JPWO2019026842A1 - Optical film and manufacturing method thereof - Google Patents

Abstract

An optical film obtained by roughening at least one surface of a film containing an alicyclic structure-containing polymer, wherein at least one surface has a maximum height Rz of 150 nm or more and 3000 nm or less, and an arithmetic average roughness. An optical film having a Ra of 30 nm or more and 1000 nm or less. The optical film preferably has an internal haze of 5% or less. The alicyclic structure-containing polymer is preferably a specific block copolymer hydride [E]. A method for producing an optical film including a roughening step is also disclosed.

Description

The present invention relates to an optical film and a manufacturing method thereof.

A display device such as a liquid crystal display device is provided with various optical elements such as a polarizing plate and a retardation plate. Some of such optical elements are composed of a film. For example, a polarizing plate generally includes a film-shaped polarizer formed of a material such as polyvinyl alcohol and a protective film that protects the polarizer. As an example of such a protective film, a resin film containing an alicyclic structure-containing polymer is known (see Patent Documents 1 and 2). The resin film containing the alicyclic structure-containing polymer can be usefully used as a protective film in a polarizing plate from the viewpoint of mechanical strength and optical properties.

JP, 2007-245551, A JP, 2011-013378, A

The polarizing plate is required to exhibit durability in the environment during manufacturing and use of the display device. For example, there is a case where the peeling strength of the protective film in the polarizing plate is required to be high when the work is reworked during the manufacture of the display device or when the polarizer is contracted during the use of the display device.

However, when a conventional resin film containing an alicyclic structure-containing polymer is used as a protective film, the peel strength may be insufficient. In particular, when the protective film is a stretched film produced through a stretching step, cohesive failure in the vicinity of the surface layer caused by the polymer molecules being oriented and intermolecular entanglement is reduced, resulting in peel strength. A shortage of can occur.

Therefore, an object of the present invention is to provide an optical film which has a high peel strength and can be effectively used as a protective film, and a method for producing the same.

As a result of studying to solve the above-mentioned problems and achieve the object, the present inventor found that at least one surface of an optical film obtained by roughening at least one surface of a film containing an alicyclic structure-containing polymer, The present invention has been completed by finding that the above-mentioned problems can be solved by setting the maximum height Rz and the arithmetic mean roughness Ra within a predetermined range.
That is, according to the present invention, the following [1] to [7] are provided.

[1] An optical film obtained by roughening at least one surface of a film containing an alicyclic structure-containing polymer,
An optical film having a maximum height Rz of 150 nm or more and 3000 nm or less and an arithmetic average roughness Ra of 30 nm or more and 1000 nm or less on at least one surface.
[2] The optical film according to [1], which has an internal haze of 5% or less.
[3] The alicyclic structure-containing polymer is a block copolymer hydride [E],
The block copolymer hydride [E] is a hydride of the block copolymer [D],
The block copolymer [D] consists of a polymer block [A] and a polymer block [B], or consists of the polymer block [A] and a polymer block [C],
The polymer block [A] is a polymer block containing a repeating unit [I] derived from an aromatic vinyl compound as a main component,
The polymer block [B] is a polymer block containing a repeating unit [I] derived from an aromatic vinyl compound and a repeating unit [II] derived from a chain conjugated diene compound as a main component,
The optical film according to [1] or [2], wherein the polymer block [C] is a polymer block containing a repeating unit [II] derived from a chain conjugated diene compound as a main component.
[4] The optical film according to [3], wherein the retardation Re in the in-plane direction is 3 nm or less and the absolute value of the retardation Rth in the thickness direction is 3 nm or less.
[5] The optical film as described in [1] or [2], wherein the alicyclic structure-containing polymer is crystalline and has a crystallinity of 1% or more.
[6] The optical film according to any one of [1] to [5], which is a polarizer protective film.
[7] The method for producing an optical film according to any one of [1] to [6],
A step of stretching a film containing an alicyclic structure-containing polymer, and a treatment step including at least one of the steps of thermosetting the film,
And a step of roughening at least one surface of the film that has undergone the treatment step.

According to the optical film of the present invention, it is possible to provide a film which has high peel strength and can be effectively used as a protective film in a polarizing plate. Further, according to the method for producing an optical film of the present invention, such an optical film of the present invention can be easily produced.

Hereinafter, the present invention will be described in detail by showing embodiments and exemplifications. However, the present invention is not limited to the embodiments and exemplifications shown below, and may be implemented by being arbitrarily modified within the scope of the claims of the present invention and the scope of equivalents thereof.

In the present application, a "long" film means a film having a length of 5 times or more, preferably 10 times or more, specifically, a width of the film, and specifically, It has a length that allows it to be rolled up and stored or transported. The upper limit of the ratio of the length to the width of the film is not particularly limited, but may be 100,000 times or less, for example.

In the following description, the retardation Re in the in-plane direction of the film is a value represented by Re=(nx−ny)×d unless otherwise specified. Further, the phase difference 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 direction perpendicular to the thickness direction of the film (in-plane direction) and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the film and in the direction orthogonal to the nx direction. nz represents the refractive index in the thickness direction of the film. d represents the thickness of the film. The measurement wavelength is 550 nm unless otherwise specified.

[1. Optical film]
The optical film of the present invention is obtained by roughening at least one surface of a film containing an alicyclic structure-containing polymer.

[1.1. Optical film material]
The film containing the alicyclic structure-containing polymer may be usually made of a resin containing the alicyclic structure-containing polymer. Examples of the alicyclic structure-containing polymer include a crystalline alicyclic structure-containing polymer, a non-crystalline alicyclic structure-containing polymer and a specific block copolymer alicyclic structure-containing hydride. Polymers may be mentioned.

[1.1.1. Crystalline alicyclic structure-containing polymer]
The crystalline polymer (polymer having crystallinity) means a polymer having a melting point [that is, the melting point can be observed by a differential scanning calorimeter (DSC)].

The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the molecule and is a polymer obtained by a polymerization reaction using a cyclic olefin as a monomer or a hydrogenated product thereof. Further, the alicyclic structure-containing polymer may be used alone or in combination of two or more kinds at an arbitrary ratio.

Examples of the alicyclic structure contained in the alicyclic structure-containing polymer include a cycloalkane structure and a cycloalkene structure. Among these, the cycloalkane structure is preferable because an optical film having excellent properties such as thermal stability can be easily obtained. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, particularly preferably 15 or less. is there. When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance, and moldability are highly balanced.

In the alicyclic structure-containing polymer, the ratio of structural units having an alicyclic structure to all structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more. .. By increasing the proportion of the structural unit having an alicyclic structure in the alicyclic structure-containing polymer as described above, the effects of the present invention such as high flexibility can be further enhanced.
Further, in the alicyclic structure-containing polymer, the balance other than the structural unit having the alicyclic structure is not particularly limited and may be appropriately selected according to the purpose of use.

The weight average molecular weight (Mw) of the alicyclic structure-containing polymer is preferably 1,000 or more, more preferably 2,000 or more, preferably 1,000,000 or less, more preferably 500,000 or less. is there. The alicyclic structure-containing polymer having such a weight average molecular weight has an excellent balance between moldability and flexibility.

The molecular weight distribution (Mw/Mn) of the alicyclic structure-containing polymer is preferably 1.0 or more, more preferably 1.5 or more, preferably 4.0 or less, more preferably 3.5 or less. .. Here, Mn represents a number average molecular weight. The alicyclic structure-containing polymer having such a molecular weight distribution is excellent in moldability.
The weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn) of the alicyclic structure-containing polymer can be measured as a polystyrene conversion value by gel permeation chromatography (GPC) using tetrahydrofuran as a developing solvent.

The glass transition temperature Tg of the alicyclic structure-containing polymer is not particularly limited, but is usually 85° C. or higher and usually 170° C. or lower.

Examples of the alicyclic structure-containing polymer include the following polymers (α) to (δ). Among them, the polymer (β) is preferable as the crystalline alicyclic structure-containing polymer because it is easy to obtain an optical film having excellent flexibility.
Polymer (α): A ring-opening polymer of a cyclic olefin monomer, which has crystallinity.
Polymer (β): A hydrogenated product of the polymer (α) having crystallinity.
Polymer (γ): Addition polymer of cyclic olefin monomer, which has crystallinity.
Polymer (δ): a hydrogenated product of the polymer (γ), which has crystallinity.

Specifically, the alicyclic structure-containing polymer is a ring-opening polymer of dicyclopentadiene and has crystallinity, and a hydrogenated product of the ring-opening polymer of dicyclopentadiene and is crystalline. And a hydrogenated product of a ring-opening polymer of dicyclopentadiene, which has crystallinity. Here, the ring-opening polymer of dicyclopentadiene is such that the ratio of structural units derived from dicyclopentadiene to all structural units is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, Particularly preferably, it means 100% by weight of the polymer.

The cyclic olefin monomer that can be used for producing the polymer (α) and the polymer (β) is a compound having a ring structure formed of carbon atoms and having a carbon-carbon double bond in the ring. .. Examples of cyclic olefin monomers include norbornene-based monomers. Further, when the polymer (α) is a copolymer, a monocyclic olefin may be used as the cyclic olefin monomer.

The norbornene-based monomer is a monomer containing a norbornene ring. Examples of the norbornene-based monomer include bicyclo[2.2.1]hept-2-ene (common name: norbornene), 5-ethylidene-bicyclo[2.2.1]hept-2-ene (common name). : Ethylidene norbornene) and its derivatives (for example, those having a substituent on the ring); tricyclo[4.3.0.12.5]deca-3,7-diene (conventional name) : Dicyclopentadiene) and its derivatives; tricyclic monomers; 7,8-benzotricyclo[4.3.0.12,5]dec-3-ene (conventional name: methanotetrahydrofluorene: 1 , 4-methano-1,4,4a,9a-also called tetrahydrofluorene) and its derivatives, tetracyclo[4.4.0.12,5.17,10]dodeca-3-ene (common name: tetracyclod Decene), 8-ethylidenetetracyclo[4.4.0.12,5.17,10]-3-dodecene and derivatives thereof, and other 4-ring monomers; and the like.

Examples of the substituent in the above monomer include an alkyl group such as a methyl group and an ethyl group; an alkenyl group such as a vinyl group; an alkylidene group such as propane-2-ylidene; an aryl group such as a phenyl group; a hydroxy group; Acid anhydride group; carboxyl group; alkoxycarbonyl group such as methoxycarbonyl group; and the like. Moreover, the said substituent may have 1 type independently, and may have 2 or more types in arbitrary ratios.

Examples of monocyclic olefins include cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, cyclooctene and other cyclic monoolefins; cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, phenylcyclo. Cyclic diolefins such as octadiene; and the like.

As the cyclic olefin monomer, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio. When two or more cyclic olefin monomers are used, the polymer (α) may be a block copolymer or a random copolymer.

The cyclic olefin monomer may have an endo isomer and an exo stereoisomer. As the cyclic olefin monomer, either an endo form or an exo form may be used. Further, only one of the isomers of the endo isomer and the exo isomer may be used alone, or an isomer mixture containing the endo isomer and the exo isomer in an arbitrary ratio may be used. Above all, it is preferable to increase the proportion of one stereoisomer, because the crystallinity of the alicyclic structure-containing polymer is increased and a film having more excellent heat resistance is easily obtained. For example, the ratio of endo-form or exo-form is preferably 80% or more, more preferably 90% or more, and further preferably 95% or more. Moreover, since the synthesis is easy, it is preferable that the proportion of the endo form is high.

The polymer (α) and the polymer (β) can usually have higher crystallinity by increasing the degree of syndiotactic stereoregularity (ratio of racemo dyads). From the viewpoint of increasing the degree of stereoregularity of the polymer (α) and the polymer (β), the ratio of Racemo Dyad to the structural units of the polymer (α) and the polymer (β) is preferably 51%. The above is more preferably 60% or more, and particularly preferably 70% or more.

The ratio of racemo dyads can be measured by ¹³ C-NMR spectrum analysis. Specifically, it can be measured by the following method.
13C-NMR measurement of the polymer sample is performed by applying the inverse-gated decoupling method at 200° C. using orthodichlorobenzene-d ⁴ as a solvent. From the results of this 13 C-NMR measurement, the intensity ratio of the signal of 43.35 ppm derived from meso dyad and the signal of 43.43 ppm derived from racemo dyad was determined with the 127.5 ppm peak of orthodichlorobenzene-d4 as a reference shift. The racemo diad percentage of the polymer sample can be determined based on

The cyclic olefin monomer used for producing the polymers (γ) and (δ) is selected from the range shown as the cyclic olefin monomer usable for producing the polymer (α) and the polymer (β). Any may be used. Moreover, the cyclic olefin monomer may be used alone or in combination of two or more kinds at an arbitrary ratio.

In the production of the polymer (γ), as a monomer, an arbitrary monomer copolymerizable with the cyclic olefin monomer may be used in combination with the cyclic olefin monomer. Examples of the optional monomer include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, 1-butene, 1-pentene, and 1-hexene; aromatic ring vinyl compounds such as styrene and α-methylstyrene. Non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene and 1,7-octadiene; and the like. Of these, α-olefins are preferable, and ethylene is more preferable. In addition, one type of any monomer may be used alone, or two or more types may be used in combination at any ratio.

The ratio of the amount of the cyclic olefin monomer to the optional monomer is a weight ratio (cyclic olefin monomer: optional monomer), preferably 30:70 to 99:1, more preferably 50:. It is 50 to 97:3, and particularly preferably 70:30 to 95:5.

When two or more cyclic olefin monomers are used, and when the cyclic olefin monomer and any monomer are used in combination, the polymer (γ) may be a block copolymer and may be a random copolymer. It may be a copolymer.

The alicyclic structure-containing polymer having crystallinity as described above can be produced, for example, by the method described in International Publication No. 2016/067893.

The proportion of the alicyclic structure-containing polymer having crystallinity in the resin having crystallinity is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. By setting the proportion of the alicyclic structure-containing polymer having crystallinity to be at least the lower limit value of the above range, the flexibility of the optical film can be enhanced.

When the optical film of the present invention contains a crystalline polymer as the alicyclic structure-containing polymer, the crystallinity thereof is preferably 1% or more, more preferably 2% or more, still more preferably 3% or more. Is. By having such a high crystallinity, it is possible to impart high heat resistance and chemical resistance to the optical film. There is no upper limit to the crystallinity of the crystalline polymer, but it is usually 90% or less. When the crystallinity is equal to or less than the above upper limit, the transparency of the optical film can be easily improved. The crystallinity of a polymer can be measured by an X-ray diffraction method.

The melting point of the crystalline polymer is preferably 200°C or higher, more preferably 230°C or higher, and preferably 290°C or lower. By using a polymer having such a melting point, it is possible to obtain an optical film having a better balance between moldability and heat resistance.

[1.1.2. Amorphous alicyclic structure-containing polymer]
The non-crystalline alicyclic structure-containing polymer is a polymer having no crystallinity among the alicyclic structure-containing polymers described above. Examples of the monomer constituting the amorphous alicyclic structure-containing polymer, the same as the examples of the monomer constituting the crystalline alicyclic structure-containing polymer described above Can be mentioned. The non-crystalline alicyclic structure-containing polymer is obtained by polymerizing the above-mentioned monomers by a known polymerization method to give a polymer having a low degree of syndiotactic stereoregularity, a normal atactic polymer or It can be produced by using an isotactic polymer. The mode of polymerization may be either ring-opening polymerization or addition polymerization.

[1.1.3. Amorphous norbornene-based polymer]
When the amorphous alicyclic structure-containing polymer is other than the block copolymer hydride described later, specifically, a norbornene-based polymer, for example, the ring-opening weight of the norbornene-based monomer is Coupling, ring-opening copolymers of norbornene-based monomers with other monomers capable of ring-opening copolymerization, and hydrides thereof; addition polymers of norbornene-based monomers, copolymers with norbornene-based monomers Examples thereof include addition copolymers with other polymerizable monomers. Among these, hydrides of ring-opening polymers of norbornene-based monomers are particularly preferable from the viewpoint of transparency.
The norbornene-based polymer can be selected from the polymers disclosed in JP-A-2002-321302, for example.

When the amorphous alicyclic structure-containing polymer is a norbornene-based polymer, the weight average molecular weight (Mw) is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000. It is above, preferably 100,000 or less, more preferably 80,000 or less, and particularly preferably 50,000 or less.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the norbornene-based polymer can be measured by gel permeation chromatography using cyclohexane as a solvent, as a weight average molecular weight in terms of polyisoprene or polystyrene. If the sample does not dissolve in cyclohexane, toluene can be used in place of cyclohexane as the solvent.

[1.1.4. Block copolymer hydride]
The block copolymer hydride, which is an example of the alicyclic structure-containing polymer in the present invention, may be crystalline or non-crystalline, but is usually non-crystalline.

Specific examples of the block copolymer hydride include a specific block copolymer hydride [E]. The block copolymer hydride [E] is obtained by hydrogenating the carbon-carbon unsaturated bond of the main chain and side chain of the specific block copolymer [D] and the carbon-carbon unsaturated bond of the aromatic ring. It is a compound having the obtained structure. The block copolymer [D] consists of a specific polymer block [A] and a specific polymer block [B], or a specific polymer block [A] and a specific polymer block [C]. Consists of. The polymer block [A] is a polymer block containing a repeating unit [I] derived from an aromatic vinyl compound as a main component. The polymer block [B] is a polymer block containing a repeating unit [I] derived from an aromatic vinyl compound and a repeating unit [II] derived from a chain conjugated diene compound as a main component. The polymer block [C] is a polymer block containing a repeating unit [II] derived from a chain conjugated diene compound as a main component. In the present application, the "main component" means that its content is 50% by weight or more of the whole.
The repeating unit derived from a compound refers to a repeating unit having a structure obtained by polymerizing the compound. A hydride of a polymer refers to a substance having a structure obtained by hydrogenating the polymer. However, the repeating unit and the hydride are not limited depending on the production method.

The block copolymer [D] is preferably two or more polymer blocks [A] per molecule and one or more polymer blocks [B] or polymer blocks [C] per molecule. Those consisting of are preferred. When the block copolymer [D] has two or more polymer blocks [A], these may be the same as or different from each other. The weight average molecular weights of the two polymer blocks [A] contained in one molecule of the block copolymer [D] may be the same or different.

The weight average molecular weight Mw(A) of the polymer block [A] is 3,000 to 90,000, preferably 3,500 to 80,000, and more preferably 4,000 to 60,000. When the Mw(A) of the polymer block [A] is 3,000 or more, the mechanical strength of the hydride of the block copolymer [E] can be improved. On the other hand, when the Mw(A) of the polymer block [A] is 90,000 or less, the melt moldability of the block copolymer hydride [E] can be improved.

In the block copolymer [D], the weight fraction wA of all the polymer blocks [A] in the block copolymer [D] and the block copolymer weight of the polymer block [B] or the polymer block [C]. The weight fraction wB in the combined [C] preferably has a predetermined ratio. That is, the ratio of wA to wB (wA/wB) is preferably 50/50 or more, more preferably 53/47 or more, even more preferably 57/43 or more, while preferably 95/5 or less, more preferably It is 85/15 or less. By setting wA/wB to the above upper limit or less, flexibility can be imparted to the block copolymer hydride [E], and good mechanical strength can be imparted. By setting wA/wB to the above lower limit or more, good heat resistance can be imparted.

The hydrogenation rate of the block copolymer hydride [E] (ratio of all the unsaturated bonds of the block copolymer [D] that have been hydrogenated in the block copolymer hydride [E]) is preferably It is 90% or more, preferably 95% or more, more preferably 99% or more. The higher the hydrogenation rate, the better the weather resistance, heat resistance and transparency of the molded product. The hydrogenation rate of the block copolymer hydride [E] can be determined by ¹ H-NMR or comparison of peak areas by UV detector and RI detector by GPC. ¹ H-NMR can be specifically measured at 145° C. using orthodichlorobenzene-d4 as a solvent.

The molecular weight of the block copolymer hydride [E] is a polystyrene-equivalent weight average molecular weight (Mw) measured by GPC using THF as a solvent, preferably 40,000 or more, more preferably 41,000 or more, It may be more preferably 45,000 or more, preferably 150,000 or less, more preferably 130,000 or less, and even more preferably 100,000 or less. The molecular weight distribution (Mw/Mn) of the block copolymer hydride [E] is preferably 3 or less, more preferably 2 or less, and particularly preferably 1.5 or less. When Mw and Mw/Mn are set within the above ranges, the heat resistance and mechanical strength of the formed stretched film against changes in retardation are good.

Specific examples and production methods of the block copolymer hydride [E] include the specific examples and production methods disclosed in WO 2016/152871.

[1.1.5. Ratio of alicyclic structure-containing polymer]
When the optical film of the present invention is made of a resin containing an alicyclic structure-containing polymer, the ratio of the alicyclic structure-containing polymer in the resin is preferably 50% by weight or more, more preferably 70% by weight or more, Particularly preferably, it is 90% by weight or more. By setting the ratio of the alicyclic structure-containing polymer within the above range, advantages of the alicyclic structure-containing polymer such as high mechanical strength and good optical properties can be obtained.

[1.1.6. Optional components]
The resin constituting the optical film may contain any component in addition to the alicyclic structure-containing polymer.
Examples of optional components include crosslinking aids.
Examples of the crosslinking aid include oximes such as p-quinonedioxime and p,p′-dibenzoylquinonedioxime; ethylene dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, cyclohexyl methacrylate, acrylic acid/ Zinc oxide mixture, acrylates or methacrylates such as allyl methacrylate; vinyl monomers such as divinylbenzene, vinyltoluene, vinylpyridine; hexamethylene diallyl nadimide, diallyl itaconate, diallyl phthalate, diallyl isophthalate, triallyl cyanurate, triyl Allyl compounds such as allyl isocyanurate; maleimide compounds such as N,N'-m-phenylene bismaleimide and N,N'-(4,4'-methylenediphenylene)dimaleimide. As the crosslinking aid, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio. Allyl compounds are preferred from the viewpoint of improving the electrical properties, heat resistance, solvent resistance and the like of the resulting stretched film, and triallyl isocyanurate (TAIC) is most preferred from the viewpoint of thermal stability.

Examples of other optional components include stabilizers such as antioxidants, ultraviolet absorbers and light stabilizers; resin modifiers such as lubricants and plasticizers; coloring agents such as dyes and pigments; antistatic agents and the like. Examples include compounding agents. These compounding agents can be used alone or in combination of two or more, and the compounding amount thereof is appropriately selected within a range not impairing the object of the present invention.

[2. Method for producing optical film]
The method for producing an optical film of the present invention comprises a step of stretching a film containing an alicyclic structure-containing polymer, and a treatment step including at least one of the steps of thermosetting the film, and after the treatment step. Roughening at least one surface of the film. In the following description, the film containing the alicyclic structure-containing polymer before the treatment step may be referred to as a “raw film” for the sake of distinguishing it from the film after the treatment step. In addition, among the films that have undergone the treatment process, the film that has not undergone the roughening process may be referred to as a “pre-roughening film”, and the film that has undergone the roughening process may be referred to as a “roughened film”.

The raw film can be produced, for example, by molding a resin containing an alicyclic structure-containing polymer into a film shape. The method for molding the resin containing the alicyclic structure-containing polymer is not particularly limited, and known methods such as melt extrusion molding can be adopted.

The dimensions of the original film can be appropriately set so that an optical film as a product having a desired dimension can be obtained. From the viewpoint of production efficiency, the original film is preferably a long film. The thickness of the raw film is preferably 5 μm or more, more preferably 15 μm or more, while preferably 200 μm or less, more preferably 170 μm or less.

[2.1. Treatment process]
The treatment step is one of a step of stretching a film containing an alicyclic structure-containing polymer (stretching step) and a step of thermally curing a film containing an alicyclic structure-containing polymer (thermosetting step). Or both steps are included. When both the thermosetting step and the stretching step are included, either step may be performed first.

[2.1.1. Stretching process)
The stretching step may be any mode such as uniaxial stretching and biaxial stretching. When the film before the stretching process is a long film, the stretching direction is a longitudinal direction (direction parallel to the longitudinal direction of the long film), a transverse direction (width direction of the long film). Parallel direction) and an oblique direction (direction not vertical or horizontal).

The draw ratio is preferably 1.05 times or more, more preferably 1.1 times or more, while preferably 7 times or less, more preferably 6 times or less. The stretching temperature is preferably 80°C or higher, more preferably 100°C or higher, while preferably 200°C or lower, more preferably 180°C or lower.

By carrying out such a stretching treatment, a large-area film can be easily obtained. Further, when a film having a retardation is required as a product, such retardation can be easily obtained. On the other hand, when a film having a small retardation is required as a product, such a film can be easily prepared by employing, for example, the above-mentioned block copolymer hydride [E] as the alicyclic structure-containing polymer. Can be obtained. However, by carrying out such a stretching treatment, the obtained film can be a film that easily undergoes cohesive failure when subjected to tensile force in the thickness direction. Here, in the present invention, by roughening at least one surface of the film, it is possible to suppress the problem caused by cohesive failure, so while enjoying the advantages obtained by stretching, also peel strength Can be increased.

[2.1.2. Heat curing step)
The heat curing step, for example, when the film contains a crystalline alicyclic structure-containing polymer as the alicyclic structure-containing polymer, crystallizes the crystalline alicyclic structure-containing polymer contained in the film. In this step, a film containing a crystallized resin is obtained. In the heat curing step, the crystalline alicyclic structure-containing polymer is crystallized to obtain, for example, a film containing a crystallized resin having a crystallinity of 1% or more as a main component. The heat-curing step can be performed by bringing at least two edges of the film containing the alicyclic structure-containing polymer into a predetermined temperature range while holding the film in a tensioned state. Hereinafter, the film containing the alicyclic structure-containing polymer to be subjected to the heat curing step is also referred to as a “curing target film”.

The tensioned state of the film to be cured means a state in which the film to be cured is under tension. However, the tensioned state of the film to be cured does not include the state in which the film to be cured is substantially stretched. Further, “substantially stretched” means that the stretching ratio in either direction of the film to be cured is usually 1.1 times or more.

When holding the film to be cured, the film to be cured is held by a suitable holder. The holder may be one that can continuously hold the entire length of the edge of the film to be cured, or one that can be held intermittently at intervals. For example, the edges of the film to be cured may be intermittently held by the holders arranged at predetermined intervals.

In the heat curing step, the film to be cured is brought into a tense state by holding at least two edges of the film to be cured. This prevents deformation of the film to be cured due to heat shrinkage in the region between the held edges. In order to prevent deformation in a wide area of the film to be cured, it is preferable to hold edges that include two opposite edges so that the region between the held edges is in a tense state. For example, in the case of a rectangular sheet-shaped film to be cured, two opposing edges (for example, edges on the long side or edges on the short side) are held and the space between the two edges is held. By making the region of 10 in a tense state, it is possible to prevent the deformation of the entire surface of the film to be cured of the sheet. Further, in the long film to be cured, the two end sides (that is, the end sides on the long side) at the end portions in the width direction are held to make the region between the two end sides in a tense state. As a result, it is possible to prevent deformation on the entire surface of the long film to be cured. In the film to be cured which is prevented from being deformed as described above, even if stress is generated in the film due to heat shrinkage, the occurrence of deformation such as wrinkles is suppressed. When using a raw film that has been subjected to a stretching step as the film to be cured, it is possible to suppress deformation by holding at least two edges that are orthogonal to the stretching direction (in the case of biaxial stretching, the direction in which the stretching ratio is large). It will be more certain.

In order to more reliably suppress the deformation in the thermosetting step, it is preferable to hold more edges. Therefore, for example, in the case of a single film to be cured, it is preferable to hold all the edges. As a specific example, it is preferable to hold four edge sides in a rectangular sheet-shaped film to be cured.

As the holder capable of holding the edge of the film to be cured, a holder that does not contact the film to be cured at a portion other than the edge of the film to be cured is preferable. By using such a holder, an optical film having more excellent smoothness can be obtained.

Further, the holder is preferably one that can fix the relative positions of the holders in the thermosetting step. In such a holder, since the positions of the holders do not move relative to each other in the thermosetting step, it is easy to suppress substantial stretching of the film to be cured in the thermosetting step.

As a suitable holder, for example, as a holder for a rectangular film to be cured, a gripper such as a clip, which is provided at a predetermined interval in a mold and can hold an edge of the film to be cured, can be mentioned. Further, for example, as a holder for holding the two end sides at the end in the width direction of the long film to be cured, a gripper provided in the tenter stretching machine and capable of gripping the edge side of the film to be cured Is mentioned.

When a long film to be cured is used, the edge at the end of the film to be cured in the longitudinal direction (that is, the edge on the short side) may be held, but instead of holding the edge. Alternatively, both sides in the longitudinal direction of the crystallization-treated region of the film to be cured may be held. For example, a holding device may be provided on both sides of the region to be crystallized of the film to be cured in the longitudinal direction so that the film to be cured can be held in a tensioned state so as not to be thermally shrunk. Examples of such a holding device include a combination of two rolls and a combination of an extruder and a take-up roll. By applying tension such as transport tension to the hardening target film by these combinations, it is possible to suppress heat shrinkage of the hardening target film in the region to be crystallized. Therefore, if the above-mentioned combination is used as a holding device, the hardening target film can be held while being conveyed in the longitudinal direction, so that the optical film can be efficiently manufactured.

In the heat curing step, as described above, the film to be cured is tensioned while holding at least two edges of the film to be cured, and the film to be cured is a glass transition temperature Tg or higher of the alicyclic structure-containing polymer, an alicyclic ring. The temperature is not higher than the melting point Tm of the formula structure-containing polymer. In the film to be cured which has been heated to the above temperature, crystallization of the alicyclic structure-containing polymer proceeds. Therefore, a film containing the crystallized alicyclic structure-containing polymer is obtained by this heat curing step. At this time, the film containing the crystallized alicyclic structure-containing polymer is placed in a tense state while hindering the deformation, so that the crystallization can be promoted without impairing the smoothness of the film.

As described above, the temperature range in the heat curing step can be arbitrarily set within a temperature range of the glass transition temperature Tg or higher of the alicyclic structure-containing polymer and the melting point Tm or lower of the alicyclic structure-containing polymer. Above all, it is preferable to set the temperature so as to increase the crystallization speed. The temperature of the film to be cured in the heat curing step is preferably Tg+20°C or higher, more preferably Tg+30°C or higher, preferably Tm-20°C or lower, more preferably Tm-40°C or lower. By setting the temperature in the heat curing step to the upper limit of the above range or less, the cloudiness of the optical film can be suppressed, so that an optical film suitable for an optically transparent film can be obtained.

As the heating device used in the heat curing step, a heating device that can raise the atmospheric temperature of the film to be cured is preferable because it is not necessary to contact the heating device with the film to be cured. Specific examples of suitable heating devices include an oven and a heating furnace.

In the heat curing step, the treatment time for maintaining the film to be cured in the above temperature range is preferably 1 second or more, more preferably 5 seconds or more, preferably 30 minutes or less, more preferably 10 minutes or less. By allowing the alicyclic structure-containing polymer to sufficiently crystallize in the heat curing step, the flexibility of the optical film can be increased. Further, by making the treatment time not more than the upper limit of the above range, clouding of the optical film can be suppressed, so that an optical film suitable for an optically transparent film can be obtained.

[2.2. Roughening process)
The roughening step is a step of roughening at least one surface of the raw film (film before roughening) after the treatment step. In the roughening step, the maximum height Rz of the surface on at least one surface of the roughened film (roughened film) is 150 nm or more and 3000 nm or less, and the arithmetic average roughness Ra is 30 nm or more and 1000 nm or less. To roughen.

The roughening method of the film before roughening is not particularly limited, and any method capable of setting the surface roughness on at least one surface of the roughened film obtained after undergoing the roughening step in the above predetermined range is selected. sell. Examples of the roughening method include buff treatment, blast treatment, hairline treatment, and dry etching (corona discharge, plasma treatment, EUV exposure). Of these methods, the buffing is preferable from the viewpoints of high-speed processing and ensuring the cleanliness of the processing section. In the present invention, when the roughening process is performed by corona discharge treatment, plasma treatment, or the like, the roughening treatment is performed at a strength (for example, 1000 w/m ² ) higher than that in general corona discharge treatment and plasma treatment.

[3. Optical film properties]
[3.1. Rz and Ra on film surface]
At least one surface of the optical film of the present invention has a maximum height Rz of 150 nm or more and 3000 nm or less and an arithmetic average roughness Ra of 30 nm or more and 1000 nm or less. The maximum height Rz is preferably 200 nm or more, more preferably 300 nm or more, and preferably 2000 nm or less. The arithmetic average roughness Ra is preferably 40 nm or more, more preferably 45 nm or more, and preferably 700 nm or less.
For example, even when the alicyclic structure-containing polymer contained in the film is strongly oriented by stretching or the like to cause a cohesive failure portion, the surface of the film is adjusted so that Rz and Ra fall within the above ranges. Since the cohesive failure portion can be peeled off by roughening, the peel strength can be increased. In the present invention, the optical film may be roughened so that the surface roughness (Ra, Rz) of one surface or both surfaces is within the above range.

The arithmetic average roughness Ra and the maximum height Rz of the surface of the optical film can be measured using a color 3D laser microscope (VK-9700 manufactured by Keyence Corporation) according to JIS B 0601-2001.

[3.2. Internal haze]
The internal haze of the optical film of the present invention is preferably 5% or less, more preferably 3% or less, still more preferably 1% or less. When the internal haze is not more than the above upper limit, the transparency becomes high and it becomes suitable for use as an optical film such as a polarizer protective film.
The internal haze can be measured using, for example, a haze meter (“NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd.).

[3.3. Phase difference]
The retardation Re in the in-plane direction of the optical film of the present invention is preferably 3 nm or less, more preferably 2.5 nm or less, still more preferably 2 nm or less. The absolute value of the retardation Rth in the thickness direction of the optical film of the present invention is preferably 3 nm or less, more preferably 2.5 nm or less, still more preferably 2 nm or less. In the optical film of the present invention containing a block copolymer hydride as the alicyclic structure-containing polymer, it is preferable that the absolute values of the retardation Re in the in-plane direction and the Rth in the thickness direction are within the above ranges. ..

The absolute values of the retardation in the in-plane direction and the retardation in the thickness direction of the optical film can be measured at a measurement wavelength of 590 nm using “AxoScan” manufactured by AXOMETRICS as a measuring device. When the above measuring device is used, the retardation in the in-plane direction and the thickness direction of the optical film is calculated using the average refractive index of the optical film. Here, the average refractive index means an average value of refractive indexes in two directions which are in-plane directions of the optical film and are perpendicular to each other, and a refractive index in the thickness direction of the optical film.

[3.4. Size]
The size of the optical film of the present invention can be appropriately set so as to have a desired size as a product. In terms of production efficiency, the optical film of the present invention can be produced as a long film. The thickness of the optical film of the present invention is preferably 5 μm or more, more preferably 10 μm or more, while preferably 200 μm or less, more preferably 170 μm or less.

[4. Applications of optical film)
The optical film of the present invention has high mechanical strength and good optical properties due to the inclusion of the alicyclic structure-containing polymer. In addition, the optical film of the present invention has high peel strength from the adherend. Therefore, the optical film of the present invention can be suitably used as a protective film for protecting other layers in a display device such as a liquid crystal display device and an organic electroluminescence display device. In particular, the optical film of the present invention can function particularly well as a polarizer protective film that protects a polarizer in a polarizing plate.

When the optical film of the present invention is used as a polarizer protective film, an adhesive layer may be provided between the polarizer and the polarizer.

The polarizer to which the optical film of the present invention is applied is not particularly limited, and any known one can be used. Examples of the polarizer include those obtained by adsorbing a material such as iodine and a dichroic dye on a polyvinyl alcohol film and then stretching the polyvinyl alcohol film. Examples of the adhesive constituting the adhesive layer include those containing various polymers as base polymers. Examples of such base polymers include, for example, acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers.

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 may be implemented by being arbitrarily modified within the scope of the claims of the present invention and the scope of equivalents thereof.
In the following description, “%” and “parts” representing amounts are by weight unless otherwise specified. Further, the operations described below were performed under the conditions of normal temperature and normal pressure unless otherwise specified.

〔Evaluation method〕
[Measurement method of weight average molecular weight and number average molecular weight]
The weight average molecular weight and the number average molecular weight of the polymer were measured as polystyrene equivalent values using a gel permeation chromatography (GPC) system ("HLC-8320" manufactured by Tosoh Corporation). At the time of measurement, an H type column (manufactured by Tosoh Corporation) was used as a column, and tetrahydrofuran was used as a solvent. The temperature at the time of measurement was 40°C.

[Measurement method of glass transition temperature Tg and melting point Tm]
The sample heated to 300° C. in a nitrogen atmosphere was rapidly cooled with liquid nitrogen, and the glass transition temperature Tg and the melting point Tm of the sample were determined by using a differential operation calorimeter (DSC) to raise the temperature at 10° C./min.
Further, in the case of a block copolymer hydride having two or more Tg, a sample is press-molded to prepare a test piece having a length of 50 mm, a width of 10 mm and a thickness of 1 mm, which is based on JIS-K7244-4 method. Using a viscoelasticity measuring device (TAE Instruments Japan, Inc., ARES), the viscoelasticity spectrum was measured at a temperature rising rate of 5°C/min in the range of -100°C to +150°C. From this, two or more Tg's were determined. For example, when Tg is two, the glass transition temperature Tg1 derived from the soft segment was calculated from the peak top temperature on the low temperature side of the loss tangent tan δ, and the glass transition temperature Tg2 derived from the hard segment was calculated from the peak top temperature on the high temperature side.

[Method for measuring hydrogenation rate of crystalline polymer, and hydrogenation rate of block copolymer hydride]
The hydrogenation rate of the polymer was measured by ¹ H-NMR measurement at 145° C. using orthodichlorobenzene-d4 as a solvent.

[Method of measuring crystallinity of polymer]
The crystallinity of the polymer contained in the film was confirmed by X-ray diffraction according to JIS K0131. Specifically, using a wide-angle X-ray diffractometer (RINT 2000, manufactured by Rigaku Co., Ltd.), the diffraction X-ray intensity from the crystallized portion was determined, and from the ratio to the overall diffraction X-ray intensity, the following formula The crystallinity was determined according to (I).
Xc=K·Ic/It (I)
In the above formula (I), Xc represents the crystallinity of the test sample, Ic represents the diffraction X-ray intensity from the crystallized portion, It represents the overall diffraction X-ray intensity, and K represents the correction term.

[Peel strength measurement method]
As an adherend, a resin film containing a norbornene-based polymer (Zeonor film, glass transition temperature 160° C., thickness 100 μm, manufactured by Nippon Zeon Co., Ltd., not particularly stretched) was prepared. Corona treatment was applied to one surface of the film to be measured (films of Examples and Comparative Examples) and one surface of the adherend. An adhesive was attached to both the corona-treated surface of the film to be measured and the corona-treated surface of the adherend, and the surfaces to which the adhesive was attached were bonded to each other. At this time, as the adhesive, a UV adhesive CRB series (manufactured by Toyochem Co., Ltd.) was used. After that, an electrodeless UV irradiation device (manufactured by Heraeus) was used, UV irradiation was performed using a D bulb as a lamp under conditions of a peak illuminance of 100 mW/cm ² and an integrated light amount of 3000 mJ/cm ² to cure the adhesive. .. As a result, a sample film including the film to be measured and the adherend was obtained.

A 90 degree peel test was performed on the obtained sample film. That is, the sample film was cut into a width of 15 mm, and the film to be measured side was attached to the surface of the slide glass with an adhesive. At this time, a double-sided pressure-sensitive adhesive tape (manufactured by Nitto Denko Corporation, product number “CS9621”) was used as the pressure-sensitive adhesive. The high-performance digital force gauge ZP-5N (manufactured by Imada) is sandwiched by the adherend, and the adherend is pulled at a speed of 300 mm/min in the normal direction of the surface of the slide glass, and the pulling force is large. The peel strength was measured as the peel strength.

[Reference example: Evaluation of validity of peel strength measurement method]
An experiment was conducted to evaluate whether or not the measurement of the peel strength by the above-described measuring method can be said to reflect the evaluation of the peel strength when the adherend is a polarizer.
A polarizing film and an adhesive were prepared by the same method as that described in Example 1 of JP-A-2005-70140. Moreover, the pre-processed stretched film and the electron beam irradiation stretched film obtained in Example 1 of the present application were prepared as the films to be measured. Corona treatment was applied to one surface of the film to be measured, and this surface was attached to one surface of the polarizing film via an adhesive. A triacetyl cellulose film was attached to the other surface of the polarizing film via an adhesive. Then, it dried at 80 degreeC for 7 minutes, the adhesive was hardened, and the sample film was obtained. The obtained sample film was subjected to the same 90-degree peel test as in the above-mentioned [Method of measuring peel strength]. As a result, values of Fa and Fb similar to the values obtained in Example 1 of the present application were obtained. From this, it can be said that the measurement of the peel strength by the above-described measuring method reflects the evaluation of the peel strength when the adherend is a polarizer.

[Measuring method of internal haze of film]
The internal haze of the film was measured as follows.
First, a test piece was obtained by cutting out from the film into a size of 50 mm×50 mm. Subsequently, a cycloolefin film (“Zeonoa film” manufactured by Nippon Zeon Co., Ltd., thickness 40 μm) was attached to both surfaces of the test piece through a transparent optical adhesive film (“8146-2” manufactured by 3M Co., Ltd.) having a thickness of 50 μm. Then, a sample multilayer body having a layer structure of cycloolefin film/transparent optical adhesive film/test piece/transparent optical adhesive film/cycloolefin film was obtained. Then, the haze of the sample multilayer body was measured using a haze meter (“NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd.).

Separately, a reference laminate including a cycloolefin film, a transparent optical adhesive film, a transparent optical adhesive film, and a cycloolefin film was formed in this order. Then, the haze of this reference laminate was measured with the haze meter. The haze of the reference laminate measured was 0.04%. The haze of the reference laminate of 0.04% is the sum of the haze of two cycloolefin films and the haze of two transparent optical adhesive films.

The internal haze of the test piece was obtained by subtracting 0.04% of the sum of the haze value of two cycloolefin films and the haze value of two transparent optical adhesive films from the haze of the sample multilayer body.

[Measurement method of absolute value of retardation in the in-plane direction and retardation in the thickness direction]
The films of Examples and Comparative Examples were measured at a wavelength of 590 nm using a retardation measuring device (product name “Axoscan” manufactured by Axometric) to obtain in-plane retardation Re and thickness direction Re of the films of Examples. The absolute value of the phase difference Rth was calculated.

[Measurement of Maximum Height Rz and Arithmetic Average Roughness Ra of Optical Film]
The arithmetic average roughness Ra and the maximum height Rz of the surface of the optical film were measured according to JIS B 0601-2001 using a color 3D laser microscope (VK-9700 manufactured by Keyence Corporation).

[Production Example 1. Production of Hydrogenated Product of Ring-Opening Polymer of Dicyclopentadiene]
The pressure resistant reactor made of metal was thoroughly dried and then replaced with nitrogen. In this pressure resistant reactor made of metal, 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution having a dicyclopentadiene (end content of 99% or more) (30 parts as the amount of dicyclopentadiene), and 1- 1.9 parts of hexene was added, and the mixture was heated to 53°C.

To a solution prepared by dissolving 0.014 parts of tetrachlorotungsten phenylimide (tetrahydrofuran) complex in 0.70 parts of toluene, 0.061 parts of a 19% diethylaluminum ethoxide/n-hexane solution was added and stirred for 10 minutes. To prepare a catalyst solution.
This catalyst solution was added to the pressure resistant reactor to start the ring-opening polymerization reaction. Then, the reaction was carried out for 4 hours while maintaining 53°C to obtain a solution of a ring-opening polymer of dicyclopentadiene.
The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the obtained ring-opening polymer of dicyclopentadiene were 8,750 and 28,100, respectively, and the molecular weight distribution (Mw/Mn) obtained from them was obtained. Was 3.21.

To 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene, 0.037 parts of 1,2-ethanediol as a terminating agent was added, and the mixture was heated to 60° C. and stirred for 1 hour to stop the polymerization reaction. Let To this, 1 part of a hydrotalcite-like compound (“Kyoward (registered trademark) 2000” manufactured by Kyowa Chemical Industry Co., Ltd.) was added, heated to 60° C., and stirred for 1 hour. Then, 0.4 parts of a filter aid (“Radiolite (registered trademark) #1500” manufactured by Showa Chemical Industry Co., Ltd.) was added, and a PP pleated cartridge filter (“TCP-HX” manufactured by ADVANTEC Toyo Corp.) was used as an adsorbent. The solution was filtered off.

To 200 parts of a solution of a ring-opening polymer of dicyclopentadiene after filtration (30 parts of polymer), 100 parts of cyclohexane was added, and 0.0043 parts of chlorohydridocarbonyltris(triphenylphosphine)ruthenium was added to obtain hydrogen. The hydrogenation reaction was carried out at a pressure of 6 MPa and 180° C. for 4 hours. As a result, a reaction solution containing a hydrogenated product of a ring-opening polymer of dicyclopentadiene was obtained. The reaction solution was a slurry solution in which hydrogenated substances were deposited.

A hydrogenated product of a ring-opening polymer of crystalline dicyclopentadiene separated by separating the hydrogenated product and the solution contained in the above reaction solution using a centrifuge and drying under reduced pressure at 60° C. for 24 hours. 28.5 parts were obtained. The hydrogenation rate of this hydrogenated product was 99% or more, the glass transition temperature (Tg) was 95° C., and the melting point (Tm) was 262° C.

[Example 1]
(1-1. Preparation of resin)
An antioxidant (tetrakis[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl) was added to 100 parts of the hydrogenated product of the ring-opening polymer of dicyclopentadiene obtained in Production Example 1. ) Propionate]Methane; 1.1 parts of "Irganox (registered trademark) 1010" manufactured by BASF Japan Ltd.) were mixed to obtain a resin as a material for the film.

(1-2. Production of film before roughening)
The resin obtained in (1-1) was charged into a twin-screw extruder equipped with four die holes having an inner diameter of 3 mm. The resin was molded into a strand-shaped molded product by hot melt extrusion molding by the above-mentioned twin-screw extruder. This molded body was shredded with a strand cutter to obtain resin pellets. The operating conditions of the above twin-screw extruder are shown below.
・Barrel setting temperature: 270℃-280℃
・Die setting temperature: 250℃
・Screw rotation speed: 145 rpm
・Feeder rotation speed: 50 rpm

Subsequently, the obtained pellets were fed to a hot melt extrusion film forming machine equipped with a T die. The resin was extruded from the T-die and wound on a roll at a speed of 1 m/min to produce a long raw film (thickness 50 μm) made of the above resin. The operating conditions of the film forming machine are shown below.
・Barrel temperature setting: 280℃-290℃
・Die temperature: 270℃
・Screw rotation speed: 30 rpm
After that, the original film was cut into a size of 100 mm×100 mm, and a small biaxial stretching machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used to grip the four side edges of the film with clips, and a stretching temperature of 110° C. Fixed-end uniaxial stretching was continuously performed at a stretch ratio of 1.3 times to obtain a pre-roughening film. At this time, the crystallinity of the polymer in the film before roughening was 4%. When surface roughness was measured using a part of the obtained film before roughening as a sample, it was Ra (nm)=8 and Rz (nm)=30. The peel strength Fa was measured and found to be 0.1 N/m.

(1-3. Production and evaluation of roughened film)
As a surface roughening device, a buff roll having a count of 1000 was used, and one surface of the pre-roughening film was roughened, and the surface roughness was Ra (nm)=200, Rz (nm)=800. A roughened film was obtained. The peel strength Fb of this roughened film was measured and found to be 1.5 N/m.

[Example 2]
(2-1. Production of film before roughening)
Using a small biaxial stretching machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the raw film cut into a size of 100 mm×100 mm obtained in (1-2. Production of film before roughening) was used for four sides of the film. The end portion of the film was gripped with a clip, and a thermosetting treatment was performed at a temperature of 145° C. to obtain a pre-roughening film. When surface roughness was measured using a part of the obtained film before roughening as a sample, it was Ra (nm)=3 and Rz (nm)=12. The peel strength Fa was measured and found to be 0.1 N/m.

(2-2. Production and evaluation of roughened film)
As a surface roughening device, a buff roll equipped with a count of 1000 was used, and one surface of the film before roughening was subjected to a roughening treatment, and the surface roughness was Ra (nm)=220, Rz (nm)=860. To obtain a roughened film. The peel strength Fb of this roughened film was measured and Fb was determined to be 1.5 N/m.

[Example 3]
(3-1. Production of film before roughening)
Pellets of a resin containing a cycloolefin polymer (a resin of a norbornene polymer having a glass transition temperature of 126° C., manufactured by Zeon Corporation) were dried at 100° C. for 5 hours. The dried resin pellets were then fed into a single screw extruder. After the resin was melted in the extruder, it was extruded in sheet form from a T die onto a casting drum through a polymer pipe and a polymer filter and cooled. Thereby, a raw film having a thickness of 50 μm and a width of 500 mm was obtained. The raw film is cut into a size of 100 mm×100 mm, and a small biaxial stretching machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.) is used to grip the four side edges of the film with clips, and the stretching temperature is 145° C. and the stretching ratio is Fixed-end uniaxial stretching was continuously performed at 1.3 times to obtain a film before roughening. When surface roughness was measured using a part of the obtained film before roughening as a sample, it was Ra (nm)=4 and Rz (nm)=10. The peel strength Fa was measured and found to be 0.1 N/m.

(3-2. Production and evaluation of roughened film)
As a surface roughening device, a buff roll having a count of 1000 was used, and one surface of the film before roughening was roughened, and the surface roughness was Ra (nm)=300, Rz (nm)=900. To obtain a roughened film. The peel strength Fb of this roughened film was measured to find Fb, which was 1.1 N/m.

[Example 4]
(4-1. Block copolymer [D])
A fully dried and nitrogen-substituted stainless steel reactor equipped with a stirrer was charged with 256 parts of dehydrated cyclohexane, 25.0 parts of dehydrated styrene, and 0.65 part of n-dibutyl ether, and stirred at 60°C. 1.35 parts of n-butyllithium (15% cyclohexane solution) was added to initiate the polymerization reaction. Furthermore, the mixture was reacted at 60° C. for 60 minutes while stirring. The polymerization conversion rate at this time was 99.5% (measured by gas chromatography, the same applies below). Next, 50.0 parts of dehydrated isoprene was added, and stirring was continued at the same temperature for 30 minutes. The polymerization conversion rate at this time was 99%. Thereafter, 25.0 parts of dehydrated styrene was further added, and the mixture was stirred at the same temperature for 60 minutes. The polymerization conversion rate at this point was almost 100%. Then, 0.5 part of isopropyl alcohol was added to the reaction solution to stop the reaction, and a polymerization reaction solution containing the block copolymer [C] was obtained. The weight average molecular weight (Mw) of the obtained block copolymer [D] was 44,900, and the molecular weight distribution (Mw/Mn) was 1.03.

(4-2. Hydrogenated block copolymer [E])
The polymerization reaction solution obtained in (4-1) was transferred to a pressure-resistant reactor equipped with a stirrer, and a silica-alumina-supporting nickel catalyst (E22U, nickel loading 60%; manufactured by JGC Corporation) as a hydrogenation catalyst. ) 4.0 parts and 350 parts of dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, hydrogen was supplied while stirring the solution, and a hydrogenation reaction was carried out at a temperature of 170° C. and a pressure of 4.5 MPa for 6 hours.

After completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst. Pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], which is a phenolic antioxidant, was added to the filtrate (Koyo Chemical Laboratory Co., Ltd., product name "Songnox 1010"). ) 0.1 part of xylene solution 1.0 part was added and dissolved. Then, using a cylindrical concentrating dryer (manufactured by Hitachi, Ltd., product name "Contro"), the above solution is heated at a temperature of 260° C. and a pressure of 0.001 MPa or less, and cyclohexane, xylene, and other volatilized solvents are solvent The ingredients were removed. The molten polymer was continuously filtered at a temperature of 260° C. by a polymer filter (manufactured by Fuji Filter Co.) equipped with a stainless sintered filter having a pore diameter of 20 μm connected to a concentrating dryer, and then the molten polymer was formed into a strand from a die. After extrusion and cooling, a block copolymer hydride [E] was obtained by a pelletizer.

The obtained hydride of the block copolymer has a block containing a repeating unit derived from styrene (hereinafter referred to as "St" as appropriate) and a block containing a repeating unit derived from isoprene (hereinafter referred to as "Ip" as appropriate). ), and the weight ratio of each block was St:Ip:St=25:50:25. The block copolymer hydride [E] has an Mw of 45,100, an Mw/Mn of 1.04, a hydrogenation rate of the main chain and an aromatic ring of about 100%, a glass transition temperature Tg1 of −50° C., and a Tg2 of Tg2. It was 140°C.

(4-3. Preparation of resin)
100 parts of the block copolymer hydride [E] obtained in (4-2) and 5 parts of a cross-linking aid (Taike (manufactured by Nippon Kasei Co., Ltd.)) were mixed to prepare a resin as a material for the film. Obtained.

(4-4. Production of film before roughening)
A film before roughening was obtained in the same manner as in (1-2) of Example 1 except that the resin obtained in (4-3) was used instead of the resin obtained in (1-1). When surface roughness was measured using a part of the obtained film before roughening as a sample, it was Ra (nm)=7 and Rz (nm)=20. The peel strength Fa was measured and found to be 0.1 N/m.

(4-5. Production of roughened film)
In the same manner as in (1-3) of Example 1, a roughened film of Example 3 having surface roughness Ra (nm)=500 and Rz (nm)=1600 was obtained. The peel strength Fb of this roughened film was measured and found to be 2.1 N/m.

[Comparative Examples 1 to 3]
The film before roughening obtained in (1-2) of Example 1 was used as the film of Comparative Example 1, and the film before roughening obtained in (3-1) of Example 3 was used as the film of Comparative Example 2; The film before roughening obtained in (4-4) of Example 4 was used as the film of Comparative Example 3 and evaluated in the same manner as in each Example product.

Table 1 shows the evaluation results (surface roughness (Ra, Rz), peel strength, internal haze, retardation (Re, Rth)) of Examples and Comparative Examples.

From the results of Table 1, at least one surface of the film containing the alicyclic structure-containing polymer, the maximum height Rz is 150 nm or more and 3000 nm or less, and the arithmetic mean roughness Ra is 30 nm or more and 1000 nm or less. It was found that the roughening treatment provided an optical film having a high peel strength and useful as a polarizer protective film.

Claims (7)

A film containing an alicyclic structure-containing polymer, an optical film obtained by roughening at least one surface,
An optical film having a maximum height Rz of 150 nm or more and 3000 nm or less and an arithmetic average roughness Ra of 30 nm or more and 1000 nm or less on at least one surface. The optical film according to claim 1, which has an internal haze of 5% or less. The alicyclic structure-containing polymer is a block copolymer hydride [E],
The block copolymer hydride [E] is a hydride of the block copolymer [D],
The block copolymer [D] consists of a polymer block [A] and a polymer block [B], or consists of the polymer block [A] and a polymer block [C],
The polymer block [A] is a polymer block containing a repeating unit [I] derived from an aromatic vinyl compound as a main component,
The polymer block [B] is a polymer block containing a repeating unit [I] derived from an aromatic vinyl compound and a repeating unit [II] derived from a chain conjugated diene compound as a main component,
The optical film according to claim 1, wherein the polymer block [C] is a polymer block containing a repeating unit [II] derived from a chain conjugated diene compound as a main component. The optical film according to claim 3, wherein the retardation Re in the in-plane direction is 3 nm or less and the absolute value of the retardation Rth in the thickness direction is 3 nm or less. The optical film according to claim 1, wherein the alicyclic structure-containing polymer is crystalline and has a crystallinity of 1% or more. The optical film according to any one of claims 1 to 5, which is a polarizer protective film. It is a manufacturing method of the optical film of any one of Claims 1-6, Comprising:
A step of stretching a film containing an alicyclic structure-containing polymer, and a treatment step including at least one of the steps of thermosetting the film,
And a step of roughening at least one surface of the film that has undergone the treatment step.