JP2010038924A - Protective film-fitted optical film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent protective film-fitted optical film, e.g., the protective film-fitted wide optical film with a width of ≥2m, in which separation voltage is hard to be caused when, after production of a polarizing plate, the protective film is interlayer-separated, adverse influence is hardly exerted to a liquid crystal element, and further, paste is not substantially left after the separation, and to provide a method for producing the same. <P>SOLUTION: In the protective film-fitted optical film obtained by laminating a protective film on at least one side of an optical film, an adhesion material layer is not substantially present in the boundary between the optical film and the protective film, and also, unevenness of thickness measured across the width direction of the optical film is ≤5%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an optical film with a protective film having a wide width, for example, a width of 2 m or more, with small thickness unevenness, and the generation of a peeling voltage is suppressed when the protective film is delaminated after creation of a polarizing plate, The present invention relates to an excellent optical film with a protective film that does not adversely affect peripheral elements such as liquid crystal elements and suppresses the generation of adhesive residue at the time of peeling, and a method for producing the same. A film suitable for optical applications is provided. In addition, although a protective film here is not used as an optical member which finally comprises a liquid crystal display etc., it is a film which protects an optical film from dust, a crack, etc. in the manufacturing process.

  In the case of a conventional optical film, in order to protect from scratches and dust adhering to the surface of the optical film, an adhesive olefin-based coextruded film on the optical film or an acrylic film on the polyester film In many cases, a protective film made of a coating film coated with the above adhesive is used.

  However, in the process of bonding the protective film to the optical film described above, it often occurred that an air layer was bitten between the optical film and the protective film, or the protective film became a ridge and bonded. In particular, the greater the width of the optical film is, for example, 2 m or more, the higher the frequency of these air entrapments and wrinkles, causing a significant reduction in productivity. This is presumably due to the fact that the protective film is soft and has no stiffness, the thickness uniformity (particularly the thickness uniformity in the width direction) is poor and the flatness of the film is poor, or there is no slipperiness.

  Furthermore, since an adhesive is used for the protective film, an adhesive residue phenomenon may occur in which a part of the adhesive remains when delamination from the optical film, which may be a major optical defect. There were many.

  In addition, when the protective film is delaminated after the optical film is assembled on the liquid crystal element, there is a big problem that a large peeling voltage is generated and the liquid crystal element is destroyed or an optical defect is generated. It was.

  The first object of the present invention is to eliminate the disadvantages of the optical film on which such a conventional protective film is bonded, and to provide a wide optical film of, for example, 2 m or more, and further, adhesive residue at the time of delamination, It is an object of the present invention to provide an optical film that hardly generates a peeling voltage.

As a method for interlaminating an optical film and a protective film without using an adhesive material layer as described above, a method using coextrusion has already been proposed (see, for example, Patent Document 1 and Patent Document 2). . That is, both of these are methods in which the optical film resin and the protective film resin are both heated to the melting point or higher, and the layers are laminated in the molten state, and then expanded in the width direction, etc., to obtain the adhesive force between the layers. . However, in such a method, although the overall homogeneity of the total thickness of the laminated film can be obtained, the thickness of each individual layer constituting each layer cannot be adjusted. When the protective film is peeled off and the optical film is taken out because the homogeneity cannot be obtained, the optical film thickness uniformity is poor, and therefore optical defects such as retardation unevenness, which is the most important optical property, occur. In some cases, this is a big problem in practical use. In particular, in the case of a wide optical film whose width exceeds 2 m, for example, this thickness unevenness becomes very remarkable, and such a coextrusion method is not suitable for a method for producing a wide optical film having a width of 2 m or more, for example. There was a case. Furthermore, it was difficult to recover the laminate itself containing these different types of resin layers, so that the manufacturing cost was high and the productivity was poor.
JP 2002-338705 A JP 2003-240953 A

  As described above, the first object of the present invention is to eliminate the disadvantages of the optical film in which the conventional protective film is bonded via the adhesive layer, and to provide a wide optical film of, for example, 2 m or more, Furthermore, it is providing the optical film with a protective film which is hard to generate | occur | produce the adhesive residue and peeling voltage at the time of delamination. The second object of the present invention is to eliminate the drawbacks of the optical film with a protective film obtained by the conventional coextrusion method, and even if the optical film is wide, such as over 2 m in width, An object is to provide an optical film with a protective film that has excellent thickness uniformity, suppresses the occurrence of optical defects such as retardation unevenness, which is the most important optical property, and has a practically high value.

  The subject of this invention is achieving the said 1st objective and the 2nd objective simultaneously.

  As a result of intensive studies, the inventors have found that an optical film in which a protective film is laminated on at least one surface of the optical film has substantially no adhesive layer generally said at the interface between the optical film and the protective film. It is an optical film of a structure, Comprising: The thickness nonuniformity measured across the width direction of the said optical film (peak-to-peak) finds that the optical film with a protective film solves said subject, 5% or less, The present invention has been reached.

Although the pressure-sensitive adhesive layer is not substantially present, it is preferable that the delamination force between the optical film and the protective film exhibits a strong adhesive force of about 10 g / 25 mm width to 300 g / 25 mm width.
With such a configuration, a wide optical film having a width of 2 m or more can be provided more easily.
That is, the present invention
(1) In the optical film with a protective film in which the protective film (B) is laminated on at least one surface of the optical film (A), an adhesive layer is not substantially present at the interface between the optical film and the protective film, And it is related with the optical film with a protective film whose thickness nonuniformity measured across the width direction of the said optical film (A) is 5% or less (peak-to-peak). In the present invention, the phrase “the adhesive material layer substantially does not exist” means that an independent surface layer of an adhesive material is not formed by coextrusion or coating.

The following (2) to (14) are each one of preferred embodiments of the present invention.
(2) The optical film with a protective film according to (1), wherein an interlayer peeling force between the optical film (A) and the protective film (B) is 10 g / 25 mm width to 300 g / 25 mm width.
(3) The optical film with a protective film according to (1) or (2), wherein the optical film with the protective film has a width of 2 m or more.
(4) The optical film (A) is an acrylic resin, a cyclic olefin resin, a methylpentene resin, a polystyrene resin excellent in transparency, a polycarbonate resin, a polyester resin, a polymaleimide resin, and a syndiotac. The optical film with a protective film according to any one of (1) to (4), comprising at least one resin selected from the group consisting of tick polypropylene resins.
(5) The glass transition temperature (Tg) of the optical film (A) is 120 ° C. or higher (above (
The optical film with a protective film as described in 4).
(6) The optical film with a protective film according to any one of (1) to (5), wherein the surface of the protective film (B) on the side in contact with the optical film (A) has a friction coefficient of 1 or less. the film.
(7) The optical film with a protective film according to any one of (1) to (6), wherein the protective film (B) has a surface specific resistance value of 10 ¹¹ Ω / □ or less.
(8) With the protective film according to any one of (1) to (7) above, wherein the protective film (B) has a water vapor transmission rate of 20 (g / m ² · day / 0.1 mm) or more. Optical film. (9) Any of the above (1) to (3) and (5) to (7), wherein the thickness unevenness measured over a width direction of 2 m or more of the protective film (B) is 5% or less 2. An optical film with a protective film according to item 1.
(10) The protective film (B) includes at least one resin selected from the group consisting of linear low density polyethylene (LLDPE), polypropylene, and modified polyolefins, polyesters, and polycarbonates thereof. The optical film with a protective film according to any one of (1) to (8).
(11) On the at least one surface of the optical film (A), a manufacturing method including the step of forming the protective film (B) by extrusion laminating (EL: Extrusion Laminate) a resin melt as a raw material. The manufacturing method of the optical film with a protective film which manufactures the optical film with a protective film of any one of 1) to (10).
(12) After removing the distortion of the protective film (B) by heating the protective film (B), a molten resin layer as a raw material is laminated and cooled on the protective film (B) and cooled. The manufacturing method of the optical film with a protective film which manufactures the optical film with a protective film of any one of said (1) to (10) with the manufacturing method which has the process of forming the said optical film (A) by.

The present invention also provides
(13) The optical film with a protective film according to any one of (1) to (10) is subjected to at least one of a heat treatment, a stretching treatment, and a relaxation treatment, and the optical film ( A method for producing an improved optical film with a protective film, comprising the step of improving the electrical properties, mechanical properties, and / or optical properties of A).
(14) The method for treating an optical film with a protective film according to (13), wherein the treatment is a stretching treatment, and the stretching treatment is simultaneous biaxial stretching.

  By using the optical film having the structure of the present invention, for example, even a wide optical film having a width of 2 m or more can be uniformly bonded without any defects such as air entrapment between the protective film and effective for large display applications. In addition, it is possible to cope with a wide optical film, which is expected to lead to cost reduction of the optical film member.

Furthermore, there is substantially no adhesive residue even when the protective film is delaminated, and it is expected to be used as a high-grade optical film member.
Moreover, the peeling band voltage at the time of delamination of the protective film is very low, and it is expected that the protective film can be effectively used for the next generation liquid crystal driven even at a low voltage.

  Furthermore, in the past, the release-coated PET film coated with silicon was peeled off from the PET film subjected to adhesive processing, and the adhesive PET film was superposed on the optical film. By using the optical film of the present invention, It is expected that two PET films are unnecessary, the manufacturing process is greatly simplified, and the production cost can be greatly reduced.

Furthermore, if necessary, the optical film on which the protective film is bonded can be directly supplied to a heating furnace such as a tenter to perform stretching or relaxation treatment with the protective film attached, and a high-quality retardation film. Manufacturing is also expected to be possible.

  In the optical film in which the protective film (B) is laminated on at least one surface of the optical film (A), the width of the optical film (A) is preferably 2 m or more, more preferably 2.5 m or more. Preferably, the optical film is excellent in productivity of 3 m or more, and is an optical film with a protective film in which an adhesive layer is not substantially present at the interface between the optical film (A) and the protective film (B). And the thickness unevenness measured over the width direction of the optical film (A) is an optical film with a protective film of 5% or less, and the delamination between the optical film (A) and the protective film (B) The force is 10 to 300 g / 25 mm width, preferably 15 to 150 g / 25 mm width. If the delamination force is less than 10 g / 25 mm, the protective film may peel off from the optical film when an external force is applied, such as when the optical film is running, transported, or even during cutting. This is because when the strength exceeds 300 g / 25 mm, the optical film may be wrinkled or damaged when the protective film is peeled off.

  The optical film (A) constituting the present invention includes an acrylic resin, a cyclic olefin resin, a polystyrene (PSt) resin excellent in transparency, a polycarbonate resin, a polyester resin, a polymaleimide resin, and syndiotactic. It is preferable to comprise at least one resin selected from the group consisting of polypropylene (SPP) resins.

  The optical film (A) constituting the present invention is a film having a light transmittance at a wavelength of 550 nm of 88% or more and a haze value of 1.5% or less when converted to an optical film thickness of 100 μm. There are no particular limitations on the optical film (A), and various transparent films can be appropriately used as long as the above conditions are satisfied.

The light transmittance at a wavelength of 550 nm when converted to an optical film thickness of 100 μm of the optical film (A) is preferably 90% or more, and the haze value is preferably 1.0% or less. When the optical film (A) is used as an optical isotropic film, the in-plane optical retardation value Re at a wavelength of 589 nm is preferably 10 nm or less, more preferably 5 nm or less, and retardation in the thickness direction. The value R _th is preferably 15 nm or less, more preferably 10 nm or less, particularly preferably 5 nm or less. When using an optical film (A) as a retardation film, of course, it varies depending on the application, by changing the conditions of stretching while adhering a protective film, for example, as Re value 30-60 nm, as R _th value 100- An optical film with a value of 250 nm is preferably used. This is because when the value is higher than this, it may cause display defects such as coloring or rainbow pattern when used as a liquid crystal display member.

In order to obtain such optical homogeneity, it is effective that the thickness unevenness measured in the width direction of the optical film (A) is 5% or less (peak to peak). More desirably, the thickness unevenness in the length direction of the optical film and in the width direction (for example, over 2 m width or more) are both 3% or less, preferably 2% or less. In order to obtain such strict thickness uniformity, co-extrusion methods such as Patent Document 1 and Patent Document 2, which are known examples, are not necessarily appropriate. This is because the thickness control of the coextruded film is to make the total thickness of each layer uniform, not to each individual layer, and when a part of the layers is peeled off, the thickness accuracy is remarkably lowered. In this method, since at least one of the optical films (A) and (B) is formed separately, the thickness unevenness can be suppressed by a known method. For example, an in-line thickness gauge with an accuracy that is finer than the upper limit of the thickness unevenness for each base material can be measured in the width direction, and from the base position corresponding to the thickness of the base material position in the width direction. For example, the molten resin discharge amount may be increased or decreased by an automatic flow rate adjusting mechanism such as a heat bolt. In addition, the thickness unevenness of an optical film (A) is the thickness unevenness of the optical film (A) before extrusion-laminating and forming a protective film (B) layer.

  Furthermore, the glass transition temperature Tg of the optical film (A) is 120 ° C. or higher, preferably 125 ° C. or higher, more preferably 130 ° C. or higher. This has not only stable dimensional stability even under severe use environment such as automotive applications that are likely to be exposed to high temperatures of about 60 ° C, but also component load tests (85 ° C, 65RH%, 500 hours, and 105 ° C) , 0 RH%, 500 hours), it is desirable to have stable dimensional stability.

Furthermore the center line average surface roughness R _a of the optical film (A) is, 100 nm or less, preferably 50nm or less, and more preferably is 20nm or less. This is because when used as a liquid crystal display member, surface roughness may cause distortion of the image, or the image may be blurred when observed from an oblique direction. To the center line average surface roughness R _a of the optical film (A) and 100nm or less, the molten resin discharged from the die, so as to solidify the surface roughness is brought into contact with the cooling drum surface was Ry = 0.1 or less You can do it.

  Furthermore, the surface wetting tension of at least one surface of the optical film (A) is 40 mN / m or more, preferably 45 mN / m or more. This is a suitable condition for obtaining strong adhesiveness at the interface between the optical film (A) constituting the present invention and another optical member such as a polarizer. In order to set the surface wetting tension of the optical film (A) to 40 mN / m or more, the substrate surface may be subjected to treatment such as plasma or corona discharge, which can be adjusted by the treatment atmosphere, discharge voltage, current value, treatment time, etc. It is.

Furthermore, the surface specific resistance value of the optical film (A) is 10 ¹² Ω / □ or less, preferably 10 ¹⁰ Ω / □ or less, preferably 10 ⁸ Ω / □ or less. This is because the optical film (A) constituting the present invention is effective for avoiding peeling electrification in steps such as transporting and peeling, and preventing dust and dust from being adsorbed. In order to set the surface resistivity of the optical film (A) to 10 ¹² Ω / □ or less, the antistatic agent may be kneaded into the base material or coated on the base material surface.

  As a resin preferably used as a material constituting at least a part of the optical film (A) of the present invention, acrylic resin, cyclic olefin resin, methylpentene resin, polystyrene (PSt) resin excellent in transparency, polycarbonate Examples thereof include optical resins selected from a series resin, a polyester series resin, a polymaleimide series resin, a syndiotactic polypropylene (SPP) series resin, and the like.

Cyclic olefin resins include various COPs including hydrides of ring-opening polymers of dicyclopentadiene, various COCs including copolymers of dicyclopentadiene or tetracyclododecene and ethylene, and hydrides thereof. And at least one selected from norbornene polymers and the like, and those having a glass transition point of 100 ° C. or higher, preferably 130 ° C. or higher are preferable. A hydride of a ring-opening polymer of dicyclopentadiene is well known in Japanese Patent Publication No. 58-43412 and Japanese Patent Laid-Open No. 63-218727. A copolymer of dicyclopentadiene and ethylene is also known in JP-A-63-331420 and the like, and norbornene-based polymers are described in U.S. Pat. No. 2,883,372 and JP-B-46-14910. As disclosed in, for example, Japanese Laid-Open Patent Publication No. 1-149738, a polymer obtained by obtaining a polycyclic norbornene compound having four or more rings from a mixture of dicyclopentadiene and dienophile is known. Of course, the dicyclopentadiene may also include alkyl substituents such as methyl and ethyl substituents, endo isomers, taxo isomers, and mixtures thereof. The cyclic polyolefin has a number average molecular weight of 30,000 or more and less than 70,000, preferably 35,000 or more and less than 60,000, from the viewpoint of the mechanical strength of the film, particularly impact properties and extrusion molding.

  The methylpentene resin is a copolymer of 4-methylpentene-1 homopolymer homopolymer and a comonomer having an arbitrary length such as carbon number 5, 8, 10, 12, 20 or the like, and is copolymerized to about 2 to 20 mol%. The main ones of these are commercially available from Mitsui Chemicals, Inc. as TPX (registered trademark).

The polymaleimide resin is a resin represented by those described in JP-A-2000-294042, JP-A-2006-70134, etc., and an N-substituted maleimide / olefin copolymer developed by Tosoh Corporation, and Examples thereof include resins to which butadiene / styrene copolymer rubber particles, graft-modified 1,3-butadiene / styrene copolymer rubber obtained by grafting styrene / acrylonitrile copolymer are added.

  The polystyrene (PSt) resin is a polymer compound having a group derived from styrene in the basic skeleton, and as the tacticity, a polymer mainly composed of an atactic polymer is preferable because of its excellent transparency. In a range that does not impair transparency, that is, a polystyrene containing isotactic polystyrene or syndiotactic polystyrene within a range in which the light transmittance is maintained at a value of 88% or more when the film has a thickness of 80 μm, Further, it may be copolymerized with another monomer such as ethylene group in an amount of about 20 mol% or less. It is commercially available from PS Japan. In addition, the polystyrene resin excellent in transparency in this invention means the polystyrene resin whose light transmittance in wavelength 550nm is 88% or more, when it is set as a 80-micrometer-thick film.

The acrylic polymer (resin) is a polymer typified by polymethyl methacrylate (PMMA), polymethacrylate, and the like, and is an optically transparent polymer having a high light transmittance including these copolymers. Moreover, as disclosed in JP-A-2006-265543, a glutaric anhydride unit-containing copolymer obtained by subjecting a carboxyl group-containing acrylic copolymer to a cyclization reaction has a high glass transition temperature Tg. In addition, it has high heat resistance, colorless transparency, excellent heat processing stability and molding properties, and also reduces foreign matter, and has high colorless transparency and low foreign matter acrylic required for optical materials. Since it becomes a polymer, it can be used effectively for the film constituting the present invention. Of course, a polymer in which acrylic rubber is dispersed to impart toughness, for example, an acrylic resin having a glutaric anhydride unit as shown in Japanese Patent Application Laid-Open No. 2006-283013, is refracted with the acrylic resin. A polymer containing acrylic elastic particles having a rate difference of 0.05 or less and a particle diameter of 1 μm or less is also effective.
Furthermore, an acrylic resin having a lactone ring and a glass transition temperature Tg of 120 ° C. or higher as disclosed in JP-A-2007-63541 or a polysiloxane disclosed in JP-A-2006-27090 is disclosed. An acrylic resin blended with lactic acid is preferably used.

  Polycarbonate resin is a polyester of carbonic acid and glycol or dihydric phenol, and is a polymer having a carbonate bond of -O-CO-O-, and a polymer of bisphenol and carbonate is most practically used. , Teijin Limited (Panlite (registered trademark), Pure Ace (registered trademark)), Kaneka Corporation (Elmec (registered trademark)), Mitsubishi Engineering Plastics (Iupilon (registered trademark)), and the like. Of course, a polymer obtained by copolymerizing a monomer having a fluorene group (for example, see Japanese Patent Application Laid-Open No. 2005-189632) exhibits reverse wavelength dispersion of retardation, and such a polycarbonate is also preferably used depending on the application. be able to.

Examples of the polyester resin include polyethylene terephthalate and polyethylene naphthalate.
The syndiotactic polypropylene (SPP) resin may be a propylene homopolymer or a copolymer of propylene and a small amount of other α-olefin. In the case of a copolymer, the propylene content is preferably 95 mol% or more, particularly 97 mol% or more. Syndiotacticity as seen by propylene triad chain is 0.6
The melt flow rate (230 ° C., 2.16 kg load) is preferably 0.1 to 50 g / 10 min.

  In the optical film (A) constituting the present invention, any known additive such as an anti-coloring agent, an antioxidant, an antistatic agent, a thermal stabilizer, a crystal nucleating agent, an adhesion improver, a slipping agent, and an anti-blocking agent. Agents, anti-foaming agents, antifoaming agents, clearing agents, viscosity modifiers, and the like may be included. Known antistatic agents such as dodecylbenzenesulfonate, bis (octylpolyoxyethylene) phosphate soda, phosphonium dodecylbenzenesulfonate, alkylsulfonate, phosphonium alkylsulfonate, styrenesulfonate, polyethylene glycol, etc. However, it is not limited to these. It is preferable to use an antistatic agent having moisture permeability as an additive because it is excellent in antistatic stability during drying and over time. Here, as an antistatic agent having moisture permeability, an ionomer having an ionic group selected from alkali metals such as potassium (K), rubidium (Rb), cesium (Ce), lithium (Li), and sodium (Na). In the present invention, the inclusion of a polymer containing potassium (K) ions is particularly preferred in terms of moisture permeability, compatibility and transparency of the film. Typical examples of moisture permeable ionomers include polystyrene sulfonate (PSS) ionomer, ethylene sulfonate ionomer, and ethylene / unsaturated carboxylic acid ionomer. Typical polymers are commercially available from Mitsui DuPont Polychemical Co., Ltd. ENTILA (trade name) is particularly excellent. Of course, a compatibilizer may be used at the same time. The addition amount of these antistatic agents is 20% or less, preferably 10% or less, more preferably 5% or less in terms of weight in terms of transparency and bleed-out properties.

Next, the protective film (B), which is another component of the present invention, will be described.
Here, the protective film (B) refers to a film that is not used as an optical member that finally constitutes a liquid crystal display or the like, but protects the optical film from dust and scratches in the manufacturing process. . The protective film (B) has a water vapor transmission rate of 20 (g / m ² · day /
0.1 mm) or more is preferable. Other preferable properties include an optical film (A
The coefficient of friction of the surface of the protective film (B) on the side in contact with) is 1 or less, preferably 0.6 or less. When the friction coefficient cannot be measured at all (the friction coefficient is infinite), or when the friction coefficient exceeds 2, for example, when the protective film has a wide width of 2 m or more, the moment when it contacts the optical film, Since the protective film does not slip, the air layer interposed between the protective film and the optical film cannot be removed at the time of bonding, and a phenomenon such as air entrainment may occur, and there is a possibility that uniform bonding cannot be performed. In addition, the friction coefficient of the surface of a protective film (B) is a friction coefficient of the surface of the protective film (B) before extrusion-laminating and forming an optical film (A) layer.

Next, as the characteristics of the protective film (B) constituting the present invention, the surface specific resistance value at 23 ° C. and 50 RH% is 10 ¹¹ Ω / □ or less, preferably 10 ¹⁰ Ω / □ or less, more preferably 10 ^9. An optical film of Ω / □ or less is desirable. This is not only to prevent dust from being adsorbed, but also to prevent the occurrence of peeling charge from the optical film as much as possible. The surface specific resistance value of the protective film (B) can be set to the above range by blending, for example, a moisture-permeable polymer in an amount described later.

  The surface wetting tension on the side of the protective film (B) that does not contact the optical film is 35 mN / m or less, preferably 32 mN / m or less. This is to prevent adhesion of an adhesive material or a fingerprint. On the other hand, the surface wetting tension of the surface in contact with the optical film varies depending on the manufacturing conditions and the desired delamination force. If a larger delamination force is desired, if necessary, the protective film (B) before bonding Adhesive strength can be adjusted by surface activation treatment or the like on the surface.

Further, the water vapor permeability of the protective film (B) constituting the present invention is 20 (g / m ² · day / 0.1 mm) or more, preferably 30-120 (g / m ² · day / 0.1 mm). It is desirable that the film has excellent water vapor permeability. If it is a protective film having only a water vapor transmission rate smaller than this, water cannot be dried from the film cross section at the time of bonding in the case of using a water-based adhesive for adhesion between the optical film (A) and the PVA polarizer, There is a possibility that defects such as blisters occur at the interface between the protective film (B) and the optical film (A), the degree of polarization of the PVA polarizer decreases, or black spots appear on the polarizer. The water vapor transmission rate of the protective film (B) can be set to the above range by, for example, blending a moisture-permeable polymer in an amount described later.

  Furthermore, the thickness unevenness measured over the width direction of, for example, 2 m or more of the protective film (B) constituting the present invention is 5% or less, preferably 3% or less, more preferably 2% or less. The film thickness unevenness not only leads to optical retardation unevenness but may also cause lamination unevenness at the time of bonding. Therefore, it is preferable to satisfy the above conditions in order to prevent these. In order to reduce the thickness unevenness measured across the width direction of the protective film (B) to 5% or less, an in-line thickness gauge having an accuracy that is about an order of magnitude finer than the upper limit of the thickness unevenness can be measured across the width direction, There is a method of increasing or decreasing the amount of molten resin discharged from the corresponding base position according to the thickness of the base material position in the width direction by an automatic flow rate adjusting mechanism such as a heat bolt. The thickness unevenness of the protective film (B) is the thickness unevenness of the protective film (B) before extrusion lamination to form the optical film (A) layer.

Furthermore, the breaking strength of the protective film (B) constituting the present invention is desirably 20 MPa or more, preferably 40 MPa or more, and more preferably 100 MPa or more. Since the rupture strength of olefin-based films, which are usually called protective films, is often less than 18 MPa, when a wide protective film of 2 m or more is pasted on an optical film, the protective film is loose and wrinkles occur. However, if the protective film (B) has a large strength such as 20 MPa or more, it is difficult to bite air and air, although it is difficult to evenly bond air and wrinkle-free evenly. It is preferable because it can be bonded evenly.

  Furthermore, the variation in the in-plane retardation values in the longitudinal direction and the width direction of the protective film (B) constituting the present invention is preferably 5 nm or less, and more preferably 3 nm or less. Further, the absolute value of retardation is preferably 5 nm or less, preferably 2 nm or less because of excellent optical homogeneity. This is because if the optical unevenness of the protective film is detected in the inspection stage when used as a liquid crystal display member, the inspection may be adversely affected.

Furthermore, it is preferable that the optical foreign-material defect which exists in the protective film (B) which comprises this invention is not detected by a polarizing plate inspection process. Specifically, the foreign matter defect of 100 μm or more is preferably 1 piece / m ² or less and the foreign matter of 40 μm or more and less than 100 μm is 10 pieces / m ² or less. Furthermore, it is also preferable that no defects are detected when the protective film is placed under crossed Nicols.

  Furthermore, as a polymer preferable as a material constituting at least a part of the protective film (B) constituting the present invention, linear low density polyethylene (LLDPE), polypropylene (PP), and modified polyolefins and polyesters thereof are modified products. , As well as polymers selected from the group consisting of polycarbonates alone, or blends thereof. A film comprising these various polymers can be used in a single layer or in a laminate. These protective films may be unstretched or may be stretched and heat-treated uniaxially or biaxially as necessary. Stretching increases the rigidity and strength of the protective film, improves thickness uniformity, increases stability over time, and corrects the shape such as film flatness even if the dimensions change over time. It may be preferable because it is easy to do.

  In the case of the film (B) constituting the present invention, as a function of the protective film, an antifouling property that prevents the adhesive paste from being transferred to the protective film is essential, but in a polyolefin film such as LLDPE or PP, This antifouling function is a function that is inherent to the polymer itself, so no special surface treatment is required, but the film is not necessarily adequate for antifouling properties such as polyester film and polycarbonate film. From this point of view, as a protective film (B) constituting the present invention, there is a drawback that it is necessary to impart an antifouling function and thus there is a disadvantage that the price as a protective film is high. Polyolefin films are preferred. Furthermore, the protective film (B) constituting the present invention is often required to have an antistatic function in order to prevent dust from being adsorbed or to prevent peeling. In order to impart this function, there is a method of modifying the protective film such as coating, but considering productivity, a method of sheeting after kneading a polymer antistatic agent is preferable. In particular, a method using a specific ionomer is particularly effective as a method for imparting not only an antistatic function but also moisture permeability.

Such a film is obtained by, for example, mixing a moisture-permeable polymer containing a specific metal ion in a matrix polymer with a specific amount and kneading the moisture-permeable polymer containing the metal ion and a compatibilizing agent. Obtainable. The moisture-permeable polymer used for the matrix polymer has a water vapor transmission rate of 1000 (g / m ² · day / 0.1 mm) or more,
A polymer having a large moisture permeability of 2000 (g / m ² · day / 0.1 mm) or more is preferable. As long as the above conditions are satisfied, the type of moisture-permeable polymer is not particularly limited, and various types of moisture-permeable polymers can be used as appropriate, but it is particularly preferable to use metal ion-containing moisture-permeable polymers. The moisture-permeable polymer containing metal ions particularly preferable as the moisture-permeable polymer was selected from alkali metals such as potassium (K), rubidium (Rb), cesium (Ce), lithium (Li), and sodium (Na). It is preferable to use an ionomer polymer having a metal ion group. In the case of the present invention, the inclusion of a polymer containing potassium (K) ions is particularly preferred in terms of moisture permeability, compatibility and transparency of the film. Representative examples of the ionomer polymer having a metal ion group include sulfonate ionomers such as polystyrene sulfonate (PSS) ionomer and ethylene sulfonate ionomer, and ethylene / unsaturated carboxylic acid ionomer.

  Of course, as the moisture-permeable polymer, cellulose triacetate (TAC) having a hydroxyl group (OH), which is a relatively large moisture-permeable resin, polyvinyl alcohol (PVA), cellophane, and polyester ether elastomer having an ether group, ethylene oxide, Propylene oxide or the like can be added to the matrix polymer, but from the viewpoint of obtaining a film or sheet having both high moisture permeability and dimensional stability against humidity, it is preferable to use the above metal ion-containing moisture-permeable polymer. . Accordingly, the moisture-permeable polymer is preferably a polymer containing metal ions as the composition of the present invention, but is not necessarily limited thereto, and an ether compound such as polyethylene glycol is also effective.

The content of the moisture-permeable polymer depends on the required performance, and is not particularly limited. Usually, when the weight of the whole polymer is 100% by weight, it is about 1 to 99% by weight, Preferably it is 5-98 weight%.
(Ethylene / unsaturated carboxylic acid copolymer ionomer)
The ionomer of an ethylene / unsaturated carboxylic acid copolymer that is preferably used as a moisture-permeable polymer containing metal ions means that some or all of the carboxyl groups of the ethylene / unsaturated carboxylic acid random copolymer are alkali metals. It has a unified structure.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic anhydride, monomethyl maleate, monoethyl maleate and the like, and acrylic acid or methacrylic acid is particularly preferable. Other monomers that can be copolymer components include vinyl esters such as vinyl acetate, methyl acrylate, ethyl acrylate, isobutyl acrylate, nbutyl acrylate, isooctyl acrylate, and methyl methacrylate. Examples thereof include saturated carboxylic acid esters and carbon monoxide.

  As the ethylene / unsaturated carboxylic acid random copolymer, the ethylene component is 60 to 90 wt%, particularly 70 to 88 wt%, the unsaturated carboxylic acid component is 10 to 40 wt%, particularly 12 to 30 wt%, It is preferable that the saturated monomer component is copolymerized in a proportion of 0 to 30% by weight, particularly 0 to 20% by weight. Such a copolymer can be obtained, for example, by randomly copolymerizing each polymerization component under high temperature and high pressure. Moreover, as long as the total satisfies the above requirements, two or more types having different unsaturated carboxylic acid component units may be used. The ionomer ion source is preferably an alkali metal, that is, lithium, sodium, potassium, rubidium, or cesium, with potassium being particularly preferred. Examples of the unsaturated carboxylic acid component in the ionomer include acrylic acid, methacrylic acid, fumaric acid, maleic acid monomethyl ester, maleic acid monoethyl ester, and maleic anhydride. The alkali metal cation content in the ionomer is desirably 0.4 to 4 mol, preferably 0.6 to 2 mol, per kg of ionomer.

  As ionomers preferably used in the present invention, those having a melt flow rate at 190 ° C. under a load of 2160 g of 0.01 to 1000 g / 10 min, particularly 0.1 to 100 g / 10 min are preferably used. In particular, ENTILA (trademark) SD100, MK400, MK153 manufactured by Mitsui DuPont Polychemical Co., Ltd. and the like are particularly preferable examples.

(Sulfonate ionomer)
The sulfonate ionomer preferably used as a moisture-permeable polymer containing metal ions is a polymer ionomer containing a sulfonate, and typical examples include polystyrene sulfonate (PSS) ionomer and ethylene sulfonate ionomer. There is. As the H substituent of sulfonic acid, metal cations such as alkali metals, alkaline earth metals, and transition metals can be preferably used. By incorporating hydrophilic compounds such as polyhydric alcohols and ether compounds such as polyoxyethylene glycol, ethylene oxide, and propylene oxide into these moisture-permeable ionomers, effects such as further improvement in moisture permeability can be expected. Examples of the polyhydric alcohol include hydrocarbon compounds having three or more hydroxyl groups in the molecule, but they may be compounds composed only of carbon, hydrogen and oxygen, in addition to carbon, hydrogen and oxygen. Further, it may contain a hetero atom such as nitrogen. These usually have a molecular weight of 400 or less, preferably 80 to 300, and may be liquid or solid at room temperature. The molecular weight may exceed 400, but the effect of improving moisture permeability is small.

Specific examples of such polyhydric alcohol compounds include glycerol, diglycerol, trimethylolpropane, pentaerythritol, 1,1,1-tris (hydroxylmethyl) ethane, and 2,2-di (hydroxymethyl) -1, 3-propanediol, sorbitol, 1,3,5-trihydroxybenzene, 1,3,5-trihydroxybenzoic acid, tris (hydroxymethyl) aminopropane, N, N, N ′, N′-tetrakis (2- Hydroxyethyl) ethylenediamine, N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine and the like can be exemplified. Of these, it is most preferable to use an aliphatic polyhydric alcohol such as glycerol or trimethylolpropane.

  Matrix polymers include polyolefin, polystyrene (PSt), polyester, polycarbonate (PC), polymethyl methacrylate (PMMA), polyethersulfone (PES), polysulfone (PSF), polyetheretherketone (PEEK), polyphenylene sulfide. Polymers typified by (PPS) and the like are preferable, such as low density polyethylene (LDPE), linear low density polyethylene homopolymer (LLDPE), polypropylene homopolymer, polypropylene random copolymer, cyclic olefin (COP, COC), and methylpentene polymer. Mention may be made of polyolefins usually used for optical applications such as (PMP).

  The protective film (B) constituting the present invention may be composed only of a matrix polymer and a moisture-permeable polymer, and may further contain one or more other components. Therefore, the protective film (B) may or may not contain a polymer that does not correspond to any of the matrix polymer and the moisture-permeable polymer.

In the protective film of the present invention (B), any known additive such as an anti-coloring agent, an antioxidant, a heat stabilizer, a crystal nucleating agent, an adhesion improver, a slip agent, an anti-blocking agent, and an anti-glare agent Further, an antifoaming agent, a clarifying agent, a viscosity adjusting agent and the like may be contained.
Preferred examples of the antistatic agent include known antistatic agents such as dodecylbenzenesulfonate, bis (octylpolyoxyethylene) phosphate soda, phosphonium dodecylbenzenesulfonate, alkylsulfonate, phosphonium alkylsulfonate, and styrenesulfonate. There is an agent, but it is not limited to these. The addition amount of these antistatic agents is preferably 5% or less in terms of polymer weight from the viewpoint of transparency and bleed-out property.

  Next, although one preferable example of the manufacturing method of the optical film with a protective film of this invention is described, the manufacturing method of the optical film with a protective film of this invention is not limited to this.

  The protective film that has been conventionally used is a composite film in which a pressure-sensitive adhesive is laminated, or a protective film having a pressure-sensitive adhesive layer coated with a pressure-sensitive adhesive. When sticking to an optical film, the air layer is often bitten because the adhesive surface does not slip by all means, and the optical film on which the protective film with such a surface defect is stuck cannot pass the optical inspection process Therefore, there is a drawback that it is difficult to use for optical use.

  In the optical film of the present invention, since the adhesive layer is not substantially present at the interface between the optical film (A) and the protective film (B), the above disadvantages can be effectively eliminated. Hereinafter, a method for providing an optical film with a protective film having a delamination force in the range of 10 to 300 g / 25 mm width without substantially using an adhesive layer will be described.

1. A method of forming a protective film (B) by extrusion laminating (EL: Extrusion Laminate) a resin melt as a raw material on at least one surface of a separately formed optical film (A).
This method has an advantage that it can be put into practical use in that a conventional manufacturing apparatus for laminating a protective film on an optical film, which has been conventionally performed, can be used as it is.

  2. A melt of a resin serving as a raw material on the protective film (B) after the separately formed moisture-permeable protective film (B) is left as it is or after the distortion of the protective film (B) is removed by heating or the like Is a method of forming an optical film (A) layer by extrusion lamination (EL). This method has an advantage that the loss of both films can be reduced because a protective film that has already been manufactured after making the thickness unevenness of the optical film uniform can be inserted into the cast drum.

  3. Using an optical film (optical film with a protective film) obtained by laminating a protective film on at least one surface of the optical film thus obtained, the optical film with the protective film is placed in a heating furnace such as an oven type. Various treatments such as heat treatment, stretching treatment (such as simultaneous biaxial stretching), and relaxation treatment are performed to improve the mechanical properties of the optical film with the protective film, the electrical properties such as static elimination, and / or the optical position. A method for improving optical characteristics such as phase difference adjustment.

(Film formation)
Ultra low molecular volatiles with a molecular weight of less than 100 such as moisture, gas, melt, volatiles, and decomposition products are removed from the matrix polymer to be the protective film (B) or optical film (A), and the content is 0.05 weight. It is preferable to prepare a raw material with less impurities that is less than or equal to%. When it is desired to impart moisture permeability of 20 (g / m ² · day / 0.1 mm) or more as the protective film (B), a moisture permeable compound, for example, an ethylene methacrylate polymer containing potassium ions [ For example, a raw material obtained by adding and mixing ENTILA (registered trademark) manufactured by Mitsui DuPont Polychemical Co., Ltd.] and a compatibilizing agent can be used. The raw material can be melted with a sheet extruder or the like, and after passing through a fine filter as necessary, the molten sheet is discharged from the die and adhered and solidified on the cooling drum to obtain a cast sheet. In this case, it is also possible to laminate with other polymer layers as a laminated sheet. In addition, as a method of cast adhesion, the electrostatic application adhesion method is particularly preferable from the viewpoints of high-speed film formation, defect-free film formation, handleability, and the like. In order to apply the electrostatic adhesion method to such a polymer, the specific resistance at the melting temperature of the resin is required to be a value of about 10 ⁸ to 10 ¹⁰ Ω · cm. When the specific resistance is as high as 10 ¹³ Ω · cm or more, the specific resistance can be adjusted by adding a polymer containing metal ions, particularly preferably the potassium ionomer described above. In this case, there is an advantage that moisture permeability can be imparted to the obtained film as well as electrostatic adhesion.

The production of the optical film with a protective film of the present invention is not limited to the above method, and a nip roll (soft & hard) method, a belt method, a calendar method, an air knife method, an air chamber method, etc. may be used as appropriate. it can. The drum material is preferably a surface drum made of chrome plating, stainless steel or ceramic and having a maximum surface roughness _{Ry of} 0.1 μm or less. The drum surface temperature is preferably close to the glass transition temperature of the polymer, although it depends on the type of polymer. A draft ratio as small as 10 or less is preferable because an optically isotropic film is obtained. It should be noted that heat treatment and stretching may be added according to the relationship with the use of the film and other needs, and a laminate may be produced by co-extrusion or lamination with other polymers. Furthermore, the surface may be modified by coating or the like, and various characteristics may be appropriately added to the surface.
(Example / Comparative Example)
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the Example shown below in any meaning.
(Evaluation method of physical properties)
In the following examples and comparative examples, various physical properties of the films were evaluated according to the following measuring methods.
(1) Water vapor transmission rate Using PERMONRAN-W1A manufactured by mocon, the water vapor transmission rate was measured at 40 ° C. and 90 RH% according to JIS K7129 B method. The unit is expressed as g / m ² · day / 0.1 mm.
(2) Light transmittance Measured using a spectrophotometer U-3410 manufactured by Hitachi, Ltd., the total light transmittance of visible light from a wavelength of 300 nm to 700 nm was measured, and a value at 550 nm was adopted. The unit is expressed in%.
(3) Retardation R
The film birefringence Δn is multiplied by the film thickness d (nm).
For the measurement of in-plane retardation Re, (i) the phase produced by the sample was placed in a polarizing microscope under crossed Nicols with sodium D line (589 nm) as the light source, with the sample film surface perpendicular to the optical axis. refraction deviation R is retardation, or obtains it from the compensation value of the compensator, or (ii) using the sodium D line as the light source, the Abbe refractometer in the same perpendicular direction from the refractive indices n _x in the main axis direction birefringence by subtracting the rate _{n y △ n (= n x} -n y) to be determined by multiplying the thickness d.

For the measurement of the thickness direction retardation R _th, determined according to the following equation seeking refractive indices n _x, n _y and a thickness direction refractive index n _z of the film plane by using the Abbe refractometer.
n _th = [(n _x + _ny ) / 2] −n _z
The unit is nm.
(4) Surface resistance A main electrode (50 mmφ), a main electrode when a voltage of 1 kV is applied by inserting a film between a guard electrode (inner diameter 70 mmφ, outer diameter 80 mmφ) concentric with the main electrode and a counter electrode (80 mmφ) The resistance was obtained from the value of the current flowing from the electrode to the guard electrode, and this was multiplied by 60π to obtain the surface resistance. The measurement was performed at 23 ° C. and a humidity of 60%. The unit is represented by Ω / □.
(5) Surface roughness Ra
According to JIS B0601, it measured using the high precision thin film level | step difference meter ET-10 made from a Kosaka laboratory. The measurement conditions were a stylus tip radius of 0.5 μm, a needle pressure of 5 mg, a measurement length of 1 mm, and a cutoff of 0.08 mm. The centerline average roughness Ra is obtained by dividing the area of the difference obtained by subtracting the area of the component shifted vertically from the centerline of the roughness curve by the measurement length and adding the value to the centerline. The unit is expressed in nm.
(6) Haze Total haze was determined according to the method of JIS K6782. The unit is expressed in%.
(7) Film thickness Measured by the micrometer method according to JIS K7130 A method. The unit is expressed in μm.
(8) Thickness unevenness Using a film thickness tester “KG601A” manufactured by Anritsu Co., Ltd., a film sampled 20 m long in the longitudinal direction of the film, and continuously measuring a thickness of 2 m or more in the width direction. The conveyance speed of the film was 3 m / min. Maximum thickness T _max (μm) at the measurement length
From the minimum value T _min (μm),
R = T _max −T _min
From the average thickness T _ave (μm) of R and measurement length, thickness unevenness (%) = R / T _ave × 100
As sought.
(9) Surface tension Measured by the wetting tension measurement method of JIS C2151 (2006). The unit is represented by mN / m.
(10) Glass transition temperature Tg
As a scanning calorimeter DSC, a robot DSC “RDC22” manufactured by Seiko Electronics Industry Co., Ltd.
0 ”was used as a data analysis device, and a disk station“ SSC / 5200 ”manufactured by the same company was used. About 5 mg of a sample was placed in an aluminum tray and heated from room temperature at 20 ° C./min. The arithmetic average value of the deviation start temperature and end temperature from the baseline based on the transition from the glass state to the rubber state observed at this time was defined as the glass transition point (Tg).
(11) Interlaminar peeling force Using a universal tensile tester “TCM-1kNB” manufactured by Minebea Co., Ltd., 180 ° peel, peeling rate of 300 mm / min, 23 ° C., 60% RH atmosphere.
(12) Breaking strength Measured by the method defined in JIS K7127 (13) Foreign matter Two polarizing plates are arranged in an orthogonal state (crossed Nicols) to block transmitted light, and a sample is placed between the two polarizing plates. Put. Irradiate light from one side and diameter 1 cm ^{2 with an} optical microscope from the other side
The number of foreign matters of 00 μm or more and foreign particles of 40 μm or more and less than 100 μm were counted.
(14) Separation withstand voltage The laminated film was cut into a size of 70 mm in width and 100 mm in length, one end of either film was gripped, and set in a simple winder, with a peeling angle of 150 °, Peeling was performed at a peeling speed of 3 m / min. The potential of the film surface generated at this time was measured with a potential measuring device (KSD-0103, manufactured by Kasuga Denki Co., Ltd.). The measurement was performed in an environment of 23 ° C. × 50% RH.
(15) Friction coefficient Using a slip tester manufactured according to ASTM-D1894-63, the friction coefficient (μs) between films under the conditions of a load of 200 g, a contact area of 63.5 × 63.5 mm, and a moving speed of 150 mm / min. ).

Example 1
Polypropylene polymer PP (Prime Polypro F300SP manufactured by Prime Polymer Co., Ltd.) is used as the polymer for the protective film, and ethylene acrylic acid potassium ionomer (Entila (trademark) MK400: Mitsui DuPont Polychemical Co., Ltd.) is used as the moisture permeable polymer. Polyethylene glycol having a molecular weight of 4000 was used as a compatibilizing agent. A uniform mixture having a composition of 80% by weight of a moisture-permeable polymer with respect to 20% by weight of the PP polymer was dried at 105 ° C. for 4 hours in a stirring heating tank. Thereafter, this was supplied to an extruder hopper, melted at 280 ° C. in the extruder, and foreign matter was filtered and discharged from the die. The melt was pressed against a chromium plating cooling drum at a static pressure of 25 ° C. in an air chamber and cooled, and then the protective film (B1) was wound up. The thickness of the protective film (B1) was 25 μm, and the film width was 2.4 m. The physical properties of the protective film thus obtained are as follows.

Water vapor transmission rate 70 (g / m ² · day · / 0.1 mm)
Light transmittance 89 (%)
Haze 4.6 (%)
Thickness variation of 2.4m in width direction 1.8 (%)
Retardation R 1 (nm)
Centerline average roughness Ra 60 (nm)
Surface tension 37 (mN / m)
Surface specific resistance 10 ¹⁰ (Ω / □)
Coefficient of friction (surface in contact with optical film) 0.4
Breaking strength 45 (MPa)
Foreign matter 100 μm or more 0 (pieces / m ² )
40 μm or more and less than 100 μm 5 (pieces / m ² )
Next, an acrylic polymer (manufactured by Daicel Degussa, Inc., PLEXIGLAS (registered trademark) hw55 high heat resistance grade, Tg: 122 ° C.) was used as the polymer for the optical film (A1). The polymer was dried at 95 ° C. for 4 hours, supplied to a vented extruder and melted at 280 ° C., water and monomers were sucked from the vent port, foreign matter was filtered, and then discharged from the die. The acrylic melt was used by a known technique of extrusion melt lamination (EL) on the opposite side of the drum surface of the 25 μm protective film (which is in contact with the cooling drum surface) already formed. As a means, instead of pressing with a roll, it was applied to the surface of the melted optical film by an electrostatic charge pinning method and adhered and laminated. For pinning, a negative DC voltage of 12,000 V and a current value of 3 mA were applied and brought into close contact with a mirror-finished chromium plating roll at 25 ° C., and then the optical acrylic film surface was immediately placed near the glass transition temperature Tg of the film. Heating with hot air of 120 ° C. improves the mechanical properties of the optical film (A), cools after static elimination treatment, winds up the film, and forms an optical acrylic film (A1) having a thickness of 40 μm and a width of 2.3 m. An optical film (1) with a protective film having a thickness of 65 μm and a width of 2.3 m was obtained, in which the protective film (B1) having a thickness of 25 μm was adhered.
The film characteristics of the optical film (A1) itself obtained by peeling off the protective film (B1) from the optical film with protective film (1) thus obtained were as follows.

Delamination force 35 (g / 25mm)
No peeling band voltage Glass transition temperature Tg 122 (° C)
Light transmittance 92 (%)
Haze 0.8 (%)
2.3m thickness unevenness in the width direction 2.0 (%)
In-plane retardation Re 1 (nm)
Out-of-plane retardation Rth 3 (nm)
Centerline average roughness Ra 15 (nm)
Surface tension 46 (mN / m)
Surface specific resistance 10 ¹² (Ω / □)
Foreign matter 100 μm or more 0 (pieces / m ² )
40 μm or more and less than 100 μm 1 (piece / m ² )
Water vapor transmission rate 25 (g / m ² · day · / 0.1 mm)
In order to confirm the practical value of the optical film (1) with a protective film comprising the protective film (B1) and the optical acrylic film (A1) of the present invention, for example, the value as a protective film of a polarizer, the following lamination is performed. A polarizing plate was created and evaluated.

  A coater is used to apply a polyvinyl alcohol PVA-based water-based adhesive to the optical film surface (A1) of the optical film (1) with a protective film of the present invention, and this is bonded to both surfaces of the polyvinyl alcohol PVA polarizer. A five-layer film consisting of protective film (B1) / optical acrylic film (A1) / adhesive / PVA polarizer / adhesive / optical acrylic film (A1) / protective film (B1) is dried as it is with hot air at 85 ° C. It was.

  Appearance state at the time of bonding of the five-layer laminated film comprising the obtained protective film (B1) / optical acrylic film (A1) / PVA polarizer / optical acrylic film (A1) / protective film (B1) of the present invention When evaluated according to the following criteria, no surface defects such as curl, wrinkles and spots were observed.

  In addition, when the appearance of the obtained 5-layer laminated film was allowed to stand for 500 hours under high humidity of 23 ° C. and 85 RH%, no changes such as curling, wrinkles, and coloring were observed in the appearance. It was.

Further, when the protective film (B1) was peeled off from the five-layer laminated film, peel resistance was hardly generated.
Thus, it turns out that the optical film with a protective film of this invention shows the characteristic outstanding also as a protective film of a polarizing plate, for example. In addition, since the optical film with a protective film of the present invention is excellent in antistatic properties, it is possible to relatively easily obtain a clean optical film (A) having no surface defects by suppressing the adhesion of dust. . Therefore, the optical film (A) constituting a part of the present invention is suitably used as a liquid crystal member, for example, a protective film such as a polarizing film, a retardation film, a compact disk, a video disk, an optical card, and the like. .

(Comparative Example 1)
Instead of the protective film (B1) used in Example 1, a commercially available unstretched cast polypropylene film CPP having a water vapor transmission rate of 1 (g / m ² · day · / 0.1 mm) (
Except for using C1), a five-layer film was prepared in the same manner as in Example 1. The water-based adhesive was applied, and the black color of the polarizer was dried during the drying process. Defects in the appearance such as the entrapment of bubbles were observed, and it could not be used as a protective film for a polarizer.

Furthermore, the thickness unevenness of the optical film was only as large as 8%.
The characteristics of this commercially available CPP film (C1) were as follows. Water vapor permeability 0.5 (g / m ² · day · 0.1 mM), light transmittance 70%, a haze 8 (%), 12% the width direction of the thickness unevenness, there are many 100μm or more foreign bodies It was.

(Comparative Example 2)
The acrylic polymer for the optical film (A1) used in Example 1 and the olefin resin for the protective film (B1) are converted into a protective film (B1 ′) / optical acrylic film (A1 ′) by a known coextrusion method. A two-layer laminated film was formed. A 65 μm-thick film (1 ′) consisting of a protective film (B1 ′) of 25 μm and an optical acrylic film (A1 ′) of 40 μm was obtained. The delamination force was as strong as 50 g / 25 mm, but when the thickness unevenness in the width direction of the optical acrylic film (A1 ′) was measured after peeling it, a thickness distribution as large as 15% was present. Therefore, it is difficult to use such a film having a large thickness unevenness, that is, a film having a large retardation R as an optical film.

(Example 2)
As a polymer constituting the optical film (A2), cyclic olefin polymer COC (Appel 6015T, Tg 145 ° C., Mitsui Chemicals, Inc.) 74% by weight as a moisture permeable polymer, ethylene acrylic acid type potassium ionomer (“ENTILA” MK400: Mitsui) A polymer mixture containing 25% by weight of DuPont) and 1% by weight of polytetramethylene glycol having a molecular weight of 6000 as a compatibilizing agent was used. The mixture was dried in a stirred heating tank at 105 ° C. for 4 hours and used as a raw material.

  On the other hand, as the protective film, the protective film (B1) used in Example 1 was used to obtain a two-layer film in which the protective film (B1) was laminated on the optical film (A2) in the same manner as in Example 1. . The friction coefficient of the protective film (B1) (surface in contact with the optical film (A2)) was 0.45.

  Thus, a composite film (protective film) having a thickness of 55 μm and a width of 2.6 m in which the optical COC film (A2) having a thickness of 30 μm and a width of 2.6 m and the protective PP film (B1) having a thickness of 25 μm are in close contact with each other. An optical film (2)) was obtained. Thereafter, the laminated film was heat-treated at 135 ° C. near the Tg of the optical film to improve the mechanical properties of the optical film (A), and subjected to slow current treatment.

The film properties of the optical film (A2) itself obtained by peeling off the protective film (B1) from the composite film (2) thus obtained were as follows.
Delamination force 25 (g / 25mm)
No peeling withstand voltage generation Glass transition temperature Tg 145 (℃)
Light transmittance 91 (%)
Haze 0.8 (%)
In-plane retardation Re 1 (nm)
Out-of-plane retardation Rth 2 (nm)
Centerline average roughness Ra 10 (nm)
Surface tension 40 (mN / m)
Surface specific resistance 10 ⁹ (Ω / □)
Foreign matter 100 μm or more 0 (pieces / m ² )
40 μm or more and less than 100 μm 1 (piece / m ² )
Water vapor transmission rate 25 (g / m ² · day · / 0.1 mm)
Thickness variation of 2.6m in the width direction 1.0 (%)

Claims (14)

  In the optical film with a protective film in which the protective film (B) is laminated on at least one surface of the optical film (A), an adhesive layer is substantially formed at the interface between the optical film (A) and the protective film (B). The optical film with a protective film which does not exist and the thickness unevenness measured over the width direction of the optical film (A) is 5% or less.   The optical film with a protective film according to claim 1, wherein the delamination force between the optical film (A) and the protective film (B) is 10 g / 25 mm width to 300 g / 25 mm width.   The optical film with a protective film according to claim 1 or 2, wherein the width of the optical film with the protective film is 2 m or more.   The optical film (A) is an acrylic resin, a cyclic olefin resin, a methylpentene resin, a polystyrene resin having excellent transparency, a polycarbonate resin, a polyester resin, a polymaleimide resin, and a syndiotactic polypropylene resin. The optical film with a protective film according to any one of claims 1 to 3, comprising at least one resin selected from the group consisting of resins.   The optical film with a protective film of Claim 4 whose glass transition temperature (Tg) of the said optical film (A) is 120 degreeC or more.   The optical film with a protective film according to any one of claims 1 to 5, wherein a friction coefficient of a surface of the protective film (B) on a side in contact with the optical film (A) is 1 or less. The optical film with a protective film according to any one of claims 1 to 6, wherein the protective film (B) has a surface resistivity of 10 ¹¹ Ω / □ or less. The optical film with a protective film according to any one of claims 1 to 7, wherein the protective film (B) has a water vapor transmission rate of 20 (g / m ² · day / 0.1 mm) or more.   The optical film with a protective film according to any one of claims 1 to 3 and 5 to 7, wherein the thickness unevenness measured in the width direction of 2 m or more of the protective film (B) is 5% or less. .   The protective film (B) comprises at least one resin selected from the group consisting of linear low density polyethylene (LLDPE), polypropylene, and modified polyolefins, polyesters, and polycarbonates thereof. Item 9. The optical film with a protective film according to any one of Items 1 to 8.   The manufacturing method which has the process of extrusion-laminating the melt of resin used as a raw material on at least one side of the optical film (A) to form the protective film (B), according to any one of claims 1 to 10. The manufacturing method of the optical film with a protective film which manufactures the optical film with a protective film of description.   After removing the distortion of the protective film (B) by heating the protective film (B), a molten resin layer as a raw material is laminated on the protective film (B) and cooled to cool the optical film (B). The manufacturing method of the optical film with a protective film which manufactures the optical film with a protective film of any one of Claim 1 to 10 by the manufacturing method which has the process of forming A).   The optical film with a protective film according to any one of claims 1 to 10, wherein at least one of heat treatment, stretching treatment, and relaxation treatment is performed, and the electrical characteristics of the optical film (A), The manufacturing method of the optical film with the improved protective film which has the process of improving a mechanical characteristic and / or an optical characteristic.   The processing method of the optical film with a protective film according to claim 13, wherein the treatment is a stretching treatment, and the stretching treatment is simultaneous biaxial stretching.