JP2020160240A - Method and device for manufacturing optical film - Google Patents

Abstract

To provide a method of manufacturing an optical film, which allows for suppressing thickness irregularity of a coating layer formed on a base material and preventing generation of spots and stripes on the optical film.SOLUTION: A method of manufacturing an optical film is provided, comprising steps of: coating a surface of a base material with a coating liquid using a die coater while conveying the base material along a peripheral surface of a backup roller; and forming a gas layer with a thickness in a range of 1 to 20 μm, inclusive, between the peripheral surface of the backup roller and the base material at a position where the base material is coated with the coating liquid.SELECTED DRAWING: Figure 1

Description

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

As a method of continuously applying a coating liquid to the surface of a long base material to form a coating layer, a slit of the die coater is provided while the long base material is wound around a backup roll and continuously conveyed. A method is known in which a coating liquid is discharged from a bead (liquid pool) at the tip of a slit, and the bead is brought into contact with the surface of a base material to apply the coating liquid (Patent Documents 1 to 5).

Japanese Unexamined Patent Publication No. 2003-010765 Japanese Unexamined Patent Publication No. 2009-241019 Japanese Unexamined Patent Publication No. 2013-169948 JP-A-2007-75797 Japanese Unexamined Patent Publication No. 2005-144414

In recent years, further thinning of mobile electronic devices has been required, and image display devices mounted on the mobile electronic devices have also been further thinned. In order to reduce the thickness of optical films such as polarizing plates and retardation plates incorporated in image display devices, when an optical film is produced by forming a coating layer on a base material, the thickness of the coating layer is preferably thin.

However, as the coating layer becomes thinner, the thickness of the coating layer becomes uneven, and the surface condition of the optical film may become poor. For example, spots (spot unevenness) may occur on the optical film, or thick streaks (horizontal steps) may periodically occur in the width direction of the optical film.
If these surface defects are present in the optical film, they may cause display defects when the optical film is incorporated into the image display device. Therefore, the defective portions are usually removed from the optical film. The higher the occurrence of surface defects, the lower the yield of the optical film and the higher the manufacturing cost. Therefore, it is preferable that the occurrence of thickness unevenness in the coating layer is small.

Therefore, a method for producing an optical film capable of suppressing uneven thickness of the coating layer formed on the base material and suppressing the occurrence of spots and streaks on the optical film; and uneven thickness of the coating layer formed on the base material. There is a demand for an optical film manufacturing apparatus that can suppress the occurrence of spots and streaks on the optical film.

The present inventors have found that surface defects such as spots and streaks on an optical film become more prominent as the substrate adheres to the backup roll. Based on this finding, the present inventors have diligently studied to solve the above-mentioned problems. As a result, they have found that the problem can be solved by forming a gas layer having a thickness of 1 μm or more and 20 μm or less between the peripheral surface of the backup roll and the base material at the position of the base material to which the coating liquid is applied. The present invention has been completed.
That is, the present invention provides the following.

[1] A method for producing an optical film, which comprises a step of applying a coating liquid to the surface of the base material with a die coater while transporting the base material along the peripheral surface of the backup roll.
A method for producing an optical film, wherein a gas layer having a thickness of 1 μm or more and 20 μm or less is formed between a peripheral surface of the backup roll and the base material at a position of the base material to which the coating liquid is applied.
[2] The method for producing an optical film according to [1], wherein the gas layer is formed by supplying a gas between the peripheral surface of the backup roll and the base material.
[3] The method for producing an optical film according to [2], wherein the gas is supplied by blowing the gas between the peripheral surface of the backup roll on which the base material starts to run and the base material.
[4] The method for producing an optical film according to [2], wherein the gas is supplied by ejecting the gas from the peripheral surface of the backup roll.
[5] Any of [1] to [4], which restricts the flow of gas from between the peripheral surface of the backup roll where the base material starts to separate and the base material toward the downstream in the transport direction of the base material. The method for producing an optical film according to item 1.
[6] A roll pair composed of a first auxiliary roll and a second auxiliary roll is provided between the peripheral surface of the backup roll at which the base material starts to separate and the base material, and the peripheral surface of the backup roll is provided by the roll pair. And the base material,
The first auxiliary roll has a rotation axis parallel to the rotation axis of the backup roll, and is in contact with the peripheral surface of the backup roll.
The second auxiliary roll has a rotation axis that is parallel to the rotation axis of the backup roll and is located at a position farther from the rotation axis of the backup roll than the rotation axis of the first auxiliary roll. In contact with the peripheral surface of the auxiliary roll and the base material,
The method for producing an optical film according to [5], wherein the hardness of the peripheral surface of the first auxiliary roll is lower than the hardness of the peripheral surface of the second auxiliary roll.
[7] The method for producing an optical film according to any one of [1] to [6], wherein at least one convex portion is provided on the peripheral surface of the backup roll.
[8] The method for producing an optical film according to [7], wherein the at least one convex portion has a height of 1 μm or more and 20 μm or less.
[9] The method for producing an optical film according to any one of [1] to [8], wherein the backup roll is freely rotatable.
[10] The method for producing an optical film according to any one of [1] to [9], wherein the base material has a coefficient of static friction with iron of 0.7 or more.
[11] A backup roll that conveys the base material along the peripheral surface, and
A die coater that applies a coating solution to the surface of the base material,
A gas supply device that supplies gas between the peripheral surface of the backup roll and the base material,
It is supplied from the gas supply device so that the thickness of the gas layer between the peripheral surface of the backup roll and the base material at the position of the base material to which the coating liquid is applied is 1 μm or more and 20 μm or less. An adjusting device that adjusts the amount of gas,
Optical film manufacturing equipment, including.
[12] Further including a roll pair consisting of a first auxiliary roll and a second auxiliary roll,
The first auxiliary roll has a rotation axis parallel to the rotation axis of the backup roll, and is in contact with the peripheral surface of the backup roll.
The second auxiliary roll has a rotation axis that is parallel to the rotation axis of the backup roll and is located at a position farther from the rotation axis of the backup roll than the rotation axis of the first auxiliary roll. It is provided so as to be in contact with the peripheral surface of the auxiliary roll and the base material to be conveyed.
The optical film manufacturing apparatus according to [11], wherein the hardness of the peripheral surface of the first auxiliary roll is lower than the hardness of the peripheral surface of the second auxiliary roll.
[13] The optical film manufacturing apparatus according to [11] or [12], wherein at least one convex portion is provided on the peripheral surface of the backup roll.
[14] The optical film manufacturing apparatus according to any one of [11] to [13], wherein the backup roll is freely rotatable.

According to the present invention, a method for producing an optical film capable of suppressing uneven thickness of a coating layer formed on a base material and suppressing the occurrence of spots and streaks on the optical film; and a coating layer formed on the base material. It is possible to provide an optical film manufacturing apparatus capable of suppressing the occurrence of spots and streaks of the optical film by suppressing the thickness unevenness of the optical film.

FIG. 1 is a schematic view showing an example of an optical film manufacturing apparatus capable of carrying out the optical film manufacturing method according to the first embodiment. FIG. 2 is a schematic view showing an example of an optical film manufacturing apparatus capable of carrying out the optical film manufacturing method of the second embodiment. FIG. 3 is a schematic view showing an example of an optical film manufacturing apparatus capable of carrying out the optical film manufacturing method according to the third embodiment.

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.

In the following description, the same elements may be designated by the same reference numerals and the description thereof may be omitted.

In the following description, the "long" film means a film having a length of 5 times or more with respect to the width, preferably having a length of 10 times or more, and specifically a roll. A film that has a length that allows it to be rolled up and stored or transported. The upper limit of the length of the film is not particularly limited, and may be, for example, 100,000 times or less the width.

In the following description, the directions of the elements are "parallel" and "vertical", unless otherwise specified, within a range that does not impair the effect of the present invention, for example, within a range of ± 3 °, ± 2 °, or ± 1 °. May include the error of.

In a long film, the width direction usually means a direction perpendicular to the transport direction at the time of manufacturing the long film.

[1. Optical film manufacturing method]
A method for producing an optical film according to an embodiment of the present invention will be described below with reference to the drawings. The method for producing an optical film according to the present embodiment includes a step of applying a coating liquid to the surface of the base material with a die coater while transporting the base material along the peripheral surface of the backup roll.
The method for producing an optical film according to the present embodiment can be preferably applied to a method for producing an optical film using a conventional so-called extrusion type coating method.

[1.1. Base material]
The substrate is usually a long, flexible film. Examples of the material of the base material are not particularly limited, and examples thereof include resin and metal, and resin is preferable. The resin usually contains a polymer. Examples of polymers contained in the resin include polyolefins (eg, polyethylene, polypropylene), alicyclic structure-containing polymers, polyesters (eg, polyethylene terephthalate (PET)), cellulose-based polymers (eg, triacetyl cellulose). , And acrylic polymers (eg, polymethylmethacrylate).

The alicyclic structure-containing polymer is a polymer containing an alicyclic structure in a repeating unit. Examples of the alicyclic structure-containing polymer include a polymer obtained by a polymerization reaction using a cyclic olefin as a monomer or a hydride thereof. More specific examples include a ring-opening polymer of a monomer having a norbornene structure and a hydride thereof.

The base material preferably has a coefficient of static friction with the iron plate of 0.7 or more. The present inventors have found that a substrate having a large coefficient of static friction with an iron plate tends to have a poor surface shape of an optical film when a conventional extrusion type coating method is used. In the manufacturing method of the present embodiment, even when a base material having a large coefficient of static friction with the iron plate and 0.7 or more is used, uneven thickness of the coating layer is suppressed and spots and streaks of the optical film are generated. Can be suppressed.

The base material has a coefficient of static friction with the iron plate of more preferably 0.8 or more, further preferably 1.0 or more, preferably 1.5 or less, and more preferably 1.4 or less. More preferably, it is 1.3 or less.

As the coefficient of static friction between the base material and the iron plate, a steel plate having a hard chrome plating on the surface (plating thickness 100 μm) and a maximum surface roughness Ry = 0.6 μm (JIS B 0601-1994) was used. It can be measured using a friction measuring instrument (eg, "FRICTION TESTER TR-2" manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the conditions of a speed of 20 mm / min, a measuring distance of 30 mm, a load range of 10 N, and a thread mass of 200 g.
The maximum surface roughness Ry can be measured according to JIS B 0601-1994. As a measuring device, a surface roughness measuring machine (eg, small surface roughness measuring machine "Surftest SJ-310" (manufactured by Mitutoyo Co., Ltd.) is used, and the evaluation length is 4.0 mm (cutoff value λc 0.8 mm ×). 5), and it can be measured by tracing the surface with a diamond probe.

The thickness of the base material is not particularly limited, and a base material having an arbitrary thickness can be used. The thickness of the base material can be, for example, 10 μm or more and 100 μm or less.
The width of the base material is not particularly limited, and a base material having an arbitrary width can be used. The width of the base material can be, for example, 100 mm or more and 3000 mm or less.

[1.2. Coating liquid]
The coating liquid applied to the surface of the base material contains any component. For example, the coating liquid may contain functional materials such as polymerizable liquid crystal compounds, polymerization initiators, chiral agents, monomers, antioxidants, and surfactants. Further, the coating liquid may contain a solvent such as an organic solvent and water. The coating liquid may be a dispersion liquid in which a functional material is dispersed in a dispersion medium, or may be a colloidal liquid. As the coating liquid, it is preferable that the viscosity measured by an E-type viscometer cone rotor at 23 ° C. and 100 rpm is in the range of 0.5 to 70 mPa · s.

[1.3. First Embodiment]
The manufacturing method according to the first embodiment of the present invention will be described in detail below with reference to the drawings.
FIG. 1 is a schematic view showing an example of an optical film manufacturing apparatus capable of carrying out the optical film manufacturing method according to the first embodiment.
The optical film manufacturing apparatus 100 includes a backup roll 110, a die coater 120, a gas supply apparatus 130, an adjusting apparatus 131, and a roll pair 140.

The backup roll 110 is a substantially cylindrical member, and is driven by a drive device (not shown) so as to rotate in the direction D1 (direction in which the base material 150 is conveyed) about the rotation shaft 110R.
In the present embodiment, the backup roll 110 is driven so as to rotate in the direction D1 about the rotation shaft 110R, but in another embodiment, the backup roll 110 is not driven and is freely driven around the rotation shaft 110R. It may be rotatably attached to the manufacturing apparatus 100, and in yet another embodiment, the backup roll 110 may be driven so as to rotate about the rotation shaft 110R in the direction opposite to the direction D1. Good.

The die coater 120 is connected to an extruder 121 that extrudes the coating liquid 160 by a pipe line 122. The die coater 120 includes a lip 123 facing the backup roll 110, discharges the coating liquid 160 from the slit 124 formed at the tip of the lip 123, and is conveyed to the surface of the base material 150 at the position P150 of the base material 150. The coating liquid 160 is continuously applied. As a result, the coating layer 161 made of the coating liquid 160 is formed on the surface of the base material 150.

The size of the die coater 120 is not particularly limited, and may be, for example, a size corresponding to the backup roll 110. The shape and size of the manifold portion of the die coater 120 are not particularly limited, and may be any shape and size.
The material forming the lip 123 is not particularly limited, and any material (eg, stainless steel material) can be used. The size of the slit 124 is not particularly limited and can be appropriately adjusted depending on, for example, the viscosity of the coating liquid 160, the desired thickness of the coating layer 161 and the like, and can be, for example, in the range of 0.05 mm or more and 2 mm or less.

The manufacturing apparatus 100 may include a die coater moving device that moves the die coater 120 to adjust the distance between the tip of the lip 123 of the die coater 120 and the backup roll 110.
Further, the manufacturing apparatus 100 may include a filtration apparatus for removing foreign matters and the like in the coating liquid 160.
Further, the manufacturing apparatus 100 may include a decompression device for applying the coating liquid 160 by the die coater 120 under reduced pressure.

The gas supply device 130 is arranged in the vicinity of the backup roll 110 so as to blow gas between the peripheral surface S1 of the backup roll 110 and the base material 150 to be conveyed.
The peripheral surface S1 is the peripheral surface of the backup roll 110 in a range where the base material 150 to be conveyed starts to follow. The fact that the base material 150 is along the backup roll 110 means that the base material 150, which is conveyed in a substantially planar shape, preferably in a planar shape, has a curved surface shape and is conveyed on the upper peripheral surface of the backup roll 110. .. Here, the upward direction of the backup roll 110 means the radial outward direction of the backup roll 110.

As the gas supply device 130, for example, a blower, an air compressor, or the like can be used.
An adjusting device 131 for adjusting the amount of gas to be blown between the peripheral surface S1 and the base material 150 is connected to the gas supply device 130. The adjusting device 131 includes, for example, a gas flow rate adjusting valve, and adjusts the amount of gas blown from the gas supply device 130 by manually or automatically adjusting the opening degree of the gas flow rate adjusting valve.

Examples of the gas supplied by the gas supply device 130 are not particularly limited, and examples thereof include air and an inert gas (eg, nitrogen gas). The humidity of the gas is not particularly limited, and the gas may be dried. The temperature of the gas is not particularly limited, and the gas may be a gas having a room temperature, a gas having a temperature higher than the room temperature, or a gas having a temperature lower than the room temperature.

The roll pair 140 is provided between the peripheral surface S2 of the backup roll 110 and the base material 150. The peripheral surface S2 is the peripheral surface of the backup roll 110 in a range where the base material 150 starts to separate. The fact that the base material 150 starts to separate from the backup roll 110 means that the base material 150 that has been conveyed in a curved shape on the upper peripheral surface of the backup roll 110 starts to be conveyed in a substantially planar shape, preferably in a planar shape. To do.

The roll pair 140 is composed of a first auxiliary roll 141 and a second auxiliary roll 142. The rotation shaft 141R of the first auxiliary roll 141 is parallel to the rotation shaft 110R of the backup roll 110. The rotation shaft 142R of the second auxiliary roll 142 is parallel to the rotation shaft 110R of the backup roll 110. Therefore, the rotating shaft 141R of the first auxiliary roll 141 and the rotating shaft 142R of the second auxiliary roll 142 are parallel to each other.

The first auxiliary roll 141 is in contact with a part of the peripheral surface 110S of the backup roll 110. The second auxiliary roll 142 is in contact with a part of the peripheral surface 141S of the first auxiliary roll 141. The rotation shaft 142R of the second auxiliary roll 142 is located at a position farther from the rotation shaft 110R of the backup roll 110 than the rotation shaft 141R of the first auxiliary roll 141. Therefore, the second auxiliary roll 142 comes into contact with one surface of the base material 150 conveyed along the peripheral surface 110S of the backup roll 110.

When the roll pair 140 has such a configuration, the roll pair 140 closes the space between the peripheral surface S2 of the backup roll 110 and the base material 150. As a result, the circumference of the backup roll 110 that restricts the flow of gas from between the peripheral surface S2 of the backup roll 110 and the base material 150 toward the downstream in the transport direction of the base material 150 and faces the die coater 120 via the base material 150. A gas layer 170 is formed between the surface S3 and the base material 150.

The hardness of the first auxiliary roll 141 on the peripheral surface 141S is lower than the hardness of the second auxiliary roll 142 on the peripheral surface 142S. Hardness can be measured according to, for example, JIS K 6253-3.
For example, the peripheral surface 141S of the first auxiliary roll 141 may be formed of rubber, and the peripheral surface 142S of the second auxiliary roll 142 may be formed of metal (eg, aluminum material, stainless steel material).

In the manufacturing method according to the first embodiment of the present invention, the peripheral surface S3 of the backup roll 110 and the base material 150 facing the die coater 120 via the base material 150 at the position P150 of the base material 150 to which the coating liquid 160 is applied. A gas layer 170 is formed between the two. The thickness of the gas layer 170 is usually 1 μm or more, preferably 1.5 μm or more, more preferably 2 μm or more, and usually 20 μm or less, preferably 15 μm or less, more preferably 13 μm or less.
By setting the thickness of the gas layer 170 to be equal to or greater than the lower limit, the influence of runout and speed unevenness of the backup roll 110 can be reduced. Further, the friction between the base material 150 and the backup roll 110 can be reduced. Further, the influence of foreign matter adhering to the backup roll 110 can be reduced. As a result, the occurrence of spots and streaks on the optical film can be suppressed.
Further, by setting the thickness of the gas layer 170 to be equal to or less than the upper limit value, it is possible to prevent the base material 150 from fluttering on the backup roll 110. As a result, it is possible to prevent the base material 150 during transportation from coming into contact with the lip 123 of the die coater 120, causing damage to the base material 150 or breaking the base material 150 to damage the base material 150.

The thickness of the gas layer 170 at the position P150 of the base material 150 to which the coating liquid 160 is applied is the thickness of the gas layer 170 between the peripheral surface S3 of the backup roll 110 facing the die coater 120 via the base material 150 and the base material 150. It can be measured by measuring the thickness.
Specifically, it can be measured by the following method.
The die coater 120 is retracted from the backup roll 110, and the base material 150 is conveyed under the same conditions as when the coating liquid 160 is applied by the die coater 120. Using a spectroscopic interference type film thickness meter (for example, "Optical NanoGauge C13027-11" manufactured by Hamamatsu Photonics Co., Ltd.), the thickness of the gas layer 170 between the peripheral surface S3 and the base material 150 was measured at a plurality of points, and the thickness thereof was measured. The average value can be the thickness of the gas layer 170 at the position P150 of the base material 150 to which the coating liquid 160 is applied.

More specifically, for example, at the position of the base material 150 where the lip 123 of the die coater 120 faces when the coating liquid 160 is applied, the thickness of the gas layer 170 is measured at three points arranged in the width direction, and further. This measurement is carried out from the position of the base material 150 where the tip of the lip 123 of the die coater 120 faces, 6 points at the position upstream in the transport direction, and the position of the base material 150 where the tip of the lip 123 of the die coater 120 faces. The thickness of the gas layer 170 is measured at a total of 15 points at 6 points downstream in the direction, and the average value of the thickness of the gas layer 170 at these 15 points is the base material 150 to which the coating liquid 160 is applied. It can be the thickness of the gas layer 170 at position P150.

The distance between the adjacent measurement points in the transport direction of the base material 150 can be appropriately set depending on the size of the die coater 120 used and the like, and may be, for example, 30 mm or more and 70 mm or less, preferably 40 mm or more and 60 mm or less.
The distance between the adjacent measurement points in the width direction of the base material 150 can be appropriately set depending on the width of the base material 150 to be transported and the like, and may be, for example, 100 mm or more and 300 mm or less. It can be preferably 150 mm or more and 250 mm or less.

The thickness of the gas layer 170 may be measured using two laser displacement meters. Specifically, it may be measured by the following method. Match the measurement reference positions of the two laser displacement meters. The distance A from the measurement reference position to the peripheral surface S3 of the backup roll 110 is measured by one of the laser displacement meters. The distance B from the measurement reference position to the surface of the base material 150 facing the die coater 120 is measured by the other laser displacement meter. Further, the thickness T of the base material 150 is measured with a film thickness meter or the like. The thickness of the gas layer 170 can be obtained by subtracting the distance B and the thickness T from the distance A.

Further, the thickness of the gas layer 170 may be measured using a micropressure contact type displacement meter. Specifically, the displacement value of the backup roll 110 on the peripheral surface S3 is measured in advance, and this is set as a zero value. The displacement value A of the surface of the base material 150 facing the die coater 120 is measured, and the displacement value A is used as the basis. It may be obtained by reducing the thickness T of the material 150.

In the manufacturing method of the present embodiment, gas is supplied between the peripheral surface 110S of the backup roll 110 and the base material 150 in order to form the gas layer 170.
More specifically, in the manufacturing method of the present embodiment, the gas supply device 130 included in the manufacturing device 100 creates a gas between the peripheral surface S1 of the backup roll 110 on which the base material 150 starts to run and the base material 150. Gas is supplied by spraying. The manufacturing apparatus 100 includes an adjusting apparatus 131. The adjusting device 131 can adjust the amount of gas supplied from the gas supply device 130. Therefore, the manufacturing apparatus 100 can set the thickness of the gas layer 170 between the peripheral surface S3 of the backup roll 110 and the base material 150 at the position P150 of the base material 150 to which the coating liquid 160 is applied to be 1 μm or more and 20 μm or less. ..

[1.4. Second Embodiment]
In the method for manufacturing an optical film according to the second embodiment, gas is ejected from the peripheral surface of the backup roll so that the coating liquid is applied between the peripheral surface of the backup roll and the base material at the position of the base material. , A gas layer having a thickness of 1 μm or more and 20 μm or less is formed.

FIG. 2 is a schematic view showing an example of an optical film manufacturing apparatus capable of carrying out the optical film manufacturing method of the second embodiment. As shown in FIG. 2, the optical film manufacturing apparatus 200 includes a backup roll 210 and a die coater 120.

The backup roll 210 is hollow and has a gas chamber 211 inside. The peripheral surface 210S of the backup roll 210 is provided with a plurality of ventilation holes 210h that communicate with the gas chamber 211 provided inside the backup roll 210. By pumping gas into the gas chamber 211 of the backup roll 210 from a gas compressor (not shown) such as a pump, the gas can be ejected from the ventilation holes 210h. Vents 210h may be provided by forming the peripheral surface 210S of the backup roll 210 with a porous material.
The gas ejected from the ventilation holes 210h causes the base material 150 to float from the peripheral surface 210S of the backup roll 210, and as a result, the peripheral surface S3 of the backup roll 210 at the position P150 of the base material 150 to which the coating liquid 160 is applied. A gas layer 170 can be formed between the substrate 150 and the substrate 150. By adjusting the amount of gas pumped from the gas compressor, the thickness of the gas layer 170 can be 1 μm or more and 20 μm or less.

In this embodiment, the backup roll 210 is attached to the manufacturing apparatus 200 so as not to rotate, but in another embodiment, the backup roll 210 is driven in the direction D1 so as to rotate about the shaft 210R. In yet another embodiment, the backup roll 210 may be attached to the manufacturing apparatus 200 so as to be freely rotatable about the shaft 210R without being driven, and in yet another embodiment, the backup roll 210 may be attached to the manufacturing apparatus 200. The roll 210 may be driven so as to rotate about the shaft 210R in the direction opposite to the direction D1.

The manufacturing apparatus 200 may further include a gas supply apparatus 130 and an adjusting apparatus 131.
As a result, gas is ejected from the peripheral surface 210S of the backup roll 210, and the gas supply device 130 and the adjusting device 131 allow the gas to flow between the peripheral surface S1 of the backup roll 210 and the base material 150 where the base material 150 starts to follow. By spraying, gas can be supplied between the peripheral surface 210S of the backup roll 210 and the base material 150.

The manufacturing apparatus 200 may further include roll pairs 140.
As a result, the flow of gas from between the peripheral surface S2 of the backup roll 210 where the base material 150 starts to separate and the base material 150 toward the downstream in the transport direction of the base material 150 is restricted.

[1.5. Third Embodiment]
In the method for manufacturing an optical film according to the third embodiment, at least one convex portion is provided on the peripheral surface of the backup roll. FIG. 3 is a schematic view showing an example of an optical film manufacturing apparatus capable of carrying out the optical film manufacturing method according to the third embodiment.
The optical film manufacturing apparatus 300 includes a backup roll 310 and a die coater 120.

The backup roll 310 has the same configuration as the backup roll 110 except that a plurality of convex portions 311 are provided on the peripheral surface 310S. The shape and number of the convex portions 311 are not particularly limited, and for example, a grid-like convex portion; a plurality of convex portions that are linear parallel to the axial direction of the backup roll 310; and a plurality of convex portions arranged in a dot shape. It may be a department. The shape of the convex portion 311 may be a periodic shape or a non-periodic shape.

When the backup roll 310 having the convex portion 311 provided on the peripheral surface 310S rotates around the rotation shaft 310R to convey the base material 150, the base material 150 to be conveyed and the peripheral surface 310S of the backup roll 310 are placed between the backup roll 310. The gas layer 170 is formed. At the position P150 of the base material 150 to which the coating liquid 160 is applied, the convex portion so that the thickness of the gas layer 170 formed between the peripheral surface S3 of the backup roll 310 and the base material 150 is 1 μm or more and 20 μm or less. By setting the height of 311 it is possible to suppress uneven thickness of the coating layer and suppress the occurrence of spots and streaks on the optical film.

In the present embodiment, the height of the convex portion 311 provided on the peripheral surface 310S of the backup roll 310 is preferably 1 μm or more, more preferably 1.2 μm or more, still more preferably 1.5 μm or more, and preferably 20 μm. Hereinafter, it is more preferably 15 μm or less, still more preferably 12 μm or less. Here, when a plurality of convex portions 311 are provided on the peripheral surface 310S of the backup roll 310, the height of the convex portions 311 is an average value of the heights of the plurality of convex portions 311.
The height of the convex portion can be measured by using the peripheral length of the backup roll 310 as the evaluation length. Measuring devices include contact type displacement meters (eg, small electric micrometer "Minicom-M" (manufactured by Tokyo Seimitsu Co., Ltd., equipped with a micropressure contact head)) and non-contact type displacement meters (eg, spectroscopic interference laser displacement). A total "SI-F10" (manufactured by Keyence)) can be used.

The distance (pitch) between adjacent convex portions 311 is preferably 20 mm or more, more preferably 30 mm or more, preferably 70 mm or less, and more preferably 50 mm or less.

The example of the method of forming the convex portion 311 having a predetermined height on the peripheral surface 310S of the backup roll 310 is not particularly limited, but for example, a method of sandblasting the peripheral surface of the backup roll and a grindstone by grinder polishing. There is a method of polishing the surface of the backup roll under the condition that the chattering vibration occurs.

In this embodiment, the backup roll 310 is driven in direction D1 so as to rotate about the shaft 310R, but in another embodiment the backup roll 310 is not driven and is free around the shaft 310R. The backup roll 310 may be rotatably attached to the manufacturing apparatus 300, and in yet another embodiment, the backup roll 310 may be driven to rotate about the shaft 310R in the direction opposite to the direction D1. Good.

[2. Optical film manufacturing method and operation of manufacturing equipment]
In the optical film manufacturing method and the optical film manufacturing apparatus according to the above embodiments, the thickness between the peripheral surface of the backup roll and the base material is 1 μm or more and 20 μm or less at the position of the base material to which the coating liquid is applied. Form a gas layer. As a result, uneven thickness of the coating layer formed on the base material can be suppressed, and the occurrence of spots and streaks on the optical film can be suppressed. Further, since the generation of spots on the optical film can be suppressed, the cleaning frequency of the backup roll for removing the adhered foreign matter can be reduced. As a result, a high-quality optical film can be manufactured without stopping the manufacturing apparatus for a long period of time, and the productivity of the optical film is improved.

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.

Unless otherwise specified, the operations described below were performed under normal temperature and pressure conditions.

[Evaluation method]
(Evaluation method of streaks (horizontal) in the width direction)
A film piece having a width of 0.7 m and a length of 2 m was cut out from the obtained long optical film. At the time of cutting out, each side of the film piece was made parallel to the transport direction or the width direction of the optical film. The cut out film piece was sandwiched between two polarizing films, and an evaluation sample was prepared in a cross Nicol state. A surface light source is applied from behind the evaluation sample, and the state of the light passing through the evaluation sample is visually observed, and the presence or absence of the horizontal stage, the intensity of the horizontal stage, and the pitch of the horizontal stage if there is a strong horizontal stage are confirmed. did.
The intensity of the horizontal stage when there was a horizontal stage was evaluated by visually observing the color contrast (contrast between white and black) in the portion other than the horizontal stage portion and the horizontal stage portion. When the contrast was strong, the strength of the horizontal row was evaluated as strong, and when the contrast was weak, the strength of the horizontal row was evaluated as weak.
Regarding the pitch of the horizontal row, a line was drawn on the strong horizontal row with a felt-tip pen, and the average value was calculated for the interval between the 10 lines and used as the pitch of the horizontal row of the optical film.

(Evaluation method of spot unevenness)
A film piece having a width of 0.7 m and a length of 2 m was cut out from the obtained long optical film. At the time of cutting out, each side of the film piece was made parallel to the transport direction or the width direction of the optical film. The cut out film piece was sandwiched between two polarizing films, and an evaluation sample was prepared in a cross Nicol state. A surface light source was applied from behind the evaluation sample, and the state of the light passing through the evaluation sample was visually observed to confirm the presence or absence of round spot-like defects. The number of spot-like defects existing in the range of 0.7 m in width × 2 m in length was counted and converted into the number per 1 m ^{2 of} the optical film.

[Example 1]
A coating solution containing a liquid crystal compound, a chiral agent, an antioxidant, a surfactant, a polymerization initiator, and a solvent was prepared. Conditions: The viscosity of the coating liquid measured by an E-type viscometer cone rotor at 23 ° C. and 100 rpm was 2.8 to 3 mPa · s.

As a base material, a long stretched film (“Zeonor film” manufactured by Zeon Corporation, thickness 77 μm, width 700 mm) made of a resin containing an alicyclic structure-containing polymer was prepared.
The static friction coefficient between the base material and the iron plate (maximum surface roughness Ry = 0.6 μm) was measured using a friction measuring instrument (“FRICTION TESTER TR-2” manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a speed of 20 mm / min and a measuring distance of 30 mm. When measured under the conditions of a load range of 10 N and a thread mass of 200 g, it was 1.0.
The maximum surface roughness Ry of the iron plate was measured according to JIS B 0601-1994. Specifically, as a measuring device, a small surface roughness measuring machine "Surftest SJ-310" (manufactured by Mitutoyo Co., Ltd.) was used, and the evaluation length was 4.0 mm (cutoff value λc 0.8 mm × 5). , Measured by tracing the surface with a diamond probe.
As the iron plate, a plate having a hard chrome plating on the surface and a plating thickness of 100 μm was used.

As an optical film manufacturing apparatus, a manufacturing apparatus 100 including a backup roll 110, a die coater 120, a gas supply apparatus 130, an adjusting apparatus 131, and a roll pair 140 shown in FIG. 1 was prepared. The diameter of the backup roll 110 is 150 mm.
The amount of gas blown from the gas supply device 130 was adjusted to 150 L / min.
The first auxiliary roll 141 constituting the roll pair 140 has a diameter of 10 mm, and its peripheral surface 141S is formed of rubber. The second auxiliary roll 142 has a diameter of 10 mm, and its peripheral surface 142S is made of metal (aluminum material).
The transport speed of the base material was set to 10 m / min.
The tension of the base material was 60 N.
A drive device (not shown) was attached to the backup roll 110, and the backup roll 110 was rotated in the direction D1.

Under the above conditions, the thickness of the gas layer 170 was measured by a spectroscopic interference type film thickness meter (“Optical NanoGauge C13027-11” manufactured by Hamamatsu Photonics Co., Ltd.) while transporting the base material by the manufacturing apparatus 100. The measurement was carried out as follows with the die coater 120 retracted from the coating position.
At the position of the base material 150 where the tips of the lips 123 of the die coater 120 face each other when the coating liquid 160 is applied, the thickness of the gas layer 170 is measured at three points arranged in the width direction, and this measurement is further performed on the die coater 120. At 6 points upstream from the position of the base material 150 facing the tip of the lip 123 of the die coater 120 and at a position downstream from the position of the base material 150 facing the tip of the lip 123 of the die coater 120. The average value of the thickness of the gas layer 170 at these 15 points was calculated for each of the 6 points. That is, the thickness of the gas layer is measured at three points arranged in the width direction of the backup roll 110, and this measurement is performed twice more in the circumferential direction of the backup roll 110 toward the upstream in the transport direction of the base material, and the backup roll 110. The average value of the thickness of the obtained gas layer was obtained by repeating the process twice more in the circumferential direction of the substrate toward the downstream in the transport direction of the base material. The distance between the measurement points in the width direction of the base material was 200 mm. The distance between the measurement points in the transport direction of the base material was 50 mm.

The coating liquid was applied to the base material using the manufacturing apparatus 100. The slit 124 of the die coater 120 was adjusted to 120 μm, the distance between the lip 123 and the backup roll 110 was set to 100 μm, and the dry film thickness of the coating liquid was 2.5 μm.

After applying the coating liquid to the substrate to form a coating layer, the coating layer is dried at 40 ° C. for 1 minute and then at 110 for 1 minute, and then the dried coating layer is irradiated with ultraviolet rays to cure the coating layer. And obtained an optical film.

With respect to the obtained optical film, streaks (horizontal steps) and spots (spot unevenness) were evaluated by the above method. The results are shown in Table 1.

[Example 2]
An optical film was obtained in the same manner as in Example 1 except for the following items, and this was evaluated.
-The drive device attached to the backup roll 110 has been removed so that the backup roll 110 can rotate freely.
-The transport speed of the base material was set to 10 m / min.
-The tension of the base material was set to 60 N or less.
The results are shown in Table 1.

[Example 3]
An optical film was obtained in the same manner as in Example 1 except for the following items, and this was evaluated.
-Instead of the manufacturing apparatus 100, the manufacturing apparatus 300 including the backup roll 310 and the die coater 120 shown in FIG. 3 was used. The backup roll 310 has a plurality of convex portions 311 that are linear in parallel with the axial direction of the backup roll 310. The maximum surface roughness Ry of the backup roll 310 at an evaluation length of 4.0 mm, measured according to JIS B 0601-1994, is 1.2 μm. For the maximum surface roughness, a small surface roughness measuring machine "Surftest SJ-310" (manufactured by Mitutoyo Co., Ltd.) was used as the measuring device, and the evaluation length was 4.0 mm (cutoff value λc 0.8 mm × 5). The measurement was performed by tracing the surface with a diamond probe.
The height of the convex portion 311 measured by measuring the peripheral length of the backup roll 310 as the evaluation length is 1.5 μm, and the distance (pitch) between the adjacent convex portions 311 is 20 mm. Here, the height and pitch of the convex portion 311 were measured by a spectroscopic interference laser displacement meter "SI-F10" manufactured by KEYENCE CORPORATION. The diameter of the backup roll 310 is 150 mm.
-The transport speed of the base material was set to 10 m / mim.
-The tension of the base material was set to 150 N.
A drive device (not shown) was attached to the backup roll 310, and the backup roll 310 was rotated in the direction D1.
The results are shown in Table 1.

[Example 4]
An optical film was obtained in the same manner as in Example 1 except for the following items, and this was evaluated.
-Instead of the manufacturing apparatus 100, the manufacturing apparatus 200 provided with the backup roll 210 and the die coater 120 shown in FIG. 2 was used. The peripheral surface 210S of the backup roll 210 is made of a porous material.
The base material was conveyed while ejecting gas (air) from the peripheral surface 210S of the backup roll 210.
The results are shown in Table 1.

[Example 5]
An optical film was obtained in the same manner as in Example 1 except for the following items, and this was evaluated.
-The gas supply device 130, the adjusting device 131, and the roll pair 140 were removed from the manufacturing device 100.
The backup roll 110 was rotated in the direction opposite to the direction D1.
The results are shown in Table 1.

[Comparative Example 1]
An optical film was obtained in the same manner as in Example 1 except for the following items, and this was evaluated.
-The gas supply device 130, the adjusting device 131, and the roll pair 140 were removed from the manufacturing device 100.
-The transport speed of the base material was set to 4 m / mim.
-The tension of the base material was set to 130 N.
The results are shown in Table 2.

[Comparative Example 2]
An optical film was obtained in the same manner as in Example 1 except for the following items, and this was evaluated.
-The gas supply device 130, the adjusting device 131, and the roll pair 140 were removed from the manufacturing device 100.
-The transport speed of the base material was set to 10 m / mim.
-The tension of the base material was set to 0N.
The results are shown in Table 2.

From the above results, the following matters can be understood.
According to the method for producing an optical film according to Examples 1 to 5, which forms a gas layer having a thickness of 1 μm or more and 20 μm or less, the generation of thick streaks (horizontal steps) generated in the width direction of the optical film is suppressed, and It can be seen that the occurrence of spots (spot unevenness) can be suppressed.
On the other hand, in the manufacturing method according to Comparative Example 1 in which the thickness of the gas layer is less than 1 μm, it can be seen that strong streaks (horizontal steps) are generated on the optical film and spots (spot unevenness) are remarkably generated.
Further, it can be seen that in the production method according to Comparative Example 2 in which the thickness of the gas layer is larger than 20 μm, the occurrence of spots is suppressed, but strong streaks are generated.

100: Manufacturing equipment 110: Backup roll 110R: Rotating shaft 110S: Peripheral surface 120: Die coater 121: Extruding device 122: Pipe line 123: Lip 124: Slit 130: Gas supply device 131: Adjusting device 140: Roll pair 141: First Auxiliary roll 141R: Rotating shaft 141S: Peripheral surface 142: Second auxiliary roll 142R: Rotating shaft 142S: Peripheral surface 150: Base material 160: Coating liquid 161: Coating layer 170: Gas layer 200: Manufacturing equipment 210: Backup roll 210R: Shaft 210S: Peripheral surface 210h: Vent hole 211: Gas chamber 300: Manufacturing equipment 310: Backup roll 310R: Rotating shaft 310S: Peripheral surface 311: Convex part D1: Direction S1: Peripheral surface S2: Peripheral surface S3: Peripheral surface

Claims (14)

A method for producing an optical film, which comprises a step of applying a coating liquid to the surface of the base material with a die coater while transporting the base material along the peripheral surface of the backup roll.
A method for producing an optical film, wherein a gas layer having a thickness of 1 μm or more and 20 μm or less is formed between a peripheral surface of the backup roll and the base material at a position of the base material to which the coating liquid is applied. The method for producing an optical film according to claim 1, wherein the gas layer is formed by supplying a gas between the peripheral surface of the backup roll and the base material. The method for producing an optical film according to claim 2, wherein the gas is supplied by spraying the gas between the peripheral surface of the backup roll and the base material on which the base material starts to run. The method for producing an optical film according to claim 2, wherein the gas is supplied by ejecting the gas from the peripheral surface of the backup roll. The invention according to any one of claims 1 to 4, wherein the flow of gas is restricted from between the peripheral surface of the backup roll where the base material starts to separate and the base material toward the downstream in the transport direction of the base material. A method for manufacturing an optical film. A roll pair composed of a first auxiliary roll and a second auxiliary roll is provided between the peripheral surface of the backup roll at which the base material starts to separate and the base material, and the peripheral surface of the backup roll and the base are provided by the roll pair. Close the gap with the material,
The first auxiliary roll has a rotation axis parallel to the rotation axis of the backup roll, and is in contact with the peripheral surface of the backup roll.
The second auxiliary roll has a rotation axis that is parallel to the rotation axis of the backup roll and is located at a position farther from the rotation axis of the backup roll than the rotation axis of the first auxiliary roll. In contact with the peripheral surface of the auxiliary roll and the base material,
The method for producing an optical film according to claim 5, wherein the hardness of the peripheral surface of the first auxiliary roll is lower than the hardness of the peripheral surface of the second auxiliary roll. The method for producing an optical film according to any one of claims 1 to 6, wherein at least one convex portion is provided on the peripheral surface of the backup roll. The method for producing an optical film according to claim 7, wherein the at least one convex portion has a height of 1 μm or more and 20 μm or less. The method for producing an optical film according to any one of claims 1 to 8, wherein the backup roll is freely rotatable. The method for producing an optical film according to any one of claims 1 to 9, wherein the base material has a coefficient of static friction with iron of 0.7 or more. A backup roll that conveys the base material along the peripheral surface,
A die coater that applies a coating solution to the surface of the base material,
A gas supply device that supplies gas between the peripheral surface of the backup roll and the base material,
It is supplied from the gas supply device so that the thickness of the gas layer between the peripheral surface of the backup roll and the base material at the position of the base material to which the coating liquid is applied is 1 μm or more and 20 μm or less. An adjusting device that adjusts the amount of gas,
Optical film manufacturing equipment, including. Further including a roll pair consisting of a first auxiliary roll and a second auxiliary roll,
The first auxiliary roll has a rotation axis parallel to the rotation axis of the backup roll, and is in contact with the peripheral surface of the backup roll.
The second auxiliary roll has a rotation axis that is parallel to the rotation axis of the backup roll and is located at a position farther from the rotation axis of the backup roll than the rotation axis of the first auxiliary roll. It is provided so as to be in contact with the peripheral surface of the auxiliary roll and the base material to be conveyed.
The optical film manufacturing apparatus according to claim 11, wherein the hardness of the peripheral surface of the first auxiliary roll is lower than the hardness of the peripheral surface of the second auxiliary roll. The optical film manufacturing apparatus according to claim 11 or 12, wherein at least one convex portion is provided on the peripheral surface of the backup roll. The optical film manufacturing apparatus according to any one of claims 11 to 13, wherein the backup roll is freely rotatable.

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