TW201318948A - Method for winding film, method for producing film and method for producing polarizer - Google Patents

Abstract

This invention is to decrease black band defects and winding shift defects. A method for winding a film is provided, which includes a winding step for winding a wound film at a winding shaft to the winding shaft, and a sliding step for sliding the winding shaft to-and-fro along a width direction in the winding step. In the sliding step, when a thickness of the film wound on the winding shaft during sliding the winding shaft to-and-fro once is set as a period, an average value of the period starting from winding the film from half of a predetermined thickness to the predetermined thickness is higher than an average value of the period starting from winding the film on the winding shaft until the film is wound to half of the predeterimined thickness so as to control at least one of a sliding velocity of the winding shaft and a rotating velocity of the winding shaft.

Description

Film winding method, film manufacturing method, and method of manufacturing polarizing plate

The present invention relates to a film winding method, a film manufacturing method, and a method of producing a polarizing plate.

Various films such as optical films have been used since. As a method of producing the films, for example, there is a method in which a coating film is formed by applying a coating liquid onto a long support to form a film having various functions. Moreover, the elongated support itself is also referred to as a type of film.

The films are all wound up and stored once in the form of a film roll and passed to the next step.

Thus, the winding of the film must occur, and the film winding step is an indispensable step in the production of the film.

As the film winding method described above, Patent Document 1 describes a winding method of a film, which comprises: a straight winding step of winding the film on a winding core in such a manner that side edges of the film are aligned And an Oscillating Winding step of causing the above-mentioned side edges to be periodically shifted in a certain range with respect to the width direction of the film after the direct winding step, in the width direction of the film The film or the above-described winding core periodically vibrates to wind the above film on the above-mentioned winding core.

Thereby, it is possible to perform winding so that the edge curl and the winding offset do not occur on the wound film roll.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-150041

However, in the film winding method described in Patent Document 1, it is not possible to eliminate a defect called blocking or black band caused by the convex portions of the film being closely adhered to each other on the film roll. .

The present invention has been made in view of the above circumstances, and an object of the invention is to provide a film winding method, a film manufacturing method, and a method for producing a polarizing plate which can simultaneously reduce both black strip defects (black band defects) and winding offset defects.

The problem of the present invention can be solved by the following inventions.

That is, the film winding method of the present invention winds the film on the winding shaft to a predetermined thickness, and is mainly characterized by comprising: a winding step of winding the roll by rotating the winding shaft The film on the winding shaft is wound on the winding shaft; and a sliding step in which the winding shaft is relatively slid back and forth in the width direction of the film with respect to the film immediately before winding; in the sliding step, When the thickness of the film wound on the winding shaft during the sliding of the winding shaft once and for all is set to a period, the thickness is from half the thickness of the predetermined thickness until the film is wound up to a predetermined thickness. The average value of the cycle is larger than the average value of the period from when the film is wound around the winding shaft until the film is wound to a thickness half of a predetermined thickness, and the winding axis is opposed to The relative sliding speed of the film immediately before winding, that is, at least one of the relative sliding speed and the rotational speed of the winding shaft, is controlled.

Thereby, both the black belt defect and the winding offset failure can be reduced.

Moreover, the main feature of the film winding method of the present invention is that it is sliding In the step, at least one of the relative sliding speed and the rotational speed of the winding shaft is increased from the time when the film is wound around the winding shaft until the film is wound to a predetermined thickness, and the cycle is gradually increased. Control.

Thereby, both the black belt defect and the winding offset failure can be further reduced.

Further, in the film winding method of the present invention, the film is wound around the winding shaft to a predetermined thickness, and the main feature is that the winding step includes winding the winding shaft by winding the winding shaft. The film on the shaft is wound on the winding shaft; and a sliding step in which the winding shaft is relatively slid back and forth in the width direction of the film with respect to the film immediately before winding; in the sliding step, When the distance between the half of the distance at which the winding shaft is moved back and forth is set to an amplitude, the average value of the amplitude between the thickness of one half of the predetermined thickness and the winding of the film to a predetermined thickness is smaller than The relative value of the winding axis relative to the film immediately before winding is started so that the film starts to wrap around the winding axis until the film is wound up to a half thickness of a predetermined thickness. The amount of sliding is controlled by the amount of relative sliding.

Thereby, both the black belt defect and the winding offset failure can be reduced.

Further, the film winding method of the present invention is mainly characterized in that, in the sliding step, the film is wound from the time when the film is wound around the winding shaft until the film is wound up to a predetermined thickness, and the amplitude is gradually decreased. Control the relative slip amount.

Thereby, both the black belt defect and the winding offset failure can be further reduced.

Further, the film production method of the present invention produces a film with a coating film, which is mainly characterized by comprising: a step of coating a coating liquid on a long support; and drying the applied coating liquid to form an attached film a step of coating the film; and The step of winding the film with the coating film by any of the above winding methods.

Thereby, it is possible to manufacture a film which reduces both the black belt defect and the winding deviation.

Further, the method for producing a polarizing plate of the present invention is a method for producing a polarizing plate in which a protective film is adhered to at least one surface of a polarizing element, and includes a winding step of winding the protective film into a roll by any of the above winding methods. a bonding step of winding off the wound protective film and bonding the developed protective film to at least one side of the polarizing element; and a cutting step of bonding the polarized light of the protective film The component is cut to a predetermined size.

The present invention can reduce both black belt defects and poor winding offset.

Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the accompanying drawings. Here, the same reference numerals are given to the same elements having the same functions. In addition, in the present specification, when "~" is used to indicate the numerical range, the numerical values of the upper and lower limits indicated by "~" are also included in the numerical range.

<film production line>

The film production line of the present invention will be described with reference to Fig. 1 . Fig. 1 is a schematic view showing a film production line. As shown in FIG. 1, the film production line 10 of the present invention mainly comprises a film manufacturing apparatus 20 and a winding device 30.

In Fig. 1, the film manufacturing apparatus 20 is extremely simplified and is merely described as a casing because it is conceivable to use various apparatuses as the film manufacturing apparatus 20. For example, the film manufacturing apparatus 20 can be manufactured by a melt film forming method, a solution film forming method, or the like. The support may be a device for forming a film by applying a coating liquid onto a support, but is not limited thereto, as long as the film to be produced is finally a film (or a support) wound by a winding device. ) can also be a device for making any film (or support).

Here, a case where the film manufacturing apparatus 20 is a slot die type coating apparatus will be described as an example. The film manufacturing apparatus 20 as a slit die coating apparatus applies the coating liquid from the slit to the moving support. The coating liquid supplied onto the support is formed into a film on the support, and then dried, whereby the solvent component in the coating liquid evaporates to form a coating film which is only a solid component.

Here, a knurling portion 42 which is a portion in which fine irregularities are formed in advance is formed at both end portions of the support. The slit die coating device also applies a coating liquid to the embossed portion 42 to form a coating film.

Next, the winding device 30 will be described. The winding device 30 mainly includes a winding shaft 60, a pair of arms 70, a motor (not shown), an oscillate portion 62, and a control portion (not shown).

The winding shaft 60 winds the film 40 supplied from the film manufacturing apparatus 20 by the guide roller 50 by rotation. The arm 70 grips the winding shaft 60 from both sides in the longitudinal direction. The motor rotates the winding shaft 60. The oscillating portion slides the arm 70 back and forth in the direction indicated by the arrow of the mark 90 (the width direction of the film 40).

The oscillating portion 62 may include, for example, an oscillating motor 61, an eccentric cam 64, and a spring 66. In this case, the oscillating motor 61 rotates the eccentric cam 64, and the eccentric cam 64 presses the arm 70 that urges the eccentric cam 64 by the spring 66, thereby sliding the arm 70 back and forth. Also, shown here The oscillating portion is merely an example, and the structure and the method of winding while sliding back and forth may be of any form.

Further, although the oscillating portion 62 slides the arm 70 back and forth to slide the winding shaft 60 back and forth, the oscillating portion 62 is not limited thereto, and the winding shaft 60 may be directly slid back and forth.

Here, the oscillating portion for sliding the winding shaft back and forth is shown. However, the present invention is not limited thereto, and a method of sliding the transport position of the film 40 back and forth may be employed. That is, the manner in which the winding shaft 60 relatively slides back and forth with respect to the film 40 immediately before being wound can be employed. The oscillating portion in this case slides the film 40 immediately before being wound around the winding shaft 60 back and forth.

Further, in the present invention, the case where the winding shaft is relatively slid back and forth with respect to the film immediately before being wound as described above is referred to as oscillation. The control unit controls the rotational speed, the oscillation speed, and the amount of oscillation movement (the amount of back and forth sliding) of the winding shaft 60.

<Film winding method>

The film winding method of the present invention is characterized in that it oscillates when the film 40 is wound, and is characterized in particular by the oscillation method. Therefore, the oscillation method of the present invention will be described in more detail with reference to Figs. 2, 3(A) and 3(B). 2 is a schematic cross-sectional view in the width direction of a film wound around a winding shaft. 3(A) and 3(B) are schematic cross-sectional views showing a part of a film to be wound.

When the film 40 is wound around the winding shaft 60, the film is wound while being oscillated. Therefore, both ends of the cross section of the wound film 40 in the width direction have a zigzag shape as shown in Fig. 2 . Here, the width of the film 40 is the same, so in the zigzag-shaped mountain and valley portions, when the right end is a mountain portion, the left end is a valley portion, when the right side When the end is the valley, the left end is the mountain.

As shown in Fig. 2, in the present invention, the width of the apex and the apex of the mountain portions adjacent to each other is referred to as a period, and the width of the bottom of the valley portion and the apex of the mountain portion (through the bottom of the valley portion and the winding axis 60) The straight line perpendicular to the axis of rotation and the shortest distance from the apex of the mountain portion adjacent to the valley portion and perpendicular to the winding axis 60 are referred to as amplitudes.

In other words, the period is the thickness of the film wound on the winding shaft 60 during the period in which the winding shaft 60 is slid back and forth once, and the amplitude is a distance that makes the winding shaft 60 move halfway back and forth, that is, It is not the distance that slides in a single lane for the distance to slide back and forth.

Here, the control of the cycle is achieved by the relative sliding speed of the winding shaft 60 with respect to the film immediately before winding (hereinafter, simply referred to as the sliding speed) and the winding speed of the winding shaft 60 ( At least one of the rotational speeds is controlled. Further, the control of the amplitude can be achieved by controlling the relative sliding amount of the winding shaft 60 with respect to the film immediately before winding (hereinafter referred to simply as the sliding amount).

In the present invention, the oscillation is performed in such a manner that either or both of the winding shafts 60 are smaller than the side farther from the winding shaft 60, or are separated. The amplitude of the side closer to the winding shaft 60 is larger than the side farther from the winding shaft 60. Preferably, in the case where the period is small, the period is gradually increased from the side closer to the winding shaft 60, and the period is gradually increased, and preferably, when the amplitude is large, the winding axis 60 is closer. One side begins to advance to the outside, and the amplitude gradually decreases.

Thereby, the defect called adhesion or black band can be reduced (referred to in the present invention) Both black belt defects are poor, and the winding offset is poor. Here, the black belt defect and the winding offset failure will be described below.

3(A) and 3(B) show schematic cross sections of the film number layer when the film 40 is wound. When the film 40 is wound on the winding shaft 60, as shown in FIG. 3(A), there are cases where the convex portions 100 in the film 40 overlap at the same position. In this case, as several layers are wound, the pressure is applied more strongly at the portion of the convex portion 100, thereby adhering the portion, or extending due to pressure, resulting in deterioration of the quality of the product. Moreover, if the portion is viewed from the outside, the portion looks like a black belt. The above situation is a bad black belt.

Therefore, as shown in FIG. 3(B), when the film 40 is wound, the winding is performed while the film is wound, and the convex portion 100 is shifted, so that occurrence of black belt defects can be prevented. However, by winding while oscillating, the adhesion is deteriorated, so that the winding offset is liable to occur. The defect of the winding offset is a problem in which the position of both side ends of the film roll that is wound up as a film is in a state after the winding is completed, that is, a state in which the position is partially shifted from the initial state.

In the case of the winding offset failure and the black belt defect, there is an inverse relationship between the methods for reducing these defects. Therefore, if one of the defects is reduced, the other failure increases, and it is difficult to simultaneously reduce the two types of defects. In other words, the closer the winding is, the more the winding offset is prevented, but the black belt defect is likely to be formed. If the winding is not performed, the black belt defect is less likely to form, but the winding offset is likely to be formed.

As a result of active research, the inventors have found that the cycle and amplitude of the oscillation are changed by a specific method, whereby both the winding offset defect and the black band defect can be simultaneously reduced.

<evaluation>

An evaluation was made to change the oscillation and wind the film to form a film roll. In Comparative Examples 1 to 4, the cycle and the amplitude of the oscillation were not changed, and a film roll was produced. In Examples 1 to 4, a film roll was produced by changing the period or amplitude.

The occurrence of black belt defects and winding offset defects of the produced film roll was investigated. The black strip defect is represented by four stages of the strength of the adhesion trace remaining on the film in A (none), B (very weak), C (weak), and D (strong). In the case of the winding offset failure, the film roll was moved in the axial direction of the film roll, and the film roll was suddenly stopped, thereby checking whether or not the winding deviation occurred. The occurrence of the winding offset is in the order of ease of winding deviation, that is, the order in which the winding offset resistance is strong to weak, and is composed of A (strong), B (slightly strong), C (slightly weak), and D (weak). 4 stages to indicate. Here, any of the cases from A to C is a range of acceptable products without any defect. Only D is bad. The evaluation contents and evaluation results are shown in Table 1, and the meanings of the symbols of the evaluation results are shown in Table 2.

Referring to Table 1, the period "5→15" of the example 1 is as follows, as described in the test preparation, as follows: the average value of the oscillation period on the core side of the center of the thickness of the film roll, that is, in the thickness direction of the film roll The average value of the oscillation period between the nearest portion of the core and the portion of the outermost portion from the middle of the outermost portion (hereinafter referred to as the center-core portion) is 5 mm, which is larger than the thickness of the film roll. The average value of the oscillation period on the outer peripheral side of the center, that is, the portion closest to the outermost portion and the outermost portion in the thickness direction of the film roll The average value of the oscillation period from the middle of the minute to the outermost portion (hereinafter referred to as the center-outer portion) is 15 mm, and the oscillation period gradually increases from the core side toward the outermost side in the thickness direction of the film roll. Increase.

The period "2→15" of the example 3 differs only in numerical values, and has the same meaning as the period "5→15" of the example 1.

Further, the "15→5" of the amplitude of the example 4 indicates that the average value of the oscillation amplitude of the center-core portion is 15 mm, and the average value of the oscillation amplitude of the center-outer portion is 5 mm, and the thickness of the film roll is In the direction, the oscillation amplitude gradually decreases from the core side toward the outermost side.

Further, "5/15" of the example 2 is as described in the test preparation, and the oscillation period of the center-core portion is fixed to 5 mm, and the oscillation period of the center-outer portion is fixed to 15 mm.

Similarly, "15/5" of the example 5 indicates that the oscillation amplitude of the center-core portion is fixed at 15 mm, and the oscillation amplitude at the center-outer portion is fixed at 5 mm.

The black belt defect is more likely to occur as the winding tension is larger, and the winding offset is less likely to occur as the winding tension is smaller. When Comparative Example 1 to Comparative Example 4 of Table 1 were observed, when the winding tension was as large as 400 N, the black belt defect was D, the black belt defect was C when the winding tension was 350 N, and the winding tension was 300 N. The bad band is B.

On the other hand, in Examples 1 to 4 in which the period or amplitude of the oscillation was changed, although the winding tension was as large as 500 N, the black belt defect was A or C.

Further, in Comparative Examples 1 to 4, when the winding tension was 300 N, the winding deviation was poor, and when the winding tension was 350 N, the winding was biased. Poor shift to C. On the other hand, in Examples 1 to 4, the winding offset defects were both A or B.

When referring to Example 1, the black belt defect was also A, and the winding offset was also bad, and good results were obtained. When Example 1 was compared with Example 2, in Example 1, the winding offset was poor, and in contrast, the winding offset in Example 2 was B. From this, it is understood that the winding offset can be further reduced by gradually changing the oscillation period.

If Example 1 is compared with Example 3, the period of oscillation in Example 1 is 5→15, and the black band defect is A. In contrast, in Example 3, the period is 2→15, and the black belt defect is C. From this, it can be seen that the oscillation period of the center-core portion is larger than that of 2 mm (about 33 times the film thickness), and the black band defect of 5 mm (about 83 times the film thickness) is greater.

If Example 1 is compared with Example 4, the black strip defect is A, and the winding offset is both A. Therefore, even if the average value of the oscillation period is changed from 5 mm (center-core portion) to 15 mm (center-outer portion), the average value of the oscillation amplitude is changed from 15 mm (center-core portion) to 5 mm. Both mm (center-outer side) can reduce black belt defects and poor winding offset. From these findings, good results can be obtained even if both the oscillation period and the amplitude are simultaneously changed.

If Example 4 was compared with Example 5, in Example 4, the winding offset was also A, whereas in Example 5, the winding offset was B. From this, it is understood that the winding offset can be further reduced by gradually changing the oscillation amplitude.

According to the above, by averaging the oscillation period of the center-outer portion The value is larger than the average value of the oscillation period of the center-volume core portion, and the black belt defect and the winding offset defect can be reduced. At this time, it is understood that the black band defect and the winding offset defect can be further reduced by gradually increasing the oscillation period from the core side toward the outside.

Further, it can be seen that the average value of the oscillation amplitude of the center-outer portion is smaller than the average value of the oscillation amplitude of the center-core portion, and the black strip defect and the winding offset defect can be reduced. At this time, it is understood that the black band defect and the winding offset defect can be further reduced by gradually decreasing the oscillation amplitude from the winding core side toward the outer side.

Further, according to the study by the inventors, it is preferable that the average oscillation period of the center-core portion is 40 to 250 times the film thickness, and the average oscillation period of the center-outer portion is 80 to 1000 times the film thickness. In this case, it is also more preferable that the average oscillation period of the center-outer portion is 3% or more larger than the average oscillation period of the center-core portion. Further, at this time, it is also known that the oscillation period gradually changes from the core side to the outer side.

Similarly, it is also known that with respect to the average oscillation amplitude, it is preferable that the average oscillation amplitude of the center-core portion is 1.5 to 4 times the width of the film at the end of the film or the width of the film formed on the knurl, and the center - The average oscillation amplitude of the outer portion is 0.01 to 2 times the width of the film at the end of the film or the width of the film formed on the knurl. In this case, it is also preferable that the average oscillation amplitude of the center-outer portion is smaller than the average oscillation amplitude of the center-core portion by 3% or more. Further, at this time, it is also known that the oscillation period gradually changes from the core side to the outer side.

<Method of Manufacturing Polarizing Plate>

Next, the manufacture of a polarizing plate using the film winding method of the present invention The method is explained. The polarizing plate refers to an element formed by protecting a film on one side or two layers of a polarizing element.

Examples of the polarizing element include adsorption of iodine or a dichroic dye to a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partial saponified film. The dichroic substance such as a uniaxially stretched film, a polyether-based alignment film such as a dehydrated material of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizing element comprising a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferred.

As a material for forming a protective film laminated on one surface or both surfaces of the polarizing element, transparency, mechanical strength, thermal stability, moisture shielding property, isotropic property, and the like are preferable. For example, a polyester-based polymer such as polyethylene terephthalate or polyethylene naphthalate, a cellulose-based polymer such as diethyl fluorene cellulose or triacetyl cellulose, and a polymethyl group may be mentioned. An acrylic polymer such as methyl acrylate, a styrene polymer such as polystyrene or acrylonitrile-styrene copolymer (AS resin), or a polycarbonate polymer. Further, examples thereof include polyethylene, polypropylene, ring-based or polyolefin having a norbornene structure, a polyolefin-based polymer such as an ethylene-propylene copolymer, a vinyl chloride-based polymer, nylon or an aromatic polyamine. Amidoxime polymer, quinone imine polymer, fluorene polymer, polyether fluorene polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, metachloroethylene A vinyl polymer, a vinyl butyral polymer, an aryl ester polymer, a polyoxymethylene polymer, an epoxy polymer, or a blend of the above polymers, etc., also serve as a polymer for forming the above protective film. Example.

As the material for forming the protective film, consider the materials listed above, but A cellulose-based polymer such as TAC (Triacetyl Cellulose) or the like is preferable in view of polarization characteristics, durability, and the like, and a TAC film is particularly preferable.

Further, a hard coat layer may be provided on the surface of the protective film on which the polarizing element is not bonded, or an anti-reflection treatment or a treatment for diffusion or anti-glare may be performed.

When the method for producing a polarizing plate using the film winding method of the present invention is described, a protective film is produced on the film production line, and the protective film is wound into a roll shape by the winding method of the present invention.

Next, the protective film wound in a roll shape and the polarizing element wound in a roll shape are separately developed, and a protective film is bonded to one surface or both surfaces of the polarizing element. When the protective film is adhered to both surfaces of the polarizing element, the protective film can be simultaneously bonded to both sides of the polarizing element by using two rolls of a protective film wound in a roll shape.

A water-based adhesive or the like can be used for bonding the polarizing element to the protective film. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, an ethylene-based latex, an aqueous polyurethane, and an aqueous polyester.

Next, the polarizing element to which the protective film is bonded is cut into a predetermined size. Thus, a polarizing plate cut to a predetermined size can be manufactured.

10‧‧‧ film production line

20‧‧‧Film manufacturing equipment

30‧‧‧Winding device

40‧‧‧ film

42‧‧‧Rolling section

50‧‧‧guide roller

60‧‧‧Winding shaft

61‧‧‧Oscillation motor

62‧‧‧Oscillation Department

64‧‧‧Eccentric cam

66‧‧‧ Spring

70‧‧‧arm

90‧‧‧ mark

100‧‧‧ convex

Fig. 1 is a schematic view showing a film production line.

2 is a schematic cross-sectional view in the width direction of a film wound around a winding shaft.

3(A) and 3(B) are schematic cross-sectional views showing a part of a film to be wound.

10‧‧‧ film production line

20‧‧‧Film manufacturing equipment

30‧‧‧Winding device

40‧‧‧ film

42‧‧‧Rolling section

50‧‧‧guide roller

60‧‧‧Winding shaft

61‧‧‧Oscillation motor

62‧‧‧Oscillation Department

64‧‧‧Eccentric cam

66‧‧‧ Spring

70‧‧‧arm

90‧‧‧ mark

Claims (6)

A film winding method of winding a film on a winding shaft to a predetermined thickness, and comprising: a winding step of rotating a film wound on the winding shaft by rotating the winding shaft Winding on the winding shaft; and sliding step of sliding the winding shaft relatively back and forth in the width direction of the film with respect to the film immediately before winding; in the sliding step When the thickness of the film wound around the winding shaft during the sliding of the winding shaft once is set to a cycle, the film is wound up to the above-mentioned specification from a thickness of half of the predetermined thickness. The average value of the period between the thicknesses is larger than the average value of the period from when the film is wound around the winding shaft until the thickness of the film is half of the predetermined thickness. In a manner, at least one of a relative sliding speed of the winding shaft with respect to the film immediately before winding, that is, a relative sliding speed and a rotational speed of the winding shaft is controlled. The film winding method according to claim 1, wherein in the sliding step, the cycle is gradually formed from when the film is wound around the winding shaft until the film is wound up to the predetermined thickness. In a manner of increasing, at least one of the relative sliding speed and the rotational speed of the winding shaft is controlled. A film winding method for winding a film on a winding shaft to a predetermined thickness, and comprising: a winding step of winding a film wound on the winding shaft on the winding shaft by rotating the winding shaft; and a sliding step in which the winding is performed The winding shaft is relatively slid back and forth in the width direction of the film around the front film; and in the sliding step, when the distance of one half of the distance at which the winding shaft is moved back and forth is set to an amplitude, The thickness of one half of the predetermined thickness is increased until the average value of the amplitude between the film is wound up to the predetermined thickness, and is smaller than when the film is wound around the winding axis until the film is wound. The relative sliding amount of the winding shaft with respect to the film immediately before winding, that is, the relative sliding amount, is controlled so as to average the amplitude between the thicknesses of the half of the predetermined thickness. The film winding method according to claim 3, wherein the sliding step is performed from a time when the film is wound around the winding shaft until the film is wound up to the predetermined thickness. In a decreasing manner, the above relative sliding amount is controlled. A film manufacturing method for producing a film with a coating film, comprising: a step of coating a coating liquid on a long support; and drying the applied coating liquid to form a film with a coating film And a step of winding the film with the coating film described above by a film winding method according to any one of claims 1 to 4. A method of manufacturing a polarizing plate on at least one side of a polarizing element A method for producing a polarizing plate to which a protective film is bonded, and comprising: a winding step of winding the protective film into a film winding method according to any one of claims 1 to 4 Rolling; bonding step, unwinding the wound protective film, and bonding the developed protective film to at least one side of the polarizing element; and cutting step of bonding the polarizing element with the protective film Cut to the specified size.