JP2021103226A - Optical film and bilayer film - Google Patents

Abstract

To provide an optical film excellent in slidability and transparency, and a bilayer film using the same.SOLUTION: An optical film includes a base material including a cycloolefin polymer, on a surface thereof. Arithmetic average roughness Ra and a maximum height Rz of the surface of the optical film on the base material side satisfy formulae (1) and (2), and an internal haze is 0.5% or less. Ra≥0.04 μm (1) and Rz≥0.7 μm (2).SELECTED DRAWING: None

Description

The present invention relates to optical films and multilayer films.

Resins containing cycloolefin polymers have been conventionally used as materials for optical films because they are excellent in transparency and the like.

The optical film is also required to have excellent handleability. In an optical film using a resin containing a cycloolefin polymer, the films tend to stick to each other when the films are wound. In order to solve such a problem, it has been conventionally practiced to impregnate silica particles in a resin constituting an optical film to improve the slipperiness of the film surface and improve the handleability. (For example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-128356

Patent Document 1 describes a method of co-extruding a norbornene-based resin and a norbornene-based resin containing silica particles to form a multilayer film. Further, as a method of including silica particles in the resin, a method of applying a coating liquid containing silica particles to the surface of the film can also be adopted.

According to such a method, the slipperiness of the film surface can be improved, but the haze of the optical film may be increased due to the inclusion of silica particles, and the transparency may be decreased.

The present invention has been devised in view of the above problems, and an object of the present invention is to provide an optical film having excellent slipperiness and transparency, and a multilayer film using this optical film.

The present inventor has made diligent studies to solve the above problems. As a result, in the optical film containing a base material containing a cycloolefin polymer on the surface, the present inventor sets the arithmetic mean roughness Ra and the maximum height Rz of the surface on the base material side within a predetermined range, and sets the internal haze to 0. The present invention has been completed by finding that excellent slipperiness and excellent transparency can be achieved at the same time by setting the content to 5.5 or less.
That is, the present invention includes the following.

[1] An optical film having a base material on its surface.
The substrate contains a cycloolefin polymer and contains
An optical film having an arithmetic mean roughness Ra and a maximum height Rz on the surface of the optical film on the substrate side, satisfying the formulas (1) and (2), and having an internal haze of 0.5% or less.
Ra ≧ 0.04 μm (1)
Rz ≧ 0.7 μm (2)
[2] The surface of the optical film on the substrate side is directly shaped so that the arithmetic mean roughness Ra and the maximum height Rz satisfy the formulas (1) and (2). The optical film according to [1], which is formed.
[3] The in-plane retardation Re of the optical film satisfies the following formula (3).
The optical film according to [1] or [2], wherein the retardation Rth in the thickness direction of the optical film satisfies the following formula (4).
-10nm ≤ Re ≤ 10nm (3)
-30nm ≤ Rth ≤ 30nm (4)
[4] The optical film according to any one of [1] to [3] and
A multi-layer film including a hard coat layer provided on the surface of the optical film on the substrate side.

According to the present invention, it is possible to provide an optical film having excellent slipperiness and excellent transparency, and a multilayer film using this optical film.

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

In the following description, the in-plane retardation Re of a film such as an optical film is a value represented by Re = (nx-ny) × d unless otherwise specified. Further, the retardation Rth in the thickness direction of the film is a value represented by Rth = {(nx + ny) /2-nz} × d unless otherwise specified. Here, nx represents the refractive index in the in-plane direction of the film, that is, the direction perpendicular to the thickness direction and in the direction that gives the maximum refractive index. ny represents the refractive index in the in-plane direction and orthogonal to the nx direction. nz represents the refractive index in the thickness direction. d represents the thickness of the film. The measurement wavelength is 590 nm unless otherwise specified.

In the following description, the "long" film means a film having a length of 5 times or more, preferably 10 times or more, and specifically a roll. A film that has a length that allows it to be rolled up and stored or transported. There is no particular limitation on the upper limit of the length, but it is usually 100,000 times or less with respect to the width.

[1. Optical film]
The optical film of the present invention has a base material on the surface. In the present invention, the substrate contains a cycloolefin polymer. The arithmetic mean roughness Ra and the maximum height Rz of the surface of the optical film of the present invention on the substrate side satisfy the formulas (1) and (2), and the internal haze is 0.5% or less.
Ra ≧ 0.04 μm (1)
Rz ≧ 0.7 μm (2)

[Base material]
The optical film has a base material on the surface. The base material is made of resin. The resin constituting the base material contains a cycloolefin polymer. The cycloolefin polymer is a polymer having a structure obtained by polymerizing a cycloolefin monomer. A resin containing such a cycloolefin polymer is usually excellent in performance such as transparency, dimensional stability, phase difference development, and ease of molding at a low temperature.

The cycloolefin polymer is a polymer having a cycloalkene structure in the main chain, a polymer having a cycloalkene structure in the side chain, a polymer having a cycloalkene structure in the main chain and the side chain, and two or more of these. Can be a mixture of the ratios of. Of these, a polymer having a cycloalkene structure in the main chain is preferable from the viewpoint of mechanical strength and heat resistance.

The number of carbon atoms constituting the cycloalkene structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 per cycloalkene structure. Less than or equal to. When the number of carbon atoms constituting the cycloalkene structure is in this range, the mechanical strength, heat resistance and moldability of the resin containing the cycloolefin polymer are highly balanced.

In the cycloolefin polymer, the proportion of structural units having a cycloalkene structure can be selected according to the intended use of the obtained product. The proportion of the structural unit having a cycloalkene structure in the cycloolefin polymer is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the ratio of the structural units having a cycloalkene structure in the cycloolefin polymer is in this range, the transparency and heat resistance of the cycloolefin resin are improved.

The cycloolefin polymer has a structure obtained by polymerizing a cycloolefin monomer. The cycloolefin monomer is a compound having a ring structure formed by carbon atoms and having a polymerizable carbon-carbon double bond in the ring structure. Examples of the polymerizable carbon-carbon double bond include a carbon-carbon double bond capable of polymerization such as ring-opening polymerization. Examples of the ring structure of the cycloolefin monomer include a monocycle, a polycycle, a condensed polycycle, a crosslinked ring, and a polycycle combining these. Among them, a polycyclic cycloolefin monomer is preferable from the viewpoint of highly balancing the characteristics such as the dielectric property and the heat resistance of the obtained polymer.

Preferred cycloolefin polymers include norbornene-based polymers, monocyclic cyclic olefin-based polymers, cyclic conjugated diene-based polymers, and hydrides thereof. Among these, the norbornene-based polymer is particularly suitable because it has good moldability.

Examples of the norbornene-based polymer include a ring-opening polymer of a monomer having a norbornene structure and a hydride thereof; an addition polymer of a monomer having a norbornene structure and a hydride thereof. Examples of ring-opening polymers of monomers having a norbornene structure include a ring-opening copolymer of one type of monomer having a norbornene structure and ring-opening of two or more types of monomers having a norbornene structure. Examples thereof include a copolymer and a ring-opening copolymer with a monomer having a norbornene structure and another monomer copolymerizable therewith. Further, as an example of the addition polymer of the monomer having a norbornene structure, the addition homopolymer of one kind of monomer having a norbornene structure and the addition copolymer of two or more kinds of monomers having a norbornene structure , And an addition copolymer of a monomer having a norbornene structure and another monomer copolymerizable therewith. Among these, the hydride of the ring-opening polymer of the monomer having a norbornene structure is particularly suitable from the viewpoints of moldability, heat resistance, low hygroscopicity, dimensional stability, light weight and the like.

Examples of monomers having a norbornene structure are bicyclo [2.2.1] hept-2-ene (trivial name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (trivial name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] deca-3-ene (trivial name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^{2, 5} . ^{17, 10} ] Dodeca-3-ene (trivial name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent on the ring) can be mentioned. Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Further, these substituents may be the same or different from each other, and a plurality of these substituents may be bonded to the ring. As the monomer having a norbornene structure, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

Examples of polar groups include heteroatoms and atomic groups having heteroatoms. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, silicon atoms, and halogen atoms. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, an amide group, an imide group, a nitrile group, and a sulfonic acid group. Can be mentioned.

Examples of monomer having a norbornene structure and a monomer capable of ring-opening copolymerization include monocyclic olefins such as cyclohexene, cycloheptene and cyclooctene and derivatives thereof; cyclic conjugated diene such as cyclohexene and cycloheptadiene and The derivative is mentioned. As the monomer having a norbornene structure and the monomer capable of ring-opening copolymerization, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

A ring-opening polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing the monomer in the presence of a ring-opening polymerization catalyst.

Examples of monomers that can be additionally copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene and derivatives thereof; cyclobutene, cyclopentene, and cyclohexene. Cycloolefins and derivatives thereof; and non-conjugated diene such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene. Among these, α-olefins are preferable, and ethylene is more preferable. Further, as the monomer having a norbornene structure and the monomer capable of addition copolymerization, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

A monomer addition polymer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing the monomer in the presence of an addition polymerization catalyst.

The above-mentioned hydrogenated compounds of the ring-opening polymer and the addition polymer are prepared by, for example, hydrogenating a carbon-carbon unsaturated bond in a solution of the ring-opening polymer and the addition polymer in an amount of preferably 90% or more. Can be manufactured. Hydrogenation can be carried out in the presence of a hydrogenation catalyst containing transition metals such as nickel and palladium.

Among the norbornene-based polymers, as structural units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane- It has a 7,9-diyl-ethylene structure, the amount of these structural units is 90% by weight or more with respect to the total structural units of the norbornene-based polymer, and the ratio of X and the ratio of Y The ratio is preferably 100: 0 to 40:60 in terms of the weight ratio of X: Y. By using such a polymer, the olefin resin layer containing the norbornene-based polymer can be made to have no dimensional change in a long period of time and have excellent stability of optical characteristics.

Examples of the monocyclic cyclic olefin polymer include an addition polymer of a cyclic olefin monomer having a monocycle such as cyclohexene, cycloheptene, and cyclooctene.

Examples of cyclic conjugated diene-based polymers are polymers obtained by cyclization reaction of addition polymers of conjugated diene-based monomers such as 1,3-butadiene, isoprene, and chloroprene; cyclic conjugates such as cyclopentadiene and cyclohexadiene. 1,2- or 1,4-additional polymers of diene-based monomers; and hydrides thereof can be mentioned.

Further, in the above-mentioned cycloolefin polymer, it is preferable that the molecule of the cycloolefin polymer does not contain a polar group. By using a cyclic olefin polymer containing no polar group in the molecule, the water absorption of the resin layer in the obtained optical film can be reduced.

The weight average molecular weight (Mw) of the cycloolefin polymer can be appropriately selected according to the intended use of the obtained product, and is preferably 10,000 or more, more preferably 15,000 or more, and particularly preferably 20,000 or more. It is preferably 100,000 or less, more preferably 80,000 or less, and particularly preferably 50,000 or less. When the weight average molecular weight is in such a range, the mechanical strength and moldability of the resin layer in the obtained product are highly balanced. Here, the weight average molecular weight is converted to polyisoprene or polystyrene as measured by gel permeation chromatography using cyclohexane as a solvent (however, toluene may be used if the sample does not dissolve in cyclohexane). Weight average molecular weight of.

The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the cycloolefin polymer is preferably 1.2 or more, more preferably 1.5 or more, and particularly preferably 1.8 or more. Is 3.5 or less, more preferably 3.0 or less, and particularly preferably 2.7 or less. By setting the molecular weight distribution to the above lower limit value or more, the productivity of the polymer can be increased and the production cost can be suppressed. Further, when the value is not more than the upper limit, the amount of the low molecular weight component becomes small, so that the relaxation at the time of high temperature exposure can be suppressed and the stability of the base material can be improved.

The proportion of the cycloolefin polymer in the resin constituting the base material is preferably 90% by weight or more, more preferably 92% by weight or more, particularly preferably 95% by weight or more, and preferably 99.9% by weight or less. It is more preferably 99% by weight or less, and particularly preferably 98% by weight or less. By setting the proportion of the cycloolefin polymer to the lower limit of the above range or more, the water absorption of the base material can be reduced.

The resin constituting the base material may further contain any component in addition to the cycloolefin polymer. Optional components include, for example, colorants such as ester compounds, pigments, dyes; optical brighteners; dispersants; heat stabilizers; light stabilizers; UV absorbers; antistatic agents; antioxidants; fine particles; surfactants. Examples include additives such as activators. One of these components may be used alone, or two or more of these components may be used in combination at any ratio.

The glass transition temperature of the resin constituting the base material is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably 120 ° C. or higher, preferably 190 ° C. or lower, more preferably 180 ° C. or lower, particularly preferably. It is 170 ° C. or lower. When the glass transition temperature is within the above range, a base material having excellent durability can be easily produced. Further, by setting the value to the upper limit or less, molding can be easily performed.

[Layer structure of optical film]
The optical film may consist of only a single base material, or may include an arbitrary layer together with the base material. When the optical film contains any layer, the number of arbitrary layers may be one or two or more. Further, the optical film may have a mode in which two or more base materials and an arbitrary layer are provided. In the case of this aspect, the optical film may have a base material on the front surface and the back surface, respectively, and an arbitrary layer may be provided between the two base materials. Examples of the optional layer include a protective film layer for protecting the base material, an adhesive layer for adhering the two layers, and the like.

[Surface roughness of optical film]
The surface of the optical film on the substrate side can be a concavo-convex surface having a predetermined arithmetic mean roughness Ra and a predetermined maximum height Rz.

The arithmetic mean roughness Ra of the surface of the optical film on the substrate side satisfies the above formula (1). That is, Ra on the surface of the optical film on the substrate side is 0.04 μm or more. The Ra on the surface of the optical film on the substrate side is preferably 0.05 μm or more, more preferably 0.06 μm or more, preferably 0.12 μm or less, and more preferably 0.10 μm or less. When the Ra of the surface of the optical film on the substrate side is 0.04 μm or more, the surfaces of the films that overlap when the optical films are wound (that is, the surface of the optical film on the substrate side and the surface thereof) Can reduce the friction that can occur between the surface and the opposite surface, and improve the slipperiness of the optical film.

The maximum height Rz of the surface of the optical film of the present invention on the substrate side satisfies the above formula (2). That is, the Rz of the surface of the optical film on the substrate side is 0.7 μm or more. The Rz of the surface of the optical film on the substrate side is preferably 0.8 μm or more, more preferably 0.9 μm or more, preferably 1.5 μm or less, and more preferably 1.3 μm or less. When the Rz of the surface of the optical film on the substrate side is 0.7 μm or more, when the optical films are wound, the surfaces of the overlapping films (that is, the surface of the optical film on the substrate side and the surface thereof) The friction that can occur between the surface and the surface on the opposite side can be reduced, and the slipperiness of the optical film can be improved.

When the optical film is composed of a single substrate and when the optical film is provided with substrates on the front surface and the back surface, both the front surface and the back surface of the optical film are based. It can be the surface on the material side. In such a case, Ra and Rz may satisfy the above formulas (1) and (2) on at least one of the front surface and the back surface of the optical film. Further, in such a case, Ra and Rz on the front surface and the back surface of the optical film may be the same, or either one or both of Ra and Rz may be different.

Ra and Rz on the surface of the optical film can be measured using, for example, a fine shape measuring instrument (Surfcorder ET4000A manufactured by Kosaka Laboratory Co., Ltd.).

In the present invention, the surface of the optical film on the substrate side can be formed so that Ra and Rz satisfy the above formulas (1) and (2) by direct shaping. In the present invention, "direct shaping" means that the surface of the optical film on the substrate side is physically processed to form irregularities. Examples of the direct shaping method include a blasting method and a touch roll forming method.

In the present invention, the blasting method is a method of spraying an abrasive on the surface of a film to form irregularities. Examples of the blasting method include a sandblasting method in which an abrasive is sprayed to form irregularities, a wet blasting method in which a blasting fluid containing an abrasive is sprayed to form irregularities, and the like. The wet blast method is preferable from the viewpoint of preventing the residual abrasive from remaining in the film after the blast treatment. As the abrasive used for the blasting treatment, alumina, resin, glass particles, zirconia, stainless steel and the like can be used. The blasting fluid used for wet blasting can be a slurry-like dispersion containing a liquid medium and a solid abrasive suspended in the medium. An example of a medium is water.

When unevenness is formed on the surface of the optical film on the substrate side by the wet blast method, the time, speed, and pressure of spraying the blasting fluid, the particle size of the abrasive, the content ratio of the abrasive in the blasting fluid, etc. Ra and Rz on the film surface can be adjusted by adjusting the blasting conditions.

In the present invention, the touch roll molding method is a method of forming irregularities by pressing a film arranged between a touch roll that imparts an uneven shape to a film and a backup roll. The material of the touch roll to be used is not particularly limited, and examples thereof include a touch roll made of an elastic body such as rubber and a touch roll made of a rigid body such as metal. A touch roll made of an elastic body is preferable from the viewpoint of stabilizing the transfer in the width direction of the film.

When forming irregularities on the film by the touch roll molding method, it is preferable to use the film produced by the melt extrusion method from the viewpoint of easily imparting the irregularities. Further, Ra and Rz of the touch roll are preferably 100% or more and 200% or less with respect to Ra and Rz finally formed on the film.

[Coefficient of static friction of optical film]
The coefficient of static friction between one surface of the optical film of the present invention and the surface of the optical film opposite to the surface is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3. It is as follows. When the coefficient of static friction of the optical film is 0.5 or less, the slipperiness of the optical film can be made excellent, blocking can be prevented when the optical films are rolled up, and the wound shape can be made good. In particular, when the coefficient of static friction of the optical film is 0.3 or less, it is possible to more effectively suppress the occurrence of defects such as scratches due to blocking. Here, the defect can be inspected by visually inspecting the film terminal or in-line by using a scratch inspection device (manufactured by MEC).

The coefficient of static friction of the optical film can be measured by using, for example, a friction measuring instrument (manufactured by Toyo Seiki Seisakusho, “TR-2”) in accordance with the method specified in JIS K7125.

[Internal haze of optical film]
The internal haze of the optical film of the present invention is 0.5% or less. The internal haze of the optical film is preferably 0.4% or less, more preferably 0.3% or less, and more preferably 0. When the internal haze is 0.5% or less, the optical film can have sufficient transparency in optical applications.

For the internal haze of the optical film, an aqueous solution obtained by diluting zinc bromide with pure water is placed in the quartz cell, and a rectangular film piece cut out from the optical film is inserted into the quartz cell to haze the quartz cell. It can be measured by installing it on a meter and measuring its haze.

[Optical film retardation]
In the present invention, the in-plane retardation Re of the optical film preferably satisfies the following formula (3).
-10nm ≤ Re ≤ 10nm (3)

The Re of the optical film is more preferably -8 nm or more, particularly preferably -5 nm or more, more preferably 8 nm or less, and particularly preferably 5 nm or less.

In the present invention, the retardation Rth in the thickness direction of the optical film preferably satisfies the following formula (4).
-30nm ≤ Rth ≤ 30nm (4)

The Rth of the optical film is more preferably −20 nm or more, particularly preferably −10 nm or more, more preferably 20 nm or less, and particularly preferably 10 nm or less.

The Re and Rth of the optical film can be measured by, for example, AXO Scan OPMF-1 manufactured by AXOMETRICS. The measurement wavelength can be 590 nm.

[Form of optical film]
The optical film may be a single-wafer film or a long film. A long film can usually be in the form of a film roll, but the optical film of the present invention has predetermined Ra and Rz on the surface on the substrate side and is excellent in slipperiness. In addition, the occurrence of blocking and the like can be suppressed, and the winding shape can be improved. Further, from the viewpoint of efficient production by the roll-to-roll method, a long film is preferable as the optical film.

The optical film may be an unstretched unstretched film or a stretched stretched film.

[Thickness of optical film]
The thickness of the optical film is not particularly limited. The specific thickness of the optical film is preferably 20 μm or more, more preferably 25 μm or more, preferably 200 μm or less, and more preferably 60 μm or less from the viewpoint of thinning.

[Manufacturing method of optical film]
Next, an example of the method for producing the optical film of the present invention will be described.
The optical film of the present invention has irregularities on the surface of the film on the base material side in step 1 of manufacturing a film containing a base material so that Ra and Rz satisfy the above formulas (1) and (2). It can be produced by a production method including step 2 of forming.

[Step 1]
Step 1 is a step of producing a film containing a base material.
When the optical film is composed of a single base material, a film containing the base material can be obtained by molding a resin containing a cycloolefin polymer as a material of the base material into a film shape.

The method for molding the resin containing the cycloolefin polymer into a film is not particularly limited. Examples of the method for forming the resin into a film include a melt extrusion method, a solution casting method, and a solution casting method. Of these, the melt extrusion method is preferable from the viewpoint that unevenness is likely to be formed in step 2.

When the film containing the base material is composed of a plurality of layers, a method of laminating two or more separately produced layers with an adhesive or the like, or coextruding the resin constituting each layer to have the plurality of layers. A film containing a base material can be obtained by a method of producing a film, a method of producing one layer and then forming another layer on the layer by coating, or the like.

[Step 2]
The step 2 is a step of forming irregularities on the surface of the film containing the base material on the base material side so that Ra and Rz satisfy the above formulas (1) and (2).
As a method for forming irregularities on the surface of the film containing the base material on the base material side, a method by direct shaping such as a blast treatment method and a touch roll molding method is preferable. The blasting method and the touch roll forming method are as described above.

[Arbitrary process]
The method for producing an optical film may include a stretching step of stretching a film containing a base material. From the viewpoint of obtaining an optical film having desired Ra and Rz, the stretching step is preferably performed before the step 2.
The stretching conditions (stretching direction, stretching temperature, etc.) in the stretching step are not particularly limited and may be appropriately selected depending on the application of the optical film and the like.

[Use]
The optical film of the present invention has Ra of 0.04 or more and Rz of 0.7 or more on the surface of the base material side and is excellent in slipperiness. Therefore, when the films are wound, the films are less likely to stick to each other for handling. Excellent in sex. Further, since the optical film of the present invention contains a cycloolefin polymer and has an internal haze of 0.5% or less, it has excellent transparency and is suitable for optical applications. Since the optical film of the present invention has such excellent properties, it can be suitably used as, for example, a film for protecting a polarizing plate.

An arbitrary layer may be provided on one surface or both surfaces of the optical film of the present invention depending on the application. Examples of the optional layer include a hard coat layer, a low refractive index layer, an antistatic layer and the like. For these arbitrary layers, for example, the optical film is unwound from the wound optical film, and one or both surfaces of the unwound optical film are coated with a resin or the like as a material for the arbitrary layer. It can be provided by a method or the like.

[2. Multi-layer film]
The multilayer film of the present invention includes the optical film of the present invention and a hard coat layer provided on the surface of the optical film on the substrate side. By providing the hard coat layer on the surface of the optical film, performances such as antireflection, antistatic, scratch resistance, and strength can be imparted. The hard coat layer may include a clear hard coat layer and an anti-glare hard coat layer.

When the optical film is composed of a single base material and when the optical film is provided with a base material on the front surface and the back surface, one of the front surface and the back surface of the optical film. A hard coat layer may be provided on one or both surfaces. When one surface of the optical film is not the surface on the substrate side, a hard coat layer may be provided on the surface.

The production speed is usually different between the process of forming the hard coat layer and the process of producing the optical film. Therefore, the hard coat layer is formed by feeding out an optical film from the wound optical film and applying a composition for forming the hard coat layer to the surface of the drawn optical film on the substrate side. sell. Since the optical film of the present invention is less likely to stick to each other when the films are wound and has excellent handleability, the process of forming a hard coat layer on the surface of the optical film can be smoothly performed, and work efficiency can be achieved. Excellent for.

Examples of the composition for forming the hard coat layer include a composition containing an active energy ray-curable resin and fine particles that can be cured by active energy rays. Examples of the active energy ray include ultraviolet rays and electron beams.

As the active energy ray-curable resin, a resin having a hardness of "HB" or higher in a pencil hardness test specified in JIS K5600-5-4 after curing is preferable.

Examples of the active energy ray-curable resin include organic silicone-based, melamine-based, epoxy-based, acrylic-based, urethane acrylate-based, and polyfunctional acrylate-based active energy ray-curable resins. Among them, urethane acrylate-based ultraviolet curable resin and / or polyfunctional acrylate-based ultraviolet curable resin are preferable from the viewpoint of good adhesive strength, excellent toughness and productivity.

The fine particles may be organic fine particles composed of an organic substance or inorganic fine particles composed of an inorganic substance. The fine particles are preferably inorganic fine particles, and more preferably inorganic oxide fine particles. Examples of the inorganic oxides that can form fine particles include silica, titania (titanium oxide), zirconia (zinc oxide), zinc oxide, tin oxide, cerium oxide, antimony pentoxide, titanium dioxide, and tin-doped indium oxide (tin). ITO), antimonated tin oxide (ATO), phosphorus-doped tin oxide (PTO), zinc-doped indium oxide (IZO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide. (FTO) can be mentioned.

As the fine particles, silica fine particles are preferable because they have an excellent balance between the adhesion to the resin as a binder for forming the hard coat layer and the transparency, and the refractive index of the hard coat layer can be easily adjusted.

The composition for forming the hard coat layer may contain fine particles of one kind alone or in a combination of two or more kinds.

The number average particle size of the fine particles is preferably 1 nm or more and 1000 nm or less, more preferably 1 nm or more and 500 nm or less, and further preferably 1 nm or more and 250 nm or less. The smaller the number average particle size of the fine particles, the lower the haze of the hard coat layer, and the higher the adhesion between the fine particles and the resin as a binder forming the hard coat layer.

In the composition for forming the hard coat layer, the content of the fine particles is preferably 10 to 80 parts by weight, more preferably 10 to 50 parts by weight, based on 100 parts by weight of the active energy ray-curable resin. Yes, more preferably 20-40 parts by weight. When the content of the fine particles is in the above range, the optical characteristics such as the haze value are excellent.

The composition for forming the hard coat layer may contain a solvent for dissolving or dispersing the active energy ray-curable resin. Examples of the solvent include alcohols such as methanol, ethanol, isopropanol, n-butanol, and isobutanol; such as ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol, diethylene glycol monobutyl ether, and diacetone glycol. Glycols; aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as n-hexane and n-heptane; esters such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; methyl ethyl ketooxime Oxymes such as; and combinations consisting of two or more of these; etc.

When the active energy ray-curable resin is cured by ultraviolet rays, the composition for forming the hard coat layer may further contain a photopolymerization initiator. Examples of the photopolymerization initiator include previously known photopolymerization initiators. Specifically, for example, benzophenone, Ciba Specialty Chemicals Co., Ltd. "DaroCure 1173", "Irgacure 651", "Irgacure" 184 ”,“ Irgacure 907 ”,“ Irgacure 754 ”and the like.

In addition to the above-mentioned fine particles and active energy ray-curable resin, the composition for forming the hard coat layer includes various additives (eg, polymerization inhibitor, antioxidant, ultraviolet absorber, antistatic agent, light stabilizer, etc. It may contain a solvent, a defoaming agent, a leveling agent).

The multi-layer film is a step of applying a composition for forming a hard coat layer to the surface of an optical film on the substrate side and then drying the coating layer made of the composition to obtain a dried coating layer. It can be produced by irradiating the coated layer with active energy rays such as ultraviolet rays to obtain a hard coat layer. The drying conditions (drying temperature, drying time, etc.) of the coating layer and the irradiation conditions (irradiation amount, irradiation time, etc.) of the active energy rays can be selected in consideration of the components of the composition forming the hard coat layer. Further, before applying the composition for forming the hard coat layer to the optical film, a surface treatment such as a corona treatment may be applied to the surface of the optical film on the substrate side.

The thickness of the hard coat layer is preferably 3 μm or more and 20 μm or less, and more preferably 7 μm or more and 13 μm or less.

The multilayer film may contain an arbitrary layer on the hard coat layer. Examples of the optional layer include an adhesive layer for adhering to a retardation film and the like, a matte layer for improving the slipperiness of the film, an antireflection layer, an antifouling layer and the like.

The multilayer film of the present invention can be used for various purposes, and can be used for producing various optical films in combination with a functional layer such as a retardation film or a polarizer.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof.

In the following description, the "part" representing the quantity is based on weight unless otherwise specified. The operations described below were performed under normal temperature and pressure conditions unless otherwise specified.

[Evaluation method]
(Measurement of internal haze)
An aqueous zinc bromide solution (refractive index 1.53) obtained by diluting zinc bromide with pure water was placed in a quartz cell having a height of 55 mm, a width of 40 mm, and a width of 14 mm. A quartz cell was installed in a haze meter (“NDH7000” manufactured by Nippon Denshoku Co., Ltd.), haze was measured, and zero correction was performed. Next, the film obtained in each example was cut out in a rectangular shape, and the cut out film piece was inserted into the quartz cell. A quartz cell in which a film piece was inserted was placed in a haze meter (“NDH7000” manufactured by Nippon Denshoku Co., Ltd.), and the internal haze of the film was measured.

(Measurement of coefficient of static friction)
The coefficient of static friction of the films obtained in each example was measured by the following method. The film produced in each example was cut into a size of 50 mm × 50 mm to obtain a test piece. Using this test piece, the coefficient of static friction was measured at a speed of 500 mm / min using a friction measuring instrument (manufactured by Toyo Seiki Seisakusho, "TR-2") in accordance with JIS K7125. As the mating material for measurement (a member that comes into contact with the surface of the test piece during measurement), the same film that was cut out from the test piece was used. For the optical film obtained in the examples, the coefficient of static friction between the blasted surface of the film and the surface opposite to the blasted surface of the film was measured. For the film obtained in the comparative example, the coefficient of static friction between one surface of the film and the surface opposite to the surface was measured.

(Measurement of surface roughness)
The arithmetic mean roughness Ra and the maximum height Rz on the surface of the film were measured using a fine shape measuring instrument (Surfcorder ET4000A manufactured by Kosaka Laboratory Co., Ltd.). The measurement was performed under the conditions of a measurement range of 1000 μm × 1000 μm, a measurement speed of 2 m / sec, a 2CR filter low frequency cut (cutoff value 0.800 mm), and a 2CR filter high frequency cut (cutoff value 0.000 mm).

(Measurement method of retardation)
The in-plane retardation Re and the thickness direction retardation Rth of the film were measured by Axo Scan OPMF-1 manufactured by AXOMETRICS. At this time, the measurement was performed at a wavelength of 590 nm.

[Example 1]
(1-1) Production of Substrate A pellet of an alicyclic olefin resin containing a norbornene polymer (“ZEONOR” manufactured by Nippon Zeon Corporation, glass transition temperature 160 ° C.) was prepared.

The resin pellets were dried at 100 ° C. for 5 hours, supplied to an extruder, melted, passed through a polymer filter, and extruded and cooled from a T-die onto a casting drum in the form of a sheet to prepare a substrate having a thickness of 40 μm.

(1-2) Manufacture of Optical Film One surface of the base material manufactured in (1-1) is wet-blasted using a wet blasting device (“Sigma” manufactured by Macau) to obtain an optical film. Obtained. As the fluid for wet blasting, a liquid medium and a dispersion liquid containing a solid abrasive dispersed therein were used. Alumina (A # 2000) was used as the abrasive, and water was used as the medium. The blasting conditions such as the content ratio of the abrasive in the blasting fluid, the spraying speed of the blasting liquid, and the spraying time were adjusted so that the treated surface had a predetermined surface roughness. The obtained optical film was evaluated by the above evaluation method. As a result, Ra of the treated surface of the optical film was 0.05 μm, Rz was 0.8 μm, the internal haze was 0%, the coefficient of static friction was 0.4, Re was 2 nm, and Rth was 7 nm. No blocking was observed in the film roll obtained by winding the obtained optical film into a roll, and the rolled shape was good.

[Example 2]
Except that in (1-2) of Example 1, the wet blasting treatment was performed by adjusting the blasting conditions so that the Ra of the treated surface after the wet blasting treatment was 0.07 μm and the Rz was 1.1 μm. The same operation as in (1-2) of Example 1 was carried out to obtain an optical film. The obtained optical film was evaluated by the above evaluation method. As a result, Ra of the treated surface of the optical film was 0.07 μm, Rz was 1.1 μm, the internal haze was 0%, the coefficient of static friction was 0.3, Re was 2 nm, and Rth was 7 nm. No blocking was observed in the film roll obtained by winding the obtained optical film into a roll, and the rolled shape was good.

[Example 3]
Except that in (1-2) of Example 1, the wet blasting treatment was performed by adjusting the blasting conditions so that the Ra of the treated surface after the wet blasting treatment was 0.10 μm and the Rz was 1.3 μm. The same operation as in (1-2) of Example 1 was carried out to obtain an optical film. The obtained optical film was evaluated by the above evaluation method. As a result, Ra of the treated surface of the optical film was 0.10 μm, Rz was 1.3 μm, the internal haze was 0%, the coefficient of static friction was 0.3, Re was 2 nm, and Rth was 7 nm. No blocking was observed in the film roll obtained by winding the obtained optical film into a roll, and the rolled shape was good.

[Comparative Example 1]
(C1-1) Production of Silica Particle-Containing Resin Pellets of alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd .; glass transition temperature 160 ° C.) containing a norbornene polymer and a predetermined amount of silica particles (manufactured by DIC Co., Ltd., An average particle size of 0.5 μm) was mixed and kneaded with a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd .: TEM-35B) to produce a silica particle-containing resin. The content of silica particles was 0.5% by weight based on the resin.

(C1-2) Production of Laminated Film The resin produced in (C1-1) was prepared as the resin for the A layer. Pellets of the alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd .; glass transition temperature 160 ° C.) containing the norbornene polymer used in (C1-1) were prepared as the resin for the B layer.
The resin for the A layer and the resin for the B layer were subjected to a multilayer sheet molding machine (manufactured by Collin), and the A layer / B layer / A layer were laminated in this order, and the thickness of the A layer was 10 μm and the thickness of the B layer was increased. By molding so as to have a thickness of 20 μm, a laminated film having a thickness of 40 μm was obtained. The laminated film was evaluated by the above evaluation method. As a result, Ra on the surface of the laminated film was 0.04 μm, Rz was 0.8 μm, the internal haze was 0.8%, the coefficient of static friction was 0.7, Re was 4 nm, and Rth was 10 nm. In the film roll obtained by winding the obtained laminated film into a roll shape, blocking occurred and the wound shape was poor.

[Comparative Example 2]
(C2-1) Production of Silica-Containing Resin The same operation as in (C1-1) of Comparative Example 1 was performed except that the silica particles were mixed so that the content of the silica particles was 1.0%, and the silica was contained. The resin was obtained.

(C2-2) Production of Laminated Film In (C1-2) of Comparative Example 1, the silica particles produced in (C2-1) above were replaced with the resin produced in (C1-1) as the resin for the A layer. The same operation as in (C1-2) of Comparative Example 1 was carried out except that the contained resin was used to obtain a laminated film having a thickness of the A layer of 10 μm, a thickness of the B layer of 20 μm, and a total thickness of 40 μm. The laminated film was evaluated by the above evaluation method. As a result, Ra on the surface of the laminated film was 0.04 μm, Rz was 1.0 μm, the internal haze was 1.2%, the coefficient of static friction was 0.7, Re was 4 nm, and Rth was 10 nm. In the film roll obtained by winding the obtained laminated film into a roll shape, blocking occurred and the wound shape was poor.

[Comparative Example 3]
(C3-1) Production of Silica-Containing Resin The same operation as in (C1-1) of Comparative Example 1 was carried out except that silica particles having an average particle diameter of 1 μm were used as the silica particles to obtain a silica-containing resin.

(C3-2) Production of Laminated Film In (C1-2) of Comparative Example 1, the silica particles produced in (C3-1) above were replaced with the resin produced in (C1-1) as the resin for the A layer. The same operation as in (C1-2) of Comparative Example 1 was carried out except that the contained resin was used to obtain a laminated film having a thickness of the A layer of 10 μm, a thickness of the B layer of 20 μm, and a total thickness of 40 μm. The laminated film was evaluated by the above evaluation method. As a result, Ra on the surface of the laminated film was 0.06 μm, Rz was 1.2 μm, the internal haze was 1.0%, the coefficient of static friction was 0.7, Re was 4 nm, and Rth was 10 nm. In the film roll obtained by winding the obtained laminated film into a roll shape, blocking occurred and the wound shape was poor.

[Comparative Example 4]
(C4-1) Production of Silica-Containing Resin Except that silica particles having an average particle diameter of 1 μm were used as silica particles and that the silica particles were mixed so that the content of the silica particles was 1.0%. The same operation as (C1-1) of Comparative Example 1 was carried out to obtain a silica-containing resin.

(C4-2) Production of Laminated Film In (C1-2) of Comparative Example 1, the silica particles produced in (C4-1) above were replaced with the resin produced in (C1-1) as the resin for the A layer. The same operation as in (C1-2) of Comparative Example 1 was carried out except that the contained resin was used to obtain a laminated film having a thickness of the A layer of 10 μm, a thickness of the B layer of 20 μm, and a total thickness of 40 μm. The laminated film was evaluated by the above evaluation method. As a result, Ra on the surface of the laminated film was 0.07 μm, Rz was 1.4 μm, the internal haze was 2.2%, the coefficient of static friction was 0.6, Re was 4 nm, and Rth was 10 nm. In the film roll obtained by winding the obtained laminated film into a roll shape, blocking was observed, although it was less than that of Comparative Example 1, and the rolled shape was inferior to that of Examples 1 to 3.

[Comparative Example 5]
(C5-1) Production of Silica-Containing Resin Except that silica particles having an average particle diameter of 1 μm were used as silica particles and that the silica particles were mixed so that the content of the silica particles was 2.0%. The same operation as (C1-1) of Comparative Example 1 was carried out to obtain a silica-containing resin.

(C5-2) Production of Laminated Film In (C1-2) of Comparative Example 1, the silica particles produced in (C5-1) above were replaced with the resin produced in (C1-1) as the resin for the A layer. The same operation as in (C1-2) of Comparative Example 1 was carried out except that the contained resin was used to obtain a laminated film having a thickness of layer A of 10 μm, a thickness of layer B of 20 μm, and a total thickness of 40 μm. The laminated film was evaluated by the above evaluation method. As a result, Ra on the surface of the laminated film was 0.10 μm, Rz was 1.5 μm, the internal haze was 3.7%, the coefficient of static friction was 0.5, Re was 4 nm, and Rth was 10 nm. In the film roll obtained by winding the obtained laminated film into a roll, no blocking was observed and the rolled appearance was good. However, the laminated film obtained in this example has a high internal haze and is not suitable for use as an optical film.

[Comparative Example 6]
(C6-1) Preparation of coating liquid 100 parts of polyurethane aqueous dispersion (“Superflex 210” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and an epoxy compound (“Deconal EX313” manufactured by Nagase ChemteX Co., Ltd.) as a cross-linking material. 15 parts, 2 parts of adihydric acid adipate as a non-volatile base, and 10 parts of an aqueous dispersion of silica particles (“Snowtex ZL” manufactured by Nissan Chemical Co., Ltd .; average particle size 85 nm) as a lubricant. As a wetting agent, an acetylene-based surfactant (“Surfinol 440” manufactured by Air Products and Chemicals Co., Ltd.) is blended with 0.5% by weight based on the total solid content and water to obtain a solid content concentration of 4%. The liquid composition was obtained as a coating liquid. The viscosity of the coating liquid was 1.2 mPa · s.

(C6-2) Production of Optical Film Pellets of alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd .; glass transition temperature 126 ° C.) containing a norbornene polymer are dried at 100 ° C. for 5 hours and then supplied to an extruder. After melting, it was passed through a polymer filter and extruded from a T-die onto a casting drum in the form of a sheet to prepare a substrate having a thickness of 80 μm.
One surface of this base material was subjected to a corona discharge treatment, and the coating liquid prepared in (C6-1) was applied so that the coating thickness after drying was 45 nm. After the coating liquid was dried by air drying, both ends were grasped by a stretching device, and stretching treatment was performed at a stretching temperature of 139 ° C. and a stretching ratio of 1.50 times to obtain an optical film. The film was evaluated by the above evaluation method. As a result, Ra on the surface of the film was 0.03 μm, Rz was 0.1 μm, the internal haze was 0.1%, the coefficient of static friction was 0.6, Re was 52 nm, and Rth was 125 nm. In the film roll obtained by winding the obtained laminated film into a roll shape, blocking was observed, although it was less than that of Comparative Example 1, and the rolled shape was inferior to that of Examples 1 to 3.

Tables 1 and 2 show the evaluation results of Examples and Comparative Examples.
In the table, the "processing method" means a processing method for forming irregularities on the surface of the film. In the table, "blast" means that the surface of the film has been wet blasted. In the table, "kneading" means that a layer of silica-containing resin obtained by kneading silica is provided on the surface side of the film. In the table, "coating" means that the surface of the film is coated with a coating liquid containing silica.

As is clear from the results shown in Tables 1 and 2, it can be seen that the optical film of the present invention has a low coefficient of static friction and a low internal haze. From this, it can be seen that according to the present invention, it is possible to provide an optical film having excellent slipperiness and excellent transparency.

Claims (4)

An optical film having a base material on its surface.
The substrate contains a cycloolefin polymer and contains
An optical film having an arithmetic mean roughness Ra and a maximum height Rz on the surface of the optical film on the substrate side, satisfying the formulas (1) and (2), and having an internal haze of 0.5% or less.
Ra ≧ 0.04 μm (1)
Rz ≧ 0.7 μm (2) The surface of the optical film on the substrate side is formed by direct shaping so that the arithmetic mean roughness Ra and the maximum height Rz satisfy the formulas (1) and (2). The optical film according to claim 1. The in-plane retardation Re of the optical film satisfies the following formula (3).
The optical film according to claim 1 or 2, wherein the retardation Rth in the thickness direction of the optical film satisfies the following formula (4).
-10nm ≤ Re ≤ 10nm (3)
-30nm ≤ Rth ≤ 30nm (4) The optical film according to any one of claims 1 to 3 and
A multi-layer film including a hard coat layer provided on the surface of the optical film on the substrate side.