JP5888031B2 - Optical film roll and method for producing optical film roll - Google Patents

Description

  The present invention relates to an optical film roll and a method for producing an optical film roll.

  The liquid crystal display device is provided with an optical film such as a retardation film or a polarizing plate protective film. These optical films may be formed into a multilayer film bonded with a protective film for the purpose of preventing scratches on the film surface and assisting in handling during storage and transportation, for example. Moreover, it is common that the multilayer film which bonded the optical film and the protective film is shipped in the state of the optical film roll wound by roll shape.

  With the recent increase in size, thickness, contrast, and price of liquid crystal display devices, optical films are becoming wider, thinner, and defect levels are being lowered. Furthermore, along with this, in the optical film roll wound with the multilayer film in which the optical film and the protective film are bonded together, there is a problem of maintaining a good winding shape without generation of wrinkles and deterioration of the gauge band. It has become. Here, the “gauge band” refers to unevenness in the width direction that extends on the surface of the optical film roll and extends in the circumferential direction. The rolled form of the optical film roll refers to the appearance of the optical film roll. It is preferable to keep the winding state of the optical film roll well not only in the optical film roll obtained by winding the multilayer film but also in the optical film roll in the middle of winding the multilayer film.

It has been found that the amount of air entrained when the multilayer film is wound is involved in the winding shape of the optical film roll. Therefore, when winding a multilayer film at a high speed, using a winding device including a winding roll and a contact pressure roller, a method of winding while applying a surface pressure to the multilayer film by pressing with the contact pressure roller (Hereinafter sometimes referred to as “touch winding method” as appropriate) is generally adopted. According to this method, when a thin multilayer film is wound at a high speed, the amount of air entrained can be easily suppressed.
Regarding the touch winding method, techniques such as Patent Documents 1 to 3 have been proposed from the viewpoint of improving the winding shape of the optical film roll.

JP 05-310346 A Japanese Patent Laid-Open No. 11-059985 JP 2011-112945 A

  Some optical films are smooth and have low slipperiness. Some optical films have a low elastic modulus. A multilayer film provided with such an optical film is likely to be deformed. Moreover, generally, the multilayer film provided with the optical film with a wide width | variety and a thin film thickness tends to produce a wave | undulation during conveyance. Therefore, it is difficult to control the amount of air entrained during the winding even by the touch winding method. Examples of such an optical film include an optical film containing an alicyclic structure-containing polymer such as a norbornene-based resin film. Therefore, in an optical film including an alicyclic structure-containing polymer, it is difficult to stably prevent wrinkles and gauge bands with the conventional technology, and it is difficult to maintain a good winding shape of the optical film roll. It was.

  If such wrinkles or gauge bands are generated, the shape of the optical film may be deformed, resulting in an optical defect. Further, in actual commercial transactions, even if there is no loss in performance, the product value may be evaluated low because the winding shape is not good. For this reason, in the optical film roll provided with the optical film containing an alicyclic structure containing polymer, the technique which suppresses a wrinkle and a gauge band and keeps a winding form favorable is calculated | required.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical film roll having a good winding shape.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has obtained an optical film roll in which a multilayer film obtained by laminating an optical film containing an alicyclic structure-containing polymer and a protective film is wound, Arithmetic average roughness Ra of the surface opposite to the optical film falls within a predetermined range, and further, the average film thickness h in the width direction of the optical film, the film thickness h _c in the center in the width direction, and the films at both ends in the width direction When the thicknesses h _e1 and h _e2 , the film thickness h _{w at} an arbitrary width position w, and the average film thickness h _{w ± 200} in the width direction in the range of the width position w ± 200 mm satisfy a predetermined relationship, an optical film roll The present invention has been completed by finding that the winding shape of can be improved.
That is, the present invention is as follows [1] to [5].

[1] An optical film roll formed by winding an optical film containing an alicyclic structure-containing polymer and a multilayer film obtained by laminating a protective film peelable from the optical film into a roll,
The arithmetic average roughness Ra of the surface of the protective film opposite to the optical film is 0.2 μm or more and 1.4 μm or less,
The optical film has an average film thickness in the width direction of h, a film thickness in the center of the width direction of h _c , a film thickness at both ends in the width direction of h _e1 and h _e2 , and a film thickness at an arbitrary width position w. H _w (where w represents the distance from the end on either side in the width direction of the optical film, and w> 200 mm), the average of the width direction in the range of width position w ± 200 mm An optical film roll that satisfies the relationships of the following formulas (1) to (3) when the film thickness is _{hw ± 200} .
0.5 ≦ (h _c −h _e1 ) /h×100≦3.0 (1)
0.5 ≦ (h _c −h _e2 ) /h×100≦3.0 (2)
_{(H w -h w ± 200)} /h×100≦2.0 (3)
[2] The optical film roll according to [1], wherein the multilayer film has a width of 1,500 mm or more.
[3] The optical film roll according to [1] or [2], wherein the arithmetic average roughness Ra of the surface of the optical film opposite to the protective film is 0.001 μm or more and 0.05 μm or less.
[4] A step of obtaining an optical film by melt-extruding a resin containing an alicyclic structure-containing polymer,
A method for producing an optical film roll, comprising: a step of bonding a protective film peelable from the optical film to the optical film to obtain a multilayer film; and a step of winding the multilayer film into a roll.
The arithmetic average roughness Ra of the surface of the protective film opposite to the optical film is 0.2 μm or more and 1.4 μm or less,
The optical film has an average film thickness in the width direction of h, a film thickness in the center of the width direction of h _c , a film thickness at both ends in the width direction of h _e1 and h _e2 , and a film thickness at an arbitrary width position w. H _w (where w represents the distance from the end on either side in the width direction of the optical film, and w> 200 mm), the average of the width direction in the range of width position w ± 200 mm The manufacturing method of an optical film roll which satisfy | fills the relationship of following formula (1)-(3), when a film thickness is _{hw +/- 200} .
0.5 ≦ (h _c −h _e1 ) /h×100≦3.0 (1)
0.5 ≦ (h _c −h _e2 ) /h×100≦3.0 (2)
_{(H w -h w ± 200)} /h×100≦2.0 (3)
[5] In the winding step, a winding device including a winding roll and a contact pressure roller is used, and the surface of the multi-layer film is applied to the winding roll while being pressed by the contact pressure roller. Winding up the multilayer film,
When the arithmetic average roughness of the surface of the protective film opposite to the optical film is Ra (μm), the pressure P (N / m) of the contact pressure roller satisfies the following formula (4): 4].
50 × Ra + 75 ≦ P ≦ 23 × Ra + 160 (4)

  ADVANTAGE OF THE INVENTION According to this invention, an optical film roll with a favorable winding form and its manufacturing method can be provided.

FIG. 1 is a diagram schematically showing an optical film roll according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a cross section of a multilayer film according to an embodiment of the present invention. FIG. 3 is a perspective view schematically showing an optical film according to an embodiment of the present invention. FIG. 4 is a diagram schematically showing how an optical film roll is obtained by winding a multilayer film. FIG. 5 is a diagram for explaining a film thickness measurement method in Examples and Comparative Examples. FIG. 6 is a diagram schematically illustrating an optical film roll manufacturing apparatus according to the first embodiment.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and may be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and the equivalents thereof.

[1. Overview]
FIG. 1 is a diagram schematically showing an optical film roll according to an embodiment of the present invention. Moreover, FIG. 2 is a figure which shows typically the cross section of the multilayer film which concerns on one Embodiment of this invention.
As shown in FIG. 1, the optical film roll 100 is a roll formed by winding a multilayer film 10 into a roll shape. The multilayer film 10 is a film in which an optical film 20 containing an alicyclic structure-containing polymer and a protective film 30 that can be peeled off from the optical film 20 are bonded together.

  The optical film roll 100 includes a step of forming a resin containing an alicyclic structure-containing polymer to obtain the optical film 20, and a protective film 30 that can be peeled off from the optical film 20 is bonded to the optical film 20 to form a multilayer film. 10 and a step of winding the multilayer film 10 in a roll shape.

In general, when a film roll is manufactured by winding a film, the amount of air that is wound is related to the generation of wrinkles and gauge bands during and after the winding of the film.
For example, the generation of wrinkles is one of the causes of excessive air entrainment during winding. When the film is wound, if there is a lot of air, the film is easily deformed by the air layer formed between the stacked films, so that wrinkles are likely to occur.
In addition, for example, the generation of a gauge band is one of the reasons that air is not sufficient when it is wound. Usually, the film thickness in the width direction is not necessarily constant, and is non-uniform. Such a film absorbs the non-uniformity of the film thickness in the width direction by preventing air from being generated by entraining air to some extent when the film is wound. However, if the amount of air involved is insufficient, the thickness of the air layer between the overlaid films becomes thin, and the nonuniformity of the film thickness in the width direction cannot be absorbed, and a gauge band may be generated.

  On the other hand, since the optical film roll 100 of the present embodiment has a configuration capable of appropriately controlling the amount of air entrained, the generation of wrinkles and gauge bands is suppressed, and a good winding shape is realized. Is possible.

[2. Step of obtaining optical film]
In the manufacturing method of the optical film roll 100, first, an optical film 20 is manufactured by molding a resin containing an alicyclic structure-containing polymer. Usually, since a film containing an alicyclic structure-containing polymer has low slipperiness, there is a tendency that stress concentration easily occurs when the film is laminated with another film and when the film is wound. Moreover, since the film containing an alicyclic structure containing polymer has a low elastic modulus, it is difficult to relieve stress. For this reason, the optical film 20 tends to be easily deformed. However, in the optical film roll 100 according to the present embodiment, even with the optical film 20 that is likely to be deformed and the like as described above, generation of wrinkles and gauge bands can be suppressed, so that a good winding shape can be realized.

  The alicyclic structure-containing polymer is a polymer having an alicyclic structure in one or both of the main chain and the side chain. Among these, a polymer containing an alicyclic structure in the main chain is preferable from the viewpoint of mechanical strength, heat resistance, and the like.

  Examples of the alicyclic structure include a saturated cyclic hydrocarbon (cycloalkane) structure and an unsaturated cyclic hydrocarbon (cycloalkene, cycloalkyne) structure. Among these, from the viewpoint of mechanical strength and heat resistance, a cycloalkane structure and a cycloalkene structure are preferable, and a cycloalkane structure is particularly preferable.

  The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, particularly preferably per alicyclic structure. Is in a range of 15 or less, the mechanical strength, heat resistance and moldability are highly balanced, which is preferable.

  The ratio of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer may be appropriately selected according to the use of the optical film 20, and is usually 50% by weight or more, preferably 70% by weight or more, and more. Preferably it is 90 weight% or more. The heat resistance of the optical film 20 can be improved by setting the ratio of the repeating unit having an alicyclic structure to be equal to or higher than the lower limit of the above range. Here, a repeating unit other than the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer is appropriately selected according to the purpose of use of the optical film 20.

Specific examples of the alicyclic structure-containing polymer include (1) a ring-opening polymer of a monomer having a norbornene ring structure (hereinafter referred to as “norbornene monomer”), a norbornene monomer, and this. Ring-opening copolymers of benzene with other ring-opening copolymerizable monomers, as well as hydrogenated products, addition polymers of norbornene monomers, and other copolymerizable with norbornene monomers Norbornene polymers such as addition copolymers with monomers of (2); polymers of monocyclic olefins and hydrogenated products thereof; (3) polymers of cyclic conjugated dienes and hydrogenated products thereof; 4) Polymers of vinyl alicyclic hydrocarbon monomers, copolymers of vinyl alicyclic hydrocarbon monomers with other monomers copolymerizable therewith, and hydrogenated products thereof, vinyl Aromatic hydrogenated products of aromatic monomer polymers and Alkenyl aromatic monomer and copolymerizable therewith vinyl alicyclic hydrocarbon polymers, such as other copolymer aromatic ring hydrogenated products of the monomers; and the like. Among these, from the viewpoint of heat resistance and mechanical strength, norbornene-based polymers and vinyl alicyclic hydrocarbon-based polymers are preferable, norbornene-based ring-opening polymer hydrogenated products, norbornene-based single monomers Ring-opening copolymer hydrogenated product of this product with other ring-opening copolymerizable monomers, vinyl aromatic monomer hydrogenated aromatic vinyl monomer and vinyl aromatic monomer More preferred is a hydrogenated aromatic ring of a copolymer of the above and other monomers copolymerizable therewith.
Moreover, an alicyclic structure containing polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Furthermore, the resin containing the alicyclic structure-containing polymer may contain components other than the alicyclic structure-containing polymer as long as the effects of the present invention are not significantly impaired. Examples of components other than the alicyclic structure-containing polymer include antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic agents, dispersants, chlorine scavengers, flame retardants, and crystallization nucleating agents. , Reinforcing agents, antiblocking agents, antifogging agents, mold release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposition agents, metal deactivators, antifouling agents, and antibacterial agents, and fats Known additives such as polymers other than cyclic structure-containing polymers and thermoplastic elastomers may be mentioned. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. However, the amount of components other than the alicyclic structure-containing polymer is within a range that does not impair the effects of the present invention, and is usually 50 parts by weight or less, preferably 30 parts by weight with respect to 100 parts by weight of the alicyclic structure-containing polymer. Or less. The lower limit is zero.

  The optical film 20 is obtained by molding a resin containing the alicyclic structure-containing polymer. There is no restriction | limiting in particular in the shaping | molding method of resin, For example, you may use either a melt molding method or a solution casting method. Examples of the melt molding method include an extrusion molding method in which molding is performed by melt extrusion, a press molding method, an inflation molding method, an injection molding method, a blow molding method, and a stretch molding method. Among these methods, in order to obtain a film excellent in mechanical strength and surface accuracy, an extrusion molding method, an inflation molding method and a press molding method are preferable. Among them, the extrusion molding method is particularly preferable from the viewpoint that the optical film 20 can be produced efficiently and easily while suppressing the development of retardation more reliably.

  Further, after forming a resin to obtain a film, the film may be stretched as necessary to produce a stretched film as the optical film 20.

FIG. 3 is a perspective view schematically showing the optical film 20 according to one embodiment of the present invention. In FIG. 3, the direction X represents the longitudinal direction of the optical film 20, the direction Y represents the width direction of the optical film 20, and the direction Z represents the thickness direction of the optical film 20.
As shown in FIG. 3, the optical film 20 obtained in the present embodiment satisfies the following formulas (1) to (3).
0.5 ≦ (h _c −h _e1 ) /h×100≦3.0 (1)
0.5 ≦ (h _c −h _e2 ) /h×100≦3.0 (2)
_{(H w -h w ± 200)} /h×100≦2.0 (3)

In the above formulas (1) to (3), h represents the average film thickness in the width direction Y of the optical film 20.
In the above formulas (1) to (3), h _c represents the film thickness at the center in the width direction Y of the optical film 20.
In said Formula (1) _-Formula (3), h _e1 and h _e2 represent the film thickness in the both ends of the width direction Y of the optical film 20, respectively.
In the above formulas (1) to (3), _{h w} represents the thickness of the optical film 20 at an arbitrary width position w. Further, w represents the distance from the end on the closer side in the width direction Y of the optical film 20. However, W> 200 mm. Therefore, the width position w is a position in the width direction Y of the optical film 20 and represents a position where the distance from the end on the near side in the width direction Y is w.
In the above formulas (1) to (3), _{hw ± 200} represents the average film thickness in the width direction in the range of the width position w ± 200 mm. Here, the range of the width position W ± 200 mm is a range in the width direction Y of the optical film 20, and the distance from the end on either side in the width direction Y is a range from w−200 mm to w + 200 mm. Represent.

In the film thickness profile in the width direction Y of the optical film 20, the expressions (1) and (2) indicate that the film thickness h _{c at} the center is slightly thicker than the film thicknesses h _e1 and h _e2 at both ends. Represents. That is, the optical film 20 is slightly convex in the width direction Y. At this time, the difference between the film thickness h _{c at} the central portion and the film thicknesses h _e1 and h _{e2 at} both ends is preferably 0.5% or more, more preferably 1.0% as compared with the average film thickness h of the full width. % Or more, preferably 3.0% or less, more preferably 2.0% or less.

In general, when winding a film, air trapped at the time of winding does not easily escape from the central portion in the axial direction of the obtained film roll, so that the film roll is likely to be wrinkled. This tendency is particularly remarkable in a film roll in which a wide film is wound. On the other hand, by setting (h _c −h _e1 ) / h × 100 and (h _c −h _e2 ) / h × 100 to be equal to or higher than the lower limits of the above formulas (1) and (2), the optical film 20 If the central portion in the width direction Y is made thicker than both end portions, the air entrained in the central portion is made difficult to stay and wrinkles can be prevented. However, if the film thickness at the center is too thick compared to both ends, the pressure of the contact roller is excessively concentrated at the center of the multilayer film during winding, and an appropriate amount of air is drawn between the multilayer films. Since it may not be able to be involved, a gauge band may be easily generated. Therefore, upper limits are set in (h _c −h _e1 ) / h × 100 and (h _c −h _e2 ) / h × 100 in the above formulas (1) and (2).

Moreover, Formula (3) means suppressing the fluctuation | variation of the film thickness in the width direction Y of the optical film 20 to some extent or less. In more detail for formula (3), the difference between the average thickness h _{w ± 200} in the range of film thickness h _w and width position w ± 200 mm at any width position w of the optical film 20 has an average thickness of the entire width Compared with h, it is usually 2.0% or less, preferably 1.5% or less, more preferably 1% or less. A film having a film thickness profile with a steep change exceeding this value cannot absorb the steep film thickness change even by air entrained during winding, and there is a possibility that a gauge band is likely to occur.

  Here, in the area | region where the distance from the both ends of the optical film 20 is less than 200 mm, it is not necessary to satisfy | fill Formula (3). If the formula (1) and the formula (2) are satisfied, in the region where the distance from both ends of the optical film 20 is less than 200 mm, the air entrained at the time of winding is well discharged from the end. Moreover, if the formula (1) and the formula (2) are satisfied, in the region where the distance from both end portions of the optical film 20 is less than 200 mm, the pressure by the contact roller becomes weak. For this reason, even if the distance from both ends of the optical film 20 is less than 200 mm, wrinkles and gauge bands are unlikely to occur even if Expression (3) is not satisfied.

There is no restriction | limiting in the means for the optical film 20 to satisfy | fill Formula (1)-Formula (3) as mentioned above. For example, when the optical film 20 is manufactured by melt extrusion, the size (opening width) of the lip gap of the die for extruding the resin may be adjusted appropriately.
For example, the extruded resin temperature is usually + 80 ° C. to + 180 ° C. higher than the glass transition temperature Tg of the resin. The gap of the lip portion can be adjusted by a choke bar and a choke bar adjusting bolt. By rotating the choke bar adjusting bolt clockwise or counterclockwise, the choke bar can narrow or widen the flow path of the molten resin. Further, it is preferable to adjust the temperature of the heat sleeve and finely adjust the gap between the lip portions by utilizing expansion or contraction due to heat of the heat sleeve. The temperature adjustment of the heat sleeve can be performed by known process control, for example, PID control.
In a preferred manufacturing method of the optical film, an average profile of the thickness of the formed film is obtained at a constant time interval (control cycle), and the temperature of the heat sleeve is increased or decreased by PID control in accordance with the average profile. The control period is usually 3 minutes to 30 minutes, preferably 5 minutes to 15 minutes. Each gain value in the PID control is not particularly limited as long as the temperature adjustment of the heat sleeve is stable.

  The optical film 20 is usually a long film. Here, the long length means one having a length of at least about 200 times the width of the film, preferably having a length of 300 times or more, specifically in a roll shape. It has a length that can be wound and stored or transported.

  The average film thickness of the optical film 20 is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less.

As shown in FIG. 2, the arithmetic operation of the surface 20 </ b> U opposite to the surface 20 </ b> D to be bonded to the protective film 30 of the optical film 20 (that is, the surface opposite to the protective film 30 of the optical film 20 in the multilayer film 10). The average roughness Ra is preferably 0.05 μm or less, more preferably 0.03 μm or less, still more preferably 0.01 μm or less, and usually 0.001 μm or more. This makes it possible to achieve both prevention of wrinkles and gauge bands and good optical characteristics. Here, the arithmetic average roughness Ra is an index representing the surface roughness defined in JIS B0601-1994.
The arithmetic average roughness Ra of the surface 20D to be bonded to the protective film 30 of the optical film 20 is usually the arithmetic average roughness Ra of the surface 20U on the opposite side of the surface 20D to be bonded to the protective film 30 of the optical film 20. The same, but may be different.

The optical film 20 usually has high transparency. Specifically, the total light transmittance of the optical film 20 is preferably 85% or more, more preferably 90% or more. The upper limit is ideally 100%. Here, the total light transmittance can be measured according to JIS K7361-1997.
Moreover, although the optical film 20 depends on a use, it usually has a small haze. Specifically, the haze of the optical film 20 is usually 10% or less, preferably 5% or less, more preferably 1% or less. The lower limit value is ideally zero, but is usually 0.1% or more. Here, haze can be measured according to JIS K7361-1997.

[3. Process of bonding optical film and protective film]
After obtaining the optical film 20, the optical film 20 and the protective film 30 are bonded together to obtain the multilayer film 10.

[3.1. Protective film]
The protective film 30 is a film that can be bonded to and peeled from the optical film 20. By bonding the protective film 30 to the optical film 20, it is possible to prevent the surface of the optical film 20 from being damaged or to improve the handling properties.

  As shown in FIG. 2, the arithmetic average roughness Ra of the surface 30D opposite to the surface 30U to be bonded to the optical film 20 of the protective film 30 is usually 0.2 μm or more, preferably 0.3 μm or more, more preferably It is 0.5 μm or more, usually 1.4 μm or less, preferably 1.0 μm or less, more preferably 0.8 μm or less. Usually, the surface 30U bonded to the optical film 20 of the protective film 30 is an adhesive surface. For this reason, usually, the arithmetic average roughness Ra of the surface 30D that is not the adhesive surface of the protective film 30 is set within the above range.

  According to the study of the present inventors, the arithmetic average roughness Ra of the surface 30D of the protective film 30 opposite to the optical film 20 is largely related to the generation of wrinkles and gauge bands of the optical film roll 100. It is thought that there is. When the multilayer film 10 is wound as the optical film roll 100, the surface 20U on the optical film side of the multilayer film 10 and the surface 30D on the protective film side of the multilayer film 10 come into contact with each other. At this time, the surface roughness of the surface 30D on the protective film side of the multilayer film 10 (that is, the surface roughness of the surface 30D on the side opposite to the optical film 20 of the protective film 30) is the entrainment of air between the multilayer films. It has a great influence on the volume and emissions.

  Specifically, when the surface of the surface 30D opposite to the optical film 20 of the multilayer film 10 becomes rough, the amount of air entrained between the multilayer films at the time of winding increases and deforms and wrinkles. It tends to occur. Furthermore, if the surface roughness of the surface 30D on the opposite side of the optical film 20 of the multilayer film 10 is rough, the air passage becomes large, and the entrained air is likely to escape. Then, when the thickness of the air layer changes due to the air escaped from between the multilayer films 10, the multilayer film is deformed following the change in thickness, and thus wrinkles are likely to occur in the optical film roll. Therefore, in this embodiment, wrinkles are prevented by setting the arithmetic average roughness Ra of the surface 30D of the protective film 30 opposite to the optical film 20 to be equal to or less than the upper limit value of the above range.

  On the other hand, if the surface of the surface 30D opposite to the optical film 20 of the multilayer film becomes smooth, the amount of air entrained between the multilayer films 10 at the time of winding decreases, and a gauge band is likely to occur. Therefore, in this embodiment, the gauge band is prevented by setting the arithmetic average roughness Ra of the surface 30D of the protective film 30 opposite to the optical film 20 to be equal to or higher than the lower limit of the above range.

  The composition and layer structure of the protective film are arbitrary as long as the effects of the present invention are not significantly impaired. For example, the protective film may be a film having a single layer structure including only one layer, or may be a film having a multilayer structure including two or more layers. The film thickness of the protective film is arbitrary, and is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 80 μm or less, preferably 60 μm or less, more preferably 40 μm or less.

  Especially, it is preferable that the protective film 30 contains a polyolefin-type polymer. If the protective film 30 is a film having a single layer structure, the layer preferably includes a polyolefin polymer. Moreover, if the protective film 30 is a film of a multilayer structure, it is preferable that at least one layer contains a polyolefin polymer. By using a polyolefin-based polymer, molding by coextrusion becomes possible, and productivity is excellent.

The protective film 30 is a film having a multilayer structure that usually includes two or more layers. When the suitable example of the protective film 30 is given, the film provided with the adhesion layer and the back layer; The film provided with the adhesion layer, the intermediate | middle layer, and the back layer in this order; In this case, the surface of the adhesive layer forms the adhesive surface of the protective film 30.
Hereinafter, suitable examples of the protective film will be described.

Adhesive layer The adhesive layer is a layer that is located on the surface of the protective film 30 on the optical film side and can adhere to the optical film 20. The pressure-sensitive adhesive layer is formed to contain a pressure-sensitive adhesive, and the protective film 30 can be fixed to the optical film 20 by the pressure-sensitive adhesive force.
Examples of the pressure-sensitive adhesive include a rubber-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a polyvinyl ether-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive. In addition, an adhesive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  Among pressure-sensitive adhesives, a block copolymer represented by general formula A-B-A or general formula AB (wherein, A represents a styrenic polymer block, and B represents a butadiene polymer block) A rubber-based pressure-sensitive adhesive containing an isoprene polymer block, and a polymer block selected from the group consisting of olefin polymer blocks obtained by hydrogenation thereof; and an acrylic pressure-sensitive adhesive.

  In the block copolymer represented by the general formula A-B-A or the general formula A-B, the styrene polymer block A has a weight average molecular weight of 12,000 or more and 100,000 or less, and a glass transition temperature. The thing of 20 degreeC or more is preferable. In addition, the polymer block B selected from the group consisting of a butadiene polymer block, an isoprene polymer block, and an olefin polymer block obtained by hydrogenating them has a weight average molecular weight of 10,000 to 300,000, A glass transition temperature of −20 ° C. or lower is preferred. Further, the weight ratio of the A component and the B component (A component / B component) is preferably 5/95 or more, more preferably 10/90 or more, preferably 50/50 or less, more preferably 30/70. It is as follows.

  Examples of the block copolymer represented by the general formula A-B-A include styrene-ethylene / propylene-styrene copolymer, styrene-ethylene / butylene-styrene copolymer, and hydrogenated products thereof. Examples of the block copolymer represented by the general formula AB include styrene-ethylene / propylene copolymer, styrene-ethylene / butylene copolymer and hydrogenated products thereof. it can.

  Examples of acrylic adhesives are methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, octyl Alkyl (meth) acrylates such as (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate; alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and butoxyethyl (meth) acrylate; cyclohexyl ( (Meth) acrylamides such as (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, vinyl acetate, (meth) acrylamide, N-methylol (meth) acrylamide; And the like homopolymers or copolymers. In addition, (meth) acrylate means acrylate and methacrylate, and (meth) acryl means acryl and methacryl.

  The acrylic pressure-sensitive adhesive is preferably used by copolymerizing an acrylic monomer having a functional group. Examples of acrylic monomers having a functional group include unsaturated acids such as maleic acid, fumaric acid and (meth) acrylic acid; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2 -Hydroxyhexyl (meth) acrylate, dimethylaminoethyl methacrylate, (meth) acrylamide, N-methylol (meth) acrylamide, glycidyl (meth) acrylate, maleic anhydride and the like can be mentioned. In addition, the acrylic monomer which has a functional group may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The acrylic pressure-sensitive adhesive may contain a crosslinking agent as necessary. The cross-linking agent is a compound that undergoes a thermal cross-linking reaction with a functional group present in the copolymer, and finally forms an adhesive layer having a three-dimensional network structure. By including a cross-linking agent, the adhesion of the protective film 30 to other layers (intermediate layer, back layer, etc.) in contact with the adhesive layer, toughness, solvent resistance, water resistance, etc. of the protective film 30 are improved. Can do. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, urea compounds, epoxy compounds, amino compounds, amide compounds, aziridine compounds, oxazoline compounds, silane coupling agents, and modified products thereof. You may use suitably. In addition, a crosslinking agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  From the viewpoint of the crosslinkability and toughness of the adhesive layer, it is preferable to use an isocyanate compound and a modified product thereof as the crosslinking agent. An isocyanate compound is a compound having two or more isocyanate groups in one molecule, and is roughly classified into an aromatic compound and an aliphatic compound. Examples of the aromatic isocyanate compound include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, naphthalene diisocyanate, tolidine diisocyanate, paraphenylene diisocyanate, and the like. Examples of the aliphatic isocyanate compound include hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, tetramethylxylene diisocyanate, and xylylene diisocyanate. Furthermore, examples of modified products of these isocyanate compounds include biuret bodies, isocyanurate bodies, and trimethylolpropane adduct bodies of isocyanate compounds.

  When using a crosslinking agent, in order to accelerate the crosslinking reaction, for example, a crosslinking catalyst such as dibutyltin laurate may be included in the pressure-sensitive adhesive.

  If necessary, the adhesive layer may contain a tackifying polymer. Examples of tackifying polymers include aromatic hydrocarbon polymers, aliphatic hydrocarbon polymers, terpene polymers, terpene phenol polymers, aromatic hydrocarbon-modified terpene polymers, chroman indene polymers, and styrene-based polymers. Examples thereof include a polymer, a rosin polymer, a phenol polymer, and a xylene polymer. Among them, an aliphatic hydrocarbon polymer such as low density polyethylene is preferable. However, the specific kind of tackifying polymer is appropriately selected from the viewpoints of compatibility with other polymers, the melting point of the resin, and the adhesive strength of the adhesive layer. Moreover, a tackifying polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The amount of the tackifying polymer is, for example, preferably 5 parts by weight or more, preferably 200 parts by weight or less, more preferably 100 parts by weight or less with respect to 100 parts by weight of the block copolymer. . By setting the amount of the tackifying polymer to be equal to or more than the lower limit of the above range, the protective film 30 can be prevented from being lifted or peeled off when it is bonded to the optical film 20. Moreover, by setting it as the upper limit value or less, the feeding tension of the protective film 30 is suppressed to prevent wrinkles and scratches when bonded to the optical film 20, or to prevent bleeding out of the tackifying polymer. The adhesive strength of the adhesive layer can be kept high.

If necessary, the adhesive layer may contain additives such as a softening agent, an anti-aging agent, a filler, a colorant (such as a dye or a pigment). In addition, an additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
Examples of the softening agent include process oil, liquid rubber, and plasticizer.
Examples of the filler include barium sulfate, talc, calcium carbonate, mica, silica, and titanium oxide.

  The adhesive strength of the adhesive layer is preferably 0.4 N / cm or more, more preferably 0.6 N / cm or more with respect to other layers (intermediate layer, back layer, etc.) in contact with the adhesive layer in the protective film 30, 6N / Cm or less is preferable, and 4 N / cm or less is more preferable. By making the adhesive strength equal to or higher than the lower limit of the above range, the protective film 30 can be prevented from being lifted and peeled off when the protective film 30 is bonded to the optical film 20. Moreover, the wrinkles and damage | wound at the time of bonding with the optical film 20 can be prevented by suppressing the drawing | extracting tension | tensile_strength of the protective film 30 by setting it as an upper limit or less.

  The thickness of the pressure-sensitive adhesive layer is usually 1.0 μm or more, preferably 2.0 μm or more, and is usually 50 μm or less, preferably 30 μm or less. By setting the film thickness of the adhesive layer to be equal to or higher than the lower limit of the above range, the adhesive force can be increased and the protective film 30 can be prevented from floating and peeling off when the protective film 30 is bonded to the optical film 20. Moreover, since it can prevent that adhesive force becomes high too much by making it below an upper limit and can suppress the drawing | feeding tension | tensile_strength of the protective film 30, it can prevent the wrinkles and damage | wound at the time of bonding with the optical film 20. . Moreover, since it can prevent that the stiffness of the protective film 30 becomes strong too much, the handleability of the protective film 30 can be made favorable.

-Back layer A back layer is a layer located in the surface on the opposite side to the optical film 20 with respect to the adhesion layer, and is normally located in the surface on the opposite side to the optical film 20 of the protective film 30. FIG. This back layer usually does not adhere to the optical film 20. In the protective film 30 having the back layer, the arithmetic average roughness Ra of the exposed surface of the back layer is usually the arithmetic average roughness Ra of the surface 30D opposite to the adhesive surface 30U of the protective film 30.

  Usually, the back layer is formed of a resin. The polymer contained in the resin forming the back layer may be a homopolymer or a copolymer. A suitable example is a polyolefin polymer.

  The polyolefin-based polymer is a homopolymer or copolymer of a chain olefin, or a copolymer of a chain olefin and a monomer copolymerizable with the chain olefin. For example, polyethylene, polypropylene, ethylene-propylene copolymer, propylene-α-olefin copolymer, ethylene-α-olefin copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene-methyl (meta ) Acrylate copolymer, ethylene-n-butyl (meth) acrylate copolymer, ethylene-vinyl acetate copolymer, and the like. Here, examples of the polyethylene include low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene. Examples of the ethylene-propylene copolymer include a random copolymer and a block copolymer. Furthermore, examples of the α-olefin include butene-1, hexene-1, 4-methylpentene-1, octene-1, pentene-1, and heptene-1.

  Among the polyolefin polymers described above, a polymer selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, and propylene-α olefin copolymer is preferable, and ethylene-propylene copolymer and propylene-α olefin copolymer are preferable. A polymer (hereinafter, these may be collectively referred to as “propylene-based copolymer”) is more preferable, and an ethylene-propylene copolymer is particularly preferable.

  The above-mentioned polymers may be used alone or in combination of two or more at any ratio. Among these, it is preferable to use a combination of a propylene-based copolymer such as an ethylene-propylene copolymer and low-density polyethylene. In this case, it is particularly preferable to combine 60% to 90% by weight of the propylene copolymer and 40% to 10% by weight of the low density polyethylene. The higher the ethylene content, the lower the melting point of the ethylene-propylene copolymer. For this reason, from the viewpoint of facilitating coextrusion and enabling low temperature extrusion, the ethylene content as a comonomer is preferably in the range of 3 mol% to 7 mol%. In addition, when adding heat resistance to a back surface layer, you may select suitably so that ethylene content may be decreased and desired heat resistance may be acquired.

  The melt flow rate (hereinafter sometimes referred to as “MFR”) at 230 ° C. of the propylene-based copolymer is preferably in the range of 5 g / 10 min to 40 g / 10 min. In particular, those having an MFR in the range of 20 g / 10 min to 40 g / 10 min are more preferable because they can be extruded at low temperature and the surface of the back layer is easily roughened by combining with low density polyethylene.

The low density polyethylene constituting the back layer preferably has an MFR at 190 ° C. of 0.5 g / 10 min to 5 g / 10 min.
Further, the low density polyethylene preferably has a density of 0.910 g / cm ^{3 to} 0.929 g / cm ³ . By making the density of the low density polyethylene equal to or higher than the lower limit of this range, the surface roughness of the surface of the back layer can be easily adjusted to an appropriate range. Moreover, by making it below the upper limit value, detachment of the resin from the protective film 30 due to rubbing with a roll (for example, a metal roll, a rubber roll, etc.) used for conveyance can be prevented, and generation of white powder can be suppressed.

  Although the polymer (for example, a propylene-type copolymer and low density polyethylene) contained in a back surface layer may be different from the polymer contained in an adhesion layer, it is preferable to use the same polymer.

  In the resin forming the back layer, unless the effects of the present invention are significantly impaired, for example, fillers such as talc, stearamide, calcium stearate, lubricants, antioxidants, ultraviolet absorbers, pigments, antistatic agents, Additives such as nucleating agents may be included. In addition, an additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The thickness of the back layer is a ratio (adhesive layer / back layer) to the thickness of the adhesive layer, usually 1/40 or more, preferably 1/20 or more, usually 1/1 or less, preferably 1/2 or less. It is. Thereby, since it can prevent that the thickness of a back surface layer becomes thin compared with an adhesion layer, film forming property can be improved and a fish eye can be prevented. Moreover, since it can prevent that the thickness of a back surface layer becomes too thick compared with an adhesion layer, the drawing | feeding tension | tensile_strength of the protective film 30 can be suppressed, and the wrinkle and damage | wound at the time of bonding with the optical film 20 can be prevented. .

-Intermediate layer An intermediate layer may be provided between the adhesive layer and the back layer as necessary. The intermediate layer is usually formed of a resin, but among them, it is preferably formed of a resin containing a polyolefin polymer.

  Examples of the polyolefin polymer contained in the intermediate layer include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer, polypropylene, and ethylene-propylene copolymer. (Random copolymer and / or block copolymer), α-olefin-propylene copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene-methyl (meth) acrylate copolymer, ethylene-n-butyl (Meth) acrylate copolymer, ethylene-vinyl acetate copolymer and the like. In addition, a polyolefin polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. However, the polyolefin polymer contained in the intermediate layer is preferably a polyolefin polymer of a different type from the polymers contained in the adhesive layer and the back layer.

  The intermediate layer may include a material for forming the adhesive layer and a material for forming the back layer as necessary. Usually, when manufacturing the protective film 30 by a coextrusion molding method, the part where the film thickness of an edge part is not uniform is slit by a slit process etc., and is removed. By using the portion thus removed as a raw material for the intermediate layer, the amount of the raw material used can be reduced.

  In the intermediate layer, unless the effects of the present invention are significantly impaired, for example, fillers such as talc, stearamide, calcium stearate, lubricants, antioxidants, ultraviolet absorbers, pigments, antistatic agents, nucleating agents, etc. These additives may be included. In addition, an additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The film thickness of the intermediate layer is usually 13 μm to 70 μm.

-Manufacturing method of protective film 30 You may manufacture the protective film 30 with the following manufacturing method (i)-(iii), for example.
(I) A method of co-extruding the material of the adhesive layer and the material of the back surface layer, and the material of the intermediate layer as required.
(Ii) A method in which a back surface layer or an intermediate layer is prepared, and an adhesive is applied to the prepared layer to form an adhesive layer.
(Iii) A method in which an adhesive layer and a back layer, and an intermediate layer are separately prepared as necessary, and the prepared layers are bonded and integrated.

  Among the exemplified production methods, the production method (i) by the co-extrusion molding method is such that the adhesive layer and the back layer or the intermediate layer are in close contact, and the adhesive residue on the optical film 20 hardly occurs. This is particularly preferable because it has advantages such as the fact that the cost is low because of simplification. Here, “glue residue” refers to a phenomenon in which the adhesive remains on the optical film 20 after the protective film 30 is peeled off. In the protective film 30 produced by the production method (i), a polyolefin polymer such as branched low-density polyethylene or polypropylene is often used as the back layer. On the other hand, for the adhesive layer, for example, vinyl acetate, linear low density polyethylene, metallocene linear low density polyethylene and the like are usually used. Among these, from the viewpoint of avoiding adhesive residue and an increase in adhesive strength over time, a linear low density polyethylene adhesive is often used rather than vinyl acetate.

  Moreover, in the protective film 30 manufactured by the manufacturing method (ii) by the coating method, polyethylene terephthalate and a polyolefin polymer are usually used as the back layer, and a rubber-based adhesive and an acrylic adhesive are often used for the adhesive layer. Agents are often used. Among these, when there is a concern about foreign matter in the protective film 30, it is preferable to use polyethylene terephthalate for the back layer rather than the polyolefin polymer. Further, in the production method (ii), when production is performed in a clean room, a high-quality protective film 30 having no foreign matter can be obtained.

In order for the surface 30D of the protective film 30 opposite to the optical film 20 to have the arithmetic average roughness Ra described above, for example, by deforming the surface of the back layer, a predetermined arithmetic surface roughness Ra is obtained. Concavities and convexities having the following may be formed. For example, using a forming roll having irregularities, a nip molding method of pressing the protective film 30 immediately after extrusion obtained in the coextrusion molding method to transfer the irregularities to the surface of the back layer; A method of peeling the release film after transferring the unevenness of the release film by pressing with a release film having; a fine particle is sprayed on the surface of the back layer of the protective film 30 to cut the surface of the back layer of the protective film 30 And the like. The step of deforming the surface of the back layer may be before or after the back layer and the adhesive layer are bonded together.
Furthermore, you may form an unevenness | corrugation in the surface of a back surface layer by adjusting the composition of a back surface layer. For example, a method in which fine particles having a predetermined particle size are contained in the back layer to form irregularities in the back layer; a method in which the back layer is formed by adjusting the compounding ratio of materials such as a resin forming the back layer, etc. Is mentioned.

Among the above-mentioned, since the protective film 30 without uneven transfer unevenness can be obtained with a wide width, a nip forming method using an uneven forming roll is preferable, and protection is performed using a mirror surface roll and an uneven forming roll. A method of sandwiching the film 30 is particularly preferable.
Examples of the surface material of each mirror roll and shaping roll include metal, rubber, and resin. These are selected so that the desired uneven shape can be transferred to the surface of the back layer of the protective film 30. However, the hardness of the shaping roll is preferably not less than the hardness of the mirror roll. Further, for example, the protective film 30 may be narrowed via a resin film having a surface property equivalent to that of a mirror roll and softer than the shaping roll.

  The mirror roll and the shaping roll are preferably those capable of independently adjusting the temperature. The temperature of the mirror roll is preferably 40 ° C. or higher and 160 ° C. or lower, and the temperature of the shaping roll is preferably 60 ° C. or higher and 200 ° C. or lower. The temperature of the mirror roll is more preferably from 60 ° C. to 130 ° C., and the temperature of the shaping roll is more preferably from 80 ° C. to 180 ° C. By setting the temperature of the mirror roll or the shaping roll to be equal to or higher than the lower limit temperature in the above range, uneven transfer unevenness can be prevented. Moreover, it can prevent that the protective film 30 winds around a mirror surface roll or a shaping roll by making the temperature of a mirror surface roll or a shaping roll below the upper limit temperature of the said range.

  In the nip forming method, the above-mentioned arithmetic average roughness Ra of the surface 30D of the protective film 30 opposite to the optical film 20 is the temperature of the protective film 30, the mirror roll and the shaping roll, the roll speed, and the protection during the clamping. The pressure at the time of clamping the film 30 and the material of the surface of the mirror roll and the shaping roll can be adjusted by appropriately selecting according to the characteristics of the material forming the protective film 30. Usually, the mirror roll and the shaping roll temperature are preferably (Tg−60) to (Tg + 20) ° C. with respect to the glass transition temperature (Tg) of the resin forming the back layer.

If necessary, the surface of the protective film 30 may be subjected to surface modification treatment. Examples of the surface modification treatment include energy ray irradiation treatment and chemical treatment.
Moreover, you may print on the surface of the protective film 30 as needed.

[3.2. Lamination]
The multilayer film 10 is obtained by bonding the optical film 20 and the protective film 30 together. At the time of bonding, it is preferable to apply a predetermined magnitude of tension to the optical film 20 and the protective film 30 in order to eliminate wrinkles and slack of the optical film 20 and the protective film 30. Further, at the time of bonding, it is preferable to perform bonding while applying pressure, for example, by a nip roll or the like.

  The multilayer film 10 thus manufactured includes an optical film 20 and a protective film 30. In the multilayer film 10, the optical film 20 is usually exposed on one surface, and the protective film 30 is exposed on the other surface. At this time, an optional layer may be further provided between the optical film 20 and the protective film 30. The arbitrary layer may be one layer or two or more layers. Moreover, when there are two or more arbitrary layers, these layers may be the same or different.

  The width of the multilayer film 10 is preferably 1500 mm or more, and more preferably 1800 mm or more. In general, wrinkles or gauge bands are likely to occur in a film roll wound with a wide film. However, the multilayer film 10 according to the present embodiment can realize a good winding shape when wound while having such a wide width. Moreover, the upper limit of the width | variety of the multilayer film 10 is 2500 mm or less normally.

[4. Step of winding a multilayer film]
FIG. 4 is a diagram schematically showing how the optical film roll 100 is obtained by winding the multilayer film 10.
As shown in FIG. 4, after obtaining the multilayer film 10, the multilayer film 10 is wound in roll shape, and the optical film roll 100 is obtained. Usually, in the process of winding the multilayer film 10, the winding device 200 provided with the winding roll 210 and the contact pressure roller 220 is used. Then, the optical film roll 100 is obtained by winding the multilayer film 10 on the winding roll 210 while applying pressure to the multilayer film 10 by pressing with the contact pressure roller 220.

  By winding the multilayer film 10 while applying a surface pressure by the contact pressure roller 220, it is easy to suppress the amount of air entrained in high-speed winding. For this reason, generation | occurrence | production of a wrinkle can be prevented and the optical film roll 100 which has a favorable winding form can be manufactured.

At this time, when the arithmetic average roughness of the surface 30D of the protective film 30 opposite to the optical film 20 is Ra (μm), the pressure P (N / m) of the contact roller 220 is expressed by the following formula (4 ) Is preferably satisfied.
50 × Ra + 75 ≦ P ≦ 23 × Ra + 160 (4)

  As described above, when winding the multilayer film 10, it is preferable to suppress and control the amount of air entrained between the multilayer films 10 to be wound from the viewpoint of preventing wrinkles and gauge bands. At this time, the amount of the air involved varies depending on the surface roughness of the surface 30 </ b> D on the opposite side of the protective film 30 from the optical film 20. Therefore, the pressure P of the contact roller 220 is preferably set according to the surface roughness of the surface 30D of the protective film 30 opposite to the optical film 20.

  The rougher the surface roughness of the surface 30D opposite to the optical film 20 of the protective film 30, the greater the amount of air entrained during winding, so the pressure P of the contact roller 220 is increased, It is preferable to suppress air entrainment. Furthermore, if the surface roughness of the surface 30D opposite to the optical film 20 of the protective film 30 is rough, the amount of air entrained at the time of winding increases, so the air flow due to the change in the pressure P of the contact roller 220 is increased. The change in the amount of entrainment also increases. For this reason, the surface roughness of the surface 30D opposite to the optical film 20 of the protective film 30 is less than the surface roughness of the surface 30D opposite to the optical film 20 of the protective film 30. When it is rough, the preferable range of the pressure P of the contact roller 220 is narrowed. Therefore, the pressure P of the contact roller 220 is within a range according to the Ra as shown in Expression (4) in the range of the arithmetic surface roughness Ra of the surface 30D of the protective film 30 opposite to the optical film 20. Preferably there is.

  The winding speed of the multilayer film 10 is usually 5 m / min or more, preferably 10 m / min or more, and is usually 50 m / min or less, preferably 45 m / min or less, more preferably 40 m / min or less. By setting the winding speed to be equal to or higher than the lower limit value of the above range, the production efficiency can be increased, and by setting the winding speed to be equal to or lower than the upper limit value, the amount of air entrainment can be suppressed.

[5. Optical film]
The obtained optical film roll 100 is a roll formed by winding the multilayer film 10 in which the optical film 20 and the protective film 30 are bonded together into a roll shape. Since the optical film roll 100 can suppress the generation of wrinkles and gauge bands, the rolled shape can be improved. In particular, since this optical film roll 100 uses a wide film containing an alicyclic structure-containing polymer as the optical film 20, it is possible to improve the winding shape while using the easily deformable optical film 20. , With significant significance.

The number of windings of the optical film roll 100 is not limited, but is usually 40 times or more, preferably 60 times or more, and usually 27000 times or less, preferably 13000 times or less.
Moreover, although there is no restriction | limiting in the outer diameter of the optical film roll 100, Usually, it is 160 mm or more, Preferably it is 190 mm or more, Usually, 2300 mm or less, Preferably it is 1200 mm or less.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the embodiments shown below, and may be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope.
In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified. In the following description, the operation was performed in an environment of normal temperature and normal pressure unless otherwise specified for temperature and pressure.

[Evaluation method]
(1) Measuring method of film thickness of film FIG. 5: is a figure explaining the measuring method of the film thickness of the film in an Example and a comparative example.
Using an on-line infrared film thickness meter (“RX-200” manufactured by Kurabo Industries), the film thickness of the film 310 being conveyed in the MD direction indicated by the arrow A1 was measured as shown in FIG. At this time, the measurement point was reciprocated so that the measurement point crossed the film 310 in the width direction Y, and the measurement was performed so as to draw a trajectory 320 in which the measurement point was bent. The measurement was performed 10 times or more in the film width direction at intervals of 10 mm in the width direction. An average value at each position in the width direction was calculated from the obtained measurement results.

(2) Measuring method of surface roughness Arithmetic average roughness Ra was measured using "New View 5000" manufactured by Zygo Co., Ltd. with an objective lens 10 times and a measurement area of 1.82 mm x 1.36 mm.

(3) Appearance evaluation method of optical film roll The appearance of the optical film roll immediately after winding the multilayer film was evaluated by palpation. Wrinkles were judged as “Yes” and “No”. As for the gauge band, “A” indicates that there is no unevenness corresponding to the gauge band, “B” indicates that there is a weak unevenness that is not harmful as a film, and “B” indicates that there is a strong unevenness that is harmful as a film. The determination was made as “C”.

[Example 1]
(Manufacture of unstretched film)
FIG. 6 is a diagram schematically illustrating an optical film roll manufacturing apparatus according to the first embodiment.
A pellet of a norbornene-based resin (“ZEONOR1420” manufactured by Nippon Zeon Co., Ltd.) containing an alicyclic structure-containing polymer was dried at 100 ° C. for 5 hours, and then supplied to a single screw extruder. This resin was melted at 250 ° C. and extruded from a T die 410 onto a casting drum 420 as shown in FIG.

The T die 410 includes a plurality of manual adjustment bolts 411 and thermal expansion bolts 412 for adjusting the size (opening width) of the lip gap of the T die 410 in the TD direction (that is, in the width direction of the unstretched film 510). I had it.
The manual adjustment bolt 411 is a bolt for adjusting the lip gap of the T die 410 by the user's operation, and is a bolt for setting the basic film thickness of the unstretched film 510. In the experiment, the size of the lip gap was adjusted by appropriately squeezing the manual adjustment bolt 411 so that the unstretched film 510 had a desired film thickness.

  Further, the thermal expansion bolt 412 is a bolt for adjusting the size of the lip gap of the T die 410 by an appropriate drive mechanism according to the control of the controller 431, and the film thickness at each position in the width direction of the stretched film 520 is finely adjusted. It is a bolt for adjusting. In the experiment, according to the film thickness profile in the width direction of the stretched film 520 sent from the online infrared film thickness meter 432 described later, the film thickness at each position in the width direction of the stretched film 520 is a desired film thickness. Thus, the control program of the controller 431 is set so that the controller 431 can control the restriction of the thermal expansion bolt 412.

  The resin extruded onto the casting drum 420 was cooled to obtain an unstretched film 510 having a thickness of 80 μm as a resin film.

(Stretching film)
The obtained unstretched film 510 was stretched 1.15 times in the MD direction at a stretching temperature of 135 ° C. using a stretching machine 440, and stretched 1.5 times in the TD direction at a stretching temperature of 140 ° C. A stretched film 520 was obtained as a film.
The film thickness of this stretched film 520 was measured with an on-line infrared film thickness meter 432, and a film thickness profile in the width direction of the stretched film 520 was obtained. The obtained film thickness profile was sent to the controller 431. The controller 431 controls the drawing of the thermal expansion bolt 412 as described above, and feedback control that can adjust the film thickness of the stretched film 520 so as to have a desired film thickness at each position in the width direction of the stretched film 520. Continued.

  The stretched film 520 had a tensile elastic modulus of 2150 MPa and an average film thickness of 50 μm. The arithmetic average roughness Ra of the stretched film 520 was 0.01 μm on both sides.

(Preparation of protective film)
A polyethylene resin film was prepared as the protective film 530. This protective film 530 had an adhesive surface that could be bonded to a norbornene-based resin film, and had a film thickness of 28 μm, a width of 2,030 mm, and a length of 3,500 m.
It was 0.8 micrometer when the arithmetic surface roughness Ra of the surface on the opposite side to the adhesion surface of the protective film 530 was measured by the method mentioned above.

(Lamination of stretched film and protective film)
A multilayer film 540 including the stretched film 520 and the protective film 530 was obtained by bonding the adhesive surface of the protective film 530 to the stretched film 520 using nip rolls 451 and 452. At this time, the nip pressure was 0.5 MPa, and the tension of the stretched film 520 and the protective film 530 was 100 N / m.

(Take-up)
Using a winding device 460 having a contact roller 461, the multilayer film 540 is wound around an FRP core, which is a winding roll 462 having an axial length of 2100 mm, and an optical having a width of 1,960 mm and a winding length of 2,500 m. A film roll 550 was obtained. At this time, the multilayer film 540 was wound with the stretched film inside. Moreover, when winding up, arithmetic mean roughness Ra by the side of a protective film was 0.8 micrometer. The pressure of the contact roller 461 was 150 N / m. Further, the winding conditions were a tension of 100 N / m at the beginning of winding of the multilayer film 540 and a speed of 26 m / min. Furthermore, the tension of the multilayer film 540 during winding was adjusted so that the tension at the end of winding became 90% linearly gradually with respect to the tension at the beginning of winding.
About the obtained optical film roll 550, the external appearance evaluation was performed by the method mentioned above. The results are shown in Table 1.

[Examples 2-7, Comparative Examples 1-7]
An optical film roll was produced in the same manner as in Example 1 except that the following items (i) to (iii) were appropriately changed, and the configuration was changed as shown in Table 1 or Table 2.
(I) As the protective film, a film having an arithmetic surface roughness Ra on the surface opposite to the adhesive surface different from that in Example 1 was prepared.
(Ii) The film thickness profile of the stretched film was changed by adjusting the manual adjustment bolt or thermal expansion bolt of the T die.
(Iii) The pressure of the contact pressure roller when winding the multilayer film was changed.

  In each Example and Comparative Example, the arithmetic surface roughness Ra of the surface opposite to the adhesive surface of the protective film was measured. Moreover, about each obtained optical film roll, external appearance evaluation was performed by the method mentioned above. The results are shown in Tables 1 and 2.

[result]
Table 1 shows the results of the examples and Table 2 shows the results of the comparative examples. Moreover, in the following Table 1 and Table 2, the column of “Ra [μm] of the protective film” represents the arithmetic average roughness Ra [μm] of the surface of the protective film opposite to the stretched film. In the section of film thickness evaluation, the value of “(h _w −h _{w ± 200} ) / h × 100” is the maximum value in the entire evaluation target range.

[Consideration]
In Examples 1 to 7, a protective film having an arithmetic average roughness Ra on the side opposite to the stretched film in the range of 0.3 μm to 1.4 μm is used. Moreover, in the film thickness of the stretched film, the difference between the film thickness at the center in the width direction and the film thickness at both ends is within a predetermined range. Moreover, there is no steep film thickness change in the film thickness profile in the width direction of the stretched film. Furthermore, when the multilayer film is wound, a pressure corresponding to the arithmetic average roughness Ra of the surface of the protective film on the side opposite to the stretched film is applied by the contact pressure roller. Thereby, as can be seen from Table 1, in the appearance evaluation of the optical film roll, no wrinkle was generated, and the gauge band evaluation was a good evaluation result of A to B. The good results were obtained because the amount of air entrained during the winding of the multilayer film and the amount of air discharged from the wound optical film roll were within an appropriate range. It is done.

  On the other hand, in the comparative example, both results were inferior to the example in at least one of the wrinkles and the gauge band. The reason for this result is considered as follows.

  In Comparative Example 1 and Comparative Example 2, the film thickness profile of the multilayer film satisfied Expressions (1) to (3). However, since the arithmetic average roughness Ra of the surface opposite to the stretched film of the protective film was as small as 0.2 μm, it was considered that air could not be sufficiently entrained, resulting in the generation of a gauging gauge band. .

  Further, in Comparative Example 3 and Comparative Example 4, since the arithmetic average roughness Ra of the surface of the protective film opposite to the stretched film was as large as 1.7 μm, the air was excessively wound and further wound. It is considered that in the roll, air is frequently discharged from the air layer between the multilayer films, and the size of the air layer is greatly changed, resulting in generation of wrinkles.

Comparative Example 5, according to Equation (1) _{"(h c -h e1) / h} × 100 " and according to the equation (2) _{"(h c -h e2) / h} × 100 " is -0.5% It has become. Thus, as for the stretched film of the comparative example 5, the center part of the width direction is thinner than the edge part. For this reason, at the time of winding, the air entrained in the central part of the multilayer film is increased, and it is considered that wrinkles are generated.

In Comparative Example 6, according to formula (1) according to _{"(h c -h e1) / h} × 100 " and (2) _{"(h c -h e2) / h} × 100 " and a 4% It has become. Thus, the stretched film of Comparative Example 6 has a large difference in film thickness between the central portion and the end portion in the width direction. For this reason, the pressure of the contact roller is concentrated on the central portion in the width direction of the multilayer film, and air is not sufficiently caught, which is considered to have resulted in the generation of a gauging gauge band.

In Comparative Example 7, “(h _w −h _{w ± 200} ) / h × 100” according to Expression (3) is 3%. Thus, the stretched film of Comparative Example 7 has a sharp change in film thickness in the width direction. For this reason, it is considered that the air between the multilayer films could not absorb the abrupt change in the film thickness, leading to the generation of a gauging gauge band.

  The optical film roll and the optical film roll manufacturing method of the present invention are applied to an optical film roll using an optical film such as a retardation film, a polarizing film, a brightness enhancement film, a light diffusing film, a light collecting film, and a reflective film. Yes.

DESCRIPTION OF SYMBOLS 10 Multilayer film 20 Optical film 30 Protective film 100 Optical film roll 200 Winding device 210 Winding roll 220 Pressure-contact roll 310 Film 320 Trajectory 410 T die 411 Manual adjustment bolt 412 Thermal expansion bolt 420 Casting drum 431 Controller 432 Online infrared film thickness meter 440 Stretching machine 451 Nip roll 452 Nip roll 460 Winding device 461 Pressure roller 462 Winding roll 510 Unstretched film 520 Stretched film 530 Protective film 540 Multilayer film 550 Optical film roll

Claims (4)

An optical film roll formed by winding an optical film containing an alicyclic structure-containing polymer and a multilayer film obtained by laminating a protective film peelable from the optical film into a roll,
The multilayer film has a width of 1,500 mm or more,
The arithmetic average roughness Ra of the surface of the protective film opposite to the optical film is 0.3 μm or more and 1.4 μm or less,
The optical film has an average film thickness in the width direction of h, a film thickness in the center of the width direction of h _c , a film thickness at both ends in the width direction of h _e1 and h _e2 , and a film thickness at an arbitrary width position w. H _w (where w represents the distance from the end on either side in the width direction of the optical film, and w> 200 mm), the average of the width direction in the range of width position w ± 200 mm An optical film roll that satisfies the relationships of the following formulas (1) to (3) when the film thickness is _{hw ± 200} .
1.0 ≦ (h _c −h _e1 ) /h×100≦3.0 (1)
1.0 ≦ (h _c −h _e2 ) /h×100≦3.0 (2)
_{(H w -h w ± 200)} /h×100≦2.0 (3) 2. The optical film roll according to claim 1, wherein the arithmetic average roughness Ra of the surface of the optical film opposite to the protective film is 0.001 μm or more and 0.05 μm or less. A step of melt-extruding a resin containing an alicyclic structure-containing polymer to obtain an optical film,
A method for producing an optical film roll, comprising: a step of bonding a protective film peelable from the optical film to the optical film to obtain a multilayer film; and a step of winding the multilayer film into a roll.
The multilayer film has a width of 1,500 mm or more,
The arithmetic average roughness Ra of the surface of the protective film opposite to the optical film is 0.3 μm or more and 1.4 μm or less,
The optical film has an average film thickness in the width direction of h, a film thickness in the center of the width direction of h _c , a film thickness at both ends in the width direction of h _e1 and h _e2 , and a film thickness at an arbitrary width position w. H _w (where w represents the distance from the end on either side in the width direction of the optical film, and w> 200 mm), the average of the width direction in the range of width position w ± 200 mm The manufacturing method of an optical film roll which satisfy | fills the relationship of following formula (1)-(3), when a film thickness is _{hw +/- 200} .
1.0 ≦ (h _c −h _e1 ) /h×100≦3.0 (1)
1.0 ≦ (h _c −h _e2 ) /h×100≦3.0 (2)
_{(H w -h w ± 200)} /h×100≦2.0 (3) In the winding step, using a winding device including a winding roll and a contact pressure roller, the multilayer film is applied to the winding roll while being pressed by the contact pressure roller to apply a surface pressure to the multilayer film. Take up the film,
When the arithmetic average roughness of the surface of the protective film opposite to the optical film is Ra (μm), the pressure P (N / m) of the contact pressure roller satisfies the following formula (4): Item 4. The manufacturing method according to Item 3 .
50 × Ra + 75 ≦ P ≦ 23 × Ra + 160 (4)

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