JP2011112945A - Roll-like wound body - Google Patents

Abstract

A long roll-shaped wound body having no irregularities is provided.
In a roll-shaped wound body obtained by winding a long multilayer film comprising a long optical film and a long protective film that can be peeled off from the long optical film into a roll, The variation of the film thickness in the width direction of the long optical film is within the range of ± 0.3% to ± 3.0% of the average value of the film thickness in the width direction, and the long optical film side of the long protective film The three-dimensional centerline average roughness of the surface opposite to the surface is set to 0.2 μm or more and 3.0 μm or less.
[Selection figure] None

Description

  The present invention relates to a roll-shaped wound body in which a long optical film is wound.

  Conventionally, in display devices such as liquid crystal display devices, it is known to provide optical films such as retardation films, polarizing films, and brightness enhancement films. Such an optical film is manufactured in a long shape by collecting a certain amount from the viewpoint of manufacturing efficiency, and the long film is stored as a roll-shaped wound body. After storing for a certain period of time, pull out the long film from the roll-shaped wound body, and paste it with other long films as necessary by the roll-to-roll method, etc., and then perform molding such as punching, etc. It is incorporated in and used.

  When winding a long optical film, a technique of laminating a protective film on an optical film is known for protecting the optical film and improving handling properties (see Patent Document 1). A protective film is laminated on an optical film to form a multilayer film, and the multilayer film is wound to form a roll-shaped wound body, thereby improving the handleability during winding and drawing, or attaching a film. The optical film can be protected from dust or the like.

JP 2005-125659 A

Here, the optical film is generally required to have a small difference in film thickness depending on the position, that is, to be uniform without thickness unevenness (variation). For this reason, the film thickness of the optical film is generally uniform at a high level. However, even when the optical film is a uniform optical film with a high film thickness, when the roll-shaped wound body is used, the difference in film thickness is amplified by the optical film being wound, and the long roll-shaped wound body As a result, a part of the protrusion may protrude or dent to cause unevenness. Moreover, even if there is no unevenness immediately after winding, deformation may occur with the passage of time, resulting in unevenness. If such unevenness is generated in the roll-shaped wound body, the unevenness may be transferred to the optical film and an optical defect may occur. In addition, since the appearance of the roll-shaped wound body is impaired when irregularities occur in the roll-shaped wound body, even if there is no loss in performance in actual commercial transactions, the product value is evaluated low because of the appearance. Sometimes.
Also, even if there is some thickness unevenness, if it is excellent in optical properties, it can be accepted as a product.In this case, even when an optical film with such thickness unevenness is wound, When it is set as a roll-shaped winding body, it is calculated | required to make it the state without an unevenness | corrugation on the surface.

  This invention is made | formed in view of said subject, Comprising: It aims at providing the roll-shaped winding body without an unevenness | corrugation.

The present inventor has intensively studied to achieve the object by solving the problems described above, and when the concave portion exists on the surface of the optical film, when the optical film is wound, the concave portion is It has been found that there is a tendency to gradually increase, and according to the roll-shaped wound body obtained in this way, air stays in the recessed portion and it is difficult to discharge the air. Therefore, as a result of the study of the present inventors, as a protective film to be laminated on the optical film, by making the surface a rough surface to some extent, the air entrained when the optical film is wound can be appropriately discharged, so that the roll-shaped winding The present inventors have found that the appearance of the rotatory body can be made beautiful and completed the present invention.
That is, the gist of the present invention is the following [1] to [4].

[1] A roll-shaped wound body obtained by winding a long multilayer film comprising a long optical film and a long protective film that can be peeled off from the long optical film into a roll. ,
The variation of the film thickness in the width direction of the long optical film is in the range of ± 0.3% to ± 3.0% of the average value of the film thickness in the width direction,
The long protective film is a roll-shaped wound body having a three-dimensional centerline average roughness of 0.2 μm or more and 3.0 μm or less on a surface opposite to the surface of the long optical film.
[2] The roll-shaped wound body according to [1], wherein a tensile elastic modulus in a longitudinal direction of the long protective film is 100 MPa or more and 400 MPa or less.
[3] The long optical film is a multilayer film composed of b layer / a layer / b layer,
The a layer is composed of a polystyrene polymer,
Said b layer is a roll-shaped winding body as described in [1] or [2] comprised by the polymethylmethacrylate polymer.
[4] The long protective film includes an adhesive layer that adheres to the optical film, and a back layer that is located on the opposite side of the adhesive layer from the optical film and does not adhere to the optical film. The roll-shaped wound body according to any one of [1] to [3].

  According to the roll-shaped wound body of the present invention, it is possible to suppress the occurrence of unevenness in the roll-shaped wound body.

  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〕
The roll-shaped wound body of the present invention rolls a long multilayer film comprising a long optical film having a certain degree of thickness unevenness and a long protective film that can be peeled off from the long optical film. It is a roll-shaped wound body formed by winding a soft protective film having a rough surface having a predetermined roughness on the surface thereof as the long protective film. As a result, the air entrained at the time of winding can be discharged, so that the occurrence of unevenness in the roll-shaped wound body obtained by winding the multilayer film including the optical film and the protective film into a roll shape is suppressed, and the roll-shaped wound body The appearance can be kept clean.

[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.

The thickness unevenness of the optical film is such that the variation of the film thickness in the width direction falls within the range of ± 0.3% to ± 3.0% of the average value of the film thickness in the width direction. Specifically, when the maximum value of the film thickness in the width direction of the optical film is Tmax, the minimum value is Tmin, and the average value is Tave, at least one of the maximum value Tmax and the minimum value Tmin is the following (a): Or, it is within the range of (b), and preferably both the maximum value Tmax and the minimum value Tmin of the film thickness are within the following ranges (a) and (b).
(A) The maximum value Tmax of the film thickness is usually Tave + 0.3% or more, usually Tave + 3.0% or less, preferably Tave + 2.0% or less, and more preferably Tave + 1.0% or less.
(B) The maximum value Tmin of the film thickness is usually Tave-0.3% or less, usually Tave-3.0% or more, preferably Tave-2.0% or more, more preferably Tave-1.0%. That's it.

  In the above (a) and (b), “Tave + k%” (k is a positive number) means a film thickness larger by k% than Tave, and “Tave−k%” (k is positive). The number “)” means a film thickness smaller by k% than Tave. Therefore, for example, the description “Tave + 0.3%” represents a film thickness that is 1.003 times that of Tave (that is, 100.3%). For example, the description “Tave−0.3%” indicates that the Tave is 0.3. This represents a film thickness of 997 times (that is, 99.7%).

An optical film having no thickness unevenness and an optical film having very small thickness unevenness do not cause unevenness in the roll-shaped wound body even when the roll-shaped wound body is formed by a conventional technique, and the effects of the present invention are hardly exhibited. Therefore, from the viewpoint of effectively demonstrating the effects of the present invention, it is preferable to use an optical film according to the present invention that has a large variation in film thickness in the width direction as described above.
On the other hand, the optical film with excessive thickness unevenness can reduce the unevenness of the roll-shaped wound body by combining with the protective film according to the present invention, but the unevenness is enough to withstand the evaluation in actual commercial transactions. There is a possibility that it cannot be lost. Further, if the thickness unevenness of the optical film is excessive, the optical film may not exhibit desired optical activity. For this reason, as an optical film which concerns on invention, it is preferable to use the thing whose grade of the fluctuation | variation of the film thickness in the width direction is as small as mentioned above.

  The average value Tave of the film thickness of the optical film varies depending on the type and use of the optical film, but is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 700 μm or less, preferably It is 500 μm or less, more preferably 300 μm or less.

  The film thickness of the optical film is an on-line infrared film thickness meter (manufactured by Kurabo Industries, trade name RX-200). The optical film being transported is 2 mm apart in the width direction, the transport speed is 10 m / min. The average thickness in the film width direction may be calculated from the average value of all measurement results measured at least 10 times in the width direction, and the thickness unevenness in the film width direction may be calculated as the ratio of the fluctuation width from the average thickness. It should be noted that before the winding of the optical film is started and after the winding is completed, sampling is performed, offline measurement is performed, and the absolute value (average value) of the online film thickness meter is corrected. In offline measurement, an optical film is embedded in an epoxy resin, then sliced to a thickness of 0.05 μm using a microtome [Daiwa Kogyo Co., Ltd., RUB-2100], and a cross section is observed using a transmission electron microscope And measure it. The measurement is performed at intervals of 100 mm in the flow direction over a length of 1000 mm, the average thickness in the film width direction is calculated from the average value of all measurement results, and the online average thickness is corrected to match the offline average thickness.

  An optical film that is harder than the protective film can be used. This is to make the protective film softer than the optical film from the viewpoint of absorbing thickness unevenness of the optical film by deformation of the protective film. The specific hardness of the optical film may be set according to the use of the optical film, but the tensile elastic modulus (Young's modulus) in the longitudinal direction (MD direction) of the optical film is usually 800 MPa or more, preferably 1200 MPa or more. More preferably, it is 1600 MPa or more, usually 3700 MPa or less, preferably 3300 MPa or less, more preferably 2900 MPa or less. The tensile modulus can be measured by a tensile tester (Instron, 5564 type digital material tester) according to JIS K7113.

As the optical film, a single-layer film having only one layer may be used, or a laminated film having two or more layers may be used.
Examples of the optical film include a retardation film, a polarizing film, a brightness enhancement film, a light diffusion film, a condensing film, and a reflection film.

  As a material for the optical film, a resin is usually used, and a thermoplastic resin is preferably used. Examples of polymers contained in the resin include olefin polymers such as polyethylene and polypropylene, polyester polymers such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyarylene sulfide polymers such as polyphenylene sulfide, and polyvinyl alcohol heavy polymers. Polymer, polycarbonate polymer, polyarylate polymer, cellulose ester polymer, polyethersulfone polymer, polysulfone polymer, polyallyl sulfone polymer, polyvinyl chloride polymer, norbornene polymer, rod-like liquid crystal polymer, styrene or styrene Polystyrene polymers including homopolymers of derivatives or copolymers with other monomers, polyacrylonitrile polymers, polymethylmethacrylate polymers, or multicomponent copolymers thereof. Such as if the polymer, and the like. Moreover, an additive can also be contained in resin as needed. In addition, the material of an optical film may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  An example of a particularly suitable optical film is a multilayer film composed of b layer / a layer / b layer, wherein the a layer is composed of a polystyrene polymer, and the b layer is composed of a polymethyl methacrylate polymer. One that is configured.

  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 a film as needed.

[3. Protective film〕
As the protective film, a long protective film that can be peeled off from the optical film is used. The protective film is laminated on at least one side of the long optical film, and the optical film is stored or transported in the state of a multilayer film laminated with the protective film. However, since the protective film is peeled off from the optical film when the optical film is used, a protective film that can be peeled off from the optical film is used.

  The tensile elastic modulus in the longitudinal direction (MD direction) of the protective film is usually 100 MPa or more, preferably 120 MPa or more, more preferably 140 MPa or more, and usually 400 MPa or less, preferably 340 MPa or less, more preferably 280 MPa or less. By using a soft protective film having such a small tensile elastic modulus, the protective film functions as a cushion. Therefore, the unevenness of the thickness of the optical film is absorbed by deformation of the protective film, and irregularities are generated in the roll-shaped wound body. And the appearance of the roll-shaped wound body can be kept clean. In addition, a protective film having a low tensile elastic modulus can eliminate wrinkles and slackness by pulling the protective film with a relatively weak force even if wrinkles or slackness occurs during bonding with an optical film.

  On the other hand, if the tensile modulus of the protective film is too high, the resin is detached from the protective film due to rubbing with a roll (for example, a metal roll, a rubber roll, etc.) used for transportation when the protective film is transported. The resulting resin may become a white powder and adhere to the roll. When white powder adheres to the roll, the white powder may reattach to the protective film, or the shape of the white powder adhered to the roll surface may be transferred to the protective film. In addition, white dust adhered to the protective film adheres to the optical film, or the shape of the white powder transferred to the protective film is further transferred to the optical film, thereby causing contamination, damage, dents, etc. to the optical film. It can happen.

  On the other hand, if the tensile elastic modulus of the protective film is too low, air may be entrained when the multilayer film is wound, and the roll-shaped wound body may have irregularities due to the entrainment of the air. In addition, unevenness may occur in the appearance of the roll-shaped wound body even when the above-described air is released over time. Furthermore, when the tensile elasticity modulus of a protective film is too low, there exists a tendency for the slip characteristic and handling property of a protective film to deteriorate. In addition, when a multilayer film is manufactured by laminating an optical film and a protective film, the protective film may be bonded with some tension (feeding tension), but the protective film has a tensile modulus of elasticity. If it is too low, the elongation of the protective film becomes large when the protective film is unwound, and the multilayer film may be warped and curled due to the shrinkage of the protective film after bonding with the optical film. In particular, when the degree of curling is large, the longitudinal end of the multilayer film may be rounded.

  In order to make the tensile elastic modulus of the protective film fall within the above-described range, for example, the degree of polymerization of the polymer contained in the protective film is adjusted, or the ratio between the polymer and the low molecule contained in the protective film is adjusted. You can adjust it.

  Further, the surface opposite to the long optical film side of the protective film (hereinafter referred to as “rear surface” as appropriate) is a rough surface having a predetermined roughness. The specific roughness of the rough surface is a three-dimensional centerline average roughness Ra, which is usually 0.2 μm or more, preferably 0.4 μm or more, more preferably 0.6 μm or more, and usually 3.0 μm or less. Preferably it is 2.4 micrometers or less, More preferably, it is 1.8 micrometers or less. The roughness of the rough surface is an average interval Sm of irregularities, which is usually 0.2 μm or more, preferably 0.4 μm or more, more preferably 0.6 μm or more, and usually 10,000 μm or less, preferably 5000 μm or less. Preferably it is 2500 micrometers or less. The three-dimensional centerline average roughness Ra and the average interval Sm of the unevenness can be measured based on JIS B 0601: 1994 using a surface roughness meter (product name “SJ400” manufactured by Mitutoyo Corporation).

  By having the roughness in such a range, it is possible to prevent the occurrence of unevenness due to air entrainment when the multilayer film is wound. That is, if the above-mentioned rough surface is not formed on the protective film, the discharge of the entrained air becomes insufficient, and as described above, the appearance of the roll-shaped wound body tends to be depressed after the entrained air is removed over time. There is a tendency that the recess becomes larger as the winding speed increases. However, if the protective film has the above-described rough surface, the entrapped air is sufficiently discharged from the rough surface portion during winding, so that it is possible to prevent the roll-shaped winding body from being recessed due to the entrapped air. Moreover, according to the said rough surface, slipperiness can be improved and the handleability of a film can also be improved. Moreover, the winding shift | offset | difference resulting from entrainment of the air at the time of winding the said 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 foreign matter from being transferred to the surface.

  By the way, preventing the occurrence of dents in the roll-shaped wound body due to the entrained air can be achieved by controlling the production conditions when the optical film and the protective film are bonded to produce a multilayer film. realizable. For example, slow down the winding speed of the optical film and the protective film, increase the sandwiching pressure of the roll (nip roll and take-up roll) that sandwiches the optical film and the protective film at the time of bonding, or increase the tension of the optical film and the protective film. You can make it stronger. However, when the winding speed is slowed down, the production efficiency is lowered. Further, when the sandwiching pressure is increased or the tension is increased, internal stress (compressive stress in the radial direction of the roll-shaped wound body) tends to increase in the obtained multilayer film. When the internal stress increases, the optical film and the protective film are pressure-bonded with a relatively strong adhesive force, so that the optical film and the protective film are easily blocked, so the protective film is peeled off from the multilayer film when the optical film is used. Can be difficult. In addition, when the internal stress increases, foreign matter (such as fish eyes) exists in the protective film, or foreign matter enters the optical film between the optical film and the protective film during bonding. It tends to be transferred and become a dent, which may cause optical defects. On the other hand, when the protective film has the rough surface, it is possible to prevent the roll-shaped wound body from being generated due to the entrained air without controlling the manufacturing conditions as described above.

  Moreover, a protective film is normally preserve | saved and conveyed as a roll-shaped winding body, and is used by pulling out from a winding body 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 wound body. This is because when the back surface is a rough surface, the adhesive layer (described later) of the protective film and the back surface are difficult to adhere to each other. If the back surface and the pressure-sensitive adhesive layer are bonded, the pressure-sensitive adhesive layer may be peeled off from the protective film or the pressure-sensitive adhesive force may be reduced, and the peeling charge may be increased.

  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 0.25 g / cm or more, usually 25 g / cm or less, Preferably it is about 1 g / 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 usually depends on the surface roughness of the optical film, and in general, the closer the surface roughness of the optical film, the lower the adhesion.

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 to 100 μm 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 protective film may be a single-layer film composed of only one layer, but is usually a laminated film having 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 A-B-A or the general formula A-B, the styrenic polymer block A has a weight average molecular weight of 12,000 to 100,000 and a glass transition point of 20. Those having a temperature of at least ° C are preferred. 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, glass A transition point of −20 ° C. or lower is preferable. Furthermore, the weight ratio of the A component and the B component is preferably A / B = 5/95 to 50/50, more preferably A / B = 10/90 to 30/70.

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

  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 can 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 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 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 40 g / cm or more, more preferably 60 g / cm or more, and preferably 600 g / cm or less, with respect to other layers (intermediate layer, back layer, etc.) in contact with the protective film. More preferable is cm or less. 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 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 surface opposite to the optical film of the protective film (ie, the back side). It is a layer that does not. 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.

  Examples of polyolefin polymers include polyethylene, polypropylene, ethylene-propylene copolymer, propylene-α-olefin copolymer, ethylene-α-olefin copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene. -Methyl (meth) acrylate copolymer, ethylene-n-butyl (meth) acrylate copolymer, ethylene-vinyl acetate copolymer, etc. are mentioned. 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, propylene-based copolymer is more preferable, and ethylene-propylene is preferable. A copolymer is particularly preferred.

  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 the propylene copolymer at a ratio of 60 to 90% by weight and low density polyethylene of 40 to 10% by weight. 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 to 7 mol%. In addition, when adding heat resistance to a back surface layer, it can also select suitably so that ethylene content can be decreased and desired heat resistance can 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 to 40 g / 10 minutes. In particular, those having an MFR in the range of 20 to 40 g / 10 min are more preferable because low-temperature extrusion is possible and the back surface 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 to 5 g / 10 min.
Further, the low density polyethylene preferably has a density of 0.910 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. Further, if the density of the low density polyethylene is too low, it may be difficult to make the back surface 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, the production method (i) by the coextrusion molding method is such that 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 produce a protective film having a rough back surface, the surface of the back layer may be deformed to form irregularities having a predetermined roughness on the back surface. For example, a nip molding method that uses a forming roll having irregularities to press the protective film immediately after extrusion obtained in the coextrusion molding method and transfers the irregularities to the back surface; For example, a method of peeling the release film after transferring the unevenness of the release film by clamping, a method of cutting the back surface of the protective film by spraying fine particles on the back surface of the protective film, 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, it is possible to form irregularities on the back surface 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 unevenness on the back surface; a method in which the back surface layer is formed by adjusting the compounding ratio of materials such as a resin forming the back surface layer, etc. Can be 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 back surface 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 having irregularities is preferably 60 ° C. or higher and 200 ° C. or lower. The temperature of the mirror roll is more preferably 60 ° C. or higher and 130 ° C. or lower, and the temperature of the shaping roll having irregularities is more preferably 80 ° C. or higher and 180 ° C. or lower. 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 nonuniformity to arise on the back surface 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. When the roll speed is higher than this, uneven transfer unevenness tends to occur on the back surface of the protective film.

  The average interval Sm (JIS B0601: 1994) of the unevenness of the rough surface formed on the protective film can be adjusted by replacing the shaping roll with a shaping roll having a predetermined irregularity cycle.

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

[4. (Multilayer film)
The long multilayer film according to the present invention is a film including the above-described long optical film and a long protective film. 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.
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 according to the present invention is usually a multilayer film having two layers in total, each having one optical film and one protective film.

  The multilayer film according to the present invention 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.

  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. (Long roll wound body)
The roll-shaped wound body of the present invention is obtained by winding the long multilayer film in a roll shape.
In the roll-shaped wound body of the present invention, since the surface opposite to the long optical film of the protective film is a rough surface, it is possible to suppress the occurrence of unevenness due to air entrainment during winding. Is possible. Moreover, when a protective film functions as a cushion as mentioned above, it can suppress that an unevenness | corrugation arises in a roll-shaped winding body by thickness nonuniformity of an optical film, and the external appearance can be maintained beautifully.

  Moreover, in the roll-shaped wound body of the present invention, the occurrence of unevenness over time can be suppressed.

Although there is no restriction | limiting in the winding frequency of a roll-shaped winding body, 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, although there is no restriction | limiting in the outer diameter of a roll-shaped winding body, 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 roll-shaped wound body of the present invention is manufactured by winding a multilayer film in a roll shape. In winding, an appropriate winding core may be used as necessary, and a roll-shaped wound body may be manufactured by winding a multilayer film around the winding core.
The winding speed is not limited. However, if the winding speed is too high, 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. These are usually 50 m / min or less, preferably 45 m / min or less, and more preferably 40 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. Can be implemented.

〔Evaluation methods〕
(1) Measuring method of film thickness The film thickness of the optical film was measured using an on-line infrared film thickness meter (manufactured by Kurabo Industries, trade name RX-200), and the optical film being conveyed was conveyed at intervals of 2 mm in the width direction. Is 10 m / min, the average thickness in the film width direction is calculated from the average value of all measurement results measured at least 10 times in the film width direction, and the thickness unevenness in the film width direction is calculated as the ratio of the fluctuation width from the average thickness. Calculated. In addition, before starting winding of an optical film and after winding was completed, it sampled, performed offline measurement, and correct | amended the absolute value (average value) of the online film thickness meter. In offline measurement, an optical film is embedded in an epoxy resin, then sliced to a thickness of 0.05 μm using a microtome [Daiwa Kogyo Co., Ltd., RUB-2100], and a cross section is observed using a transmission electron microscope And measured. The measurement was performed at intervals of 100 mm in the flow direction over a length of 1000 mm, the average thickness in the film width direction was calculated from the average value of all measurement results, and the online average thickness was corrected to match the offline average thickness.

(2) Measuring method of tensile modulus of film Tensile modulus of film is measured in the longitudinal direction (MD direction) and width with a tensile tester (Instron, 5564 type digital material tester) according to JIS K7113. The tensile elastic modulus of each film in the direction (TD direction) was measured. The measurement conditions were a tensile speed of 5 m / min, a test count of 5 times, a room temperature of 23 ° C., and a humidity of 50% RH. The strain was measured by placing a point at a distance of 50 mm in the center of the test piece and measuring the distance between the two points with a video extensometer (Instron).

(3) Measuring method of back surface roughness Three-dimensional centerline average surface roughness Ra on the back surface of the protective film and the average interval Sm of unevenness were measured using a surface roughness meter (product name “SJ400”, manufactured by Mitutoyo Corporation). 0601: Measured based on 1994. Sm (average interval of irregularities) is a contour curve (roughness curve) obtained by cutting a long wavelength component with a high-pass filter having a cutoff value λc from the measured cross-sectional curve, and the roughness curve The reference length (L) is extracted with respect to the average line, and is the average value of the lengths (Xsi) of adjacent peaks and valleys on the reference length. Ra (arithmetic mean roughness) is the average value of the absolute value of the height (distance from the average line to the measurement curve) at the reference length of the curve obtained by the method as described above. is there.

(4) Evaluation of bonding state From a multilayer film in which a protective film and an optical film are bonded, a square test piece of 250 mm in the longitudinal direction and 250 mm in the width direction is cut out and mixed between the optical film and the protective film. The bubbles to be evaluated were visually evaluated.

(5) Evaluation of appearance The appearance of the roll-shaped wound body was visually observed to evaluate the presence or absence of dents.

(6) Evaluation of unwinding of protective film After winding the manufactured protective film into a wound body, the protective film is pulled out from the end of the wound body, and three test pieces are cut out in the width direction. The test piece has a width of 25 mm and a length of 100 mm or more. The cut specimen is put in a 180 ° peel state, and the peeling force when the adhesive layer and the back layer of the specimen are peeled at 200 mm / min is measured three times, and the average value is taken as the unwinding force. At this time, if the unwinding force is 0.1 N / 25 mm or less, the unwinding is small and the handling property is good, and if the unwinding force exceeds 0.1 N / 25 mm, the unwinding is large and the handling property is poor. Shall. The 180 ° peel state means that the adhesive layer and the back layer of the test piece cut from the protective film are pulled to the opposite side, and the pulling direction of the adhesive layer and the pulling direction of the back layer form an angle of 180 °. It means the state to do.

[Example 1]
(1) Production of protective film Olefin crystal / ethylene butylene / olefin crystal Block polymer (CEBC) [manufactured by JSR, trade name “DYNARON (registered trademark) 6200P” 80% by weight, ethylene-propylene copolymer [230 ° C. or lower MFR 30 g / 10 minutes, ethylene content 5% by weight] and 16% by weight, and low density polyethylene [190 ° C. or less MFR 2 g / 10 minutes, density 0.92 g / cm ³ ] 4% by weight, uniformly mixed with a Henschel mixer. An adhesive layer resin was prepared as a material for the adhesive layer.

75% by weight of ethylene-propylene copolymer [230 ° C. or lower MFR 30 g / 10 minutes, ethylene content 5% by weight] and 2 weight of low density polyethylene [190 ° C. or lower MFR 2 g / 10 minutes, density 0.92 g / cm ³ ] % And hydrogenated styrene butadiene rubber (HSBR) [trade name “DYNARONTM1320P” manufactured by JSR Co., Ltd., 23% by weight, were uniformly mixed by 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 2300 m and a width of 1550 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 80 μm.
The mirror roll used for the nip has a three-dimensional centerline average roughness Ra of the back layer of 0. 0 when a film is formed by niping under the same conditions as described above using a pair of opposed mirror rolls. 22 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 three-dimensional centerline average roughness Ra of the back surface on which the unevenness of the obtained protective film was formed, the average interval Sm of the unevenness, and the Ra on the surface on the adhesive layer side where the unevenness of the protective film was not formed were measured. The results are shown in Table 1.
Furthermore, the tensile elasticity modulus of the obtained protective film was measured in MD direction and TD direction. The results are shown in Table 2.
Moreover, when the rewinding evaluation was performed on the protective film, the result was good.

(2) Manufacture of optical film Methacrylic resin composition comprising a layer composed of styrene-maleic anhydride copolymer resin (Nova Chemical Japan, product name: Dirac D332), which is a resin having a negative intrinsic birefringence value, and rubber particles An unstretched laminate c having a b layer composed of a product in the order of b layer / a layer / b layer was prepared by coextrusion molding of the resin. At this time, the thickness of the b layer / a layer / b layer was set to 55 μm / 30 μm / 55 μm, respectively.

The obtained unstretched laminate c is simultaneously biaxially stretched at a stretching temperature of 135 ° C. at a stretching ratio of 1.8 times in the MD direction and a stretching ratio of 1.3 times in the TD direction, and an optical film having a total thickness of 60 μm. Got.
About the obtained optical film, the average thickness and thickness nonuniformity were measured in the way mentioned above. The results are shown in Table 3.

(3) Bonding of protective film and optical film The surface of the prepared protective film on the adhesive layer side and the optical film are bonded to each other with a protective film feeding tension of 20N and an optical film transport tension of 150N. Got. The obtained multilayer film had a length of 2000 m and a width of 1490 mm. The number of windings of the roll-shaped wound body was 2089 times. This multilayer film was wound into a roll shape at a winding tension of 120 N to 140 N and a winding speed of 10 m / min to obtain a roll-shaped wound body of a multilayer film including a protective film and an optical film. The laminated state of the obtained multilayer film and the appearance of the roll-shaped wound body were evaluated in the manner described above. The results are shown in Table 5.

[Example 2]
(1) Production of protective film The amount of ethylene-propylene copolymer to be contained in the back layer resin was 82% by weight, the amount of hydrogenated styrene butadiene rubber was 16% by weight, and the molding to nip the protective film A protective film was obtained in the same manner as in Example 1 except that a shaping roll having an average interval Sm of surface irregularities of 540 μm was used as the roll.
Ra and Sm of the back surface in which the unevenness | corrugation of the obtained protective film was formed, and Ra of the surface at the side of the adhesion layer in which the unevenness | corrugation of the protective film was not formed were measured. The results are shown in Table 1.
Furthermore, the tensile elasticity modulus of the obtained protective film was measured in MD direction and TD direction. The results are shown in Table 2.
Moreover, when the rewinding evaluation was performed on the protective film, the result was good.

(2) Production of optical film An optical film was obtained in the same manner as in Example 1 except that a far-infrared panel heater was installed in a drawing furnace and an appropriate temperature distribution was formed in the width direction. The temperature distribution was adjusted so that the stretching temperature was in the range of 135 ° C to 140 ° C. About the obtained optical film, the average thickness and thickness nonuniformity were measured in the way mentioned above. The results are shown in Table 3.

(3) Bonding of protective film and optical film Using the prepared protective film and optical film, a multilayer film was produced in the same manner as in Example 1 except that the feeding tension of the protective film was 40 N. Furthermore, the roll-shaped winding body of this multilayer film was obtained. The laminated state of the obtained multilayer film and the appearance of the roll-shaped wound body were evaluated in the manner described above. The results are shown in Table 5.

Example 3
(1) Production of protective film The amount of ethylene-propylene copolymer to be contained in the back layer resin was 95% by weight, the amount of hydrogenated styrene butadiene rubber was 3% by weight, and the molding to nip the protective film A protective film was obtained in the same manner as in Example 1 except that a shaping roll having an average interval Sm of surface irregularities of 1100 μm was used as the roll.
Ra and Sm of the back surface in which the unevenness | corrugation of the obtained protective film was formed, and Ra of the surface at the side of the adhesion layer in which the unevenness | corrugation of the protective film was not formed were measured. The results are shown in Table 1.
Furthermore, the tensile elasticity modulus of the obtained protective film was measured in MD direction and TD direction. The results are shown in Table 2.
Moreover, when the rewinding evaluation was performed on the protective film, the result was good.

(2) Production of optical film An optical film was obtained in the same manner as in Example 1 except that a far-infrared panel heater was installed in a drawing furnace and an appropriate temperature distribution was formed in the width direction. The temperature distribution was adjusted so that the stretching temperature was in the range of 135 ° C to 142 ° C. About the obtained optical film, the average thickness and thickness nonuniformity were measured in the way mentioned above. The results are shown in Table 3.

(3) Bonding of protective film and optical film Using the prepared protective film and optical film, a multilayer film was produced in the same manner as in Example 1 except that the feeding tension of the protective film was 80 N. Furthermore, the roll-shaped winding body of this multilayer film was obtained. The laminated state of the obtained multilayer film and the appearance of the roll-shaped wound body were evaluated in the manner described above. The results are shown in Table 5.

[Comparative Example 1]
(1) Production of protective film The amount of the ethylene-propylene copolymer contained in the back layer resin was 98% by weight, no hydrogenated styrene butadiene rubber was used, and when the protective film was nipped, A protective film was obtained in the same manner as in Example 1 except that a mirror roll was used instead.
Ra and Sm of the back surface in which the unevenness | corrugation of the obtained protective film was formed, and Ra of the surface at the side of the adhesion layer in which the unevenness | corrugation of the protective film was not formed were measured. The results are shown in Table 1.
Furthermore, the tensile elasticity modulus of the obtained protective film was measured in MD direction and TD direction. The results are shown in Table 2.
Moreover, when the rewinding evaluation was performed on the protective film, the result was good.

(2) Production of optical film In the same manner as in Example 1, an optical film was obtained. About the obtained optical film, the average thickness and thickness nonuniformity were measured in the way mentioned above. The results are shown in Table 3.

(3) Bonding of protective film and optical film Using the prepared protective film and optical film, a multilayer film was produced in the same manner as in Example 1 except that the tension of the protective film was 90 N. Furthermore, the roll-shaped winding body of this multilayer film was obtained. The laminated state of the obtained multilayer film and the appearance of the roll-shaped wound body were evaluated in the manner described above. The results are shown in Table 5.

[Comparative Example 2]
(1) Production of protective film The amount of ethylene-propylene copolymer contained in the back layer resin was 95% by weight, the amount of hydrogenated styrene butadiene rubber was 3% by weight, and when the protective film was nipped A protective film was obtained in the same manner as in Example 1 except that a mirror roll was used instead of the shaping roll.
Ra and Sm of the back surface in which the unevenness | corrugation of the obtained protective film was formed, and Ra of the surface at the side of the adhesion layer in which the unevenness | corrugation of the protective film was not formed were measured. The results are shown in Table 1.
Furthermore, the tensile elasticity modulus of the obtained protective film was measured in MD direction and TD direction. The results are shown in Table 2.
Moreover, when the rewinding evaluation was performed on the protective film, the result was good.

(2) Production of optical film An optical film was obtained in the same manner as in Example 1 except that a far-infrared panel heater was installed in a drawing furnace and an appropriate temperature distribution was formed in the width direction. The temperature distribution was adjusted so that the stretching temperature was in the range of 135 ° C to 140 ° C. About the obtained optical film, the average thickness and thickness nonuniformity were measured in the way mentioned above. The results are shown in Table 3.

(3) Bonding of protective film and optical film Using the prepared protective film and optical film, a multilayer film was produced in the same manner as in Example 1 except that the feeding tension of the protective film was 80 N. Furthermore, the roll-shaped winding body of this multilayer film was obtained. The laminated state of the obtained multilayer film and the appearance of the roll-shaped wound body were evaluated in the manner described above. The results are shown in Table 5.

[Comparative Example 3]
(1) Production of protective film The amount of ethylene-propylene copolymer contained in the back layer resin was 98% by weight, no hydrogenated styrene butadiene rubber was used, and the surface of the surface as a forming roll for nipping the protective film. A protective film was obtained in the same manner as in Example 1 except that a shaping roll having an average unevenness interval Sm of 1160 μm was used.
Ra and Sm of the back surface in which the unevenness | corrugation of the obtained protective film was formed, and Ra of the surface at the side of the adhesion layer in which the unevenness | corrugation of the protective film was not formed were measured. The results are shown in Table 1.
Furthermore, the tensile elasticity modulus of the obtained protective film was measured in MD direction and TD direction. The results are shown in Table 2.
Moreover, when the rewinding evaluation was performed on the protective film, the result was good.

(2) Production of optical film An optical film was obtained in the same manner as in Example 1 except that a far-infrared panel heater was installed in a drawing furnace and an appropriate temperature distribution was formed in the width direction. The temperature distribution was adjusted so that the stretching temperature was in the range of 135 ° C to 143 ° C. About the obtained optical film, the average thickness and thickness nonuniformity were measured in the way mentioned above. The results are shown in Table 3.

(3) Bonding of protective film and optical film Using the prepared protective film and optical film, a multilayer film was produced in the same manner as in Example 1 except that the tension of the protective film was 90 N. Furthermore, the roll-shaped winding body of this multilayer film was obtained. The laminated state of the obtained multilayer film and the appearance of the roll-shaped wound body were evaluated in the manner described above. The results are shown in Table 5.

[Summary]
From Table 5, although the roll-shaped winding body of Examples 1-3 has no dent, it turns out that the roll-shaped winding body of Comparative Examples 1-3 has produced the dent. From this, in the roll-shaped wound bodies of Examples 1 to 3, the protective film has a rough surface with a predetermined roughness, so that air can be prevented from being caught, and the protective film has a low tensile elastic modulus. Since the protective film is deformed and can absorb thickness unevenness of the optical film, it was confirmed that the occurrence of unevenness in the roll-shaped wound body can be suppressed.
Moreover, from Table 5, in Examples 1-3, there is no bubble between the optical film bonded together and the protective film. Generally, when the surface on the adhesive layer side of the protective film is rough, the above-mentioned bubbles tend to increase. However, in the protective films of Examples 1 to 3, a rough surface having an appropriate roughness is formed on the back surface. It is considered that air is well removed at the time of combining, and generation of bubbles is prevented. On the other hand, in Comparative Example 3, air bubbles exist between the optical film and the protective film. This is because the protective film of Comparative Example 3 has too much roughness on the back surface, so the surface of the adhesive layer is rough due to the influence of the winding state of the protective film (hard winding, soft winding), material and roughness shape. It is surmised that the effect that bubbles are likely to be generated by the unevenness is expressed more than the effect that air bubbles are excessively increased and air escapes at the time of bonding to prevent the generation of bubbles. When the number of bubbles as in Comparative Example 3 increases, the bonding state becomes poor, and the appearance may become white and the appearance may be impaired. Moreover, when the said bubble is transcribe | transferred to an optical film, the optical characteristic of an optical film will change and there exists a possibility that the performance of an optical film may be impaired.

[Reference Example: Relationship between tension and elastic modulus to eliminate wrinkles and sag of protective film]
[Reference Example 1]
In the same manner as in “(1) Production of protective film” in Example 2, a protective film having a back layer thickness of 15 μm, an adhesive layer thickness of 15 μm, and a total thickness of 30 μm was produced. The tensile tension of the obtained protective film was 206 MPa in the MD direction and 269 MPa in the TD direction.
The obtained protective film was pulled in the MD direction while applying tension, and the value of the feeding tension at which wrinkles and slack disappeared from the protective film was measured. The results are shown in Table 6.

[Reference Example 2]
In the same manner as in “(1) Production of protective film” in Comparative Example 3, a protective film having a back layer thickness of 15 μm, an adhesive layer thickness of 15 μm, and a total thickness of 30 μm was produced. The tensile tension of the obtained protective film was 446 MPa in the MD direction and 543 MPa in the TD direction.
The obtained protective film was pulled in the MD direction while applying tension, and the value of the feeding tension at which wrinkles and slack disappeared from the protective film was measured. The results are shown in Table 6.

  From Table 6, the protective film of Reference Example 2 having a high tensile elastic modulus does not disappear wrinkles and slack unless pulled with a relatively large drawing tension, but the protective film of Reference Example 1 having a low tensile elastic modulus is relatively small. It can be seen that wrinkles and slack can be eliminated by pulling with the feeding tension.

  The long roll-shaped wound body of the present invention can be applied to an arbitrary optical film such as a retardation film, a polarizing film, a brightness enhancement film, a light diffusion film, a condensing film, and a reflective film.

Claims (4)

A roll-shaped wound body obtained by winding a long multilayer film comprising a long optical film and a long protective film that can be peeled off from the long optical film into a roll,
The variation of the film thickness in the width direction of the long optical film is in the range of ± 0.3% to ± 3.0% of the average value of the film thickness in the width direction,
The long protective film is a roll-shaped wound body having a three-dimensional centerline average roughness of 0.2 μm or more and 3.0 μm or less on a surface opposite to the surface of the long optical film.   The roll-shaped wound body according to claim 1, wherein a tensile elastic modulus in a longitudinal direction of the long protective film is 100 MPa or more and 400 MPa or less. The long optical film is a multilayer film composed of b layer / a layer / b layer,
The a layer is composed of a polystyrene polymer,
The roll layered body according to claim 1 or 2, wherein the b layer is composed of a polymethyl methacrylate polymer.   The long protective film includes an adhesive layer that adheres to the optical film, and a back layer that is located on the opposite side of the adhesive layer from the optical film and does not adhere to the optical film. The roll-shaped winding body as described in any one of -3.