JP2010254439A - Film roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film roll for reducing revolving strain caused by the thickness step of a winding core, in the roll of winding an extra thick film, particularly a film having a thickness exceeding 188 μm on a core. <P>SOLUTION: This film roll satisfies a specific related expression in an angle (θ) formed by a winding starting end surface and the film plane of the film contacting with the core, through a method such as cutting with a sharp cutter, by fixing the angle between the film plane of a cutting place of the film and the cutter to a specific range in a state of heating the winding starting end of the film contacting with the core to the temperature of a glass transition point or more of a film material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a film wound up in a roll shape. In particular, the present invention relates to a film roll suitable for an optical film used as a member of a liquid crystal display or a plasma panel.

Biaxially stretched polyester films are widely used as prism sheets and light diffusion films for liquid crystal displays, top sheets of plasma displays and substrates for optical filters. Since the polyester film used as these base materials is required to have excellent flatness over a wide area, a thick film having a strong waist is used. Although the thickness of the polyester film used for said use changes with display areas and display methods, it is about 25 micrometers-188 micrometers. However, with the recent increase in size and thickness of flat panel displays, thicker films are required.
These films are usually wound in a cylindrical core in units of several hundreds of meters to several thousands of meters and shipped as film rolls. However, as the film thickness increases, the step difference in film thickness at the winding end of the innermost film in contact with the core (hereinafter, also simply referred to as the thickness difference in the winding core) increases. For this reason, a circumferential distortion due to a step difference in film thickness occurs in the film wound around and wound on the film. This distortion is a fatal defect for a display film. The circular distortion generated in this way tends to become smaller as the circuit is overlapped on the core (the longer the winding length is), but the part where the distortion can be visually recognized is used as a product. This is not possible, and the yield decreases. Therefore, a method that can easily solve this problem is desired.

  Patent Documents 1 and 2 disclose a method in which a knurling process is performed on an end portion in the width direction of a film over a length of not less than twice the outer periphery of the core and not more than 10% of the total film winding length. ing. However, since the pressure applied from the film wound around the outer periphery accumulates in the film roll, an extremely high pressure is applied. Therefore, even if a knurling process of several turns is applied to the end portion in the film width direction, the effect is limited. In particular, when the thickness of the film exceeds 188 μm or the width of the film roll exceeds 1000 mm, the effect is not so much exhibited. Moreover, even if it appears that the circumferential distortion has disappeared, the distortion remains in the vicinity of the center at a long distance from the winding core.

Moreover, in patent document 3, in order to suppress the generation | occurrence | production of the circumferential distortion by a level | step difference by reducing the film thickness level | step difference of the film | membrane end of the innermost layer film which contacts a core, A film roll having a width of 1 m and a length of 1000 m, in which a winding end of a polyester film having a thickness of 100 μm is cut obliquely with a cutter and wound, is disclosed as an example. Illustrated.
However, thicker films, particularly biaxially stretched polyester films with a thickness exceeding 188 μm, have properties that are very easy to cleave. For this reason, it has been difficult to obtain a smooth end face by a normal method. As a result, a large variation in the angle of the end face occurred, and the thickness step of the winding core could not be essentially solved. Even if it appears that the circumferential distortion has disappeared, the distortion remains partially at a long distance from the core. Further, in a film used for a large display or the like, even a slight distortion is greatly affected.
As described above, in the ultra-thick film, in particular, the biaxially stretched film having a thickness exceeding 188 μm, it is extremely difficult to eliminate the circular distortion due to the thickness difference in the winding core.

JP 2005-290332 A JP 2005-298196 A JP-A-9-315637

  An object of the present invention is to eliminate the circular distortion due to the step difference in the thickness of the film winding start end portion of the winding core portion in a roll obtained by winding an ultra-thick film, particularly a film having a thickness exceeding 188 μm around the core.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention. That is, this invention consists of the following structures.
1. A film roll in which a film is wound on a core, the thickness of the film is in the range of 25 to 1000 μm, and the angle (θ) formed between the winding start end surface of the film contacting the core and the film plane is expressed by the following relational expression ( 1) A film roll characterized by satisfying (2).
0.05 ≦ AV (tan θ) ≦ 1.0 (1)
SD (tan θ) / AV (tan θ) <0.2 (2)
Here, AV (tan θ) is an average value of tan θ measured over the entire width of the film roll, and SD (tan θ) is a standard deviation of tan θ measured over the entire width of the film roll.
2. 2. The film roll as described in 1 above, wherein the thickness of the film exceeds 188 μm.
3. 3. The film roll as described in 1 or 2 above, wherein the roll width exceeds 1000 mm.
4). The film roll as defined in 1 above, wherein the haze of the film is 5% or less, from the vicinity of the core to more than twice the outer periphery of the core and 10% or less of the total film winding length, A film roll characterized in that an uneven portion is present on at least one surface in the vicinity of the end portion in the width direction.
5). When manufacturing a film roll in which a film is wound on a core, the film plane and the blade at the cut position of the film are heated while the winding start end of the film in contact with the core is heated to a temperature equal to or higher than the glass transition point of the film material. The film roll is fixed to a range satisfying the following relational expression (3) and cut with a sharp blade.
0.05 ≦ tan α ≦ 1.0 (3)

  The film roll of the present invention has a small circular distortion due to the thickness difference of the core part, and can be used effectively up to the core side of the core. In particular, there is almost no local distortion due to angle fluctuation of the cut surface, and it can be suitably used as an optical film for a large screen display in which a slight distortion is greatly affected. Easy to perform and efficient production becomes possible.

Conceptual diagram of the angle between the film and the blade Schematic diagram of film cutting blade jig (pillow type) Schematic diagram of film cutting tool jig (guide type) Cross section of film cutting fixture (slope base) Cross section of (Circle base) of fixing bracket for film cutting Explanatory drawing of tan θ measurement (in case of smooth cut surface) Illustration of tan θ measurement (when there is cleavage)

The present invention is a film roll in which a film is wound on a core, the thickness of the film is in the range of 25 to 1000 μm, and the angle (θ) formed by the winding start end surface of the film contacting the core and the film plane is as follows: These film rolls satisfy the following relational expressions (1) and (2).
0.05 ≦ AV (tan θ) ≦ 1.0 (1)
SD (tan θ) / AV (tan θ) <0.2 (2)
Here, AV (tan θ) is an average value of tan θ measured over the entire width of the film roll, and SD (tan θ) is a standard deviation of tan θ measured over the entire width of the film roll.

Hereinafter, the present invention will be described in more detail.
<Type of film>
The film roll of the present invention is applicable to various plastic films. In particular, the effect is exhibited in a film used for an optical application that requires transparency. For example, the present invention can be applied to polyester films, polycarbonate films, cellulose triacetate films, cycloolefin films, polystyrene films, acrylic films, polyimide films, polyamide films, polyolefin films, and the like. The film may be unstretched, uniaxially stretched, or biaxially stretched. In particular, in the case of a biaxially stretched polyester film, the present invention can provide an excellent effect. The biaxially stretched polyester film is most preferably a film made of polyethylene terephthalate having a terephthalic acid unit of 90 mol% or more with respect to the dicarboxylic acid component and an ethylene glycol unit of 90 mol% or more with respect to the previous glycol component.
The haze of the film is preferably 5% or less. More preferably, it is 4% or less, More preferably, it is 3% or less. The lower limit of haze is practically 0.1%.
If the haze exceeds 5%, it may cause problems such as a decrease in transparency and a decrease in sharpness when used in an optical film which is a preferred application of the present invention.

The effect of the present invention is exhibited when the thickness of the film is in the range of 25 to 1000 μm. In particular, when the thickness exceeds 188 μm, the effect of the present invention is exhibited to the maximum, which is preferable. The more preferable thickness of the film to which the present invention is applied is 200 μm or more, and more preferably 230 μm or more. The upper limit of the thickness of the film is more preferably 700 μm or less, and further preferably 500 μm or less.
The length of the film is preferably adapted to a length of 200 m or more. Further, it is preferably 300 m or more, particularly 400 m or more. In a film having a length of less than 200 m, the upper limit of the film length is preferably 10,000 m or less, more preferably 5000 m or less.

The width of the film roll is arbitrary, but is usually 650 mm or more. Furthermore, when exceeding 1000 mm, the effect of this invention is exhibited to the maximum, and it is especially preferable. The most preferable roll width is 1050 mm or more. The upper limit of the roll width is preferably 10,000 mm.
The film may be subjected to various processes such as an easy adhesion coat and an easy slip coat, and may be a multilayer film having two or more layers.

<Core>
The core for winding the film is not particularly limited and is arbitrary. For example, a core made of paper, resin-impregnated paper, plastic, glass epoxy, or metal can be used.
The outer diameter of the core is preferably 90 mm or more, and more preferably 160 mm or more. When the core has an outer diameter of less than 90 mm, curling in the wound inner portion of the wound film is increased, and workability in the next processing step is deteriorated. The outer diameter of the core is preferably 350 mm or less. Beyond this, the length of the circular distortion that cannot be used becomes too long and the loss increases.

<End face angle>
The angle (θ) formed between the winding start end face of the film in contact with the core and the film plane is
The relationship 0.05 ≦ AV (tan θ) ≦ 1.0 must be satisfied. Here, AV (tan θ) is an average value of tan θ measured over the entire width of the film roll. The average value of the angle θ calculated backward from the above relationship is about 3 degrees to 45 degrees. If the angle is more obtuse than this range, it may be difficult to sufficiently reduce the circular distortion due to the step of the thickness of the film winding start end of the core (hereinafter also referred to as the thickness step of the core). (Incidentally, the angle (θ) between the winding start end face and the film plane is the angle seen from the film width direction when the cut end face extends in the film width direction, and extends in a curved or zigzag shape. Or, if it extends diagonally with respect to the film width direction, it is the angle seen from the direction parallel to the cut surface of that part)
The lower limit of AV (tan θ) is preferably 0.1 (5.7 degrees), more preferably 0.2 (11.3 degrees), and further preferably 0.25 (14.0 degrees). The upper limit is preferably 0.7 (35 degrees), more preferably 0.6 (31 degrees), and even more preferably 0.5 (26.6 degrees).
Further, SD (tan θ) / AV (tan θ) <0.2.
SD (tan θ) is a standard deviation of tan θ measured over the entire width of the film roll. SD (tan θ) / AV (tan θ) is preferably less than 0.10, and more preferably less than 0.05. When SD (tan θ) / AV (tan θ) exceeds 0.2, even if the thickness difference in the core portion appears to disappear, distortion may partially remain and cause spots. The lower limit of SD (tan θ) / AV (tan θ) is zero.

  Further, it is preferable that there is no point where tan θ exceeds AV (tan θ) +0.25, more preferably there is no point where AV (tan θ) +0.2 exists, and further, a point where AV (tan θ) +0.15 is exceeded. Is preferably absent. In addition, it is preferable that there is no point where tan θ exceeds 0.6.

<Film production method>
An example of the method for producing the film roll of the present invention will be described using polyethylene terephthalate as an example. A raw material of polyethylene terephthalate is melt-extruded on a chill roll with an extruder and cooled to prepare an unstretched sheet. Next, this is heated to glass transition temperature + 10-50 degreeC, and is extended | stretched to a longitudinal direction and the width direction. The stretching ratio is usually in the range of 3 to 6 times in the longitudinal direction and 3 to 4.5 times in the width direction. Further, this may be re-longitudinal stretched or re-laterally stretched. Even better. Then, it heat-processes by 190 degreeC-below melting | fusing point with a tenter, the polyester film of thickness within the range of 25-1000 micrometers is made, for example, it winds up as a jumbo roll.
This is slit into a predetermined width and length with a slitter to form a film roll, which is used for the next processing.

<Preferred method for producing film roll>
In the present invention, when the film roll is manufactured by slitting, the angle (θ) formed between the winding start end face of the film contacting the core and the film plane satisfies the following relational expressions (1) and (2). Process.
0.05 ≦ AV (tan θ) ≦ 1.0 (1)
SD (tan θ) / AV (tan θ) <0.2 (2)
The method is not limited as long as the relational expressions (1) and (2) are satisfied. After cutting to 90 degrees with respect to the core surface, scraping with a grinder so that there are no angular spots, a method of stretching the film while heating it above the temperature at which the film material flows, and cutting with a sharp blade And a method of cutting in the horizontal direction.
Among these, the method of cutting in the transverse direction with an angle with a sharp blade is preferred for simplicity, but usually a biaxially stretched polyester film of hundreds of μm or more is cut with the blade with an angle in the lateral direction. When trying to do so, it had a cleaving property, so that it was not cut smoothly, the cut surface was stepped, the position where the blade edge hits the front and back surfaces of the film was not determined, and the cut surface was susceptible to uneven spots.

<Temperature adjustment during cutting>
However, the present inventors have found that, when cutting, by heating to a temperature equal to or higher than Tg of the material constituting the film, it can be easily cut without cleavage at a certain angle.
The film temperature during cutting is preferably Tg + 5 ° C. or higher, and more preferably Tg + 10 ° C. or higher. The film temperature needs to be equal to or lower than the melting point of the material constituting the film, more preferably Tg + 100 ° C. or lower, and further preferably Tg + 80 ° C. or lower.
Examples of means for heating the film include heating with hot air, heating with an infrared heater, heating rolls and heating plates, immersion in hot water and heating oil, and the like.

<Fixing the blade during cutting>
When cutting, the angle α formed when the film plane and the blade span direction of the blade are viewed from the direction of travel of the blade is fixed so that 0.05 ≦ tan α ≦ 1.0. The term "fixed" as used herein means that the cutter is not cut while changing the angle of the blade within the range of the above formula, but is cut at an angle within a certain point within the above range. It is not necessarily a thing that physically fixes with a screw or the like.
Further, the blade may be bent or curved, and in that case, the contact point between one surface of the film and the blade edge (A (the contact point at the forefront of the film, the acute angle side) ) And the other surface (B (obtuse angle side)) of the film and the contact point of the blade edge is referred to as the blade crossing direction.

The lower limit of tan α is preferably 0.1 (5.7 degrees), more preferably 0.2 (11.3 degrees), and still more preferably 0.25 (14.0 degrees). The upper limit is preferably 0.7 (35 degrees), more preferably 0.6 (31 degrees), and even more preferably 0.5 (26.6 degrees).
At this time, it is preferable that the blade span direction of the blade has an angle with respect to the length direction of the film when viewed from the plane direction of the film. This angle is preferably 10 to 70 degrees.

When cutting the film, after the film is borrowed to the core, it is wound up slightly, and a blade is inserted between the core and the film to cut it, and the film is borrowed to the core and other parts and tension is applied to the film. Examples include a method of cutting in the air and a method of cutting a film on a cutting table.
In order to cut the blade at an angle within a certain range within the above range, the blade may be cut by hand while paying attention to the angle between the blade and the film, but a cutter or a guide may be attached to the blade.
Furthermore, there are a method of cutting the film by fixing it to an angled fixing bracket, a method of fixing the film to an arcuate base and scraping it off.
The blade is not limited as long as it is a sharp object such as a razor, a knife, or a cutter knife.

  In this way, the film having the oblique cut surface is wound around the core while slitting. The cut surface that is slanted when starting to be wound around the core may be located outside or inside. When wrapping around the core, the core and the film are attached using a single-sided or double-sided adhesive tape, adhesive, adhesive, water, or other liquid.

<Knurling>
Furthermore, in this invention, it is preferable that an uneven | corrugated | grooved part exists in the at least single side | surface near the width direction edge part of a film over the length of 10% or less of the total film winding length from 2 times or more of the core outer periphery. By such a knurling process, it is possible to more effectively reduce the circular distortion.
The concavo-convex portion is preferably 5 times or more the length of the outer periphery of the core, more preferably 10 times or more, and particularly preferably 15 times or more. Further, it is more preferably 8% or less of the total film length.
If it is less than twice the outer circumference of the core, the effect of reducing the circular distortion may be insufficient. On the other hand, even if the length of the concavo-convex formation exceeds 10% of the total length of the film, the effect is not only saturated, but the roll diameter of the roll may become too large. 100 times or less of the core outer periphery is preferable, and 70 times or less is more preferable.

  The concavo-convex portion is formed in the vicinity of the end portion in the width direction of the film. Here, the vicinity means, for example, a portion within 20 mm, preferably within 10 mm from the end of the film. If the concavo-convex portion is formed not in the vicinity of the end portion of the film but inside, the usable range of the film as a product is narrowed, and the efficiency of use is significantly reduced. Moreover, although the uneven | corrugated | grooved part will be formed in strip | belt shape, the width | variety is 3 mm or more normally, Preferably it is 5 mm or more, and is 20 mm or less normally, Preferably it is 10 mm or less. When the width of the concavo-convex part is 3 mm or less, the influence of the thickness step of the film core part of the present invention may not be suppressed. On the other hand, even if it exceeds 20 mm, the effect does not increase, and the usable range of the film becomes narrow.

The height of the concavo-convex convex portion is usually 3% or more, preferably 5% or more, more preferably 7% or more, and usually 30% or less, preferably 20% or less, more preferably 15% of the thickness of the film. It is as follows. If the height of the convex portion is less than 3% of the film thickness, the effect of reducing the circular distortion may be insufficient. On the other hand, when the thickness exceeds 30%, problems such as wrinkling of the film and generation of foreign matter may occur. Note that the height of the unevenness can be obtained by measuring the thickness of the portion subjected to the unevenness forming process and the thickness of the unprocessed portion with a surface contact type thickness meter.
The unevenness may be on the inside of the winding, on the outside of the winding, or on both sides.

  The method of providing the concavo-convex portion in the vicinity of the film edge and the shape of the concavo-convex portion are not particularly limited, and a known method can be adopted, but it is preferably formed by pressing a knurled (roughened surface) roll. The shape of the knurling process is not particularly limited, and examples thereof include a twill shape and an emboss ring shape. In the case of a cross-hair shape, the intersection of the oblique lines forms a convex portion on the film. That is, in this method, a flaw pattern is formed in the vicinity of the film end portion by knurling with knurling, and the thickness in the vicinity of the end portion is slightly increased by the flaw pattern.

  Forming irregularities (knurling or embossing) by pressing a knurled roll (knurling roll) is a method of providing a heating means such as an electric heater inside the knurling roll, a method of heating a film by dielectric heating, film production Examples include a method in which the heat of the heat treatment zone in the process is used and the film is pressed while the temperature of the film is high.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples. The film and roll properties were measured by the following methods.
(1) Total light transmittance, haze In accordance with JIS K 7105 “Testing methods for optical properties of plastics” haze (cloudiness value), NDH-300A turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. The total light transmittance was measured.

(2) tan θ
The winding end of the film in contact with the core was observed with a digital microscope (VH-7000, manufactured by KEYENCE), and the length (L) in the film plane direction was measured. Further, the film thickness (t) was measured using a Sony thickness gauge (μ-mate), and the value of t / L was defined as tan θ (FIG. 6). In addition, when a cleavage is seen in a cut surface, the length of the plane direction of the cutting start point of a film front and back becomes L (FIG. 7).
(3) AV (tan θ), SD (tan θ)
The tan θ was measured by the method of (2) at 15 locations almost evenly in the film width direction, and the average value and standard deviation were obtained. The measurement position at the left and right ends in the width direction was a position 2 cm from the end when the knurling was not performed, and a position 2 cm inside from the knurling when the knurling was performed.

(4) Naral height Using a Sony thickness gauge, the thickness of the knurled part (thickness including irregularities) and the thickness of the non-knalled part were measured, and the difference was defined as the knurled height. At the left and right knurls, five points were measured at approximately equal intervals in the length of two rounds from the beginning of the core winding of the film, and the average value was obtained.

(5) Observation of differential strain After the film roll was stored at 40 ° C. for 1 month, the film was once rewound onto another core until the core was wound, and the core of the original roll was unwound from the rewound roll. A sample having a length of 1 m was cut out from the sample and a sample of 1 m in length was cut out.
For evaluation, a strain observation plate irradiated with fluorescent light from the back side was set up, and the sample film was placed on a flat table in front of the strain observation plate so that the length direction was parallel to the observation plate. The reflection image of the observation board reflected on the film was observed from the front direction and the oblique 30 degree direction.
The observation plate is an object obtained by irradiating light from a back surface with a fluorescent lamp onto a polished glass of 100 cm × 100 cm into which a black line having a width of 10 cm is put in parallel at 10 cm intervals.
X: Step distortion is recognized in the entire film width direction (unusable)
Δ: There is no step distortion, but distortion or waviness is observed in a part of the film (unusable)
○: Looks parallel (can be used)

(6) Observation of cut surface The degree of cleavage of the cut surface at the winding end of the film contacting the core and the occurrence of burrs were observed with a 10-fold magnifier.
X: Large delamination was observed in many places, and burr-like places were also observed.
(Triangle | delta): Although delamination was seen in many places, it was a small thing. .
○: Small delamination was observed in some places.
A: Delamination was not observed and the end face was very smooth.

(7) Surface temperature of film Measured using a heat label manufactured by Micron Corporation.
(8) Glass transition temperature of film material 10 mg of a sample was cut out from the film, put in an aluminum pan, covered, and measured by DSC. The measurement conditions were that the temperature was once raised to 280 ° C., held for 5 minutes, then rapidly cooled, and then measured at a rate of temperature increase of 20 ° C./min. DSC was a DSC 6220 type differential scanning calorimeter manufactured by SII Nano Technology.

[Example 1]
A Toyobo biaxially stretched polyester film A4300 (thickness 250 μm, haze 0.9%, product width 1350 mm, roll length 1400 m, plastic core with a diameter of 17.2 cm, glass transition temperature 68 ° C.) was wound back using a slitter. At that time, a plastic core having a diameter of 17.2 cm was used as the winding core, and the winding length was 1050 m.
When the film is wound around the core, the end portion is first borrowed on the plastic core with an adhesive tape, and then the film is wound around the core at about 180 degrees, and hot air is applied to the entire width of the portion to be cut so that the film temperature is 75. After confirming that the temperature was 0 ° C., the cutting edge of a cutter knife (A-1P manufactured by NT Corporation) was inserted between the film and the core and cut. The cutter knife is provided with a macula and is set so that tan α is 0.34 when the blade edge is applied to the roll and the blade crossing direction is 45 degrees with respect to the film length direction when viewed from the plane direction of the film. Has been. Furthermore, the temporary fixing part of the separated film is peeled off from the core and discarded, and the end part which has been cut diagonally is renewed with a double-sided tape (manufactured by Nitto Denko) with a thickness of 10 μm on the core. Pasted and rolled up. The wound film roll was allowed to stand for 1 month in an environment of 40 ° C. and 60% RH, and then various evaluations were performed.

[Example 2]
It carried out similarly to Example 1 except having heated the temperature of a cutting location to 90 degreeC.
Example 3
The film was passed through a knurled roll, and a knurling process with a height of 25 μm and a length of 25 m from the winding core was applied to the inner side of the film from both ends to a position of 10 mm in width. I went.

Example 4
It carried out like Example 1 except having carried out at room temperature, without heating at the time of a cutting | disconnection.
Example 5
The same procedure as in Example 1 was performed except that the cutting method was as follows.
The entire film width at a position about 20 cm away from the contact point between the core and the film was heated to 90 ° C. using an infrared heater, and the film was immediately cut. For the cutting, a cutter knife having a guide having a tan α of 0.35 was used (jig C).

Example 6
The same procedure as in Example 2 was performed except that a cutter was not provided on the cutter knife at the time of cutting and the arm was cut so that the angle of the arm was not shaken.
Example 7
Cutting was performed in the same manner as in Example 6. However, the same knurling process as in Example 3 was performed.

Example 8
The same operation as in Example 2 was performed except that the film had a thickness of 350 μm and the winding length was 750 m. However, the height of the jig of the jig was adjusted (jig B).
Example 9
A film having a thickness of 350 μm was cut in the same manner as in Example 5. However, the same knurling process as in Example 3 was performed. The winding length was 750 m.
Example 10
The same operation as in Example 6 was performed except that the thickness of the film was 350 μm and the winding length was 750 m.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that heating was not performed during cutting and the cutter knife was held by hand. The x region was slightly longer than the example, but the Δ region remained long and was difficult to use because the stress was concentrated.
[Comparative Example 2]
The same procedure as in Comparative Example 1 was performed except that the thickness of the film was 350 μm and the winding length was 750 m. The x region was slightly longer than the example, but the Δ region remained long and was difficult to use because the stress was concentrated.

[Comparative Example 3]
Although it was the same as that of the comparative example 2, in the case of a cutting | disconnection, it cut | disconnected so that the cutter knife might become an angle of about 90 degree | times with respect to a film plane. Also, knurling was performed in the same manner as in Example 3. The distortion at the center did not disappear, and the X region continued for a long time.
Tables 1 and 2 show the production conditions and evaluation results of the film rolls of Examples and Comparative Examples.

  The film roll of the present invention has a small circular distortion due to the thickness difference of the core part, and can be used effectively up to the core side of the core. In particular, there is almost no local distortion due to angle fluctuation of the cut surface, etc., and it can be suitably used as an optical film for a large screen display in which a slight distortion is greatly affected. Easy to perform and efficient production becomes possible.

Claims (5)

A film roll in which a film is wound on a core, the thickness of the film is in the range of 25 to 1000 μm, and the angle (θ) formed between the winding start end surface of the film contacting the core and the film plane is expressed by the following relational expression ( 1) A film roll characterized by satisfying (2).
0.05 ≦ AV (tan θ) ≦ 1.0 (1)
SD (tan θ) / AV (tan θ) <0.2 (2)
Here, AV (tan θ) is an average value of tan θ measured over the entire width of the film roll, and SD (tan θ) is a standard deviation of tan θ measured over the entire width of the film roll.   The film roll according to claim 1, wherein the thickness of the film exceeds 188 μm.   The film roll according to claim 1 or 2, wherein a roll width exceeds 1000 mm.   The film roll as defined in claim 1, wherein the film has a haze of 5% or less, from the vicinity of the core to more than twice the outer periphery of the core and a length of 10% or less of the total film winding length. A film roll characterized in that an uneven portion is present on at least one surface in the vicinity of the end in the width direction. When manufacturing a film roll in which a film is wound on a core, the film flat surface and the blade at the cutting point of the film are heated in a state where the winding start end of the film contacting the core is heated to a temperature equal to or higher than the glass transition point of the film material. The film roll is fixed to a range satisfying the following relational expression (3) and cut with a sharp blade.
0.05 ≦ tan α ≦ 1.0 (3)

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