Film roll, method for manufacturing the same, polarizing plate, and display device

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

Technical Field

[0001] 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 or the like that does not leave a tape transfer trace and does not have a chain-like film deformation due to air leakage during long-term storage.

Background Art

[0002] In recent years, with the fierce price competition in liquid crystal televisions, cost reduction measures such as reducing switching losses have been considered by polarizing plate manufacturers, and in response, the length of the film used for polarizing plates has been increasing.

[0003] By increasing the length of the film, cost reduction can be expected from various viewpoints such as splicing loss, inspection man-hours, transportation, and auxiliary materials. The film is usually wound into a roll after being manufactured for the convenience of storage and transportation.

[0004] However, when a film roll with a long film wound is stored for a long time, when the film is unwound, tape transfer traces due to adhesion between the films remain (hereinafter also referred to as "tape transfer"), and there is a problem that chain-like film deformation (hereinafter also referred to as "chain-like deformation") occurs due to air leakage between the films.

[0005] Here, the above-mentioned "chain-like deformation" refers to deformation (chain-like defect) of the film caused by the stress due to the self-weight of the film after winding and the stress tending to extend in the width direction of the film.

[0006] As a means for solving the above problems, a means of winding together with a protective film can be considered, but there is a problem that the protective film becomes waste.

[0007] As a means of solving the above problems without generating waste, it is conceivable to perform nailing processing in advance at the end of the film and take in air between the films during winding to form an air gap layer of appropriate thickness (also referred to as an "air layer"), thereby suppressing the sticking of the films to each other. However, the means by the above nailing processing has a problem that the effect of suppressing sticking is weaker compared to the means of winding together with the protective film.

[0008] In addition, by using the above means, the pressure applied to the surface of the film becomes larger as it gets closer to the winding core of the film roll, and the air between the films easily escapes, resulting in a thinner air gap layer. Therefore, there is a problem that tape transfer marks due to sticking of the films wound near the winding core and chain-like deformation due to air escape between the films when the film roll is stored for a long time occur.

[0009] In Patent Document 1, a means is disclosed in which, when winding the film, the amount of air taken into the films is made constant by changing the magnitude of the winding tension and the height of the nailing at the end of the film corresponding to the winding diameter of the film roll, thereby forming an air gap layer of appropriate thickness. However, there is still room for improvement in order to solve the above problems.

[0010] In this specification, the "air gap layer" refers to a layer formed by the gap between the opposing surfaces of adjacent films in a film roll, and is a layer in which air or other substances other than air (such as a gas such as an inert gas) may exist. Strictly speaking, the layer composed of air in this "air gap layer" is called an "air layer", but when not distinguishing between the two does not particularly affect the present invention, the "air layer" shall be referred to as the "air gap layer". Furthermore, a form in which adjacent films have fine, film-specific irregularities on one film surface that are in contact at various points with the opposing film surface is also considered a form of void layer. However, in this invention, void layers formed by knurling (irregular shapes) artificially applied to the film by knurling are not included. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2013-46966 [Overview of the project] [Problems that the invention aims to solve]

[0012] This invention has been made in view of the above-mentioned problems and circumstances, and its objective is to provide 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, a method for manufacturing the same, a polarizing plate, and a display device. [Means for solving the problem]

[0013] In order to solve the above problems, the inventors investigated the causes of the above problems and found that the above problems could be solved by not knurling the film roll and making the thickness of the void layer between the films around the core thicker than the thickness of the void layer around the outer edge of the roll, thus leading to the present invention. In other words, the above-mentioned problems according to the present invention are solved by the following means.

[0014] 1. A film roll without a knurled section, wherein when the thickness of the void layer between adjacent films in the periphery of the winding core is measured on the side surface in the width direction of the film roll, and the thickness of the void layer between adjacent films in the periphery outside the winding is measured, Y is the value of the void layer between adjacent films, and X and Y satisfy the relationship given by the following formula (1).

[0015] Equation (1): Y <X

[0016] 2. The film roll according to paragraph 1, characterized in that X [μm] and Y [μm] satisfy the following formulas (2) and (3).

[0017] Equation (2): 0.05 < Y < 0.50 Equation (3): 1 < (X / Y) < 3

[0018] 3. A method for manufacturing a film roll that does not have a knurled section, characterized in that when the thickness of the void layer between adjacent films in the peripheral portion of the winding core is measured on the side surface in the width direction of the film roll, and the thickness of the void layer between adjacent films in the peripheral portion outside the winding is measured, X and Y are adjusted to satisfy the relationship of formula (1) below.

[0019] Equation (1): Y <X

[0020] 4. The method for manufacturing a film roll according to paragraph 3, characterized in that X [μm] and Y [μm] are adjusted to satisfy the following formulas (2) and (3).

[0021] Equation (2): 0.05 < Y < 0.50 Equation (3): 1 < (X / Y) < 3

[0022] 5. A method for manufacturing a film roll according to paragraph 3 or 4, characterized in that the film touch pressure at the periphery of the winding core is adjusted to a range of 2 to 30 [N / m], the film touch pressure at the center of the winding is adjusted to a range of 3 to 40 [N / m], and the film touch pressure at the outer periphery of the winding is adjusted to a range of 5 to 55 [N / m]. 6. A polarizing plate characterized by comprising a portion of the film from the film roll described in paragraph 1 or 2.

[0023] 7. A display device characterized by comprising a portion of the film from the film roll described in paragraph 1 or 2. [Effects of the Invention]

[0024] The present invention provides 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, a method for manufacturing the same, a polarizing plate, and a display device. Although the mechanism by which the effects of this invention manifest or the mechanism of action are not yet clear, we speculate as follows.

[0025] The film roll of the present invention does not undergo knurling, and by making the thickness of the air gap layer between films around the core thicker than the thickness of the air gap layer around the outer edge of the roll, it is possible to prevent tape transfer marks caused by the films sticking together and to prevent chain-like film deformation (hereinafter also referred to as "chain-like deformation") caused by air leaks between the films.

[0026] As mentioned above, the "chain-like deformation" refers to the deformation (chain-like defects) of the film caused by the stress due to the film's own weight after winding and the stress that causes the film to stretch in the width direction.

[0027] Conventionally, if film rolls are knurled to increase the amount of air trapped between the films, the air gap between the films becomes thicker compared to when no such processing is applied. 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 even greater radial stress is applied when the film roll is subjected to a minor impact.

[0028] Furthermore, when radial stress is applied to the film, air escapes from between the films. As a result, knurled film rolls exhibit a greater change in the thickness of the void layer near the core compared to ordinary film rolls. This makes the films more likely to stick together, especially at the core, and leaves more tape transfer marks at the core due to this sticking.

[0029] Furthermore, in film rolls that have undergone knurling, the film is supported only by the knurled portion. As a result, the restraining force to prevent misalignment is applied to the knurled portion, causing uneven stress on the film. This leads to uneven air release between the film layers and an uneven thickness of the void layer, making chain-like deformation more likely during long-term storage.

[0030] In contrast, the film roll of the present invention has no knurled portion, and the entire film is supported by the minute contact surfaces between the films or by the gas (e.g., air) in the void layer. Therefore, the restraining force to prevent winding misalignment is not unevenly distributed, and the stress on the film becomes uniform.

[0031] 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 inherent to the film. Therefore, if numerous protrusions on the opposing surfaces of adjacent films are in contact with each other at various points, the entire minute contact surface of these protrusions may be supporting the film.

[0032] In other words, for example, because parts of the protrusions are in contact, the films are not supported solely by the void layer, such as the air layer, but also by multiple contact points caused by these minute irregularities.

[0033] Furthermore, by making the air gap layer thicker in the core portion to allow for the intake of an appropriate amount of air, even if more air escapes during long-term storage of the film roll, particularly in the core portion, the unevenness in the thickness of the air gap layer throughout the film roll is minimized, and a uniform thickness of air gap layer is formed between the film layers. As a result, it is presumed that when the film roll is unwound, no tape transfer marks remain and there is no chain-like deformation. [Brief explanation of the drawing]

[0034] [Figure 1] Schematic diagram showing the positional relationship between the side surface of the film roll in the width direction and the imaging device. [Figure 2] A schematic diagram showing the widthwise side of a film roll as viewed from a plane perpendicular to that side. [Figure 3] Processed image for calculating the thickness of the void layer [Figure 4] A simplified conceptual diagram of a portion of the side surface in the width direction of a film roll to explain the core periphery, the center of the winding, and the outer periphery of the winding. [Figure 5] Schematic diagram of the internal structure of the imaging unit [Figure 6] Schematic diagram of the imaging device system configuration [Figure 7] A flowchart illustrating the manufacturing process of the solution casting method. [Figure 8] Schematic diagram of an apparatus for manufacturing films by solution casting. [Figure 9] A schematic plan view showing the internal structure of the tenter extension device. [Figure 10] Plan view showing the tenter extension device with the cover removed. [Figure 11] Schematic diagram of the nozzle and heater installation area, viewed from the front, showing the three zones inside the tenter extension device. [Figure 12] Side view of the three zones inside the tenter extension device. [Figure 13] A schematic diagram showing the process of winding the film and a cross-section of the film roll of the present invention after winding. [Figure 14]A flowchart showing the manufacturing process flow of the molten casting method. [Figure 15] Schematic diagram of an apparatus for manufacturing film by the molten casting method. [Figure 16] A schematic diagram showing an example of the configuration of the liquid crystal display device of the present invention. [Modes for carrying out the invention]

[0035] The film roll of the present invention is a film roll without a knurled section, characterized in that when the thickness of the void layer between adjacent films in the peripheral area of ​​the winding core is measured on the side surface in the width direction of the film roll, and the thickness of the void layer between adjacent films in the peripheral area outside the winding is Y [μm], then X and Y satisfy the relationship given by formula (1). The above features make it possible to solve the problems of the present invention.

[0036] Furthermore, the present invention relates to a method for manufacturing a film roll that does not have a knurled section, characterized in that when the thickness of the void layer between adjacent films in the peripheral portion of the winding core is measured on the side surface in the width direction of the film roll, and the thickness of the void layer between adjacent films in the peripheral portion outside the winding is measured as X [μm], X and Y are adjusted to satisfy the relationship of formula (1). The two features described above are technical features common to or corresponding to each of the embodiments (appearances) described below.

[0037] In embodiments of the present invention, it is preferable that X [μm] and Y [μm] satisfy formulas (2) and (3) above, from the viewpoint of forming a uniform void layer during long-term storage.

[0038] From the viewpoint of forming a uniform void layer during long-term storage, it is preferable to adjust X[μm] and Y[μm] so that they satisfy formulas (2) and (3).

[0039] From the viewpoint of forming a uniform void layer during long-term storage, it is preferable to adjust the film touch pressure in the peripheral part of the winding core to a range of 2 to 30 [N / m], the film touch pressure in the center of the winding to a range of 3 to 40 [N / m], and the film touch pressure in the peripheral part outside the winding to a range of 5 to 55 [N / m].

[0040] A portion of the film in the film roll of the present invention can be suitably used by being incorporated into a polarizing plate.

[0041] A portion of the film in the film roll of the present invention can be suitably used by being incorporated into a display device.

[0042] The present invention, its components, and embodiments and models for carrying out the present invention will be described in detail below. In this application, "~" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0043] 1. Film roll (1.1 Overview of film rolls) The film roll of the present invention is a film roll without a knurled section, and is characterized in that when the thickness of the void layer between adjacent films in the peripheral area of ​​the winding core is measured on the side surface in the width direction of the film roll, and the thickness of the void layer between adjacent films in the peripheral area outside the winding is Y [μm], then X and Y satisfy the relationship given by the following formula (1).

[0044] Equation (1): Y <X

[0045] The film roll of the present invention ("film roll" means a film wound into a roll shape) has no knurled sections (also called "knurled sections"), and as described above, the film is supported by the gas (e.g., air) in the gaps between adjacent films or by the entire minute contact surface between the films. Therefore, the restraining force to prevent winding misalignment is not unevenly distributed, and the stress on the film becomes uniform.

[0046] Furthermore, by making the air gap layer thicker in the core portion to allow for the incorporation of an appropriate amount of air, even if more air escapes during long-term storage of the film roll, particularly in the core portion, the unevenness in the thickness of the air gap layer throughout the film roll is minimized, and a uniform air gap layer is formed between the film layers. As a result, when the film roll is unwound, no tape transfer marks remain and there is no chain-like deformation.

[0047] In embodiments of the present invention, it is preferable that X [μm] and Y [μm] satisfy formulas (2) and (3) above, from the viewpoint of forming a uniform void layer during long-term storage.

[0048] (1.2) Gap layer between films (1.2.1) Means for controlling the thickness of the void layer The film roll of the present invention has a thicker void layer at the core to allow an appropriate amount of air to be incorporated. This minimizes unevenness in the thickness of the void layer throughout the film roll, even if a larger amount of air escapes from the core during long-term storage, thereby forming a uniform void layer between the film layers.

[0049] Such means include, for example, means of changing the film touch pressure using a touch roller, and means of changing the winding tension, winding speed, and roller angle. The above-mentioned touch rollers may be in multiples and may be chrome-coated as a surface treatment. Furthermore, elastic rollers or the like can also be used as the touch rollers mentioned above.

[0050] (1.2.2) Method for calculating the thickness of the void layer Figure 1 is a schematic diagram showing the positional relationship between the side surface of the film roll in the width direction and the imaging device. As shown in Figure 1, the imaging device (E) is installed on the side in the width direction of the film roll (30) wound on the core (R). Note that TD in Figure 1 represents the width direction of the film roll.

[0051] The following describes an example of a method for photographing the side surface of a film roll in the width direction using the above-mentioned imaging device, and a method for calculating the thickness of the void layer.

[0052] An imaging unit (U), which is part of the imaging device, photographs the side surface of the film roll in the width direction, centered on an arbitrary point (P) on the side surface of the film roll, and acquires image data for calculating the gaps between the film.

[0053] Figure 2 is a schematic diagram showing the widthwise side of a film roll as viewed from a plane perpendicular to that side.

[0054] Here, as shown in Figure 2, when the winding diameter is expressed as a percentage from the core surface (S0) to the outermost film layer (S4) of the film roll, the winding diameter at the core surface (S0) is 0%, and the winding diameter at the outermost film layer (S4) of the film roll is 100%.

[0055] When photographing the area around the winding core, take a picture of the position where the winding diameter is 20% (P 20 The image data is obtained by photographing the side portion, centering on the ) part.

[0056] When photographing the center of the winding, take a picture of the position where the winding diameter is 50% (P 50 When photographing the side portion centered on ) and the outer peripheral portion of the winding, the position where the winding diameter is 80% (P 80 The image data is obtained by photographing the side portion, centering on the ) part.

[0057] Subsequently, 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 the winding core periphery, winding center, and winding outer periphery of the film roll's width direction is then calculated.

[0058] Since the thickness of the void layer between films is calculated in three regions—the periphery of the winding core, the center of the winding, and the outer periphery of the winding—before providing specific examples for calculating the void layer thickness, we will first explain the concepts of these three regions.

[0059] Figure 4 is a simplified conceptual diagram of a portion of the side surface in the width direction of a film roll, illustrating the core periphery, the center of the winding, and the outer periphery of the winding.

[0060] In Figure 4, when the film layer directly wound onto the core (R) and attached to the core surface (S0) (not shown) is defined as S1, and the outermost layer of the film roll is defined as S4, the region from S1 to S4 is divided into three equal regions. The region on the core side is defined as the core peripheral region (A), the region outside the winding is defined as the outer peripheral region (C), and the region between the core peripheral region (A) and the outer peripheral region (C) is defined as the winding center region (B). Furthermore, the film layer forming the boundary between the core periphery (A) and the center of the winding (B) is denoted as S2, and the film layer forming the boundary between the center of the winding (B) and the outer periphery (C) is denoted as S3.

[0061] A specific example of a method for calculating the thickness of the void layer around the winding is the following:

[0062] (Specific example of a method for calculating the thickness of the void layer) For example, in calculating the thickness of the void layer around the core, the aforementioned position (P 20 The film roll's horizontal side is photographed with the center (P) as the focal point, and image data is obtained to calculate the gap between the films. Then, edge enhancement processing is performed on the obtained image data to obtain a processed image as shown in Figure 3, and the center of the processed image (P) is photographed. 20 Starting from point ( ), the radial length is measured with the film wound perpendicular to the surface and ending at the point at the 100th layer outwards. The thickness X [μm] of the void layer is then calculated using the following formula (A).

[0063] Thickness X [μm] of the void layer in formula (A) = {Length in the radial direction [μm] - (Average thickness per layer of the film layer measured by a film thickness gauge [μm]) × (Number of layers)} ÷ (Number of layers)

[0064] In addition, the (number of layers) in the above formula is determined by whether the end point is on the film surface and perpendicular to it, and which layer it is when winding outward. When it is in the 100th layer as described above, (number of layers) = 100.

[0065] In calculating the thickness of the void layer at the center of the winding, it is calculated in the same manner as above except that the aforementioned position (P 20 ) is changed to the position (P 50 ). In the thickness of the void layer at the outer peripheral edge of the winding, it is calculated in the same manner as above except that the aforementioned position (P 20 ) is changed to the position (P 80 ).

[0066] In addition, since the total length of the film roll is short, when photographing the side surface in the width direction of the film roll with an arbitrary point (P) as the center, if there are not 10 layers, for example, if there are only 70 layers when winding outward perpendicular to the film surface, measure the radial length with the point at the position of the 70th layer as the end point, and calculate the thickness X [μm] of the void layer using the above formula (A).

[0067] As the film thickness gauge 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.

[0068] (System configuration of the imaging unit and the imaging device) As the imaging unit, one with the following configuration was used. Fig. 5 is a schematic diagram of the internal configuration of the imaging unit (U). In Fig. 5, S is the measured surface (side surface in the width direction) of the film roll. The main components in Fig. 5 are as follows.

[0069] 〈Components〉 · Total reflection mirror (60) · Half mirror (61) • Telecentric lens (62) (MML1-HR130VI-35F: Manufactured by Moritex Co., Ltd., magnification x1, WD130mm) • High-brightness line lighting (63) (LNSP2-100SW: Manufactured by CCS Corporation) • Monochrome line sensor camera (64) (RMSL8K39CL: Manufactured by Nippon Electro Devices Co., Ltd., 8000 pixels with 3.5 μm / pixel)

[0070] Furthermore, the system configuration of the imaging device is shown in the schematic diagram in Figure 6.

[0071] 2. Method for manufacturing film rolls The present invention relates to a method for manufacturing a film roll that does not have a knurled section, characterized in that when the thickness of the void layer between adjacent films in the peripheral portion of the winding core is measured on the side surface in the width direction of the film roll, and the thickness of the void layer between adjacent films in the peripheral portion outside the winding is measured as X [μm], X and Y are adjusted to satisfy the relationship of formula (1).

[0072] In the above-described method for manufacturing a film roll, it is preferable from the viewpoint of forming a uniform void layer during long-term storage to adjust X [μm] and Y [μm] so that they satisfy formulas (2) and (3).

[0073] Furthermore, from the viewpoint of forming a uniform air layer during long-term storage, it is preferable to adjust the film touch pressure in the peripheral area of ​​the winding core to a range of 2 to 30 [N / m], the film touch pressure in the center of the winding to a range of 3 to 40 [N / m], and the film touch pressure in the peripheral area outside the winding to a range of 5 to 55 [N / m].

[0074] While conventional manufacturing methods such as inflation, T-die, calendering, cutting, casting, emulsion, and hot pressing can be used to produce the film rolls of the present invention, solution casting and molten casting are preferred from the viewpoint of suppressing discoloration, foreign matter defects, and optical defects such as die lines. Solution casting is particularly preferred for achieving a uniform film surface.

[0075] (2.1) Solution casting method Figure 7 is a flowchart showing the flow of the solution casting film manufacturing process, and Figure 8 is a schematic diagram of the apparatus used to manufacture films by the solution casting film manufacturing method.

[0076] The solution casting method will be explained below with reference to Figures 7 and 8. The method for manufacturing a film by solution casting includes a dope preparation step [S1], a casting step [S2], a peeling step [S3], a shrinking step [S4], a first drying step [S5], a first stretching step [S6], a first cutting step [S7], a second stretching step [S8], a second cutting step [S9], a second drying step [S10], a third cutting step [S11], and a winding step [S12].

[0077] Furthermore, the above manufacturing method does not need to include both the first drying step [S5] and the second drying step [S10]; it is sufficient to include at least one of these steps. Furthermore, the process may include a first stretching step [S6], a second stretching step [S8], and any of the first cutting step [S7], second cutting step [S9], and third cutting step [S11].

[0078] (2.1.1) Dope preparation (stirring preparation) process [S1] The dope preparation process will be described below as an example of a case in which a cycloolefin resin (hereinafter also referred to as "COP") is used as the thermoplastic resin, as an embodiment of the present invention, but the present invention is not limited thereto.

[0079] In the dope preparation (agitation preparation) step [S1] shown in Figure 7, at least the resin and solvent are agitated in the agitation tank (1a) of the agitation device (1) shown in Figure 8 to prepare the dope to be cast onto the support (3) (endless belt).

[0080] (solvent) As the solvent mentioned above, a mixed solvent of a good solvent and a poor solvent is used. This process involves dissolving the COP, and optionally other compounds, in a dissolution vessel while stirring, in a solvent mainly composed of a good solvent for COP, to form a dope, or, optionally, mixing other compound solutions with the COP solution to form a dope, which is the main dissolving solution.

[0081] From the viewpoint of reducing the drying load after casting the dope onto the support, a higher concentration of COP in the dope is preferable. However, if the concentration is too high, the load during dope filtration increases, resulting in poor accuracy. Therefore, it is necessary to achieve both the reduction of the drying load and the suppression of the load during filtration. To achieve both of these conditions, the concentration of COP in the dope is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 30% by mass. Furthermore, it is preferable that the dope contains water in the range of 0.01 to 2% by mass.

[0082] The solvents used in doping may be used alone or in combination of two or more, but it is preferable in terms of production efficiency to use a mixture of a good solvent and a poor solvent for COP, and a higher proportion of the good solvent is preferable in terms of COP solubility.

[0083] The preferred mixing ratio of the good solvent to the poor solvent is within the range of 70-98% by mass for the good solvent and within the range of 2-30% by mass for the poor solvent.

[0084] In this specification, a "good solvent" for COP is defined as one that dissolves the COP being used on its own, and a "poor solvent" for COP is defined as one that swells or does not dissolve the COP being used on its own. Therefore, the goodness or poorness of a solvent depends on the average degree of substitution of the above COP.

[0085] The good solvent used in the present invention is not particularly limited, but examples include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc., and methylene chloride or methyl acetate are particularly preferred.

[0086] The poor solvent used in the present invention is not particularly limited, but methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, and the like are preferably used.

[0087] Furthermore, the solvent used to dissolve COP is recovered from the film by drying at each step of the process and reused.

[0088] The recovered solvent may contain trace amounts of additives added to COP, such as plasticizers, UV absorbers, resins, and monomer components. However, even if these are present, it can still be reused, and if necessary, it can be purified and reused.

[0089] (Dissolution method) As described above, a general method can be used for dissolving COP when preparing the dope. Specifically, methods performed at atmospheric pressure, methods performed below the boiling point of the main solvent, and methods performed under pressure above the boiling point of the main solvent are preferred. Combining heating and pressurization allows heating to exceed the boiling point at atmospheric pressure.

[0090] Furthermore, a method of dissolving by stirring while heating at a temperature above the boiling point of the solvent at atmospheric pressure, but within a range where the solvent does not boil under pressure, is also preferable in order to prevent the formation of gels or lumpy undissolved matter called "mamako."

[0091] Another preferred method involves mixing COP with a poor solvent to wet or swell it, and then adding a good solvent to dissolve it.

[0092] Pressurization may be carried out by injecting an inert gas such as nitrogen gas, or by increasing the vapor pressure of the solvent through heating. Heating is preferably performed from an external source; for example, a jacket-type heater is preferable because it allows for easy temperature control.

[0093] When adding a solvent, a higher heating temperature is preferable from the standpoint of COP solubility, but if the heating temperature is too high, the required pressure increases, resulting in poor productivity.

[0094] The preferred heating temperature is in the range of 30 to 120°C, more preferably in the range of 60 to 110°C, and even more preferably in the range of 70 to 105°C. Furthermore, the pressure is adjusted so that the solvent does not boil at the set temperature.

[0095] Alternatively, a cooling dissolution method is also preferably used, which allows COP to be dissolved in a solvent such as methyl acetate.

[0096] (filtration) Next, it is preferable to filter this COP solution (dope during or after dissolution) using a suitable filter material such as filter paper.

[0097] For filter media, a low absolute filtration accuracy is preferable in order to remove insoluble matter, but if the absolute filtration accuracy is too low, there is a problem that the filter media is prone to clogging. Therefore, filter media with an absolute filtration accuracy of 0.008 mm or less are preferred, filter media in the range of 0.001 to 0.008 mm are more preferred, and filter media in the range of 0.003 to 0.006 mm are even more preferred.

[0098] There are no particular restrictions on the material of the filter media, and ordinary filter media can be used, but plastic filter media such as polypropylene and Teflon (registered trademark), or metal filter media such as stainless steel are preferred because they do not shed fibers.

[0099] It is preferable to remove or reduce impurities, particularly bright spot contaminants, contained in the COP of the raw material by filtration.

[0100] Bright spot foreign matter refers to a point (foreign matter) that appears when light leaks from the opposite side when light is shone from one polarizing plate side onto a film or similar material placed between two polarizing plates in a crossed nicol state and observed from the other polarizing plate side. This bright spot foreign matter has a diameter of 0.01 mm or more and the number of bright spots is 200 / cm². 2 The following is preferable: Comfortable 100 pieces / cm 2 The following is more preferably 50 pieces / m 2 The following is more preferably 0 to 10 pieces / cm 2 The following applies: Furthermore, it is preferable to have fewer bright spots smaller than 0.01 mm.

[0101] While dope filtration can be performed by conventional methods, a method that involves filtration while heating the solvent at a temperature above its boiling point at atmospheric pressure, but within a range where the solvent does not boil under pressure, is preferable because it results in a smaller increase in the difference in filtration pressure before and after filtration (called differential pressure).

[0102] The preferred temperature range is 30 to 120°C, more preferably 45 to 70°C, and even more preferably 45 to 55°C.

[0103] A lower filtration pressure is preferable. 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.

[0104] (2.1.2) Casting process [S2] In the casting process [S2] shown in Figure 7, the dope prepared in the dope preparation process [S1] is delivered to the casting die (2) shown in Figure 8 via a conduit through a pressurized metering gear pump or the like. The dope is then cast from the casting die (2) to the casting position on a support (3) made of an endlessly rotating stainless steel belt, forming a cast film (5).

[0105] In this case, the inclination of the casting die (2), that is, the direction of dope discharge from the casting die (2) to the support (3), should be appropriately set so that the angle with respect to the normal of the surface of the support (3) (the surface to which the dope is cast) is within the range of 0 to 90°.

[0106] Subsequently, the cast film (5) is heated and dried on the support (3), and the solvent is evaporated until the cast film (5) can be peeled off the support (3) by the peeling roller (4). In this invention, the term "cast film" refers to the doped film cast from the lip portion described above.

[0107] The above evaporation is preferably carried out in an atmosphere within the range of 5 to 75°C. To evaporate the solvent, there are several methods, including applying hot air to the upper surface of the cast film (5), transferring heat from the back surface of the support (3) using a liquid, and transferring heat from both sides by radiant heat. However, the method of transferring heat from both sides by radiant heat is preferable because it offers good drying efficiency. Furthermore, methods that combine these methods are also preferred.

[0108] From a productivity standpoint, the width of the casting should preferably be 1.3m or more. More preferably, it is in the range of 1.3 to 4.0 m. If the width of the cast does not exceed 4.0m, stripes will not form during the manufacturing process, and stability will be increased during the subsequent transport process. From the standpoint of transportability and productivity, a range of 1.3 to 3.0 m is even more preferable.

[0109] (Ryuen Dai) Dies used for casting include coat hanger dies and T-dies, all of which are preferred.

[0110] For those skilled in the art to improve the uniformity of film thickness in the casting process, one method is to control the slit gap (the tip opening of the liquid discharge port at the slit nozzle) of the lip portion of the casting die (the portion of the casting die slit where the dope comes out) in both solution casting and molten casting methods.

[0111] For example, when extruding a highly viscous dope (including melt), variations in the width of the slit gap occur. To prevent this, multiple heat bolts are installed to control the width of the slit gap.

[0112] However, this method has the problem of being limited by the physical installation constraints of the heat voltage. Furthermore, while there is a method to suppress pressure fluctuations in the width of the slit gap that cause variations in the width of the slit gap by changing the internal structure of the casting die in terms of width, this method has the problem of requiring the casting die to be switched for each product type, which is time-consuming and costly.

[0113] The casting die is equipped with a mechanism to adjust the width of the slit through which the dope is discharged (or extruded in the case of molten resin). It is preferable to use the heat bolts of the casting die to adjust the gap between the width of the slits through which the dope is discharged, thereby controlling the initial discharge thickness of the cast film by adjusting the film thickness deviation immediately after discharge to within a range of 1.0 to 5.0% relative to the entire cast film.

[0114] To increase the film formation speed of the film according to the present invention, two or more of the above-mentioned casting dies may be provided on a support, and the doping amount may be divided and layered. Alternatively, it is preferable to obtain a laminated film roll by a co-casting method in which multiple dopes are cast simultaneously. To increase the film formation rate, two or more casting dies may be provided on the support, and the doping amount may be divided and layered.

[0115] (Support) The support (3) is preferably made of, for example, a stainless steel belt or a drum with a plated surface made of cast iron, and is held by a pair of rollers (3a), a roller (3b), and a plurality of rollers located between them. In this case, it is preferable that the surface of the support is mirror-like.

[0116] One or both of the rollers (3a) and (3b) are equipped with a drive device that applies tension to the support (3), thereby ensuring that the support (3) is used in a taut, tensioned state.

[0117] The surface temperature of the support (3) in the casting process [S2] is within the range of -50°C to the boiling point of the solvent, and a higher temperature is preferable because it allows for a faster drying rate of the cast film.

[0118] The preferred support temperature is in the range of 0 to 55°C, and more preferably in the range of 22 to 50°C.

[0119] Note that the temperature of the support may be the same throughout, or it may vary depending on the location.

[0120] The method for controlling the temperature of the support (3) is not particularly limited, but methods include blowing hot or cold air onto it, or bringing hot water into contact with the back of the support. Using hot water is preferable because it allows for more efficient heat transfer, thus shortening the time it takes for the support temperature to stabilize. When using warm air, it is sometimes necessary to use air at a temperature higher than the target temperature.

[0121] (2.1.3) Peeling process [S3] In this process, during the casting process [S2], the solvent is evaporated on the support (3) until the cast film (5) has sufficient film strength to be peeled off, and after drying and solidifying or cooling and solidifying, the film is peeled off the support (3) before the film completes a full circuit around the support (3). In other words, this process involves peeling off the film, from which the solvent has evaporated on the support (3), at the peeling position. In this case, from the viewpoint 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.

[0122] In the peeling process [S3], the film is peeled off by a peeling roller (4) (a roll that assists in peeling off the film) while maintaining its self-supporting properties. The temperature at the peeling site 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.

[0123] (Amount of residual solvent) The amount of residual solvent on the support (3) during peeling in the peeling process [S3] is appropriately adjusted depending on the strength of the drying conditions, the length of the support (3), etc., and the amount of residual solvent in the shrinking process [S4] is greatly influenced by the thickness of the film, the resin, etc., so there is an overlap in the preferred range of residual solvent amounts between the peeling process [S3] and the shrinking process [S4].

[0124] The amount of residual solvent in the film varies depending on the film thickness, but if there is too much residual solvent at the delamination point (the position where the film is peeled from the support), the film may become too soft and difficult to peel, which can impair flatness and make it more prone to horizontal stripes, kinks, and vertical streaks due to peel tension. Conversely, if the amount of residual solvent is too low, parts of the film may peel off during the process.

[0125] From the above perspective, in order for the film to exhibit good flatness, it is desirable that the residual solvent content be in the range of 10 to 50% by mass, considering the balance between economic speed and quality.

[0126] One method for increasing the film formation rate (by removing the film while the residual solvent is still present as much as possible) is gel casting, which allows for removal even with a large amount of residual solvent.

[0127] The methods described above include adding a poor solvent relative to COP during doping, gelling the cast film after doping and casting, and gelling the cast film by cooling the support, allowing it to be peeled off while containing a large amount of residual solvent. Another method involves adding metal salts during the doping process.

[0128] 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 formation rate can be increased.

[0129] The amount of residual solvent is defined by the following formula.

[0130] Formula: Residual solvent amount [mass%] = {(MN) / N} × 100

[0131] In the above formula, M is the mass of a sample taken at any point during or after the production of the cast film or film, and N is the mass of M after heating at 115°C for 1 hour.

[0132] (Peeling tension) The peeling tension when separating the support from the film is preferably 300 N / m or less. More preferably, the tension is in the range of 196 to 245 N / m, but if wrinkles are likely to form during peeling, it is preferable to peel with a tension of 190 N / m or less.

[0133] (2.1.4) Shrinkage process [S4] The shrinkage process [S4] is a process of shrinking the film (F) in the width direction within the plane. Methods for shrinking the film (F) include, for example, treating the film at a high temperature without holding its width to increase its density; applying tension to the film after peeling it from the support in the transport direction (Machine Direction, hereinafter also referred to as the "MD direction") to stretch and shrink it in the width direction (TD direction) perpendicular to the MD direction within the film surface; and drastically reducing the amount of residual solvent in the film. In this case, the film shrinks in the traverse direction (hereinafter also referred to as the "TD direction") perpendicular to the MD direction within the film plane.

[0134] The shrinkage process promotes entanglement between resin molecules (matrix molecules) in the thickness direction of the film. For example, when bonding the film to a polarizer via an adhesive during the production of a polarizing plate, the adhesive can more easily penetrate into the film through the entangled parts (crosslinked parts) between the matrix molecules. As a result, the film can be firmly fixed to the polarizer via the adhesive, improving the peel strength of the film from the polarizer. In other words, good adhesion between the film and the polarizer can be ensured.

[0135] (Definition of contraction rate) In this invention, the shrinkage rate is defined by the following formula.

[0136] Formula: Shrinkage rate [%] = Film width at the end of the shrinkage process [mm] / Film width at the start of the shrinkage process [mm] × 100

[0137] In the shrinkage process [S4], if the shrinkage rate of the film is too low, the effect of promoting entanglement between matrix molecules will be insufficient, and if it is too high, there is a concern that the production efficiency of the film (stretched film) will decrease. Therefore, the shrinkage rate of the film in the shrinkage process [S4] is preferably in the range of 1 to 40%, and more preferably in the range of 5 to 20%.

[0138] (Methods for measuring and calculating shrinkage rate) The film width can be measured using the LS-9000 manufactured by Keyence Corporation. The shrinkage rate of the film according to the present invention was determined by taking the average value of the film width measured every second for 5 minutes (300 seconds) using the above measuring instrument, and substituting this value into the above formula. However, the method is not limited to the above method; for example, the film width may be determined by reading a value from a ruler and substituting this value into the above formula.

[0139] (2.1.5) First drying step [S5] In the first drying step [S5], the film (F) is heated on a support by a drying device (6) to evaporate the solvent and dry the film.

[0140] In the drying apparatus (6) shown in Figure 8, the film (F) is transported by multiple conveyor rolls arranged in a staggered pattern when viewed from the side, and the film (F) is dried in between.

[0141] There are no particular restrictions on the drying method within the drying apparatus (6). Generally, the film (F) is dried using hot air, infrared rays, heated rolls, microwaves, etc. However, for simplicity, drying the film (F) with hot air is preferred. Combining these methods is also preferable. The first drying step [S5] may be performed as needed.

[0142] Thinner films dry faster, but excessively rapid drying can easily impair the flatness of the finished film. When drying films at high temperatures, it is necessary to consider the amount of residual solvent before drying. However, by keeping the amount of residual solvent below a certain level, it is possible to prevent malfunctions caused by solvent foaming.

[0143] 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 entire drying process. Drying is particularly preferred within the range of 35 to 200°C, and it is preferable to gradually increase the drying temperature.

[0144] Generally, film drying methods include the roll drying method (a method in which the film is passed alternately through multiple rolls arranged vertically) or the tenter method, which involves transporting the film while drying it.

[0145] When using a tenter stretching device for drying the film, it is preferable to use a device that allows for independent control of the gripping length (distance from the start of gripping to the end of gripping) of the film on the left and right sides using the left and right gripping means of the tenter stretching device during the stretching process described later. Furthermore, in the stretching process, it is preferable to intentionally create sections with different temperatures in order to improve flatness.

[0146] Furthermore, it is preferable to establish a neutral zone between different temperature zones to prevent interference between them.

[0147] (2.1.6) First stretching process [S6] The first stretching step [S6] may be a step of stretching the film (F) only in the MD direction within the film plane, or a step of stretching only in the TD direction, or a step of stretching in both the MD and TD directions, or a step of stretching in an oblique direction. Furthermore, although there are no limitations on the stretching direction, from the viewpoint of obtaining a wide film, it is preferable to have a process that includes stretching in at least the width direction. Such stretching is performed by a stretching device (7).

[0148] (Stretching method) Stretching methods include stretching in the transport direction (longitudinal direction of the film; film formation direction; casting direction; longitudinal direction; MD direction) by creating a difference in peripheral speed of the rolls (longitudinal stretching), stretching in the width direction (orthogonal direction within the film plane; width direction of the film; transverse direction; TD direction) by fixing both side edges of the film (F) with clips or the like (transverse stretching), performing longitudinal stretching and transverse stretching sequentially (sequential biaxial stretching), and performing longitudinal stretching and transverse stretching simultaneously (simultaneous biaxial stretching). Of these, a tenter stretching device is used for transverse stretching and simultaneous biaxial stretching (including oblique stretching). 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 between these clips as they move along with the film.

[0149] Among the methods described above, the so-called tenter method, which uses a tenter stretching device, is preferred for improving the performance, productivity, flatness, and dimensional stability of the film.

[0150] Furthermore, in the case of the so-called tenter method, driving the clip portion with a linear drive system allows for smooth stretching, which is preferable because it reduces the risk of breakage and other problems.

[0151] These width maintenance or lateral stretching processes in the film formation process are preferably performed by a tenter stretching device, which may be either a pin tenter or a clip tenter. In addition to stretching, drying may also be performed inside the stretching apparatus (7).

[0152] (Stretching ratio) In order to ensure a high phase difference, a wide width, and to promote adhesive penetration when bonding with the polarizer, it is preferable to stretch the film at a high magnification during the stretching process. However, if the stretching ratio is too high, the stretching stress may cause crazing within the film, or the entanglement between matrix molecules that maintain film strength may dissociate, potentially weakening the film.

[0153] Therefore, the stretching ratio in the stretching process is preferably in the range of 1.1 to 5.0 times, and more preferably in the range of 1.3 to 3.0 times.

[0154] In this invention, "stretching ratio" refers to the ratio [%] of the area of ​​the film after stretching to the area of ​​the film before stretching. In other words, the "stretching ratio" in the stretching process described above is preferably within the range of 1.1 to 5.0 times, and more preferably within the range of 1.3 to 3.0 times, when the total stretching ratio due to stretching in the longitudinal (longitudinal) and transverse (width) directions of the film is expressed as an area ratio.

[0155] Furthermore, if stretching is performed multiple times, it is preferable that the stretching at the highest magnification, which carries the highest risk of matrix molecule dissociation, be performed in the final stretch. For example, in Figure 7, it is preferable that the highest magnification stretching is performed in the second stretching step. In this case, the entanglement of matrix molecules can be strengthened before the maximum stretching is achieved, so even when stretching is performed at the maximum magnification, the dissociation of the matrix molecules can be suppressed, thereby preventing aggregate breakdown.

[0156] (Tenter extension device) The following explanation will use the case where a tenter stretching device is used as the stretching device (7) as an example, with reference to Figures 9, 10, 11, and 12.

[0157] Figure 9 is a schematic plan view showing the internal structure of the tenter stretching device, and is a cross-sectional view of the tenter stretching device viewed from above with a plane perpendicular to the film surface. Figure 10 shows the tenter extension device with the cover removed, and the cover is indicated by a dashed line.

[0158] Figure 11 is a schematic diagram of the nozzle and heater installation areas in the three zones within the tenter stretching device, viewed from the front. As shown in Figure 11, the infrared (IR) heater is positioned only above the nozzle to prevent the film from coming into contact with the infrared (IR) heater when the film is torn. However, bringing the infrared (IR) heater closer to the film allows the radiant energy from the infrared (IR) heater to be concentrated in a narrower area. Therefore, the infrared (IR) heater should be brought as close to the film as possible without interfering with the widthening operation by the clip.

[0159] Note that Figure 11 mainly shows heat treatment from the central nozzle (105), and in this embodiment, heat treatment is not performed using the end nozzle (104), however, it is possible to use both in this embodiment.

[0160] When performing heat treatment, having an infrared (IR) heater emitted from the nozzle gap, as shown in Figure 12, allows for more efficient transfer of radiant energy to the film.

[0161] As shown in Figure 9, the infrared (IR) heaters were arranged in rows so that the entire width of the film could be heated even before stretching. The heaters may also be arranged in a staggered pattern along the length of the unit.

[0162] The tenter stretching device (40) is equipped with a 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. The endless chain (48) is positioned on both sides of the film (F), 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 the driving sprocket (50) is rotated by driving this motor. As a result, the endless chain (48) travels in a circular motion between the driving sprocket (50) and the driven sprocket (52), causing the clip (42) attached to the endless chain (48) to also travel in a circular motion.

[0163] A rail (54) is provided between the driving sprocket (50) and the driven sprocket (52) to guide the endless chain (48) (or clip (42)). The rails (54) are arranged on both sides of the film (F), and the spacing between the rails (54) is configured to be wider on the downstream side than on the upstream side in the direction of film (F) transport. As a result, when the clips (42) travel in a circular motion, the distance between the clips (42) is increased, allowing the film (F) held by the clips (42) to be stretched laterally in the width direction.

[0164] An open member (56) is attached to both the driving sprocket (50) and the driven sprocket (52). The release member (56) is a device that displaces the flapper (not shown) of the clip (42), which will be described later, from the gripping position to the release position. This release member (56) automatically performs the gripping and release operations of the film (F).

[0165] Incidentally, as shown in Figures 9, 10, and 12, the inside of the tenter stretching device (40) is equipped with a preheating zone, a (lateral) stretching zone, and a heat setting zone. The zones are separated by windbreak curtains (not shown). Furthermore, within each zone, hot air is supplied to the film (F) from above, below, or both.

[0166] The hot air is blown uniformly across the width of the film (F) while maintaining a predetermined temperature for each zone. This allows the temperature inside each zone to be controlled to the desired level. The following describes each zone.

[0167] The preheating zone is a zone for preheating the film (F), and heats the film (F) without widening the spacing between the clips (42).

[0168] The film (F), which has been preheated in the preheating zone, moves to the (transverse) stretching zone. The (lateral) stretching zone is a zone in which the film (F) is stretched (laterally) in the width direction by widening the spacing between the clips (42). The stretching ratio in this (lateral) stretching process is preferably in the range of 1.0 to 2.5 times, more preferably in the range of 1.05 to 2.3 times, and even more preferably in the range of 1.1 to 2 times.

[0169] The film (F), which has been stretched laterally in the stretching zone, moves to the heat-setting zone.

[0170] In this embodiment, the inside of the tenter stretching device (40) is divided into a preheating zone, a (lateral) stretching zone, and a heat setting zone. However, the types and arrangement of the zones are not limited to these, and for example, a cooling zone for cooling the film (F) may be provided after the (lateral) stretching zone. Additionally, a thermal relaxation zone may be provided within the thermal fixation zone.

[0171] In this embodiment, only (lateral) stretching was performed with the tenter stretching device (40), but stretching in the vertical direction may also be performed simultaneously. In this case, when the clip (42) moves, the pitch of the clip (42) (the distance between the clips (42) in the transport direction) should be changed. For example, a pantograph mechanism or a linear guide mechanism can be used as a mechanism to change the pitch of the clip (42).

[0172] (Heat treatment timing) A tenter stretching apparatus is typically divided into multiple zones, such as a preheating zone for heating the film, a transverse stretching zone for stretching the film laterally, a heat-setting zone for crystallization of the film, and a relaxation zone for removing thermal stress from the film, as shown in Figures 9, 10, and 12.

[0173] (Furnace temperature) Typically, the furnace temperature is preferably in the range of 120 to 200°C, and more preferably in the range of 120 to 180°C. Here, "furnace temperature" refers to the temperature (H) measured at a position 100 mm above the center of the film immediately before stretching in the stretching zone of the tenter stretching apparatus described later. A It is defined as (=100mm), where the value of each temperature is measured every minute for one hour, and the average value of these values ​​is calculated.

[0174] Typically, the furnace temperature is preferably in the range of 120 to 200°C, and more preferably in the range of 120 to 180°C. In cases where a longitudinal temperature gradient is applied across multiple sections, the heat treatment section shall be the one to be considered.

[0175] Furthermore, the furnace temperature will differ depending on whether or not heat treatment is performed in the stretching zone. However, if heat treatment is performed in the stretching zone, the furnace temperature will refer to the furnace temperature in the stretching zone before the heat treatment is performed.

[0176] (Amount of residual solvent) The amount of residual solvent in the film during stretching is preferably 20% by mass or less, and more preferably 15% by mass or less.

[0177] (2.1.7) First cutting process [S7] In the first cutting step [S7], a cutting section (8) consisting of a slitter cuts both ends in the width direction of the film (F) that was stretched in the first stretching step [S6]. In the film (F), the portions remaining after cutting both ends constitute the product portion that becomes the film product. On the other hand, the portion cut from the film (F) may be recovered and reused again as part of the raw materials for film manufacturing.

[0178] (2.1.8) Second stretching process [S8] In the second stretching step [S8], the film (F) is stretched by the stretching device (9) in the same manner as in the first stretching step [S6]. In this case, preferred stretching methods include a stretching method that stretches the film in the transport direction (MD direction) by creating a difference in the peripheral speed of the rolls, and a tenter method that stretches the film in the width direction (TD direction) by fixing both side edges of the film (F) with clips or the like. These methods are preferable for improving the performance, productivity, flatness, and dimensional stability of the film. In addition to stretching, drying may also be performed inside the stretching apparatus (9).

[0179] (2.1.9) Second cutting process [S9] In the second cutting step [S9], a cutting unit (10) consisting of a slitter cuts both ends of the formed film (F) in the width direction, similar to the first cutting step [S7]. Note that the clip gripping portions at both ends of the film are usually cut off because the film is deformed and unusable as a product. If no material degradation has occurred due to heat, it will be reused after collection.

[0180] In the film (F), the portions remaining after cutting both ends constitute the product portion that becomes the film product. Meanwhile, the portions cut from the film (F) are collected and reused as part of the raw materials for film production.

[0181] (2.1.10) Second drying process [S10] In the second drying step [S10], the film (F) is dried in the drying apparatus (11) in the same manner as in the first drying step [S5]. Inside the drying apparatus (11), the film (F) is transported by multiple transport rolls arranged in a staggered pattern when viewed from the side, and the film (F) is dried in between.

[0182] There are no particular restrictions on the drying method in the drying apparatus (6), and generally include hot air, infrared radiation, heated rollers, and microwaves. Among the drying methods described above, the method of drying the film (F) with hot air is preferred due to its simplicity. The second drying step [S10] may be performed as needed.

[0183] (2.1.11) Third cutting process [S11] In the third cutting step [S11], a cutting section (12) consisting of a slitter cuts both ends of the formed film (F) in the width direction, similar to the first cutting step [S7] and the second cutting step [S9]. In the film (F), the portions remaining after cutting both ends constitute the product portion that becomes the film product. Meanwhile, the portions cut from the film (F) are collected and reused as part of the raw materials for film production.

[0184] (2.1.12) Winding process [S12] Finally, in the winding process [S12], the film (F) is wound up by the winding device (13) to obtain a film roll. In other words, in the winding process, a film roll is manufactured by winding the film (F) onto a core while it is being transported. The preferred range for the initial tension when winding the film during the winding process is within the range of 20 to 300 N / m.

[0185] Figure 13 is a schematic diagram showing the process of winding the film and a cross-section of the film roll of the present invention after winding. When winding the film (F), it is preferable to install a touch roller (33) as shown in Figure 13, for example, and to appropriately change the film touch pressure in order to form the desired void layer. In Figure 13, the formed film (31) is wound up by rollers (32) and touch rollers (33) and wound up as a film roll (30).

[0186] (Amount of residual solvent) More specifically, the process involves winding the film into a winding device (12) after the amount of residual solvent in the film has decreased to 2% by mass or less. 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 to wind the material so that the residual solvent content is within the range of 0.00 to 0.20% by mass.

[0187] (Winding method) The winding method for the film (F) can be done using a commonly used winder, and there are various methods for controlling the tension, such as the constant torque method, constant tension method, tapered tension method, and programmed tension control method with constant internal stress, which can be used as appropriate.

[0188] Before winding, the ends of the film may be slit and trimmed to the desired product width, and a surface modification treatment may be applied to both ends of the film to prevent sticking and scratching during winding.

[0189] (After winding) The film roll of the present invention is preferably a long film, specifically in the range of about 100 to 10,000 m, and is usually provided in roll form.

[0190] (2.2) Manufacturing process of film rolls by melt casting method The film according to the present invention can also be manufactured by a melt-flow molding method. The "melt film formation method" refers to a method in which a composition containing a thermoplastic resin and the aforementioned additives is heated and melted to a temperature at which it exhibits fluidity, and then the molten material containing the fluid thermoplastic resin is cast.

[0191] Molding methods involving heating and melting can be further classified into molten extrusion, press molding, inflation molding, injection molding, blow molding, and stretch molding. Among these molding methods, the melt extrusion method is preferred in terms of mechanical strength and surface accuracy.

[0192] Figure 14 is a flowchart showing the flow of the manufacturing process using the molten casting method. Figure 15 is a schematic diagram of an apparatus for manufacturing films using the melt casting method. The solution casting method will be explained below with reference to Figures 14 and 15.

[0193] The method for manufacturing a film roll by the melt casting film-forming method includes an extrusion step [M1], a casting and molding step [M2], a first stretching step [M3], a first cutting step [M4], a second stretching step [M5], a second cutting step [M6], and a winding step [M7].

[0194] Furthermore, the above manufacturing method does not need to include both the first stretching step [M3] and the second stretching step [M5]; it is sufficient to include at least one of these steps. Similarly, the first cutting process [M4] and the second cutting process [M6] only need to include at least one of the other processes.

[0195] (2.2.1) Extrusion process [M1] In the extrusion process [M1], at least the resin is melted and extruded in the extruder (14) and molded onto the cast drum (16). Details regarding the resins that can be used in the present invention will be described later.

[0196] Furthermore, it is preferable to pre-mix and pelletize the resin. Pelletization can be carried out using known methods.

[0197] For example, dry resin, plasticizers, and other additives can be supplied to an extruder via a feeder, mixed using a single-screw or twin-screw extruder, extruded in strand form from a casting die (15), water-cooled or air-cooled, and then cut to produce pellets.

[0198] The additive may be mixed with the resin before being supplied to the extruder, or the additive and resin may be supplied to the extruder separately using different feeders. Furthermore, it is preferable to mix small amounts of additives, such as particles and antioxidants, into the resin beforehand to ensure uniform mixing.

[0199] When introducing pellets from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition by drying, under vacuum, reduced pressure, or in an inert gas atmosphere.

[0200] The extruder should suppress shear force, allow for pelletization to prevent resin degradation (such as molecular weight reduction, discoloration, and gel formation), and preferably process at the lowest possible temperature.

[0201] For example, in the case of a twin-screw extruder, it is preferable to use a deep-groove type screw and rotate it in the same direction. Due to the need for uniform mixing, interlocking types are preferred. It is preferable to filter the resin pellets with a leaf disk type filter or the like during melting to remove foreign substances.

[0202] Using the pellets obtained as described above, film formation is carried out. Of course, it is also possible to directly supply the raw material resin (powder, etc.) to the extruder with a feeder without pelletizing and directly carry out film formation.

[0203] (2.2.2) Casting and forming process [M2] In the casting and forming process [M2], the resin pellets melted in the extrusion process are cast in a film shape from a casting die (15) through a pressure type metering gear pump or the like and transferred infinitely by a conduit to the casting position on a rotationally driven stainless steel endless casting drum (16). The melted resin pellets are cast from the casting die (15). Then, the cast molten resin pellets are formed on the casting drum (16) to form a cast film (18).

[0204] The inclination of the casting die (15), that is, the discharge direction of the molten resin pellets from the casting die (15) to the support (16), may be appropriately set within the range of 0 to 90° with respect to the normal of the surface of the casting drum (16) (the surface on which the molten resin pellets are cast).

[0205] A touch roller (16a) or a cooling drum (17) assisting the casting drum (16) may be appropriately used alone or in combination to form the film (F).

[0206] (2.2.3) First stretching process [M3] In the first stretching process [M3], the film (F) is stretched by a stretching device (19). As the stretching method at this time, a stretching method of stretching in the MD direction by providing a peripheral speed difference between rolls or a tenter method of stretching in the TD direction by fixing both side edges of the film (F) with clips or the like is preferable in order to improve the performance, productivity, flatness and dimensional stability of the film. In addition, in the stretching device (19), drying may be performed in addition to stretching.

[0207] Regarding the descriptions of the tenter stretching device, heat treatment timing, furnace temperature, stretching temperature, temperature in the stretching furnace, residual solvent amount, etc., they are omitted because they overlap with the first stretching step [S6] in the manufacturing process of the film roll by the solution casting film forming method.

[0208] (2.2.4) First cutting step [M4] In the first cutting step [M4], a cutting part (20) composed of a slitter cuts both ends in the width direction of the formed film (F). In the film (F), the portion remaining after cutting both ends constitutes the product part that becomes the 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 formation again.

[0209] (2.2.5) Second stretching step [M5] In the second stretching step [M5], the film (F) is stretched by a stretching device (21) in the same manner as in the first stretching step [M3]. As the stretching method at this time, a stretching method of providing a peripheral speed difference between rolls and stretching in the MD direction, or a tenter method of fixing both side edges of the film (F) with clips or the like and stretching in the TD direction, is preferable for improving the film's performance, productivity, flatness, and dimensional stability. In addition, in the stretching device (21), drying may be performed in addition to stretching.

[0210] (2.2.6) Second cutting step [M6] In the second cutting step [M6], a cutting part (22) composed of a slitter cuts both ends in the width direction of the formed film (F) in the same manner as in the first cutting step [M4]. In the film (F), the portion remaining after cutting both ends constitutes the product part that becomes the 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 formation again.

[0211] (2.2.7) Winding process [M7] Finally, in the winding process [M7], the film (F) is wound up by the winding device (23) to obtain a film roll. In other words, in the winding process [M7], a film roll is manufactured by winding the film (F) onto a core while it is being transported.

[0212] The winding method for the film (F) can be done using a commonly used winder, and there are various methods for controlling the tension, such as the constant torque method, constant tension method, tapered tension method, and programmed tension control method with constant internal stress, which can be used as appropriate.

[0213] 3. Resins that make up the film (3.1) Thermoplastic resin The thermoplastic resin material used in the film according to the present invention is not limited as long as it can be handled as a film roll after film formation.

[0214] Examples of thermoplastic resins used for polarizing plates include cellulose ester resins such as triacetylcellulose (TAC), cellulose acetate propionate (CAP), and diacetylcellulose (DAC), cyclic olefin resins 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 terefterate (PET).

[0215] However, it is preferable to use COP because it allows for easier control of stretchability and crystallinity, and the adhesive penetrates easily, ensuring better adhesion to the polarizer. Furthermore, the above film may be subjected to surface modification treatment after manufacturing.

[0216] Furthermore, the effects of this invention are particularly valuable in the thin-film region. The film thickness is preferably in the range of 5 to 80 μm, more preferably in the range of 10 to 65 μm, and even more preferably in the range of 10 to 45 μm.

[0217] If the film thickness is 5 μm or more, the rigidity of the film roll is high, and it becomes easy to maintain the roll shape. If the film thickness is 80 μm or less, the mass does not increase too much, and it becomes easy to produce a long film roll.

[0218] (3.1.1) Cycloolefin resin The cycloolefin resin contained in the film roll of the present invention is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and other copolymerizable monomers. <*

[0219] The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

[0220]

Chemical formula

[0221] In general formula (A-1), R 1 ~R 4 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2. However, all of R 1 ~R 4 do not simultaneously represent hydrogen atoms, R 1 and R 2 do not simultaneously represent hydrogen atoms, and R 3 and R 4 do not simultaneously represent hydrogen atoms.

[0222] In general formula (A-1), R 1 ~R 4The hydrocarbon group having 1 to 30 carbon atoms represented by is preferably a hydrocarbon group having 1 to 10 carbon atoms, and more preferably a hydrocarbon group having 1 to 5 carbon atoms.

[0223] A 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 carbonyl groups, imino groups, ether bonds, silyl ether bonds, and thio ether bonds, which are divalent polar groups. Examples of hydrocarbon groups with 1 to 30 carbon atoms include methyl, ethyl, propyl, and butyl groups.

[0224] In general formula (A-1), R 1 ~R 4 Examples of polar groups represented by include carboxyl groups, hydroxyl groups, alkoxy groups, alkoxycarbonyl groups, aryloxycarbonyl groups, amino groups, amide groups, and cyano groups.

[0225] Among these, carboxyl groups, hydroxyl groups, alkoxycarbonyl groups, and aryloxycarbonyl groups are preferred, and from the viewpoint of ensuring solubility during solution film formation, alkoxycarbonyl groups and aryloxycarbonyl groups are preferred.

[0226] 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 resulting polymer becomes bulkier, and the glass transition temperature tends to improve.

[0227] [ka]

[0228] In general formula (A-2), R 5 R represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having 1 to 5 carbon atoms. 6represents a carboxyl group, hydroxyl group, alkoxycarbonyl group, aryloxycarbonyl group, amino group, amide group, cyano group, or halogen atom (fluorine atom, chlorine atom, bromine atom, or iodine atom). p represents an integer from 0 to 2.

[0229] R in general formula (A-2) 5 It is preferable that this represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably a hydrocarbon group having 1 to 3 carbon atoms.

[0230] R in general formula (A-2) 6 The group preferably represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group, and from the viewpoint of ensuring solubility during solution film formation, the alkoxycarbonyl group and the aryloxycarbonyl group are more preferred.

[0231] In general formula (A-2), p is preferably represented as 1 or 2 from the viewpoint of improving the heat resistance of the film. When p represents 1 or 2, the resulting polymer becomes bulkier, which tends to improve the glass transition temperature.

[0232] Cycloolefin monomers having the structure represented by general formula (A-2) are preferred because they improve solubility in organic solvents.

[0233] Generally, disrupting the symmetry of organic compounds reduces their crystallinity, which in turn improves their solubility in organic solvents.

[0234] R in general formula (A-2) 5 and R 6 Because the substitution occurs only on one side of the ring-forming carbon atoms relative to the molecular axis of symmetry, the molecule has low symmetry. In other words, cycloolefin monomers having the structure represented by general formula (A-2) have high solubility and are therefore suitable for manufacturing films by solution casting.

[0235] The content of cycloolefin monomers having the structure represented by general formula (A-2) in a polymer of cycloolefin monomers can be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% of the total amount of cycloolefin monomers constituting the cycloolefin resin.

[0236] When a certain amount of cycloolefin monomers having the structure represented by general formula (A-2) is included, the orientation of the resin increases, and the phase difference (retardation) value tends to rise.

[0237] Specific examples of cycloolefin monomers having the structure represented by general formula (A-1) are shown below in example compounds 1 to 14, and specific examples of cycloolefin monomers having the structure represented by general formula (A-2) are shown in example compounds 15 to 34.

[0238] [ka]

[0239] Examples of copolymerizable monomers that can copolymerize with cycloolefin monomers include copolymerizable monomers that can copolymerize with cycloolefin monomers through ring opening, and copolymerizable monomers that can copolymerize with cycloolefin monomers through addition copolymerization.

[0240] Examples of ring-opening copolymerizable monomers include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0241] Examples of copolymerizable monomers that can be added copolymerized include unsaturated double bond-containing compounds, vinyl cyclic hydrocarbon monomers, and (meth)acrylates.

[0242] Examples of unsaturated double bond-containing compounds include olefin compounds having 2 to 12 (preferably 2 to 8) carbon atoms, such as ethylene, propylene, and butene.

[0243] Examples of vinyl cyclic hydrocarbon monomers include vinylcyclopentene monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

[0244] Examples of (meth)acrylates include alkyl (meth)acrylates with 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0245] The content of cycloolefin monomers in a copolymer of cycloolefin monomers and copolymerizable monomers can be, for example, in the range of 20 to 80 mol%, preferably in the range of 30 to 70 mol%, relative to the total amount of monomers constituting the copolymer.

[0246] As mentioned above, cycloolefin resins are polymers obtained by polymerizing or copolymerizing cycloolefin monomers having a norbornene skeleton, preferably cycloolefin monomers having a structure represented by general formula (A-1) or (A-2). Examples include the polymers (1) to (7) below.

[0247] (1) Cycloolefin monomer ring-opening polymer (2) A ring-opening copolymer of a cycloolefin monomer and a copolymerizable monomer that can be ring-opened therewith. (3) Hydrogenated ring-opening (co) polymers of the above (1) or (2) (4) A ring-opened (co)polymer of (1) or (2) above is cyclized by a Friedel-Crafts reaction, and then a (co)polymer is obtained by adding hydrogen. (5) Saturated copolymer of a cycloolefin monomer and an unsaturated double bond-containing compound (6) Addition copolymers of cycloolefin monomers with vinyl cyclic hydrocarbon monomers and hydrogenated versions thereof (7) Alternating copolymer of cycloolefin monomer and (meth)acrylate

[0248] The polymers described in (1) to (7) above can all be obtained by known methods, for example, the methods described in Japanese Patent Publication No. 2008-107534 and Japanese Patent Publication No. 2005-227606.

[0249] For example, the catalyst and solvent used in the ring-opening copolymerization described in (2) above can be those described in paragraphs 0019 to 0024 of Japanese Patent Publication No. 2008-107534.

[0250] The catalyst used in the hydrogenated materials described in (3) and (6) above can be, for example, the one described in paragraphs 0025 to 0028 of Japanese Patent Publication No. 2008-107534.

[0251] The acidic compound used in the Friedel-Crafts reaction described in (4) above can be, for example, one described in paragraph 0029 of Japanese Patent Publication No. 2008-107534.

[0252] For example, the catalyst used in the addition polymerization described in (5) to (7) above can be the one described in paragraphs 0058 to 0063 of Japanese Patent Application Publication No. 2005-227606.

[0253] The alternating copolymerization reaction described in (7) above can be carried out, for example, by the method described in paragraphs 0071 and 0072 of Japanese Patent Application Publication No. 2005-227606.

[0254] Among these, polymers (1) to (3) and (5) above are preferred, and polymers (3) and (5) above are more preferred.

[0255] In other words, the cycloolefin resin preferably contains at least one of the structural units represented by the following general formula (B-1) and the following general formula (B-2), and more preferably contains only the structural units represented by general formula (B-2), or both the structural units represented by general formula (B-1) and the structural units represented by general formula (B-2), in order to increase the glass transition temperature and light transmittance of the resulting cycloolefin resin.

[0256] The structural unit represented by general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by general formula (A-1) mentioned above, and the structural unit represented by general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by general formula (A-2) mentioned above.

[0257] [ka]

[0258] In general formula (B-1), X represents -CH=CH- or -CH2CH2-. 1 ~R 4 and p are R in general formula (A-1), respectively. 1 ~R 4 It is synonymous with p.

[0259] [ka]

[0260] In general formula (B-2), X represents -CH=CH- or -CH2CH2-. 5 ~R 6 and p are R in general formula (A-2), respectively. 5 ~R 6 It is synonymous with p.

[0261] The cycloolefin resin according to the present invention may be a commercially available product. Examples of commercially available cycloolefin resins include Arton G (e.g., G7810), Arton F, Arton R (e.g., R4500, R4900, and R5000), and Arton RX, all manufactured by JSR Corporation.

[0262] The intrinsic viscosity [η]inh of cycloolefin resins is 0.2 to 5 cm³ when measured at 30°C. 3 It is preferable that the range is within / g, and 0.3 to 3cm 3 It is more preferable that the range is within / g, and 0.4 to 1.5 cm. 3 It is even more preferable that the range is within / g.

[0263] The number-average molecular weight (Mn) of the cycloolefin resin is preferably in the range of 8,000 to 100,000, more preferably in the range of 10,000 to 80,000, and even more preferably in the range of 12,000 to 50,000.

[0264] The weight-average molecular weight (Mw) of the cycloolefin resin is preferably in the range of 20,000 to 300,000, more preferably in the range of 30,000 to 250,000, and even more preferably in the range of 40,000 to 200,000.

[0265] The number-average molecular weight and weight-average molecular weight of cycloolefin resins can be measured in polystyrene equivalents using gel permeation chromatography (GPC).

[0266] (Gel permeation chromatography) Solvent: Methylene chloride Columns: Shodex K806, K805, K803G (three columns manufactured by Showa Denko Corporation were connected together and used) Column temperature: 25℃ Sample concentration: 0.1% by mass Detector: RI Model 504 (manufactured by GL Sciences) Pump: L6000 (manufactured by Hitachi, Ltd.) Flow rate: 1.0mL / min Calibration curve: A calibration curve was used for 13 samples of standard polystyrene (STK standard polystyrene, manufactured by Tosoh Corporation) with a Mw value in the range of 500 to 2,800,000. It is preferable to use the 13 samples at approximately equal intervals.

[0267] When the intrinsic viscosity [η]inh, number-average molecular weight, and weight-average molecular weight are within the above range, the cycloolefin resin exhibits good heat resistance, water resistance, chemical resistance, mechanical properties, and moldability as a film.

[0268] The glass transition temperature Tg [°C] of cycloolefin resins is usually 110°C or higher, preferably in the range of 110 to 350°C, more preferably in the range of 120 to 250°C, and even more preferably in the range of 120 to 220°C.

[0269] A glass transition temperature (Tg) of 110°C or higher makes it easier to suppress deformation under high-temperature conditions. On the other hand, if the glass transition temperature Tg [°C] is 350°C or lower, molding becomes easier, and the degradation of the resin due to heat during molding is also easier to suppress.

[0270] The content of cycloolefin resin is preferably 70% by mass or more, and more preferably 80% by mass or more, relative to the film.

[0271] (3.1.2) Acrylic resins The acrylic resin according to the present invention is a polymer of acrylic acid ester or methacrylic acid ester, and also includes copolymers with other monomers. Therefore, the acrylic resin according to the present invention also includes methacrylic resin.

[0272] While there are no particular restrictions on the resin, it is preferable that it consists of methyl methacrylate units in the range of 50 to 99% by mass, and other monomer units copolymerizable thereto in the range of 1 to 50% by mass.

[0273] Other units that constitute acrylic resins formed by copolymerization include alkyl methacrylates with 2 to 18 C12 alkyl groups, alkyl acrylates with 1 to 18 C12 alkyl groups, hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, dicarboxylic acids containing unsaturated groups such as N-vinylpyrrolidone, maleic acid, fumaric acid, and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutarimide, and glutaric anhydride.

[0274] Examples of copolymerizable monomers that form units obtained by removing glutarimide and glutaric acid anhydride from the above units include monomers corresponding to the above units.

[0275] Specifically, examples include monomers such as alkyl methacrylates with 2 to 18 C12 alkyl groups, alkyl acrylates with 1 to 18 C12 alkyl groups, hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, dicarboxylic acids containing unsaturated groups such as N-vinylpyrrolidone, maleic acid, fumaric acid, and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, and N-substituted maleimide.

[0276] Furthermore, glutarimide units can be formed, for example, by imidizing an intermediate resin having (meth)acrylic acid ester units with a primary amine (imidizing agent) (see Japanese Patent Publication No. 2011-26563).

[0277] Glutaric anhydride units can be formed, for example, by heating an intermediate resin having (meth)acrylic acid ester units (see Japanese Patent Publication No. 4961164).

[0278] Among the structural units described above, the acrylic resin according to the present invention is particularly preferably made of isobornyl methacrylate, acryloylmorpholine, N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, styrene, hydroxyethyl methacrylate, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, or glutarimide, from the viewpoint of mechanical strength.

[0279] The acrylic resin according to the present invention preferably has a weight-average molecular weight (Mw) in the range of 50,000 to 1,000,000, more preferably in the range of 100,000 to 1,000,000, and particularly preferably in the range of 200,000 to 800,000, from the viewpoint of controlling dimensional changes in response to changes in ambient temperature and humidity, and improving peelability from metal supports during film production, drying properties of organic solvents, heat resistance, and mechanical strength.

[0280] If the value is 50,000 or higher, it exhibits excellent heat resistance and mechanical strength; if it is 1,000,000 or lower, it exhibits excellent peelability from metal supports and drying properties for organic solvents.

[0281] There are no particular limitations on the method for producing the acrylic resin according to the present invention, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used.

[0282] Here, conventional peroxide-based and azo-based polymerization initiators can be used, and redox-based initiators can also be used.

[0283] Polymerization can be carried out at temperatures ranging from 30 to 100°C for suspension or emulsion polymerization, and from 80 to 160°C for bulk or solution polymerization.

[0284] To control the reduced viscosity of the resulting copolymer, polymerization can also be carried out using alkyl mercaptans or the like as chain transfer agents.

[0285] From the viewpoint of maintaining the mechanical strength of the film, it is preferable that the glass transition temperature Tg [°C] of the acrylic resin be in the range of 80 to 120°C.

[0286] Commercially available acrylic resins can also be used as the acrylic resin according to the present invention. Examples include Delpet 60N, 80N, 980N, SR8200 (all manufactured by Asahi Kasei Chemicals Corporation), Dianaal 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.). Acrylic resins can be used in combination of two or more types.

[0287] The acrylic resin according to the present invention preferably contains additives, and as an example of additives, it is preferable to include acrylic particles (rubber elastic particles) described in International Publication No. 2010 / 001668 in order to improve the mechanical strength of the film and adjust the rate of dimensional change.

[0288] Examples of commercially available multilayer acrylic granular composites include "Metablen W-341" from Mitsubishi Rayon, "Kaneace" from Kaneka Corporation, "Paraloid" from Kureha Corporation, "Acryloid" from Rohm & Haas Corporation, "Stafloid" from Aica Corporation, Chemisnow MR-2G, MS-300X (all manufactured by Soken Chemical Co., Ltd.), and "Parapet SA" from Kuraray Corporation. These can be used individually or in combination of two or more types.

[0289] The volume-average particle diameter of the acrylic particles is 0.35 μm or less, preferably in the range of 0.01 to 0.35 μm, and more preferably in the range of 0.05 to 0.30 μm. If the particle size is above a certain level, the film can be made more stretchable under heat, and if the particle size is below a certain level, the transparency of the resulting film is less likely to be compromised.

[0290] 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 even more preferably 1.2 GPa or less.

[0291] The flexural modulus mentioned above varies depending on the type and amount of acrylic resin and rubber elastic particles in the film. For example, the higher the content of rubber elastic particles, the lower the flexural modulus generally becomes.

[0292] Furthermore, when using a copolymer of alkyl methacrylate and alkyl acrylate, etc., as an acrylic resin, the flexural modulus is generally lower than when using a homopolymer of alkyl methacrylate.

[0293] (3.1.3) Cellulose ester resins In the film roll of the present invention, it is also preferable to use a cellulose ester resin.

[0294] The cellulose ester used in this invention refers to a cellulose acylate resin in which some or all of the hydrogen atoms of the hydroxyl groups (-OH) at positions 2, 3, and 6 in the β-1,4-linked glucose units that constitute cellulose are replaced with acyl groups.

[0295] The cellulose esters mentioned above are not particularly limited, but are preferably esters of linear or branched carboxylic acids having approximately 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.

[0296] Examples of the above include cellulose esters in which the hydrogen atoms of the hydroxyl group portion of cellulose are replaced with acyl groups having 2 to 22 carbon atoms, such as acetyl groups, propionyl groups, butyryl groups, isobutyryl groups, valeryl groups, pivaloyl groups, hexanoyl groups, octanoyl groups, lauroyl groups, and stearoyl groups.

[0297] The carboxylic acid (acyl group) constituting the ester may have substituents. The carboxylic acid constituting the ester is preferably a lower fatty acid having 6 or fewer carbon atoms, and more preferably a lower fatty acid having 3 or fewer carbon atoms.

[0298] The acyl group in the cellulose ester may be a single type or a combination of multiple acyl groups.

[0299] Specific examples of preferred cellulose esters include cellulose acetates such as diacetylcellulose (DAC) and triacetylcellulose (TAC), as well as mixed fatty acid esters of cellulose in which propionate groups or butyrate groups are bonded in addition to acetyl groups, such as cellulose acetate propionate (CAP), cellulose acetate butyrate, and cellulose acetate propionate butyrate. These cellulose esters may be used individually or in combination of multiple species.

[0300] (Type of acyl group / degree of substitution) By adjusting the type and degree of substitution of the acyl group in the cellulose ester, the humidity fluctuations of the phase difference can be controlled within a desired range, thereby improving the uniformity of the film thickness.

[0301] The smaller the degree of substitution of the acyl group in the cellulose ester, the better the phase difference expression becomes, making it possible to create thin films. On the other hand, if the degree of substitution of the acyl group is too small, it may lead to a deterioration in durability, which is undesirable.

[0302] On the other hand, the greater the degree of substitution of the acyl group in the cellulose ester, the less phase difference is observed. Therefore, it is necessary to increase the stretching ratio during film formation. However, it is difficult to stretch uniformly at high stretching ratios, which leads to greater (worsening) variations in film thickness.

[0303] Furthermore, since the Rt humidity fluctuation, which is a retardation (phase difference) in the thickness direction, is caused by the coordination of water molecules to the carbonyl groups of cellulose, the higher the degree of substitution of acyl groups, that is, the more carbonyl groups there are in the cellulose, the worse the Rt humidity fluctuation tends to be.

[0304] The cellulose ester is preferably in the range of 2.1 to 2.5 in terms of total substitution degree. By setting the range accordingly, environmental fluctuations (especially Rt fluctuations due to humidity) can be suppressed, and the uniformity of the film thickness can be improved.

[0305] More preferably, the range is 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.

[0306] More specifically, cellulose esters satisfy both formulas (a) and (b) below. In formulas (a) and (b) below, X is the degree of substitution of an acetyl group, and Y is the degree of substitution of a propionyl group or a butyryl group, or a mixture thereof.

[0307] Formula (a): 2.1≦X+Y≦2.5 Formula (b): 0≦Y≦1.5

[0308] The cellulose ester is more preferably cellulose acetate (Y=0) and cellulose acetate propionate (CAP) (Y; propionyl group, Y>0), and even more preferably cellulose acetate with Y=0, as this reduces variations in film thickness.

[0309] A particularly preferred cellulose acetate is cellulose diacetate (DAC) with a x-value of 2.1 ≤ X ≤ 2.5 (more preferably 2.15 ≤ X ≤ 2.45), which allows for desired phase difference expression, Rt humidity fluctuations, and variations in film thickness.

[0310] Furthermore, when Y > 0, the cellulose acetate propionate (CAP) that is particularly preferred is one that satisfies the following conditions: 0.95 ≤ X ≤ 2.25, 0.1 ≤ Y ≤ 1.2, and 2.15 ≤ X + Y ≤ 2.45.

[0311] By using the aforementioned cellulose acetate or cellulose acetate propionate, a film roll with excellent retardation, mechanical strength, and resistance to environmental changes can be obtained.

[0312] The degree of substitution of acyl groups indicates the average number of acyl groups per glucose unit, and shows how many hydrogen atoms of the hydroxyl groups at positions 2, 3, and 6 of a glucose unit are substituted with acyl groups. Therefore, the maximum degree of substitution is 3.0, which means that all hydrogen atoms of the hydroxyl groups at positions 2, 3, and 6 are replaced by acyl groups.

[0313] These acyl groups may be evenly substituted at the 2nd, 3rd, and 6th positions of the glucose unit, or they may be substituted in a distributed manner. The degree of substitution is determined by the method specified in ASTM-D817-96.

[0314] To obtain the desired optical properties, cellulose acetates with different degrees of substitution may be mixed and used. In the above case, the mixing ratio of the different cellulose acetates is not particularly limited.

[0315] The number-average molecular weight (Mn) of cellulose esters is 2 × 10⁻⁶. 4 ~3×10 5 Within the range of 2 × 10 4 ~1.2 × 10 5 Within the range, and furthermore, 4 x 10 4~8×10 4 Within this range is preferable from the viewpoint of achieving high mechanical strength in the resulting film roll.

[0316] The number-average molecular weight (Mn) of cellulose esters is calculated by measurement using gel permeation chromatography (GPC) under the measurement conditions described above.

[0317] The weight-average molecular weight (Mw) of cellulose ester is 2 × 10⁻⁶ 4 ~1 × 10 6 Within the range of 2 × 10 4 ~1.2 × 10 5 Within the range, and furthermore, 4 x 10 4 ~8×10 4 Within this range is preferable from the viewpoint of achieving high mechanical strength in the resulting film roll.

[0318] The cellulose used as a raw material for cellulose esters is not particularly limited, but examples include cotton linters, wood pulp, and kenaf. Furthermore, the cellulose esters obtained from these can be mixed and used in any desired proportion.

[0319] Cellulose esters such as cellulose acetate and cellulose acetate propionate can be produced by known methods.

[0320] Generally, the cellulose raw material is mixed with a specified organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic anhydride, propionic anhydride, etc.), and a catalyst (sulfuric acid, etc.) to esterify the cellulose, and the reaction proceeds until a cellulose triester is produced.

[0321] In triesters, the three hydroxyl groups of the glucose unit are replaced by acylic acid, an organic acid.

[0322] By using two types of organic acids simultaneously, it is possible to produce mixed ester-type cellulose esters, such as cellulose acetate propionate or cellulose acetate butyrate.

[0323] Next, a cellulose ester resin having a desired degree of acyl substitution is synthesized by hydrolyzing the cellulose triester. Subsequently, cellulose ester resin is produced through processes such as filtration, sedimentation, washing, dehydration, and drying. Specifically, it can be synthesized by referring to the method described in Japanese Patent Publication No. 10-45804.

[0324] (3.2) Other additives The film roll of the present invention may also contain the following as other additives in addition to the thermoplastic resin described above.

[0325] (3.2.1) Plasticizers The film roll of the present invention preferably contains at least one plasticizer for the purpose of imparting processability to, for example, polarizing plate protective films. Plasticizers are preferably used alone or in a mixture of two or more types.

[0326] Among plasticizers, it is preferable to include at least one plasticizer selected from the group consisting of sugar esters, polyesters, and styrene compounds, from the viewpoint of achieving both effective control of moisture permeability and high compatibility with base resins such as cellulose esters.

[0327] The plasticizer is preferably 15,000 or less in molecular weight, and more preferably 10,000 or less, from the viewpoint of achieving both improved resistance to moisture and heat and compatibility with base resins such as cellulose esters.

[0328] If the compound with a molecular weight of 10,000 or less is a polymer, it is preferable that its weight-average molecular weight (Mw) is 10,000 or less. The preferred range for weight-average molecular weight (Mw) is 100 to 10000, and more preferably 400 to 8000.

[0329] In particular, to obtain the effects of the present invention, it is preferable to include the compound with a molecular weight of 1500 or less in an amount of 6 to 40 parts by mass per 100 parts by mass of the base resin, and more preferably in an amount of 10 to 20 parts by mass. By including the above-mentioned amount within the specified range, it is possible to achieve both effective control of moisture permeability and compatibility with the base resin, which is preferable.

[0330] (Sugar esters) The film roll of the present invention may contain a sugar ester compound for the purpose of preventing hydrolysis.

[0331] Specifically, as the sugar ester compound, a sugar ester can be used that has at least one pyranose structure or furanose structure with 1 to 12 such structures, and in which all or part of the OH groups of that structure are esterified.

[0332] (polyester) The film roll of the present invention may also contain polyester.

[0333] The polyester is not particularly limited, but for example, a polymer with terminal hydroxyl groups (polyester polyol) obtained by a condensation reaction of a dicarboxylic acid or an ester-forming derivative thereof with a glycol, or a polymer in which the terminal hydroxyl groups of the polyester polyol are encapsulated with a monocarboxylic acid (end-capped polyester) can be used.

[0334] In this context, ester-forming derivatives refer to esterified dicarboxylic acids, dicarboxylic acid chlorides, and dicarboxylic acid anhydrides.

[0335] (Styrene compounds) In addition to or in lieu thereof, styrene-based compounds may also be used in the film roll of the present invention for the purpose of improving the water resistance of the film.

[0336] The styrene-based compound may be a homopolymer of styrene-based monomers, or a copolymer of a styrene-based monomer and other copolymer monomers.

[0337] In order for the molecular structure to have a certain level of bulkiness, the content of structural units derived from styrene monomers in styrene compounds is preferably in the range of 30 to 100 mol%, more preferably in the range of 50 to 100 mol%.

[0338] Examples of styrene 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; hydroxystyrenes such as p-hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, and 3,4-dihydroxystyrene; vinylbenzyl alcohols; alkoxy-substituted styrenes such as p-methoxystyrene, p-tert-butoxystyrene, and m-tert-butoxystyrene; 3-vinylbenzoic acid, 4-vinylbenzoic acid This includes vinylbenzoic acids such as benzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; amidestyrenes such as 2-butylamidostyrene, 4-methylamidostyrene, and p-sulfonamidostyrene; aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline, and vinylbenzyldimethylamine; nitrostyrenes such as 3-nitrostyrene and 4-nitrostyrene; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene, and indenes. The styrene monomer may be a single type or a combination of two or more types.

[0339] (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. These components can be added in an amount ranging from 0.01 to 20 parts by mass per 100 parts by mass of the base resin.

[0340] (Antioxidant) The film roll of the present invention can use commonly known antioxidants. In particular, lactone-based, sulfur-based, phenol-based, double-bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

[0341] These antioxidants and the like are added in an amount of 0.05 to 20% by mass, preferably 0.1 to 1% by mass, relative to the resin, which is the main raw material of the film. These antioxidants can achieve synergistic effects by using several different compounds in combination rather than using just one type. For example, the combined use of lactone-based, phosphorus-based, phenol-based, and double-bond-based compounds is preferred.

[0342] (Coloring agent) The film roll of the present invention preferably contains a coloring agent for color adjustment, to the extent that it does not impair the effects of the present invention.

[0343] In this invention, "coloring agent" refers to dyes and pigments, and in this invention, it refers to those that have the effect of making the color tone of a liquid crystal screen bluer, or adjusting the yellow index, or reducing haze.

[0344] Various dyes and pigments can be used as colorants, but anthraquinone dyes, azo dyes, and phthalocyanine pigments are particularly effective.

[0345] (UV 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 providing ultraviolet absorption functionality.

[0346] While not particularly limited, examples of UV absorbers include benzotriazole-based, 2-hydroxybenzophenone-based, or phenyl salicylate-based UV absorbers.

[0347] Examples include triazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2′-dihydroxy-4-methoxybenzophenone. The above-mentioned ultraviolet absorbers can be used individually or in combination of two or more types.

[0348] The amount of UV absorber used varies depending on the type of UV absorber, usage conditions, etc., but generally, it is added in the range of 0.05 to 10% by mass, preferably 0.1 to 5% by mass, relative to the base resin.

[0349] (fine particles) In the present invention, it is preferable to add fine particles that impart slipperiness to the film roll. In particular, adding fine particles is effective in improving the slipperiness of the film surface according to the present invention, improving slipperiness during winding, and preventing the occurrence of scratches and blocking.

[0350] The fine particles can be either inorganic or organic, as long as they do not impair the transparency of the resulting film roll and have heat resistance during melting, but inorganic fine particles are more preferred. These microparticles can be used individually or in combination of two or more types.

[0351] By using particles with different particle sizes and shapes (for example, needle-shaped and spherical), it is possible to achieve both high transparency and slipperiness.

[0352] Among the compounds constituting the above-mentioned fine particles, silicon dioxide is particularly preferred because it has a refractive index close to that of the cycloolefin resin, acrylic resin, and cellulose ester resin, and therefore exhibits excellent transparency (haze).

[0353] Specific examples of silicon dioxide include commercially available products with product names such as Aerosil® 200V, Aerosil® R972V, Aerosil® R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (all manufactured by Nippon Aerosil Co., Ltd.), Seahostar® KEP-10, Seahostar® KEP-30, Seahostar® KEP-50 (all manufactured by Nippon Shokubai Co., Ltd.), Silohobic® 100 (manufactured by Fuji Silicia Co., Ltd.), Nipseal® E220A (manufactured by Nippon Silica Industry Co., Ltd.), and Admafine® SO (manufactured by Admatex Co., Ltd.), which can be preferably used.

[0354] The particle shape can be irregular, needle-shaped, flattened, spherical, etc., and there are no particular restrictions on the shape that can be used, but spherical particles are particularly preferred because they can improve the transparency of the resulting film roll.

[0355] The particle size is preferably smaller than the wavelength of visible light, and even more preferably less than or equal to half the wavelength of visible light, because if the particle size is close to the wavelength of visible light, light will scatter and transparency will be poor.

[0356] If the particle size is too small, the slipperiness may not be improved, so it is particularly preferable that the particle size be within the range of 80 to 180 nm. Note that particle size refers to the size of the aggregate when the particle is an aggregate of primary particles. Furthermore, if the particle is not spherical, it refers to the diameter of the circle corresponding to its projected area.

[0357] The fine particles are preferably added to the base resin in an amount of 0.05 to 10% by mass, more preferably 0.1 to 5% by mass.

[0358] 4. Polarizing plate A portion of the film in the film roll of the present invention can be suitably used by being incorporated into a polarizing plate. A polarizing plate is generally composed of a polarizer film (also called a "polarizing film" or "polarizer film") and transparent resin films laminated on both sides thereof. Some of the films in the film roll of the present invention may be provided in the polarizing plate as such resin films.

[0359] Examples of polarizing plates include those having a polarizer layer made of a polarizer film, a polarizing plate protective film made of a resin film, and an adhesive layer disposed between them.

[0360] (4.1) Polarizer layer The polarizer layer described above is a layer consisting of at least a polarizer film. Here, a "polarizer" refers to an element that allows only light with a specific polarization plane to pass through.

[0361] Examples of polarizing films include polyvinyl alcohol-based polarizing films and cellulose ester-based polarizing films. However, polyvinyl alcohol-based resins are preferred over cellulose ester-based resins because they offer superior transparency, optical properties, and durability.

[0362] Polyvinyl alcohol-based polarizing films include those dyed with iodine and those dyed with dichroic dyes.

[0363] The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing it with iodine or a dichroic dye (preferably a film further treated for durability with a boron compound), or a film obtained by uniaxially stretching a polyvinyl alcohol-based film after dyeing it with iodine or a dichroic dye (preferably a film further treated for durability with a boron compound). The absorption axis of the polarizer layer is typically parallel to the direction of maximum elongation.

[0364] For example, ethylene-modified polyvinyl alcohol with an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99.0 to 99.99 mol%, as described in Japanese Patent Publication No. 2003-248123 and Japanese Patent Publication No. 2003-342322, can be used.

[0365] The thickness of the polarizer layer is preferably 5 to 30 μm, and more preferably 5 to 20 μm, for example, in order to make the polarizer thinner.

[0366] (4.2) Polarizing film protective film A portion of the film in the film roll of the present invention can be placed on at least one surface of the polarizer layer (at least the surface facing the liquid crystal cell) and can be used as a polarizer protective film or a phase difference film. The surface on which the polarizer layer of the polarizing plate protective film is laminated may be subjected to the activation treatment described later.

[0367] If a portion of the film in the film roll of the present invention is arranged on only one side of the polarizer layer as a polarizing plate protective film, another optical film, such as a phase difference film, may be arranged on the other side of the polarizer layer.

[0368] Other examples of optical films include commercially available cellulose ester films (e.g., Konica Minolta Tack KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA) This includes models such as KC6UA, KC8UA, KC2UAH, KC4UAH, and KC6UAH (all manufactured by Konica Minolta, Inc.), and Fujitac T40UZ, Fujitac T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, and Fujitac R06 (all manufactured by Fujifilm Corporation).

[0369] The thickness of the other optical films may be, for example, 5 to 100 μm, preferably 40 to 80 μm.

[0370] (4.3) Adhesive layer The adhesive layer is a water-based adhesive or an ultraviolet-curing adhesive that has been dried and placed between a portion of the film (or other optical film) of the film roll of the present invention and the polarizer layer.

[0371] The thickness of the adhesive layer can be, for example, 0.01 to 10 μm, preferably about 0.03 to 5 μm.

[0372] (Water-based adhesive) Examples of water-based adhesives include vinyl-based, gelatin-based, vinyl latex-based, polyurethane-based, isocyanate-based, polyester-based, and epoxy-based adhesives.

[0373] When a polyvinyl alcohol-based polarizing film is used for the polarizer layer, a water-based adhesive containing a vinyl resin is preferred from the viewpoint of easily obtaining adhesion, and a water-based adhesive containing a polyvinyl alcohol resin (such as a fully saponified polyvinyl alcohol aqueous solution) is more preferred.

[0374] Water-based adhesives containing polyvinyl alcohol resins may further contain water-soluble crosslinking agents such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid.

[0375] (UV-curing adhesive) The UV-curable adhesive may be a photo-radical polymerizable composition or a photo-cationic polymerizable composition. Among these, photocationically polymerizable compositions are preferred.

[0376] The photocationic polymerizable composition comprises an epoxy compound and a photocationic polymerization initiator.

[0377] An epoxy compound is a compound having one or more, preferably two or more, epoxy groups in its molecule.

[0378] Examples of epoxy compounds include hydrogenated epoxy compounds obtained by reacting an alicyclic polyol with epichlorohydrin (glycidyl ethers of polyols having an alicyclic ring); aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts; and alicyclic epoxy compounds having one or more epoxy groups bonded to an alicyclic ring within the molecule. One type of epoxy compound may be used, or two or more types may be used in combination.

[0379] Photocationic polymerization initiators can be, for example, aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; or iron-arene complexes.

[0380] The photocationic polymerization initiator may further contain additives such as oxetanes, polyols, photosensitizers, and solvents, as needed.

[0381] (4.4) Method for manufacturing polarizing plates The method for manufacturing a polarizing plate according to the present invention comprises: 1) a step of applying an activation treatment to the surface of a polarizing plate protective film; 2) a step of laminating a polarizer layer (polarizing film) onto the activated surface of the polarizing plate protective film via a water-based adhesive or an ultraviolet-curing adhesive; and 3) a step of drying the resulting laminate.

[0382] Regarding step 1) The surface of the polarizing plate protective film (the surface that adheres to the polarizer layer) is subjected to an activation treatment. This makes it easier to achieve adhesion with the polarizer layer.

[0383] Specifically, the activation treatment makes the siloxane bonds, ether bonds, and tertiary carbon atoms in the side chains of certain graft polymers contained in the polarizer protective film hydrophilic, thereby increasing their affinity for water-based adhesives and facilitating their interaction, thus facilitating adhesion between the polarizer protective film and the polarizer layer.

[0384] Examples of activation treatments include corona treatment, plasma treatment, and saponification treatment, preferably corona treatment and plasma treatment, and more preferably corona treatment.

[0385] The activation treatment conditions should be sufficient to adequately activate the siloxane bonds, ether bonds, and tertiary carbon atoms contained in the side chains of the specific graft polymer. If the activation treatment is corona treatment, the irradiation dose is 100-1000 [W·min / m²]. 2 It is preferable that the range be 150-900 [W·min / m]. 2 It is more preferable that it be within the range of ].

[0386] Regarding step 2) Next, a polarizer layer is laminated onto the activated surface of the polarizing plate protective film via a water-based adhesive or an ultraviolet-curing adhesive.

[0387] Regarding step 3) Next, the resulting laminate is dried to obtain a polarizing plate.

[0388] Drying can be carried out by heat drying. The drying temperature should be any temperature at which the water-based adhesive or UV-curing adhesive dries sufficiently, for example, it may be in the range of 60 to 100°C.

[0389] 5.Display device A portion of the film in the film roll of the present invention can be suitably used by being incorporated into a display device. Examples of the aforementioned display devices include various image display devices such as liquid crystal display devices and organic EL display devices. The following describes an example of the use of some of the films in the film roll of the present invention, specifically when they are provided as polarizing plate protective films in polarizers and liquid crystal display devices.

[0390] (5.1) Liquid crystal display device Specifically, the present invention includes, for example, a liquid crystal display device comprising a liquid crystal cell and a pair of polarizing plates that sandwich it.

[0391] Figure 16 is a schematic diagram showing an example of the configuration of the liquid crystal display device of the present invention. As shown in Figure 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).

[0392] 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, and the VA (MVA, PVA) mode is preferable in order to obtain high contrast.

[0393] The first polarizing plate (210) includes a first polarizer (212), a polarizing plate protective film (211) positioned on the side of the first polarizer (212) opposite to the liquid crystal cell, and a polarizing plate protective film (213) positioned on the side of the first polarizer (212) facing the liquid crystal cell.

[0394] The second polarizer (230) includes a second polarizer (232), a polarizer protective film (231) positioned on the liquid crystal cell side of the second polarizer (232), and a polarizer protective film (233) positioned on the side of the second polarizer (232) opposite to the liquid crystal cell. One of the polarizer protective films (213) and (231) may be omitted if necessary.

[0395] Furthermore, at least one of the polarizing plate protective films (211) and (233) may be the resin film according to the present invention.

[0396] (5.2) Other uses A portion of the film in the film roll of the present invention can be preferably used not only as a protective film for polarizing plates of liquid crystal display devices, but also as a protective film for image display devices equipped with touch panels, organic EL displays, plasma displays, and other image display devices.

[0397] The embodiments to which the present invention can be applied are not limited to those described above, and can be modified as appropriate without departing from the spirit of the invention. [Examples]

[0398] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "mass%".

[0399] [A. Film Roll Production] [A.1 Preparation of Film Roll No. 1] Solution casting was used to produce the film.

[0400] (Doping process [S1]) <Synthesis of cyclic polyolefin polymer [P-1]> 100 parts by mass of purified toluene and 100 parts by mass of norbornene carboxylate methyl ester were added to a stirring device.

[0401] Next, 25 mM (relative to monomer mass) of ethylhexanoate-Ni dissolved in toluene, 0.225 mol (relative to monomer mass) of tri(pentafluorophenyl)boron, and 0.25 mol (relative to monomer mass) of triethylaluminum dissolved in toluene were added to a stirring device. The reaction was carried out at room temperature for 18 hours with stirring.

[0402] After the reaction was complete, the reaction mixture was added to excess ethanol to generate a polymer precipitate. The precipitate was purified, and the resulting polymer was dried under vacuum at 65°C for 24 hours to synthesize a cyclic polyolefin polymer [P-1].

[0403] <Preparation of cyclic polyolefin solution (dope [D-1])> The following composition [1] was placed in a mixing tank and stirred to dissolve each component. The mixture was then filtered through filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to prepare a cyclic polyolefin solution (dope [D-1]).

[0404] 《Composition [1]》 • Cyclic polyolefin polymer [P-1] 25 parts by mass • Dichloromethane 65 parts by mass • 10 parts by mass of ethanol

[0405] <Preparation of the fine particle dispersion [1]> Next, the following composition [2] was put into a disperser to prepare a fine particle dispersion [1] as an additive.

[0406] 《Composition [2]》 • Microparticles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary mean particle size: 7 nm, apparent specific gravity 50 g / L) 4 parts by mass • Dichloromethane 76 parts by mass • Ethanol 20 parts by mass

[0407] <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 the fine particle dispersion [1] were mixed to prepare film-forming dope [1] (resin composition: cycloolefin resin: COP).

[0408] (Casting process [S2]) In the dope preparation step [S1], the film-forming dope [1] (resin composition: cycloolefin resin: COP) prepared was delivered to the casting die via a conduit through a pressurized metering gear pump. The dope was then cast from the casting die in a width of 1800 mm on a support made of an endlessly rotating stainless steel belt that continuously transported the dope. The dope was heated on the support until it became self-supporting, and the solvent was evaporated to dry it until the cast film could be peeled off the support by a peeling roller, thereby forming a cast film.

[0409] (Peeling process [S3]) In the casting process [S2], after forming the cast film, the cast film was peeled off the support using a peeling roller while maintaining its self-supporting properties.

[0410] (Shrinkage process [S4]) The film was subjected to high-temperature treatment without being held in place by its width, thereby increasing its density and causing it to shrink in the width direction with a shrinkage rate of 7%.

[0411] (1st drying process [S5]) Subsequently, the film was heated on the support to evaporate the solvent. The amount of residual solvent in the film was measured by the following method and found to be 5% by mass or less.

[0412] <Measurement of residual solvent amount> The amount of residual solvent was determined by mass spectrometry using gas chromatography as follows. In other words, a film sample was taken from any desired location, and to prevent the evaporation of any solvent remaining in the film, it was quickly placed in a vial and sealed. Next, a needle was inserted into the vial, and mass spectrometry was performed using a gas chromatograph (manufactured by Agilent Technologies, Inc.).

[0413] The amount of residual solvent is defined by the following formula. Residual solvent amount [mass%] = {(MN) / N} × 100 In the above formula, M is the mass [g] of a sample taken at any point during or after the production of the cast film or film, and N is the mass [g] of the sample after heating at 115°C for 1 hour.

[0414] (1st stretching process [S6]) The film was then transported in a tenter stretching machine and stretched horizontally.

[0415] (1st cutting process [S7]) The ends of the stretched film in the width direction were cut.

[0416] (Second stretching process [S8]) Similar to the first stretching process, the film was stretched using a tenter stretching device. The amount of residual solvent in the film was measured using the method described above and was found to be 1-5% by mass.

[0417] (Second cutting process [S9]) Similar to the first cutting step, both ends of the stretched film in the width direction were cut.

[0418] (Second drying process [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 using the method described above and was found to be 0.1 to 2% by mass.

[0419] (Third cutting process [S11]) Similar to the first and second cutting steps, both ends of the stretched film in the width direction were cut.

[0420] (Winding process [S12]) The above film was wound at a winding speed (line speed for transporting the film) of 60 m / min, with a film roll width of 2000 mm and a winding length of 10000 m. The thickness of the film during winding was measured to be 40 μm.

[0421] Furthermore, using a winding device and TR (touch roller), the touch pressure around the winding core was adjusted to 15.2 N / m and the tension to 40 N / m, the touch pressure in the center of the winding was adjusted to 16.0 N / m and the tension to 40 N / m, and the touch pressure around the outer edge of the winding was adjusted to 16.0 N / m and the tension to 40 N / m, with a 70% taper and a 25% corner.

[0422] The film thickness was measured at 1612 points using an inline retardation film thickness measuring device RE-200L2T-Rth + film thickness (manufactured by Otsuka Electronics Co., Ltd.). The difference in height between the highest and lowest points of the uneven structure formed on the film surface was calculated, and the average value was used. During this time, the traverse speed was 100 mm / sec.

[0423] Through the above process, film roll No. 1 was produced.

[0424] [A.2 Preparation of film rolls No. 2-13] Film rolls No. 2 to 13 were manufactured in the same manner as film roll No. 1, except that the type of dope (resin composition) for film formation in the dope preparation step [S1], the winding length [m], winding speed [m / min] in the winding step [S12], the film thickness [μm], the touch pressure [N / m] and tension [N / m] around the winding core, the touch pressure [N / m] and tension [N / m] in the center of the winding, and the touch pressure [N / m] and tension [N / m] around the outer edge of the winding were changed as shown in Table I.

[0425] [Table 1]

[0426] [B. Calculation of the thickness of the void layer around the core, in the center of the winding, and around the outer edge of the winding] After storing each prepared film roll at 40°C and 80% RH for one week, the thickness of the void layer around the core, in the center of the roll, and around the outer edge of the roll was calculated using the method described above (an example of a method for calculating the thickness of the void layer).

[0427] The following describes a specific method for calculating the thickness of the void layer around the core using film roll No. 1.

[0428] The position where the winding diameter is 20% on the side of film roll No. 1 after one week of storage (P 20 The side portion was photographed, centering on the ), and image data was acquired. Edge enhancement processing was performed on the acquired image data to obtain a processed image for calculating the thickness of the void layer, as shown in Figure 3.

[0429] Then, the center of the processed image (P 20Starting from point ), the radial length was measured with the winding perpendicular to the film surface and ending at the point at the 100th layer outward. The thickness X [μm] of the void layer around the winding core was calculated using the following formula (A).

[0430] Equation (A) Thickness of the void layer X [μm] = [Radial length [μm] - (Average thickness per film layer measured by a film thickness gauge [μm]) × (Number of layers)] ÷ (Number of layers)

[0431] Substituting the measured values, the thickness of the void layer of film roll No. 1, X [μm] = [4021 μm - 40.00 μm × 100] ÷ 100 = 0.21 μm.

[0432] The thickness of the void layer in the center of the winding is determined by the position (P) where the winding diameter is 50% on the side surface in the width direction. 50 The side portion is photographed with the ) as the center, and the center of the processed image (P 50 The calculation was performed in the same manner as the thickness of the void layer around the core, except that the starting point was ).

[0433] Regarding the thickness of the void layer in the outer peripheral part of the winding, at the position where the winding diameter is 80% in the width direction of the side surface (P 80 The side portion is photographed with the ) as the center, and the center of the processed image (P 80 The calculation was performed in the same manner as the thickness of the void layer around the core, except that the starting point was ).

[0434] [C rating] [C.1 Evaluation based on the degree of tape transfer] (Evaluation method) After storing each film roll for one week as described above, the film was unwound, and the length of the tape transfer, where a clearly visible strip-like deformation in the width direction was observed, was measured using a tachometer to determine how many meters from the core the film length was displayed on the winding device. The results were then evaluated based on the following evaluation criteria. The results are shown in Table I.

[0435] (Evaluation Criteria) ○: Tape transfer only occurs up to less than 20m from the core. △: Tape transfer has occurred from the core portion of the tape up to less than 50m. ×: Tape transfer has occurred for more than 50m from the core of the tape.

[0436] [C.2 Evaluation based on the degree of chain-like deformation] (Evaluation method) After storing each film roll for one week as described above, the film was unwound, and the length [m] of the film that had undergone chain-like deformation was measured using a tachometer at the longitudinal position of the film displayed on the winding device. The film was then evaluated based on the following evaluation criteria. Furthermore, a score of △ or higher in the evaluation criteria below was considered to indicate no practical problems. The results are shown in Table I.

[0437] (Evaluation Criteria) ◎: The length of the film where chain-like deformation occurred is less than 10m. ○: The length of the film where chain-like deformation occurred is 10m or more but less than 50m. △: The length of the film where chain-like deformation occurred is 50m or more but less than 200m. ×: The length of the film where chain-like deformation occurred is 200m or more.

[0438] [D Summary] As is clear from the conditions and evaluation results shown in Table I, the embodiments of the present invention are superior to the comparative examples in terms of the degree of tape transfer and the degree of chain-like deformation, demonstrating overall superiority. [Explanation of Symbols]

[0439] 1. 1a. Agitation device (agitation tank) 2 Flow Die 3. Support structure (endless belt, drum) 3a, 3b rollers 4. Peeling roller 5 Casting membrane 6 Drying equipment 7. Stretching equipment (tenter stretching equipment, oblique stretching equipment) 8 Cut section 9 Stretching device (tenter stretching device) 10 Cut section 11 Drying equipment 12 Cut section 13 Winding device 14. Extruder 15 Flowing Die 16 cast drums, small size 16a Touch Roller 17 Cooling Drum 19 Stretching device (tenter stretching device) 20 Cut section 21 Stretching device (tenter stretching device) 22 Cut section 23 Winding device 30 film rolls 31 film 32 rollers 33 Touch Roller 40 Stretching device (tenter stretching device) 42 clips 46 Cover 48 Endless Chain 50 Drive sprocket 52 Driven sprocket 54 rails 56 Open member 60 Total Reflection Mirrors 61 Half Mirror 62 Telecentric Lens 63 High-brightness line lighting 64 Monochrome Line Sensor Camera 80 Temperature distribution sensor 101 Nozzle fixing part 102 Nozzles 103 Casting membrane 104 End Nozzle 105 Central Nozzle 106 Clip Cover 200 LCD display device 210 First polarizing plate 211 Polarizing plate protective film located on the side of the first polarizer opposite to the liquid crystal cell side. 212 First polarizer 213 Polarizing plate protective film placed on the liquid crystal cell side of the first polarizer 220 LCD cells 230 Second polarizing plate 231 Polarizing plate protective film placed on the liquid crystal cell side of the second polarizer 232 Second polarizer 233 Polarizing plate protective film located on the side of the second polarizer opposite to the liquid crystal cell side. 240 Backlight A. Periphery of the winding core B. Center of the winding C Outer peripheral area F Film H A H B width Q: Thermocouples, infrared (IR) heaters E Imaging device R winding core TD film roll width direction U Imaging Unit P Any point on the side surface of the film roll in the width direction S: The surface of the film roll to be measured (side portion in the width direction) S0 core surface The film layer attached to the surface of the S1 core The film layer that forms the boundary between the periphery of the S2 core and the center of the winding. The film layer that forms the boundary between the center and outer periphery of the S3 winding. The outermost film layer of the S4 film roll. P 20 Position where the winding diameter is 20% P 50 Position where the winding diameter is 50% P 80 Position where the winding diameter is 80%

Claims

1. A film roll without a knurled section, When the thickness of the void layer between adjacent films in the peripheral area of ​​the film roll is measured on the side surface in the width direction, and X [μm] is the thickness of the void layer between adjacent films in the peripheral area outside the roll, and Y [μm] is the thickness of the void layer between adjacent films in the peripheral area outside the roll, then X and Y satisfy the relationship given by equation (1) below. A film roll characterized by the following features. Equation (1): Y < X

2. The above X [μm] and Y [μm] satisfy the following equations (2) and (3). The film roll according to feature 1. Equation (2): 0.05 < Y < 0.50 Equation (3): 1 < (X / Y) < 3

3. A method for manufacturing a film roll that does not have a knurled section, When the thickness of the void layer between adjacent films in the peripheral area of ​​the winding core, measured on the side surface in the width direction of the film roll, is X [μm], and the thickness of the void layer between adjacent films in the peripheral area outside the winding is Y [μm], the values ​​of X and Y are adjusted to satisfy the relationship shown in the following equation (1). A method for manufacturing a film roll, characterized by the following features. Equation (1): Y < X

4. The X [μm] and Y [μm] are adjusted to satisfy the following equations (2) and (3). The method for manufacturing a film roll according to feature 3. Equation (2): 0.05 < Y < 0.50 Equation (3): 1 < (X / Y) < 3

5. The film touch pressure at the periphery of the winding core is adjusted to a range of 2 to 30 [N / m], the film touch pressure at the center of the winding is adjusted to a range of 3 to 40 [N / m], and the film touch pressure at the outer periphery of the winding is adjusted to a range of 5 to 55 [N / m]. A method for manufacturing a film roll according to claim 3 or 4.

6. A portion of the film of the film roll described in claim 1 or claim 2 is provided. A polarizing plate characterized by the following features.

7. A portion of the film of the film roll described in claim 1 or claim 2 is provided. A display device characterized by the following features.

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