Core tube for film roll, film roll and manufacturing method of film roll

Abstract

The invention provides a core tube for film winding, which can restrain the winding sagging of a film roll and make the cutting end face uniform. The invention discloses a core tube for film rolling. The core tube for film rolling is a metal core tube, and the dynamic balance of the core tube is 1450 g or below.

Description

Technical Field

[0001] The present invention relates to a core tube for winding a film, a film roll including the core tube for winding a film and a film, and a method for manufacturing a film roll using the core tube for winding a film.

[0002] For example, without limitation, the present invention relates to a core tube for winding a polyvinyl alcohol-based film (hereinafter sometimes referred to as "PVA-based film"), a film roll including the core tube for winding a PVA-based film and a PVA-based film (hereinafter sometimes referred to as "PVA-based film roll"), and a method for manufacturing a PVA-based film roll using the core tube for winding a PVA-based film. Background Art

[0003] Film rolls made by winding various films onto a core tube can be used to manufacture a variety of products. For example, PVA-based films are used in many applications as films with excellent transparency, and as one useful application, polarizing films can be cited. Polarizing films can be used, for example, as basic components of liquid crystal displays.

[0004] When manufacturing a polarizing film, for example, first a long strip of PVA-based film is formed by a continuous casting method using an aqueous solution of a polyvinyl alcohol-based resin as a forming material, then both side ends are cut off (trimmed) to make the width a designed value, and it is wound onto a cylindrical core tube, thereby manufacturing a PVA-based film roll. Then, the PVA-based film is unwound from the PVA-based film roll and subjected to dyeing and uniaxial stretching, etc., thereby manufacturing a polarizing film.

[0005] The polarizing film thus manufactured is required to have excellent uniformity of optical properties such as polarization for use in liquid crystal displays, etc., and it is required that the PVA-based film and the PVA-based film roll as its original roll do not have defects such as wrinkles and creases during winding and unwinding, etc.

[0006] In order to meet the above requirements, the present applicant proposed a core tube made of aluminum and having a surface roughness set at 100S or less as a core tube for winding a PVA-based film (see Patent Document 1).

[0007] In addition, the present applicant proposed a core tube made of carbon fiber reinforced plastic and having a modulus of elasticity set at 98 GPa or more as a core tube for winding a PVA-based film (see Patent Document 2).

[0008] When manufacturing this core tube, it is manufactured through the following steps: producing a sheet (prepreg) obtained by infiltrating a thermosetting resin into a carbon cloth formed by plain weaving or twill weaving, etc. of carbon fibers, winding one layer or multiple layers of the sheet (prepreg) around the outer peripheral surface of a cylindrical or tubular mold (mandrel), then putting it into a furnace and heating to form a carbon fiber reinforced plastic cured into a tubular shape on the outer peripheral surface of the mold (mandrel), and after extracting the tubular carbon fiber reinforced plastic from the mold (mandrel), performing surface grinding.

[0009] Prior art documents

[0010] Patent documents

[0011] Patent document 1: Japanese Patent Application Laid-Open No. 2004-106377

[0012] Patent document 2: Japanese Patent Application Laid-Open No. 2006-205536 Summary of the invention

[0013] Problems to be solved by the invention

[0014] The core tube for winding a PVA-based membrane in Patent Document 1 is more likely to bend than that in Patent Document 2. Therefore, especially when increasing the axial length to wind a PVA-based membrane with a large winding width, it is difficult to sufficiently suppress defects such as winding sag and uneven cutting end faces generated in the PVA-based membrane roll, and there is room for improvement.

[0015] In addition, the core tube for winding a PVA-based membrane in Patent Document 2 has less bending than that in Patent Document 1, and can suppress core tube rotational vibration during the winding of the PVA-based membrane. Therefore, a PVA-based membrane roll with excellent appearance can be obtained. However, its manufacturing method is complex or cumbersome. Therefore, there is still room for improvement from the viewpoints of manufacturing cost and manufacturing preparation time.

[0016] The present invention provides a core tube for winding a membrane roll that can suppress winding sag of the membrane roll and improve the uniformity of the cutting end face under such a background.

[0017] Solutions to solve the problems

[0018] In the process of repeatedly and intensively studying in view of the above circumstances, the present inventors focused on the behavior of the core tube during rotation and the influence of the above behavior on the membrane and the membrane roll. The present inventors further repeatedly studied centering on this view, and as a result, found that by using a core tube that satisfies specific conditions, winding sag of the membrane roll can be suppressed and the cutting end face can be made uniform.

[0019] That is, the present invention has the following aspects. [1]

[0021] A core tube for winding a membrane roll

[0022] The above core tube for winding a membrane roll is a metal core tube and its dynamic balance is 1450 g or less. [2]

[0024] The core tube for winding a membrane roll according to [1], wherein the above membrane is a polyvinyl alcohol-based membrane. [3]

[0026] The core tube for winding a membrane roll according to [1] or [2], wherein the above metal is aluminum alloy. [4]

[0028] The core tube for retrieving a film roll according to any one of [1] to [3], wherein the axial length of the core tube for retrieving a film roll is 0.5 to 7.0 m. [5]

[0030] The core tube for retrieving a film roll according to any one of [1] to [4], wherein the outer diameter of the core tube for retrieving a film roll is 75 to 350 mm. [6]

[0032] The core tube for retrieving a film roll according to any one of [1] to [5], wherein the mass of the core tube for retrieving a film roll is 30 to 200 kg. [7]

[0034] The core tube for retrieving a film roll according to any one of [1] to [6], wherein the film is a polyvinyl alcohol-based film for manufacturing a polarizing film. [8]

[0036] The core tube for retrieving a film roll according to any one of [1] to [7], wherein the dynamic balance is 1200 g or less. [9]

[0038] A polyvinyl alcohol-based film roll, which comprises the core tube for retrieving a film roll according to any one of [1] to [8] and a polyvinyl alcohol-based film wound around the core tube.

[10]

[0040] A method for manufacturing a polyvinyl alcohol-based film roll, which includes a step of using the core tube for retrieving a film roll according to any one of [1] to [8] to wind a polyvinyl alcohol-based film.

[0041] Effects of the Invention

[0042] According to the core tube for retrieving a film roll of the present invention, the winding sag of the film roll can be suppressed and the uniformity of the cutting end face can be improved.

[0043] In addition, according to the PVA film roll obtained by using the PVA film roll retrieving core tube as an example of an embodiment of the present invention, a polarizing film having excellent optical properties can be provided. Description of the Drawings

[0044] Figure 1 A perspective view schematically showing an embodiment of a film roll using the core tube for retrieving a film roll of the present invention.

[0045] Figure 2 An explanatory view schematically showing an embodiment of the manufacturing process of a film roll using the core tube for retrieving a film roll of the present invention.

[0046] Figure 3It is an explanatory drawing schematically showing an embodiment of a manufacturing process of a film roll using the film roll take-up core tube of the present invention.

[0047] Figure 4 It is a side view schematically showing an embodiment of a film roll using the film roll take-up core tube of the present invention.

[0048] Figure 5 It is an explanatory drawing schematically showing a dynamic balance testing machine for measuring dynamic balance. Detailed Embodiments

[0049] Hereinafter, the present invention will be described based on examples of modes for carrying out the present invention. However, the present invention is not limited to the embodiments described below.

[0050] It should be noted that in this specification, when expressed as "X to Y" (X and Y are arbitrary numbers), unless otherwise specifically stated in advance, it means "X or more and Y or less" and also includes the meaning of "preferably larger than X" or "preferably smaller than Y".

[0051] In addition, in this specification, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the meaning of "preferably larger than X" or "preferably smaller than Y".

[0052] Furthermore, in this specification, "X or / and Y" (X and Y are arbitrary components) means at least one of X and Y, and means three meanings: only X, only Y, and X and Y.

[0053] In this specification, for numerical ranges described in stages, the upper limit value or the lower limit value of a certain stage's numerical range can be arbitrarily combined with the upper limit value or the lower limit value of other stages' numerical ranges. In addition, in the numerical ranges described in this specification, the upper limit value or the lower limit value of this numerical range can be replaced with the values shown in the examples.

[0054] In this specification, the "main component" refers to a component that has a greater influence on the characteristics of the object, and the content of this component is usually 50% by mass or more in the object, preferably 55% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more and can be 100% by mass.

[0055] [Film Roll Take-up Core Tube]

[0056] Figure 1 It is a perspective view showing a film roll produced using a film roll take-up core tube (1) according to an embodiment of the present invention (hereinafter, sometimes referred to as "this film roll take-up core tube (1)").

[0057] The core tube (1) for taking up the film roll is characterized in that its dynamic balance is below 1450 g. By controlling the dynamic balance of the core tube for taking up the film roll below 1450 g, the uniformity of the cut end face of the obtained film roll can be improved, the winding sag of the film roll can be suppressed, and the eccentricity of the film roll can be suppressed.

[0058] According to such a film roll, the film discharge state can be made uniform. For example, in the manufacturing process of a polarizing film, the PVA-based film roll of an embodiment of the present invention can make the discharge state of the PVA-based film uniform, and a polarizing film with excellent optical properties can be obtained.

[0059] It should be noted that the cut end face of the film roll refers to Figure 1 the side end face (S) of the film roll shown in the figure. The uniformity of the cut end face refers to the degree of deviation of the axial position of the end edge of the film among the films. It can be said that the smaller this deviation is, the more excellent the uniformity of the cut end face is. In addition, the winding sag of the film roll refers to, for example, Figure 4 the degree of the difference (T2 - T1) between the upper thickness (T1) and the lower thickness (T2) of the film roll shown in the figure. It can be said that the smaller this difference is, the more the winding sag of the film roll is suppressed and the smaller the eccentricity of the film roll is.

[0060] Although the reason for achieving the above excellent effects by using the core tube (1) for taking up the film roll is not necessarily clear, according to the investigation of the present inventors, it is presumed that because the dynamic balance of the core tube for taking up the film roll is controlled within the above range, the eccentricity of the film roll is suppressed and the stability of the tension during film winding tends to increase. As a result, the uniformity of the cut end face of the film roll increases and the winding sag is suppressed.

[0061] From the viewpoint of improving the uniformity of the cut end face of the film roll and suppressing the winding sag, the dynamic balance of the core tube (1) for taking up the film roll is preferably below 1200 g, more preferably below 1000 g, further preferably below 800 g, and particularly preferably below 600 g. The above dynamic balance can be appropriately set within the above range. For example, it can be below 500 g, below 400 g, below 350 g, etc. It should be noted that it is ideal that the lower limit value of the dynamic balance of the core tube (1) for taking up the film roll is close to 0, and there is no particular limitation. It is preferably, for example, 1 g, preferably 5 g in practice, and particularly preferably 10 g.

[0062] Regarding the method of adjusting the dynamic balance of the core tube (1) for taking up the film roll to the above range, there is no particular limitation, but examples include: (a) a method of grinding a part of the core tube for taking up the film roll, a method of perforating; (b) a method of installing a balance weight at a predetermined position of the core tube for taking up the film roll; a method of performing both the above (a) and (b), etc.

[0063] Regarding the method of grinding or perforating a part of the core tube for taking up the film roll in the above (a), examples include: a method of grinding a part of the outer peripheral surface or the inner peripheral surface of the core tube for taking up the film roll obtained by extrusion molding or the like to form a thin-walled portion, and a method of forming a through hole penetrating from the outer peripheral surface to the inner peripheral surface direction of the core tube for taking up the film roll obtained by extrusion molding. However, from the viewpoint of excellent workability, a method of grinding a part of the outer peripheral surface or the inner peripheral surface to form a thin-walled portion is preferred, and from the viewpoint of particularly excellent workability, a method of grinding a part of the outer peripheral surface to form a thin-walled portion is particularly preferred. Regarding the method of grinding a part of the outer peripheral surface or the inner peripheral surface of the core tube for taking up the film roll, there is no particular limitation, and a known grinding machine can be used.

[0064] Regarding the method of mounting the balance weight at a predetermined position on the core tube for taking up the film roll in the above (b), an example is a method of mounting the balance weight on the inner peripheral surface or the outer peripheral surface of the core tube for taking up the film roll obtained by extrusion molding or the like. Specifically, an example is a method of mounting the balance weight on the inner peripheral surface of the core tube for taking up the film roll obtained by extrusion molding using an adhesive or a bonding agent or the like. There is no particular limitation on the material of the above balance weight, and lead, which is a soft material and has good workability, is ideal.

[0065] In addition, there is no particular limitation on the mounting position of the above balance weight, but from the viewpoint of avoiding buffering with the core tube support bodies or the like provided at both ends of the core tube for taking up the film roll, it is preferably mounted at a predetermined position in the middle part of the inner peripheral surface of the core tube for taking up the film roll except for the both end parts in the axial direction (length direction). There is no particular limitation on the axial length of the both end parts, but it can be, for example, about 350 mm for each of the both ends.

[0066] It should be noted that the "dynamic balance" in the present invention means so-called two-plane unbalance and is represented by the unbalance mass [g] on a predetermined plane and the unbalance mass [g] on the other plane different from the predetermined plane. The dynamic balance can be measured according to JIS B 0905 (1992) by a method commonly used by those skilled in the art. The left dynamic balance and the right dynamic balance of the present core tube (1) for taking up the film roll are each 1450 or less and preferably within the above range.

[0067] For example, a known dynamic balancing tester (refer to Figure 5 ) can be used for measurement. Specifically, refer to Figure 5, support both ends of the core tube for taking up the film roll on the bearing part (B), install a belt (V) for transmitting the rotation of the motor (M) to the core tube for taking up the film roll (1) on the outer peripheral surface of the core tube for taking up the film roll (1), and rotate it in a state where both ends of the core tube for taking up the film roll (1) are supported by the bearing part (B). According to JIS B 0905 (1992), detect the unbalance signal generated by this rotation at the left and right bearing parts, and obtain the unbalance mass or position (phase) of the left and right sides of the core tube for taking up the film roll through calculation.

[0068] Specifically, for example, install a vibration detection sensor and a rotation position detection sensor for detecting the rotation position (angle) of the core tube at the bearing part of the dynamic balance testing machine, and the control device of the dynamic balance testing machine has an arithmetic device for calculating the dynamic balance and angle of the core tube based on the detection signals from these sensors. The above vibration detection sensor is various sensors that can detect the vibration of the core tube and is, for example, an acceleration sensor, a velocity sensor, etc. The above rotation position detection sensor detects the rotation angle of the core tube relative to the reference position and is an optical or magnetic detector.

[0069] If the core tube is rotated and the rotation speed reaches a predetermined speed, the vibration is detected by the vibration detection sensor, the rotation angle is detected by the rotation position detection sensor, and the unbalance mass and position (phase) are calculated by the arithmetic control device based on the detection signals.

[0070] The shape of this core tube for taking up the film roll (1) is cylindrical. The material of this core tube for taking up the film roll (1) is metal, and from the viewpoints of manufacturing cost and strength, aluminum alloy is particularly ideal. For aluminum alloy, there is no particular limitation, and aluminum alloys containing silicon and magnesium can be cited. Heat-treatable aluminum alloys containing silicon and magnesium are particularly preferred.

[0071] It should be noted that in this specification, the core tube for taking up the film roll (1) being made of metal generally means that more than 90% of the entire core tube is composed of metal, more preferably more than 95%, further preferably more than 97%, particularly preferably more than 99%, and particularly preferably a core tube composed only of metal.

[0072] For example, this core tube for taking up the film roll (1) is preferably made of aluminum alloy, and preferably more than 90% of the entire core tube is composed of aluminum alloy, more preferably more than 95%, further preferably more than 97%, particularly preferably more than 99%, and particularly preferably a core tube composed only of aluminum alloy.

[0073] In addition, the metal core tube for taking up the film roll (1) can be in a form where, for example, the surface of the core tube is covered with a material other than metal (such as carbon, etc.).

[0074] Regarding the core tube (1) for taking up the film roll, from the viewpoints of, for example, manufacturing cost and manufacturing preparation time, it is ideal to measure the dynamic balance of the core tube for taking up the film roll made of aluminum alloy obtained by extrusion molding and adjust the dynamic balance by the above method (a) or / and (b) to obtain the core tube (1) for taking up the film roll. In particular, from the viewpoints of further reducing the manufacturing cost and further shortening the manufacturing preparation time, it is ideal to measure the dynamic balance of the core tube for taking up the film roll made of aluminum alloy obtained by extrusion molding and adjust the dynamic balance by the above method (b) to obtain the core tube (1) for taking up the film roll.

[0075] The axial length of the core tube (1) for taking up the film roll depends on the width of the film (2), but is usually 0.5 to 7.0 m. For example, when winding a PVA-based film, from the viewpoint of coping with the widening of the width of polarizing films in recent years, it is preferably 4.0 m or more, more preferably 5.0 to 7.0 m.

[0076] It should be noted that even for a core tube for taking up a PVA-based film roll made of a metal such as aluminum as shown in Patent Document 1 proposed in the past, when the axial length is short, the degree of defects such as winding sag of the PVA-based film roll is small, but when the axial length becomes long, bending significantly appears, so it is difficult to cope with the widening and lengthening of polarizing films in recent years. If it is the core tube (1) for taking up the film roll, even when using a metal such as aluminum that is advantageous from the viewpoints of manufacturing cost and manufacturing preparation time as the material, defects such as winding sag of the PVA-based film roll can be suppressed, so it is possible to effectively cope with the widening and lengthening of polarizing films in recent years. Therefore, as an example of particularly demonstrating the effects of the present invention, there is an embodiment in which the axial length of the core tube (1) for taking up the film roll is 4.5 m or more (especially 5.0 m or more) and the material is made of a metal such as aluminum (especially aluminum alloy).

[0077] The diameter (outer diameter) of the core tube (1) for taking up the film roll is usually 75 to 350 mm. It is preferably 110 to 320 mm, more preferably 200 to 300 mm. In addition, the wall thickness of the core tube (1) for taking up the film roll also depends on its material, and when its material is aluminum alloy, it is usually 5 to 40 mm.

[0078] The mass of the core tube (1) for taking up the film roll is usually 10 to 200 kg. It is preferably 20 to 200 kg, more preferably 30 to 200 kg. Further preferably 30 to 180 kg, particularly preferably 30 to 150 kg.

[0079] From the viewpoint of suppressing rotational vibration during winding, the core tube (1) for this film winding preferably has a roundness of 0.01 to 1 mm and a cylindricity of 0.01 to 1 mm. More preferably, the roundness is 0.01 to 0.2 mm and the cylindricity is 0.01 to 0.2 mm, and particularly preferably, the roundness is 0.01 to 0.1 mm and the cylindricity is 0.01 to 0.1 mm. It should be noted that the above-mentioned roundness is the value measured according to JIS H 0500 (1998) and is the difference between the maximum outer diameter and the minimum outer diameter measured in any cross-section of the core tube. In addition, the above-mentioned cylindricity is the value measured according to JIS B0182 (1993) and is the difference between the minimum cylindrical diameter and the maximum cylindrical diameter.

[0080] [Film]

[0081] Regarding the material of the film (2), there is no particular limitation, and examples thereof include: polyvinyl alcohol-based resins, cellulose-based resins, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, etc. The film (2) has these materials as the main components and is formed, for example, by a known film-forming method using a solution of these resins as the forming material.

[0082] Among the above, a polyvinyl alcohol-based resin is ideal for the material of the film (2), and a PVA-based film is ideal for the film (2).

[0083] Taking the PVA-based film as an example, the film (2) will be described.

[0084] The PVA-based film is manufactured by forming a long strip by a continuous casting method using an aqueous solution of a polyvinyl alcohol-based resin and then cutting and removing (trimming) both end portions to make the width the designed value.

[0085] Regarding the polyvinyl alcohol-based resin (hereinafter, sometimes referred to as "PVA-based resin"), an unmodified PVA-based resin is usually used, that is, a resin obtained by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate. A resin obtained by saponifying a copolymer of vinyl acetate and a small amount (for example, 10 mol% or less, more preferably 5 mol% or less) of a component copolymerizable with vinyl acetate may also be used as needed. Examples of the component copolymerizable with vinyl acetate include: unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (ethylene, propylene, n-butene, isobutene, etc.), vinyl ethers, unsaturated sulfonates, etc.

[0086] In addition, a PVA-based resin having a 1,2-diol bond in the side chain can also be used as the PVA-based resin. The PVA-based resin having a 1,2-diol bond in the side chain can be prepared by, for example, the following methods: (i) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene; (ii) a method of saponifying and decarboxylating a copolymer of vinyl acetate and ethylene carbonate; (iii) a method of saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane; (iv) a method of saponifying a copolymer of vinyl acetate and glycerol monoallyl ether, etc.

[0087] The weight-average molecular weight of the PVA-based resin is preferably from 100,000 to 300,000, more preferably from 110,000 to 280,000, and still more preferably from 120,000 to 260,000. When the weight-average molecular weight is too small, there is a tendency that sufficient optical properties cannot be obtained when the PVA-based resin is made into an optical film, while when it is too large, there is a tendency that it is difficult to stretch and difficult to industrially produce when the film is made into a polarizing film. In addition, the weight-average molecular weight of the PVA-based resin is measured by the GPC-MALS method.

[0088] From the viewpoint of the optical properties of the above polarizing film, the average saponification degree of the above PVA-based resin is generally preferably 98 mol% or more, particularly preferably 99 mol% or more, still more preferably 99.5 mol% or more, and especially preferably 99.8 mol% or more. That is, when the average saponification degree is too small, the above polarizing film made of a PVA-based resin film tends to not have sufficient optical properties.

[0089] The PVA-based resin aqueous solution preferably contains generally used plasticizers such as glycerol, diglycerol, triglycerol, ethylene glycol, triethylene glycol, polyethylene glycol, trimethylolpropane, etc. The content is preferably 30 parts by mass or less relative to 100 parts by mass of the PVA-based resin, particularly preferably 3 to 25 parts by mass, and still more preferably 5 to 20 parts by mass. When there is too much plasticizer, a tendency of reduced film strength can be seen.

[0090] In addition, the PVA-based resin aqueous solution preferably further contains nonionic, anionic, and cationic surfactants, and among them, nonionic surfactants such as polyoxyethylene dodecylamine are particularly preferred. The content of the surfactant is preferably 5 parts by mass or less relative to 100 parts by mass of the PVA-based resin, still more preferably 0.001 to 3 parts by mass, and particularly preferably 0.001 to 2 parts by mass. When there is too much surfactant, there is a tendency that the appearance of the film surface becomes poor.

[0091] Sodium acetate contained in the powder of the PVA-based resin has an adverse effect on the optical properties, and therefore it is preferably removed (deacetylated). The removal (deacetylation) of the sodium acetate is usually carried out by adding water to the polyvinyl alcohol-based resin in a deacetylation tank.

[0092] Next, the washed water-containing PVA-based resin wet cake is dissolved and a PVA-based resin aqueous solution is prepared. However, when the water-containing PVA-based resin wet cake is directly dissolved in water, a desired high-concentration aqueous solution cannot be obtained. Therefore, dehydration is preferably performed first. The dehydration method is not particularly limited, but generally a method using centrifugal force is employed.

[0093] Preferably, the water-containing PVA-based resin wet cake having a water content of 50% by mass or less, more preferably 30 to 45% by mass, is prepared through the above washing and dehydration. When the water content is too high, there is a tendency that it is difficult to achieve the desired aqueous solution concentration.

[0094] Next, in a dissolution tank, steam (about 110 to 160 °C) is blown into the cake-shaped PVA-based resin to pressurize and dissolve it to prepare a PVA-based resin aqueous solution. At this time, a plasticizer, an additive, etc. may be added as needed. Thus, a PVA-based resin aqueous solution having a water content of about 60 to 80% by mass is prepared.

[0095] Next, after the prepared PVA-based resin aqueous solution is filtered with a filter to remove impurities, a defoaming treatment is performed. Regarding the defoaming treatment method, a standing defoaming, a defoaming treatment method using a multi-screw extruder, etc. are used, but a defoaming treatment method using a multi-screw extruder is preferably used.

[0096] Next, after the defoamed PVA-based resin aqueous solution is filtered again with a filter, it is supplied to a T-shaped slit die and extruded from the T-shaped slit die to flow down in a curtain shape.

[0097] Next, the PVA-based resin aqueous solution flowing down after being extruded from the T-shaped slit die is cast, formed into a film, dried, and formed into a film on the outer peripheral surface of a rotating drum-shaped roller. In addition, for film formation and drying, the drum-shaped roller is usually at a high temperature (about 80 to 100 °C) itself.

[0098] Next, the film is peeled off from the outer peripheral surface of the drum-shaped roller and passed between a plurality of drying rollers (about 60 to 100 °C) in such a manner that the front and back surfaces of the film alternately pass through, and then preferably heat treatment is performed with a heat treatment machine (about 100 to 140 °C). Next, humidity adjustment may be performed with a humidity adjuster as needed.

[0099] The water content of the film is preferably 5% by mass or less, particularly preferably 1 to 4% by mass. When the water content is too high, there is a tendency that the appearance is likely to be poor during film storage.

[0100] (Width, length, and thickness of the film)

[0101] The width, length, and thickness of the film (2) are not particularly limited and can be appropriately set.

[0102] The width of the film (2) is not particularly limited, but is preferably, for example, 3.0 m or more, more preferably 4.0 m or more, and particularly preferably 4.5 m or more. The upper limit is not particularly limited, but is, for example, 7.0 m. Although not particularly limited, from the perspective of, for example, the widening of polarizing films in recent years, the width of the film (2) is preferably set within the above range.

[0103] In addition, the length of the film (2) is not particularly limited, but is preferably, for example, 5000 m or more, more preferably 8000 m or more, and particularly preferably 10000 m or more. The upper limit is not particularly limited, but may be, for example, 30000 m. Although not particularly limited, from the viewpoint of, for example, the elongation of polarizing films in recent years, the length of the film (2) is preferably set within the above range.

[0104] The thickness of the film (2) is not particularly limited, but is, for example, 70 μm or less, preferably 65 μm or less. The lower limit of the thickness is usually about 15 μm.

[0105] [Method for manufacturing film roll]

[0106] As the method for producing the film roll, a known method can be used as appropriate. An example of the method for producing the film roll is described below. The following production method is not particularly limited, but is ideal as a method for producing a PVA-based film roll.

[0107] First, the core tube (1) for winding the film is supported in a manner that allows it to rotate freely relative to a known film winding device. Next, the leading edge of the film (2) continuously formed into a long strip is fixed to the outer peripheral surface of the core tube (1) for winding the film using a fixing tape. Next, the core tube (1) for winding the film is rotated to wind the film (2) onto the core tube (1) for winding the film, thereby obtaining Figure 1 The film roll shown.

[0108] Although the reference Figure 2 , 3 An example of a production method including a step of winding a film (2) using the film winding core tube (1) is specifically described, but the present invention is not limited to this embodiment.

[0109] Figure 2 , 3 The winding device shown is a device for winding the manufactured long film (2) onto the core tube (1) for winding the film after cutting it into a designed width.

[0110] like Figure 2As shown, the winding device has: a core tube support (10) that supports the core tube (1) for winding the present film in a freely rotatable manner; and a pair of control rollers (11, 12) arranged in parallel with the core tube (1) for winding the present film. In addition, the core tube support (10) has a driving device (not shown), such as a motor, for driving the rotation of the core tube (1) for winding the present film.

[0111] The winding device manufactures by winding the film (2) after the cutting process onto the core tube (1) for winding the present film while bringing it into contact with at least one of the pair of control rollers (11, 12). Figure 1 the film roll shown.

[0112] It should be noted that, in Figure 2 、 3 the symbol (5) is a plurality of guide rollers provided to move the formed long film (2) in the length direction to the winding device.

[0113] The arm-shaped core tube support (10) has the core tube (1) for winding the present film detachably attached to its front end portion, and freely swings around the root portion of its arm along a virtual plane perpendicular to the axis of the core tube (1) for winding the present film (refer to the arrow R in Figure 2 ). The swing radius of the arm-shaped core tube support (10) is larger than the radius of the manufactured film roll, usually 1.0 to 1.5 m.

[0114] The pair of control rollers (11, 12) has a first control roller (11) and a second control roller (12). Each control roller (11, 12) is rotatably mounted on the front end portion of a swing arm (11a, 12a) in a freely following manner, and is arranged in a mutually opposed state (configured in a tandem type). Each swing arm (11a, 12a) freely swings around the root portion along a virtual plane perpendicular to the axis of each control roller (11, 12). The pair of control rollers (11, 12) can be independently adjusted in position.

[0115] The dimensions of each control roller (11, 12) are not particularly limited, but usually have a radius of 100 to 300 mm and a length greater than or equal to the width of the film (2). The center-to-center distance between the opposed control rollers (11, 12) is usually 150 to 700 mm. The swing radius of the swing arms (11a, 12a) is larger than the radius of the control rollers (11, 12), usually 200 to 1000 mm.

[0116] Regarding the method of winding the film (2) using the core tube (1) for winding the present film, for example, as Figure 2As shown, after installing and supporting the film take-up core tube (1) at the front end of the core tube support (10), when the film take-up core tube (1) is rotated, the film (2) starts to be wound around the outer peripheral surface of the film take-up core tube (1).

[0117] It should be noted that from the start of winding to a predetermined point (initial winding period), as Figure 2 shown, the film (2) contacts the second control roller (12) and then the first control roller (11), and then is wound onto the outer peripheral surface of the film take-up core tube (1). During this winding period, as the outer diameter of the film (2) wound onto the film take-up core tube (1) increases, the core tube support (10) swings (refer to the arrow R in Figure 2 ) and the film take-up core tube (1) moves away from the first control roller (11).

[0118] When continuing such winding, for example, as Figure 3 shown, after contacting the second control roller (12) from a predetermined point, it is wound without contacting the first control roller (11). The entry angle (the angle β between the line segment L and the film (2)) during this winding usually becomes larger than the above-mentioned entry angle (the angle α between the line segment L and the film (2)) in the initial winding period. Continuing such winding, a film roll is produced.

[0119] There is no particular limitation on the winding speed of the film (2), but it is preferably 35 m / min or more, particularly preferably 40 m / min or more, and further preferably 50 to 150 m / min.

[0120] When the winding speed is too slow, there is a tendency for the production efficiency to decrease, and when it is too fast, the uniformity of the cut end surface deteriorates, and there is a tendency to have an adverse effect on the performance of, for example, a polarizing film.

[0121] In addition, during the winding period, the gap (approach amount) between the outer peripheral surface of the wound film (2) and the outer peripheral surface of the first control roller (11) is preferably maintained at 2 to 10 mm, particularly preferably 2 to 8 mm, and further preferably 2 to 6 mm. In particular, the gap (approach amount) is preferably maintained in the range of 2 to 5 mm in the initial winding period and 3 to 8 mm after the initial winding period.

[0122] When the gap (approach amount) is too large, the release state of the film (2) is uneven, and there is a tendency for, for example, the produced polarizing film to easily generate color spots and the performance to deteriorate. When the gap (approach amount) is too small, there is a tendency for the film (2) to easily generate wrinkles during winding.

[0123] The winding tension of the film (2) is not particularly limited, but is preferably, for example, 100 to 350 N / m, particularly preferably 120 to 320 N / m, and further preferably 140 to 300 N / m. When the winding tension is too large, wrinkles due to tight winding tend to occur. When the winding tension is too small, winding sag tends to occur, and the film roll tends to be eccentric.

[0124] The winding tension is the tension applied to each 1m width of the winding film (2). The winding tension can be adjusted by, for example, adjusting the torque of the core tube (1) for winding the film and adjusting the load on the film (2) by using a tension roller provided in the path of the film (2).

[0125] The cut end surface of the film roll produced by using the core tube (1) for film winding is uniform, the winding droop is also suppressed, and the eccentricity of the film roll is small, so the unwinding state of the film (2) can be uniform. Therefore, for example, when a polarizing film is produced by using a PVA film roll produced by using the core tube (1) for film winding, the polarizing film can be made into a film with excellent performance such as no color spots.

[0126] In addition, when the film roll has a large winding sag and a large eccentricity, the film roll may come into contact with the first control roller (also called a near contact roller) adjacent to the film roll during the winding process, and when the film roll comes into contact with the first control roller, the winding device may stop. Therefore, it is necessary to frequently monitor to avoid contact between the two, which is a heavy burden. On the other hand, when the distance between the film roll and the first control roller is increased to avoid contact between the film roll and the first control roller, the amount of air drawn into the film roll increases, which promotes defects such as winding sag.

[0127] If a film roll is made using the core tube (1) for film winding, the winding sag and the eccentricity of the film roll can be suppressed. Therefore, for example, in the winding process, the possibility of contact between the film roll and the first control roller can be reduced, which is also useful in reducing the possibility of the winding device stopping. In addition, the need to increase the distance between the film roll and the first control roller to avoid contact between the film roll and the first control roller is also small, so it is also useful in reducing the amount of air entrainment.

[0128] [Polarizing film]

[0129] Next, a method for producing a polarizing film as an example of a product produced using the above-mentioned film roll will be described.

[0130] In the manufacture of polarizing film, the PVA film is usually moved in the longitudinal direction while undergoing the processes of swelling, dyeing, boric acid cross-linking, stretching, washing, and drying. First, a PVA film roll is set in a polarizing film manufacturing device. Then, the PVA film is unwound from the PVA film roll. Then, the PVA film is dyed, uniaxially stretched, and treated with a boron compound.

[0131] The above-mentioned dyeing is carried out by bringing the PVA-based film into contact with a liquid containing iodine or a dichroic dye. An aqueous solution of iodine-potassium iodide is usually used, preferably with an iodine concentration of 0.1 to 20 g / L, a potassium iodide concentration of 10 to 70 g / L, and a mixing mass ratio of potassium iodide / iodine in the range of potassium iodide / iodine = 10 to 100. In addition, a dyeing time of about 30 to 500 seconds is practical, and the temperature of the dyeing treatment bath is preferably 5 to 60 °C. In addition, a small amount of an organic solvent compatible with water may also be contained in addition to the water solvent. In addition, as the contacting means, any means such as dipping, coating, and spraying can be used.

[0132] The above-mentioned uniaxial stretching is preferably stretched to 3 to 10 times, and more preferably 3.5 to 6 times. At this time, a little stretching can also be carried out in a direction perpendicular to the above-mentioned uniaxial stretching (stretching to prevent shrinkage in the width direction or more). The temperature condition during uniaxial stretching is preferably set in the range of 40 to 170 °C. In addition, the uniaxial stretching ratio is finally set within the above range, and the uniaxial stretching can be carried out not only in one stage but also in any stage of the manufacturing process.

[0133] It should be noted that the above-mentioned dyeing can be carried out before uniaxial stretching, simultaneously with uniaxial stretching, or after uniaxial stretching. However, since the crystallization of the PVA-based film progresses and the dyeability decreases through uniaxial stretching, the above-mentioned dyeing is preferably carried out before or simultaneously with uniaxial stretching.

[0134] The above-mentioned boron compound treatment is a treatment for making the dyeing firm and is carried out after dyeing and uniaxial stretching, simultaneously with dyeing, or simultaneously with uniaxial stretching. Regarding the boron compound, boric acid and borax are practical. This boron compound is preferably made into an aqueous solution or a water-organic solvent mixture and used at a concentration of about 0.3 to 2 mol / L, and a small amount of potassium iodide is coexisted in the liquid. Regarding the treatment method using the boron compound, the dipping method is preferred, but the coating method and the spraying method can also be implemented. In addition, regarding the treatment conditions, the temperature is about 40 to 70 °C, the treatment time is preferably about 2 to 20 minutes, and it is also preferred to carry out a stretching operation during the treatment as needed.

[0135] When the polarizing film thus obtained is released in a state where the PVA-based film as the polarizing film material is homogeneous, it becomes one having excellent polarization performance and appearance characteristics.

[0136] The polarizing film can also be used as a polarizing plate by laminating and bonding an optically isotropic polymer film or sheet on one or both of its sides as a protective film. Examples of the protective film include films or sheets of cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, poly-4-methylpentene, polyphenylene ether, cyclic or norbornene-based polyolefins, etc. In addition, for the purpose of thinning, the polarizing film can be coated and laminated with a curable resin such as a urethane-based resin, an acrylic-based resin, or a urea-based resin on one or both of its sides instead of the protective film.

[0137] In addition, the polarizing film (or one having a protective film or a curable resin laminated on at least one of its sides) may sometimes be provided with a transparent pressure-sensitive adhesive layer formed on one of its surfaces by a general method as needed for practical use. As for the pressure-sensitive adhesive layer, a copolymer of an acrylate such as butyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, etc. and an α-monoolefin carboxylic acid such as acrylic acid, maleic acid, itaconic acid, methacrylic acid, crotonic acid, etc. (including those containing vinyl monomers such as acrylonitrile, vinyl acetate, and styrene added) as the main component does not impair the polarization performance of the polarizing film, and is therefore particularly preferred. In addition to this, as long as it is a pressure-sensitive adhesive having transparency, it can be used, and for example, a polyvinyl ether-based or rubber-based one can also be used.

[0138] The polarizing film and the polarizing plate are preferably used for liquid crystal display devices such as portable information terminals, personal computers, televisions, projectors, signs, electronic desk calculators, electronic clocks, word processors, electronic papers, game machines, video recorders, cameras, photo albums, thermometers, audio equipment, automobiles, mechanical measuring instruments, etc., sunglasses, anti-glare glasses, 3D glasses, wearable displays, reflection reduction layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical communication equipment, medical equipment, building materials, toys, etc.

[0139] Examples

[0140] Hereinafter, examples and comparative examples will be listed to more specifically illustrate the present invention, but the present invention is not limited to the following examples as long as it does not exceed the gist of the present invention. In addition, "parts" and "%" in the examples refer to mass basis.

[0141] <Comparative Example 1>

[0142] Prepare a cylindrical film take-up core tube (1-1) obtained by extrusion molding of aluminum alloy (A6061-T6). The dimensions of the film take-up core tube (1-1) are: axial length 6200 mm, inner diameter 280 mm, outer diameter 300 mm, and mass 150 kg. Use Figure 5The dynamic balance measuring machine shown measures the dynamic balance of the core tube (1-1) for taking up the film roll according to JIS B 0905 (1992). As a result, the right side is 1550 g and the left side is 1510 g.

[0143] The PVA-based film to be wound onto the core tube (1-1) for taking up the film roll is produced as described below and wound onto the core tube (1-1) (continuous casting method) to form a PVA-based film roll.

[0144] That is, 1000 kg of a PVA-based resin with a weight-average molecular weight of 142000 and a saponification degree of 99.8 mol%, 2500 kg of water, and 100 kg of glycerol as a plasticizer are placed in a dissolution tank, heated to 140°C while stirring, and the concentration is adjusted to a resin concentration of 25% by mass to obtain a uniformly dissolved aqueous solution of a polyvinyl alcohol-based resin. Next, this aqueous solution of the polyvinyl alcohol-based resin is supplied to a twin-screw extruder and degassed, and then the temperature of the aqueous solution is raised to 95°C. It is sprayed and cast from the T-shaped slit die nozzle onto a casting drum with a surface temperature of 90°C to form a film. Then, the formed film is dried with multiple metal heating rollers, heat-treated using a floating dryer, and then the two side ends are cut off and wound onto the core tube (1-1) for taking up the film roll to obtain a PVA-based film roll with a wound thickness of 60 μm, a width of 5010 mm, and a length of 129000 mm. The winding speed is 100 m / min, and the winding tension is 288 N / m.

[0145] <Example 1>

[0146] The dynamic balance of the core tube (1-1) for taking up the film roll is corrected using a lead balance weight to obtain the core tube (1-2) for taking up the film roll. The dynamic balance of the core tube (1-2) for taking up the film roll is measured according to JIS B 0905 (1992) in the same manner as above. As a result, the right side is 126 g and the left side is 270 g.

[0147] Except for using the core tube (1-2) for taking up the film roll, a PVA-based film roll is produced in the same manner as Comparative Example 1.

[0148] The appearance of each of the obtained PVA-based film rolls is observed, and the uniformity of the cut end face and the winding sag are evaluated. The results are shown in Table 1.

[0149] [Table 1]

[0150]

[0151] From the results in Table 1, it can be seen that the cut end face of Comparative Example 1 where the dynamic balance of the core tube for taking up the PVA-based film roll exceeds 1450 g is uneven. Specifically, the axial deviation of the inner part adjacent to the core tube in the PVA-based film is relatively small, but the axial deviation of the outer part is large. In addition, it was confirmed that Comparative Example 1 had a winding sag (T2 - T1) of 31 mm.

[0152] On the other hand, in Example 1 where the dynamic balance of the core tube for winding the PVA-based film is confirmed to be below 1450 g, there is no axial deviation like that in Comparative Example 1 and the cut end faces are uniform. In addition, it is confirmed that the magnitude of the winding sag (T2 - T1) in Example 1 is approximately halved compared to Comparative Example 1.

[0153] The specific modes in the present invention are shown in the above embodiments, but the above embodiments are merely illustrative and not to be construed in a limiting sense. It is intended to include various modifications obvious to those skilled in the art within the scope of the present invention.

[0154] Industrial Applicability

[0155] The cut end faces of the film roll made using the core tube for winding the film of the present invention are uniform and the winding sag is suppressed. Therefore, for example, the PVA-based film roll made using the core tube for winding the PVA-based film of the present invention can be effectively used in the case of manufacturing a polarizing film with excellent optical properties.

[0156] Description of Reference Numerals

[0157] 1: Core tube for winding the film

[0158] 2: Film

[0159] S: Cut end face

Claims

1. A core tube for taking a film roll, wherein, The core tube for taking the film roll is a metal core tube with a dynamic balance of less than 1450 g.

2. The core tube for taking a film roll according to claim 1, wherein, The film is a polyvinyl alcohol-based film.

3. The core tube for taking up the film roll according to claim 1 or 2, wherein, The metal is aluminum alloy.

4. The core tube for taking up the film roll according to claim 1 or 2, wherein, The axial length of the core tube for taking the film roll is 0.5 to 7.0 m.

5. The core tube for taking up the film roll according to claim 1 or 2, wherein, The outer diameter of the core tube for taking the film roll is 75 to 350 mm.

6. The core tube for taking up a film roll according to claim 1 or 2, wherein, The mass of the core tube for taking the film roll is 30 to 200 kg.

7. The core tube for taking up the film roll according to claim 1 or 2, wherein, The film is a polyvinyl alcohol-based film for manufacturing a polarizing film.

8. The core tube for taking up a film roll according to claim 1 or 2, wherein, The dynamic balance is less than 1200 g.

9. A polyvinyl alcohol-based film roll, comprising the core tube for taking the film roll according to claim 1 or 2 and the polyvinyl alcohol-based film wound around the core tube.

10. A method for manufacturing a polyvinyl alcohol-based film roll, comprising the step of using the core tube for taking the film roll according to claim 1 or 2 to wind the polyvinyl alcohol-based film.

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