JP2023173151A - Film roll, method for manufacture thereof, polarizer, and display device - Google Patents

Abstract

To provide a film roll in which tape transfer marks do not remain and there is no chain-shaped film deformation due to air leakage during long-term storage, and a method for manufacture of the same, a polarizer, and a display device.SOLUTION: In a film roll with no knurling processing part, when a thickness of a void layer between films adjacent to each other at a winding core peripheral part that is measured at a width direction side part is represented by X[μm], and a thickness of a void layer between films adjacent to each other at a winding outer peripheral part is represented by Y[μm], X and Y satisfy the following formula (1): Y<X.SELECTED DRAWING: Figure 1

Description

The present invention relates to a film roll, a method for manufacturing the same, a polarizing plate, and a display device. More specifically, the present invention relates to a film roll that does not leave tape transfer marks and does not undergo chain-like film deformation due to air leakage during long-term storage.

In recent years, with the fierce price competition of LCD televisions, polarizing plate manufacturers are considering cost reduction measures such as reducing switching loss, and in response to this, the length of the films used in polarizing plates has been increasing.

By increasing the length of the film, cost reductions can be expected in various aspects such as splicing loss, inspection man-hours, transportation, and auxiliary materials.The film is usually rolled into rolls after being manufactured for convenience in storage and transportation. It is wound up.

However, especially when a long film roll is stored for a long period of time, when the film is unwound, tape transfer marks are left due to the films sticking together (hereinafter also referred to as "tape transfer"). There is a problem in that chain-like film deformation (hereinafter also referred to as "chain-like deformation") occurs due to air leakage.

Here, the above-mentioned "chain-like deformation" refers to film deformation (chain-like defect) caused by stress due to the film's own weight after winding and stress that tends to extend in the width direction of the film.

A possible solution to the above problem is to wind the film together with the protection film, but there is a problem that the protection film becomes waste.

One way to solve the above problem without producing waste is to knurling the edges of the film in advance, and by introducing air between the film during winding, a void layer of appropriate thickness ("air layer") is created. ) to prevent the films from sticking to each other.
However, the above knurling method has a problem in that it is less effective in suppressing sticking than the method of winding the protective film together.

In addition, by using the above method, the closer the film roll is to the core, the greater the pressure applied to the surface of the film, making it easier for air to escape between the films, making the void layer thinner. There are problems with tape transfer marks caused by films wound close to each other sticking together, and chain-like deformation caused by air leakage between the films when a film roll is stored for a long period of time.

In Patent Document 1, when winding a film, the amount of air taken in between the films is kept constant by changing the winding tension and the height of the knurling at the film end in accordance with the winding diameter of the film roll. However, there is still room for improvement in order to solve the above problems.

Note that in this specification, the term "void layer" refers to a layer formed by a gap between opposing surfaces of adjacent films in a film roll, and is a layer formed by air or other substances other than air (for example, inert gas, etc.). A layer in which gases (gases) can exist. Strictly speaking, the layer composed of air in this "void layer" is called the "air layer," but if not distinguishing between the two does not particularly affect the present invention, the "air layer" is referred to as the "void layer." It shall be written as "layer".
In addition, a form in which adjacent films have microscopic convexities unique to the surface of one film that contact the surface of the other film in some places is also a form of void layer. . Note that the present invention does not include a void layer formed by knurls (uneven shapes) artificially imparted to the film by knurling processing.

JP2013-46966A

The present invention was made in view of the above-mentioned problems and circumstances, and the objects to be solved are: a film roll that does not leave tape transfer marks and no chain-like film deformation due to air leakage during long-term storage, a method for manufacturing the same, An object of the present invention is to provide a polarizing plate and a display device.

In order to solve the above problem, the inventors of the present invention have investigated the causes of the above problem, etc., and have determined that the thickness of the void layer between the films around the winding core is reduced by not applying knurling to the film roll, and reducing the thickness of the void layer between the films around the winding core. It was discovered that the above-mentioned problem could be solved by making the thickness thicker than the void layer, leading to the present invention.
That is, the above-mentioned problems related to the present invention are solved by the following means.

1. A film roll that does not have a knurling part, and the thickness of the void layer between adjacent films around the winding core, measured at the side surface in the width direction of the film roll, is defined as X [μm], A film roll characterized in that the X and Y satisfy the following formula (1), where the thickness of the void layer between adjacent films at the outer periphery of the roll is Y [μm].

Formula (1): Y<X

2. The film roll according to item 1, wherein the X [μm] and the Y [μm] satisfy the following formula (2) and the following formula (3).

Formula (2): 0.05<Y<0.50
Formula (3): 1<(X/Y)<3

3. A film roll manufacturing method for manufacturing a film roll without a knurling part, wherein the gap layer between adjacent films around the winding core is measured at a widthwise side surface of the film roll. When the thickness is X [μm] and the thickness of the void layer between adjacent films at the outer periphery of the winding is Y [μm], the X and Y satisfy the relationship of the following formula (1). A method for manufacturing a film roll, characterized by adjusting the film roll as follows.

Formula (1): Y<X

4. 4. The method for manufacturing a film roll according to item 3, wherein the X [μm] and the Y [μm] are adjusted so as to satisfy the following formula (2) and the following formula (3).

Formula (2): 0.05<Y<0.50
Formula (3): 1<(X/Y)<3

5. The film touch pressure at the periphery of the winding core is within the range of 2 to 30 [N/m], the film touch pressure at the center of the winding is within the range of 3 to 40 [N/m], and the film at the outer periphery of the winding. The method for manufacturing a film roll according to item 3 or 4, characterized in that the touch pressure is adjusted within a range of 5 to 55 [N/m].
6. A polarizing plate comprising a part of the film of the film roll according to item 1 or 2.

7. A display device comprising a part of the film of the film roll according to item 1 or 2.

By means of the above means of the present invention, it is possible to provide a film roll, a manufacturing method thereof, a polarizing plate, and a display device that do not leave tape transfer marks and do not undergo chain-like film deformation due to air leakage during long-term storage.
Although the mechanism of expression or action of the effects of the present invention is not clear, it is speculated as follows.

The film roll of the present invention is not subjected to knurling processing, and by making the thickness of the void layer between the films around the core thicker than the thickness of the void layer around the outer periphery of the roll, tape transfer due to the sticking of the films to each other is achieved. It is possible to prevent chain-like film deformation (hereinafter also referred to as "chain-like deformation") due to air leakage between films without leaving any traces.

As mentioned above, the above-mentioned "chain-like deformation" refers to film deformation (chain-like defects) caused by stress due to the film's own weight after winding and stress that tends to extend in the width direction of the film. It is.

As in the past, when a film roll is subjected to a knurling process to increase the amount of air taken in between the films, the void layer between the films becomes thicker than when the process is not performed.
During long-term storage of film rolls, radial stress is applied to the film closer to the core due to the film's own weight, and especially when a small impact occurs on the film roll, larger radial stress is applied to the film roll. .

When stress is applied to the film in the radial direction, the air between the films escapes, so knurling film rolls have a larger change in the thickness of the void layer near the core than normal film rolls. As a result, sticking of the films to each other tends to occur particularly at the core portion, and many tape transfer marks due to the adhesion of the films to each other remain at the core portion.

In addition, in a knurled film roll, the film is supported only by the knurled part, so the regulating force to prevent roll shift is applied to the knurled part, which causes uneven stress on the film. In this case, the amount of air leakage between the films becomes uneven, and the thickness of the void layer becomes uneven, so that chain-like deformation is likely to occur during long-term storage.

On the other hand, the film roll of the present invention does not have a knurled part, and the film is supported by the entire film, including the minute contact surfaces between the films or the gas (e.g., air) in the void layer, so that winding misalignment occurs. The regulating force to prevent this is not biased, and the stress applied to the film is uniform.

To explain in more detail, although the film roll of the present invention is not knurled, the film surface usually has voids consisting of nanometer-sized fine irregularities unique to the film, so that adjacent films When a large number of convex portions on opposing surfaces of the film are in contact with the other surface at some places, the film may be supported by the entire minute contact surfaces of the convex portions.

That is, for example, because some of the convex parts are in contact, the films are supported not only by the void layer, for example, the air layer, but also by multiple contact points due to the minute irregularities. There are cases like this.

In addition, by making the void layer thicker at the winding core to take in an appropriate amount of air, even if more air escapes from the winding core during long-term storage of the film roll, the entire film roll will remain intact. By suppressing the deviation in the thickness of the void layer and forming a void layer of uniform thickness between the films, there is no trace of tape transfer when the film of the film roll is unwound, and chain-like deformation is avoided. It is presumed that there is no.

Schematic diagram showing the positional relationship between the widthwise side surface of the film roll and the imaging device A schematic diagram of the widthwise side surface of a film roll viewed from a plane perpendicular to the side surface. Processed image for calculating the thickness of the void layer A simplified conceptual diagram of a part of the widthwise side surface of the film roll for explaining the core periphery, the center of the roll, and the outer periphery of the roll. Schematic diagram of the internal configuration of the imaging unit Schematic diagram of the system configuration of the imaging device Flowchart showing the flow of the manufacturing process of the solution casting film forming method Schematic diagram of equipment for manufacturing film by solution casting method A plan view schematically showing the internal configuration of a tenter stretching device. Plan view showing the tenter stretching device with the cover removed Schematic diagram of the nozzle and heater installation area when looking from the front of the three zones inside the tenter stretching device Side view of the three zones within the tenter drawing device Schematic diagram showing the process of winding the film and the cross section of the film roll of the present invention after being wound up Flowchart showing the flow of the manufacturing process of melt casting film forming method Schematic diagram of equipment for manufacturing film by melt casting film forming method A schematic diagram showing an example of the configuration of a liquid crystal display device of the present invention

The film roll of the present invention is a film roll that does not have a knurling part, and the thickness of the void layer between adjacent films around the winding core is measured at the side surface in the width direction of the film roll. is defined as X [μm], and the thickness of the void layer between adjacent films at the outer periphery of the winding is defined as Y [μm]. shall be.
The above features can solve the problems of the present invention.

Further, the method for manufacturing a film roll of the present invention is a method for manufacturing a film roll for manufacturing a film roll having no knurling processing portion, wherein the film roll is measured at a side surface in the width direction of the film roll. When the thickness of the void layer between adjacent films in the peripheral part is X [μm], and the thickness of the void layer between adjacent films in the outer peripheral part of the winding is Y [μm], the above-mentioned X and It is characterized in that the Y is adjusted so as to satisfy the relationship of the formula (1).
The above two features are technical features common to or corresponding to each of the embodiments (aspects) described below.

In an embodiment of the present invention, it is preferable that the above-mentioned X [μm] and the above-mentioned Y [μm] satisfy the above-mentioned formula (2) and the above-mentioned formula (3) from the viewpoint of uniform void layer formation during long-term storage.

It is preferable to adjust the X [μm] and the Y [μm] so that they satisfy the formulas (2) and (3) from the viewpoint of forming a uniform void layer during long-term storage.

The film touch pressure at the periphery of the winding core is within the range of 2 to 30 [N/m], the film touch pressure at the center of the winding is within the range of 3 to 40 [N/m], and the film at the outer periphery of the winding. It is preferable to adjust the touch pressure within the range of 5 to 55 [N/m] from the viewpoint of forming a uniform void layer during long-term storage.

A part of the film of the film roll of the present invention can be suitably used by being included in a polarizing plate.

A part of the film of the film roll of the present invention can be suitably used by being included in a display device.

Hereinafter, the present invention, its constituent elements, and forms and aspects for carrying out the present invention will be described in detail. In this application, "~" is used to include the numerical values described before and after it as a lower limit value and an upper limit value.

1. Film roll (1.1) Overview of the film roll The film roll of the present invention is a film roll that does not have a knurling part, and the film roll has a core peripheral area measured at a widthwise side surface of the film roll. When the thickness of the void layer between adjacent films is X [μm], and the thickness of the void layer between adjacent films at the outer periphery of the winding is Y [μm], the above X and the above Y are as follows. It is characterized by satisfying the relationship of formula (1).

Formula (1): Y<X

The film roll of the present invention (the term "film roll" refers to a film wound into a roll) has no knurling processing (also referred to as "knurling"), and as described above, there is Since the film is supported by the gas (for example, air) in the gap or the entire minute contact surface between the films, the regulating force for preventing winding misalignment is not biased, and the stress applied to the film is uniform.

In addition, by making the void layer thicker at the winding core to take in an appropriate amount of air, even if more air escapes from the winding core during long-term storage of the film roll, the entire film roll will remain intact. By suppressing the deviation in the thickness of the void layer to a small value and forming a uniform void layer between the films, no tape transfer marks remain when the film of the film roll is unwound, and there is no chain-like deformation.

In an embodiment of the present invention, it is preferable that the above-mentioned X [μm] and the above-mentioned Y [μm] satisfy the above-mentioned formula (2) and the above-mentioned formula (3) from the viewpoint of uniform void layer formation during long-term storage.

(1.2) Void layer between films (1.2.1) Means for controlling the thickness of the void layer In the film roll of the present invention, the void layer in order to take in an appropriate amount of air is thickened at the winding core portion. During long-term storage of the film roll, even if more air escapes, especially at the core, the thickness of the void layer throughout the film roll can be kept to a minimum and a uniform void layer can be formed between the films. do.

Examples of such means include means for changing the film touch pressure using a touch roller, and means for changing the winding tension, winding speed, roller rolling angle, and the like.
There may be a plurality of the above-mentioned touch rollers, and the surface may be coated with chrome.
Moreover, an elastic roller or the like can also be used as the touch roller.

(1.2.2) Method for calculating the thickness of the void layer FIG. 1 is a schematic diagram showing the positional relationship between the widthwise side surface of the film roll and the imaging device.
As shown in FIG. 1, the imaging device (E) is installed on the side surface in the width direction of the film roll (30) wound around the core (R).
Note that TD in FIG. 1 is the width direction of the film roll.

Hereinafter, an example of a method of photographing a side surface in the width direction of a film roll using the above-mentioned imaging device and a method of calculating the thickness of the void layer will be described.

An imaging unit (U), which is a part of the imaging device, photographs the widthwise side surface of the film roll centering on an arbitrary point (P) on the widthwise side surface of the film roll, and captures the gaps between the films. Obtain image data for calculation.

FIG. 2 is a schematic view of the widthwise side surface of the film roll viewed from a plane perpendicular to the side surface.

Here, as shown in Fig. 2, when the winding diameter is expressed as a percentage from the winding core surface (S ₀ ) to the outermost film layer (S ₄ ) of the film roll, the winding diameter at the winding core surface (S ₀ ) is , 0%, and the winding diameter of the outermost film layer (S ₄ ) of the film roll is 100%.

When photographing the peripheral part of the winding core, the side part is photographed centering on the position (P ₂₀ ) where the winding diameter is 20%, and the image data is obtained.

In addition, when photographing the central part of the winding, the side part is photographed centering on the position (P ₅₀ ) where the winding diameter is 50%, and when photographing the outer peripheral part of the winding, the winding diameter is 80%. The side surface portion is photographed centering on the position (P ₈₀ ) where the image becomes symmetrical, and the image data is obtained.

After that, edge enhancement processing is performed on the acquired image data to obtain a processed image for calculating the thickness of the void layer as shown in Figure 3. The thickness of the void layer between adjacent films in each of the central part and the outer peripheral part of the winding is calculated.

The thickness of the void layer between the films is calculated in three areas: the core periphery, the center of the roll, and the outer periphery of the roll. Before doing so, first, the concept of the three areas of the winding core periphery, the winding center, and the winding outer periphery will be explained.

FIG. 4 is a simplified conceptual diagram of a part of the widthwise side surface of the film roll for explaining the winding core peripheral area, the winding center area, and the winding outer peripheral area.

In FIG. 4, the film layer directly wound around the winding core (R) and stuck to the winding core surface (S ₀ ) (not shown) is designated as _S1 , and the outermost layer of the film roll is designated as _S4 . When the area from S ₁ to S ₄ is divided into three equal areas, the area on the winding core side is defined as the winding core periphery (A), the area on the outside of the winding is defined as the winding outer periphery (C), The area between the winding core peripheral part (A) and the winding outer peripheral part (C) is defined as the winding central part (B).
In addition, the film layer that forms the boundary between the winding core peripheral area (A) and the winding center area (B) is designated _S2 , and the film layer that forms the boundary between the winding center area (B) and the winding outer peripheral area (C). Let _S3 be the layer of the film.

As a specific example for calculating the thickness of the void layer in the peripheral portion of the winding, for example, the following calculation method can be mentioned.

(Specific example of how to calculate the thickness of the void layer)
For example, in calculating the thickness of the void layer around the winding core, the side surface in the width direction of the film roll is photographed centering on the above-mentioned position (P ₂₀ ), and image data is used to calculate the void between the films. After that, edge enhancement processing is performed on the acquired image data to obtain a processed image as shown in Fig. 3. Starting from the center (P ₂₀ ) of the processed image, the film is rolled perpendicularly to the film surface and directed outward. The radial length is measured using the 100th layer as the end point, and the thickness X [μm] of the void layer is calculated using the following formula (A).

Formula (A) Thickness of the void layer ]÷(Number of layers)

Note that (the number of layers) in the above formula is determined by the number of layers in which the end point is perpendicular to the film surface toward the outside, and if it is in the 100th layer as described above, (Number of layers)=100.

The thickness of the void layer at the center of the winding is calculated in the same manner as above except for changing the position (P ₂₀ ) to the position (P ₅₀ ). In this case, calculation is performed in the same manner as above except that the above-mentioned position (P ₂₀ ) is changed to position (P ₈₀ ).

In addition, since the total length of the film roll is short, when the width direction side part of the film roll is photographed centering on the above-mentioned arbitrary point (P), if there are not 100 layers toward the outside of the film when it is wound perpendicular to the film surface, for example, 70 layers. If there are only up to 100 layers, measure the radial length using the 70th layer as the end point, and use the above formula (A) to calculate the thickness of the void layer X [μm]. good.

As the film thickness meter in the above formula (A), for example, an in-line retardation/film thickness measuring device RE-200L2T-Rth+ film thickness (manufactured by Otsuka Electronics Co., Ltd.) can be used.

(System configuration of imaging unit and imaging device)
The imaging unit used had the following configuration.
FIG. 5 is a schematic diagram of the internal configuration of the imaging unit (U), and S in FIG. 5 is the surface to be measured (lateral side surface portion) of the film roll. The main components in FIG. 5 are as follows.

<Component part>
・Total reflection mirror (60)
・Half mirror (61)
・Telecentric lens (62) (MML1-HR130VI-35F: manufactured by Moritex Co., Ltd., magnification x 1, WD 130mm)
・High brightness line lighting (63) (LNSP2-100SW: manufactured by CCS Corporation)
・Monochrome line sensor camera (64) (RMSL8K39CL: manufactured by Japan Electro Device Co., Ltd., 8000 pixels of 3.5 μm/pixel)

Furthermore, the system configuration of the imaging device was shown in the schematic diagram of FIG. 6.

2. Method for manufacturing a film roll The method for manufacturing a film roll of the present invention is a method for manufacturing a film roll that does not have a knurling part, and the film roll is measured at a side surface in the width direction of the film roll. When the thickness of the void layer between adjacent films at the periphery of the winding core is X [μm], and the thickness of the void layer between adjacent films at the outer periphery of the winding is Y [μm], The present invention is characterized in that the X and the Y are adjusted so as to satisfy the relationship of the formula (1).

In the above film roll manufacturing method, adjusting the X [μm] and the Y [μm] to satisfy the above formula (2) and the above formula (3) forms a uniform void layer during long-term storage. preferred from the viewpoint of

In addition, the film touch pressure at the periphery of the winding core is within a range of 2 to 30 [N/m], the film touch pressure at the center of the winding is within a range of 3 to 40 [N/m], and the film touch pressure at the outer periphery of the winding is within a range of 3 to 40 [N/m]. It is preferable to adjust the film touch pressure within the range of 5 to 55 [N/m] from the viewpoint of forming a uniform air layer during long-term storage.

The film roll of the present invention can be manufactured using conventional manufacturing methods such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method. From the viewpoint of suppressing optical defects such as die lines and the like, the solution casting film forming method and the melt casting film forming method are preferable, and the solution casting film forming method is particularly preferable because it makes the surface of the film uniform. preferred for.

(2.1) Solution casting film forming method FIG. 7 is a flowchart showing the flow of the manufacturing process of the solution casting film forming method, and FIG. 8 is a schematic diagram of an apparatus for manufacturing a film by the solution casting film forming method. It is a diagram.

The solution casting film forming method will be described below with reference to FIGS. 7 and 8.
The film manufacturing method using the solution casting film forming method includes a dope preparation step [S1], a casting step [S2], a peeling step [S3], a shrinking step [S4], a first drying step [S5], and a first stretching step. Step [S6], first cutting step [S7], second stretching step [S8], second cutting step [S9], second drying step [S10], third cutting step [S11], and winding step [ S12].

In addition, the said manufacturing method does not need to include both the 1st drying process [S5] and the 2nd drying process [S10], and should just include at least one of the steps.
Further, the cutting process may include any one of a first stretching process [S6], a second stretching process [S8], a first cutting process [S7], a second cutting process [S9], and a third cutting process [S11]. Bye.

(2.1.1) Dope preparation (stirring preparation) step [S1]
Hereinafter, as an embodiment of the present invention, a dope preparation process will be described using as an example a case where a cycloolefin resin (hereinafter also referred to as "COP") is used as a thermoplastic resin, but the present invention is not limited thereto. .

In the dope preparation (stirring preparation) step [S1] in FIG. 7, at least the resin and solvent are stirred in the stirring tank (1a) of the stirring device (1) in FIG. Prepare a dope to be cast.

(solvent)
As the solvent, a mixed solvent of a good solvent and a poor solvent is used.
This step is a step of dissolving the COP and, in some cases, other compounds in a dissolution pot with stirring in a solvent that is mainly a good solvent for COPs, or adding other compounds to the COP solution in some cases. This is a process of mixing solutions to form a dope, which is the main solution.

From the viewpoint of reducing the drying load after the dope is cast onto a support, it is preferable that the concentration of COP in the dope is high, but if the concentration is too high, the load during filtration of the dope increases and accuracy deteriorates. Therefore, it is necessary to simultaneously reduce the drying load and suppress the load during filtration.
In order to achieve both of these, the concentration of COP in the dope is preferably in the range of 10 to 35% by mass, more preferably in the range of 15 to 30% by mass.
Further, it is preferable that the dope contains water in a range of 0.01 to 2% by mass.

The solvent used in the dope may be used alone or in combination of two or more types, but it is preferable to use a mixture of a good solvent and a poor solvent for COP in terms of production efficiency, and the one with more good solvents is better. is preferable from the viewpoint of solubility of COP.

The preferred range of the mixing ratio of the good solvent and the poor solvent is that the good solvent is in the range of 70 to 98% by mass, and the poor solvent is in the range of 2 to 30% by mass.

In addition, in this specification, a "good solvent" for COP is defined as one that dissolves the COP used alone, and a "poor solvent" for COP is defined as one that independently swells or does not dissolve the COP used. It is defined as
Therefore, a good solvent or a poor solvent varies depending on the average degree of substitution of the COP.

Good solvents used in the present invention are not particularly limited, but include, for example, organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc., with methylene chloride or methyl acetate being particularly preferred. .

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used.

Moreover, the solvent used for dissolving COP is used by recovering the solvent removed from the film by drying in each step and reusing it.

The recovered solvent may contain trace amounts of additives added to COP, such as plasticizers, ultraviolet absorbers, resins, monomer components, etc., but even if these are contained, it is preferable to reuse them. It can also be purified and reused if necessary.

(Dissolution method)
As a method for dissolving COP when preparing the dope described above, a general method can be used.
Specifically, preferred are a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, and a method carried out under pressure above the boiling point of the main solvent.If heating and pressurization are combined, heating can be carried out above the boiling point at normal pressure.

In addition, it is also preferable to stir and dissolve while heating at a temperature above the boiling point of the solvent under normal pressure and within a range where the solvent does not boil under pressure, in order to prevent the formation of lumpy undissolved substances called gels and mako. .

Also preferably used is a method in which COP is mixed with a poor solvent to wet or swell it, and then a good solvent is added to dissolve the COP.

Pressurization may be performed by injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating.
It is preferable to perform heating from the outside. For example, a jacket type is preferable because the temperature can be easily controlled.

A higher heating temperature after adding the solvent is preferable from the viewpoint of solubility of COP, but if the heating temperature is too high, the required pressure will increase and productivity will deteriorate.

The preferred heating temperature is within the range of 30 to 120°C, more preferably within the range of 60 to 110°C, and still more preferably within the range of 70 to 105°C.
Further, the pressure is adjusted so that the solvent does not boil at the set temperature.

Alternatively, a cooling dissolution method is also preferably used, whereby COP can be dissolved in a solvent such as methyl acetate.

(filtration)
Next, this COP solution (the dope being dissolved or after being dissolved) is preferably filtered using a suitable filter medium such as filter paper.

It is preferable for the filter medium to have a low absolute filtration accuracy in order to remove insoluble matters, but if the absolute filtration accuracy is too low, there is a problem in that the filter medium is likely to become clogged.
Therefore, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium within the range of 0.001 to 0.008 mm is more preferable, and a filter medium within the range of 0.003 to 0.006 mm is even more preferable.

There are no particular restrictions on the material of the filter media, and ordinary filter media can be used, but filter media made of plastic such as polypropylene or Teflon (registered trademark), or metal filter media such as stainless steel are preferred since they do not cause fibers to fall off. preferable.

It is preferable to remove or reduce impurities contained in the raw material COP, particularly bright spot foreign substances, by filtration.

A bright spot foreign substance is a phenomenon in which two polarizing plates are arranged in a crossed nicol state, a film, etc. is placed between them, and when light is applied from one polarizing plate side and observed from the other polarizing plate side, the opposite image appears. This is a point (foreign object) from which light from the side appears to leak, and it is preferable that the number of bright spots with a diameter of 0.01 mm or more is 200 pieces/cm ² or less.
More preferably, the number is 100 pieces/cm ² or less, still more preferably 50 pieces/m ² or less, and even more preferably 0 to 10 pieces/cm ² or less.
Further, it is preferable that there are fewer bright spots with a diameter of 0.01 mm or less.

Filtration of the dope can be carried out by the usual method, but the method of filtering while heating at a temperature above the boiling point of the solvent at normal pressure and within the range where the solvent does not boil under pressure is the most effective method for controlling the filtration pressure before and after filtration. This is preferable because the increase in the difference (referred to as differential pressure) is small.

The preferred temperature is within the range of 30 to 120°C, more preferably within the range of 45 to 70°C, even more preferably within the range of 45 to 55°C.

The smaller the filtration pressure, the better.
Specifically, it is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and even more preferably 1.0 MPa or less.

(2.1.2) Casting process [S2]
In the casting step [S2] in FIG. 7, the dope prepared in the dope preparation step [S1] is sent to the casting die (2) in FIG. The dope is cast from a casting die (2) onto a casting position on a support body (3) consisting of a rotationally driven endless belt made of stainless steel to form a casting film (5).

At that time, the inclination of the casting die (2), that is, the direction in which the dope is discharged from the casting die (2) to the support (3), is determined based on the surface of the support (3) (the surface on which the dope is cast). The angle with respect to the normal line may be set appropriately within the range of 0 to 90 degrees.

Thereafter, the cast membrane (5) is heated and dried on the support (3), and the solvent is evaporated until the cast membrane (5) can be peeled off from the support (3) by a peeling roller (4). let
In the present invention, the term "cast film" refers to a doped film cast from the lip portion.

The above evaporation is preferably carried out in an atmosphere within the range of 5 to 75°C.
To evaporate the solvent, there are methods such as applying hot air to the upper surface of the cast film (5), transferring heat from the back side of the support (3) using a liquid, and transferring heat from the front and back sides using radiant heat. However, a method in which heat is transferred from the front and back using radiant heat is preferable because it has good drying efficiency.
Moreover, a method of combining them is also preferably used.

The width of the casting is preferably 1.3 m or more from the viewpoint of productivity.
More preferably, it is within the range of 1.3 to 4.0 m.
If the width of the casting does not exceed 4.0 m, no stripes will appear in the manufacturing process, and stability in the subsequent conveyance process will be high.
From the viewpoint of transportability and productivity, a range of 1.3 to 3.0 m is more preferable.

(Casting die)
Casting dies include coat hanger dies, T dies, etc., and any of them are preferably used.

For those skilled in the art, in order to improve the uniformity of film thickness in the casting process, in both the solution casting film forming method and the melt casting film forming method, the lip part of the casting die (the dope of the casting die slit) An example of this method is to control the slit gap (the opening at the tip of the slit nozzle liquid discharge port).

For example, when extruding a highly viscous dope (including melt), variations in the width of the slit gap will occur, but in order to prevent this, there is a method of controlling the slit gap by installing multiple heat bolts along the width. be.

However, this method has a problem in that there is a physical installation limit on the number of heat bolts.
In addition, there is a method of changing the internal structure of the casting die depending on the width in order to suppress pressure fluctuations in the width that cause variations in the width of the slit gap, but the casting die can be changed depending on the product type. There is a problem in that it is indispensable and requires time and cost.

The casting die is provided with a mechanism that adjusts the width of the slit for discharging the dope (extruding the resin in the case of melting).
Using the heat bolt of the casting die, the width gap of the slit for discharging the dope is adjusted so that the film thickness deviation immediately after discharging is within the range of 1.0 to 5.0% with respect to the entire cast film, It is preferable to control the initial discharge film thickness of the cast film.

In order to increase the film forming speed of the film according to the present invention, two or more of the above-mentioned casting dies may be provided on the support, and the doping amount may be divided and layered.
Alternatively, it is also preferable to obtain a film roll having a laminated structure by a co-casting method in which a plurality of dopes are simultaneously cast.
In order to increase the film forming speed, two or more casting dies may be provided on the support, and the doping amount may be divided and layered.

(Support)
The support (3) is preferably a stainless steel belt or a cast drum whose surface is plated, and is held by a pair of rollers (3a), a roller (3b), and a plurality of rollers located between them. There is.
At this time, the surface of the support is preferably a mirror surface.

One or both of the rollers (3a) and (3b) is provided with a drive device that applies tension to the support (3), thereby causing the support (3) to be in a tensioned state. used in

The surface temperature of the support (3) in the casting step [S2] is within the range of -50° C. to the boiling point of the solvent, and higher temperatures are preferred because the drying rate of the cast membrane can be faster.

The preferred support temperature is within the range of 0 to 55°C, more preferably within the range of 22 to 50°C.

Note that the temperature of the support may be the same throughout or may differ depending on the position.

The method for controlling the temperature of the support (3) is not particularly limited, but there are methods such as blowing hot or cold air or bringing hot water into contact with the back side of the support.
It is preferable to use hot water because heat transfer is more efficient and the time required for the temperature of the support to become constant is shorter.
When using warm air, air at a temperature higher than the target temperature may be used.

(2.1.3) Peeling process [S3]
In this step, in the casting step [S2], the solvent is evaporated on the support (3) until the cast film (5) has a peelable film strength, and after drying and solidification or cooling solidification, the support The film is peeled off from the support (3) before it goes around the body (3) once.
That is, this step is a step in which the film from which the solvent has been evaporated on the support (3) is peeled off at the peeling position.
At this time, from the viewpoints of surface quality, moisture permeability, and peelability, it is preferable to peel the above film from the support within a range of 30 to 600 seconds.

In the peeling step [S3], the film is peeled off with a peeling roller (4) (a roll that helps peel the film) while maintaining self-supporting properties.
The temperature at the peeling position on the support is preferably in the range of -50 to 40°C, more preferably in the range of 10 to 40°C, and most preferably in the range of 15 to 30°C.

(Residual solvent amount)
The amount of residual solvent in the film on the support (3) at the time of peeling in the peeling step [S3] is appropriately adjusted depending on the strength of the drying conditions, the length of the support (3), etc. Since the amount of residual solvent in is greatly influenced by the thickness of the film, the resin, etc., there is an overlap in the preferable range of the amount of residual solvent in the peeling step [S3] and the shrinking step [S4].

The amount of residual solvent in the film varies depending on the thickness of the film, but if the amount of residual solvent at the peeling point (the position where the film is peeled off from the support) is too large, the film may become too soft and difficult to peel. However, the flatness may be impaired, and horizontal steps, warping, and vertical lines may occur more easily due to peeling tension.
Conversely, if the amount of residual solvent is too small, part of the film may peel off during the process.

From the above point of view, in order for the film to exhibit good flatness, it is desirable that the amount of residual solvent be within the range of 10 to 50% by mass from the viewpoint of balance between economical speed and quality.

As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method that allows peeling even when the amount of residual solvent is large.

The above methods include adding a poor solvent for COP to the dope and gelling the cast film after dope casting, and gelling the cast film by cooling the support to increase the amount of residual solvent. There is a method of peeling it off while it is still contained.
Another method is to add a metal salt to the dope.

As described above, by gelling the cast film on the support and strengthening the film, the peeling of the film from the support can be accelerated and the film forming rate can be increased.

The amount of residual solvent is defined by the following formula.

Formula: Residual solvent amount [mass%] = {(MN)/N} x 100

In addition, M in the above formula is the mass of a sample taken at any time during or after manufacturing the cast membrane or film, and N is the mass after heating M at 115° C. for 1 hour.

(Peeling tension)
The peeling tension when peeling the support and the film is preferably 300 N/m or less.
More preferably, the tension is within the range of 196 to 245 N/m, but if wrinkles are likely to occur during peeling, it is preferable to peel with a tension of 190 N/m or less.

(2.1.4) Shrinking process [S4]
The shrinking step [S4] is a step of shrinking the film (F) in the width direction within the plane.
Methods for shrinking the film (F) include, for example, a method in which the film is treated at a high temperature without holding the width thereof to increase the density of the film, and a method in which the film is peeled off from the support in the transport direction (Machine Direction, hereinafter referred to as "MD direction"). ) by applying tension to the film and stretching and shrinking it in the width direction (TD direction) perpendicular to the MD direction within the film plane, and by methods such as sharply reducing the amount of residual solvent in the film. be exposed.
In this case, the film contracts in the transverse direction (hereinafter also referred to as "TD direction") perpendicular to the MD direction within the film plane.

The shrinking process promotes entanglement between resin molecules (matrix molecules) in the thickness direction of the film. It becomes easier to penetrate into the film through the entangled portions (crosslinked portions) between matrix molecules.
As a result, the film can be firmly fixed to the polarizer via the adhesive, and the peel strength of the film to the polarizer can be improved.
In other words, good adhesion between the film and the polarizer can be ensured.

(Definition of shrinkage rate)
In the present invention, the shrinkage rate is defined by the following formula.

Formula: Shrinkage rate [%] = Width of the film at the end of the shrinking process [mm] / Width of the film at the start of the shrinking process [mm] x 100

Here, in the shrinkage step [S4], if the shrinkage rate of the film is too small, the effect of promoting entanglement between matrix molecules will be insufficient, and if it is too large, the production efficiency of the film (stretched film) may decrease. There are concerns.
Therefore, the shrinkage rate of the film in the shrinking step [S4] is preferably within the range of 1 to 40%, more preferably within the range of 5 to 20%.

(Measurement method and calculation method of shrinkage rate)
The width of the film can be measured using LS-9000 manufactured by Keyence Corporation.
In addition, the shrinkage rate of the film according to the present invention can be determined by substituting the average value of each value obtained by measuring the width of the film with the above-mentioned measuring device at 1-second intervals for 5 minutes (300 seconds) into the above formula. However, the method is not limited to the above method, and for example, the width of the film may be determined using a value read from a ruler and substituted into the above formula.

(2.1.5) First drying step [S5]
In the first drying step [S5], the film (F) is heated on the support by the drying device (6) to evaporate the solvent and dry it.

In the drying device (6) in FIG. 8, the film (F) is transported by a plurality of transport rolls arranged in a staggered manner when viewed from the side, and the film (F) is dried during this time.

The drying method in the drying device (6) is not particularly limited, and the film (F) is generally dried using hot air, infrared rays, heated rolls, microwaves, etc. However, from the viewpoint of simplicity, hot air may be used. A method of drying the film (F) is preferred.
Moreover, a method of combining them is also preferable.
Note that the first drying step [S5] may be performed as necessary.

If the film is not thick, it will dry quickly, but if it dries too quickly, the flatness of the finished film will tend to deteriorate.
When drying a film at high temperatures, it is necessary to consider the amount of residual solvent before drying, but failures due to foaming of the solvent can be prevented by ensuring that the amount of residual solvent is not too large.

The amount of residual solvent before the first drying step [S5] is preferably about 30% by mass or less, and the drying temperature is generally within the range of 30 to 250° C. throughout the drying step.
In particular, it is preferable to dry within the range of 35 to 200°C, and it is preferable to increase the drying temperature in stages.

Films are generally dried by a roll drying method (a method in which the film is dried by passing it alternately through a number of rolls arranged above and below) or a tenter method, in which the film is dried while being conveyed.

When using a tenter stretching device to dry the film, use a device that can independently control the gripping length (distance from the start of gripping to the end of gripping) of the film on the left and right sides by the left and right gripping means of the tenter stretching device in the stretching process described below. It is preferable.
Further, in the stretching process, it is also preferable to intentionally create sections having different temperatures in order to improve flatness.

Furthermore, it is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

(2.1.6) First stretching step [S6]
The first stretching step [S6] may be a step of stretching the film (F) only in the MD direction within the film plane, a step of stretching only in the TD direction, or a step of stretching the film (F) only in the MD direction and the TD direction. It may be a step of stretching in both directions, or it may be a step of stretching in an oblique direction.
Moreover, although there is no limitation on the stretching direction, from the viewpoint of obtaining a wide film, it is preferable that there is a step that includes stretching at least in the width direction.
Such stretching is performed by a stretching device (7).

(Stretching method)
As a stretching method, there is a method of stretching in the conveying direction (longitudinal direction of the film; film forming direction; casting direction; machine direction; MD direction) by setting a difference in peripheral speed of the rolls (longitudinal stretching), and a method of stretching the film (F) in the conveying direction (longitudinal direction of the film; A method of fixing both side edges with clips, etc. and stretching (horizontal stretching) in the width direction (orthogonal direction within the film plane; width direction of the film; transverse direction; TD direction), longitudinal stretching and lateral stretching in order. There are methods such as sequential biaxial stretching (sequential biaxial stretching) and simultaneous biaxial stretching (simultaneous biaxial stretching), among which horizontal stretching and simultaneous biaxial stretching (including diagonal stretching) A device is used.
A tenter stretching device is a device that stretches a film by gripping both ends of the film in the width direction with clips and widening the gap while running the clips together with the film.

Among the above methods, the so-called tenter method using a tenter stretching device is preferable in order to improve the performance, productivity, flatness, and dimensional stability of the film.

Further, in the case of the so-called tenter method, it is preferable to drive the clip portion using a linear drive method because smooth stretching can be performed and the risk of breakage etc. can be reduced.

In the film forming process, maintaining the width or stretching in the lateral direction is preferably carried out using a tenter stretching device, which may be a pin tenter or a clip tenter.
Note that in the stretching device (7), drying may be performed in addition to stretching.

(Stretching ratio)
In order to ensure a high retardation, a wide width, and promote penetration of the adhesive when bonding to a polarizer, it is preferable to stretch the film at a high magnification in the stretching step.
However, if the stretching ratio is too high, crazes may occur within the film due to stretching stress, or the entanglements between matrix molecules that maintain film strength may dissociate, making the film brittle.

Therefore, the stretching ratio in the stretching step is preferably within the range of 1.1 to 5.0 times, more preferably within the range of 1.3 to 3.0 times.

In addition, the "stretching ratio" as used in the present invention refers to the ratio [%] of the area of the film after stretching to the area of the film before stretching.
That is, the "stretching ratio" in the above stretching process is such that the total stretching ratio by stretching the film in the longitudinal (longitudinal) direction and the lateral (width) direction is within the range of 1.1 to 5.0 times in area ratio. It is preferably within the range of 1.3 to 3.0 times, and more preferably within the range of 1.3 to 3.0 times.

In addition, when stretching is performed multiple times, it is preferable that the stretching at the highest magnification, which has the highest risk of dissociation of matrix molecules, is performed in the final stage.
For example, in FIG. 7, the stretching at the highest magnification is preferably performed in the second stretching step.
In this case, the entanglement of the matrix molecules can be strengthened by the time of stretching at the maximum magnification, so even if the stretching is performed at the maximum magnification, the dissociation of the entanglement of the matrix molecules can be suppressed and cohesive failure can be suppressed.

(tenter stretching device)
Hereinafter, a case where a tenter stretching device is used as the stretching device (7) will be described as an example with reference to FIGS. 9, 10, 11, and 12.

FIG. 9 is a plan view schematically showing the internal configuration of the tenter stretching device, and is a sectional view of the tenter stretching device viewed from above in a plane perpendicular to the plane of the film.
FIG. 10 shows the tenter stretching device with the cover removed, and the cover is indicated by a two-dot chain line.

FIG. 11 is a schematic diagram of the nozzle and heater installation portions when three zones in the tenter stretching apparatus are viewed from the front.
As shown in Figure 11, the infrared (IR) heater is placed only above the nozzle to prevent the film from coming into contact with the infrared (IR) heater when the film breaks. However, since the radiant energy from the infrared (IR) heater can be concentrated in a narrower area, the infrared (IR) heater is placed as close to the film as possible without interfering with the width-setting operation by the clip.

In addition, in FIG. 11, heat treatment is mainly shown from the center nozzle (105), and in this example, heat treatment by the end nozzle (104) is not performed, but in this embodiment, it can be used in combination. .

When performing heat treatment, it is better to have an infrared (IR) heater coming out from the nozzle gap as shown in Figure 12, so that radiant energy can be transmitted to the film without wasting it.

As shown in FIG. 9, infrared (IR) heaters were arranged in rows so that the entire width of the film could be heated even before stretching.
Note that the heaters may be arranged in a staggered manner in the longitudinal direction.

The tenter stretching device (40) includes a large number of clips (42) that grip both ends of the film (F) in the width direction, and the clips (42) are attached to an endless chain (48) at regular intervals. There is.
The endless chains (48) are arranged on both sides with the film (F) in between, and each is stretched between the driving sprocket (50) on the inlet side and the driven sprocket (52) on the outlet side.
The driving sprocket (50) is connected to a motor (not shown), and by driving this motor, the driving sprocket (50) is rotated.
As a result, the endless chain (48) runs around between the driving sprocket (50) and the driven sprocket (52), so the clip (42) attached to the endless chain (48) runs around.

A rail (54) for guiding the endless chain (48) (or clip (42)) is provided between the driving sprocket (50) and the driven sprocket (52).
The rails (54) are arranged on both sides of the film (F), and the interval between the rails (54) is configured to be wider on the downstream side than on the upstream side in the transport direction of the film (F).
Thereby, when the clips (42) travel around, the distance between the clips (42) is widened, so that the film (F) held by the clips (42) can be stretched laterally in the width direction.

An opening member (56) is attached to each of the driving sprocket (50) and the driven sprocket (52).
The release member (56) is a device that displaces a flapper (not shown) of the clip (42), which will be described later, from the gripping position to the release position. The action is automatic.

By the way, inside the tenter stretching device (40), as shown in FIGS. 9, 10, and 12, a preheating zone, a (lateral) stretching zone, and a heat setting zone are provided.
The zones are separated from each other by a wind-blocking curtain (not shown).
Moreover, inside each zone, hot air is supplied to the film (F) from above or below, or from both.

The hot air is blown out uniformly in the width direction of the film (F) with the temperature controlled at a predetermined temperature for each zone.
Thereby, the temperature inside each zone is controlled to a desired temperature. Each zone will be explained below.

The preheating zone is a zone where the film (F) is preheated, and the film (F) is heated without increasing the interval between the clips (42).

The film (F) preheated in the preheating zone moves to the (transverse) stretching zone.
The (transverse) stretching zone is a zone in which the film (F) is stretched in the width direction (laterally) by widening the interval between the clips (42).
The stretching ratio in this (lateral) stretching process is preferably within the range of 1.0 to 2.5 times, more preferably within the range of 1.05 to 2.3 times, and preferably within the range of 1.1 to 2 times. More preferred.

The film (F) that has been horizontally stretched in the horizontal stretching zone moves to the heat setting zone.

Note that in this embodiment, the interior of the tenter stretching device (40) is divided into a preheating zone, a (lateral) stretching zone, and a heat setting zone, but the types and arrangement of the zones are not limited to this. For example, ( Lateral) A cooling zone for cooling the film (F) may be provided after the stretching zone.
Further, a heat relaxation zone may be provided within the heat fixation zone.

Note that in this embodiment, only (lateral) stretching was performed using the tenter stretching device (40), but stretching may also be performed in the longitudinal direction at the same time.
In this case, the pitch of the clips (42) (the interval between the clips (42) in the transport direction) may be changed when the clips (42) are moved.
As a mechanism for changing the pitch of the clip (42), for example, a pantograph mechanism or a linear guide mechanism can be used.

(Heat treatment timing)
A tenter stretching apparatus is usually divided into multiple zones, for example, as shown in FIGS. 9, 10, and 12, a preheating zone for heating the film, a lateral stretching zone for stretching the film in the transverse direction, and a transverse stretching zone for crystallizing the film. A heat setting zone, a relaxation zone for removing thermal stress from the film, etc. are provided.

(Furnace temperature)
Usually, the temperature inside the furnace is preferably within the range of 120 to 200°C, more preferably within the range of 120 to 180°C.
Here, the "furnace temperature" is the temperature measured at a position 100 mm above the center of the film immediately before stretching (H _A = 100 mm) in the stretching zone of the tenter stretching device described later, and the temperature at each temperature for each minute is It is defined as the value obtained by measuring the values for one hour and calculating the average value thereof.

Usually, the temperature inside the furnace is preferably within the range of 120 to 200°C, more preferably within the range of 120 to 180°C.
Here, when a longitudinal temperature gradient is created in a plurality of sections, the heat treatment section is targeted.

Furthermore, the temperature inside the furnace differs depending on whether or not heat treatment is performed in the drawing zone, but when heat treatment is performed in the drawing zone, the temperature inside the furnace is the same as the temperature inside the furnace in the drawing zone before heat treatment. shall be said.

(Residual solvent amount)
The amount of residual solvent in the film during stretching is preferably 20% by mass or less, more preferably 15% by mass or less.

(2.1.7) First cutting step [S7]
In the first cutting step [S7], a cutting section (8) made of a slitter cuts both ends in the width direction of the film (F) stretched in the first stretching step [S6].
In the film (F), the portions remaining after cutting both ends constitute a product portion that becomes a film product.
On the other hand, the portion cut from the film (F) may be recovered and reused as part of the raw material for film production.

(2.1.8) Second stretching step [S8]
In the second stretching step [S8], the film (F) is stretched by the stretching device (9) similarly to the first stretching step [S6].
At this time, stretching methods include stretching in the transport direction (MD direction) by setting a difference in peripheral speed between the rolls, or fixing both side edges of the film (F) with clips etc. in the width direction (TD direction). ) is preferable in order to improve the performance, productivity, flatness, and dimensional stability of the film.
Note that in the stretching device (9), drying may be performed in addition to stretching.

(2.1.9) Second cutting step [S9]
In the second cutting step [S9], similarly to the first cutting step [S7], the cutting section (10) made of a slitter cuts both ends of the formed film (F) in the width direction.
Note that the gripping portions of the clips at both ends of the film are usually cut off because the film is deformed and cannot be used as a product.
If the material has not deteriorated due to heat, it will be recycled after recovery.

In the film (F), the portions remaining after cutting both ends constitute a product portion that becomes a film product.
On the other hand, the portion cut from the film (F) is recovered and reused as part of the raw material for film production.

(2.1.10) Second drying step [S10]
In the second drying step [S10], the film (F) is dried in the drying device (11) similarly to the first drying step [S5].
Inside the drying device (11), the film (F) is transported by a plurality of transport rolls arranged in a staggered manner when viewed from the side, and the film (F) is dried during this time.

The drying method in the drying device (6) is not particularly limited, and generally includes hot air, infrared rays, heated rolls, microwaves, and the like.
Among the above drying methods, the method of drying the film (F) with hot air is preferred from the viewpoint of simplicity.
Note that the second drying step [S10] may be performed as necessary.

(2.1.11) Third cutting step [S11]
In the third cutting step [S11], similarly to the first cutting step [S7] and the second cutting step [S9], the cutting section (12) consisting of a slitter is cut in the width direction of the formed film (F). Cut both ends.
In the film (F), the portions remaining after cutting both ends constitute a product portion that becomes a film product.
On the other hand, the portion cut from the film (F) is recovered and reused as part of the raw material for film production.

(2.1.12) Winding process [S12]
Finally, in the winding step [S12], the film (F) is wound up by the winding device (13) to obtain a film roll.
That is, in the winding process, a film roll is manufactured by winding the film (F) around the core while conveying the film (F).
The preferable range of the initial tension when winding up the film in the winding process is within the range of 20 to 300 N/m.

FIG. 13 is a schematic view showing the process of winding up the film and the cross section of the film roll of the present invention after being wound up.
When winding up the film (F), it is preferable to install a touch roller (33) as shown in FIG. 13, for example, and change the film touch pressure as appropriate in order to form a desired void layer.
In FIG. 13, the formed film (31) is wound by a roller (32) and a touch roller (33) to form a film roll (30).

(Residual solvent amount)
More specifically, it is a step of winding up the film with a winding device (12) after the amount of residual solvent in the film is 2% by mass or less, and by reducing the amount of residual solvent to 0.4% by mass or less. A film with good dimensional stability can be obtained.
In particular, it is preferable that the amount of residual solvent is within the range of 0.00 to 0.20% by mass.

(Winding method)
The film (F) can be wound using a commonly used winder, and there are methods to control tension such as constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress. , you can use them properly.

Before winding, the ends of the film are slit and trimmed to the desired width, and surface modification treatment may be applied to both ends of the film to prevent sticking and scratches during winding.

(After winding)
The film roll of the present invention is preferably a long film, specifically within a range of about 100 to 10,000 m, and is usually provided in the form of a roll.

(2.2) Film roll manufacturing process by melt-casting film-forming method The film according to the present invention can also be formed by a melt-casting film-forming method.
"Melt film forming method" is a method in which a composition containing a thermoplastic resin and the above-mentioned additives is heated and melted to a temperature that exhibits fluidity, and then the melt containing the fluid thermoplastic resin is cast. means.

Molding methods that involve heating and melting can be classified, in detail, into melt extrusion molding, press molding, inflation, injection molding, blow molding, stretch molding, and the like.
Among these molding methods, melt extrusion is preferred from the viewpoint of mechanical strength, surface precision, and the like.

FIG. 14 is a flowchart showing the flow of the manufacturing process of the melt casting film forming method.
Moreover, FIG. 15 is a schematic diagram of an apparatus for manufacturing a film by a melt casting film forming method.
The solution casting film forming method will be described below with reference to FIGS. 14 and 15.

The method for producing a film roll by the melt casting film forming method includes an extrusion process [M1], a casting/forming process [M2], a first stretching process [M3], a first cutting process [M4], and a second stretching process [M2]. M5], a second cutting process [M6], and a winding process [M7].

In addition, the said manufacturing method does not need to include both the 1st stretching process [M3] and the 2nd stretching process [M5], and should just include at least one of the steps.
Further, the first cutting step [M4] and the second cutting step [M6] may similarly include at least one of the steps.

(2.2.1) Extrusion process [M1]
In the extrusion step [M1], at least the resin is melt-extruded using an extruder (14) and molded onto a cast drum (16).
Details of the above resin that can be used in the present invention will be described later.

Further, it is preferable that the resin is kneaded and pelletized in advance.
Pelletization may be performed by a known method.

For example, dry resin, plasticizer, and other additives are fed to an extruder using a feeder, kneaded using a single-screw or twin-screw extruder, extruded into strands from a casting die (15), and cooled with water or air. It can be made into pellets by cutting.

The additive may be mixed with the resin before being fed to the extruder, or the additive and resin may be fed to the extruder using separate feeders.
Further, in order to uniformly mix small amounts of additives such as particles and antioxidants, it is preferable to mix them with the resin in advance.

When introducing the pellets from the supply hopper to the extruder, it is preferable to dry them, under vacuum or reduced pressure, or under an inert gas atmosphere to prevent oxidative decomposition and the like.

It is preferable that the extruder suppresses shear force and processes the resin at a temperature as low as possible so that it can be pelletized and the resin does not deteriorate (molecular weight reduction, coloration, gel formation, etc.).

For example, in the case of a twin-screw extruder, it is preferable to use deep groove type screws and rotate them in the same direction.
In terms of uniformity of kneading, the interlocking type is preferred.
When the resin/pellet is melted, it is preferable to filter it with a leaf disc type filter or the like to remove foreign substances.

Film formation is performed using the pellets obtained as described above.
Of course, it is also possible to directly feed the raw material resin (powder, etc.) to an extruder using a feeder and form a film without pelletizing it.

(2.2.2) Casting/forming process [M2]
In the casting/forming process [M2], the resin/pellets melted in the extrusion process are cast into a film from the casting die (15) by a conduit through a pressurized metering gear pump, etc., and are transferred endlessly into a rotary driven stainless steel tube. Molten resin pellets are cast from a casting die (15) onto a casting position on a steel endless cast drum (16).
Then, the cast resin pellets in a molten state are molded on a cast drum (16) to form a cast film (18).

The inclination of the casting die (15), that is, the direction in which the molten resin/pellets are discharged from the casting die (15) to the support (16) The angle may be set as appropriate so that the angle is within the range of 0 to 90° with respect to the normal to the surface to be cast.

The film (F) may be formed using a touch roller (16a) or a cooling drum (17) that assists the casting drum (16), either alone or in combination.

(2.2.3) First stretching step [M3]
In the first stretching step [M3], the film (F) is stretched by a stretching device (19).
At this time, the stretching methods include a stretching method in which the peripheral speed of the film is set at a difference and the film is stretched in the MD direction, and a tenter method in which both side edges of the film (F) are fixed with clips or the like and stretched in the TD direction. Preferable for improving performance, productivity, flatness and dimensional stability.
Note that in the stretching device (19), drying may be performed in addition to stretching.

Note that the description of the tenter stretching device, heat treatment timing, furnace temperature, stretching temperature, temperature inside the stretching furnace, amount of residual solvent, etc. is based on the first stretching step [S6] in the film roll manufacturing process by the solution casting film forming method. ] is omitted as it overlaps with the above.

(2.2.4) First cutting process [M4]
In the first cutting step [M4], a cutting section (20) made of a slitter cuts both ends of the formed film (F) in the width direction.
In the film (F), the portions remaining after cutting both ends constitute a product portion that becomes a film product.
On the other hand, the portion cut from the film (F) may be recovered and reused as part of the raw material for film production.

(2.2.5) Second stretching step [M5]
In the second stretching step [M5], the film (F) is stretched by the stretching device (21) similarly to the first stretching step [M3].
At this time, the stretching methods include a stretching method in which the peripheral speed of the film is set at a difference and the film is stretched in the MD direction, and a tenter method in which both side edges of the film (F) are fixed with clips or the like and stretched in the TD direction. Preferable for improving performance, productivity, flatness and dimensional stability.
Note that in the stretching device (21), drying may be performed in addition to stretching.

(2.2.6) Second cutting process [M6]
In the second cutting step [M6], similarly to the first cutting step [M4], the cutting section (22) made of a slitter cuts both ends of the formed film (F) in the width direction.
In the film (F), the portions remaining after cutting both ends constitute a product portion that becomes a film product.
On the other hand, the portion cut from the film (F) may be recovered and reused as part of the raw material for film production.

(2.2.7) Winding process [M7]
Finally, in the winding step [M7], the film (F) is wound up by the winding device (23) to obtain a film roll.
That is, in the winding step [M7], a film roll is manufactured by winding the film (F) around the core while conveying the film (F).

The film (F) can be wound using a commonly used winder, and there are methods to control tension such as constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress. , you can use them properly.

3. Resin constituting the film (3.1) Thermoplastic resin The thermoplastic resin material used for the film according to the present invention is not limited as long as it can be handled as a film roll after film formation.

Examples of thermoplastic resins used for polarizing plates include cellulose ester resins such as triacetylcellulose (TAC), cellulose acetate propionate (CAP), and diacetylcellulose (DAC), and cyclic olefins such as cycloolefin resins. (hereinafter also referred to as "COP"), polypropylene resins such as polypropylene (PP), acrylic resins such as polymethyl methacrylate (PMMA), and polyester resins such as polyethylene terephthalate (PET). can.

However, it is desirable to use COP because it is easy to control stretchability and crystallinity, and because it allows the adhesive to penetrate easily and ensures better adhesion with the polarizer.
Note that the above film may be subjected to surface modification treatment after production.

Further, the effects of the present invention are more valuable in the thin film region.
The thickness of the film is preferably within the range of 5 to 80 μm, more preferably within the range of 10 to 65 μm, and even more preferably within the range of 10 to 45 μm.

If the thickness of the film is 5 μm or more, the rigidity of the film roll will be high and it will be easy to maintain the roll shape.
If the thickness of the film is 80 μm or less, the mass will not increase too much and it will be easier to produce a long film roll.

(3.1.1) Cycloolefin resin The cycloolefin resin contained in the film roll of the present invention is a polymer of cycloolefin monomers, or a copolymerizable monomer of cycloolefin monomers and other monomers. Preferably, it is a copolymer with a body.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2). It is more preferable that there be.

In general formula (A-1), R ¹ to R ⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer from 0 to 2. However, R ¹ to R ⁴ do not all represent hydrogen atoms at the same time, R ¹ and R ² do not represent hydrogen atoms at the same time, and R ³ and R ⁴ do not represent hydrogen atoms at the same time. do.

The hydrocarbon group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ in general formula (A-1) is preferably a hydrocarbon group having 1 to 10 carbon atoms, for example. More preferably, it has 1 to 5 hydrocarbon groups.

The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom.
Examples of such linking groups include divalent polar groups such as carbonyl groups, imino groups, ether bonds, silyl ether bonds, and thioether bonds.
Examples of hydrocarbon groups having 1 to 30 carbon atoms include methyl, ethyl, propyl, butyl, and the like.

Examples of the polar groups represented by R ¹ to R ⁴ in general formula (A-1) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. is included.

Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferable, and from the viewpoint of ensuring solubility during solution film formation, an alkoxycarbonyl group and an aryloxycarbonyl group are preferable.

In general formula (A-1), p is preferably 1 or 2 from the viewpoint of improving the heat resistance of the film.
This is because when p is 1 or 2, the obtained polymer becomes bulky and the glass transition temperature tends to increase.

In the general formula (A-2), R ⁵ represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. R ⁶ represents a carboxyl group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (fluorine atom, chlorine atom, bromine atom, or iodine atom). p represents an integer from 0 to 2.

R ⁵ in the general formula (A-2) preferably represents a hydrocarbon group having 1 to 5 carbon atoms, more preferably a hydrocarbon group having 1 to 3 carbon atoms.

R ⁶ in the general formula (A-2) preferably represents a carboxyl group, a hydroxy group, an alkoxycarbonyl group, or an aryloxycarbonyl group. More preferred is an oxycarbonyl group.

In general formula (A-2), p preferably represents 1 or 2 from the viewpoint of improving the heat resistance of the film.
This is because when p represents 1 or 2, the obtained polymer becomes bulky and the glass transition temperature tends to increase.

A cycloolefin monomer having a structure represented by general formula (A-2) is preferred from the viewpoint of improving solubility in organic solvents.

Generally, the crystallinity of organic compounds decreases by breaking the symmetry, so the solubility in organic solvents improves.

Since R ⁵ and R ⁶ in the general formula (A-2) are substituted only on the ring-constituting carbon atoms on one side with respect to the symmetry axis of the molecule, the symmetry of the molecule is low, that is, the general formula (A- Since the cycloolefin monomer having the structure represented by 2) has high solubility, it is suitable for producing a film by a solution casting method.

The content ratio of the cycloolefin monomer having the structure represented by general formula (A-2) in the cycloolefin monomer polymer is relative to the total of all cycloolefin monomers constituting the cycloolefin resin. For example, it may be 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol%.

When a certain amount or more of a cycloolefin monomer having a structure represented by general formula (A-2) is contained, the orientation of the resin increases, so that the retardation value tends to increase.

Specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown below in Exemplary Compounds 1 to 14, and cycloolefin monomers having a structure represented by general formula (A-2) are shown below. Specific examples of the mer are shown in Exemplary Compounds 15 to 34.

Examples of copolymerizable monomers that can be copolymerized with cycloolefin monomers include copolymerizable monomers that can be ring-opening copolymerized with cycloolefin monomers, and addition copolymerizable monomers that can be copolymerized with cycloolefin monomers. Possible copolymerizable monomers and the like are included.

Examples of copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

Examples of copolymerizable monomers capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl cyclic hydrocarbon monomers, (meth)acrylates, and the like.

Examples of unsaturated double bond-containing compounds include olefinic compounds having 2 to 12 carbon atoms (preferably 2 to 8 carbon atoms), such as ethylene, propylene, butene, and the like.

Examples of vinyl cyclic hydrocarbon monomers include vinyl cyclopentene monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and cyclohexyl (meth)acrylate.

The content of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer is, for example, 20 to 80 mol% with respect to the total of all monomers constituting the copolymer. The amount may be within the range of 30 to 70 mol %, preferably 30 to 70 mol %.

As mentioned above, the cycloolefin resin is produced by polymerizing or It is a polymer obtained by copolymerization, and examples thereof include the following polymers (1) to (7).

(1) Ring-opening polymer of cycloolefin monomer (2) Ring-opening copolymer of cycloolefin monomer and copolymerizable monomer capable of ring-opening copolymerization with it (3) Above (1) or a hydrogenated product of the ring-opened (co)polymer of (2) (4) The ring-opened (co)polymer of (1) or (2) above is cyclized by Friedel-Crafts reaction, and then hydrogen is added. (Co)polymer (5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound (6) Addition copolymer of cycloolefin monomer with vinyl cyclic hydrocarbon monomer Coalescence and its hydrogenated product (7) Alternating copolymer of cycloolefin monomer and (meth)acrylate

The polymers (1) to (7) above can all be obtained by known methods, for example, the methods described in JP-A No. 2008-107534 and JP-A No. 2005-227606.

For example, as the catalyst and solvent used in the ring-opening copolymerization in (2) above, those described in paragraphs 0019 to 0024 of JP-A No. 2008-107534 can be used.

As the catalyst used for the hydrogenated product in (3) and (6) above, for example, those described in paragraphs 0025 to 0028 of JP-A No. 2008-107534 can be used.

As the acidic compound used in the Friedel-Crafts reaction in (4) above, for example, those described in paragraph 0029 of JP-A No. 2008-107534 can be used.

As the catalysts used in the addition polymerizations of (5) to (7) above, those described in paragraphs 0058 to 0063 of JP-A No. 2005-227606 can be used, for example.

The alternating copolymerization reaction (7) above can be carried out, for example, by the method described in paragraphs 0071 and 0072 of JP-A-2005-227606.

Among these, the polymers (1) to (3) and (5) above are preferred, and the polymers (3) and (5) above are more preferred.

In other words, the cycloolefin resin has a structural unit represented by the following general formula (B-1) and a structural unit represented by the following general formula (B-1) in that the resulting cycloolefin resin can have a high glass transition temperature and a high light transmittance. It is preferable to contain at least one of the structural units represented by the following general formula (B-2), only contain the structural unit represented by the general formula (B-2), or contain the structural unit represented by the general formula (B-1). It is more preferable to include both the structural unit represented by the formula (B-2) and the structural unit represented by the general formula (B-2).

The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-1), and is represented by the general formula (B-2). The structural unit represented by the above-mentioned general formula (A-2) is a structural unit derived from a cycloolefin monomer.

In general formula (B-1), X represents -CH=CH- or -CH ₂ CH ₂ -. R ¹ to R ⁴ and p have the same meanings as R ¹ to R ⁴ and p in general formula (A-1), respectively.

In general formula (B-2), X represents -CH=CH- or -CH ₂ CH ₂ -. R ⁵ to R ⁶ and p have the same meanings as R ⁵ to R ⁶ and p in general formula (A-2), respectively.

The cycloolefin resin according to the present invention may be a commercially available product.
Examples of commercially available cycloolefin resins include Arton G (for example, G7810, etc.), Arton F, Arton R (for example, R4500, R4900, and R5000, etc.) manufactured by JSR Corporation, and Arton RX. .

The intrinsic viscosity [η] inh of the cycloolefin resin is preferably within the range of 0.2 to 5 cm ³ /g, and preferably within the range of 0.3 to 3 cm ³ /g when measured at 30°C. is more preferable, and even more preferably within the range of 0.4 to 1.5 cm ³ /g.

The number average molecular weight (Mn) of the cycloolefin resin is preferably within the range of 8,000 to 100,000, more preferably within the range of 10,000 to 80,000, and even more preferably within the range of 12,000 to 50,000. .

The weight average molecular weight (Mw) of the cycloolefin resin is preferably within the range of 20,000 to 300,000, more preferably within the range of 30,000 to 250,000, and even more preferably within the range of 40,000 to 200,000. .

The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured in terms of polystyrene using gel permeation chromatography (GPC).

(gel permeation chromatography)
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (3 units manufactured by Showa Denko K.K. were connected and used)
Column temperature: 25℃
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0mL/min
Calibration curve: A calibration curve using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) within the range of Mw=500 to 2,800,000 was used. The 13 samples are preferably used at approximately equal intervals.

When the intrinsic viscosity [η] inh, number average molecular weight, and weight average molecular weight are within the above ranges, the cycloolefin resin has good heat resistance, water resistance, chemical resistance, mechanical properties, and moldability as a film. Become.

The glass transition temperature Tg [°C] of the cycloolefin resin is usually 110°C or higher, preferably within the range of 110 to 350°C, more preferably within the range of 120 to 250°C, and 120°C. More preferably, the temperature is within the range of ~220°C.

When the glass transition temperature Tg [°C] is 110°C or higher, deformation under high temperature conditions can be easily suppressed.
On the other hand, when the glass transition temperature Tg [° C.] is 350° C. or less, molding becomes easy and deterioration of the resin due to heat during molding is easily suppressed.

The content of the cycloolefin resin is preferably 70% by mass or more, more preferably 80% by mass or more based on the film.

(3.1.2) Acrylic Resin The acrylic resin according to the present invention is a polymer of acrylic ester or methacrylic ester, and also includes copolymers with other monomers.
Therefore, the acrylic resin according to the present invention also includes methacrylic resin.

The resin is not particularly limited, but it consists of methyl methacrylate units in the range of 50 to 99% by mass and other monomer units copolymerizable with this in the range of 1 to 50% by mass. is preferred.

Other units constituting the acrylic resin formed by copolymerization include alkyl methacrylates having an alkyl number of 2 to 18 carbon atoms, alkyl acrylates having an alkyl number of 1 to 18 carbon atoms, isobornyl methacrylate, 2- Hydroxyalkyl acrylates such as hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acryloylmorpholine, acrylamides such as N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, maleic acid, fumaric acid, itaconic acid unsaturated group-containing dicarboxylic acids such as styrene, aromatic vinyl compounds such as α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, Examples include glutarimide and glutaric anhydride.

Examples of copolymerizable monomers forming units other than glutarimide and glutaric anhydride from the above units include monomers corresponding to the above units.

That is, alkyl methacrylates having an alkyl number of 2 to 18 carbon atoms, alkyl acrylates having an alkyl number of 1 to 18 carbon atoms, hydroxyalkyl acrylates such as isobornyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid, etc. α,β-unsaturated acids, acryloylmorpholine, acrylamide such as N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, unsaturated group-containing dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, styrene, α-methylstyrene monomers such as aromatic vinyl compounds such as, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide and N-substituted maleimide.

Further, the glutarimide unit can be formed, for example, by reacting an intermediate resin having a (meth)acrylic acid ester unit with a primary amine (imidizing agent) to imidize it (see JP-A No. 2011-26563). ).

The glutaric anhydride unit can be formed, for example, by heating an intermediate resin having a (meth)acrylic acid ester unit (see Japanese Patent No. 4961164).

Among the above-mentioned structural units, the acrylic resin according to the present invention includes isobornyl methacrylate, acryloylmorpholine, N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, styrene, hydroxyethyl methacrylate, anhydrous Particular preference is given to the inclusion of maleic acid, maleimide, N-substituted maleimide, glutaric anhydride or glutarimide.

The acrylic resin according to the present invention has advantages such as controlling dimensional changes due to changes in environmental temperature and humidity, peelability from metal supports during film production, organic solvent drying properties, heat resistance, and mechanical strength. From the viewpoint of improvement, the weight average molecular weight (Mw) is preferably within the range of 50,000 to 1,000,000, more preferably within the range of 100,000 to 1,000,000, and particularly preferably within the range of 200,000 to 800,000.

If it is 50,000 or more, the heat resistance and mechanical strength are excellent, and if it is 1,000,000 or less, the peelability from the metal support and the drying property of organic solvents are excellent.

The method for producing the acrylic resin according to the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used.

Here, as the polymerization initiator, ordinary peroxide-based and azo-based ones can be used, and redox-based ones can also be used.

Regarding the polymerization temperature, suspension or emulsion polymerization can be carried out within the range of 30 to 100°C, and bulk or solution polymerization can be carried out within the range of 80 to 160°C.

In order to control the reduced viscosity of the obtained copolymer, polymerization can also be carried out using an alkyl mercaptan or the like as a chain transfer agent.

The glass transition temperature Tg [°C] of the acrylic resin is preferably within the range of 80 to 120°C from the viewpoint of maintaining the mechanical strength of the film.

As the acrylic resin according to the present invention, commercially available ones can also be used.
For example, Delpet 60N, 80N, 980N, SR8200 (manufactured by Asahi Kasei Chemicals), Dianal BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB -218, EMB-229, EMB-270, EMB-273 (all manufactured by Mitsubishi Rayon Co., Ltd.), KT75, TX400S, and IPX012 (all manufactured by Denki Kagaku Kogyo Co., Ltd.).
Two or more types of acrylic resin can also be used in combination.

The acrylic resin according to the present invention preferably contains an additive, and as an example of the additive, acrylic particles (rubber elastic particles) described in International Publication No. 2010/001668 are used to improve the mechanical strength of the film. It is preferable to include it for the purpose of improvement and adjustment of the dimensional change rate.

Examples of commercially available multilayered acrylic granular composites include "Metablen W-341" manufactured by Mitsubishi Rayon, "Kane Ace" manufactured by Kaneka, "Paraloid" manufactured by Kureha, and Rohm and Haas. "Acryloid" manufactured by Aika, "Stafyloid" manufactured by Aica, Chemisnow MR-2G, MS-300X (manufactured by Souken Kagaku Co., Ltd.), and "Parapet SA" manufactured by Kuraray, etc. , can be used alone or in combination of two or more.

The volume average particle diameter of the acrylic particles is 0.35 μm or less, preferably within the range of 0.01 to 0.35 μm, and more preferably within the range of 0.05 to 0.30 μm.
If the particle size is above a certain level, the film can be easily stretched under heating, and if the particle size is below a certain level, the transparency of the obtained film is unlikely to be impaired.

From the viewpoint of flexibility, the film of the present invention preferably has a flexural modulus (JIS K7171) of 10.5 GPa or less, more preferably 1.3 GPa or less, and still more preferably 1.2 GPa or less.

The above-mentioned bending elastic modulus varies depending on the type and amount of the acrylic resin and rubber elastic particles in the film, and for example, the larger the content of rubber elastic particles, the lower the bending elastic modulus generally becomes.

Furthermore, the flexural modulus is generally smaller when a copolymer of an alkyl methacrylate and an alkyl acrylate is used as the acrylic resin than when a homopolymer of an alkyl methacrylate is used.

(3.1.3) Cellulose ester resin In the film roll of the present invention, it is also preferable to use a cellulose ester resin.

The cellulose ester used in the present invention refers to some or all of the hydrogen atoms of the 2-, 3-, and 6-position hydroxy groups (-OH) in the β-1,4-bonded glucose units that constitute cellulose. refers to cellulose acylate resin substituted with an acyl group.

The above-mentioned cellulose ester is not particularly limited, but is preferably an ester of a linear or branched carboxylic acid having about 2 to 22 carbon atoms.
The carboxylic acid constituting the ester may be an aliphatic carboxylic acid, may form a ring, or may be an aromatic carboxylic acid.

Examples of the above include, for example, when the hydrogen atom in the hydroxyl group of cellulose has 2 carbon atoms, such as an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, a lauroyl group, a stearoyl group, etc. Examples include cellulose esters substituted with ~22 acyl groups.

The carboxylic acid (acyl group) constituting the ester may have a substituent.
The carboxylic acid constituting the ester is preferably a lower fatty acid having 6 or less carbon atoms, and more preferably a lower fatty acid having 3 or less carbon atoms.

Note that the acyl group in the cellulose ester may be a single type or a combination of a plurality of acyl groups.

Specific examples of preferred cellulose esters include cellulose acetates such as diacetylcellulose (DAC) and triacetylcellulose (TAC), as well as cellulose acetate propionate (CAP), cellulose acetate butyrate, and cellulose acetate propionate butyrate. Examples include mixed fatty acid esters of cellulose to which a propionate group or a butyrate group is bonded in addition to the acetyl group.
These cellulose esters may be used alone or in combination.

(Type of acyl group/degree of substitution)
By adjusting the type and degree of substitution of the acyl group of the cellulose ester, the humidity fluctuation of the retardation can be controlled within a desired range, and the uniformity of the film thickness can be improved.

The smaller the degree of substitution of the acyl group of the cellulose ester, the better the retardation development property becomes, which makes it possible to form a thin film.
On the other hand, if the degree of substitution of the acyl group is too small, durability may deteriorate, which is not preferable.

On the other hand, the higher the degree of substitution of the acyl group in the cellulose ester, the less the retardation will appear, so it is necessary to increase the stretching ratio during film formation, but it is difficult to stretch uniformly at a high stretching ratio. The variation in film thickness increases (deteriorates).

In addition, Rt humidity fluctuation, which is retardation (phase difference) in the thickness direction, is caused by water molecules coordinating with the carbonyl groups of cellulose. The larger the amount, the worse the Rt humidity fluctuation tends to be.

The cellulose ester preferably has a total degree of substitution within the range of 2.1 to 2.5.
By setting it within this range, environmental fluctuations (particularly Rt fluctuations due to humidity) can be suppressed, and the uniformity of the film thickness can be improved.

More preferably, it is within the range of 2.2 to 2.45 from the viewpoint of improving the castability and stretchability during film formation and further improving the uniformity of the film thickness.

More specifically, the cellulose ester satisfies both formulas (a) and (b) below. In the following formulas (a) and (b), X is the degree of substitution of an acetyl group, Y is the degree of substitution of a propionyl group or a butyryl group, or a mixture thereof.

Formula (a): 2.1≦X+Y≦2.5
Formula (b): 0≦Y≦1.5

The cellulose ester is more preferably cellulose acetate (Y=0) and cellulose acetate propionate (CAP) (Y; propionyl group, Y>0), and more preferably Y from the viewpoint of reducing variation in film thickness. = 0, which is cellulose acetate.

Particularly preferably used cellulose acetate is 2.1≦X≦2.5 (more preferably 2.15≦X≦ 2.45) cellulose diacetate (DAC).

In addition, when Y>0, particularly preferably used cellulose acetate propionate (CAP) is 0.95≦X≦2.25, 0.1≦Y≦1.2, 2.15≦X+Y≦ It is 2.45.

By using the above-mentioned cellulose acetate or cellulose acetate propionate, a film roll with excellent retardation, mechanical strength, and environmental fluctuations can be obtained.

In addition, the degree of substitution of acyl groups indicates the average number of acyl groups per glucose unit, and how many hydrogen atoms of the hydroxy groups at the 2nd, 3rd, and 6th positions of 1 glucose unit are substituted with acyl groups. shows.
Therefore, the maximum degree of substitution is 3.0, which means that the hydrogen atoms of the hydroxyl groups at the 2nd, 3rd, and 6th positions are all substituted with acyl groups.

These acyl groups may be substituted on the 2nd, 3rd, and 6th positions of the glucose unit on an average basis, or may be substituted with a distribution.
The degree of substitution is determined by the method specified in ASTM-D817-96.

Cellulose acetates having different degrees of substitution may be mixed and used in order to obtain desired optical properties.
In the above case, the mixing ratio of different cellulose acetates is not particularly limited.

The number average molecular weight (Mn) of the cellulose ester is within the range of 2 x 10 ⁴ to 3 x 10 ⁵ , more preferably within the range of 2 x 10 ⁴ to 1.2 x 10 ⁵ , and further still within the range of 4 x 10 4 to 1.2 x 10 ⁵ . If it is within the range of 8×10 ⁴ , it is preferable from the viewpoint of increasing the mechanical strength of the obtained film roll.

The number average molecular weight (Mn) of the cellulose ester is calculated by measurement using gel permeation chromatography (GPC) under the measurement conditions described above.

The weight average molecular weight (Mw) of the cellulose ester is within the range of 2 x 10 ⁴ to 1 x 10 ⁶ , more preferably within the range of 2 x 10 ⁴ to 1.2 x 10 ⁵ , and further still within the range of 4 x 10 4 to 1.2 x 10 ⁵ . A range of 8×10 ⁴ is preferable from the viewpoint of increasing the mechanical strength of the resulting film roll.

The raw material cellulose for cellulose ester is not particularly limited, but examples include cotton linters, wood pulp, and kenaf.
Moreover, the cellulose esters obtained from these can be mixed and used in arbitrary proportions.

Cellulose esters such as cellulose acetate and cellulose acetate propionate can be produced by known methods.

Generally, raw material cellulose is mixed with specified organic acids (acetic acid, propionic acid, etc.), acid anhydrides (acetic anhydride, propionic anhydride, etc.), and catalysts (sulfuric acid, etc.) to esterify cellulose. The reaction proceeds until the triester is produced.

In triesters, the three hydroxy groups of the glucose unit are replaced with acylic acids of organic acids.

When two types of organic acids are used simultaneously, mixed ester type cellulose esters, such as cellulose acetate propionate and cellulose acetate butyrate, can be produced.

Next, by hydrolyzing the cellulose triester, a cellulose ester resin having a desired degree of acyl substitution is synthesized.
Thereafter, cellulose ester resin is completed through steps such as filtration, precipitation, washing, dehydration, and drying. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

(3.2) Other additives The film roll of the present invention may contain the following in addition to the above-mentioned thermoplastic resin as other additives.

(3.2.1) Plasticizer The film roll of the present invention preferably contains at least one type of plasticizer for the purpose of imparting processability to, for example, a polarizing plate protective film.
It is preferable to use the plasticizer alone or in combination of two or more.

Among the plasticizers, including at least one type of plasticizer selected from the group consisting of sugar esters, polyesters, and styrene compounds is effective for controlling moisture permeability and improving compatibility with base resins such as cellulose esters. This is preferable from the viewpoint of achieving a high degree of compatibility.

The plasticizer preferably has a molecular weight of 15,000 or less, more preferably 10,000 or less, from the viewpoint of achieving both improvement in heat and humidity resistance and compatibility with the base resin such as cellulose ester.

When the compound having a molecular weight of 10,000 or less is a polymer, the weight average molecular weight (Mw) is preferably 10,000 or less.
The weight average molecular weight (Mw) is preferably within the range of 100 to 10,000, more preferably within the range of 400 to 8,000.

In particular, in order to obtain the effects of the present invention, it is preferable to contain the compound having a molecular weight of 1500 or less in the range of 6 to 40 parts by mass, and 10 to 20 parts by mass, based on 100 parts by mass of the base resin. It is more preferable to contain it within this range.
By containing within the above range, effective control of moisture permeability and compatibility with the base resin can be achieved, which is preferable.

(sugar ester)
The film roll of the present invention may contain a sugar ester compound for the purpose of preventing hydrolysis.

Specifically, as a sugar ester compound, it is possible to use a sugar ester that has at least 1 to 12 pyranose or furanose structures and has esterified all or part of the OH groups of the structure. .

(polyester)
The film roll of the present invention can also contain polyester.

Polyesters are not particularly limited, but include, for example, polymers with hydroxyl groups at the ends (polyester polyols) obtained by a condensation reaction of dicarboxylic acids or their ester-forming derivatives with glycol, or polymers with hydroxyl groups at the ends of the polyester polyols. A polymer whose groups are capped with monocarboxylic acid (end-capped polyester) can be used.

Note that the ester-forming derivative referred to herein refers to an esterified product of dicarboxylic acid, a dicarboxylic acid chloride, and an anhydride of dicarboxylic acid.

(Styrenic compound)
In the film roll of the present invention, in addition to or in place of the sugar ester and polyester described above, a styrene compound can also be used for the purpose of improving the water resistance of the film.

The styrene compound may be a homopolymer of a styrene monomer or a copolymer of a styrene monomer and another copolymer monomer.

The content of structural units derived from styrene monomers in the styrene compound is preferably in the range of 30 to 100 mol%, more preferably 50 to 100 mol%, in order for the molecular structure to have a bulkiness above a certain level. It can be within the range.

Examples of styrenic monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; p-hydroxy Hydroxystyrenes such as styrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, and 3,4-dihydroxystyrene; vinylbenzyl alcohols; p-methoxystyrene, p-tert-butoxystyrene, m -Alkoxy-substituted styrenes such as tert-butoxystyrene; Vinylbenzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; 2-butylamidostyrene, 4-methylamide Amidostyrenes such as styrene and p-sulfonamidestyrene; Aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline, and vinylbenzyldimethylamine; Aminostyrenes such as 3-nitrostyrene, 4-nitrostyrene, etc. Nitrostyrenes; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene; indenes; and the like.
The styrenic monomer may be used alone or in combination of two or more types.

(3.2.2) Optional components The film roll of the present invention may contain other optional components such as antioxidants, colorants, ultraviolet absorbers, matting agents, acrylic particles, hydrogen bonding solvents, and ionic surfactants. It can be included.
These components can be added in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the base resin.

(Antioxidant)
In the film roll of the present invention, commonly known antioxidants can be used as antioxidants.
In particular, lactone-based, sulfur-based, phenol-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

These antioxidants and the like are added in an amount of 0.05 to 20% by mass, preferably 0.1 to 1% by mass, based on the resin that is the main raw material of the film.
Rather than using only one type of these antioxidants, a synergistic effect can be obtained by using several different types of compounds together.
For example, it is preferable to use lactone-based, phosphorus-based, phenol-based, and double bond-based compounds in combination.

(colorant)
The film roll of the present invention preferably contains a colorant for color adjustment within a range that does not impair the effects of the present invention.

The term "colorant" refers to a dye or a pigment, and in the present invention, it refers to a material that has the effect of making the color tone of a liquid crystal screen blue-toned, adjusting the yellow index, or reducing haze.

Various dyes and pigments can be used as coloring agents, but anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

(Ultraviolet absorber)
Since the film roll of the present invention can be used on the viewing side or backlight side of a polarizing plate, it may contain an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function.

The ultraviolet absorber is not particularly limited, but includes, for example, benzotriazole-based, 2-hydroxybenzophenone-based, or salicylic acid phenyl ester-based ultraviolet absorbers.

For example, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(3,5 -triazoles such as -di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc. Examples include benzophenones.
The above ultraviolet absorbers can be used alone or in combination of two or more.

The amount of the ultraviolet absorber used varies depending on the type of ultraviolet absorber, usage conditions, etc., but is generally within the range of 0.05 to 10% by mass, preferably 0.1% by mass based on the base resin. It is added within a range of 5% by mass.

(fine particles)
The film roll of the present invention preferably contains fine particles that impart slipperiness to the film roll.
In particular, it is effective to add fine particles from the viewpoint of improving the slipperiness of the surface of the film according to the present invention, improving the slipperiness during winding, and preventing the occurrence of scratches and blocking.

The fine particles may be either inorganic fine particles or organic fine particles as long as they do not impair the transparency of the obtained film roll and have heat resistance during melting, but inorganic fine particles are more preferred.
These fine particles can be used alone or in combination of two or more.

By using particles with different particle sizes and shapes (for example, acicular and spherical), it is possible to achieve both high transparency and slipperiness.

Among the compounds constituting the fine particles, silicon dioxide is particularly preferably used because it has a refractive index close to that of the cycloolefin resin, acrylic resin, or cellulose ester resin, and thus has excellent transparency (haze).

Specific examples of silicon dioxide include Aerosil (registered trademark) 200V, Aerosil (registered trademark) R972V, Aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (Japan Aerosil Co., Ltd. ), Seahoster (registered trademark) KEP-10, Seahoster (registered trademark) KEP-30, Seahoster (registered trademark) KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Cylohobic (registered trademark) 100 (Fuji Silicia) Commercial products having trade names such as Nip Seal (registered trademark) E220A (manufactured by Nippon Silica Kogyo Co., Ltd.) and AdmaFine (registered trademark) SO (manufactured by Admatex Co., Ltd.) can be preferably used.

The shape of the particles may be amorphous, acicular, flat, spherical, etc. without any particular limitation, but spherical particles are particularly preferred since they can improve the transparency of the resulting film roll.

If the particle size is close to the wavelength of visible light, light will be scattered and transparency will deteriorate, so it is preferably smaller than the wavelength of visible light, and more preferably 1/2 or less of the wavelength of visible light. .

If the particle size is too small, the slipperiness may not be improved, so it is particularly preferably within the range of 80 to 180 nm.
Note that the particle size means the size of the aggregate when the particle is an aggregate of primary particles.
Furthermore, when the particle is not spherical, it means the diameter of a circle corresponding to its projected area.

The fine particles are preferably added in an amount of 0.05 to 10% by mass, preferably 0.1 to 5% by mass, based on the base resin.

4. Polarizing Plate A part of the film of the film roll of the present invention can be suitably used by being included in a polarizing plate.
A polarizing plate is generally composed of a polarizer film (also referred to as a "polarizing film" or "polarizer film") and transparent resin films laminated on both sides of the polarizer film, and is one of the film rolls of the present invention. For example, the film may be included in a polarizing plate as the resin film.

Examples of the polarizing plate include those having a structure including a polarizer layer using a polarizer film, a polarizing plate protective film using a resin film, and an adhesive layer disposed between them.

(4.1) Polarizer layer The above-mentioned polarizer layer is a layer consisting of at least a polarizer film.
Here, the term "polarizer" refers to an element that passes only light with a plane of polarization in a certain direction.

Examples of polarizing films include polyvinyl alcohol-based polarizing films and cellulose ester-based polarizing films, but polyvinyl alcohol-based resins have superior transparency, optical properties, durability, etc. compared to cellulose ester-based resins. Preferable from this point of view.

Polyvinyl alcohol-based polarizing films include those made by dyeing polyvinyl alcohol-based films with iodine and those made by dyeing them with dichroic dyes.

The polyvinyl alcohol polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing it with iodine or a dichroic dye (preferably a film further subjected to durability treatment with a boron compound), or It may be a film obtained by dyeing an alcoholic film with iodine or a dichroic dye and then uniaxially stretching the film (preferably, a film further subjected to durability treatment with a boron compound).
The absorption axis of the polarizer layer is usually parallel to the direction of maximum stretch.

For example, ethylene with an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%, as described in JP-A No. 2003-248123, JP-A No. 2003-342322, etc. Modified polyvinyl alcohol is used.

The thickness of the polarizer layer is preferably 5 to 30 μm, and more preferably 5 to 20 μm in order to make the polarizing plate thinner.

(4.2) Polarizing plate protective film A part of the film of the film roll of the present invention can be disposed on at least one surface of the polarizer layer (at least the surface facing the liquid crystal cell), and the polarizing plate protective film or It can be used as a retardation film.
The surface of the polarizing plate protective film on which the polarizer layer is laminated may be subjected to the activation treatment described below.

When a part of the film of the film roll of the present invention is arranged only on one side of the polarizer layer as a polarizing plate protective film, other optical film such as a retardation film may be placed on the other side of the polarizer layer. A film may be placed.

Examples of other optical films include commercially available cellulose ester films (e.g., Konica Minolta Tac KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, manufactured by Konica Minolta Co., Ltd., Fujitac T40UZ, Fujitac T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, (manufactured by Fuji Film Co., Ltd.), etc.

The thickness of the other optical film may be, for example, 5 to 100 μm, preferably 40 to 80 μm.

(4.3) Adhesive layer The adhesive layer is a water-based adhesive or an ultraviolet curable adhesive placed between a part of the film (or other optical film) of the film roll of the present invention and the polarizer layer. It is dried.

The thickness of the adhesive layer may be, for example, about 0.01 to 10 μm, preferably about 0.03 to 5 μm.

(water-based adhesive)
Examples of water-based adhesives include vinyl adhesives, gelatin adhesives, vinyl latex adhesives, polyurethane adhesives, isocyanate adhesives, polyester adhesives, and epoxy adhesives.

When a polyvinyl alcohol-based polarizing film is used in the polarizer layer, a water-based adhesive containing a vinyl resin is preferable from the viewpoint of easy adhesion. polyvinyl alcohol aqueous solution, etc.) are more preferable.

The water-based adhesive containing the polyvinyl alcohol resin may further contain a water-soluble crosslinking agent such as boric acid, borax, glutaraldehyde, melamine, and oxalic acid.

(UV curable adhesive)
The ultraviolet curable adhesive may be a radical photopolymerizable composition or a cationic photopolymerizable composition.
Among these, photocationic polymerizable compositions are preferred.

The cationic photopolymerizable composition includes an epoxy compound and a cationic photopolymerization initiator.

An epoxy compound is a compound having one or more, preferably two or more, epoxy groups in the molecule.

Examples of epoxy compounds include hydrogenated epoxy compounds obtained by reacting alicyclic polyols with epichlorohydrin (glycidyl ether of polyols having an alicyclic ring); aliphatic polyhydric alcohols or their alkylenes; Aliphatic epoxy compounds such as oxide adduct polyglycidyl ether; alicyclic epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule are included.
The epoxy compounds may be used alone or in combination of two or more.

The photocationic polymerization initiator may be, for example, an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt; or an iron-arene complex.

The cationic photopolymerization initiator may further contain additives such as a cationic polymerization promoter such as oxetane and polyol, a photosensitizer, and a solvent, if necessary.

(4.4) Method for manufacturing a polarizing plate The method for manufacturing a polarizing plate according to the present invention includes 1) performing an activation treatment on the surface of a polarizing plate protective film, and 2) performing an activation treatment on the polarizing plate protective film. 3) a step of laminating a polarizer layer (polarizing film) on the applied surface via a water-based adhesive or an ultraviolet curable adhesive; and 3) a step of drying the obtained laminate.

Regarding the step 1), the surface of the polarizing plate protective film (the surface to be bonded to the polarizer layer) is subjected to activation treatment.
This makes it easier to obtain adhesiveness with the polarizer layer.

Specifically, through activation treatment, the side chain siloxane bonds, ether bonds, tertiary carbon atoms, etc. of the specific graft polymer contained in the polarizing plate protective film are made hydrophilic, thereby improving the affinity with water-based adhesives. The polarizing plate protective film and the polarizer layer can be easily bonded together by increasing the polarizing plate protective film and making it easier to interact with each other.

Examples of activation treatments include corona treatment, plasma treatment and saponification treatment, preferably corona treatment and plasma treatment, more preferably corona treatment.

The activation treatment conditions may be of a level that can sufficiently activate the siloxane bonds, ether bonds, tertiary carbon atoms, etc. contained in the side chains of the specific graft polymer.
When the activation treatment is corona treatment, the irradiation amount is preferably within the range of 100 to 1000 [W min/m ² ], and preferably within the range of 150 to 900 [W min/m ² ]. It is more preferable.

Regarding Step 2) Next, a polarizer layer is laminated on the activated surface of the polarizing plate protective film via a water-based adhesive or an ultraviolet curable adhesive.

Regarding Step 3) Next, the obtained laminate is dried to obtain a polarizing plate.

Drying can be performed by heating.
The drying temperature may be any temperature at which the water-based adhesive or ultraviolet curable adhesive is sufficiently dried, and may be, for example, within the range of 60 to 100°C.

5. Display Device A part of the film of the film roll of the present invention can be suitably used by being included in a display device.
Examples of the display device include various image display devices such as a liquid crystal display device and an organic EL display device.
Below, as an example of use of some films of the film roll of the present invention, a case will be described in which the film is provided in a polarizer and a liquid crystal display device as a polarizing plate protective film.

(5.1) Liquid Crystal Display Device A specific example of the display device of the present invention is a liquid crystal display device including, for example, a liquid crystal cell and a pair of polarizing plates sandwiching the cell.

FIG. 16 is a schematic diagram showing an example of the configuration of a liquid crystal display device of the present invention.
As shown in FIG. 16, the liquid crystal display device (300) includes a liquid crystal cell (220), a first polarizing plate (210) and a second polarizing plate (230) that sandwich it, and a backlight (240). ).

The display mode of the liquid crystal cell (220) may be various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), and IPS. ) mode is preferable.

The first polarizing plate (210) includes a first polarizer (212), a polarizing plate protective film (211) disposed on the surface of the first polarizer (212) opposite to the liquid crystal cell, and a polarizing plate protective film (213) disposed on the surface of the first polarizer (212) on the liquid crystal cell side.

The second polarizing plate (230) includes a second polarizer (232), a polarizing plate protective film (231) disposed on the surface of the second polarizer (232) on the liquid crystal cell side, and a second polarizer (232). It includes a polarizing plate protective film (233) disposed on the opposite side of the polarizer (232) from the liquid crystal cell. One of the polarizing plate protective films (213) and (231) may be omitted if necessary.

At least one of the polarizing plate protective films (211) and (233) may be the resin film according to the present invention.

(5.2) Other uses Some films of the film roll of the present invention can be used not only as polarizing plate protective films for liquid crystal display devices, but also for image display devices equipped with touch panels, organic EL displays, plasma displays, etc. It can also be preferably used as a protective film for image display devices and the like.

Note that the embodiments to which the present invention is applicable are not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the present invention.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In the examples, "parts" or "%" are used, but unless otherwise specified, "parts by mass" or "% by mass" are expressed.

[A Production of film roll]
[A.1 Film roll No. Preparation of 1]
A solution casting method was used to form the film.

(Dope preparation step [S1])
<Synthesis of cyclic polyolefin polymer [P-1]>
100 parts by mass of purified toluene and 100 parts by mass of norbornenecarboxylic acid methyl ester were charged into a stirring device.

Next, 25 mmol % of ethylhexanoate-Ni (based on the monomer mass) dissolved in toluene, 0.225 mol% of tri(pentafluorophenyl)boron (based on the monomer mass), and 0.25 mol% of triethylaluminum dissolved in toluene (based on the monomer mass) (based on monomer mass) was put into a stirring device.
The reaction was allowed to proceed for 18 hours at room temperature with stirring.

After the reaction was completed, the reaction mixture was poured into excess ethanol to form a polymer precipitate.
A cyclic polyolefin polymer [P-1] was synthesized by vacuum drying the polymer obtained by purifying the precipitate at 65° C. for 24 hours.

<Preparation of cyclic polyolefin solution (dope [D-1])>
The following composition [1] was put into a mixing tank, stirred to dissolve each component, and then filtered through a filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to obtain a cyclic polyolefin solution (dope [D-1). ) was prepared.

《Composition [1]》
・Cyclic polyolefin polymer [P-1] 25 parts by mass ・Dichloromethane 65 parts by mass ・Ethanol 10 parts by mass

<Preparation of fine particle dispersion [1]>
Next, the following composition [2] was put into a dispersion machine to prepare a fine particle dispersion liquid [1] as an additive.

《Composition [2]》
・Fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle diameter: 7 nm, apparent specific gravity 50 g/L) 4 parts by mass ・Dichloromethane 76 parts by mass ・Ethanol 20 parts by mass

<Preparation of film-forming dope [1]>
100 parts by mass of the above cyclic polyolefin solution (dope [D-1]) and 0.75 parts by mass of fine particle dispersion liquid [1] were mixed to form a film-forming dope [1] (resin composition cycloolefin resin: COP). was prepared.

(Casting process [S2])
The film-forming dope [1] (resin composition cycloolefin resin: COP) prepared in the dope preparation step [S1] is sent to the casting die by a conduit through a pressurized metering gear pump, and is transferred indefinitely. The dope is cast from a casting die to a casting position on a support made of a rotatably driven stainless steel endless belt in a width of 1800 mm using a film forming line, heated on the support until the dope becomes self-supporting, The solvent was evaporated and dried until the cast membrane could be peeled off from the support using a peeling roller, thereby forming a cast membrane.

(Peeling process [S3])
In the casting step [S2], after forming a cast membrane, the cast membrane was peeled off from the support with a peeling roller while maintaining self-supporting properties.

(Shrinking process [S4])
The film was subjected to high-temperature treatment without being held in the width direction to increase the density of the film, thereby shrinking the film in the width direction at a shrinkage rate of 7%.

(First drying step [S5])
The film was then heated on the support to evaporate the solvent.
When the amount of residual solvent in the film was measured by the method described below, it was found to be 5% by mass or less.

<Residual solvent amount measurement>
The amount of residual solvent was determined by mass spectrometry using gas chromatography as described below.
That is, a piece of the film was taken from an arbitrary location, and in order to prevent the solvent remaining in the film from volatilizing, it was immediately placed in a vial and capped.
Next, a needle was inserted into the vial, and mass spectrometry was performed using a gas chromatograph (manufactured by Agilent Technologies).

Note that the amount of residual solvent is defined by the following formula.
Amount of residual solvent [mass%] = {(MN)/N} x 100
In addition, M in the above formula is the mass [g] of the sample taken at any time during or after manufacturing the cast membrane or film, and N in the above formula is the mass [g] of the sample collected at 115°C. It is the mass [g] after heating for a period of time.

(First stretching step [S6])
Thereafter, the film was conveyed within a tenter stretching device and was laterally stretched.

(First cutting step [S7])
Both ends of the stretched film in the width direction were cut.

(Second stretching step [S8])
Similarly to the first stretching step, the film was stretched using a tenter stretching device.
The amount of residual solvent in the film was measured by the method described above and was found to be 1 to 5% by mass.

(Second cutting step [S9])
Similarly to the first cutting step, both ends of the stretched film in the width direction were cut.

(Second drying step [S10])
Similar to the first drying step, the film was heated on the support to evaporate the solvent.
The amount of residual solvent in the film was measured by the above method and was found to be 0.1 to 2% by mass.

(Third cutting step [S11])
Similarly to the first cutting step and the second cutting step, both ends of the stretched film in the width direction were cut.

(Winding process [S12])
The above film was wound up at a winding speed (line speed for transporting the film) of 60 m/min, a film roll width of 2000 mm, and a winding length of 10000 m.
The thickness of the film upon winding was measured and found to be 40 μm.

In addition, using a winding device and TR (touch roller), the touch pressure around the winding core during winding was adjusted to 15.2 N/m, the tension was adjusted to 40 N/m, and the touch pressure at the center of the winding was adjusted to 15.2 N/m. 16.0N/m, the tension was adjusted to 40N/m, the touch pressure on the outer peripheral part of the winding was adjusted to 16.0N/m, the tension was adjusted to 40N/m, and the taper was 70% and the corner was 25%. .

The thickness of the film was measured at 1,612 points using an in-line retardation/film thickness measuring device RE-200L2T-Rth+ Film Thickness (manufactured by Otsuka Electronics Co., Ltd.). The difference in height from the lower part was calculated and taken as the average value.
At this time, the traverse movement speed was 100 mm/sec.

Through the above steps, film roll No. 1 was prepared.

[A.2 Film roll No. Preparation of 2 to 13]
In the dope preparation step [S1], the type of film-forming dope (resin composition), the winding length [m] in the winding step [S12], the winding speed [m/min], the thickness of the film [μm], Touch pressure [N/m] and tension [N/m] around the core during winding, touch pressure [N/m] and tension [N/m] around the center of the winding, touch pressure around the outer periphery of the winding Film roll No. 1 was used except that [N/m] and tension [N/m] were changed as shown in Table I. Similarly to 1, film roll No. 2 to 13 were produced.

[B Calculation of the thickness of the void layer around the winding core, at the center of the winding, and at the outer periphery of the winding]
After storing each produced film roll for one week at 40°C and 80% RH, the areas around the core, the center of the roll, and the outside of the roll were measured using the method described above (an example of a method for calculating the thickness of the void layer). The thickness of the void layer was calculated.

Below is the film roll number. A specific method of calculating the thickness of the void layer around the winding core using 1 is shown below.

Film roll No. after storage for one week. The side surface portion of No. 1 in the width direction is photographed centering on the position (P ₂₀ ) where the winding diameter is 20%, the image data is obtained, and the obtained image data is subjected to edge enhancement processing. A processed image for calculating the thickness of the void layer as shown in No. 3 was obtained.

Thereafter, the radial length is measured starting from the center of the processed image (P ₂₀ ) and winding perpendicularly to the film surface toward the outside with the end point at the 100th layer, and formula (A) below is calculated. Using this, the thickness X [μm] of the void layer around the winding core was calculated.

Formula (A) Thickness of the void layer ]÷(Number of layers)

When the measured value is substituted, film roll No. The thickness of the void layer of No. 1 was X [μm]=[4021μm−40.00μm×100]÷100=0.21μm.

Regarding the thickness of the void layer at the center of the winding, a photograph is taken of the side surface in the width direction centered at the position (P ₅₀ ) where the winding diameter is 50%, and the center (P ₅₀ ) of the processed image is taken as the starting point. The thickness was calculated in the same manner as the thickness of the void layer around the winding core, except for the above.

Regarding the thickness of the void layer at the outer periphery of the winding, a photograph is taken of the side surface in the width direction centered at the position (P ₈₀ ) where the winding diameter is 80%, and the center (P ₈₀ ) of the processed image is The thickness was calculated in the same manner as the thickness of the void layer around the winding core, except that the starting point was used.

[C rating]
[C. 1 Evaluation based on degree of tape transfer]
(Evaluation method)
After unwinding the film of each film roll after storage for one week as described above, the tape transfer with clearly visible band-like deformation in the width direction is displayed on the winding device from the core part to the length of the film. The position value of the direction was measured using a tachometer and evaluated based on the following evaluation criteria. The results are shown in Table I.

(Evaluation criteria)
Good: Tape transfer occurred only up to less than 20 m from the winding core.
Δ: Tape transfer occurs up to 20 m or more and less than 50 [m] from the winding core.
×: Tape transfer occurs at a distance of 50 m or more from the winding core.

[C. 2 Evaluation based on degree of chain-like deformation]
(Evaluation method)
Unwind the film of each film roll after storage for one week as described above, measure the length [m] of the film where chain-like deformation has occurred, and measure the position value in the longitudinal direction of the film displayed on the winding device using a tachometer. and evaluated based on the following evaluation criteria.
In addition, it was judged that there is no problem in practical use if it is △ or more in the following evaluation criteria. The results are shown in Table I.

(Evaluation criteria)
◎: The length of the film in which chain-like deformation occurred is less than 10 m.
O: The length of the film in which chain-like deformation has occurred is 10 m or more and less than 50 m.
Δ: The length of the film in which chain-like deformation occurred is 50 m or more and less than 200 m.
×: The length of the film in which chain-like deformation occurred is 200 m or more.

[D Summary]
As is clear from the conditions and evaluation results shown in Table I, the examples of the present invention were evaluated higher in the degree of tape transfer and the degree of chain-like deformation than the comparative examples, and were superior overall. I understand.

1, 1a Stirring device (stirring tank)
2 Casting die 3 Support (endless belt, drum)
3a, 3b roller 4 peeling roller 5 casting film 6 drying device 7 stretching device (tenter stretching device, diagonal stretching device)
8 Cutting section 9 Stretching device (tenter stretching device)
10 cutting section 11 drying device 12 cutting section 13 winding device 14 extruder 15 casting die 16 cast drum, support 16a touch roller 17 cooling drum 19 stretching device (tenter stretching device)
20 Cutting section 21 Stretching device (tenter stretching device)
22 cutting section 23 winding device 30 film roll 31 film 32 roller 33 touch roller 40 stretching device (tenter stretching device)
42 Clip 46 Cover 48 Endless chain 50 Driving sprocket 52 Driven sprocket 54 Rail 56 Open member 60 Total reflection mirror 61 Half mirror 62 Telecentric lens 63 High brightness line illumination 64 Monochrome line sensor camera 80 Temperature distribution sensor 101 Nozzle fixed part 102 Nozzle 103 Casting film 104 End nozzle 105 Center nozzle 106 Clip cover 200 Liquid crystal display device 210 First polarizing plate 211 Polarizing plate protective film disposed on the surface of the first polarizer opposite to the liquid crystal cell side 212 First Polarizer 213 Polarizing plate protective film disposed on the surface of the first polarizer on the liquid crystal cell side 220 Liquid crystal cell 230 Second polarizing plate 231 Polarizing plate disposed on the surface of the second polarizer on the liquid crystal cell side Protective film 232 Second polarizer 233 Polarizing plate protective film disposed on the surface of the second polarizer opposite to the liquid crystal cell side 240 Backlight A Winding core periphery B Winding center C Winding outer periphery F Film H _A , H _B width Q Thermocouple, infrared (IR) heater E Imaging device R Winding core TD Width direction of the film roll U Imaging unit P Any point on the lateral side of the film roll S Surface to be measured (lateral side)
S ₀ roll core surface S ₁ film layer stuck to the roll core surface S ₂ film layer that forms the boundary between the core periphery and the winding center S _{3 film layer that forms the boundary between the 3} roll center and the outer periphery Boundary film layer S Outermost film layer of ₄ film rolls P ₂₀ Position where the roll diameter is 20% P ₅₀ Position where the roll diameter is 50% P ₈₀ Position where the roll diameter is 80%

Claims (7)

A film roll that does not have a knurling part,
The thickness of the void layer between adjacent films at the periphery of the winding core measured at the widthwise side surface of the film roll is defined as X [μm], and the void layer between adjacent films at the periphery of the winding core is X [μm]. A film roll characterized in that when the thickness of the film is Y [μm], the X and the Y satisfy the relationship of the following formula (1).
Formula (1): Y<X The film roll according to claim 1, wherein the X [μm] and the Y [μm] satisfy the following formula (2) and the following formula (3).
Formula (2): 0.05<Y<0.50
Formula (3): 1<(X/Y)<3 A film roll manufacturing method for manufacturing a film roll without a knurling part, the method comprising:
The thickness of the void layer between adjacent films at the periphery of the winding core measured at the side surface in the width direction of the film roll is defined as X [μm], and the thickness of the void layer between adjacent films at the periphery of the winding core is defined as X [μm]. A method for producing a film roll, characterized in that when the thickness of the void layer is Y [μm], the X and Y are adjusted so as to satisfy the relationship of the following formula (1).
Formula (1): Y<X The method for manufacturing a film roll according to claim 3, wherein the X [μm] and the Y [μm] are adjusted so as to satisfy the following formula (2) and the following formula (3).
Formula (2): 0.05<Y<0.50
Formula (3): 1<(X/Y)<3 The film touch pressure at the periphery of the winding core is within the range of 2 to 30 [N/m], the film touch pressure at the center of the winding is within the range of 3 to 40 [N/m], and the film at the outer periphery of the winding. 5. The method for manufacturing a film roll according to claim 3, wherein the touch pressure is adjusted within a range of 5 to 55 [N/m]. A polarizing plate comprising a part of the film of the film roll according to claim 1 or 2. A display device comprising a part of the film of the film roll according to claim 1 or 2.

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