymethylmethacrylate, etc.), polyurethane, Polycarbonate, polysulfone, polyether, polymethylpentene, polyether ketone, poly (meth) acrylic nitrile, polymer having an alicyclic structure (for example, norbornene resin (trade name "Arton (registered trademark)", JSR), Amorphous polyolefin (for example, trade name "Zeonex (registered trademark)", Nippon Zeon Co., Ltd.) and the like can be mentioned.
Of these, triacetyl cellulose (TAC), polyethylene terephthalate (PET), and a polymer having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable, from the viewpoint of low optical anisotropy and the like.

The thickness of the continuous film support may be determined according to manufacturing suitability, application, user's request, etc., and is preferably in the range of 3 μm to 250 μm, for example. In particular, when the thickness of the continuous film support is thin, wrinkles tend to occur. However, in the present disclosure, by performing the second step described above, a thin continuous film support in the range of 3 μm to 100 μm is applied. The body can be used as a suitable one, and the effect of suppressing the occurrence of wrinkles on the web is more effectively exhibited.
The thickness of the continuous film support is more preferably 15 μm or more from the viewpoint of high applicability to winding on a backup roll, and preferably 80 μm or less from the viewpoint of material cost. Above all, the thickness of the continuous film support is more preferably 20 μm or more and 60 μm or less, and further preferably 30 μm or more and 50 μm or less.

The width of the continuous film support is preferably 200 mm or more and 2000 mm or less, preferably 600 mm or more, in that wrinkles are likely to occur and the effect of suppressing the occurrence of wrinkles on the web is more effectively exhibited. It is more preferably 1500 mm or less.

--Joining process ---
The optical film manufacturing method of the present disclosure may include a step (bonding step) of joining the ends of a plurality of films to form a long continuous film support. When the joining step is provided, the above-mentioned joining portion is formed on the continuous film support.
Joining can be performed using a known joining method.
An adhesive, an adhesive tape (for example, an adhesive material having an adhesive layer on a base material) or the like can be used for joining the films.

--Curable layer forming process ---
In the method for producing an optical film of the present disclosure, a step of applying a curable layer to a continuous film support (curable layer forming step) can be provided before the first step.

This step is preferably performed by using a coating liquid having a composition that is cured by active energy rays, applying this coating liquid on a continuous film support, and drying the coating liquid.

(Application)
For coating, a coating device known as a coating means can be applied.
Examples of the coating device include a curtain coating method, a dip coating method, a spin coating method, a printing coating method, a spray coating method, a slot coating method, a roll coating method, a slide coating method, a blade coating method, a gravure coating method, and a wire bar method. And the like.

(Dry)
For drying, a drying device known as a drying means can be applied.
Examples of the drying means include an oven, a hot air blower, an infrared (IR) heater and the like.

In drying with a warm air blower, warm air may be applied from the surface of the continuous film support opposite to the surface on which the coating liquid is applied, and the surface of the applied coating liquid is diffused so as not to flow with the warm air. A board may be installed.
The drying conditions may be determined according to the type of coating liquid used, the coating amount, the transport speed, and the like. For example, the drying conditions are preferably performed in the range of 30 ° C. to 140 ° C. for 10 seconds to 10 minutes.

Through the above coating and drying, an uncured curable layer that is cured by active energy rays is formed.
The thickness of the curable layer is preferably 0.1 μm or more and 15 μm or less, and more preferably 0.5 μm or more and 5 μm or less. The smaller the total thickness when the curable layer is formed on the continuous film support, the more likely it is that wrinkles will occur in the second step described later. Therefore, the smaller the thickness of the curable layer, the easier it is to obtain the effect of suppressing the occurrence of wrinkles.

The total thickness of the laminated body formed by forming the curable layer on the continuous film support is preferably 3.1 μm or more and 115 μm or less. When the total thickness of the laminate is thin, wrinkles are likely to occur, but in the method for producing an optical film of the present disclosure, the effect of suppressing the occurrence of wrinkles is high when the total thickness is within the above range.

An example of the curable layer forming step will be described with reference to FIG.
As shown in FIG. 1, when the tip of the wound continuous film support (web) F is sent out, first, a coating liquid having a composition of being cured by active energy rays by a coating device 1 which is an example of coating means. Is applied. Then, the curable layer formed by the coating is dried in a drying region in the drying apparatus 2 which is a drying means.
In this way, a curable layer obtained by applying and drying a coating liquid having a composition that is cured by active energy rays is formed on the web.

-Second step-
In the second step of the present disclosure, the curable layer in the winding region of the continuous film support wound on the heated backup roll in the active energy ray irradiation unit in which the inert gas is supplied at the first supply flow rate. Is irradiated with active energy rays.

The active energy ray irradiation unit refers to a region for irradiating at least the curable layer with active energy rays, and the irradiation promotes the curing reaction of the curing component in the curable layer.
Normally, the inert gas is supplied to the active energy ray irradiation unit at the first supply flow rate. When the inert gas is supplied, the inside of the active energy ray irradiation portion is replaced with the inert gas, and an inert atmosphere is formed.

The inert gas may be supplied to the active energy ray irradiation unit by any method. For example, the inert gas may be supplied to the active energy ray irradiation unit from a nozzle installed in the active energy ray irradiation unit at a position where the inert gas can be supplied to the active energy ray irradiation unit. Can be supplied.
The nozzle can be attached to one end of a gas supply pipe connected to the external inert gas supply means at the other end and can discharge (for example, release or inject) the inert gas.
The nozzle for supplying the inert gas may be installed at any position of the active energy ray irradiation unit, and the discharge direction of the inert gas is not limited. As shown in FIG. 1 or 2, for example, the nozzle installation position may be the position where the nozzle 36a and the nozzle 36b are installed, and the arrow direction indicated by the nozzle 36a or the nozzle 36b is used as the inert gas discharge direction. May be good.

The active energy ray irradiation unit may be in a state of being filled with an internal atmosphere heated by the heating means. In this case, the internal atmosphere may be heated by the heating means, and examples thereof include a mode in which the inert gas is heated by the heating means and a mode in which the inner wall of the reaction chamber is heated by the heating means.
When the inert gas is heated by the heating means, the heating means may be, for example, a means for preheating the inert gas supplied from the nozzle 36a into the reaction chamber 3 as shown in FIG. It may be a means for heating the inert gas supplied to the reaction chamber in the reaction chamber. For example, the inert gas supplied to the active energy ray irradiation unit may be supplied after being heated to a temperature range higher than the external temperature of the active energy ray irradiation unit.
As described above, the effect of reducing the occurrence of wrinkles can be further expected by heating the atmosphere of the active energy ray irradiation unit or the supplied inert gas.
With respect to the above points, the method for producing an optical film of the present disclosure has an advantage that it can be carried out at a lower cost than a method of heating the inner wall of an inert gas or a reaction chamber by a heating means.

The first supply flow rate f1 of the inert gas supplied to the active energy ray irradiation unit is preferably ^{5 m} 3 / h or more 300 meters ³ / h or less, 100 m ³ / h or more 300 meters ³ / h, more preferably, 150 meters ³ / It is more preferably h or more and 250 m ³ / h.
The supply flow rate of the inert gas can be measured by attaching a flow meter to the discharge port of the nozzle or the supply pipe connected to the nozzle.

The irradiation of the active energy rays is preferably performed on the continuous film support in the stretched state. As in this step, it is preferable that the continuous film support wound around the backup roll is stretched by applying tension in the longitudinal direction.
The tension applied in the longitudinal direction of the continuous film support on the backup roll is preferably 100 N / m to 600 N / m.

The transport speed of the continuous film support transported on the backup roll is preferably 10 m / min or more and 100 m / min or less, preferably 20 m / min, from the viewpoint of ensuring productivity and improving the irradiation accuracy of active energy rays. More preferably, it is 60 m / min or less.

The lap angle of the continuous film support with respect to the backup roll is preferably 60 ° or more, more preferably 90 ° or more.
The lap angle is defined as the transport direction of the continuous film support when the continuous film support comes into contact with the backup roll and the transport direction of the continuous film support when the continuous film support is separated from the backup roll. The angle that becomes.

(Active energy ray)
The active energy ray used in this step is not particularly limited as long as it can impart energy capable of generating active species to the curable layer to be irradiated.
Examples of the active energy ray include α ray, γ ray, X ray, ultraviolet ray (UV), infrared ray, visible ray, electron beam and the like. Of these, as the active energy ray, ultraviolet rays or electron beams are preferable, and ultraviolet rays are more preferable, from the viewpoint of curing sensitivity and availability of an apparatus.

(light source)
Examples of the light source for irradiating the active energy ray include the above-mentioned light source for irradiating the active energy ray. The light source is preferably a light source that irradiates ultraviolet rays from the viewpoint of curing sensitivity and availability of an apparatus.
Examples of the light source for irradiating ultraviolet rays include lamps such as tungsten lamps, halogen lamps, xenon lamps, xenon flash lamps, mercury lamps, mercury xenon lamps, and carbon arc lamps, and various lasers (eg, semiconductor lasers, helium neon lasers, etc.). Examples thereof include an argon ion laser, a helium cadmium laser, a YAG (Yttrium Aluminum Garnet) laser), a light emitting diode, and a cathode wire tube.
The peak wavelength of ultraviolet rays emitted from a light source that irradiates ultraviolet rays is preferably 200 nm to 400 nm.

(Inert gas)
Examples of the inert gas used in this step include rare gases such as nitrogen gas, argon gas and neon gas, and carbon dioxide gas, and among them, nitrogen gas is preferable.

(Backup role)
The backup roll is not particularly limited, and a known backup roll can be used.
As the backup roll, for example, one having a hard chrome-plated surface can be preferably used.
The thickness of the plating is preferably 40 μm to 60 μm from the viewpoint of ensuring conductivity and strength.
The surface roughness of the backup roll is preferably 0.1 μm or less in terms of surface roughness Ra from the viewpoint of reducing the variation in the frictional force between the continuous film support and the backup roll.

The surface temperature of the backup roll may be determined according to the composition of the curable layer, the curing performance of the curable layer, the heat resistance of the continuous film support, etc., and is preferably 50 ° C to 250 ° C, preferably 60 ° C to 160 ° C. Is more preferable.
By setting the surface temperature of the backup roll to the above temperature, the curing speed of the curable layer can be increased, and the temperature of the continuous film support to be wound can be controlled.

It is preferable that the backup roll detects the surface temperature and the surface temperature of the backup roll is maintained by the temperature control means based on the temperature.
The temperature control means of the backup roll includes a heating means and a cooling means. As the heating means, induction heating, water heating, oil heating and the like are used, and as the cooling means, cooling with cooling water is used.

The diameter of the backup roll is preferably 100 mm to 1000 mm, more preferably 100 mm to 800 mm, and more preferably 200 mm to 700 mm from the viewpoints of easy wrapping of the continuous film support, easy irradiation of ultraviolet rays, and manufacturing cost of the backup roll. Is more preferable.

In the second step of the present disclosure, (1) at least a part while the joint portion passes through the active energy ray irradiation portion, and (2) a point where the continuous film support separates from the backup roll and 4 m downstream from this point in the transport direction. At least one of at least a part of the time during which the joint passes between the points and the above points, the inert gas is supplied at the second supply flow rate, and the first supply flow rate f1 and the second supply flow rate f2 The following equation 1 is satisfied.
f1> f2 ・ ・ ・ Equation 1

By controlling the supply flow rate of the inert gas into the active energy ray irradiation unit within the range satisfying the above formula 1, when only one side of the web is cooled by the inert gas supplied to the active energy ray irradiation unit. , It is possible to suppress the force in the out-of-plane direction caused by the temperature difference between the front and back of the web becoming too large.
When transporting a web having a joint portion in which films are joined and connected to each other, a temperature difference is particularly likely to occur while the joint portion is on a heated backup roll, that is, in the active energy ray irradiation portion. When it is satisfied, the effect of suppressing the temperature difference is large.
Also, while the specific section after leaving the backup roll, that is, the joint, is in the transport path between the separation point where the continuous film support separates from the backup roll and the point 4 m downstream from the separation point in the transport direction. Generally, waveform deformation (wrinkles) tends to disappear. Therefore, if the temperature of the section up to the point 4 m downstream in the transport direction can be adjusted so as not to drop too much, it is possible to effectively prevent the wrinkles from changing to the riding wrinkles.
That is, in the method for producing an optical film of the present disclosure, by satisfying Equation 1 in a certain section, the effect of suppressing the temperature difference generated becomes large, and it is possible to prevent the development of riding wrinkles.

At least a part of the time during which the joint passes through the active energy ray irradiation part, and at least while the joint passes between the point where the continuous film support separates from the backup roll and the point 4 m downstream from this point in the transport direction. The ratio (= f2 / f1 × 100) of the second supply flow rate f2 to the first supply flow rate f1 in at least one of the parts is preferably 50% or less.
When the ratio of the second supply flow rate f2 is 50% or less, the occurrence of wrinkles can be dramatically reduced.
Above all, the ratio (= f2 / f1 × 100) of the second supply flow rate f2 to the first supply flow rate f1 described above is more preferably 20% or less, further preferably 10% or less. It is particularly preferable that it is 0 (zero)% (that is, the second supply flow rate is zero).

The second supply flow rate f2 of the inert gas is not particularly limited as long as the relationship with the first supply flow rate f1 is satisfied as described above, but specific ranges include, for example. , 100 m ³ / h or less, ^{more preferably 20 m 3} / h or less, and even more preferably 0 m ³ / h.

If the supply flow rate of the inert gas is reduced too much, it takes time to reduce the oxygen concentration in the active energy ray irradiation section to a certain range even if the supply flow rate of the inert gas is returned to f1, and as a result, it is supported. It may lead to an increase in body loss. This point also applies when the timing of returning the supply flow rate of the inert gas after the joint is separated from the backup roll is too late. Therefore, it is preferable that the supply flow rate of the inert gas is controlled in a range in which the oxygen concentration can be easily maintained in a constant range.

In the second step, from the viewpoint of dramatically reducing the occurrence of wrinkles, at least a part of the time during which the joint passes through the active energy ray irradiation part, and from the point where the continuous film support separates from the backup roll and from this point. It is preferable to maintain the second supply flow rate f2 at least in both of at least a part of the time when the joint portion passes between the point and the point 4 m downstream in the transport direction.
That is, as described above, the temperature difference between the front and back of the web tends to be large while inside the active energy ray irradiation part, and it is desirable to prepare an environment in which wrinkles are unlikely to occur in a specific section after being separated from the backup roll. It is effective to reduce the supply flow rate of the inert gas when passing through the active energy ray irradiation unit and when passing from the separation point of the backup roll to 4 m downstream.
Specifically, while the joint portion passes through the active energy ray irradiation portion, it is continuous with at least a part of the distance from the separation point (for example, point Q in FIG. 1) where the joint portion is separated from the backup roll to 1 m upstream. While the joint passes between the separation point (for example, point Q in FIG. 1) where the film support separates from the backup roll and the point 4 m downstream in the transfer direction from the separation point (for example, point Q), the film support is conveyed from the separation point. It is preferable to maintain the second supply flow rate f2 at least a part of the distance to a point up to 2 m downstream (preferably up to 4 m downstream) in the direction.

In the second step, the supply flow rate of the inert gas is adjusted so as to satisfy Equation 1 before the joint portion of the conveyed continuous film support comes into contact with the backup roll (for example, before reaching the contact point P in FIG. 1). It is also preferable to adjust.
In the active energy ray irradiation section, the temperature difference between the front and back of the film due to the supplied inert gas is likely to occur, so before heating with the backup roll (for example, as shown in FIG. 1, the point in contact with the backup roll (contact point)). By adjusting the range to satisfy f1> f2 before reaching P), it becomes easier to suppress the occurrence of wrinkles.
Specifically, it is preferable to satisfy f1> f2 before the joint reaches a contact point (for example, point P in FIG. 1) in contact with the backup roll.

An example of the second step will be described with reference to FIG.
As shown in FIG. 1, the web (continuous film support) F on which the curable layer, which is a coating film, is formed has an active energy in which nitrogen gas, which is an example of an inert gas, is supplied at the first supply flow rate f1. In the reaction chamber 3 which is an example of the ray irradiation unit, irradiation of ultraviolet rays which is an example of active energy rays is performed. Specifically, the web F on which the curable layer is formed is wound around the backup roll 34 in the reaction chamber 3, and the light source 32 irradiates the curable layer, which is a coating film, with ultraviolet rays.
At this time, nitrogen gas is supplied from the nozzle 36a into the reaction chamber 3, but as described above, the joint portion of the web is separated from the backup roll 34 while passing through the reaction chamber 3. Nitrogen gas is supplied at the second supply flow rate f2 for at least one of the passages up to 4 m downstream of the separation point Q, and the first supply flow rate f1 and the second supply flow rate f2 have a specific relational expression. It is adjusted within the range that satisfies (Equation 1 above).
As a result, it is possible to effectively suppress the occurrence of web run-up wrinkles that are likely to occur when the curable layer is cured in an inert atmosphere.

FIG. 1 shows an example in which nitrogen gas is discharged from the nozzle 36a so that the nitrogen gas does not directly hit the web. However, in the method for producing an optical film of the present disclosure, the discharge direction of nitrogen gas is not particularly limited. As shown in the nozzle 36b of FIG. 2, the nitrogen gas can be discharged so that the nitrogen gas directly hits the web.

-Third process (preheating process)-
The method for producing an optical film of the present disclosure includes a third step (hereinafter, also referred to as "preheating step") of preheating a continuous film support coated with a curable layer before the second step. It is preferable to have.
By having the preheating step, the web having the curable layer is conveyed to the second step in a heated state and comes into contact with the backup roll, so that the side on which the curable layer is formed and the backup roll come into contact with each other. The temperature difference between the surface and the surface is less likely to occur, and the occurrence of wrinkles is suppressed more effectively.

In the preheating step, the method of heating the web on which the curable layer is formed is not particularly limited, and a contact heating method or a non-contact heating method may be used.
Examples of the contact heating method include a method in which a heated roll, belt, or the like is brought into contact with the web on which the curable layer is formed.
The non-contact heating method includes a method of blowing warm air to heat the web on which the curable layer is formed, a method of applying radiant heat using an infrared heater to heat the web, and a heating zone in which the atmosphere is heated. Examples thereof include a method of passing the inside through a web to heat the inside.
As one specific example of the preheating step, as shown in FIGS. 1 and 2, for example, the web F on which the curable layer is formed is brought into contact with the temperature control roll 4 which has been temperature-controlled to a desired temperature and heated. May be good. In order to improve the accuracy of temperature control of the web F on which the curable layer is formed, the web F on which the curable layer is formed may be wound around the temperature control roll 4 and conveyed.

In the preheating step, the heating temperature for the web on which the curable layer is formed is preferably close to the surface temperature of the backup roll in the second step. Here, the heating temperature refers to the temperature of the surface of the web on which the curable layer is formed.
That is, the heating temperature for the web on which the curable layer is formed is preferably 60 ° C. to 250 ° C., more preferably 80 ° C. to 250 ° C., and even more preferably 80 ° C. to 150 ° C.
The heating temperature of the web heated in the preheating step is the temperature at which the surface of the web is measured using a non-contact thermometer or a non-contact temperature sensor.

Further, the heating temperature for the web-curable layer is formed as a T ₃ ° C., if the surface temperature of the heated back-up roll was set to T ₂ ° C., T ₃ is, T 2 _-20 ° C. or more T _{2 +} 20 ° C. or less Is preferable.
That is, the temperature T ₃ is preferably within ± 20 ° C. with respect to the temperature T _2.
Further, considering that the temperature drops during transportation to the active energy ray irradiation portion after the web on which the curable layer is formed is heated, it is preferable to satisfy the relationship of _{temperature T 3} > temperature T _2.

As described above, a curable layer, which is an optical functional layer, is formed on a continuous film support (web) having a joint portion in which the films are bonded to each other.
Examples of the optical functional layer include an optically anisotropic layer in a retardation film, an antireflection layer in an antireflection film, an antiglare layer in an antiglare film, and a lenticular lens layer in a lenticular sheet.
That is, according to the method for producing an optical film of the present disclosure, a retardation film having an optically anisotropic layer, an antireflection film having an antireflection layer, an antiglare film having an antiglare layer, and a lenticular sheet having a lenticular lens layer. Etc. can be obtained.

~ Manufacturing method of retardation film ~
Hereinafter, a method for producing a retardation film will be described as an example of the method for producing the optical film of the present disclosure.
The retardation film is an optical difference containing an alignment layer having an orientation regulating force for arranging the liquid crystal compounds of the liquid crystal layer in a certain direction on a continuous film support (web) and an oriented and immobilized liquid crystal compound. The anisotropic layer (hereinafter, also referred to as “liquid crystal layer”) is provided in this order.

(Orientation layer and its formation method)
The alignment layer in the retardation film is not particularly limited as long as it has an orientation regulating force for arranging the liquid crystal compounds in the liquid crystal layer in a certain direction.
Examples of the alignment layer in the retardation film include an alignment layer to which an orientation regulating force is applied to a liquid crystal compound by a rubbing method, specifically, a layer of an organic compound (preferably a polymer) subjected to a rubbing treatment. it can.
Here, the rubbing method is a method of restricting the orientation of a liquid crystal compound on a coating film by rubbing the surface of a coating film containing a material for forming an alignment layer (hereinafter, also referred to as a coating film for an alignment layer) with a rubbing cloth in a certain direction. It is a method of giving power. Further, a process of rubbing the surface of the coating film for an alignment layer with a rubbing cloth in a certain direction is called a rubbing process.

-Material for forming an orientation layer-
The material for forming the alignment layer used for forming the alignment layer preferably contains the following organic compound and a solvent for dissolving the organic compound. Examples of the organic compound include polymethylmethacrylate and acrylic acid / methacrylic acid. Polymers, styrene / maleinimide copolymers, polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyl toluene copolymers, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefins, polyesters, polyimides, Examples thereof include polymers such as vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene, and polycarbonate, and compounds such as silane coupling agents.
Examples of preferred polymers include polyimides, polystyrenes, polymers of styrene derivatives, polyvinyl alcohols, and alkyl-modified polyvinyl alcohols having an alkyl group (preferably an alkyl group having 6 or more carbon atoms).
As the polymer used as the material for forming the alignment layer, alkyl-modified polyvinyl alcohol is particularly preferable, and the alkyl group having 6 to 14 carbon atoms is -S-,-(CH ₃ ) C (CN)-, or-(. C ₂ H ₅ ) Alkyl-modified polymer alcohol bonded to the terminal or side chain of polyvinyl alcohol via N-CS-S- is preferable.

The same methods as the coating method and the drying method in the curable layer forming step described above can be used for forming the coating film for the alignment layer, and the preferred embodiment is also the same.
The film thickness of the coating film for the alignment layer is preferably 0.1 μm to 5 μm, more preferably 0.2 μm to 1 μm.

-Giving orientation control force-
In the case of the rubbing method, the surface of the coating film for the alignment layer formed on the continuous film support may be rubbed with a rubbing cloth in a certain direction.
The rubbing treatment is not particularly limited, and a known method can be applied. Specifically, as a rubbing treatment, a method of rubbing the surface of the coating film for an alignment layer with a rubbing cloth such as paper, gauze, felt, rubber, nylon, or polyester fiber in a certain direction can be mentioned. Generally, a rubbing treatment such as rubbing the surface of the coating film for an alignment layer several times is performed using a rubbing cloth on which fibers of a uniform length and thickness are evenly transplanted.
As described above, the alignment layer having the orientation regulating force for the liquid crystal compound is formed.

(Liquid crystal layer and its formation method)
It is preferable that a curable layer of the liquid crystal layer forming material (hereinafter, also referred to as “curable layer for liquid crystal layer”) is formed on the oriented layer formed as described above. After that, the liquid crystal compound is oriented and fixed in the curable layer for the liquid crystal layer, and a liquid crystal layer (that is, an optically anisotropic layer) is obtained.

-Material for forming a liquid crystal layer-
The liquid crystal layer forming material contains a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, and further known other components such as a polymerizable compound, a crosslinkable compound, a chiral agent, an orientation control agent, a polymerization initiator, and an orientation auxiliary. May be contained.

-Stick-shaped liquid crystal compounds Examples of rod-shaped liquid crystal compounds include azomethine-based compounds, azoxy-based compounds, cyanobiphenyl-based compounds, cyanophenyl ester-based compounds, benzoic acid ester-based compounds, cyclohexanecarboxylic acid phenyl ester-based compounds, cyanophenylcyclohexane-based compounds, and cyano. Substituted phenylpyrimidine-based compounds, alkoxy-substituted phenylpyrimidine-based compounds, phenyldioxane-based compounds, trans and alkenylcyclohexylbenzonitrile-based compounds are preferably used.
As the rod-shaped liquid crystal compound, not only low molecular weight liquid crystal molecules as described above but also high molecular weight liquid crystal molecules can be used.

It is more preferable that the orientation of the rod-shaped liquid crystal compound is fixed by polymerization. From this point of view, it is preferable to use a rod-shaped liquid crystal compound having a polymerizable group.
Examples of the rod-shaped liquid crystal compound having a polymerizable group include Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. Nos. 4,683,327, 562,648, 5770107, International Publication 95/22586, 1993. 95/24455, 97/00600, 98/23580, 98/52905, Japanese Patent Application Laid-Open No. 1-272551, 6-16616, 7-110469, 11 Examples thereof include the compounds described in JP-A-80081 and JP-A-2001-328973.
Further, as the rod-shaped liquid crystal compound, for example, those described in JP-A No. 11-513019, JP-A-2007-279688, etc. can be preferably used.

-Disc-shaped liquid crystal compound As the disk-shaped liquid crystal compound, for example, those described in JP-A-2007-108732, JP-A-2010-2404038 and the like can be preferably used.

The curable layer for a liquid crystal layer can be formed in the same manner as in the coating and drying in the curable layer forming step described above, and the preferred embodiment is also the same. When the method for producing an optical film of the present disclosure is a method for producing a retardation film, the formation of a curable layer for a liquid crystal layer corresponds to the above-described curable layer forming step.

-Orientation of liquid crystal compounds-
Before fixing the orientation of the liquid crystal compound in the curable layer for the liquid crystal layer, it is preferable to perform the orientation treatment of the liquid crystal compound in the curable layer for the liquid crystal layer.
The orientation treatment can be performed by drying at room temperature or the like or by heating.
In the case of a liquid crystal compound having thermotropic properties, the liquid crystal formed by the orientation treatment can generally be transferred by a change in temperature or pressure. Further, in the case of a liquid crystal compound having a lyotropic property, it can be transferred by a composition ratio such as the amount of solvent.

When the rod-shaped liquid crystal compound expresses the smectic phase, the temperature range in which the nematic phase is expressed is usually higher than the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase. Therefore, the rod-shaped liquid crystal compound is heated to the temperature range in which the rod-shaped liquid crystal compound expresses the nematic phase, and then the heating temperature is lowered to the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase, whereby the rod-shaped liquid crystal compound is brought into the nematic phase. Can be transferred to the smectic phase. By forming the smectic phase in this way, a liquid crystal in which the liquid crystal compounds are oriented with high order can be obtained.

In the temperature range in which the rod-shaped liquid crystal compound expresses the nematic phase, it is necessary to heat the rod-shaped liquid crystal compound for a certain period of time until it forms a monodomain. The heating time is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 3 minutes, and most preferably 10 seconds to 2 minutes.
In the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase, it is necessary to heat for a certain period of time until the rod-shaped liquid crystal compound expresses the smectic phase. The heating time is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 3 minutes, and most preferably 10 seconds to 2 minutes.

The orientation of the liquid crystal compound may be performed by drying when forming the curable layer for the liquid crystal layer. That is, in the drying when forming the curable layer for the liquid crystal layer, both the drying of the material for forming the liquid crystal layer coated on the alignment layer and the orientation of the liquid crystal compound may be performed.
Further, the orientation of the liquid crystal compound may be performed separately from the drying when forming the curable layer for the liquid crystal layer.

-Fixing the orientation of liquid crystal compounds-
The orientation of the liquid crystal compound in the curable layer for the liquid crystal layer is preferably fixed by curing the curable layer for the liquid crystal layer by thermal polymerization or polymerization with active energy rays. When the method for producing an optical film of the present disclosure is a method for producing a retardation film, fixing the orientation of the liquid crystal compound using active energy rays corresponds to the second step described above.
When a polymerizable liquid crystal compound is used, if the irradiation amount of the active energy ray is small, the unpolymerized liquid crystal compound remains, which causes temperature change of optical characteristics, deterioration with time, and the like. Therefore, it is preferable to determine the irradiation conditions so that the proportion of the remaining unpolymerized liquid crystal compound is 5% or less.

Wherein the irradiation conditions of the formulation of the liquid crystal layer forming material, and depending on the thickness of the liquid crystal layer curable layer, active energy ray irradiation amount ^is preferably ^{50mJ / cm 2 ~1000mJ / cm 2} , 100mJ / Cm ^{2 to} 500 mJ / cm ² is more preferable.

As the light source used for irradiating the active energy rays, the light source in the second step described above can be applied, and the preferred embodiment is also the same.

In addition, for details of the liquid crystal layer, the description of JP-A-2008-225281 and JP-A-2008-026730 can be referred to.

In the retardation film obtained as described above, wrinkles generated when the orientation of the liquid crystal compound is fixed are reduced. Therefore, it can be a retardation film having excellent in-plane uniformity of optical performance.

In the above, an example in which the method for producing an optical film of the present disclosure is applied when obtaining a liquid crystal layer of a retardation film has been described, but in addition to this example, the antireflection layer and antiglare of the antireflection film described above have been described. It can also be applied to obtain an antiglare layer of a film, a lenticular lens layer of a lenticular sheet, and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

[Examples 1 to 9 and Comparative Example 1]
(Web preparation)
One end of another TAC film of the same type was abutted against one end of a cellulose triacetate film (TAC film; TD40UL, FUJIFILM Corporation) having a width of 1340 mm and a thickness of 40 μm on the same plane and positioned so that the longitudinal direction was straight. Then, the two TAC films that were butted against each other were attached to both sides with an adhesive tape over the entire width and connected. In this way, a web having a joint was produced.
As the adhesive tape, a polyethylene terephthalate (PET) having a thickness of 100 μm was used, to which a double-sided tape having a thickness of 100 μm was attached as an adhesive layer on one surface.
The joint portion that is the connecting portion of the two TAC films has a laminated structure of PET / double-sided tape / TAC film / double-sided tape / PET, and the total thickness is 440 μm.

(Formation of coating film for alignment layer and rubbing treatment)
A 2% by mass aqueous solution of alkyl-modified polyvinyl alcohol (Poval MP-203, Kuraray) was applied to one side of a continuous film support made of a cellulose triacetate film TD40UL (Fujifilm Corporation) having a length of 1000 m, a width of 1340 mm and a thickness of 40 μm. ^{After applying 25 ml per 1 m 2 of the} continuous film support, the film was dried at 60 ° C. for 60 seconds to form a coating film for an alignment layer having a dry film thickness of 0.5 μm. Then, while transporting the continuous film support on which the coating film for the alignment layer is formed at a transport speed of 30 m / min, the surface of the coating film for the alignment layer is subjected to a rubbing treatment to form an alignment layer having a thickness of 0.5 μm. did.

(Formation of curable layer for liquid crystal layer)
Subsequently, an apparatus having the same configuration as in FIG. 1 was prepared, and a liquid crystal layer forming material prepared by mixing the following compositions was applied onto the alignment layer using a bar coater. The continuous film support coated with the liquid crystal layer forming material was heated and dried at a film surface temperature of 150 ° C. for 60 seconds to form a curable layer for a liquid crystal layer having a dry film thickness of 2 μm (curable layer forming step). ). In addition, 10 m before and after the joint portion, the bar coater was separated from the coating point, and coating was not performed.
The total thickness of the laminate in which the curable layer for the liquid crystal layer is formed on the web is 42.5 μm.

-Composition of material for forming liquid crystal layer-
Reverse wavelength dispersion liquid crystal compound R-2 100 parts by mass Photopolymerization initiator 3.0 parts by mass (Irgacure 819, BASF)
Fluorine-containing compound A 0.8 parts by mass Crosslinkable polymer O-2 (glass transition temperature Tg: 10 ° C.) 0.3 parts by mass Chloroform 588 parts by mass

(Preheating)
Next, a continuous film support (web) F having a curable layer for a liquid crystal layer was conveyed (line speed: 20 m / min; first step) to a heating roll 4 having a diameter of 600 mm whose surface temperature was adjusted to 120 ° C. A web F having a curable layer for a liquid crystal layer was brought into contact with the web F. In this way, the web F having the curable layer for the liquid crystal layer was heated (third step).

(UV curing)
Subsequently, in the reaction chamber 3, the backup roll (diameter: 500 mm, material: stainless steel) is wound around the backup roll (diameter: 500 mm, material: stainless steel) at a lap angle of 90 ° C., and the air-cooled metal halide lamp (eye) is applied to the curable layer for the liquid crystal layer in the wound area. (Graphics) was used to irradiate ultraviolet rays (active energy rays) (second step). The irradiation amount of ultraviolet rays here was 300 mJ / cm ² .

Nitrogen gas at room temperature (25 ° C.) is supplied to ^{the reaction chamber at a supply flow rate of 200 m 3} / h (first supply flow rate f1) from a slit-shaped outlet of 2 mm × 2000 mm, and the width of the web. Nitrogen gas was applied over the entire direction. The slit-shaped outlet was installed so that the short (2 mm) side was along the transport direction of the continuous film support and the long (2000 mm) side was along the width direction of the continuous film support. Further, the slit-shaped outlet was installed at a position 5 mm away from the coating film surface at the contact point between the continuous film support and the backup roll.

Then, when the curable layer for the liquid crystal layer is cured by irradiating with ultraviolet rays as described above, when the joint portion passes through the inside of the reaction chamber 3, and when the continuous film support is separated from the separation point Q away from the backup roll. While passing the distance from the point Q to the point 4 m downstream in the transport direction, the supply flow rate of ^{nitrogen gas supplied at the supply flow rate of 200 m 3} / h (first supply flow rate f1) is shown in Table 1 below. As shown in the above, the supply was changed to a second supply flow rate f2, which is smaller than the supply flow rate f1. The length of the continuous film support wound around the surface of the backup roll (the surface corresponding to 1/4 in the circumferential direction) is 400 mm.

As described above, a retardation film having a liquid crystal layer in which the orientation of the liquid crystal compound is fixed was produced.

[Evaluation]
With respect to the retardation films produced in Examples and Comparative Examples, the frequency of run-up wrinkles was measured by the following method. The results are shown in Table 1.
Specifically, in the region from 0 m to 1 mm from the end (end on the winding end side) of the produced retardation film, the state of occurrence of riding wrinkles is visually observed over the entire width direction, and the presence or absence of riding wrinkles is observed. It was confirmed. The wrinkle occurrence rate was calculated from the following formula, where n was the number of times that wrinkles were generated during the N times of passing through the joint, and N = 10.
Wrinkle occurrence rate (%) = n / N x 100

As is clear from Table 1, the retardation film of the example has a significantly reduced frequency of run-up wrinkles as compared with the retardation film of the comparative example.
In particular, during the time when the joint portion passes through the active energy ray irradiation portion and between the point where the continuous film support separates from the backup roll and the point where the joint portion passes 4 m downstream from this point in the transport direction, initially. In Examples 1 to 4 in which the second supply flow rate f2, which is smaller than the first supply flow rate, which is the flow rate, was maintained, the effect on suppressing the occurrence of run-up wrinkles was more remarkable.

1 ... Coating device (coating means)
2 ... Drying device (drying means)
3 ... Reaction chamber (active energy ray irradiation section)
4 ... Heating roll 32 ... Light source 34 ... Backup roll 36a, 36b ... Nozzle F ... Web (continuous film support)
P: Contact point where the continuous film support and the backup roll come into contact Q: Separation point where the continuous film support (particularly the joint) separates from the backup roll

Claims (9)

The first step of transporting a continuous film support having a joint portion in which films are bonded to each other and having a curable layer coated therein.
In the active energy ray irradiation unit where the inert gas is supplied at the first supply flow rate, the active energy ray is irradiated to the curable layer in the winding region of the continuous film support wound on the heated backup roll. Second step and
Have,
In the second step, at least a part of the time during which the joint portion passes through the active energy ray irradiation portion, and between a point where the continuous film support separates from the backup roll and a point 4 m downstream from the point in the transport direction. At least one of at least a part of the time during which the joint passes supplies the inert gas at the second supply flow rate, and the ratio of the second supply flow rate f2 to the first supply flow rate f1 is 20%. The following is a method for manufacturing an optical film. The method for producing an optical film according to claim 1, wherein the surface temperature of the backup roll is 60 ° C. or higher and 160 ° C. or lower. It said second step further, before the junction of the transported continuous film support comes into contact with the backup roll, to adjust the supply flow rate of the inert gas in the range satisfying the formula 1, claim 1 or The method for producing an optical film according to claim 2.
f1> f2 formula 1 In the second step, at least a part of the time during which the joint portion passes through the active energy ray irradiation portion, and between a point where the continuous film support separates from the backup roll and a point 4 m downstream from the point in the transport direction. The method for producing an optical film according to any one of claims 1 to 3 , wherein the second supply flow rate f2 is maintained for at least a part of the time during which the joint portion passes through. The method for producing an optical film according to any one of claims 1 to 4 , further comprising a third step of preheating the continuous film support coated with the curable layer before the second step. The method for producing an optical film according to any one of claims 1 to 5 , wherein the width length of the continuous film support is 200 mm or more and 2000 mm or less. The method for producing an optical film according to any one of claims 1 to 6 , wherein the thickness of the continuous film support is 3 μm or more and 100 μm or less. The method for producing an optical film according to any one of claims 1 to 7 , wherein the first supply flow rate f1 of the inert gas is 5 m ³ / h or more and 300 m ³ / h or less. The method for producing an optical film according to any one of claims 1 to 8 , wherein the total thickness of the laminate in which the curable layer is formed on the continuous film support is 3.1 μm or more and 115 μm or less.

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