JP2012179901A - Method of manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film excellent in phase difference uniformity and transparency, and having few local defects, using a propylene based resin.SOLUTION: A method of manufacturing the optical film made of a propylene based resin includes a step of nipping and pressing the molten film made of the propylene based resin, with an elastic roll and a casting roll. A part in contact with the molten film on the surface of the elastic roll is formed from a material containing a metal oxide and/or a semi-metal oxide, and a surface roughness (Ra) of the part is 0.04 to 0.12 μm.

Description

  The present invention relates to a method for producing an optical film. More specifically, the present invention is excellent in retardation uniformity and transparency, and has few local defects (hereinafter sometimes referred to as “local defects”). The present invention relates to a method for producing an optical film. Here, the local defect is a defect that is locally observed in the film, and is a defect derived from a small resin reservoir, and the shape thereof is a streak shape or an elliptical shape parallel to the extrusion direction of the film. Is mentioned.

In flat panel displays such as liquid crystal display devices, optical films such as a retardation film and a polarizer protective film are used to improve contrast and viewing angle. Optical films are required to have excellent retardation uniformity and transparency.
In recent years, a method for producing an optical film using a crystalline thermoplastic resin such as a propylene-based resin has been studied. For example, Patent Documents 1 and 2 show excellent transparency and thickness accuracy by sandwiching a molten film made of a propylene-based resin between a cooling roll having a specific temperature condition and a metal elastic roll having a specific temperature condition. A method for obtaining a raw film for retardation film is described.

JP 2009-90652 A JP 2009-90653 A

However, in the methods described in Patent Documents 1 and 2, local defects are generated in the obtained film, and in order to use the film as a retardation film original film, the defective portion must be avoided. There is a problem that the yield is poor.
An object of the present invention is to provide a method for producing an optical film that is excellent in retardation uniformity and transparency and has few local defects using a propylene-based resin in view of the above-described state of the prior art. is there.

As a result of intensive studies, the inventors have found that the present invention can solve the above problems, and have completed the present invention.
That is, the present invention is a method for producing an optical film made of a propylene-based resin, including a step of pressing a molten film made of a propylene-based resin between an elastic roll and a casting roll, A method in which the portion in contact with the molten film is formed of a material containing a metal oxide and / or a metalloid oxide, and the surface roughness (Ra) of the portion is 0.04 μm or more and 0.12 μm or less. It is related to.

  According to the present invention, an optical film having excellent retardation uniformity and transparency and few local defects can be produced.

It is a figure which shows an example of the preferable equipment arrangement | positioning used with the method of manufacturing the optical film of this invention.

The elastic roll used in the present invention is a roll having elasticity, and the portion in contact with the molten film on the surface of the elastic roll is formed of a material containing a metal oxide and / or a semimetal oxide, and The part has a surface roughness (Ra) of 0.04 μm or more and 0.12 μm or less. Hereinafter, the material containing metal oxide and / or metalloid oxide may be referred to as material (1).
As for the surface of an elastic roll, only the part which contact | connects a molten film may be formed from the material (1), and the whole surface may be formed from the material (1). The elastic roll may be a roll formed from the material (1), and is a roll having a portion formed from the material (1) on the surface of the roll formed from a material different from the material (1). May be.
As a roll formed of a material different from the material (1), a rubber roll, a metal roll, a roll in which a rubber roll is disposed inside a metal outer cylinder, a flexible thin metal outer cylinder, Examples thereof include a roll composed of a highly rigid metal inner cylinder fitted concentrically to the outer cylinder, and a cooling medium filled between the outer cylinder and the inner cylinder. A roll formed of a material different from the material (1) includes a roll in which a rubber roll is disposed inside a metal outer cylinder, a thin metal outer cylinder having flexibility, and a concentric inner fit with the outer cylinder. A roll having a metal outer cylinder is preferable, such as a roll made of a highly rigid metal inner cylinder and a cooling medium filled between the outer cylinder and the inner cylinder. Hereinafter, a metal roll and a roll having a metal outer cylinder may be collectively referred to as a metal elastic roll.

  It is preferable that an elastic roll is a roll which has the part formed from the material (1) on the surface of a metal elastic roll. As a method for producing such a roll, a method of providing a portion made of the material (1) on a desired portion of the surface of the metal elastic roll is preferable. This method is easy to manufacture an elastic roll in which the surface roughness of the portion formed from the material (1) satisfies the scope of the present invention. Examples of the metal elastic roll include a touch roll described in Japanese Patent No. 3422798, a metal belt (endless belt) described in Japanese Patent Application Laid-Open No. 7-040370, and a flexible material described in Japanese Patent Application Laid-Open No. 11-235747. A thin metal outer cylinder, a highly rigid metal inner cylinder that is concentrically fitted to the outer cylinder, and a roll that includes a cooling medium filled between the outer cylinder and the inner cylinder. Can be mentioned. The metal elastic roll should just have the surface formed with the metal. Examples of the material forming the surface of the metal elastic roll include silicon manganese-based, manganese chromium-based and chromium vanadium-based spring steel, stainless steel, nickel steel, chromium, nickel, nickel-phosphorus alloy, copper, and the like. When the metal elastic roll is a roll having a metal outer cylinder, the thickness of the outer cylinder is preferably 100 μm or more and 5000 μm or less. The metal elastic roll having the outer cylinder having such a thickness has flexibility, flexibility and resilience close to rubber elasticity. When the metal elastic roll is a roll in which a rubber roll is disposed inside a metal outer cylinder, the thickness of the outer cylinder is preferably 100 μm or more and 3000 μm or less. The metal elastic roll is a thin metal outer cylinder having flexibility, a highly rigid metal inner cylinder that is concentrically fitted to the outer cylinder, and cooling that is filled between the outer cylinder and the inner cylinder. In the case of a roll made of a medium, the thickness of the outer cylinder is preferably 2000 μm or more and 5000 μm or less.

  The metal outer cylinder may be a cylinder in which the surface of a metal cylinder is plated. Examples of the metal used for plating include chromium, nickel, nickel-phosphorus alloy, copper and the like. From the viewpoint of ease of mirror finishing, hard chrome plating is preferable. The hard chrome plating is a relatively thick plating mainly composed of chrome and is also called industrial chrome plating.

  As a method for plating the surface of a metal cylinder, for example, the cylinder surface is immersed in a bath containing a solution containing a metal used for plating, and the cathode and anode placed in the bath are energized to apply metal to the cylinder surface. The method of precipitating is mentioned. The metal layer formed on the surface of the cylinder may be polished. The thickness of the metal layer formed by plating is preferably 5 μm or more and 1000 μm or less. The hardness of the metal layer is usually Vickers hardness of 400 Hv or more and 1200 Hv or less. From the viewpoint of the elasticity and strength of the roll, the elastic roll in the present invention is a roll having a portion formed from the material (1) on the surface of the roll having an outer cylinder obtained by plating the surface of a metal cylinder. Preferably there is.

  As for the elastic roll used for this invention, only the part which contact | connects the molten film in the surface may be formed from the material (1), and the whole surface may be formed from the material (1). The material (1) may contain components other than metal oxides and metalloid oxides. The material (1) is preferably made of only a metal oxide or only of a metalloid oxide.

The metal oxide is an oxide of at least one metal selected from alkali metals, alkaline earth metals, transition metals, and base metals. For example, chromium oxide (Cr ₂ O ₃ ), aluminum oxide (Al ₂ O) ₃ ), zirconium oxide (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ) and the like.
A semi-metal oxide is an oxide of a substance having an intermediate property between a metal and a non-metal. Examples of the semimetal include boron, silicon, germanium, arsenic, tin, tellurium, and polonium. Examples of the metalloid oxide include silicon dioxide (SiO ₂ ).
It is also possible to use the aforementioned metal oxide and metalloid oxide in combination. For example, a material or the like with chromium oxide (Cr ₂ O _3), silicon dioxide (SiO ₂₎ and the main component thereof.

  Examples of commercially available materials containing metal oxide and / or metalloid oxide used in the present invention include ZACROM manufactured by Tocalo Corporation and Ultrachrome II manufactured by EDI Corporation.

In the case where the elastic roll is a roll having a portion formed from the material (1) on the surface of the roll formed from a material different from the material (1), Patent No. 2107844, Examples include the methods described in Japanese Patent No. 3220012, Japanese Patent No. 1521696, and Japanese Patent Laid-Open No. 63-487. For example, there is a method in which a colloid solution containing the material (1) is applied to the surface of a roll formed of a material different from the material (1) to form a layer made of the colloid solution, and then the layer is dried. It is done.
When the elastic roll is a roll having a portion formed from the material (1) on the surface of the roll formed from a material different from the material (1), the thickness of the portion formed from the material (1) is: It is preferably 0.2 nm or more and 200 nm or less, and more preferably 1 nm or more and 100 nm or less. If the thickness is less than 0.2 nm, it is difficult to form a portion formed from the material (1) uniformly on the roll, and the effect of reducing local defects of the film to be produced tends to be poor. When the thickness exceeds 200 nm, it may take time and effort to polish the surface to obtain a desired surface roughness.

  The surface roughness (Ra) of the elastic roll used in the present invention is 0.04 μm or more and 0.12 μm or less, and preferably 0.05 μm or more and 0.10 μm or less. When the surface roughness is less than 0.04 μm, it becomes difficult to obtain a film with few local defects, and when it exceeds 0.12 μm, the surface roughness of the elastic roll is transferred to the film, and used as an optical film. It is difficult to obtain a film that can be used. The surface roughness (Ra) can be measured by the method described in JIS B 0601.

  The casting roll used in the present invention is a roll for taking a molten film and solidifying by cooling. Examples of the casting roll include a roll whose surface is plated with hard chrome, nickel, nickel phosphorus alloy, copper, or a roll sprayed with ceramic. The surface roughness (Ra) of the casting roll is preferably 0.12 μm or less, more preferably 0.08 μm or less. It is preferable that the surface of the casting roll is also formed of a material (1) containing a metal oxide and / or a semimetal oxide at a portion in contact with the molten film. When such a casting roll is used, the film is easily peeled off from the roll, so that the film can be stably run on the production line. The entire surface of the casting roll is preferably formed from the material (1).

  Examples of the optical film include a polarizer protective film, a prism sheet, a retardation film precursor, and the like. The retardation film precursor is an unstretched film and indicates a film that becomes a retardation film by stretching the film.

  Examples of the propylene-based resin include a propylene homopolymer, a copolymer of propylene and one or more comonomers selected from the group consisting of ethylene and an α-olefin having 4 to 20 carbon atoms. Moreover, these mixtures may be sufficient. Examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1- Butene, 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene, 1-octene, 2- Ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-propyl-1-heptene, 2-methyl-3-ethyl-1-heptene, 2,3,4-trimethyl-1-pentene, 2- Propyl-1-pentene, 2, -Diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadacene, 1-octathecene, 1-nonadecene Etc. As the propylene-based resin, a propylene homopolymer, a propylene / ethylene copolymer, a propylene / 1-butene copolymer, a propylene / 1-pentene copolymer, a propylene / 1-hexene copolymer, 1-octene copolymer, propylene / ethylene / 1-butene copolymer or propylene / ethylene / 1-hexene copolymer. When the propylene-based resin in the present invention is a copolymer of propylene and one or more comonomers selected from the group consisting of ethylene and an α-olefin having 4 to 20 carbon atoms, the resin is a random copolymer. It may be a coalescence or a block copolymer. When the propylene-based resin is a copolymer, the content of comonomer-derived structural units in the copolymer is preferably more than 3% by weight and 40% by weight or less from the viewpoint of the balance between transparency and heat resistance of the film. More preferably, it is more than 5% by weight and 25% by weight or less. In addition, when it is a copolymer of 2 or more types of comonomers and propylene, it is preferable that the total content of the structural unit derived from all the comonomer contained in this copolymer is in said range.

  Propylene-based resin production methods include a method of homopolymerizing propylene using a known polymerization catalyst, or one or more comonomers selected from the group consisting of ethylene and α-olefins having 4 to 20 carbon atoms and propylene. And a method of copolymerizing these. Known polymerization catalysts include, for example, (1) a Ti-Mg catalyst comprising a solid catalyst component containing magnesium, titanium and halogen as essential components, and (2) a solid catalyst component containing magnesium, titanium and halogen as essential components. In addition, a catalyst system in which an organoaluminum compound is combined with a third component such as an electron donating compound as necessary, (3) a metallocene catalyst, and the like. Among these catalyst systems used for the production of propylene polymers, the catalyst system in which an organic aluminum compound and an electron donating compound are combined with a solid catalyst component containing magnesium, titanium and halogen as the essential components is the most. Generally used. More specifically, the organoaluminum compound preferably includes triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride and tetraethyldialumoxane, and the electron donating compound is preferably cyclohexylethyldimethoxy. Examples thereof include silane, tert-butyl-n-propyldimethoxysilane, tert-butylethyldimethoxysilane, and dicyclopentyldimethoxysilane. Examples of the solid catalyst component containing magnesium, titanium and halogen as essential components include catalyst systems described in, for example, JP-A-61-218606, JP-A-61-287904, JP-A-7-216017, and the like. Is mentioned. Examples of the metallocene catalyst include catalyst systems described in Japanese Patent No. 2587251, Japanese Patent No. 2627669, and Japanese Patent No. 2668732.

  Polymerization methods used for the production of propylene-based resins include solvent polymerization using an inert solvent typified by hydrocarbon compounds such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, Examples include a bulk polymerization method using a monomer as a solvent, a gas phase polymerization method in which polymerization is performed in a gaseous monomer, and the bulk polymerization method or the gas phase polymerization method is preferable. These polymerization methods may be a batch method or a continuous method.

The stereoregularity of the propylene-based resin may be any of isotactic, syndiotactic, and atactic forms. The propylene resin is preferably a syndiotactic or isotactic propylene polymer from the viewpoint of heat resistance.
The propylene-based resin may be a blend of two or more types of propylene-based polymers having different molecular weights, proportions of structural units derived from propylene, tacticity, and the like, or may appropriately contain a polymer or an additive other than the propylene-based polymer.

  The melt flow rate (MFR) of the propylene-based resin is a value measured according to JIS K 7210 (test temperature and nominal load are in accordance with Annex B Table 1 of JIS K 7210), and usually 0.1 g / 10 min to 50 g. / 10 minutes, and preferably about 0.5 g / 10 minutes to 20 g / 10 minutes. By using a propylene resin having an MFR in such a range, a uniform film can be formed without applying a large load to the extruder.

  The molecular weight distribution of the propylene-based resin is usually 1 to 20. The molecular weight distribution is the ratio of the weight average molecular weight (Mw) of the resin to the number average molecular weight (Mn). Mw and Mn are measured and calculated using o-dichlorobenzene at 140 ° C. as the solvent and polystyrene as the standard sample.

  You may mix | blend a well-known additive with the propylene-type resin used for this invention in the range which does not inhibit the effect of this invention. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, and an antiblocking agent, and one or more of these may be used. Good.

  Antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine antioxidants (HALS), and, for example, phenolic and phosphorus antioxidant mechanisms in one molecule. Examples thereof include a composite type antioxidant having a unit. Examples of the UV absorber include UV absorbers such as 2-hydroxybenzophenone and hydroxytriazole, and UV blockers such as benzoate. Examples of the antistatic agent include polymer type, oligomer type, and monomer type agents. Examples of the lubricant include higher fatty acid amides such as erucic acid amide and oleic acid amide, higher fatty acids such as stearic acid, and metal salts thereof. Examples of the nucleating agent include a sorbitol nucleating agent, an organic phosphate nucleating agent, and a polymer nucleating agent such as polyvinylcycloalkane. Examples of the antiblocking agent include fine particles having a spherical shape or a shape close thereto.

  A method for producing the optical film of the present invention will be described in detail with reference to FIG. The method for producing the optical film of the present invention is a method for producing a molten film made of a propylene-based resin by sandwiching it between the elastic roll and the casting roll.

  First, a propylene-based resin is charged into the extruder 10 from a hopper (not shown). In order to suppress deterioration, the propylene-based resin introduced into the extruder from the hopper is preferably preliminarily dried in an inert gas atmosphere, preferably in a nitrogen atmosphere for about 1 to 10 hours in advance. Examples of the inert gas include nitrogen and argon. Nitrogen is preferable from the viewpoint of ease of handling. The drying temperature at this time is preferably 40 ° C. or higher and 130 ° C. or lower. Also in the extruder, it is preferable to use an inert gas atmosphere in order to suppress the deterioration of the resin.

  Next, the propylene-based resin is melted and kneaded by a screw (not shown) in the heated cylinder of the extruder 10 (hereinafter, sometimes referred to as “melting step”). The propylene-based resin melt-kneaded in the melting step is extruded into a film form from the discharge port of the T-die 12 (hereinafter sometimes referred to as “molding step”). The molding temperature in the melting step and the molding step is preferably 180 ° C. or higher and 300 ° C. or lower, and more preferably 220 ° C. or higher and 280 ° C. or lower. If the temperature of the resin is 180 ° C. or more and 300 ° C. or less, it becomes easy to obtain a film with small thickness unevenness, and the deterioration of the resin is reduced. It is easy to obtain a film with excellent appearance.

Next, the molten film is pressed between the elastic roll 14 and the casting roll 16 to be cooled and solidified.
On the surface of the elastic roll 14, a portion made of a material (1) containing a metal oxide and / or a semimetal oxide is formed. When the elastic roll is a roll having a portion formed from the material (1) on the surface of the roll formed from a material different from the material (1), the roll formed from a material different from the material (1) In some cases, micro-cracks may be generated on the surface. In that case, it is preferable to form a portion made of the material (1) so as to fill the microcracks with the material (1). The surface state of the elastic roll can be confirmed by X-ray photoelectron spectroscopy (hereinafter sometimes referred to as “XPS”) analysis. A sample is taken from a portion formed of the material (1), and a wide scan measurement is performed on the sample. As the X-ray source to be used, Al-Kα rays can be exemplified. A wide scan measurement is performed and an element is identified from the obtained spectrum, and a high resolution measurement is performed to obtain a narrow scan spectrum. From this, it is derived what kind of atom is present in what kind of bond (estimated attribution), and what percentage of atoms in a certain bonded state is present (state ratio).

The pressure when the molten film is sandwiched between the elastic roll and the casting roll (hereinafter sometimes referred to as “linear pressure”) is determined by the pressure pressing the elastic roll 14 against the casting roll 16. The linear pressure is preferably 0.5 N / mm or more and 100 N / mm or less. When the linear pressure is 0.5 N / mm or more and 100 N / mm or less, it is easy to control the linear pressure uniformly, and since the linear pressure is relatively small, it is easy to obtain a film having a small retardation value.
As a method for controlling the linear pressure, a triangular wedge-shaped “claw” called a cotter is installed at a portion where the molten film is pinched, and the roll interval is adjusted by controlling the cotter, and the elastic roll 14 and casting. A general method is to apply a predetermined pressure to one or both of the rolls 16 using hydraulic pressure, air, or the like and press it until it comes into contact with the adjusted cotter. In addition, without using a cotter, in order to adjust the clearance between the bearing blocks of each of the pair of rolls, a screw is installed on at least one of the bearing portions of the pair of rolls, and the rotational speed of the screws is controlled mechanically. Examples include a method in which a melted film is pressure-bonded with a pair of rolls by adjusting a bearing block steplessly to a predetermined position, and a method in which a servo motor is used in a hydraulic system.

  Thereafter, the molten film is pinched by a roll and then cooled and solidified to form a film. The ears are slit (cut) as necessary, and wound by a winder. A film made of a propylene-based resin may have a protective film laminated on one side or both sides before slitting the ear part and / or after slitting. The thickness of the film made of the propylene-based resin is preferably 40 μm to 500 μm from the viewpoint that the effects of the present invention are best exhibited.

  The film made of the propylene-based resin obtained by the method of the present invention is non-oriented and highly transparent, so that it can be used as a polarizing plate protective film and can be used for various other liquid crystal members. In addition, a stretched film obtained by stretching a film made of a propylene-based resin obtained by the method of the present invention can be used as a retardation film as a medium-to-small size from a large liquid crystal panel such as a TV, a monitor for a personal computer, a car navigation system, a digital camera, or a mobile phone. It can be used widely for liquid crystal panels. A stretched film having a desired retardation can be produced by controlling the magnification for stretching a film made of a propylene-based resin. Examples of the stretching method include longitudinal stretching, lateral stretching, sequential biaxial stretching, and simultaneous biaxial stretching. In the case of sequential biaxial stretching, either longitudinal stretching is performed first, then lateral stretching, or lateral stretching is performed first, and then longitudinal stretching is performed.

  By the way, the polarizing plate protective film and the original film for retardation film are required to be non-oriented. Here, the term “non-oriented” means that the polymer molecular chains in the material made of the thermoplastic resin are not oriented at all and are in a disordered state. The degree of orientation can be evaluated by obtaining a retardation value, and the retardation value can be measured using a commercially available retardation meter. The retardation value of the original film for retardation film is preferably 0 nm to 50 nm as a value when the thickness is 100 μm. When the retardation value of the retardation film original film is within this range, when the retardation film original film is stretched and used as a retardation film, the retardation film original film has an initial position. Since the phase difference is small, it is easy to control the phase difference even if the stretching conditions are adjusted.

In the present invention, the molten film is sandwiched between the casting roll 16 and the elastic roll 14. Therefore, since both surfaces of the molten film are cooled by the elastic roll 14 and the casting roll 16, the molten film can be quickly cooled and solidified. According to the present invention, even when a propylene resin, which is a crystalline resin, is used as a film material, the molten film can be cooled and solidified before the propylene resin crystal grows. A film made of a propylene-based resin having transparency can be produced.
Moreover, in this embodiment, the elastically deformable roll 14 which has the part formed from the material containing the casting roll 16 and a metal oxide and / or a semimetal oxide on the surface is used. When the molten film is pinched with such a roll, an optical film with few local defects can be obtained. Local defects tend to occur with a period that is an integral multiple of the diameter of the elastic roll. Examples of the shape of the local defect include a stripe shape parallel to the film extrusion direction and an elliptical shape. Since the film obtained by the present invention has few such local defects, the entire film obtained can be used as a product.
Moreover, the film obtained by the method of the present invention has a small retardation, and there is almost no unevenness in the retardation in the width direction of the film. Such a film is suitable as an original film for retardation film.

Hereinafter, the present invention will be described in detail with reference to examples. Each characteristic value was measured and evaluated by the following method.
(transparency)
Transparency was evaluated by HAZE. HAZE was measured according to JIS K 7136.
(Phase difference value)
The obtained film was cut at 40 mm × 40 mm at 100 mm intervals from the center in the film width direction in both directions of the film edge. A total of 9 samples were cut out. The in-plane phase difference (R0) of the sample was measured using a phase difference meter (KOBRA-WPR) manufactured by Oji Scientific Instruments.
(Phase difference uniformity)
When the value obtained by subtracting the minimum value from the maximum value of the measured phase difference values at all nine points was 20 nm or less, it was evaluated as “◯”, and when it exceeded 20 nm, it was evaluated as “X”.
(Local defect)
Evaluation was made by the number of defects of 1 mm or more corresponding to the following formula in the film 10 m.
Local defect = (longest side of the local defect + longest defect length of 90 degrees with the longest side of the local defect) / 2
(Surface roughness)
Arithmetic average roughness (Ra) was measured by a method described in JIS B 0601 using a surface roughness meter (Surfcom 130A) manufactured by Tokyo Seimitsu Co., Ltd. The value of Ra is the surface roughness in the present invention.
(XPS analysis)
Wide scan measurement and high resolution measurement were performed using Surface Science Instruments (S-Probe ESCA Model 2803). Here, the information depth is 6 to 7 nm, and the detectable element is Li or more. The binding energy, estimated state ratio, and estimated attribution were determined from the high-resolution measurement results. The binding energy is a value obtained by standardizing CC and CH as 284.6 eV. The state ratio is expressed in atomic percent (Atominc%).

[Example 1]
An apparatus as shown in FIG. 1 was used. The elastic roll 14 was a roll in which a layer 14d made of a material containing silicon dioxide (Ultra Chrome II manufactured by EDI) was formed on the entire surface of the thin metal outer cylinder 14b whose surface was hard chrome plating. XPS analysis was performed to confirm the surface state of the elastic roll. The results are shown in Table 1. The XPS analysis result on the surface of the elastic roll 14 showed that the peak derived from SiOx (x = 2) of the silicon compound was present and the state ratio of the peak derived from the Si—O bond was high. This indicates that the layer 14d made of a material containing a metalloid oxide is formed on the surface of the elastic roll. The elastic roll used had a surface roughness (Ra) of 0.05 μm.
Propylene-based resin (propylene-ethylene random copolymer, ethylene content = 4.6% by weight, melt flow rate (hereinafter also referred to as MFR) = 8.0, melting point = 138 ° C., Nobrene W151 manufactured by Sumitomo Chemical Co., Ltd. ) Was melt kneaded in a 75 mmΦ extruder heated to 250 ° C., and a molten film made of a propylene-based resin was discharged from a T die to a casting roll. The temperature from the adapter installed after the extruder to the T die was set to 250 ° C. The temperature of the molten resin at the discharge port 12a portion of the T die 12 was 250 ° C. Then, the molten film was taken out while being clamped by the elastic roll 14 and the casting roll 16 shown in FIG. The molten film was cooled and solidified by the elastic roll 14, the casting roll 16, and the cooling roll 18 to become a film made of a propylene-based resin having a thickness of 100 μm. Here, the temperature of the elastic roll 14 was set to 120 ° C., and the temperature of the casting roll 16 was set to 20 ° C. Table 2 shows the evaluation results of the film made of the obtained propylene-based resin.

[Example 2]
As the elastic roll, propylene was produced in the same manner as in Example 1, except that an elastic roll whose surface was formed of the same material containing silicon dioxide as in Example 1 and whose surface roughness Ra was 0.09 μm was used. A film made of a resin was obtained. The results are shown in Table 1.

[Comparative Example 1]
As an elastic roll, a roll having a thin metal outer cylinder 14b whose surface is hard chrome plating was used. The elastic roll did not have a portion made of the material (1) on the surface. The surface roughness (Ra) of the elastic roll was 0.03 μm. A film made of a propylene-based resin was obtained in the same manner as in Example 1 except that the elastic roll was used. The results are shown in Table 1. Moreover, the XPS analysis of the elastic roll surface was implemented similarly to Example 1. FIG. The results are shown in Table 1. It is shown that there is no peak derived from SiOx (x = 2) which is a silicon compound.

[Comparative Example 2]
As an elastic roll, a roll having a thin metal outer cylinder 14b whose surface is hard chrome plating was used. The elastic roll did not have a portion made of the material (1) on the surface. (Ra) of the elastic roll was 0.08 μm. A film made of a propylene-based resin was obtained in the same manner as in Example 1 except that the elastic roll was used. The results are shown in Table 1.

[Comparative Example 3]
As the elastic roll, a roll in which a layer made of a material containing silicon dioxide (Ultra Chrome II manufactured by EDI) was formed on the entire surface of the thin metal outer cylinder 14b whose surface was hard chrome plating. The surface roughness (Ra) of the elastic roll was 0.02 μm. A film made of a propylene-based resin was obtained in the same manner as in Example 1 except that the elastic roll was used. The results are shown in Table 1.

  In each of Examples 1-2 and Comparative Examples 1-3, the retardation value was 35 nm or less, and the orientation was small and good. In addition, the phase difference uniformity was small and good “◯”. In terms of transparency, the total HAZE was excellent at 0.4% or less. In Comparative Example 1 and Comparative Example 2 using a metal elastic roll in which a material containing a metalloid oxide is not formed, and in Comparative Example 3 using a metal elastic roll having a small surface roughness (Ra), there are local defects. Occurred. On the other hand, in Example 1, although it occurred in one place, it hardly occurred. In Example 2, local defects did not occur at all, and the product could be obtained over the entire surface of the film.

※１：試料中のC1s電子準位から放出された光電子ピークに基づく分析結果。
※２：試料中のO1s電子準位から放出された光電子ピークに基づく分析結果。
※３：試料中のSi2p電子準位から放出された光電子ピークに基づく分析結果。
※４：試料中のCr2p 3/2電子準位から放出された光電子ピークに基づく分析結果。
※５：試料中のZn2p 3/2電子準位から放出された光電子ピークに基づく分析結果。
※６：試料中のBa3d 5/2電子準位から放出された光電子ピークに基づく分析結果。

* 1: Analysis results based on photoelectron peaks emitted from the C1s electron level in the sample.
* 2: Analysis results based on the photoelectron peak emitted from the O1s electron level in the sample.
* 3: Analysis results based on the photoelectron peak emitted from the Si2p electron level in the sample.
* 4: Analysis results based on the photoelectron peak emitted from the Cr2p 3/2 electron level in the sample.
* 5: Analysis results based on the photoelectron peak emitted from the Zn2p 3/2 electron level in the sample.
* 6: Analysis results based on the photoelectron peak emitted from the Ba3d 5/2 electron level in the sample.

DESCRIPTION OF SYMBOLS 10 Extruder 12 T die 12a Discharge port 14 Elastic roll 14a Metal inner cylinder 14b Thin metal outer cylinder 14c Fluid axial cylinder 16 Casting roll 18 Cooling roll H Air gap F Film 14d The part formed from material (1)

Claims (2)

A method for producing an optical film made of a propylene-based resin,
Including a step of sandwiching a molten film composed of a propylene-based resin with an elastic roll and a casting roll,
A portion in contact with the molten film on the surface of the elastic roll is formed of a material containing a metal oxide and / or a semimetal oxide, and the surface roughness (Ra) of the portion is 0.04 μm or more and 0 A method of 12 μm or less.   The method for producing an optical film according to claim 1, wherein the metalloid oxide is silicon oxide.

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