KR20230167314A - Film roll and method for manufacturing the same - Google Patents

Abstract

The object of the present invention is to provide a means to further reduce the misalignment of the attachment and winding of the film roll.
If it is a film roll without a knurling portion, and the gap between the film layers in the roll measured from the side of the film roll is X (unit: ㎛), and the film thickness deviation including the film end is Y (unit: ㎛), A film roll that satisfies the following equations (1) and (2).

Description

FILM ROLL AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a film roll and a method of manufacturing the same.

In recent years, with the fierce price competition of liquid crystal TVs, cost reduction measures such as reduction of conversion losses have been considered by polarizer manufacturers. More specifically, a polarizing plate is produced by bonding a polarizer and an optical film, but for the purpose of shortening the production time due to the conversion loss, etc., manufacturers of optical films are examining the provision of long optical film rolls. is in progress.

However, as the film roll becomes longer, the weight of the winding increases, making it more difficult to maintain a uniform stress balance from the winding core to the outside of the winding, so the film roll maintains a high-quality winding state without deformation over time. The challenge is to provide .

Conventionally, film rolls wound with an optical film that has been knurled at the film end have been industrially adopted from the viewpoints of productivity, cost, etc. The main functions of the knurling processing section are:

1) Suppression of adhesion by introducing voids (also known as air layers) between films

2) Suppression of winding misalignment due to physical irregularities

It is thought that there are two. In addition, immediately after completion of winding of the film roll (immediately after manufacturing), the above-mentioned voids (air layer) between the films inhibit adhesion of product surfaces to each other.

However, during transportation (transportation by ship, truck, etc.) or when stored in a warehouse, a phenomenon occurs in which the voids (air layer) between the films escape with time. There are few cases where film rolls stored in a warehouse are used immediately to start production, and in some cases, they are stored in the warehouse for a long period of time. Therefore, there has been a demand for improvement in the storage properties regarding the attachment.

In addition, the winding of the film roll tends to be misaligned due to vibration or shock that occurs during transportation by trucks, etc., and it is also affected by seasonal fluctuations, making control very difficult. This can be solved by winding an optical film with knurled ends. Because it was not enough, improvement was required.

Here, Patent Document 1 discloses an optical film in which both ends are knurled and a roll body in which an air layer is mixed. In addition, Patent Document 2 discloses a method for manufacturing an optical film in which an optical film is wound around a winding shaft while knurling is provided at both ends, and the gap between the film layers of the roll after winding is created by varying the emboss height with respect to the winding diameter. A manufacturing method for maintaining constant is disclosed.

Patent Document 3 discloses a technique for setting film thickness unevenness (deviation) in a specific range as a way to improve the quality of retardation films.

Japanese Patent Publication No. 2009-208358 Japanese Patent Publication No. 2013-46966 Japanese Patent Publication No. 2007-254699

However, in the technology described in the above-mentioned patent document, the reduction of the sticking and winding misalignment of the film roll was insufficient, and further improvement was required.

Therefore, the purpose of the present invention is to provide a means to further reduce the misalignment of the attachment and winding of the film roll.

The present inventors conducted extensive research. As a result, it was found that the above-mentioned problem was solved by the following film roll, and the present invention was completed.

That is, the present invention is a film roll without a knurling portion, and the gap between film layers in a roll measured from the side of the film roll is X (unit: ㎛), and the film thickness deviation including the film end is Assuming Y (unit: ㎛), it is a film roll that satisfies the following equations (1) and (2).

According to the present invention, a means for further reducing the sticking and winding misalignment of the film roll can be provided.

1 is a schematic diagram showing an example of an imaging unit included in an imaging device used when measuring the gap between film layers.
Figure 2 is a schematic diagram showing an example of an imaging device used when measuring voids between film layers.
FIG. 3 is a diagram showing an example of a system configuration included in an imaging device used when measuring voids between film layers.
Figure 4 is a schematic diagram showing an example of the measurement method and measurement results of the gap between film layers.
Figure 5 is a schematic diagram showing an example of the measurement method and measurement results of the gap between film layers.
6 is a schematic diagram showing an example of the arrangement of an infrared (IR) heater.

The present invention is a film roll without a knurling portion, where the gap between film layers in a roll measured from the side of the film roll is X (unit: ㎛), and the film thickness deviation including the film end is Y (unit: ㎛) This is a film roll that satisfies the following equations (1) and (2).

The film roll of the present invention having such a structure has further reduced sticking and winding misalignment.

In order to solve the problem of further reducing the sticking and winding misalignment of the film roll, the present inventors first analyzed the steps in which sticking occurs in the film roll subjected to the knurling process.

During storage of a film roll, the voids (air layer) between the films gradually disappear with time, and buckling begins to occur near the center of the film roll due to its own weight. Subsequently, several points of the pasted parts overlap, and in order to let the force escape, in addition to the fine wrinkles in the width direction, a long period of cross-wise sticking occurs. It was found that as the film roll becomes longer, the self-wound weight increases, so this sticking becomes more noticeable.

Based on this phenomenon, the present inventors attempted to eliminate knurled portions and reduce the gap between film layers in order to suppress winding misalignment due to transport vibration and buckling deformation over time. By reducing the gap between film layers, the problem of buckling deformation mentioned above was solved, but instead, it was found that new defects (also called black band defects and gauge band defects) caused by films being stuck in contact with each other occurred.

Therefore, the present inventors conducted further studies and found that there was a correlation between the gap between the film layers and the film thickness deviation and the winding defect, and thought of supplementing the function of knurling by controlling the film thickness deviation.

If the film thickness deviation is too small than the gap between film layers, the area of the contact area (resistance area) between the films becomes small, making it easy to slip and cause winding misalignment. Conversely, if the film thickness deviation is too large than the gap between film layers, the film thickness deviation is easy to occur. It was found that sticking defects (black band defects) were likely to occur starting from the peak. In this regard, when the gap between the layers of the film in the roll (unit: ㎛) is The present inventors found that rolls can solve the above problems.

Conventional film rolls with knurled portions were supported by lines, so to speak, with irregularities (embosses) of several micrometers existing at both ends of the film, which attempted to reduce sticking and winding misalignment. In contrast, the present invention does not have knurling portions at both ends of the film, but controls sticking and winding misalignment over the entire surface by unevenness (irregularities smaller than embossing) accompanying the film thickness variation of the film, a new, unprecedented method. It is achieved through approach.

Additionally, the above mechanism is based on speculation, and its error does not affect the technical scope of the present invention.

Hereinafter, the present invention, its components, and forms and aspects for carrying out the present invention will be described in detail. Additionally, the present invention is not limited to the following embodiments.

In this specification, “X to Y” is used to include the numerical values (X and Y) described before and after them as the lower limit and the upper limit, and means “X to Y or less.” In addition, in this specification, unless otherwise specified, operations and measurements of physical properties are performed under the conditions of room temperature (20 to 25°C)/relative humidity 40 to 50% RH/normal pressure (1 atm).

[Overview of the film roll of the present invention]

The film roll of the present invention does not have a knurling portion, and the gap between the film layers in the roll measured from the side of the film roll is X (unit: ㎛), and the film thickness deviation including the film end is Y (unit: ㎛). This satisfies the following equations (1) and (2).

(Definition of Terms)

First, below, the meaning of main terms related to the present invention will be explained.

“The gap between the layers of the film in a roll,

<Measurement method>

The imaging device of FIG. 2, which includes the imaging unit shown in FIG. 1 and has the system configuration shown in FIG. 3, is installed on the side of the film roll as shown in FIG. 5, and the side of the film roll is photographed. The measurement was performed centering on a point located outside 50% of the roll side surface from the winding core (a point at 50% of the film roll diameter, point B in Figs. 4 and 5) to calculate the gap between layers of the film in the roll. Measure the burn. Similarly, 20% of the winding outside from the winding core on the end face of the roll body (point at 20% of the film roll diameter, point A in Fig. 5) inside the film interlayer void and 80% winding outside from the winding core on the end face of the roll body. Each image for calculating the gap between film layers outside the roll (point at 80% of the film roll diameter, point C in FIG. 5) is measured. Measured image data is acquired, edge emphasis processing is performed on the acquired image data, and a processed image (for example, an image within the thick frame of FIGS. 4 and 5) is obtained. Additionally, the radial length is measured using the center position of the processed image as the starting point and the position in the 100th layer toward the outside of the winding as the end point, and the gap between each film layer is calculated using the following equation:

In addition, when the total length of the film roll is short and there are no 100 layers required for calculating the outer film interlayer void, the outer film interlayer void is the number of layers from the 80% winding outer side to the outermost layer from the winding core on the end surface of the roll body. You can calculate it using .

<Film thickness>

In this specification, the film thickness of the film is obtained as follows. In the width direction, the film thickness at 100 points including the film edge is measured online. In the conveyance direction, the entire length is measured online every 1 m. For example, in the case of a film roll with a total length of 3,000 m, 100 points in the width direction x 3,000 points in the conveyance direction = 300,000 points in total are measured.

The film thickness used in calculating the space between film layers within the roll is the average value of the film thickness at 100 points in the width direction measured at the point when the film roll reaches 20% of the diameter. The film thickness used in calculating the gap between film layers in a roll is the average value of the film thickness at 100 points in the width direction measured when the film roll reaches 50% of the diameter. The film thickness used in calculating the gap between the outer film layers is the average value of the film thicknesses of 100 points in the width direction measured at the point when the film roll reaches 80% of the diameter.

The film thickness deviation Y including the film edge in the above equation (2) is the film thickness deviation (maximum film thickness - minimum film thickness) of 100 points measured for calculation of the interlayer void of the rolled film.

The film thickness is measured using SI-T10 (spectral interference displacement type, multilayer film thickness meter) manufactured by Keyence Corporation. In addition, the film thickness is not limited to the above-described measuring device, and may be measured using a film thickness measuring device RE-200L2T manufactured by Otsuka Electronics Co., Ltd.

“Film edge” refers to a region within 10 cm from the end of the film in the width direction.

“Central portion” refers to the area excluding both ends in the width direction of the film roll. “Outer diameter” refers to the diameter of a circle formed at the outermost periphery of a roll when the cross-section perpendicular to the central axis (core) of the film roll is taken as a circle. Therefore, “outer diameter of the end” refers to the diameter (average value) of the circular cross-section observed at the end region. Additionally, the “outer diameter of the central portion” refers to the diameter of the circular cross-section observed from the central point of the central portion.

(Shape of the film roll of the present invention, etc.)

The film roll of the present invention is not subjected to knurling at both ends (does not have knurling portions), the space between the film layers in the roll measured from the side of the film roll is X (unit: ㎛), and the film including the film end When the film thickness deviation is Y (unit: ㎛), the above equations (1) and (2) are satisfied.

When X in the above formula (1) is 0.05 μm or less, defective sticking becomes more likely to occur. Additionally, when the X is 0.50 μm or more, winding misalignment becomes more likely to occur. The X is preferably 0.08 to 0.48 μm, and more preferably 0.10 to 0.30 μm.

When X/Y in the above formula (2) is 0.7 or less, sticking defects become more likely to occur. Moreover, when Y is 2.0 or more, winding misalignment becomes more likely to occur. The X/Y is preferably 0.75 to 1.80, more preferably 0.80 to 1.50, and still more preferably 0.80 to 1.40.

From the viewpoint of further improving the effect of the present invention, the standard deviation σ of the inner film interlayer void, the inner film interlayer void, and the outer film interlayer void of the film roll according to the present invention is preferably 0.18 or less, and more preferably 0.15 or less. , it is more preferable that it is less than 0.08, and it is most preferable that it is 0.

In the present invention, the gap between film layers is appropriately adjusted by 1) the amount of pressure on the film by the touch roll (hereinafter simply referred to as touch pressure), 2) winding tension, 3) winding speed, 4) roller winding angle, etc. You can control it by doing this. Additionally, the film thickness deviation Y can be controlled by appropriately selecting the heating method (heating means, heater spacing, etc.) when stretching the film. Among these, the control methods 1) and 2) in particular will be explained in detail later.

In addition, the film roll according to the present invention preferably has a ratio of the outer diameter of the central portion to the outer diameter of the end portions (outer diameter of the central portion/outer diameter of the ends) of 0.98 to 1.02. Within this range, the effect of the present invention can be further improved.

(Resin used in film rolls)

<Thermoplastic resin>

As a material used for the film obtained from the film roll according to the present invention (hereinafter also simply referred to as “film according to the present invention”), a thermoplastic resin is preferable. The thermoplastic resin material is not particularly limited as long as it can be handled as a film roll after film formation. The thermoplastic resin may be used individually or in combination of two or more types. In addition, the film according to the present invention may have a single-layer structure or may have a multi-layer structure of two or more layers.

Examples of thermoplastic resins include, for example, cyclic polyolefin resins such as cycloolefin polymers used as polarizing plates (hereinafter also referred to as cycloolefin resins (COP)), chain polyolefin resins such as polypropylene (PP), and polymethyl methacrylate. Acrylic resins such as (PMMA), cellulose ester resins such as triacetylcellulose (TAC), cellulose acetate propionate (CAP), and diacetylcellulose (DAC), and polyester resins such as polyethylene terephthalate (PET). You can. Among them, cycloolefin resin, acrylic resin, or cellulose ester resin is preferable.

However, it is more preferable to use cycloolefin resin (COP) because it is easy to control stretchability and crystallinity, the adhesive is easy to penetrate, and better adhesion to the polarizer can be secured. That is, it is more preferable that the film roll concerning this invention contains cycloolefin resin. In addition, the film according to the present invention may be subjected to surface modification treatment after production.

Additionally, the effect of the present invention becomes more valuable in the thin film area. The film thickness of the film according to the present invention 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. When 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, making it easy to produce long film rolls.

Hereinafter, preferred thermoplastic resins, such as cycloolefin resin, acrylic resin, and cellulose ester resin, will be described in detail.

≪Cycloolefin resin (COP)≫

The cycloolefin resin (COP) used in the present invention is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and another copolymerizable monomer. In addition, cycloolefin resin can also be used individually or in combination of two or more types.

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).

In the general formula (A-1), R ¹ to R ⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p is an integer from 0 to 2. However, R ¹ to R ⁴ are never hydrogen atoms at the same time, R ¹ and R ² are not hydrogen atoms at the same time, and R ³ and R ⁴ are not hydrogen atoms at the same time.

In general formula (A-1), the hydrocarbon group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ is preferably a hydrocarbon group having 1 to 10 carbon atoms, for example, and has 1 to 5 carbon atoms. It is more preferable that it is a hydrocarbon group.

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

Examples of hydrocarbon groups having 1 to 30 carbon atoms include methyl group, ethyl group, propyl group, and butyl group.

In the general formula (A-1), examples of the polar groups represented by R ¹ to R ⁴ include, for example, a carboxyl group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. do.

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

p in general formula (A-1) is preferably 1 or 2 from the viewpoint of improving the heat resistance of the film according to the present invention. This is because when p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature is likely to improve.

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

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

R ⁶ in the general formula (A-2) is preferably a carboxyl group, a hydroxy group, an alkoxycarbonyl group, or an aryloxycarbonyl group, and is more preferably an alkoxycarbonyl group or an aryloxycarbonyl group from the viewpoint of ensuring solubility during solution film formation. .

p in the general formula (A-2) is preferably 1 or 2 from the viewpoint of improving the heat resistance of the film according to the present invention. This is because when p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature is likely to improve.

A cycloolefin monomer having a structure represented by general formula (A-2) is preferable because it improves solubility in organic solvents. In general, the crystallinity of organic compounds is reduced by breaking the symmetry, so the solubility in organic solvents is improved. R ⁵ and R ⁶ in the general formula (A-2) are replaced only by ring carbon atoms on one side with respect to the symmetry axis of the molecule, so the symmetry of the molecule is low, that is, expressed in general formula (A-2) Since the cycloolefin monomer having the structure has high solubility, it is suitable for producing films by the solution casting method.

In the polymer of cycloolefin monomers, the content ratio of cycloolefin monomers having a structure represented by general formula (A-2) is, for example, 70 moles relative to the total number of moles of all cycloolefin monomers constituting the cycloolefin resin. % or more, preferably 80 mol% or more, more preferably 100 mol%. When a certain ratio or more of a cycloolefin monomer having a structure represented by general formula (A-2) is included, the orientation of the resin increases, so the phase difference (retardation) value tends to increase.

Hereinafter, specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown as Exemplary Compounds 1 to 14, and specific examples of cycloolefin monomers having a structure represented by general formula (A-2) are given below. Represented by exemplary compounds 15 to 34.

Examples of copolymerizable monomers capable of copolymerizing with cycloolefin monomers include copolymerizable monomers capable of ring-opening copolymerization with cycloolefin monomers and copolymerizable monomers capable of addition copolymerization with cycloolefin monomers.

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

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

Examples of unsaturated double bond-containing compounds include olefin-based compounds having 2 to 12 carbon atoms (preferably 2 to 8 carbon atoms), and examples include ethylene, propylene, and butene.

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

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

The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer is, for example, within the range of 20 to 80 mol%, preferably 30 mol%, relative to the total number of moles of all monomers constituting the copolymer. It may be within the range of 70 mol%.

As described above, the cycloolefin resin is a polymerization or copolymerization of a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2). It is a polymer obtained by, and examples thereof include the polymers (1) to (7) below:

(1) Ring-opening polymer of cycloolefin monomer

(2) Ring-opened copolymer of a cycloolefin monomer and a copolymerizable monomer that can be ring-opened and copolymerized therewith.

(3) Hydrogenated product of the ring-opened (co)polymer of (1) or (2) above

(4) A (co)polymer obtained by cyclizing the ring-opened (co)polymer of (1) or (2) above by the Friedel Crafts reaction and then adding hydrogen.

(5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound

(6) Addition copolymers of cycloolefin monomers with vinyl-based cyclic hydrocarbon monomers and hydrogenated products thereof.

(7) Alternating copolymers of cycloolefin monomers and (meth)acrylates.

All of the polymers (1) to (7) above can be obtained by known methods, for example, the method described in Japanese Patent Application Laid-Open No. 2008-107534 or Japanese Patent Application Laid-Open No. 2005-227606.

· The catalyst and solvent used in the ring-opening copolymerization of (2) above can be, for example, those described in paragraphs 0019 to 0024 of Japanese Patent Application Laid-Open No. 2008-107534.

· The catalyst used for producing the hydrogenated product of (3) and (6) above can be, for example, those described in paragraphs 0025 to 0028 of Japanese Patent Application Laid-Open No. 2008-107534.

· The acidic compound used in the Friedel Crafts reaction of (4) above can be, for example, one described in paragraph 0029 of Japanese Patent Application Laid-Open No. 2008-107534.

The catalyst used in the addition polymerization of (5) to (7) above can be, for example, those described in paragraphs 0058 to 0063 of Japanese Patent Application Laid-Open No. 2005-227606.

· The alternating copolymerization reaction of (7) above can be performed, for example, by the method described in paragraphs 0071 and 0072 of Japanese Patent Application Laid-Open No. 2005-227606.

Among them, the polymers (1) to (3) and (5) above are preferable, and the polymers (3) and (5) above are more preferable.

That is, from the viewpoint of increasing the glass transition temperature of the obtained cycloolefin resin and increasing the light transmittance, the cycloolefin resin contains a structural unit represented by the following general formula (B-1) and the following general formula ( It is preferable to include at least one of the structural units represented by the formula (B-2), only the structural unit represented by the general formula (B-2), or the structural unit represented by the following general formula (B-1): It is more preferable to include both structural units represented by the following general formula (B-2).

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

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

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

The cycloolefin resin used in the present invention may be a commercial product. Examples of commercially available cycloolefin resins include Arton (registered trademark, the same applies hereinafter) G (e.g., G7810, etc.) manufactured by JSR Corporation, Arton F, Arton R (e.g., R4500, R4900, etc.) and R5000, etc.) and Aton RX, etc.

The intrinsic viscosity [η] inh of the cycloolefin resin is preferably in the range of 0.2 to 5 cm3/g, more preferably in the range of 0.3 to 3 cm3/g, and 0.4 to 1.5 cm3/g at 30°C. It is more preferable that it is within the range of In addition, the intrinsic viscosity [η] inh can be measured according to the method described in JIS Z8803 (2011).

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.

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.

The number average molecular weight or weight average molecular weight of the cycloolefin resin can be measured in polystyrene conversion, for example, using gel permeation chromatography (GPC) as follows:

<Gel permeation chromatography>

Solvent: Methylene chloride

Column: Shodex (registered trademark) K806, K805, K803G (used by connecting 3 pieces made by Showa Denko Co., Ltd.)

Column temperature: 25℃

Sample concentration: 0.1 mass%

Detector: RI Model 504 (made by GL Science Co., Ltd.)

Pump: L6000 (made by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0ml/min

Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve based on 13 samples within the range of Mw=500 to 2,800,000 is used. It is desirable to use 13 samples at approximately equal intervals.

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

The glass transition temperature (Tg) of the cycloolefin resin 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 preferably in the range of 120 to 220°C. It is more desirable. When the glass transition temperature (Tg) is 110°C or higher, it is easy to suppress deformation under high temperature conditions. On the other hand, if the glass transition temperature (Tg) is 350°C or lower, molding processing becomes easy, and deterioration of the resin due to heat during molding processing is also easily suppressed. In addition, in this specification, the glass transition temperature can be a value measured by differential scanning calorimetry (DSC).

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

≪Acrylic resin≫

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 a methacrylic resin. Moreover, acrylic resin can also be used individually or in combination of two or more types.

The acrylic resin is not particularly limited, but preferably contains 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable with it.

Other copolymerizable monomers include, for example, alkyl methacrylates with an alkyl number of carbon atoms of 2 to 18, alkyl acrylates with an alkyl number of carbon atoms of 1 to 18, isobornyl methacrylate, and 2-hydroxyethyl. Hydroxyalkyl acrylates such as acrylates, α,β-unsaturated carboxylic acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, and N-vinylpyrroli Divalent carboxylic acids containing unsaturated groups such as 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, anhydrous Maleic acid, maleimide, N-substituted maleimide, glutarimide, glutaric anhydride, etc. can be mentioned.

Excluding glutarimide and glutaric anhydride, copolymerizable monomers that form structural units derived from monomers include the above-mentioned monomers. That is, alkyl methacrylates with an alkyl number of carbon atoms of 2 to 18, alkyl acrylates with an alkyl number of carbon atoms of 1 to 18, and hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate. , α,β-unsaturated carboxylic acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, maleic acid, fumaric acid, and itaconic acid. Unsaturated group-containing divalent carboxylic acids such as styrene, aromatic vinyl compounds such as α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, and N-substituted Monomers such as maleimide can be mentioned.

Additionally, the glutarimide unit can be formed, for example, by reacting an intermediate polymer having a (meth)acrylic acid ester unit with a primary amine (imidizing agent) to imidize it (e.g., Japanese Patent Publication No. 2011) -See Gazette No. 26563).

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

Among the structural units described above, the acrylic resin according to the present invention includes isobornyl methacrylate, acryloylmorpholine, N-hydroxyphenyl methacrylamide, N-vinylpyrrolidone, and styrene from the viewpoint of mechanical strength. , hydroxyethyl methacrylate, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, or glutarimide.

The acrylic resin according to the present invention is used from the viewpoint of controlling dimensional changes in response to changes in environmental temperature, humidity, and atmosphere, and from the viewpoint of improving peelability from a metal support during film production, drying in organic solvents, heat resistance, and mechanical strength. , the weight average molecular weight (Mw) is preferably in the range of 50,000 to 1,000,000, more preferably in the range of 100,000 to 1,000,000, and especially preferably in the range of 200,000 to 800,000. If the weight average molecular weight (Mw) is 50,000 or more, heat resistance and mechanical strength are excellent, and if it is 1,000,000 or less, peelability from the metal support and drying property in organic solvents are excellent. In addition, the weight average molecular weight (Mw) of the acrylic resin is determined by measurement using the gel permeation chromatography (GPC) described above.

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

As the polymerization initiator used, a normal peroxide polymerization initiator or an azo polymerization initiator can be used, and a redox polymerization initiator can also be used. Regarding the polymerization temperature, it may be within the range of 30 to 100°C for suspension or emulsion polymerization, and may be within the range of 80 to 160°C for bulk or solution polymerization. Additionally, in order to control the reduced viscosity of the obtained copolymer, polymerization may be performed using an alkylmercaptan or the like as a chain transfer agent.

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

As the acrylic resin according to the present invention, a commercially available product can also be used. Examples of commercially available products include, for example, Delpet 60N, 80N, 980N, SR8200 (above, manufactured by Asahi Kasei Corporation), Dianal (registered trademark) BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB-218, EMB-229, EMB-270, EMB-273 (above, manufactured by Mitsubishi Chemical Corporation), KT75, TX400S, and IPX012 (above, manufactured by Denka Corporation), etc. I can hear it.

The acrylic resin according to the present invention preferably contains an additive. Examples of preferable additives include acrylic particles (rubber elastomer particles) described in International Publication No. 2010/001668. By adding these additives, it becomes possible to improve the mechanical strength of the film and adjust the rate of dimensional change.

Examples of commercially available acrylic particles include, for example, "Metablen (registered trademark) W-341" manufactured by Mitsubishi Chemical Corporation, "Kaneace (registered trademark)" manufactured by Kaneka Corporation, and " Paralloid”, “Acryloid” manufactured by Rohm & Haas, “Starphylloid (registered trademark)” manufactured by Aika High School Co., Ltd., Chemisnow MR-2G, MS-300X and Kura manufactured by Soken Kagaku Co., Ltd. Examples include “Parapet (registered trademark) SA” manufactured by Les Co., Ltd. These commercial products can be used individually or in combination of two or more types.

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

From the viewpoint of flexibility, the film according to the present invention preferably has a bending elastic modulus of 10.5 GPa or less, more preferably 1.3 GPa or less, and even more preferably 1.2 GPa or less, as measured by the method described in JIS K7171 (2016). The bending elastic modulus varies depending on the type and amount of acrylic resin or rubber elastomer particles in the film. For example, the larger the content of acrylic particles (rubber elastomer particles), the smaller the bending elastic modulus generally becomes.

Additionally, as an acrylic resin, the bending elastic modulus is generally lower when a copolymer such as alkyl methacrylate and alkyl acrylate is used rather than a homopolymer of alkyl methacrylate.

≪Cellulose ester resin≫

In the film according to the present invention, it is also preferable to use cellulose ester resin. Here, the cellulose ester resin refers to a cellulose acyl resin in which some or all of the hydrogen atoms of the 2nd, 3rd, and 6th hydroxy groups (-OH) in the β-1,4 bonded glucose units constituting cellulose are replaced with acyl groups. It refers to rate balance.

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

For example, the hydrogen atom of the hydroxyl group of cellulose has 2 to 2 carbon atoms, such as acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, pivaloyl group, hexanoyl group, octanoyl group, lauroyl group, and stearoyl group. Cellulose ester substituted with an acyl group of 22 can be mentioned.

The carboxylic acid (acyl group) constituting the ester may have a substituent. The carboxylic acid constituting the ester is particularly preferably a lower fatty acid with 6 or less carbon atoms, and more preferably a lower fatty acid with 3 or less carbon atoms. Additionally, the number of acyl groups in the cellulose ester may be one, or a combination of multiple types of acyl groups may be used.

Specific examples of preferred cellulose esters include cellulose acetates such as diacetylcellulose (DAC) and triacetylcellulose (TAC), as well as acetyl groups such as cellulose acetate propionate (CAP), cellulose acetate butyrate, and cellulose acetate propionate butyrate. In addition, mixed fatty acid esters of cellulose to which a propionate group or a butyrate group are bonded may be mentioned.

These cellulose esters can be used individually or in combination of two or more types.

· Type of acyl group and degree of substitution

By adjusting the type and degree of substitution of the acyl group of the cellulose ester, the humidity fluctuation of the phase difference can be controlled to a desired range and the uniformity of the film thickness can be improved. The smaller the degree of substitution of the acyl group of the cellulose ester, the better the retardation properties, making it possible to form a thin film. On the other hand, if the degree of substitution of the acyl group is too small, durability may deteriorate.

As the degree of substitution of the acyl group of the cellulose ester increases, the phase difference does not appear, so it is necessary to increase the stretching ratio when forming the film, but it is difficult to stretch uniformly at a high stretching ratio, and for this reason, there are cases where the film thickness fluctuation increases. (sometimes it gets worse).

In addition, since the Rt humidity fluctuation, which is a retardation (phase difference) in the film thickness direction, is caused by water molecules coordinating with the carbonyl group of cellulose, the higher the degree of substitution of the acyl group, that is, the more carbonyl groups in the cellulose, the more the Rt humidity fluctuation. This tends to get worse.

The cellulose ester preferably has a total degree of substitution within the range of 2.1 to 2.5. By setting it within this range, environmental fluctuations (especially Rt fluctuations due to humidity) can be suppressed and uniformity of film thickness can be improved. From the viewpoint of improving flexibility and stretchability during film formation and further improving film thickness uniformity, it is more preferable that the total degree of substitution is in the range of 2.2 to 2.45.

More specifically, it is preferable that the cellulose ester satisfies both the following formulas (a) and (b). In the following formulas (a) and (b),

Equation (a): 2.1≤X+Y≤2.5

Equation (b): 0≤Y≤1.5.

As for the cellulose ester, cellulose acetate (Y=0) and cellulose acetate propionate (CAP) (Y>0) are more preferable, and cellulose acetate with Y=0 is more preferable from the point of reducing variation in film thickness.

The cellulose acetate that is particularly preferably used is cellulose diacetate (DAC) of 2.1 ≤ X ≤ 2.5 (more preferably 2.15 ≤ )am.

In addition, in the case of Y>0, cellulose acetate propionate (CAP), which is particularly preferably used, satisfies 0.95≤X≤2.25, 0.1≤Y≤1.2, and 2.15≤X+Y≤2.45.

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

Additionally, the degree of substitution of an acyl group indicates the average number of acyl groups per glucose unit, and indicates how many hydrogen atoms of the 2nd, 3rd, and 6th hydroxy groups of one glucose unit are substituted with acyl groups. Therefore, the maximum degree of substitution is 3.0, which in this case means that the hydrogen atoms of the 2nd, 3rd, and 6th hydroxy groups are all substituted with acyl groups.

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

Cellulose acetates with different degrees of substitution may be mixed to obtain desired optical properties. In this case, the mixing ratio of different cellulose acetates is not particularly limited.

The number average molecular weight (Mn) of the cellulose ester resin is preferably within the range of 20,000 to 300,000, further within the range of 20,000 to 120,000, and further within the range of 40,000 to 80,000 from the viewpoint of increasing the mechanical strength of the resulting film roll.

The weight average molecular weight (Mw) of the cellulose ester resin is preferably within the range of 20,000 to 1,000,000, further within the range of 20,000 to 600,000, and further within the range of 40,000 to 400,000 from the viewpoint of increasing the mechanical strength of the resulting film roll. In addition, the number average molecular weight (Mn) and weight average molecular weight (Mw) of the cellulose ester resin are determined by measurement using the gel permeation chromatography (GPC) described above.

The raw material cellulose of cellulose ester resin is not particularly limited, but examples include cotton linter, wood pulp, and kenaf. In addition, the cellulose esters obtained from them can be used by mixing them in any ratio.

Cellulose ester resin can be manufactured by a known method. In general, cellulose as a raw material is mixed with a specified organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic anhydride, propionic acid, etc.), and a catalyst (sulfuric acid, etc.) to esterify the cellulose and form a triester of cellulose. Proceed with the reaction until .

In triester, the three hydroxy groups of the glucose unit are replaced with acylic acid of an organic acid. By using two types of organic acids at the same time, mixed ester type cellulose esters, such as cellulose acetate propionate and cellulose acetate butyrate, can be produced.

Next, a cellulose ester resin having the desired degree of acyl substitution is synthesized by hydrolyzing the triester of cellulose. Afterwards, the cellulose ester resin is completed through processes such as filtration, precipitation, water washing, dehydration, and drying. Specifically, it can be synthesized by referring to the method described in Japanese Patent Application Laid-Open No. 10-45804.

≪Other additives≫

In addition to the thermoplastic resin, the film roll according to the present invention may further contain other additives described below.

<Plasticizer>

The film roll of the present invention preferably contains at least one type of plasticizer for the purpose of providing processability to, for example, a polarizing plate protective film. Among the plasticizers, those containing at least one plasticizer selected from the group consisting of sugar esters, polyesters, and styrene compounds are effective in controlling moisture permeability and are highly compatible with base resins such as cellulose esters. desirable.

The plasticizer preferably has a molecular weight of 15,000 or less, and is preferably 10,000 or less from the viewpoint of improving moisture and heat resistance and compatibility with base resins such as cellulose ester. When the compound having a molecular weight of 10,000 or less is a polymer, the weight average molecular weight (Mw) is preferably 10,000 or less. A more preferable weight average molecular weight (Mw) ranges from 100 to 10,000, and even more preferably from 400 to 8,000.

The content of the plasticizer is preferably in the range of 6 to 40 parts by mass, and more preferably in the range of 10 to 20 parts by mass, based on 100 parts by mass of the thermoplastic resin. Containing it within the above range is preferable because effective control of moisture permeability and compatibility with the base resin can be achieved.

· Sugar ester

The film roll according to the present invention may contain a sugar ester compound for the purpose of preventing hydrolysis. Specifically, as the sugar ester compound, a sugar ester having at least 1 and 12 or less of a pyranose structure or a furanose structure and having all or part of the OH group of the structure esterified can be used. .

· Polyester

The film roll according to the present invention may contain polyester. There are no particular restrictions on the polyester, but for example, a polymer (polyester polyol) whose terminal is a hydroxy group obtained by condensation reaction of dicarboxylic acid or these ester-forming derivatives with glycol, or the polyester polyol. Polymers in which the terminal hydroxy groups are sealed with monocarboxylic acid (end-blocked polyester) can be used. The ester-forming derivative referred to here is an esterified product of dicarboxylic acid, dicarboxylic acid chloride, and anhydride of dicarboxylic acid.

· Styrene compound

A styrene compound may be added to the film roll of the present invention in addition to or instead of the sugar ester and polyester for the purpose of improving the water resistance of the film.

The styrene compound may be a homopolymer of styrene monomer, or may be a copolymer of styrene monomer and another copolymerized monomer. The content ratio of structural units derived from styrene monomer in the styrene compound is preferably within the range of 30 to 100 mol%, more preferably within the range of 50 to 100 mol% in order for the molecular structure to have a volume of a certain level or more. am.

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 alcohol; Alkoxy-substituted styrenes such as p-methoxystyrene, p-tert-butoxystyrene, and m-tert-butoxystyrene; Vinyl benzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; Amide styrenes such as 2-butylamide styrene, 4-methylamide styrene, and p-sulfonamide styrene; 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; Aryl styrenes such as phenyl styrene, indenes, etc. are included. These styrene monomers can be used individually or in combination of two or more types.

<Arbitrary component>

The film roll according to 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 within the range of 0.01 to 20 parts by mass per 100 parts by mass of the thermoplastic resin.

· Antioxidant

As antioxidants, commonly known ones can be used. In particular, lactone-based, sulfur-based, phenol-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be used. These antioxidants are added within the range of 0.05 to 20% by mass, preferably within the range of 0.1 to 1% by mass, relative to the thermoplastic resin.

These antioxidants are preferable because a synergistic effect can be obtained by using a combination of compounds of different types rather than using one type alone. For example, the combined use of lactone-based, phosphorus-based, or phenol-based and double bond-based is preferred.

· Colorant

The film roll according to the present invention preferably contains a colorant for color adjustment within a range that does not impair the effect of the present invention. Here, a colorant means a dye or pigment, and in the present invention, it refers to something that has the effect of changing the color tone of the liquid crystal screen to a blue tone, adjusting the yellow index, or reducing haze. Various dyes and pigments can be used as colorants, but anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

· UV absorber

Since the film roll according to 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 an ultraviolet ray absorbing function.

The ultraviolet absorber is not particularly limited, but examples include ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers, 2-hydroxybenzophenone-based ultraviolet absorbers, or salicylic acid phenyl ester-based ultraviolet absorbers. Specifically, for example, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H- Benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4 -2-hydroxybenzophenone-based ultraviolet absorbers such as octoxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone can be exemplified. These ultraviolet absorbers can be used individually or in combination of two or more types.

The amount of ultraviolet absorber used is not uniform depending on the type of ultraviolet absorber, conditions of use, etc., but is generally preferably within the range of 0.05 to 10% by mass, more preferably 0.1 to 5% by mass, relative to the thermoplastic resin. It is added within the range.

· Fine particles

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

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

By using a combination of particles of different particle sizes and shapes (for example, needle-shaped and spherical, etc.), both transparency and slipperiness can be achieved to a high degree.

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

Specific examples of fine particles containing silicon dioxide include, for example, Aerosil (registered trademark) 200V, Aerosil (registered trademark) R972V, Aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600. , NAX50 (above, manufactured by Nippon Aerosil Co., Ltd.), Seahostar (registered trademark) KEP-10, Seahostar (registered trademark) KEP-30, Seahostar (registered trademark) KEP-50 (above, Nippon Aerosil Co., Ltd.) Kuwait Co., Ltd.), Silophobia (registered trademark) 100 (Fuji Silicia Co., Ltd.), Nipsil (registered trademark) E220A (Nippon Silica Kogyo Co., Ltd.), and Admapain (registered trademark) SO (Registered trademark) SO (Add. Co., Ltd.) Commercially available products with brand names such as Matex) can be preferably used.

The shape of the fine particles may be irregular, needle-shaped, flat, spherical, etc., without limitation, but it is particularly preferable to use spherical particles because the transparency of the resulting film roll can be improved.

If the size of the fine particles is close to the wavelength of visible light, light is scattered and transparency deteriorates. Therefore, it is preferable that the size of the fine particles is smaller than the wavelength of visible light, and is preferably 1/2 or less of the wavelength of visible light. However, if the size of the fine particles is too small, the slipperiness may not be improved, so it is particularly preferable that it be within the range of 80 to 180 nm. Additionally, the size of fine particles means the size of the aggregate (average secondary particle diameter) when the fine particles are aggregates (secondary particles) of primary particles. In addition, when the fine particles are not spherical, it means the diameter of a circle corresponding to the projected area.

The fine particles are preferably added within the range of 0.05 to 10 mass%, more preferably within the range of 0.1 to 5 mass%, relative to the thermoplastic resin.

[Use of film]

The film obtained from the film roll according to the present invention (film according to the present invention) is suitably used as an optical film, such as a protective film for a polarizing plate, and for display in various optical measurement devices, liquid crystal displays, organic electroluminescence displays, etc. Can be used on devices. That is, the present invention provides a polarizing plate containing a film obtained from the film roll of the present invention. The structure of the polarizing plate other than the film according to the present invention is not particularly limited, and conventionally known knowledge can be appropriately employed.

[Film roll manufacturing method]

The manufacturing method of the film roll according to the present invention is not particularly limited, but includes a stretching process of stretching the film while controlling the film thickness deviation Y (unit: ㎛), and the gap between the layers of the film in the roll X measured from the side of the film roll. (unit: ㎛) is a manufacturing method of a film roll, including a winding process of winding the film while controlling the do.

For forming the film according to the present invention, methods such as the usual inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, and hot press method can be used without particular limitation. However, from the viewpoint of suppressing coloring, suppressing foreign matter defects, suppressing optical defects such as die lines, etc., the solution cast film forming method and the melt casting film forming method are preferable, and the solution cast film forming method is more preferable from the viewpoint of obtaining a uniform surface. do.

Hereinafter, the solution casting method and the melt casting film forming method, which are preferred manufacturing methods for the film roll according to the present invention, will be described.

(Film roll manufacturing process by solution casting method)

The manufacturing method of the film by the solution casting process is not particularly limited, but includes a dope preparation process (S1), a casting process (S2), a peeling process (S3), a shrinkage process (S4), a first drying process (S5), 1st stretching process (S6), 1st cutting process (S7), 2nd stretching process (S8), 2nd cutting process (S9), 2nd drying process (S10), 3rd cutting process (S11) and winding process It is preferable to include (S12).

In addition, the manufacturing method does not need to include both the first drying process (S5) and the second drying process (S10), and just needs to include at least one of the processes. Additionally, it is sufficient to include at least one cutting process selected from the group consisting of the first cutting process (S7), the second cutting process (S9), and the third cutting process (S11).

<Dope preparation (stirring preparation) process (S1)>

In the dope preparation (stirring preparation) process (S1), at least resin and the solvent are stirred in the stirring tank 1a of the stirring device 1, and dope flexible on a support body (endless belt) is prepared. As a solvent, a mixed solvent of a good solvent and a poor solvent is used.

Hereinafter, as an embodiment of the present invention, a dope preparation process in the case of using cycloolefin resin (COP) as a thermoplastic resin will be described, but the present invention is not limited to this.

This process is a process of forming a dope by dissolving the COP and other compounds as necessary in a solvent that is mainly a good solvent for the cycloolefin resin (COP) in a melting kiln while stirring, or a solution of the COP. This is a process of preparing dope, the main solution, by mixing solutions of other compounds as needed.

The concentration of the cycloolefin resin (COP) in the dope is preferably thick because it can reduce the drying load after the support is flexible. However, if the COP concentration is too high, the load during filtration increases and accuracy may deteriorate. The concentration that makes these compatible is preferably within the range of 10 to 35 mass%, and more preferably within the range of 15 to 30 mass%.

The solvent used in the dope may be used alone or in combination of two or more types, but it is preferable to use a mixture of a good solvent and a poor solvent of cycloolefin resin (COP) in terms of production efficiency, and it is preferable to use both solvents. A larger number is more preferable in terms of COP solubility.

The range of the preferable mixing ratio of the good solvent and the poor solvent is within the range of good solvent:poor solvent (mass ratio) = 70:30 to 98:2. Good solvents and poor solvents are defined as good solvents that independently dissolve the cycloolefin resin (COP) to be used, and poor solvents that do not swell or dissolve independently. Therefore, the good solvent and poor solvent may change depending on the average degree of substitution of COP.

The good solvent is not particularly limited, but includes organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate, with methylene chloride or methyl acetate being preferred. In addition, the poor solvent is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. Moreover, it is preferable that 0.01-2 mass % of water is contained in dope.

The solvent used to dissolve the cycloolefin resin (COP) may be used by recovering the solvent removed from the film by drying in the film forming process and reusing the solvent. The recovered solvent may contain trace amounts of additives added to the COP, such as plasticizers, ultraviolet absorbers, polymers, and monomer components. However, even if these are contained, they can be suitably reused. If necessary, they can be purified and reused. You may.

As a method for dissolving cycloolefin resin (COP) when producing dope, a general method can be used. Specifically, a method performed at normal pressure, a method performed under pressure below the boiling point of the main solvent, and a method performed under pressure above the boiling point of the main solvent are preferable. By combining heating and pressurization, heating can be performed above the boiling point at normal pressure. Additionally, a method of stirring and dissolving while heating at a temperature that is higher than the boiling point of the solvent at normal pressure and within a range in which the solvent does not boil under pressure is also preferable because it prevents the generation of bulky undissolved substances called gels or lumps. Additionally, a method of mixing the cycloolefin resin (COP) with a poor solvent to wet or swell the resin and then dissolving it by adding a good solvent is also preferably used.

Pressurization may be performed by pressurizing an inert gas such as nitrogen gas or by raising the vapor pressure of the solvent by heating. Heating is preferably performed from the outside, and for example, a jacket type is preferable because temperature control is easy.

A higher heating temperature after adding the solvent is preferable from the viewpoint of solubility of the cycloolefin resin (COP), but if the heating temperature is too high, the required pressure increases and productivity deteriorates. The heating temperature is preferably within the range of 30 to 120°C, more preferably within the range of 60 to 110°C, and still more preferably within the range of 70 to 105°C. Additionally, the pressure is adjusted so that the solvent does not boil at the set temperature.

A cooling dissolution method is also preferably used to dissolve the cycloolefin resin (COP), and thereby the cycloolefin resin (COP) can be dissolved in a solvent such as methyl acetate.

It is preferable to filter the obtained cycloolefin resin (COP) solution (dope during or after dissolution) using an appropriate filter medium such as filter paper. As a filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matter, etc., but if the absolute filtration accuracy is too small, clogging of the filter medium tends to occur. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with an absolute filtration accuracy in the range of 0.001 to 0.008 mm is more preferable, and a filter medium with an absolute filtration accuracy in the range of 0.003 to 0.006 mm is even more preferable.

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

It is preferable to remove and reduce impurities, especially bright point foreign substances, contained in the raw material cycloolefin resin (COP) by filtration. Bright point foreign matter means that two polarizers are placed in a cross-Nicol state, a film, etc. is placed between them, light is exposed from one side of the polarizer, and when observed from the other side of the polarizer, light from the opposite side appears. It is a point (foreign matter) that appears to be leaking, and the number of bright points with a diameter of 0.01 mm or more is preferably 200 points/cm2 or less.

The number of bright spots with a diameter of 0.01 mm or more is more preferably 100 points/cm2 or less, further preferably 50 points/cm2 or less, and even more preferably 0 to 10 points/cm2 or less. Additionally, it is preferable to have fewer bright spots with a diameter of less than 0.01 mm.

Filtration of the dope can be performed by a normal method, but a method of filtering while heating at a temperature that is higher than the boiling point of the solvent at normal pressure and within a range where the solvent does not boil under pressurized pressure is the difference in filtration pressure before and after filtration (differential pressure). The rise is small, which is desirable.

The preferable temperature for filtration is in the range of 30 to 120°C, more preferably in the range of 45 to 70°C, and even more preferably in the range of 45 to 55°C. Additionally, it is preferable that the filtration pressure is small. Specifically, the filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and still more preferably 1.0 MPa or less.

<Flexible process (S2)>

In the casting process (S2), the cast film formed by dope cast on the support is heated on the support, and the solvent is evaporated until the cast film can be peeled from the support with a peeling roll. Evaporation is preferably performed at a temperature within the range of 5 to 75°C.

To evaporate the solvent, there are a method of blowing warm air onto the upper surface of the flexible membrane, a method of transferring heat from the back side of the support using a liquid, a method of transferring heat from the front and back using radiant heat, etc. However, the method of transferring heat from the front and back using radiant heat is used for drying. It is desirable because it has good efficiency. Additionally, a method of combining them is also preferably used.

From the viewpoint of productivity, the width of the casting (cast) is preferably 1.3 m or more, and more preferably within the range of 1.3 to 4.0 m. If the casting width is 4.0 m or less, streaks do not occur in the manufacturing process and stability in the subsequent conveyance process increases. From the viewpoint of transportability and productivity, the casting width is more preferably within the range of 1.3 to 3.0 m.

The support used in the casting process (S2) is preferably one with a mirror-finished surface, and a stainless steel belt or drum with a cast surface finished by plating is preferably used.

The surface temperature of the support in the casting process (S2) is preferably within the range of -50°C to the boiling point of the solvent, and a higher temperature is preferable because it can speed up the drying rate of the cast film. The surface temperature of the support is more preferably in the range of 0 to 55°C, and even more preferably in the range of 22 to 50°C.

The method of controlling the temperature of the support is not particularly limited, but includes a method of blowing warm or cold air or a method of contacting hot water with the back side of the support. The use of hot water is preferable because heat transfer is carried out efficiently and the time until the temperature of the support becomes constant is short. When using warm air, there are cases where wind with a temperature higher than the target temperature is used.

According to some embodiments, in the casting process (S2), the dope prepared in the dope preparation process (S1) is fed to the casting die through a pressurized constant-quantity gear pump or the like through a conduit, and the rotary drive stainless steel is infinitely transported. The dope is stretched from a casting die to a casting position on a support comprising a steel endless belt.

A method for increasing the uniformity of the film thickness in the casting process (S2) includes a method of controlling the slit gap of the lip portion of the casting die in both the solution casting method and the melt casting film forming method. For example, when extruding dope (including melt) with high viscosity, the slit gap varies in the width direction, but to prevent this, the slit gap is controlled by installing a plurality of heat bolts in the width direction. There is a way to do it. However, this method has a problem in that there is a physical installation limit to the number of heat bolts.

Additionally, in order to suppress pressure fluctuations in the width direction that cause fluctuations in the width direction of the slit gap, there is a method of changing the internal structure of the flexible die in the width direction. However, there is a problem that flexible dies must be switched for each production type, which takes time and costs.

· Initial discharge film thickness control by heat bolt of flexible die

Controlling the initial discharge film thickness using heat bolts of the flexible die is one of the means for controlling the film thickness of the film according to the present invention.

The flexible die is provided with a mechanism for adjusting the slit through which dope is discharged (in the case of melting, the resin is extruded) in the width direction. By the heat bolt of the casting die, the gap in the width direction of the slit through which dope is discharged is adjusted so that the film thickness deviation immediately after discharge is within the range of 1.0 to 5.0% with respect to the entire cast film, so that the initial discharge film thickness of the cast film is It is desirable to exercise control.

· etc

The point where the dope of the flexible die slit comes out is called the lip, but a flexible die that allows the slit shape of the lip portion to be adjusted and makes it easy to uniform the film thickness is preferable. Flexible dies include coat hanger dies and T dies, but all are preferably used.

In addition, in this specification, a cast film refers to a dope film cast from the lip portion described above.

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

In the casting process (S2), flexible dope is dried on a support body to form a cast film. At that time, the inclination of the casting die, that is, the discharge direction of the dope from the casting die to the support, may be appropriately set so that the angle with respect to the normal line of the surface of the support (the surface on which the dope is cast) is within the range of 0 to 90 degrees.

The support body is comprised, for example, of a stainless steel belt, and is held by a pair of rolls and a plurality of rolls positioned between them. At this time, it is preferable that the surface of the support is mirror-finished. At least one of the pair of rolls is provided with a drive device that applies tension to the support, and thereby the support is used in a state in which tension is applied and stretched.

Additionally, the support may be a drum.

<Peeling process (S3)>

In this process, in the casting process (S2), the solvent is evaporated until the film strength is sufficient to enable peeling of the cast film on the support, followed by dry solidification or cooling solidification, before the film moves around the support. is peeled off from the support. That is, this process is a process of peeling the film from which the solvent has evaporated on the support at the peeling position.

At this time, from the viewpoint of cotton quality, moisture permeability, and peelability, it is preferable to peel the film from the support within the range of 30 to 600 seconds. In addition, the position where the film is peeled from the support is called a peeling point, and the roll that assists the peeling is called a peeling roll.

In the peeling step (S3), the film is peeled with a peeling roll while maintaining self-supporting properties. The temperature at the peeling point on the support is preferably within the range of -50 to 40°C, more preferably within the range of 10 to 40°C, and still more preferably within the range of 15 to 30°C.

· Residual solvent amount

The amount of residual solvent in the film on the support during peeling is appropriately adjusted depending on the strength of the drying conditions, the length of the support, etc. Although it may vary depending on the thickness of the film, if the amount of residual solvent at the peeling point is too large, the film may become too flexible and difficult to peel, and the flatness may be damaged, or may traverse or tilt due to peeling tension. Vertical stripes may easily occur. Conversely, if the amount of residual solvent is too small, part of the film may peel off along the way.

In order for the film to exhibit good flatness, it is preferable that the residual solvent amount is within the range of 10 to 50 mass% from the viewpoint of balance between economic speed and quality.

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

Methods include a method of adding a poor solvent for the cycloolefin resin (COP) to the dope and gelling the cast film after casting the dope, and a method of gelling the cast film by cooling the support and peeling it in a state containing a large amount of residual solvent. . Additionally, there is also a method of adding a metal salt to the dope.

As described above, the flexible film is gelled on the support to strengthen the film, thereby speeding up peeling and increasing the film forming speed.

Additionally, the residual solvent amount is defined by the following formula:

Residual solvent amount (mass%) = {(M-N)/N} × 100

In the above formula, M is the mass of a sample collected at an arbitrary point in time during or after manufacturing the flexible membrane or film, and N is the mass after M is heated at 115°C for 1 hour.

The peeling tension when peeling the support and the film is preferably 300 N/m or less. The peeling tension is more preferably 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.

<Shrinkage process (S4)>

The shrinking process (S4) is a process of shrinking the film in-plane. This shrinking process is performed by stretching the film after peeling from the support in the conveyance direction (Machine Direction, hereinafter also referred to as “MD direction”). In this case, the film shrinks in the width direction (Traverse Direction, hereinafter also referred to as “TD direction”) perpendicular to the MD direction within the film plane.

The shrinkage process promotes entanglement between polymer molecules (matrix molecules) in the film thickness direction. As a result, even when the film and the polarizer are bonded through an adhesive during the production of the polarizing plate, the adhesive becomes easy to penetrate into the inside of the film through the entangled portion (crosslinked portion) between matrix molecules. As a result, the film can be firmly fixed to the polarizer through the adhesive, thereby improving the peeling strength of the film with respect to the polarizer. In other words, good adhesion between the film and the polarizer can be secured.

· Definition of shrinkage rate

In this specification, the shrinkage rate is defined by the following equation:

Shrinkage rate [%] = width of the film at the end of the shrinkage process [mm] / width of the film at the start of the shrinkage process [mm] x 100.

In the shrinkage step (S4), if the shrinkage rate of the film is too small, the effect of promoting entanglement between matrix molecules will be insufficient, and if it is too large, there is concern that the production efficiency of the film (stretched film) will decrease. For this reason, the shrinkage rate of the film in the shrinkage step (S4) is preferably within the range of 1 to 40%, and more preferably within the range of 5 to 20%.

·Measuring and calculating method of shrinkage rate

In this specification, the width of the film can be measured using LS-9000 manufactured by Keyence Corporation. In addition, the shrinkage rate of the film according to the present invention is obtained by substituting the average value of each value measured every 1 second for 5 minutes (300 seconds) by the measuring device described above into the above equation as the film width. , there is no need to be limited to the above-mentioned method, and for example, the value read from the normal value for the width of the film may be used as the width of the film and substituted into the above equation.

In the shrinking step (S4), the film is shrunk in the width direction. Methods for shrinking the film include, for example, (1) treating the film at a high temperature without retaining its width to increase the density of the film, or (2) applying tension to the film in the conveyance direction (MD direction). , (3) shrinking the film in the width direction (TD direction), and (3) drastically reducing the amount of residual solvent in the film.

<First drying process (S5)>

The first drying step (S5) is a step of heating the film on a support to evaporate the solvent. Within the drying apparatus, the film is transported by a plurality of transport rolls arranged in a zigzag shape when viewed from the side, and the film is dried in the meantime.

The drying method in the drying device is not particularly limited and generally includes methods using hot air, infrared rays, heating rolls, microwaves, etc., but from the viewpoint of simplicity, the method of drying the film with hot air is preferable. Additionally, a method of combining them is also desirable. In addition, the first drying process (S5) may be performed as needed.

If the film thickness is thin, drying is fast, but if drying is too rapid, the flatness of the finished film is likely to be damaged. When drying at high temperature, it is necessary to consider the amount of residual solvent. However, by ensuring that the amount of residual solvent is not too large, defects due to foaming of the solvent can be prevented. It is better to perform drying at a high temperature such that the residual solvent amount is 30% by mass or less. Throughout, drying is carried out within a range of approximately 30 to 250°C. In particular, it is preferable to dry within the range of 35 to 200°C, and it is preferable to gradually increase the drying temperature.

In addition, the amount of residual solvent in the film on the support at the time of peeling in the peeling step (S3) is appropriately adjusted depending on the strength and weakness of the drying conditions, the length of the support, etc., and the above-described residual solvent in the shrinking step (S4) Since the amount is greatly influenced by the film thickness, resin, etc., the peeling step (S3) and the shrinkage step (S4) have a range that overlaps with the preferred range of the residual solvent amount.

The temperature of the support may be the same throughout, or may vary depending on the position. In the first drying step (S5), the film is peeled from the support using a drying device and dried.

In the film drying process, a roll drying method (a method of drying the film by passing it alternately through a plurality of rolls arranged above and below) or a tenter method of drying the film while conveying it is generally adopted.

When using a tenter stretching device, a device that can independently control the gripping length (distance from the start of gripping to the end of gripping) of the film from the left and right by the left and right gripping means of the tenter stretching device in the stretching process described later is used. It is desirable to do so.

Additionally, in the stretching process, it is also desirable to intentionally create sections with different temperatures to improve planarity. Additionally, it is also desirable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

<First stretching process (S6)>

The stretching process may be a process of stretching the film within the film plane only in the MD direction, may be a process of stretching only in the TD direction, may be in both the MD and TD directions, or may be a process of stretching in the diagonal direction. do.

Additionally, there are no restrictions on the stretching direction, but from the viewpoint of obtaining a wide film, it is preferable to have a process that includes stretching in at least the width direction. This stretching can be performed using a stretching device.

In order to secure a high phase difference, secure a wide width, and promote adhesive penetration when adhering to a polarizer, it is preferable to stretch the film at a high magnification during the stretching process. However, if the stretching ratio is too high, craze may occur in the film due to stretching stress, or entanglement between matrix molecules that maintain the film strength may dissociate, making the film brittle. For this reason, the draw ratio in the stretching step 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.

In addition, when stretching is performed multiple times, it is preferable that among the plurality of stretching, the stretching at the highest magnification, which has the highest risk of dissociation of matrix molecules, is performed at the last time. For example, stretching at the highest magnification is preferably performed in the second stretching step (S8). In this case, since the entanglement of the matrix molecules can be strengthened even when stretched at the highest magnification, dissociation of the entanglement of the matrix molecules can be suppressed and cohesive failure can be suppressed even when stretched at the highest magnification.

In the first stretching step (S6), the film is stretched by a tenter stretching device. The stretching method at this time is a method of stretching in the conveyance direction (MD direction) by providing a peripheral speed difference between the rolls, or a tenter method of stretching the film in the width direction (TD direction) by fixing both side edges of the film with clips, etc. It is desirable because it improves performance, productivity, planarity, and dimensional stability.

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

In the film forming process, the width retention or transverse stretching is preferably performed using a tenter stretching device, which may be a pin tenter or a clip tenter. Additionally, in the tenter stretching device, drying may be performed in addition to stretching.

However, the inside of the tenter stretching device is provided with a preheating zone, a (transverse) stretching zone, and a heat setting zone. Zones are separated by curtains. Additionally, inside each zone, hot air is supplied from above or below the film F, or from both sides. Hot air is blown out uniformly in the width direction of the film while maintaining a predetermined temperature for each zone. Thereby, the inside of each zone is controlled to the desired temperature. Below, each zone is explained.

The preheating zone is a zone in which the film is preheated, and the film is heated without widening the gap between the clips. In this preheating zone, it is preferable that local heating is performed on the film in order to set the film thickness deviation Y including the film edge to a desired value.

Examples of local heating means include infrared (IR) heaters and hot air, but there is no particular limitation, and heat treatment may be performed by other means.

The advantage of the hot air type is that it has sufficient film thickness adjustment capability regardless of the material. In the present invention, it is preferable from the viewpoint of film thickness controllability and stability to perform local heating with infrared (IR) heaters arranged in the width direction (TD direction) and conveyance direction (MD direction) of the film.

Infrared (IR) heaters on the film are regularly arranged in one row or multiple rows in the film transport direction, as shown in Figures 6 (a), (b), and (c) (Figure 6 ( a) shows 1 row in the film transport direction, Figure 6(b) shows 2 rows in the film transport direction, and Figure 6(c) shows 5 rows in the film transport direction). Additionally, the infrared (IR) heater may be arranged zigzagly in the conveyance direction.

In Fig. 6, P1, P2, and P3 represent the pitch of the heat source portion installation interval of each infrared heater.

Here, each heat source part in the infrared (IR) heater is the central part of each infrared (IR) heater, as is clear with reference to Figures 6 (a), (b), and (c).

The form of the infrared (IR) heater in the present invention is not limited, and the heat source portion of the actual infrared (IR) heater has a shape such as point, line, or plane. In the present invention, the “infrared (IR) The term “heat source portion of the heater” refers to the central portion of the heat source portion of the actual infrared (IR) heater, even if the actual infrared (IR) heater takes any form such as point, line, or plane.

≪Infrared (IR) heater≫

Details of the infrared (IR) heater used in the present invention will be described. As an infrared (IR) heater used in the present invention, unlike general infrared (IR) heaters, a heater designed to pinpoint narrow the irradiation range of infrared rays by using a mirror that reflects infrared rays is preferable. .

Examples of mirrors that reflect infrared rays include cold mirrors (manufactured by Sigma Goki Co., Ltd.) and infrared aluminum multi-reflection mirrors (manufactured by Novo Optics). The mirror used in the examples of the present invention is an infrared aluminum thick reflection mirror (manufactured by Novo Optics), which is a mirror using aluminum.

The irradiation range of infrared rays of one current general infrared (IR) heater, for example, is 500 mm in the width direction in the far-infrared heater product number MCHNNS3 (irradiation energy 400 W, manufactured by Misumi Corporation), whereas in the present invention, it is 500 mm in the width direction. The irradiation range of infrared rays from one infrared (IR) heater (manufactured by Heat Tech Co., Ltd.) used was 550 W of irradiation energy and 100 to 150 mm in the width direction.

Although not shown, in the tenter stretching device, the infrared (IR) heater is disposed only above the nozzle so that the film does not come into contact with the infrared (IR) heater when the film breaks.

By bringing the infrared (IR) heater closer to the film, the radiant energy from the infrared (IR) heater can be concentrated in a narrower range. Therefore, it is desirable to bring the infrared (IR) heater as close to the film as possible without interfering with the width forming operation by the clip. Specifically, the distance from the film to the infrared (IR) heater is preferably within the range of 30 to 120 mm.

Additionally, it is preferable to use the infrared (IR) heater with a heating width of 100 to 250 mm. In addition, “heating width” refers to the width heated by the infrared (IR) heater until the heating intensity becomes 0.2 when the heating intensity immediately below the infrared (IR) heater is set to 1.

The installation interval (pitch) of the heat source portion of the infrared (IR) heater is preferably 10 to 300 mm, more preferably 15 to 200 mm, and even more preferably 20 to 150 mm. Additionally, the infrared (IR) heater preferably has an irradiation energy of 100 to 1,000 W and heats within the range of 150 to 400°C.

By adjusting the installation interval of the heat source part of the infrared (IR) heater, the irradiation energy, the heating temperature, etc., the above-described film thickness deviation Y can be controlled.

The film preheated in the preheating zone moves to the transverse stretching zone. The transverse stretching zone is a zone in which the film is transversely stretched in the width direction by widening the interval between clips. The draw ratio in this transverse stretching treatment 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.

The film transversely stretched in the transverse stretching zone moves to the heat setting zone.

In addition, in this embodiment, the interior of the tenter stretching device is divided into a preheating zone, a (transverse) stretching zone, and a heat setting zone, but the type and arrangement of the zones are not limited to this, for example, after the transverse stretching zone. , a cooling zone may be provided to cool the film. Additionally, a heat relief zone may be provided among the heat fixation zones.

In addition, in this embodiment, only horizontal stretching may be performed with a tenter stretching device, or stretching may be performed simultaneously in the vertical direction. In this case, when the clip is moved, the pitch of the clip (the spacing between clips in the conveyance direction) can be changed. As a mechanism for changing the pitch of the clip, for example, a pantograph mechanism or a linear guide mechanism can be used.

Methods for stretching the film include stretching in the vertical (transport) direction (vertical stretching), stretching in the horizontal (width) direction (transverse stretching), and stretching in the longitudinal and transverse directions in order (sequential biaxial stretching). , a method of performing longitudinal stretching and transverse stretching simultaneously (simultaneous biaxial stretching). Among these, when transverse stretching or simultaneous biaxial stretching (including diagonal stretching) is performed, a tenter stretching device is used.

A tenter stretching device is a device that stretches a film by holding both ends of the film in the width direction with clips and expanding the gap while running the clips together with the film.

· Heat treatment timing

A tenter stretching device is usually divided into multiple zones, for example, a preheating zone for heating the film, a transverse stretching zone for stretching the film in the transverse direction, a heat fixing zone for crystallizing the film, and a relaxation zone for removing thermal stress of the film. Zones, etc. are provided.

· Furnace temperature

Usually, the temperature inside the stretching furnace is preferably within the range of 120 to 200°C, and more preferably within the range of 120 to 180°C. Here, the furnace temperature in the present invention is the temperature measured at a position 100 mm above the center of the film immediately before stretching in the stretching zone of the tenter stretching device described later, and the value of each temperature every 1 minute is measured for 1 hour. Measurements were taken and their average values were calculated.

Here, when a temperature gradient is provided in the conveyance direction in a plurality of sections, the section for heat treatment is the target of the furnace temperature. In addition, in the present invention, the temperature inside the furnace is different when the heat treatment is not performed in the stretching zone, but when the heat treatment is performed in the stretching zone, the temperature inside the furnace is the same as that in the stretching zone before heat treatment. This refers to the temperature inside the furnace.

· Residual solvent amount

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.

<First cutting process (S7)>

In the first cutting process (S7), the cutting unit including the slitter cuts both ends in the width direction of the film stretched in the first stretching process (S6). In a film, the portion remaining after cutting both ends constitutes a product portion that becomes a film product. On the other hand, the part cut from the film may be recovered and reused as part of the raw material for forming the film.

<Second stretching process (S8)>

In the second stretching step (S8), the film is stretched using a stretching device, similar to the first stretching step (S6). The stretching method at this time includes a method of stretching in the conveyance direction (MD direction) by providing a difference in the peripheral speed of the roll, or a tenter method of securing both side edges of the film with clips, etc. and stretching it in the width direction (TD direction). It is desirable because it improves performance, productivity, planarity, and dimensional stability. Additionally, in the stretching device, drying may be performed in addition to stretching.

<Second cutting process (S9)>

In the second cutting process (S9), similarly to the first cutting process (S7), the cutting part containing the slitter cuts both ends in the width direction of the formed film. Additionally, the holding portions of the clips at both ends of the film are usually excised because the film is deformed and cannot be used as a product. If the material has not deteriorated due to heat, it is recovered and reused. In a film, the portion remaining after cutting both ends constitutes a product portion that becomes a film product. On the other hand, the part cut from the film is recovered and reused as a part of the raw material for forming the film.

<Second drying process (S10)>

In the second drying process (S10), like the first drying process (S5), the film is dried in a drying device. Within the drying apparatus, the film is transported by a plurality of transport rolls arranged in a zigzag shape when viewed from the side, and the film is dried in the meantime.

The drying method in the drying device is not particularly limited, and generally includes methods using hot air, infrared rays, heating rolls, or microwaves. Among these drying methods, the method of drying the film using hot air is preferable from the viewpoint of simplicity. In addition, the second drying process (S10) may be performed as needed.

<Third cutting process (S11)>

In the third cutting process (S11), similarly to the first cutting process (S7) and the second cutting process (S9), the cutting part containing the slitter cuts both ends in the width direction of the formed film. In a film, the portion remaining after cutting both ends constitutes a product portion that becomes a film product. On the other hand, the part cut from the film is recovered and reused as a part of the raw material for forming the film.

<Winding process (S12)>

Finally, in the winding process (S12), the film is wound by a winding device to obtain a film roll. That is, in the winding process (S12), a film roll is manufactured by winding the film onto a winding core while conveying it.

The winding tension when winding up the film in the winding process is not particularly limited, but is preferably within the range of 10 to 300 N/m, and preferably within the range of 20 to 200 N/m. By adjusting this winding tension, the gap between the film layers can be controlled. The winding tension may be constant during the winding process, or may be changed during the winding process.

· Residual solvent amount

More specifically, this process is a process of winding the film with a winding device after the amount of residual solvent in the film becomes 2% by mass or less. Preferably, the amount of residual solvent is set to 0.4% by mass or less to produce a film with good dimensional stability. can be obtained.

In particular, it is preferable to wind up the amount of residual solvent within the range of 0.00 to 0.20 mass%.

(Winding method)

The film winding method can be any method that uses a commonly used winder, and for example, tension control methods such as the constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress can be used. There are, and you can use them separately. Before winding, the ends may be slitted to the width of the product, and surface modification treatment other than knurling may be performed on both ends of the film to prevent sticking or scratches during winding.

In this process, the gap between film layers can be controlled by appropriately adjusting the pressing amount (touch pressure) of the touch roll that contacts and presses the film wound on the winding shaft.

The touch roll has a pressing amount control device that controls the pressing amount, and it becomes possible to control the gap between film layers by adjusting the pressing amount. The pressing amount control device is disposed at both ends of the touch roll.

The relationship between the touch roll and tension control (winding tension) is the following equation described in the literature (J.K.Good Modeling Nip Induced Tension in Wound Rolls) Proceedings of Forth International Conference on Web Handling, 1997);

Based on the thinking of TW (winding tension) = Th (conveyance tension) + μN (μ: friction coefficient, N: touch pressure), the optimal radial stress and circumferential stress during winding that do not cause defects are set. It is possible.

As the material of the touch roll, metal or a material made by wrapping resin, rubber, etc. around a metal roll can be used. Additionally, a crown roll whose diameter changes as it moves from the center in the width direction to the side can also be used. As the core material, aluminum, iron, CFRP (carbon fiber reinforced plastics), etc. can be used. Additionally, a chrome coated surface as surface treatment, an elastic roll, etc. may be used as the touch roll. The number of touch rolls may be one or two or more.

The pressing amount (touch pressure) of the touch roll is not particularly limited, but is preferably more than 5 N/m and less than 80 N/m, more preferably 7 to 60 N/m, and even more preferably 10 to 50 N/m. The winding tension may be constant during the winding process, or may be changed during the winding process.

(Film roll manufacturing process by melt casting method)

The film according to the present invention can also be formed by a melt casting method. The “melt casting method” refers to a method of heating and melting a composition containing a thermoplastic resin and the above-mentioned additives to a temperature showing fluidity, and then casting the melt containing the fluid thermoplastic resin.

Molding methods for heating and melting can be specifically classified into melt extrusion molding, press molding, inflation, injection molding, blow molding, and stretch molding. Among these molding methods, the melt extrusion molding method is preferable in terms of mechanical strength, surface precision, etc.

Hereinafter, the melt casting film forming method is explained.

According to some embodiments, the method of manufacturing a film roll by a melt casting process includes an extrusion process (M1), a casting/molding process (M2), a first stretching process (M3), a first cutting process (M4), and a first stretching process (M3). It includes a second stretching process (M5), a second cutting process (M6), and a winding process (M7).

In addition, the manufacturing method by the melt-cast film forming method does not need to include both the first stretching process (M3) and the second stretching process (M5), and just needs to include at least one of the processes. In addition, the 1st cutting process (M4) and the 2nd cutting process (M6) should just contain at least one process similarly.

<Extrusion process (M1)>

In the extrusion process (M1), at least the thermoplastic resin is melt-extruded using an extruder and molded on a cast drum. It is desirable to knead the thermoplastic resin in advance and pelletize it.

Pelletization may be performed by a known method. For example, dried resin, plasticizer, and other additives are supplied to the extruder through a feeder, kneaded using a single- or double-screw extruder, extruded into strands from a flexible die, cooled in water or air, and cut to form pellets. You can get angry.

The additive may be mixed into the thermoplastic resin before being supplied to the extruder, or the additive and the thermoplastic resin may each be supplied to the extruder through separate feeders. In order to mix a small amount of additives uniformly, it is preferable to mix them in the thermoplastic resin in advance.

When introducing pellets from the supply hopper to the extruder, it is preferable to do so under vacuum, reduced pressure, or an inert gas atmosphere to prevent oxidative decomposition, etc. In addition, the extruder is preferably processed at a temperature that can be pelletized and as low as possible to suppress shear force and prevent thermoplastic resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.).

For example, in the case of a twin-screw extruder, it is desirable to use a deep groove type screw and rotate it in the same direction. From the uniformity of kneading, the meshing type is preferable. When the resin/pellets are melted, it is preferable to filter them using a leaf disk type filter or the like to remove foreign substances.

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

<Flexing/Molding Process (M2)>

In the stretching/molding process (M2), the resin/pellets melted in the extrusion process are stretched into a film shape from the casting die through a conduit through a pressurized constant-dispensing gear pump, etc., and are infinitely transported using a rotation-driven stainless steel endless cast. Molten resin/pellets are cast from a casting die at the casting position on the drum. Then, the flexible molten resin pellet is molded on a cast drum to form a flexible film.

The inclination of the flexible die, that is, the discharge direction of the molten resin/pellets from the flexible die to the support, is an angle of 0 to 90° with respect to the normal line of the surface of the cast drum (the surface on which the molten resin/pellets are flexible). Just set it appropriately so that it is within the range.

The film may be formed by appropriately using a cooling drum that assists the touch roll or cast drum, either individually or in combination of two or more.

The method for increasing the uniformity of film thickness in the casting/forming process (M2) is the same as the casting process (S2) in the film roll manufacturing process by the solution casting method described above, and the peeling process ( Descriptions such as the amount of residual solvent in S3), the shrinkage rate in the shrinkage step (S4), and the drying method in the first drying step (S5) are also omitted because they are redundant.

<First stretching process (M3)>

In the first stretching process (M3), the film is stretched by a stretching device. The stretching method at this time is a method of stretching in the MD direction by providing a difference in the peripheral speed of the roll, or a tenter method of stretching in the TD direction by fixing both side edges of the film with clips, etc., which improves the performance, productivity, planarity, and dimensional stability of the film. It is desirable because it improves. Additionally, in the stretching device, drying may be performed in addition to stretching.

Regarding the tenter stretching device, local heating method, heat treatment timing, furnace temperature, stretching temperature, and residual solvent amount, the first stretching step (S6) in the film roll manufacturing method by the solution casting method is described. It is omitted as it is redundant.

<First cutting process (M4)>

In the first cutting process (M4), the cutting unit including the slitter cuts both ends of the formed film in the width direction. In a film, the portion remaining after cutting both ends constitutes a product portion that becomes a film product. On the other hand, the part cut from the film may be recovered and reused as part of the raw materials for forming the film.

<Second stretching process (M5)>

In the second stretching process (M5), the film is stretched using a stretching device as in the first stretching process (M3). The stretching method at this time is a method of stretching in the MD direction by providing a difference in the peripheral speed of the roll, or a tenter method of stretching in the TD direction by fixing both side edges of the film with clips, etc., which improves the performance, productivity, planarity, and dimensional stability of the film. It is desirable because it improves. Additionally, in the stretching device, drying may be performed in addition to stretching.

<Second cutting process (M6)>

In the second cutting process (M6), similarly to the first cutting process (M4), the cutting part including the slitter cuts both ends of the formed film in the width direction. In a film, the portion remaining after cutting both ends constitutes a product portion that becomes a film product. On the other hand, the part cut from the film may be recovered and reused as part of the raw materials for forming the film.

<Winding process (M7)>

Finally, in the winding process (M7), the film is wound by a winding device to obtain a film roll. That is, in the winding process, a film roll is manufactured by winding the film onto a winding core while conveying it. The details of this process are the same as the winding process (S12) described above, so description is omitted here.

The film roll according to the present invention is preferably a long film, and specifically, the total length of the film roll is preferably within the range of 100 to 12,000 m. Additionally, the width of the film roll according to the present invention is preferably within the range of 400 to 3,000 mm.

Although embodiments of the present invention have been described in detail, it is clear that this is explanatory and illustrative and is not limiting, and the scope of the present invention should be interpreted in accordance with the appended claims.

The present invention includes the following aspects and forms:

1. It is a film roll without a knurling portion, and the gap between the film layers in the roll measured from the side of the film roll is X (unit: ㎛), and the film thickness deviation including the film end is Y (unit: ㎛). When a film roll satisfies the following equations (1) and (2);

2. The film roll according to 1. above, wherein the standard deviation σ of the film interlayer voids within the roll, the voids between film layers within the roll, and the voids between film layers outside the roll of the film roll is 0.15 or less;

3. The film roll according to 1. or 2. above, comprising a cycloolefin resin;

4. A stretching process of locally heating the film using a plurality of infrared heaters and stretching the film while controlling the film thickness deviation Y (unit: ㎛) including the film edge, and measuring from the side of the film roll. A method for producing a film roll, comprising a winding process of winding the film while controlling the interlayer gap X (unit: ㎛) of the film, wherein Manufacturing method of film roll, which satisfies;

5. A polarizing plate comprising a film obtained from the film roll described in any of 1. to 3. above.

[Example]

The effect of the present invention will be explained using the following examples. However, the technical scope of the present invention is not limited to the following examples. In the following examples, the notations “%” and “part” are used, but unless otherwise specified, “% by mass” and “part by mass” are indicated.

[Example 1]

<Production of film roll>

The solution casting method was used to form the film.

(Dope preparation process (S1))

<Synthesis of cyclic polyolefin resin P-1>

100 parts by mass of purified toluene and 100 parts by mass of norbornenecarboxylic acid methyl ester were added to the stirring device. Next, 25 mmol% ethylhexanoate-Ni (to monomer mole) dissolved in toluene, 0.225 mol% tri(pentafluorophenyl)boron (to monomer mole) and 0.25 mol% triethylaluminum (to monomer mole) dissolved in toluene. mole) was added to the stirring device. The reaction was carried out for 18 hours while stirring at room temperature (25°C). After completion of the reaction, the reaction mixture was poured into excess ethanol to produce precipitation of the polymer. The precipitate was purified, and the obtained cyclic polyolefin resin (cycloolefin resin (COP)) (P-1) was dried under vacuum at 65°C for 24 hours.

The weight average molecular weight (Mw) of the cyclic polyolefin resin (P-1) measured by the following gel permeation chromatography (GPC) was 140,000:

<Gel permeation chromatography>

Solvent: Methylene chloride

Column: Shodex (registered trademark) K806, K805, K803G (used by connecting 3 pieces made by Showa Denko Co., Ltd.)

Column temperature: 25℃

Sample concentration: 0.1 mass%

Detector: RI Model 504 (made by GL Science Co., Ltd.)

Pump: L6000 (made by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0ml/min

Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve based on 13 samples within the range of Mw=500 to 2,800,000 was used.

<Preparation of fine particle dispersion (M-1)>

A fine particle dispersion (M-1) with the following composition was prepared:

4 parts by mass of fine particles (Aerosil (registered trademark) R812: manufactured by Nippon Aerosil Co., Ltd., average primary particle size: 7 nm, average secondary particle size: 100 nm, apparent specific gravity 50 g/L)

76 parts by mass of dichloromethane

20 parts by mass of ethanol.

25 parts by mass of the cyclic polyolefin resin (P-1) obtained above, 65 parts by mass of dichloromethane, 10 parts by mass of ethanol, and 0.75 parts by mass of the fine particle dispersion (M-1) were placed in a mixing tank and stirred to dissolve each component, It was filtered through filter paper with an average pore diameter of 34 μm and a sintered metal filter with an average pore diameter of 10 μm to prepare a cyclic polyolefin resin solution (Dope D-1).

(Flexible process (S2))

The dope for film forming (cyclic polyolefin resin composition COP1) prepared in the dope preparation process (S1) was fed to the flexible die through a conduit through a pressure-type constant metering gear pump. Dope was casted to a width of 1800 mm on a film forming line from a casting die at a casting position on a support body containing a rotary driven stainless steel endless belt that feeds infinitely. It was heated on the support until the dope had self-supporting properties, and it was dried by evaporating the solvent until the cast film could be peeled from the support with a peeling roll, thereby forming a cast film.

Additionally, the length of the conduit from the pump to the flexible die was set to 30 m, the gear ratio of the gear pump used for dope liquid delivery was adjusted, and the rotation speed of the pump was set to 70 rpm.

With the heat bolt of the casting die, the gap in the width direction of the slit through which dope is discharged was adjusted so that the film thickness deviation immediately after discharge was 5.5% with respect to the entire cast film, and the initial discharge film thickness of the cast film was controlled.

After drying the flexible film on the belt until the residual solvent amount reached 5% by mass and forming a film on the surface layer, warm air was blown at a wind speed of 45 m/sec (40°C) to flatten the protrusions.

(Peeling process (S3))

In the casting process (S2), after forming the cast film, the cast film was peeled from the support with a peeling roll while maintaining self-supporting properties.

(Shrinkage process (S4))

The film was treated at a high temperature without maintaining the width, thereby increasing the density of the film, thereby shrinking the film to a shrinkage rate of 7% in the width direction.

(First drying process (S5))

The film was then heated on the support to evaporate the solvent. The amount of residual solvent in the film was measured by the following method and was 5% by mass or less:

(Measurement of residual solvent amount)

The amount of residual solvent was calculated by gas chromatography as follows. That is, a piece of film was collected from a random location, and in order to prevent volatilization of the solvent remaining in the film, it was quickly placed in a vial and capped. Next, a needle was inserted into the vial, and mass analysis was performed using a gas chromatograph (manufactured by Agilent Technology Co., Ltd.). Additionally, the residual solvent amount is defined by the following formula:

Residual solvent amount (mass%)={(M-N)/N}×100

M in the above formula is the mass (g) of the sample taken at any time during or after manufacturing the flexible membrane or film, and N in the above formula is the mass (g) after heating the sample at 115°C for 1 hour. am.

(First stretching process (S6) (local heating, adjustment of Y))

After that, the film was conveyed in a tenter stretching device heated with hot air at 140°C, and the film was horizontally stretched while locally heating the film.

<Local heating means>

As a local heating means, an infrared (IR) heater was used. The heat source portion of each infrared (IR) heater on the film was positioned at a distance of 75 mm from the film surface. Additionally, the heating width was set to 150 mm (the heating width at which the intensity becomes 0.2 when the intensity immediately below the infrared (IR) heater is set to 1). Each heat source part of the infrared (IR) heater was set at 180 to 350°C at a rating of 750W.

<Arrangement of infrared (IR) heaters and installation interval of heat source>

Infrared (IR) heaters were arranged in two rows in the conveyance direction, as shown in Fig. 6(b), and the heat source portion installation interval of each infrared (IR) heater was set at a pitch of 50 mm.

(First cutting process (S7))

Both ends of the stretched film in the width direction were cut.

(Second stretching process (S8))

The film was stretched using a tenter stretching device in the same manner as in the first stretching step (S6), except that the temperature of the hot air was set to 180°C. The amount of residual solvent in the film was measured by the same method as above, and was found to be 1 to 5% by mass.

(Second cutting process (S9))

Similarly to the first cutting process, both ends of the stretched film in the width direction were cut.

(Second drying process (S10))

Similar to the first drying process (S5), the film was heated on the support to evaporate the solvent. The amount of residual solvent in the film was measured by the method described above and was found to be 0.1 to 2% by mass.

(Third cutting process (S11))

Similarly to the first cutting process (S7) and the second cutting process (S9), both ends of the stretched film in the width direction were cut.

(Winding process (S12))

The above film was wound. The winding tension was 40 N/m, taper 70%, and corner 25%. From the start of winding to the end of winding, the pressing amount of the touch roll (TR) was fixed at 16 N/m. The film roll width was 2,000 mm, the winding length was 7,800 m, and the line speed for transporting the film was 60 m/min.

Film roll No. 1 was produced through the above steps.

[Example 2]

In the first stretching step (S6), film roll No. 2 was produced in the same manner as in Example 1, except that the installation interval of the heat source portion of each infrared (IR) heater was set to a pitch of 200 mm.

[Example 3]

In the winding process (S12), film roll No. 3 was produced in the same manner as in Example 2, except that the winding tension was set to 20 N/m.

[Example 4]

In the first stretching step (S6), the installation interval of the heat source portion of each infrared (IR) heater is set to a pitch of 15 mm, and in the winding step (S12), the winding tension is set to 80 N/m, and the touch roll (TR) Film roll No. 4 was produced in the same manner as in Example 1, except that the pressing amount was set to 36 N/m.

[Example 5]

In the winding process (S12), the pressing amount of the touch roll (TR) at the start of winding is set to 32 N/m, and at the stage of winding 3,000 m, the pressing amount of the touch roll (TR) is changed to 16 N/m, and the pressing amount of the touch roll (TR) is changed to 5,000 m. Film roll No. 5 was produced in the same manner as in Example 1, except that the pressing amount of the touch roll (TR) was changed to 8 N/m in the m winding step.

[Example 6]

In the winding process (S12), the pressing amount of the touch roll (TR) at the start of winding is set to 8 N/m, and at the stage of winding 3,000 m, the pressing amount of the touch roll (TR) is changed to 16 N/m, and the pressing amount of the touch roll (TR) is changed to 5,000 m. Film roll No. 6 was produced in the same manner as in Example 1, except that the pressing amount of the touch roll (TR) was changed to 32 N/m in the m winding step.

[Example 7]

In the winding process (S12), the pressing amount of the touch roll (TR) at the start of winding is set to 40 N/m, and at the stage of winding 3,000 m, the pressing amount of the touch roll (TR) is changed to 12 N/m, and the pressing amount of the touch roll (TR) is changed to 5,000 N/m. Film roll No. 7 was produced in the same manner as in Example 1, except that the pressing amount of the touch roll (TR) was changed to 40 N/m in the m winding step.

[Example 8]

To form the film, a melt casting method was used.

(Extrusion process (M1))

In the same procedure as in Example 1, cyclic polyolefin resin (P-1) was prepared, pelletized, and additives (fine particles, Aerosil (registered trademark) R812: manufactured by Nippon Aerosil Co., Ltd., average primary particle size) : 7 nm, average secondary particle diameter: 100 nm, apparent specific gravity 50 g/L) was supplied to the extruder, melted in the extruder, and extruded in a film form from a flexible die onto a cast drum through a pressurized constant-dispensing gear pump. .

(Flexing/Molding Process (M2))

In the extrusion process (M1), the length of the pipe from the pump to the casting die was set to 60 m, the gear ratio of the gear pump used for liquid feeding was adjusted, and the rotation speed of the pump was set to 20 rpm.

The initial discharge film thickness of the cast film was controlled by adjusting the gap between the widths of the slits through which the dope is discharged to 1.5% with respect to the entire cast film immediately after discharge using the heat bolt of the cast die. The extruded resin was molded by cooling with a cooling drum to form a cast film.

(First stretching process (M3) (local heating, adjustment of Y))

After that, the cast film was conveyed within a tenter stretching device and stretched horizontally. At that time, local heating was performed using an infrared (IR) heater. The heat source portion of each infrared (IR) heater on the film was located at a distance of 75 mm from the film surface. Additionally, the heating width was set to 150 mm (the heating width at which the intensity becomes 0.2 when the intensity immediately below the infrared (IR) heater is set to 1). Each heat source part of the infrared (IR) heater was set at 180 to 350°C at a rating of 750W.

<Arrangement of infrared (IR) heaters and installation interval of heat source>

Infrared (IR) heaters were arranged in two rows in the conveyance direction, as shown in Fig. 6(b), and the heat source portion installation interval of each infrared (IR) heater was set at a pitch of 50 mm.

(First cutting process (M4))

Both ends of the stretched film in the width direction were cut.

(Second stretching process (M5))

Similar to the first stretching process, the film was stretched using a tenter stretching device.

(2nd cutting process (M6))

Similarly to the first cutting process, both ends of the stretched film in the width direction were cut.

(Winding process (M7))

The above film was wound. The winding tension was 40 N/m, taper 70%, and corner 25%. From the start of winding to the end of winding, the pressing amount of the touch roll (TR) was fixed at 16 N/m. The film roll width was 2,000 mm, the winding length was 7,800 m, and the line speed for transporting the film was 60 m/min.

Film roll No. 8 was produced through the above steps.

[Example 9]

Film roll No. 9 was produced in the same manner as in Example 1, except that triacetylcellulose (TAC, weight average molecular weight: 300,000) was used instead of cyclic polyolefin resin (P-1).

[Example 10]

In the winding process (S12), the pressing amount of the touch roll (TR) at the start of winding is set to 32 N/m, and at the stage of winding 3,000 m, the pressing amount of the touch roll (TR) is changed to 13 N/m, and the pressing amount of the touch roll (TR) is changed to 5,000 m. Film roll No. 10 was produced in the same manner as in Example 1, except that the pressing amount of the touch roll (TR) was changed to 7 N/m in the m winding step.

[Comparative Example 1]

In the first stretching process (S6), the installation interval of the heat source part of each infrared (IR) heater is changed to a pitch of 10 mm, and in the winding process (S12), the pressing amount of the touch roll (TR) is changed to 80 N/m. Except for the changes, film roll No. 11 was produced in the same manner as in Example 1.

[Comparative Example 2]

Example except that heating by an infrared (IR) heater was not performed in the first stretching step (S6), and the pressing amount of the touch roll TR was set to 5 N/m in the winding step (S12). In the same manner as 1, film roll No. 12 was produced.

[Comparative Example 3]

In the winding process (S12), film roll No. 13 was produced in the same manner as in Comparative Example 2, except that the pressing amount of the touch roll TR was set to 16 N/m.

[Comparative Example 4]

In the first stretching step (S6), the installation interval of the heat source portion of each infrared (IR) heater is set to a pitch of 100 mm, and in the winding step (S12), the pressing amount of the touch roll (TR) is set to 8 N/m. Except this, film roll No. 14 was produced in the same manner as in Example 1.

[Comparative Example 5]

Dope preparation process (S1) - the 3rd cutting process (S11) were performed similarly to Example 1.

(Knurled processing process)

After that, the film was irradiated with laser light to form a knurled portion (site A). The knurled width of both ends was 15 mm from the film end. The line speed for transporting the film was 60 m/min.

As the laser device, a carbon dioxide gas laser device was used. The output of the laser device was 20 W, the center wavelength of the outgoing light wavelength was 9.4 μm, and the outgoing light wavelength range was ±0.01 μm or less centered on the center wavelength.

Laser light is irradiated to the film by reflecting the collimated beam emitted from the carbon dioxide laser device with two galvano mirrors and concentrating it on the surface of the conveyed film through an fθ lens (focal length 200 mm). It was done.

By controlling the angle of the galvano mirror, the light collection position was moved in the direction of the film plane, thereby controlling the irradiation trajectory of the laser light onto the film surface.

(Atmospheric pressure plasma treatment process: surface modification treatment)

AGP-500 manufactured by Gasga Denki Co., Ltd. was installed on the back side of the knurled portion of the film and irradiated with 0.5 kW. The distance between the probe emitting atmospheric pressure plasma and the film was set to 5 mm. The installation position was set so that the atmospheric pressure plasma to be irradiated could be irradiated with a width of 110% of the knurling width from the film back side facing the knurled portion.

(Winding process (S12))

The above film was wound. The winding tension was 40 N/m, taper 70%, and corner 25%. From the start of winding to the end of winding, the pressing amount of the touch roll (TR) was fixed at 8 N/m. The film roll width was 2,000 mm, the winding length was 7,800 m, and the line speed for transporting the film was 60 m/min.

Film roll No. 15 was produced through the above steps.

[Comparative Example 6]

In the winding process (S12), the pressing amount of the touch roll (TR) at the start of winding was set to 16 N/m, and the pressing amount of the touch roll (TR) was changed to 5 N/m at the stage of winding 3,000 m. In the same manner as Comparative Example 5, film roll No. 16 was produced.

The manufacturing conditions and configurations of the film rolls of each Example and Comparative Example are shown in Table 1 below.

[measurement]

<Gap between film layers>

The imaging device of FIG. 2, which includes the imaging unit shown in FIG. 1 and has the system configuration shown in FIG. 3, was installed on the side of the film roll as shown in FIG. 5, and the side of the film roll was photographed. The measurement was performed centering on a point located outside 50% of the roll side surface from the winding core (a point at 50% of the film roll diameter, point B in Figs. 4 and 5) to calculate the gap between layers of the film in the roll. Measure the burn. Similarly, 20% of the winding outside from the winding core on the end face of the roll body (point at 20% of the film roll diameter, point A in FIG. 5) has an interwinding film interlayer void and 80% of the winding outside from the winding core on the end face of the roll body (point A of the film roll diameter). Images for calculating the voids between film layers outside the circle at 80% of the points and point C in FIG. 5 were measured, respectively. Measured image data was acquired, edge emphasis processing was performed on the acquired image data, and processed images (for example, images within the thick frames of FIGS. 4 and 5) were obtained. Additionally, the radial length was measured using the center position of the processed image as the starting point and the position in the 100th layer toward the outside of the winding as the end point, and the gap between each film layer was calculated using the following equation:

In addition, the high-brightness line light 3 shown in FIG. 1 is a white line light (product number: LNSP2-100SW) manufactured by CCS Corporation, and the telecentric lens 4 is a product manufactured by Moritex Corporation. Number: MML1-HR130VI-35F (magnification ) were used, respectively.

<Film thickness including film end>

The film thickness of the film was determined using a film thickness meter SI-T10 manufactured by Keyence Corporation. In the width direction, the film thickness at 100 points including the film edge was measured online. Additionally, regarding the conveyance direction, 7,800 points per 1 m were measured online. That is, for a film roll with a total length of 7,800 m, the film thickness of 100 points in the width direction x 7,800 points in the conveyance direction = 780,000 points in total was measured.

The film thickness used in calculating the gap between film layers within the roll is the average value of the film thickness at 100 points in the width direction measured at the point when the film roll reaches 20% of the diameter (at the point where the winding length is 1,100 m). The film thickness used in calculating the gap between film layers in a roll is the average value of the film thickness at 100 points in the width direction measured at the point where the film roll reaches 50% of the diameter (at the point where the winding length is 3,200 m). The film thickness used in calculating the gap between the outer film layers is the average value of the film thicknesses of 100 points in the width direction measured at the point where the film roll reaches 80% of the diameter (at the point where the winding length is 5,800 m).

The film thickness deviation Y including the film end in the above formula (2) is the film thickness deviation (maximum film thickness) at 100 points in the width direction (at the time of the winding length of 3,200 m) measured for calculation of the interlayer void of the film in the roll. -is the minimum value of the film thickness).

In addition, in each Example and Comparative Example, the average film thickness of the film along the entire length of the film roll was all 35 μm.

[evaluation]

<Winding misalignment>

The film rolls obtained in each Example and Comparative Example were subjected to an acceleration of 5.8 m/s ² in the width direction for 30 minutes in a vibration test, and the amount of left and right deviation was measured. As a vibration tester, TR1000 manufactured by IMV Corporation was used. If the evaluation rank is ○ to △, it is practical:

Evaluation rank of winding misalignment

○: Misalignment amount less than 2 mm

△: Misalignment amount of 2 mm or more and less than 10 mm

×: Misalignment amount of 10 mm or more.

<Application>

Films were fed from the film rolls obtained in each Example and Comparative Example, and the state of sticking (hereinafter also referred to as blocking) of the overlapping films was visually observed and evaluated based on the following criteria. If the evaluation rank is ○ to △, it is practical:

Evaluation Rank

○: No blocking

△: Blocking is at a weak level, but there is no problem in practical terms.

×: Blocking is at a level other than the above (level claimed by the user)

In addition, the "level with weak blocking" in the evaluation rank Δ is a level at which it is difficult to determine whether it is affixed or not.

For the film rolls of Examples and Comparative Examples, the results of the various measurements and evaluations described above are shown in Table 2 below.

As is clear from Table 2 above, it was found that the film rolls of the examples had further reduced sticking and winding misalignment. On the other hand, it was found that in the film roll of the comparative example, at least one of sticking and winding misalignment deteriorated.

1: Half mirror
2: Total reflection mirror
3: High-brightness line lighting
4: Telecentric lens
5: Monochrome sensor camera
6: Measurement surface of film roll (winding end surface)
10: Imaging unit
20: winding core

Claims (5)

If it is a film roll without a knurling portion, and the gap between the film layers in the roll measured from the side of the film roll is X (unit: ㎛), and the film thickness deviation including the film end is Y (unit: ㎛), A film roll that satisfies the following equations (1) and (2).
The film roll according to claim 1, wherein the standard deviation σ of the film interlayer voids within the roll, the voids between the film layers within the roll, and the voids between the film layers outside the roll of the film roll is 0.15 or less. 3. The film roll according to claim 1 or 2, comprising a cycloolefin resin. A stretching step of locally heating the film using a plurality of infrared heaters and stretching the film while controlling the film thickness deviation Y (unit: ㎛) including the film edge,
A winding process of winding the film while controlling the space between the layers of the film in the roll,
A method of manufacturing a film roll, comprising:
The method for producing a film roll, wherein the X and the Y satisfy the following equations (1) and (2).
A polarizing plate comprising a film obtained from the film roll according to claim 1 or 2.