JP2012061712A - Optical film roll and method for producing the same - Google Patents

Abstract

The present invention provides an optical film roll that can suppress the occurrence of band, wrinkle transfer and bubble biting, and is excellent in storage stability.
In an optical film roll 100, a multilayer film 30 in which an optical film 10 containing an alicyclic structure-containing polymer and a protective film 20 peelable from the optical film 10 are bonded together is wound into a roll. In addition, the arithmetic average roughness Ra of the surface of the protective film 20 opposite to the optical film 10 is set to 0.2 μm or more and 0.5 μm or less, and the average interval Sm of unevenness is set to 200 μm or more and 500 μm or less.
[Selection] Figure 1

Description

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

  Various optical films are used in various displays such as a liquid crystal display device, a plasma display panel (PDP), and an electroluminescence (EL) element. In these various displays, the demand for defects in optical films has become higher with the increase in screen size, thickness reduction, price reduction, and power saving. In particular, the width and thickness of optical films have been reduced in response to thinning and lower prices of displays, and along with this, the appearance of optical film rolls when the optical film is wound into a roll (hereinafter referred to as the following) (Referred to as "rolling form" as appropriate), storage stability after winding, sandwiching of air between the films when the optical film and the protective film are bonded together (hereinafter, this phenomenon is referred to as "bubble biting" as appropriate), and Improvements such as transfer of a protective film to an optical film having a rough surface shape (hereinafter, this phenomenon is appropriately referred to as “texture transfer”) have been a problem.

In order to solve these problems, Patent Document 1 proposes increasing the rigidity of the winding core. In Patent Document 2, it is proposed that the amount of air sandwiched between films at the time of winding is controlled by tension or nip pressure. Furthermore, Patent Document 3 and Patent Document 4 propose that the arithmetic average roughness of the surface of the optical film or the rough surface of the protective film is controlled to suppress blocking and control the friction coefficient.
A technique such as that disclosed in Patent Document 5 is also known.

JP 2001-106438 A Japanese Patent Laid-Open No. 08-091646 Japanese Patent Laid-Open No. 07-186335 JP 2008-080626 A JP 2009-090647 A

  However, in the conventional technique, smoothness is high, and an optical film having a small thickness has not been sufficiently improved. In particular, among optical films, an optical film containing an alicyclic structure-containing polymer has properties such as low slip and elastic modulus, so that it is easily deformed, and the conventional technique improves the appearance of the optical film roll. It is difficult to keep.

  For example, when the optical film containing the alicyclic structure-containing polymer is wide, when the optical film is wound into an optical film roll, the optical film rises and protrudes in the circumferential direction of the optical film roll. Part (hereinafter referred to as “band” as appropriate) may be formed. When such a band is formed, irregularities are generated on the surface of the optical film roll in the width direction of the optical film roll, and the appearance is deteriorated.

In addition, since an optical film containing an alicyclic structure-containing polymer has a low elastic modulus and is soft, the appearance of the optical film roll is likely to be deformed by long-term storage, and wrinkles are likely to occur due to heat shock or the like. Moreover, when the optical film is soft, when it is attached to the protective film and wound, transfer of the uneven shape on the surface of the protective film to the optical film (texture transfer) easily occurs.
Furthermore, in the optical film including the alicyclic structure-containing polymer, when the optical film and the protective film are bonded together, air is easily sandwiched between the optical film and the protective film, and bubble biting is likely to occur.

  When such band, grain transfer, bubble biting, etc. occur, the shape of the optical film may be deformed to cause an optical defect. In actual commercial transactions, if the appearance of the optical film roll is impaired, even if there is no loss in performance, the product value may be evaluated low due to the appearance. For this reason, even in an optical film roll that is soft and easily deformed, such as an optical film containing an alicyclic structure-containing polymer, the appearance of the optical film roll is suppressed by suppressing the occurrence of the band, texture transfer, bubble biting, etc. There was a need for technology to keep it.

  This invention is made | formed in view of the above, Comprising: It aims at providing the optical film roll which can suppress generation | occurrence | production of a band, a texture transfer, and bubble biting, and is excellent in storage stability, and its manufacturing method.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have rolled a multilayer film obtained by laminating an optical film containing an alicyclic structure-containing polymer and a protective film peelable from the optical film. In the rolled optical film roll, by appropriately setting the arithmetic average roughness Ra of the surface opposite to the optical film of the protective film and the average interval Sm of the irregularities, band, wrinkle transfer and bubble biting are generated. The present invention has been completed by finding that an optical film roll that can be suppressed and excellent in storage stability can be realized.
That is, the gist of the present invention is the following [1] to [6].

（ただし、式（１）の積分は、ｓｉｎカーブ１周期分について行う。）
〔３〕 前記保護フィルムがポリオレフィン系重合体を含む、〔１〕又は〔２〕に記載の光学フィルムロール。
〔４〕 前記光学フィルムの前記保護フィルムとは反対側の面の静摩擦係数が０．７以上である、〔１〕〜〔３〕のいずれか一項に記載の光学フィルムロール。
〔５〕 前記光学フィルムの前記保護フィルムとは反対側の面の算術平均粗さＲａが０．０５μｍ以下である、〔１〕〜〔４〕のいずれか一項に記載の光学フィルムロール。
〔６〕 脂環式構造含有重合体を溶融押し出しして光学フィルムを得る工程、
該光学フィルムから剥離可能な保護フィルムを該光学フィルムと貼り合わせて複層フィルムを得る工程、
該複層フィルムをロール状に巻回する工程、を含む光学フィルムロールの製造方法であって、
前記保護フィルムの前記光学フィルムとは反対側の面の、算術平均粗さＲａが０．２μｍ以上０．５μｍ以下であり、かつ、凹凸の平均間隔Ｓｍが２００μｍ以上５００μｍ以下である、光学フィルムロールの製造方法。 [1] An optical film roll formed by winding a multilayer film obtained by laminating an optical film containing an alicyclic structure-containing polymer and a protective film peelable from the optical film into a roll,
An optical film roll having an arithmetic average roughness Ra of 0.2 μm or more and 0.5 μm or less and an average interval Sm of 200 μm or more and 500 μm or less of the surface of the protective film opposite to the optical film. .
[2] The optical film according to [1], wherein the arithmetic average roughness Ra and the average interval Sm of the irregularities on the surface of the protective film opposite to the optical film satisfy the relationship of the following formula (1): roll.

(However, the integration of equation (1) is performed for one cycle of the sin curve.)
[3] The optical film roll according to [1] or [2], wherein the protective film contains a polyolefin polymer.
[4] The optical film roll according to any one of [1] to [3], wherein a static friction coefficient of a surface of the optical film opposite to the protective film is 0.7 or more.
[5] The optical film roll according to any one of [1] to [4], wherein an arithmetic average roughness Ra of the surface of the optical film opposite to the protective film is 0.05 μm or less.
[6] A step of melt-extruding the alicyclic structure-containing polymer to obtain an optical film,
A step of bonding a protective film peelable from the optical film to the optical film to obtain a multilayer film;
A step of winding the multilayer film into a roll, and a method for producing an optical film roll,
An optical film roll having an arithmetic average roughness Ra of 0.2 μm or more and 0.5 μm or less and an average interval Sm of 200 μm or more and 500 μm or less of the surface of the protective film opposite to the optical film. Manufacturing method.

The optical film roll of the present invention can suppress the occurrence of band, texture transfer and bubble biting, and is excellent in storage stability.
According to the method for producing an optical film roll of the present invention, it is possible to produce an optical film roll that can suppress generation of band, texture transfer and bubble biting, and is excellent in storage stability.

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 illustrating an example of a configuration in which a multilayer film is wound in a roll shape. FIG. 3 is a diagram schematically showing a state in which the outermost multilayer film is cut by a plane parallel to the axial direction and the radial direction of the optical film roll in the optical film roll in the middle of winding the multilayer film. It is. FIG. 4 shows a multilayer film in an optical film roll according to an embodiment of the present invention, in which the wound inner and outer multilayer films are cut along a plane parallel to the circumferential direction and the radial direction of the optical film roll. FIG. FIG. 5 is a diagram for explaining the area represented by the left side of Equation (1). FIG. 6 schematically shows a state in which the optical film and the protective film are cut by a plane parallel to the width direction and the thickness direction of the multilayer film in a configuration in which the optical film and the protective film are bonded between a pair of bonding rolls. FIG.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the following embodiments and examples, and departs from the gist of the present invention and its equivalent scope. Any change can be made without departing from the scope.

[1. Overview]
FIG. 1 is a diagram schematically showing an optical film roll according to an embodiment of the present invention. As shown in FIG. 1, the optical film roll 100 is a roll formed by winding a multilayer film 30 in which an optical film 10 and a protective film 20 that can be peeled off from the optical film 10 are bonded together into a roll shape. In this optical film roll 100, band or wrinkle transfer is performed by providing irregularities that satisfy a predetermined condition on the surface 20U of the protective film 20 opposite to the optical film 10 (hereinafter referred to as “rough surface” as appropriate). In addition, suppression of foam biting and improvement in storage stability are realized.

[2. Optical film]
A long optical film is used as the optical 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. In the case of a long film, the long direction of the film usually coincides with the MD direction, and the width direction of the film coincides with the TD direction.

  The optical film includes an alicyclic structure-containing polymer. Usually, an optical film containing an alicyclic structure-containing polymer has low slipperiness, so stress concentration easily occurs when it is attached to a protective film and when the film is wound, and stress is relieved because of its low elastic modulus. Since it is difficult, there is a tendency to easily cause deformation and the like. Even if the optical film roll of the present invention is an optical film containing an alicyclic structure-containing polymer that easily undergoes deformation or the like, it is possible to suppress the occurrence of band, texture transfer and bubble biting, and excellent storage stability. Significant in terms.

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 proportion 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, but is usually 50% by weight or more, preferably 70% by weight or more, more preferably. Is 90% by weight or more. When the ratio of the repeating unit having an alicyclic structure is excessively small, the heat resistance may be lowered. In addition, repeating units other than the repeating unit which has an alicyclic structure in an alicyclic structure containing polymer are suitably selected according to the intended purpose of the optical film.

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.
In addition, an alicyclic structure containing polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Moreover, the optical film may contain components other than an alicyclic structure containing polymer, unless the effect of this invention is impaired remarkably. 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 contained in the optical film is within a range that does not impair the effects of the present invention, and is usually 50 parts by weight or less with respect to 100 parts by weight of the alicyclic structure-containing polymer. The amount is preferably 30 parts by weight or less. The lower limit is zero.

  Further, the optical film may be a single-layer film having only one layer, or may be a multilayer film having two or more layers. At this time, if the optical film has a single-layer structure, the layer only needs to contain an alicyclic structure-containing polymer. Further, if the optical film has a multilayer structure, it is sufficient that at least one layer contains an alicyclic structure-containing polymer, and the layer that forms the surface opposite to the protective film has an alicyclic structure-containing weight. It is preferable to include coalescence. However, it is preferable to use an optical film having a single layer structure.

  The static friction coefficient of the surface of the optical film opposite to the protective film is usually 0.7 or more, preferably 0.8 or more, more preferably 0.9 or more. In the optical film roll of the present invention, even when the optical film is hard to slip due to such a high coefficient of static friction, the protective film exhibits an appropriate sliding property, so that the optical film is damaged when wound into a roll. Can be suppressed. The upper limit of the static friction coefficient is usually 3.0 or less, preferably 2.0 or less. In general, the surface of the optical film on the protective film side also has a static friction coefficient in the same range as the surface on the side opposite to the protective film.

  The static friction coefficient of the surface of the optical film is as follows. Test speed: 150 mm / min, test load: 200 g (load with rubber), slip surface: film to metal (chrome) (Plating iron plate), test direction: MD direction, test temperature: 23 ° C., number of tests: 5 times.

  The arithmetic average roughness Ra of the surface of the optical film opposite to the protective film is usually 0.05 μm or less, preferably 0.03 μm or less, more preferably 0.01 μm or less. Thus, an optical film having a highly smooth surface is excellent in optical characteristics, but if the high smoothness is impaired, the optical characteristics may also change. However, the optical film roll of the present invention can suppress the occurrence of band, wrinkle transfer and bubble biting even if the optical film is easily deformed, and is excellent in storage stability, so that the high smoothness of the optical film can be maintained over a long period of time. . The lower limit of the arithmetic average roughness Ra is ideally zero. In general, the surface on the protective film side of the optical film also has an arithmetic average roughness Ra in the same range as the surface on the side opposite to the protective film.

  The arithmetic average roughness Ra of the surface of the optical film may be measured by using “New View 5000” manufactured by Zygo Corp. with an objective lens of 10 times and a measurement area of 358 μm × 268 μm.

  The tensile elastic modulus in the MD direction of the optical film is usually 1000 MPa or more, preferably 1500 MPa or more, more preferably 2000 MPa or more, usually 4000 MPa or less, preferably 3500 MPa or less, more preferably 3000 MPa or less. An optical film having a tensile modulus in the above range can be easily produced by melt extrusion.

  The tensile modulus was “Tensilon UTM-10T-PL” manufactured by Toyo Baldwien, tensile speed: 500 mm / min, load: load cell 50 kgf, sample shape: width 10 mm × length 50 mm, number of tests: 5 It is sufficient to measure in a single time.

  The thickness of the optical film is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less. Thus, the thin optical film is soft and easily deformed. However, in the optical film roll of the present invention, even if the optical film is easily deformed, band, wrinkle transfer and bubble biting are generated. It is significant in that it can be suppressed and has excellent storage stability.

  The optical film may be a stretched film or an unstretched film. The presence or absence of stretching may be determined according to the use of the optical film, but the thickness of the optical film is preferably a stretched film from the viewpoint that it becomes thinner by stretching.

  The optical film usually has high transparency. Specifically, the total light transmittance of the optical film is preferably 85% or more, more preferably 90% or more. The upper limit is ideally 100%. Here, the total light transmittance may be measured according to JIS K7361-1997.

  The optical film usually has a small haze, depending on the application. Specifically, the haze of the optical film 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, the haze may be measured according to JIS K7361-1997.

  There is no restriction | limiting in particular in the manufacturing method of an optical film, For example, either a melt molding method or a solution casting method can be used. The melt molding method can be further classified into an extrusion molding method, 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 an optical film excellent in mechanical strength, surface accuracy, etc., an extrusion molding method, an inflation molding method, or a press molding method is preferable, and in particular, efficiency while suppressing the development of retardation more reliably. The extrusion method is particularly preferred from the viewpoint that an optical film can be produced easily and easily.

  Further, when an optical film is produced as a laminated film, for example, a coextrusion molding method such as a coextrusion T-die method, a coextrusion inflation method, a coextrusion lamination method, etc .; a film lamination molding method such as dry lamination; Known methods such as a coating molding method for coating the resin solution constituting the other layers can be appropriately used. Among them, the coextrusion molding method is preferable from the viewpoint of good production efficiency and preventing volatile components such as a solvent from remaining in the optical film. Among the coextrusion molding methods, the coextrusion T-die method is preferable. Further, examples of the coextrusion T-die method include a feed block method and a multi-manifold method, but the multi-manifold method is more preferable in that variation in layer thickness can be reduced.

  Furthermore, in the manufacturing method of an optical film, you may make it perform the extending | stretching process etc. which extend | stretch an optical film as needed.

[3. Protective film]
The protective film is a long film that is bonded to the optical film in order to protect the optical film. Usually, a protective film is bonded together directly on the surface of an optical film, without passing through other layers, such as an adhesive layer.

The rough surface of the protective film opposite to the optical film is a surface having irregularities so as to have a predetermined arithmetic average roughness Ra and an average interval Sm of the irregularities. Specifically, the arithmetic average roughness Ra of the rough surface of the protective film opposite to the optical film is usually 0.2 μm or more and usually 0.5 μm or less. Moreover, the average interval Sm of the unevenness of the rough surface on the side opposite to the optical film of the protective film is usually 200 μm or more and usually 500 μm or less.
Note that “arithmetic average roughness Ra” and “average unevenness interval Sm” are indices representing the surface roughness defined in JIS B0601-1994. The arithmetic average roughness Ra of the rough surface opposite to the optical film of the protective film and the average interval Sm of the irregularities are measured using a “DEKTAK 6M stylus type surface shape measuring instrument” manufactured by ULVAC, measuring length: 10 mm, What is necessary is just to measure at the tip radius of the stylus: 2.5 μm and the load of the stylus: 10 mg.

The significance of the surface roughness of the rough surface opposite to the optical film of the protective film will be described below with reference to the drawings.
FIG. 2 is a diagram schematically illustrating an example of a configuration in which the multilayer film 30 is wound in a roll shape. 3 shows an optical film roll 100 in the middle of winding the multilayer film 30 as shown in FIG. 2, and the outermost multilayer film 30 is separated from the axial direction X and the radial direction Z of the optical film roll 100. It is a figure which shows typically a mode that it cut | disconnected by the plane parallel to this. The axial direction X of the optical film roll 100 coincides with the width direction of the multilayer film 30, and the radial direction Z of the optical film coincides with the thickness direction of the multilayer film 30.

  As shown in FIG. 2, the optical film roll 100 is normally manufactured by winding the multilayer film 30 around the winding core 40 in a roll shape. When winding the multilayer film 30, the wound multilayer film 30 and the outer peripheral surface of the optical film roll 100 are wound in a portion II where the wound multilayer film 30 contacts the outer peripheral surface 110 of the optical film roll 100. The air A1 may enter between 110 and 110. The infiltrated air A1 normally forms an air layer (not shown) between the multilayer film 30 and the outer peripheral surface 110 of the optical film roll 100, but the amount of the infiltrated air A1 is small as described above. Therefore, the air layer has a small thickness, and the infiltrated air A1 is quickly discharged to the outside of the optical film roll 100.

  However, in the conventional technique, the air A1 is not discharged for some reason, and the air 120 may remain between the multilayer film 30 and the outer peripheral surface 110 of the optical film roll 100 as shown in FIG. . In the portion 130 where the air 120 remains, the outer diameter of the optical film roll 100 is partially increased. Accordingly, when the winding of the multilayer film 30 is continued with the air 120 remaining, the portion 130 where the air 120 remains is raised, and a band is formed on the optical film roll 100.

  On the other hand, in the optical film roll 100 of the present invention, as shown in FIG. 4, for example, air 120 (not shown in FIG. 4) does not remain. Here, FIG. 4 shows the inner and outer multilayer films wound out of the multilayer film 30 in the optical film roll 100 according to an embodiment of the present invention, the circumferential direction Y and the diameter of the optical film roll 100. 3 is a diagram schematically showing a cross section cut by a plane parallel to the direction Z. FIG. In FIG. 4, the inner multilayer film is indicated by reference numeral “31”, and the outer multilayer film is indicated by reference numeral “32”. Further, the optical film of the inner multilayer film 31 is denoted by “11”, the protective film of the inner multilayer film 31 is denoted by “21”, the optical film of the outer multilayer film 32 is denoted by “12”, and the outer multilayer film 31 is denoted by “12”. The protective film of the layer film 32 is indicated by “22”. Further, the circumferential direction Y of the optical film roll 100 coincides with the longitudinal direction of the multilayer films 31 and 32.

  As shown in FIG. 4, in the optical film roll 100, when the multilayer films 31 and 32 are wound, the multilayer films 31 and 32 are wound over many layers. At this time, when paying attention to a certain multilayer film 31 and the multilayer film 32 on the outermost layer, the outer surface of the inner multilayer film 31 and the inner surface of the outer multilayer film 32 are in contact with each other. become. In the example of FIG. 4, the multilayer films 31 and 32 are wound with the optical films 11 and 12 inside, so that the protective film 21 of the inner multilayer film 31 on the side opposite to the optical film 11 is rough. The surface 21U becomes the outer surface of the inner multilayer film 31, and the surface 12D opposite to the protective film 22 of the optical film 12 of the outer multilayer film 32 becomes the inner surface of the outer multilayer film 32. For this reason, in the following description, the rough surface on the opposite side to the optical film 11 of the protective film 21 of the inner multilayer film 31 and the outer surface of the inner multilayer film 31 are denoted by a common symbol “21U”. The surface opposite to the protective film 22 of the optical film 12 of the outer multilayer film 32 and the inner surface of the outer multilayer film 32 are denoted by a common reference numeral “12D”.

  In the present invention, since the uneven surface 21U is formed on the rough surface 21U of the protective film 21 so as to have the surface roughness described above, the outer surface 21U of the inner multilayer film 31 has the uneven surface 21X. It has a concave portion 21A and a convex portion 21B according to the above. Therefore, between the inner multilayer film 31 and the outer multilayer film 32, a void 50 surrounded by the concave portion 21A and the convex portion 21B of the rough surface 21U of the protective film 21 and the surface 12D of the optical film 12 is formed. Is done. This air gap 50 is because air that has entered between the inner multilayer film 31 and the outer multilayer film 32 escapes in the axial direction X of the optical film roll 100 (that is, the width direction of the multilayer films 31, 32). It functions as a flow path. Therefore, if the multilayer film 31 has a large cross-sectional size obtained by cutting the gap 50 in a plane parallel to the longitudinal direction Y and the thickness direction Z, air is easily discharged through the gap 50. A conventional band caused by the residual air 120 can be prevented.

  As can be seen from the definitions of the arithmetic average roughness Ra and the average interval Sm between the irregularities, the arithmetic average roughness Ra of the rough surface 21U of the protective film 21 corresponds to the average value of the height of the cross section of the void 50, and The average interval Sm of the unevenness corresponds to the width of the cross section of the gap 50. Therefore, in order to set the arithmetic average roughness Ra to 0.2 μm or more, and to set the average interval Sm of the unevenness to 200 μm or more, the cross-sectional area of the gap 50 is sufficiently increased, Therefore, it is technically significant in that the air can be quickly discharged and the generation of the band due to the air 120 can be prevented.

  In this regard, the present inventor studied the size of the desired cross-sectional area of the gap 50 from the viewpoint of quickly discharging the air 120 and preventing the band as described above. Specifically, as shown in FIG. 1, the roughness curve of the multilayer film 30 is measured for the rough surface 20U of the protective film 20, and the average cross-sectional area of the void 50 (see FIG. 4) is determined from the roughness curve. Asked. Further, as described above, the arithmetic average roughness Ra of the rough surface 20U of the protective film 20 correlates with the height of the cross section of the gap 50, and the average interval Sm of the irregularities correlates with the width of the cross section of the gap 50. Using this, an attempt was made to express the average cross-sectional area of the void 50 using the arithmetic average roughness Ra of the rough surface 20U and the average interval Sm of the irregularities. Furthermore, it was examined how large the average cross-sectional area of the air gap 50 can prevent the generation of the band.

As a result of the above investigation, when the roughness curve of the rough surface 20U is approximated by a sin curve, the average value of the cross-sectional area of the gap 50 is obtained from the left side of the following equation (1), and the equation (1) It has been found that when the average value of the cross-sectional area of the void 50 obtained from the left side is 50 μm ² or more, the generation of bands due to the residual air 120 (see FIG. 3) can be prevented. Therefore, it is preferable that the arithmetic average roughness Ra of the rough surface 20U of the protective film 20 and the average interval Sm of the unevenness satisfy the relationship of the formula (1).

  However, in Formula (1), x represents the position on the rough surface 20U in the measurement direction of arithmetic mean roughness Ra and the average space | interval Sm of unevenness | corrugation, The integral of the left side of Formula (1) is a sin curve 1 period. Do about.

  FIG. 5 is a diagram for explaining the area represented by the left side of Equation (1). The function integrated on the left side of Equation (1) corresponds to the function represented by the sine curve shown in FIG. 5, and the area represented on the left side of Equation (1) corresponds to the area of the portion represented by diagonal lines in FIG. Moreover, in the function integrated by the left side of Formula (1), the 1st term is a function calculated | required from the roughness curve of the rough surface 20U of the protective film 20, Comprising: The roughness curve of the rough surface 20U of the protective film 20 Is an approximate function. Furthermore, the second term is a term for correcting the calculated value so that it does not become zero due to the nature of the sine function when calculating the area of one cycle of the sin curve. In the example of FIG. This is a term for moving the curve upward by one amplitude.

  Here, the coefficients of “1.575” and “6.3” on the left side of the formula (1) are coefficients obtained by repeating the experiment by the present inventor. That is, a curve obtained by synthesizing a plurality of sin curves can be drawn by performing frequency analysis (Fourier transform) on the roughness curve of the rough surface 20U. The frequency analysis can be performed using “Microsoft Excel” manufactured by Microsoft Corporation. By approximating a curve obtained by synthesizing the plurality of sin curves to one sin curve using the arithmetic average roughness Ra and the average interval Sm of the unevenness, the left side of the equation (1) can be derived. These coefficients are highly reliable because they have consistency with the results in many examples and comparative examples described later.

  When the average interval Sm of the unevenness of the rough surface 20U of the protective film 20 exceeds 500 μm, the distance between adjacent concave portions or convex portions on the rough surface 20U of the protective film 20 becomes too large, and thus the protective film 20 and the multilayer film There is a possibility that meandering occurs during the conveyance of 30 and the appearance of the optical film roll 100 is impaired. For this reason, the upper limit of 500 μm or less is usually provided in the average interval Sm of the unevenness of the rough surface 20U of the protective film 20.

  Further, as shown in FIG. 4, the arithmetic average roughness Ra of the rough surface 21U of the protective film 21 increases, the height of the convex portion 21B of the rough surface 21U of the protective film 21 increases, and the tip of the convex portion 21B. Tends to have a sharper shape. When the tip of the convex portion 21B is sharp, due to stress concentration, the shape of the convex portion 21B is likely to be transferred to the surface 12D of the optical film 12 facing the surface, and a texture transfer is likely to occur. For this reason, the arithmetic average roughness Ra of the rough surface 21U of the protective film 21 is preferably small enough to prevent the transfer, and specifically, the arithmetic average roughness Ra is preferably 0.5 μm or less. .

  Furthermore, from the viewpoint of preventing the texture transfer, it is preferable that the average interval Sm of the unevenness of the rough surface 21U of the protective film 21 is large. If the average interval Sm between the concave and convex portions of the rough surface 21U of the protective film 21 is large, the sharpness of the tip of the convex portion 21B becomes gentle, so that the shape transfer of the convex portion 21B to the surface 12D of the optical film 12 can be prevented. is there. When the arithmetic average roughness Ra of the rough surface 21U of the protective film 21 is in the above-mentioned range, since the uneven transfer can be sufficiently prevented if the average interval Sm of the unevenness is 200 μm or more, the average interval Sm of the unevenness is Also, there is a technical significance in that shape transfer (that is, texture transfer) of the unevenness 21X of the protective film 21 to the optical film can be prevented.

  In FIG. 4, the configuration of the optical film roll 100 in which the multilayer films 31 and 32 are wound with the optical films 11 and 12 on the inner side is illustrated and described, but conversely, the protective films 21 and 22 are on the inner side. Similarly, in the optical film roll 100 around which the multilayer films 31 and 32 are wound, it is possible to prevent band and wrinkle transfer.

  6 shows a configuration in which the optical film 10 and the protective film 20 are bonded between the pair of bonding rolls 61 and 62, and the optical film 10 and the protective film 20 are parallel to the width direction X and the thickness direction Z of the multilayer film 30. It is a figure which shows typically a mode that it cut | disconnected by the flat plane. As shown in FIG. 6, the optical film 10 and the protective film 20 are usually sandwiched and bonded between a pair of opposing laminating rolls 61 and 62. At this time, when the unevenness 20X is formed on the rough surface 20U on the opposite side of the protective film 20 from the optical film 10, in general, the pressing force applied from the bonding roll 61 to the protective film 20 is the recess 20A. It becomes smaller as indicated by the arrow A2, and becomes larger as indicated by the arrow A3 at the convex portion 20B.

  Here, when the arithmetic average roughness Ra of the rough surface 20U of the protective film 20 is too large, the difference in height between the concave portions 20A and the convex portions 20B of the concave and convex portions 20X formed on the rough surface 20U increases, and accordingly. Thus, the difference between the pressure applied from the bonding roll 61 to the concave portion 20A of the protective film 20 and the pressure applied to the convex portion 20B also increases. For this reason, in the boundary surface 20D where the optical film 10 and the protective film 20 are bonded together, the air 120 may be sandwiched between the back side (optical film 10 side) of the recess 20A of the protective film 20 and bubble biting may occur. . Since the pressure applied to the back side portion of the recess 20A of the protective film 20 is relatively smaller than the surroundings, the surrounding air 120 concentrates on the portion where the pressure is low, and the optical film 10 and the protective film 20 It is presumed that it was caused by remaining in between. Therefore, from the viewpoint of suppressing the above-mentioned bubble biting, the arithmetic average of the rough surface 20U of the protective film 20 is reduced so that the difference in pressure applied from the laminating roll 61 to the concave portions 20A and the convex portions 20B of the concave and convex portions 20X is reduced. It is preferable to reduce the roughness Ra. Specifically, the roughness Ra is usually 0.5 μm or less, preferably 0.4 μm or less. Furthermore, since the difference in pressure applied from the laminating roll 61 to the recesses 20A and the protrusions 20B decreases as the average interval Sm of the unevenness of the rough surface 20U of the protective film 20 increases, the average interval Sm of the unevenness is Preferably it is 250 micrometers or more, More preferably, it is 300 micrometers or more.

  Conventionally, in order to control the slipperiness of the protective film, a technique for adjusting the arithmetic average roughness Ra of the surface of the protective film has been known, but a technique for adjusting the average interval Sm of the unevenness has not been known. . In addition, the arithmetic average roughness Ra and the average interval Sm between the concaves and convexes are common in that they are index values of the surface roughness, but they are independent of each other. For example, the larger the arithmetic average roughness Ra is, the larger the arithmetic average roughness Ra is. There is no circumstance that the average interval Sm of the unevenness is large or small. For this reason, when controlling the surface roughness of the rough surface on the side opposite to the optical film of the protective film as in the present invention, the arithmetic average roughness Ra and the average interval Sm of the unevenness are combined to make the range of characteristics. Therefore, suppressing band, wrinkle transfer and bubble biting has a significant significance different from that of the prior art.

  Furthermore, by setting the surface roughness Ra of the rough surface opposite to the optical film of the protective film and the average interval Sm of the unevenness to the above ranges, the multilayer film is displaced during storage, and the end face deviation occurs in the optical film roll. In addition, since the roll shape can be prevented from being deformed over time, the storage stability can be improved.

  Moreover, if the surface roughness of the rough surface on the opposite side to the optical film of a protective film is made into the said range, the slipperiness of a protective film and a multilayer film can be improved, and handleability can also be improved. Moreover, the winding gap | deviation resulting from the entrainment of the air at the time of winding a protective film and a multilayer film can be prevented. Furthermore, according to the rough surface, even if foreign matter such as dust adheres to the rough surface or foreign matter is mixed inside the protective film or inside the optical film, the foreign matter is contained in the concave portion of the rough surface. It is possible to prevent the shape of the foreign matter from being transferred to the surface.

  Further, the protective film is usually wound and stored and transported as a roll, and is used by being pulled out from the roll at the time of use. At this time, when the protective film has the rough surface, the protective film can be easily pulled out from the roll. This is because the adhesive layer (described later) of the protective film and the rough surface are difficult to adhere due to the rough surface.

  In order to control the arithmetic average roughness Ra of the surface opposite to the optical film of the protective film and the average interval Sm of the irregularities as described above, for example, the arithmetic average roughness Ra and the irregularities of the surface of the shaping roll What is necessary is just to adjust average space | interval Sm corresponding to the surface roughness of the protective film which is going to form.

  The degree of ease of peeling between the optical film and the protective film may be set arbitrarily, but the peeling force between the optical film and the protective film is usually 0.0025 N / cm or more, and usually 0.25 N / cm. Hereinafter, it is preferably 0.010 N / cm or less. Although it is preferable that peeling is easy, if peeling can be performed too easily, peeling may occur when the multilayer film is wound and pulled. In addition, the adhesive force between the optical film and the protective film is usually affected by the surface roughness of the optical film, and the adhesion strength generally decreases as the surface roughness of the optical film increases.

The thickness of the protective film varies depending on the thickness of the optical film and the required quality level of the optical film, but is usually 20 μm or more and usually 100 μm or less from the viewpoint of moldability and handling properties.
The length and width of the protective film are usually the same as those of the optical film.

  The composition and layer structure of the protective film are arbitrary as long as the effects of the present invention are not significantly impaired. However, the protective film preferably contains a polyolefin-based polymer. Further, the protective film may be a single-layer structure film having only one layer, or may be a multilayer film having two or more layers. Under the present circumstances, if a protective film is a film of a single layer structure, it is preferable that the said layer contains a polyolefin-type polymer. In addition, if the protective film has a multilayer structure, at least one layer preferably contains a polyolefin polymer. By using a polyolefin-based polymer, molding by coextrusion becomes possible, and productivity is excellent.

  The protective film is usually a film having a multilayer structure including two or more layers. When the suitable example of a protective film 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 etc. are mentioned. Hereinafter, suitable examples of the protective film will be described.

-Adhesion layer An adhesion layer is a layer which is located in the optical film side surface of a protective film, and adheres to an optical film. The pressure-sensitive adhesive layer is formed to contain a pressure-sensitive adhesive, and the protective film is fixed to the optical film 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 ABA or the general formula AB, 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 point. 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 point of −20 ° C. or lower is preferable. 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, Styrene, acrylonitrile, vinyl pyridine, vinyl pyrrolidone, vinyl alkyl ethers, and the like homopolymers or copolymers and the like. 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 crosslinking agent, adhesion between the adhesive layer and other layers (intermediate layer, back layer, etc.) in contact with the protective film, toughness of the protective film, solvent resistance, water resistance, etc. can be improved. . 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. It can be used as appropriate. 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 aromatic isocyanate compounds 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 type of tackifying polymer is appropriately selected from the viewpoint of the compatibility with the block copolymer, 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. . If the amount of the tackifying polymer is too small, the protective film may be lifted or peeled off when it is bonded to the optical film. If the amount is too large, the feeding tension increases and the optical film is bonded. In this case, wrinkles and scratches may occur, or bleed-out of the tackifying polymer may occur and the adhesive force may be easily reduced.

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, and 6 N / cm or less with respect to other layers (intermediate layer, back layer, etc.) in contact with the protective film. Preferably, 4 N / cm or less is more preferable. If the adhesive strength is too low, the protective film may be lifted or peeled off when bonded to the optical film. If the adhesive strength is too high, the feeding tension will increase and the wrinkle will be reduced when bonding to the optical film. Or scratches may occur.

  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. If the pressure-sensitive adhesive layer is too thin, the pressure-sensitive adhesive force is lowered and the protective film may be lifted or peeled off. On the other hand, if the adhesive layer is too thick, the adhesive force becomes excessively high and the feeding tension increases, which may cause wrinkles and scratches when bonded to the optical film. In addition, the stiffness of the protective film may become strong and handling properties may deteriorate.

Back layer The back layer is a layer that is located on the opposite side of the adhesive layer from the optical film and is usually located on the opposite side of the protective film from the optical film, and does not adhere to the optical film. is there. Usually, a rough surface is formed on the exposed surface of the back layer.

  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 polymer is a chain olefin homopolymer or copolymer, or a copolymer of a chain olefin and a monomer copolymerizable therewith. 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. Polymers (hereinafter collectively referred to as “propylene copolymers”) are more preferable, and ethylene-propylene copolymers are particularly preferable.

  Although the polymer mentioned above may be used individually by 1 type, you may use it combining 2 or more types by arbitrary ratios. 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 referred to as “MFR” where appropriate) at 230 ° C. of the propylene 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 . If the density of the low density polyethylene is too high, the resin may be detached from the protective film due to rubbing with a roll (for example, a metal roll, a rubber roll, etc.) used for conveyance, which may cause generation of white powder. Moreover, when the density of the low density polyethylene is too low, it may be difficult to make the surface of the back layer rough.

  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 addition, the resin forming the back layer may be, for example, a filler such as talc, stearamide, and calcium stearate, a lubricant, an antioxidant, an ultraviolet absorber, a pigment, and an antistatic material, as long as the effects of the present invention are not significantly impaired. You may include additives, such as an agent and a nucleating agent. 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. If the thickness of the back layer is too small compared to the adhesive layer, the film formability may deteriorate and a lot of fish eyes may be generated. If it is too thick, the feeding tension will increase and the protective film will be bonded to the optical film. Wrinkles and scratches are likely to occur.

-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. Normally, when a protective film is produced by a coextrusion molding method, the non-uniform thickness at the end is slit and removed by a slitting process, etc., but the removed portion is used as a raw material for the intermediate layer. As a result, the amount of raw materials 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 thickness of the intermediate layer is usually 13 μm to 70 μm.

-Manufacturing method of a protective film There is no restriction | limiting in the manufacturing method of a protective film, As long as the protective film mentioned above is obtained, arbitrary methods are employable. Examples of methods for producing protective films are: (i) a method for coextruding the material for the adhesive layer and the material for the back layer, and the material for the intermediate layer, if necessary, and (ii) preparing the back layer or the intermediate layer. And a method of forming an adhesive layer by applying an adhesive to the prepared layer. Alternatively, (iii) a pressure-sensitive adhesive layer and a back layer, and an intermediate layer may be separately prepared as necessary, and the prepared layers may be bonded and integrated.

  Among the exemplified production methods, in the production method (i) by the coextrusion molding method, the adhesive layer and the back layer or the intermediate layer are firmly adhered, and the adhesive residue on the optical film (the optical film after the protective film is peeled off) This is particularly preferable because it has the advantage that the phenomenon that the adhesive remains) is less likely to occur and the manufacturing process is simplified and the cost is low. In the protective film 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, vinyl acetate, linear low density polyethylene, metallocene linear low density polyethylene and the like are usually used for the adhesive layer. 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.

  Further, in the protective film produced by the production method (ii) by the coating method, polyethylene terephthalate and polyolefin polymer are usually used as the back layer, and rubber adhesive and acrylic adhesive are usually used for the adhesive layer. Is often used. Among these, when there is a concern about foreign matters in the protective film, it is preferable to use polyethylene terephthalate for the back layer rather than the polyolefin polymer. In the production method (ii), a high-quality protective film free from foreign matters can be obtained when produced in a clean room.

In order to form the rough surface having the above-described surface roughness on the protective film, for example, by deforming the surface of the back layer, the unevenness having a predetermined surface roughness is formed on the side opposite to the optical film of the protective layer. It may be formed on the surface. For example, a nip forming method in which an unevenness-imparting roll is used to press the protective film immediately after extrusion obtained in the coextrusion molding method to transfer the unevenness to the surface of the back layer; A method of transferring the unevenness of the release film by clamping with a mold film, and then peeling the release film; a method of cutting the surface of the back layer of the protective film by spraying fine particles on the surface of the back layer of the protective film, etc. Is mentioned. 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, irregularities can be formed on the surface of the back layer by adjusting the composition of the back 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 a protective film without uneven transfer unevenness can be obtained with a wide width, a nip forming method using an uneven forming roll is preferred, and a protective film using a mirror roll and an uneven forming roll The method of pinching is particularly preferable.
Examples of the surface material of each mirror roll and shaping roll include metal, rubber, and resin. These are appropriately selected so that the desired uneven shape can be transferred to the surface of the back layer of the protective film. However, the hardness of the shaping roll is preferably not less than the hardness of the mirror roll. Further, for example, the protective film may be narrowed through 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. When the temperature of the mirror surface roll or the shaping roll exceeds the upper limit temperature in the above range, the protective film may be wound around the mirror surface roll or the shaping roll. Moreover, when the temperature of a mirror surface roll or a shaping roll is less than the minimum temperature of the said range, there exists a tendency for uneven | corrugated transfer unevenness to arise on the surface of the back surface layer of a protective film.

  In the nip forming method, the roughness of the rough surface of the protective film is the temperature of the protective film, the mirror roll and the shaping roll at the time of clamping, the roll speed, the pressure at which the protective film is clamped, and the mirror roll and the shaping roll. The material of the surface can be adjusted by selecting appropriately according to the characteristics of the material forming the protective film. 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.

  For example, in the case of a protective film including a back layer formed of an acrylic resin, a preferable pressure is 5 kN / m to 13 kN / m. If the pressure applied to the protective film exceeds the upper limit of the above range, the protective film may be broken. If the pressure applied to the protective film is below the lower limit of the above range, uneven transfer unevenness tends to occur in the width direction of the protective film.

  The roll speed of the mirror surface roll and the shaping roll is preferably 20 m / min or less. If the roll speed is higher than this, uneven transfer unevenness tends to occur on the rough surface of the protective film.

The rough surface of the protective film may be subjected to surface modification treatment as necessary. Examples of the surface modification treatment include energy beam irradiation treatment and chemical treatment.
Moreover, you may print on the rough surface of a protective film as needed.

[4. Multi-layer film]
The multilayer film is a long film in which the above-described long optical film and a long protective film are bonded together. In this multilayer film, since it is sufficient that a protective film is provided on at least one side of the optical film, the protective film may be provided on both sides of the optical film. However, a protective film is usually bonded to one side of the optical film.
The multilayer film may be a multilayer film including a total of three or more layers having two or more of one or both of the optical film and the protective film. However, the multilayer film is usually a multilayer film having a total of two layers each having one optical film and one protective film.

  The multilayer film may have other layers in addition to the optical film and the protective film as long as the effects of the present invention are not significantly impaired. The other layers may be one layer or two or more layers. Moreover, each layer may be the same or different. The positions of other layers can be set arbitrarily. However, normally, a multilayer film has only an optical film and a protective film.

  Although there is no restriction | limiting in the manufacturing method of a multilayer film, Usually, the optical film and protective film which were prepared separately are bonded together and a multilayer film is manufactured. At the time of bonding, in order to eliminate wrinkles and slack of the optical film and the protective film, the bonding is performed while applying a predetermined tension to the optical film and the protective film.

[5. Optical film roll]
The optical film roll of the present invention is obtained by winding the long multilayer film in a roll shape.
In the optical film roll, since the surface of the protective film opposite to the optical film is a rough surface having the predetermined surface roughness as described above, the generation of band, wrinkle transfer and bubble biting can be suppressed and stored. Excellent stability.

Although there is no restriction | limiting in the frequency | count of winding of an optical film roll, Usually, 40 times or more, Preferably it is 60 times or more, Usually, 27000 times or less, Preferably it is 13000 times or less.
Moreover, there is no restriction | limiting in the outer diameter of an optical film roll, However, 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.

The optical film roll of the present invention includes, for example, at least a step of melt-extruding an alicyclic structure-containing polymer to obtain an optical film, and a protective film peelable from the optical film is bonded to the optical film to form a multilayer film It can manufacture by performing the process of obtaining, and the process of winding a multilayer film in roll shape. At this time, an appropriate winding core may be used when winding.
The winding speed is not limited. However, if the winding speed is too fast, air is likely to be trapped, and if the winding speed is too slow, the production efficiency is lowered. Therefore, it is usually 5 m / min or more, preferably 10 m. / Min., Usually 150 m / min or less, preferably 100 m / min or less, more preferably 80 m / min or less.

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

[Evaluation methods]
[Evaluation of roll appearance]
The film roll immediately after winding was evaluated visually and by palpation. “A” indicates that there is no unevenness such as a band by visual inspection and palpation, “B” indicates that there is no unevenness by visual inspection but there is unevenness by palpation, and “C” indicates that there is unevenness both by visual inspection and palpation.

[Evaluation of storage stability]
The sample was allowed to stand at a temperature of 10 ° C. and a humidity of 80% for 24 hours, and further allowed to stand at a temperature of 40 ° C. and a humidity of 80% for 24 hours, and then the roll appearance was evaluated in the same manner as in the above [Evaluation of Roll Appearance].

[Evaluation of transfer (texture transfer) to the uneven film on the surface of the protective film]
The optical film was cut out from the roll on which the above [Evaluation of Storage Stability] was performed, and the reflected light of the fluorescent lamp via the optical film was visually evaluated. If there was no change in the shape of the fluorescent lamp, “A” was set, “B” was set when the edge of the fluorescent lamp was disturbed, and “C” was set when the fluorescent lamp was totally distorted.

[Evaluation of foam biting during bonding]
Using a “V-550 UV-Visible spectrophotometer” manufactured by JASCO Corporation, the total light reflectance was measured at an incident angle of 5 °. The sample used a multilayer film in which an optical film and a protective film were bonded, and the surface of the protective film on the back layer side was polished with # 320 emery polishing paper. If an air layer is generated at the bonding interface due to foam biting, the total light reflectivity is increased by increasing the number of air interfaces. Therefore, the smaller the total light reflectivity measured, the less the bubble bite. Specifically, when the total light reflectance is less than 8.0%, there is almost no bubble biting, and when the total light reflectance is 8.0% or more, the bubble biting can be visually confirmed.

[Evaluation of rough surface shape of protective film]
Using a “DEKTAK 6M stylus type surface shape measuring instrument” manufactured by ULVAC, the length of the protective film is 10 mm, the tip radius of the stylus is 2.5 μm, and the load of the stylus is 10 mg. The arithmetic average roughness Ra and the average interval Sm of the irregularities were measured in the MD direction of the surface.

(Measurement of tensile modulus)
Using “Tensilon UTM-10T-PL” manufactured by Toyo Baldwien, tensile speed: 500 mm / min, load: load cell 50 kgf, sample shape: width 10 mm × length 50 mm, number of tests: 5 times, long optical The tensile modulus in the MD direction of the film was measured.

[Measurement of static friction coefficient (according to ASTM D1894)]
Using Intesco's "precision universal material testing machine 2005 type", test speed: 150 mm / min, test load: 200 g (with rubber load), slip surface: film to metal (chromium plated iron plate), test direction: MD direction The static friction coefficient of the film surface was measured at a test temperature of 23 ° C. and a test number of 5 times.

[Evaluation of surface shape of optical film]
Arithmetic average roughness Ra was measured using “New View 5000” manufactured by Zygo Corp. with an objective lens of 10 times and a measurement region of 358 μm × 268 μm.

[Example 1]
(Manufacture of raw film)
Pellets of the alicyclic structure-containing polymer resin [“ZEONOR1420” manufactured by Nippon Zeon Co., Ltd.] were dried at 100 ° C. for 5 hours. The pellets are supplied to an extruder, melted in the extruder, passed through a polymer pipe and a polymer filter, extruded from a T-die onto a casting drum, cooled, and unstretched with a length of 80 μm and a width of 1650 mm. A film was obtained.

(Stretching film)
The obtained unstretched film was stretched at a stretching temperature of 135 ° C. in the MD direction at a stretching ratio of 1.15 times, and further stretched at a stretching temperature of 140 ° C. in the TD direction at a stretching ratio of 1.45 times. Obtained. The obtained optical film had a tensile modulus of 2150 MPa and a thickness of 52 μm. The static friction coefficient of the optical film was 1.02 on both sides, and the arithmetic average roughness Ra was 0.01 μm on both sides.

(Manufacture of protective film)
80% by weight of olefin crystal / ethylene butylene / olefin crystal block polymer (CEBC) [“DYNARON6200P” manufactured by JSR Corporation], 16 ethylene / propylene copolymer (230 ° C. or less MFR 30 g / 10 min, ethylene content 5% by weight) % By weight and 4% by weight of low density polyethylene [190 ° C. or less MFR 2 g / 10 min, density 0.92 g / cm ³ ] are uniformly mixed with a Henschel mixer to prepare an adhesive layer resin as an adhesive layer material. .

75% by weight of ethylene-propylene copolymer [230 ° C. or lower MFR 30 g / 10 min, ethylene content 5% by weight] and 2 wt. Of low density polyethylene [190 ° C. or lower MFR 2 g / 10 min, density 0.92 g / cm ³ ] % And 23% by weight of hydrogenated styrene butadiene rubber (HSBR) [“DYNARON1320P” manufactured by JSR Corporation] were uniformly mixed with a Henschel mixer to prepare a back layer resin as a back layer material.

  Using a two-type, two-layer multi-layer coextrusion device, the adhesive layer resin and the back layer resin were extruded at a extrusion temperature of 230 ° C. at an extrusion rate of 3.8 kg / hour and 3.8 kg / hour, respectively. The film was formed by discharging. Immediately after discharging from the die, the film is nipped with a shaping roll having irregularities on the surface and a mirror-like roll having a mirror-like surface, so that the shaping roll is on the back layer side, and the shaping roll The film was transferred to a film and then cooled to obtain a protective film having a two-layer structure having a length of 4500 m and a width of 1380 mm. The nip conditions were a linear pressure of 12 kN / m, a roll speed of 20 m / min, a surface temperature of the shaping roll of 70 ° C., and a surface temperature of the mirror roll of 70 ° C. Moreover, the average interval Sm of the irregularities on the surface of the shaping roll was 200 μm.

The thickness of each layer constituting the obtained protective film is such that the thickness of the back layer on the side where the irregularities are formed is 15 μm, the thickness of the adhesive layer on the side where the irregularities are not formed is 15 μm, and the total thickness of the protective film is It was 30 μm.
The surface on the back layer side where the unevenness of the obtained protective film was formed was a rough surface having an arithmetic average roughness Ra of 0.2 μm and an average interval Sm of unevenness of 200 μm.

(Pasting of protective film)
The protective film was bonded to the optical film by bonding the adhesive layer of the protective film to the optical film at a nip pressure of 0.5 MPa.

(Take-up)
The film was wound into a roll at a tension of 100 N / m, a taper of 20%, a speed of 30 m / min, a width of 1330 mm, and a length of 3900 m to obtain an optical film roll.

  The obtained optical film roll was evaluated in the manner described above for roll appearance, storage stability, transfer to a concavo-convex optical film on the surface of the protective film, and bubble biting during bonding. The evaluation results of roll appearance and storage stability are shown in Table 2. In Table 2, among the evaluation results in each column, the left evaluation result represents the evaluation result immediately after winding, and the right evaluation result represents the evaluation result after storage. Moreover, the evaluation result of the transcription | transfer to the uneven | corrugated optical film of the protective film surface is shown in Table 3, and the evaluation result of the bubble biting at the time of bonding is shown in Table 4.

[Examples 2 to 16, Comparative Examples 1 to 20]
An optical film roll was produced in the same manner as in Example 1 except that the surface roughness on the back layer side of the protective film was changed by using a molding roll having a different surface shape. In addition, the value of arithmetic mean roughness Ra of the surface by the side of the back layer of a protective film and the average space | interval Sm of an unevenness | corrugation are as Table 1 below. With respect to each of the obtained optical film rolls, the roll appearance, storage stability, transfer to the uneven optical film on the surface of the protective film, and bubble biting during bonding were evaluated in the manner described above. The results are shown in Tables 2-4.

  From Tables 1 to 4, the arithmetic average roughness Ra of the surface opposite to the optical film of the protective film (that is, the surface on the back layer side of the protective film) is 0.2 μm or more and 0.5 μm or less, and unevenness It was confirmed that when the average distance Sm is 200 μm or more and 500 μm or less, it is possible to suppress the occurrence of band, texture transfer and bubble biting, and to realize an optical film roll excellent in storage stability.

  The optical film roll of the present invention and the production method thereof can be applied to any optical film containing an alicyclic structure-containing polymer, for example, a retardation film, a polarizing film, a brightness enhancement film, a light diffusion film, a light collecting film, It can be preferably applied to a reflective film or the like.

DESCRIPTION OF SYMBOLS 10 Optical film 11 Optical film 12 Optical film 12D The surface on the opposite side to the protective film of an optical film 20 Protective film 20A Recessed part 20B Convex part 20D Boundary surface which bonded the optical film and the protective film Opposite surface (rough surface)
20X Concavity and convexity 21 Protective film 21A Concave portion 21B Convex portion 21U Surface opposite to the optical film of the protective film (rough surface)
21X Concavity and convexity 22 Protective film 30 Multi-layer film 31 Multi-layer film 32 Multi-layer film 40 Winding core 50 Void 61 Laminating roll 62 Laminating roll 100 Optical film roll 110 Outer peripheral surface of optical film roll 120 Air 130 Portion where air remains

Claims (6)

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,
An optical film roll having an arithmetic average roughness Ra of 0.2 μm or more and 0.5 μm or less and an average interval Sm of 200 μm or more and 500 μm or less of the surface of the protective film opposite to the optical film. . 2. The optical film roll according to claim 1, wherein the arithmetic average roughness Ra and the average interval Sm between the concaves and convexes on the surface of the protective film opposite to the optical film satisfy the relationship of the following formula (1).

(However, the integration of equation (1) is performed for one cycle of the sin curve.)   The optical film roll according to claim 1 or 2, wherein the protective film contains a polyolefin-based polymer.   The optical film roll as described in any one of Claims 1-3 whose static friction coefficient of the surface on the opposite side to the said protective film of the said optical film is 0.7 or more.   The optical film roll as described in any one of Claims 1-4 whose arithmetic mean roughness Ra of the surface on the opposite side to the said protective film of the said optical film is 0.05 micrometer or less. A step of melt-extruding the alicyclic structure-containing polymer to obtain an optical film,
A step of bonding a protective film peelable from the optical film to the optical film to obtain a multilayer film;
A step of winding the multilayer film into a roll, and a method for producing an optical film roll,
An optical film roll having an arithmetic average roughness Ra of 0.2 μm or more and 0.5 μm or less and an average interval Sm of 200 μm or more and 500 μm or less of the surface of the protective film opposite to the optical film. Manufacturing method.

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