JP2010228296A - Optical laminate film and method of manufacturing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical film stably manufacturing an optical film while avoiding rupture and cracking, and to provide an optical laminate film for use therein. <P>SOLUTION: The optical laminate film comprises a surface protection film laminated over at least one side of an optical film containing an acrylic resin having an imide ring structure in its main chain. The adhesion of a surface of the surface protection film in contact with the optical film at 23&deg;C is within the range of 0.02-0.4 N/50 mm width. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an optical laminated film composed of an optical film and a surface protective film, and an optical film manufacturing method using the optical laminated film.

  Acrylic resins represented by polymethyl methacrylate (hereinafter referred to as “PMMA”) are excellent in optical performance and have been applied to various optical materials as optically isotropic materials with high light transmittance, low birefringence, and low retardation. ing. In recent years, with the progress of flat displays such as liquid crystal display devices, plasma displays, organic EL display devices, infrared sensors, optical waveguides, etc., the demand for heat resistance of optical transparent polymer materials has increased. However, high heat resistance has been demanded.

  As acrylic resins having heat resistance (hereinafter referred to as “heat-resistant acrylic resins”), acrylic resins having an imide ring structure in the main chain are known, and various optical materials, particularly optical films, have been developed. ing. For example, an acrylic resin having a maleimide ring copolymerized with maleimides in the main chain (see, for example, Patent Document 1) has a property of expressing a phase difference upon stretching. A retardation film containing an acrylic resin having in the main chain is disclosed. In addition, an acrylic resin having a glutarimide ring in the main chain (see, for example, Patent Document 5) is also being studied for application to optical film applications such as a polarizer protective film.

JP 2001-146506 A Japanese Patent Laid-Open No. 3-23404 Japanese Patent Laid-Open No. 5-288929 JP 2007-31537 A Japanese Patent Laid-Open No. 2006-337569

  However, since the optical film containing an acrylic resin having an imide ring structure in the main chain described in Patent Documents 1 to 5 lacks flexibility, the film is easily broken or cracked, and it is difficult to stably manufacture the film. The problem that there is.

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing an optical film that can be stably produced while suppressing breakage and cracks, and an optical laminated film used in the method. Is to realize.

  In order to solve the above problems, an optical laminated film according to the present invention is an optical laminated film in which a surface protective film is laminated on at least one surface of an optical film containing an acrylic resin having an imide ring structure in the main chain. And the adhesive force in 23 degreeC of the surface which contact | connects the said optical film in the said surface protection film is a laminated film for optics in the range of 0.02 N / 50mm width or more and less than 0.4 N / 50mm width.

  According to the said structure, since the surface protection film is laminated | stacked on the optical film, the fracture | rupture and a crack of an optical film can be suppressed. For this reason, the fracture | rupture and the crack of a film which may arise when winding up in roll shape or conveying can be suppressed.

  Furthermore, since the surface protective film has a predetermined adhesive force, the film can be prevented from cracking when the surface protective film is peeled off.

  Therefore, according to the said structure, there exists an effect that the optical film excellent in the external appearance can be provided, and the optical laminated | multilayer film which can be conveyed stably etc. can be provided.

  In the laminated optical film according to the present invention, the optical film is preferably an unstretched film having a thickness in the range of 20 μm to 600 μm.

  According to the said structure, especially in the unstretched film lacking in a softness | flexibility, the fracture | rupture and crack at the time of roll winding, conveyance, and peeling off a surface protection film can be prevented, and it can manufacture stably.

  In the laminated optical film according to the present invention, the optical film is preferably a stretched film having a thickness in the range of 20 μm to 100 μm.

  According to the above configuration, even if the flexibility is improved by stretching, the film is insufficient in strength because the thickness is thin, preventing breakage and cracking at the time of roll winding, transportation and peeling of the surface protection film, It can be manufactured stably.

  In the laminated optical film according to the present invention, the surface protective film preferably has a thickness in the range of 20 μm to 50 μm.

  According to the said structure, the influence on the winding process of the film thickness precision of a surface protection film is suppressed, and a uniform roll-shaped film is obtained.

  Furthermore, since the surface protection film has high flexibility, local stress applied to the optical film when it is peeled off from the optical film can be relaxed, so that the optical film can be prevented from being broken and stably manufactured.

  The optical film manufacturing method according to the present invention is a method for manufacturing an optical film including a step of laminating a surface protective film on an optical film including an acrylic resin having an imide ring structure in the main chain in order to solve the above-described problem. And it is a manufacturing method in the range whose adhesive force in 23 degreeC of the surface which contacts the said optical film in the said surface protection film is 0.02 N / 50mm width or more and less than 0.4 N / 50mm width.

  According to the said method, since the process of sticking a surface protection film on an optical film is included, the fracture | rupture and a crack of an optical film can be suppressed. Specifically, since the optical film lacks flexibility (flexibility), it tends to be broken or cracked when traveling on a portion with a large curvature of the manufacturing apparatus or when it is wound into a roll. By applying the surface protective film, the optical film can be prevented from being broken or cracked. Thereby, an optical film can be manufactured stably.

  Furthermore, since the said surface protection film has the adhesive force in the said range, the fracture | rupture and the crack of a film at the time of peeling a surface protection film can be suppressed.

  Therefore, according to the said method, there exists an effect that the optical film excellent in the external appearance can be manufactured stably.

  As described above, the optical laminated film according to the present invention is an optical laminated film in which a surface protective film is laminated on at least one surface of an optical film containing an acrylic resin having an imide ring structure in the main chain. In the surface protective film, the adhesive film at 23 ° C. of the surface in contact with the optical film is an optical laminated film having a range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width.

  For this reason, there exists an effect that the optical film excellent in the external appearance can be provided, and the optical laminated film which can be conveyed stably etc. can be provided.

  Further, as described above, the method for producing an optical film according to the present invention is a method for producing an optical film including a step of laminating a surface protective film on an optical film containing an acrylic resin having an imide ring structure in the main chain. Thus, the surface protective film is a production method in which the adhesive force at 23 ° C. of the surface in contact with the optical film is in the range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width.

For this reason, there exists an effect that the optical film excellent in the external appearance can be manufactured stably.

  Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and modifications other than the following examples can be made as appropriate without departing from the spirit of the present invention. .

  In this specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, “main component” means containing 50% by mass or more, and “ppm” is in terms of mass unless otherwise specified. For example, 10,000 ppm means 1% by mass. In addition, “weight” is treated as a synonym for “mass”, “weight%” is treated as a synonym for “mass%”, and “A to B” indicating a range indicates A or more and B or less.

  In addition, the “film” in this specification includes both a film-like material and a sheet-like material. Although the film thickness of the said optical film is not specifically limited, It is preferable to exist in the range of 20 micrometers or more and 600 mm or less.

  An optical laminated film according to the present invention is an optical laminated film in which a surface protective film is laminated on at least one surface of an optical film containing an acrylic resin having an imide ring structure in the main chain, the surface protective film In the optical laminated film, the adhesive force at 23 ° C. of the surface in contact with the optical film is in the range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width.

  Moreover, the manufacturing method of the optical film which concerns on this invention is a manufacturing method of an optical film including the process of laminating | stacking a surface protection film on the optical film containing acrylic resin which has an imide ring structure in a principal chain, Comprising: Said surface protection It is a manufacturing method within the range whose adhesive force in 23 degreeC of the surface which contacts the said optical film in a film is 0.02 N / 50mm width or more and less than 0.4 N / 50mm width.

(I) Acrylic resin having an imide ring structure in the main chain The acrylic resin having an imide ring structure in the main chain is not particularly limited, and a (meth) acrylic acid type having an imide ring structure in a known main chain A thermoplastic resin can be used.

  Examples of acrylic resins include resins obtained by polymerizing monomers (compositions) containing acrylic acid, methacrylic acid and derivatives thereof and derivatives thereof.

  Preferable specific examples of the (meth) acrylic acid derivative include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. T-butyl acid, n-hexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2, (meth) acrylic acid 2, Examples include 3,4,5,6-pentahydroxyhexyl and 2,3,4,5-tetrahydroxypentyl (meth) acrylate. These may use only 1 type and may use 2 or more types together. Of these, methyl (meth) acrylate is most preferred because of its excellent thermal stability.

  The lower limit of the content ratio of the structural units derived from acrylic acid, methacrylic acid and derivatives thereof in the acrylic resin is preferably 3% by weight or more, more preferably 5% by weight or more, and particularly preferably 10% by weight or more. Further, the upper limit is preferably less than 97% by weight, more preferably less than 95% by weight, and still more preferably less than 90% by weight.

  The acrylic resin having an imide ring structure in the main chain has an imide ring structure in the main chain. The imide ring structure is, for example, a maleimide-derived ring structure, an itaconimide-derived ring structure, or a glutarimide ring structure. For example, N-phenylmaleimide, N-cyclohexylmaleimide and N-methylmaleimide and other maleimides (derivatives) and N-phenylitaconimide and other itaconic imides (derivatives) may be copolymerized, and the main chain may be cyclized after polymerization. It can be obtained by introducing a glutarimide ring structure or a maleimide-derived ring structure into the molecular chain (also referred to as the main skeleton or main chain in the polymer).

  The content ratio of the imide ring structure in the acrylic resin having an imide ring structure is preferably 3% by weight or more, more preferably 5% by weight or more, and particularly preferably 10% by weight or more. If it is 3% by weight or less, the heat resistance may be insufficient. Further, the upper limit is preferably less than 97% by weight, more preferably less than 95% by weight, and still more preferably less than 90% by weight.

  The lower limit of the content ratio of the structural unit derived from the (meth) acrylic acid derivative in the acrylic resin having an imide ring structure and the content ratio of the imide ring structure is preferably 30% by weight or more, more preferably 50% by weight or more, More preferably, it is 70 weight% or more, Most preferably, it is 90 weight% or more. The upper limit is preferably less than 100% by weight, more preferably less than 99% by weight.

  The acrylic resin having an imide ring structure in the main chain may be copolymerized with other copolymerizable monomer components, or may have a structural unit derived from other monomer components. Specific examples of other monomer components that can be copolymerized include aromatic vinyl monomers such as styrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, vinyltoluene, α-methylstyrene, and methallyl alcohol. , Allyl alcohol, allyl alcohol such as 2-hydroxymethyl-1-butene, 2- (hydroxyalkyl) acrylic acid ester such as methyl 2- (hydroxyethyl) acrylate, 2- (hydroxyethyl) acrylic acid and the like 2- (Hydroxyalkyl) acrylic acid, nitrile monomers such as acrylonitrile, vinyl esters such as vinyl acetate, N-vinylpyrrolidone, N-vinylimidazole, N-vinylacetamide, N-vinylformaldehyde, N-vinylcaprolactam, N -Vinylcarbazole and the like It is.

  The acrylic resin having an imide ring structure in the main chain preferably has a glass transition temperature in the range of 110 ° C. or higher and 200 ° C. or lower, and the acrylic resin is generally recognized as a heat-resistant acrylic resin by the traders. The glass transition temperature is more preferably in the range of 115 ° C. or higher and 180 ° C. or lower, and still more preferably in the range of 120 ° C. or higher and 160 ° C. or lower. When the glass transition temperature is higher than 200 ° C., the fluidity of the molten resin is deteriorated, so that the film tends to be difficult to mold. In general, substances that can be made into glass are generally in a low-temperature glass state and in a high-temperature supercooled liquid state, with a narrow temperature range inherent to the substance as a boundary, thermal expansion coefficient, electrical conductivity, Temperature coefficient such as viscosity and other physical quantities change rapidly. The glass transition temperature refers to the temperature range at this boundary, and is the temperature at which the polymer molecule begins to undergo micro-Brownian motion. Although there are various measuring methods for the glass transition temperature, in this specification, it is defined as a temperature obtained by a midpoint method according to ASTM-D-3418 using a differential scanning calorimeter (DSC).

  The acrylic resin having an imide ring structure in the main chain preferably has a melt flow rate measured at a test temperature of 240 ° C. and a load of 10 kg, preferably 1 to 100 g / 10 minutes, more preferably 3 to 100 g / 10 minutes, It is preferably 5 to 50 g / 10 minutes, particularly preferably 10 to 50 g / 10 minutes. If it is less than 1 g / 10 minutes, the moldability may become poor, which is not preferable. On the other hand, if it is more than 100 g / 10 min, the mechanical properties, flexibility, surface hardness, etc. of the obtained optical film may decrease, which is not preferable.

  The acrylic resin having an imide ring structure in the main chain preferably has a weight average molecular weight in the range of 1,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000. More preferably, it is in the range of 10,000 to 500,000, particularly preferably in the range of 50,000 to 500,000.

  The total amount of residual volatile components contained in the acrylic resin having an imide ring structure in the main chain is preferably 5,000 ppm or less, more preferably 2,000 ppm or less. If the total amount of residual volatile components is more than 5,000 ppm, it may be colored due to alteration during molding, foaming, or molding defects such as silver streak.

  The acrylic resin having an imide ring structure in the main chain is not particularly limited and can be produced by a known production method. As a method for introducing an imide ring structure into the main chain, for example, maleimide such as N-phenylmaleimide, N-cyclohexylmaleimide and N-methylmaleimide, and itaconimide such as N-phenylitaconimide may be copolymerized. Further, after polymerization of the acrylic resin, a glutarimide ring structure, a maleimide-derived ring structure, or the like may be introduced into the molecular chain (also referred to as the main skeleton or main chain in the polymer).

  The method for producing an acrylic resin having an imide ring structure in the main chain is not particularly limited, and a monomer composition containing a (meth) acrylic acid ester is polymerized using a conventionally known method. That's fine. If necessary, maleimides (derivatives) such as N-phenylmaleimide, N-cyclohexylmaleimide and N-methylmaleimide and itaconic imides (derivatives) such as N-phenylitaconimide may be copolymerized. You may copolymerize (meth) acrylic acid etc. which form a ring structure by cyclization reaction. Moreover, it is not specifically limited, You may copolymerize with the other monomer component which can be copolymerized. Specific examples of other monomer components that can be copolymerized include aromatic vinyl monomers such as styrene and α-methylstyrene, nitrile monomers such as acrylonitrile, vinyl esters such as vinyl acetate, and the like. Is mentioned.

  The polymerization temperature and the polymerization time vary depending on the type of monomer (monomer composition) used, the ratio of use, and the like. Preferably, the polymerization temperature is in the range of 0 ° C. to 150 ° C., and the polymerization time is 0.00. It is in the range of 5 hours to 20 hours, more preferably, the polymerization temperature is in the range of 80 ° C. to 140 ° C., and the polymerization time is in the range of 1 hour to 10 hours.

  In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran Etc., and only one of these may be used, or two or more may be used in combination. When manufacturing an acrylic resin having an imide ring structure in the main chain, if the boiling point of the solvent used is too high, the residual volatile content of the finally obtained acrylic resin will increase, so the boiling point is 50 ° C. or higher. The thing within the range of 200 degrees C or less is preferable.

  During the polymerization reaction, a polymerization initiator may be added as necessary. Although it does not specifically limit as a polymerization initiator, For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amyl Organic peroxides such as peroxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2, Azo compounds such as 4-dimethylvaleronitrile), and the like. These may be used alone or in combination of two or more. What is necessary is just to set the usage-amount of a polymerization initiator suitably according to the combination of the monomer to be used, reaction conditions, etc., and it does not specifically limit.

  When carrying out the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 60% by mass or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 60% by mass, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture and controlled to be 60% by mass or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 50% or less, still more preferably 45% by weight or less. Note that if the concentration of the polymer in the polymerization reaction mixture is too low, the productivity is lowered. Therefore, the concentration of the polymer in the polymerization reaction mixture is preferably 10% by mass or more, and more preferably 20% by mass or more. It is more preferable.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and the polymerization solvent may be added continuously or intermittently. By controlling the concentration of the produced polymer in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed, and in particular, to increase the ring content and improve the heat resistance. Even when the ratio of hydroxyl groups and ester groups in the molecular chain is increased, gelation can be sufficiently suppressed.

  The polymerization solvent to be added may be the same type of solvent used during the initial charging of the polymerization reaction or may be a different type of solvent, but is the same as the solvent used during the initial charging of the polymerization reaction. It is preferable to use different types of solvents. Further, the polymerization solvent to be added may be only one type of solvent or a mixed solvent of two or more types.

  In the polymerization reaction mixture obtained when the polymerization reaction is completed, a solvent is usually contained in addition to the obtained polymer. When the cyclization reaction of the main chain is performed after the polymerization, it is not necessary to completely remove the main solvent and take out the polymer in a solid state, and it is preferable to perform the subsequent cyclization step in a state containing the solvent. . If necessary, a solvent suitable for the subsequent cyclization step may be added again after the solid is taken out.

  The hue of the acrylic resin obtained by the polymerization reaction is not particularly limited, but it is preferable that it is transparent and has a lower yellowing degree because it does not impair the original characteristics of the acrylic resin. For example, the acrylic resin has a haze value of 3 or less, more preferably 2 or less, and most preferably 1 or less when formed into a 3 mm thick molded body. The molded article has a YI (yellow index) value of 10 or less, preferably 5 or less.

When the cyclization reaction of the main chain is performed after the polymerization, a cyclization reaction catalyst (cyclization catalyst) can be added as necessary to promote the cyclization reaction. The cyclization reaction can also be performed in heat treatment and the devolatilization process described in detail below. The devolatilization process requires volatile components such as solvents, residual monomers, and alcohol by-produced by the cyclization reaction. The removal process under reduced pressure heating conditions. If this removal treatment is insufficient, the residual volatile components in the produced resin increase, resulting in problems such as coloration due to alteration during molding, and molding defects such as bubbles and silver streaks.

  In the case of using the devolatilization step throughout the cyclization reaction, the apparatus to be used is not particularly limited, but a devolatilizer comprising a heat exchanger and a devolatilization tank in order to more effectively perform the present invention. It is preferable to use an extruder with a vent, or a devolatilizer and an extruder arranged in series, and use a devolatilizer or vented extruder comprising a heat exchanger and a devolatilizer. Is more preferable.

  The reaction treatment temperature in the case of using a devolatilizer comprising the heat exchanger and the devolatilizer is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the reaction treatment temperature is lower than 150 ° C, the cyclization reaction may be insufficient and the residual volatile matter may increase, and if it is higher than 350 ° C, coloring or decomposition may occur.

  When using the devolatilizer comprising the heat exchanger and the devolatilizer, the pressure during the reaction treatment is preferably within the range of 931 to 1.33 hPa (700 to 1 mmHg), and 798 to 66.5 hPa (600 to More preferably within the range of 50 mmHg). When the pressure is higher than 931 hPa, there is a problem that volatile components including alcohol easily remain, and when the pressure is lower than 1.33 hPa, there is a problem that industrial implementation becomes difficult.

  When using the extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  In the case of using the vented extruder, the reaction treatment temperature is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the temperature is lower than 150 ° C, the cyclization reaction may be insufficient and the residual volatile matter may increase. If the temperature is higher than 350 ° C, coloring or decomposition may occur.

  In the case of using the extruder with a vent, the pressure during the reaction treatment is preferably within a range of 931 to 1.33 hPa (700 to 1 mmHg), and more preferably within a range of 798 to 13.3 hPa (600 to 10 mmHg). When the pressure is higher than 931 hPa, there is a problem that volatile components including alcohol easily remain, and when the pressure is lower than 1.33 hPa, there is a problem that industrial implementation becomes difficult.

  In addition, in the case of using the devolatilization step throughout the cyclization reaction, as described later, the physical properties of the acrylic resin having an imide ring structure in the main chain obtained under severe heat treatment conditions may deteriorate. It is preferable to use a catalyst for a dealcoholization reaction and under a mild condition as much as possible using a vented extruder or the like.

  In the case of using the devolatilization step throughout the cyclization reaction, preferably, the polymer obtained in the polymerization step is introduced into the cyclization reaction device together with the solvent. It may be passed through the reaction apparatus such as a vented extruder.

  You may perform the form which does not use a devolatilization process over the whole process of a cyclization reaction, but uses together only in a part of process. For example, the apparatus for producing the polymer is further heated, and if necessary, a part of the devolatilization step is used together to advance the cyclization reaction to some extent in advance, and then the devolatilization step is used at the same time. In this form, a cyclization reaction is performed to complete the reaction.

  In the embodiment in which the devolatilization step is used throughout the cyclization reaction described above, for example, when the polymer is heat-treated at a high temperature close to 250 ° C. or higher using a twin screw extruder, Due to the difference, partial decomposition or the like occurs before the cyclization reaction occurs, and the physical properties of the acrylic resin having an imide ring structure in the main chain may be deteriorated. Therefore, if the cyclization reaction is allowed to proceed to some extent before performing the cyclization reaction using the devolatilization process at the same time, the reaction conditions in the latter half can be relaxed, and the resulting acrylic resin having an imide ring structure in the main chain It is preferable because deterioration of physical properties can be suppressed.

  As a particularly preferred form, the devolatilization step is started after a lapse of time from the start of the cyclization reaction, that is, the hydroxyl group and ester group present in the molecular chain of the polymer obtained in the polymerization step are cyclized in advance. There is a mode in which the cyclization reaction rate is raised to some extent by reaction, and then a cyclization reaction is carried out using the devolatilization step at the same time. Specifically, for example, the cyclization reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle-type reactor, and then a reactor equipped with a devolatilizer, for example, heat exchange Preferred is a mode in which the cyclization reaction is completed with a devolatilizer comprising a vessel and a devolatilization tank, an extruder with a vent, or the like. Particularly in this form, it is more preferable that a catalyst for the cyclization reaction is present.

  As described above, the cyclization reaction rate is raised to some extent by previously cyclizing the hydroxyl group and ester group present in the molecular chain of the polymer obtained in the polymerization step, and then the devolatilization step is simultaneously used in combination. The method for carrying out the cyclization reaction is a preferred form for obtaining an acrylic resin having an imide ring structure in the main chain. With this form, an acrylic resin having an imide ring structure in the main chain having a higher cyclization reaction rate, a higher glass transition temperature, and excellent heat resistance can be obtained.

  The reactor that can be employed in the cyclization reaction performed in advance before the cyclization reaction using the devolatilization process at the same time is not particularly limited, but preferably from an autoclave, a kettle reactor, a heat exchanger, and a devolatilization tank. A vented extruder suitable for a cyclization reaction in which a devolatilization step is used at the same time can also be used. More preferred are autoclaves and kettle reactors. However, even when using a reactor such as an extruder with a vent, by adjusting the temperature condition, barrel condition, screw shape, screw operating condition, etc. It is possible to carry out the cyclization reaction in the same state as the reaction state in the kettle reactor.

  In the cyclization reaction performed in advance before the cyclization reaction using the devolatilization step at the same time, preferably, a mixture containing the polymer and the solvent obtained in the polymerization step is added (i) by adding a catalyst. , A method of heating reaction, (ii) a method of heating reaction without a catalyst, and a method of performing the above (i) or (ii) under pressure.

  The “mixture containing a polymer and a solvent” to be introduced into the cyclization reaction in the cyclization step may be the polymerization reaction mixture obtained in the polymerization step, or may be used after the solvent is removed once. It means that a solvent suitable for the chemical reaction may be added again.

  Solvents that can be re-added during the cyclization reaction performed in advance prior to the cyclization reaction using the devolatilization process at the same time are not particularly limited. For example, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; methyl ethyl ketone, Ketones such as methyl isobutyl ketone; chloroform, DMSO, tetrahydrofuran and the like may be used, but the same type of solvent as that which can be used in the polymerization step is preferable.

  As the cyclization catalyst, basic cyclization catalysts such as metal salts and metal oxides can be used. The addition timing of the cyclization catalyst is not particularly limited, and it may be added at the beginning of the reaction, during the reaction, or both. The amount of the catalyst to be added is not particularly limited, but is preferably in the range of 0.001 to 5% by mass, more preferably in the range of 0.01 to 2.5% by mass, and still more preferably based on the mass of the polymer. It is in the range of 0.01 to 0.1% by mass, particularly preferably in the range of 0.05 to 0.5% by mass. The heating temperature and heating time in method (i) are not particularly limited, but the heating temperature is preferably room temperature or higher, more preferably 50 ° C. or higher, and the heating time is preferably in the range of 1 to 20 hours. More preferably, it is in the range of 2 to 10 hours. If the heating temperature is low, or if the heating time is short, the cyclization reaction rate decreases, which is not preferable. Further, if the heating time is too long, the resin may be colored or decomposed, which is not preferable.

  Examples of the method (ii) include a method of heating the polymerization reaction mixture obtained in the polymerization step as it is using a pressure-resistant kettle or the like. The heating temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. The heating time is preferably in the range of 1 to 20 hours, more preferably in the range of 2 to 10 hours. If the heating temperature is low, or if the heating time is short, the cyclization reaction rate decreases, which is not preferable. Further, if the heating time is too long, the resin may be colored or decomposed, which is not preferable.

  Both the above methods (i) and (ii) have no problem even under pressure depending on conditions. Moreover, in the case of the cyclization reaction performed in advance before the cyclization reaction using the devolatilization process at the same time, there is no problem even if a part of the solvent volatilizes spontaneously during the reaction.

  The mass reduction rate between 150 and 300 ° C. in dynamic TG measurement at the end of the cyclization reaction performed in advance before the cyclization reaction using the devolatilization process at the same time, that is, immediately before the start of the devolatilization process is 2%. The following is preferable, more preferably 1.5% or less, and still more preferably 1% or less. When the mass reduction rate is higher than 2%, the cyclization reaction rate does not rise to a sufficiently high level even if the cyclization reaction is carried out simultaneously with the devolatilization step, and the resulting main chain has an imide ring structure. There is a risk that the physical properties of the resin will decrease. In addition, when performing said cyclization reaction, in addition to a polymer, you may coexist other thermoplastic resins.

  The polymer obtained in the polymerization step is preliminarily cyclized to increase the cyclization reaction rate to some extent. You may perform the cyclization reaction which used the devolatilization process simultaneously, without isolate | separating the obtained polymer and solvent. Moreover, you may perform the cyclization reaction which used the devolatilization process simultaneously after passing through other processes, such as adding a solvent again after isolate | separating the said polymer as needed.

  The devolatilization step is not limited to being completed at the same time as the cyclization reaction, and may be completed after a lapse of time from the completion of the cyclization reaction.

As described above, the acrylic resin having an imide ring structure in the main chain can use a catalyst in the cyclization reaction. However, if the catalyst remains in the resin, the resin is heated. When this is done, foaming may occur. In order to prevent this foaming phenomenon, it is conceivable to add a deactivator. When the catalyst used in the cyclization reaction is a postponing substance, neutralization may be performed using an acidic substance in order to deactivate the catalyst remaining after the reaction. (II) Surface protective film The surface protective film which concerns on this Embodiment is a film which has the surface whose adhesive force in 23 degreeC exists in the range of 0.02 N / 50mm width or more and less than 0.4 N / 50mm width. The adhesive strength of the surface protective film is more preferably in the range of 0.02 N / 50 mm width or more and less than 0.15 N / 50 mm width, more preferably in the range of 0.02 N / 50 mm width or more and less than 0.1 N / 50 mm width. Is within.

  In this specification, the said adhesive force means the value measured by the 180 degree peeling test based on JISZ-0237. Specifically, PMMA (polymethyl methacrylate) is placed on a stainless steel plate, a test piece (surface protective film) is attached on PMMA, and the test piece is peeled off at a speed of 300 mm / min in the 180 ° direction. The load at four locations is measured at intervals of 20 mm, and the average value is taken as the adhesive strength.

  Examples of the surface protective film include films in which an adhesive layer is coated or coextruded on a substrate.

  Although there is no limitation in particular as said base material, Polyester resins, such as polyolefin resins, such as polyethylene and a polypropylene, a polyethylene terephthalate, etc. are mentioned, A polyolefin resin is preferable. When a polyolefin resin is used, since the flexibility of the film is high, local stress applied when it is peeled off from the optical film can be relieved, so that the optical film can be prevented from being broken and stably manufactured.

  The pressure-sensitive adhesive layer is not particularly limited as long as it can provide the above-mentioned adhesive force, EVA (ethylene-vinyl acetate copolymer), metallocene L-LDPE (a metallocene catalyst polymerized linear chain) Low density polyethylene) is preferred.

  The film thickness of the surface protective film is preferably in the range of 10 to 100 μm, more preferably in the range of 20 to 50 μm, and still more preferably in the range of 20 to 35 μm. If the thickness of the surface protective film is less than 10 μm, the strength is not sufficient. When the thickness exceeds 100 μm, the film thickness accuracy of the surface protective film may affect the uniformity of winding, and it may be difficult to produce a stable optical film. Since an excessive stress is easily applied, the optical film may be broken during manufacturing.

  The pressure-sensitive adhesive layer in the surface protective film may be provided over the entire surface in contact with the optical film, or provided only in part, as long as the surface protective film can be stably attached to the acrylic resin. May be.

(III) Manufacturing method of optical film <Film forming process>
The optical film according to the present embodiment can be obtained from the acrylic resin according to the present embodiment described above. The optical film may be produced by a molding method described later after taking out the acrylic resin, or may be continuously formed by a molding method described later without taking out the acrylic resin. May be.

  Examples of the film forming method for the acrylic resin include conventionally known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Of these film forming methods, the solution casting method (solution casting method) and the melt extrusion method are particularly suitable.

  Examples of the solvent used in the solution casting method (solution casting method) include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as cyclohexane and decalin; esters such as ethyl acetate and butyl acetate Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve and butyl cellosolve; ethers such as tetrahydrofuran and dioxane; dichloromethane, Halogenated hydrocarbons such as chloroform and carbon tetrachloride; dimethylformamide; dimethyl sulfoxide; and the like. These solvents may be used alone or in combination of two or more.

  Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method, an inflation method and the like, and the molding temperature at that time may be appropriately adjusted according to the glass transition temperature of the film raw material, and is not particularly limited. For example, it is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C.

  When forming a film by the T-die method, a roll-shaped film can be obtained by attaching a T-die to the tip of a known single-screw extruder or twin-screw extruder and winding the film extruded into a film. it can. At this time, it is also possible to perform uniaxial stretching by appropriately adjusting the temperature of the winding roll and adding stretching in the extrusion direction. Also, simultaneous biaxial stretching, sequential biaxial stretching, and the like can be performed by stretching the film in a direction perpendicular to the extrusion direction.

  The optical film according to the present embodiment may be an unstretched film or a stretched film. When it is a stretched film, it may be either a uniaxially stretched film or a biaxially stretched film. In the case of a biaxially stretched film, either a simultaneous biaxially stretched film or a sequential biaxially stretched film may be used. In the case of biaxial stretching, the mechanical strength is improved and the film performance is improved.

  In addition, it is preferable that the film thickness of the said optical film exists in the range of 20 micrometers or more and 600 micrometers or less. Moreover, when it is a stretched film, it is preferable to exist in the range of 20 micrometers or more and 100 micrometers or less.

  The optical film according to the present embodiment includes an acrylic resin having an imide ring structure in the main chain as a main component. Preferably in the range of 70% or more and 100% or less, more preferably in the range of 80% or more and 100% by mass or less, still more preferably in the range of 90% by mass or more and 100% by mass or less, particularly preferably 95% by mass or more and 100% by mass. % Or less.

  In the optical film according to the present embodiment, components other than an acrylic resin having an imide ring structure may be included in the main chain. Examples of components that can be included in addition to the acrylic resin having an imide ring structure include polymers (other polymers) other than acrylic resins having an imide ring structure, and other additives.

  Other polymers include, for example, acrylic polymers other than acrylic resins having an imide ring structure; olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene). Halogen-containing polymers such as vinyl chloride and vinyl chloride resins; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate, Polyesters such as polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; Polyetheretherketone; polysulfone; polyether sulfone; polyoxyethylene benzylidene alkylene; polyamideimide; and the like are; polybutadiene rubber, rubber-like polymer such as acrylic rubber ABS resin or ASA resin blended with. The content of the other polymer in the optical film is preferably in the range of 0% by mass to 50% by mass, more preferably in the range of 0% by mass to 40% by mass, and still more preferably 0% by mass to 30%. It is in the range of not more than mass%, particularly preferably in the range of not less than 0 mass% and not more than 20 mass%.

  Moreover, as the other polymer, a thermoplastic polymer that is thermodynamically compatible with an acrylic resin having an imide ring structure in the main chain is preferable. For example, a copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit, specifically, an acrylonitrile-styrene copolymer, a polyvinyl chloride polymer, or a methacrylic acid ester Examples thereof include a polymer containing 50% by mass or more.

  Examples of the other additives include antioxidants such as hindered phenols, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcements such as glass fibers and carbon fibers. Materials; UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate Flame retardants such as antimony oxide; antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; organic Fillers and inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants;

  The content of the other additives in the optical film is preferably in the range of 0% by mass to 5% by mass, more preferably in the range of 0% by mass to 2% by mass, and still more preferably 0% by mass to 0%. Within 5 mass% or less.

  The other polymers and additives are preferably melt-kneaded in advance with an acrylic resin before film formation.

<Surface protection film lamination process>
In the surface protective film laminating step, the surface protective film described above is laminated on the optical film obtained by the film forming step. It is preferable to affix the above-described surface protective film to the optical film.

  The method for attaching the surface protective film is not particularly limited, and includes, for example, a motor such as an unwinding machine (or unwinding machine) installed on the lower side or the upper side of the film line running on the film forming apparatus. Examples include a method of setting a surface protective film roll on the drive shaft and bonding the formed film and the surface protective film by pressing them with two rubber rolls.

  Moreover, the surface protective film may be bonded to only one side of the optical film, or may be bonded to both sides.

<Winding process>
In the winding step, the optical film (optical laminated film) on which the surface protective film is laminated is wound into a roll. More specifically, a winding core is set on a winding machine, the optical laminated film is wound around the winding core, and the winding speed is adjusted so as to be almost the same as the line speed of the optical laminated film. To do. Here, it is preferable to wind the optical laminated film into a roll shape by setting the tension taper to a ratio in the range of 5% to 30% and decreasing the tension as the roll diameter increases. In addition, the “tensile taper” in the present specification means a rate of decrease (decrease rate) in tension at the time when the film finishes winding with respect to the initial tension.

  The initial tension at the time of winding is appropriately set depending on the film thickness of the film to be wound, etc., and can be set, for example, in the range of more than 2N and less than 100N. Furthermore, the said winding speed can be set in the range of 1-100 m / min, for example.

  Conventionally, it is known to prevent winding deviation or loosening by giving a knurling of a certain thickness to a film (see, for example, JP-A-2002-212803). However, according to the method according to the present embodiment, the film roll can be prevented from being collapsed without giving knurling, and a film roll having a uniform shape can be produced.

  Moreover, since the surface protection film is laminated | stacked on the optical film, the laminated film for optics wound up in the said roll shape can carry out conveyance etc. suppressing the fracture | rupture and a crack peculiar to acrylic resin.

<Surface protection film peeling process>
The optical laminated film can be used as an optical film by peeling off the surface protective film.

  Here, since the adhesive force at 23 ° C. of the surface in contact with the optical film in the surface protective film is within a range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width, the surface protective film is peeled off. Breaking and cracking of the optical film can be suppressed.

  The method for peeling off the surface protective film is not particularly limited. For example, a torque motor or the like installed in a direction different from the traveling direction of the optical laminated film (for example, the lower side or the upper side of the optical laminated film) And a method of causing a winder equipped with a drive shaft to wind the surface protective film and peeling the surface protective film from the optical film.

  In the above description, the case where the optical laminated film is wound up in a roll shape has been described. However, the present invention is not limited to this. For example, the optical laminated film may be cut every predetermined length without being wound into a roll. If the step of adhering to the acrylic resin a surface protective film in which the adhesive force at 23 ° C. of the surface in contact with the optical film is in the range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width is included The substantially same effect as the embodiment can be obtained.

  However, when the laminated optical film is wound up in a roll shape as in this embodiment, the film can be manufactured more efficiently, so that the effect is particularly great.

(IV) Optical laminated film The optical laminated film according to the present embodiment is an optical laminated film in which a surface protective film is laminated on an optical film containing an acrylic resin having an imide ring structure in the main chain.

  That is, the optical laminated film according to the present embodiment is an optical laminated film in which the surface protective film according to the present embodiment is laminated on the optical film according to the present embodiment.

  In the optical laminated film according to the present embodiment, the adhesive force at 23 ° C. of the surface in contact with the optical film in the surface protective film is in the range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width. Preferably, it is in the range of 0.02 N / 50 mm width or more and less than 0.15 N / 50 mm width, and more preferably in the range of 0.02 N / 50 mm width or more and less than 0.1 N / 50 mm width. Here, the adhesive force means a value measured by a 180 ° peel test in accordance with JIS Z-0237 as described above. Specifically, PMMA (polymethyl methacrylate) is placed on a stainless steel plate, a test piece (surface protective film) is attached on PMMA, and the test piece is peeled off at a speed of 300 mm / min in the 180 ° direction. The load at four locations is measured at intervals of 20 mm, and the average value is taken as the adhesive strength.

  As described above, the method for producing an optical film according to the present invention is a method for producing an optical film including a step of laminating a surface protective film on an optical film containing an acrylic resin having an imide ring structure in the main chain, It is a manufacturing method of the optical film in which the adhesive force in 23 degreeC of the surface which contact | connects the said optical film in the said surface protective film exists in the range of 0.02 N / 50mm width or more and less than 0.4 N / 50mm width.

  For this reason, there exists an effect that the optical film excellent in the external appearance can be manufactured stably.

  An optical laminated film according to the present invention is an optical laminated film in which a surface protective film is laminated on an optical film containing an acrylic resin having an imide ring structure in the main chain, The adhesive force at 23 ° C. of the surface in contact with the optical film is in the range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width.

  For this reason, there exists an effect that the optical film excellent in the external appearance can be provided, and the optical laminated film which can be conveyed stably etc. can be provided.

Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments are appropriately combined. Embodiments obtained in this manner are also included in the technical scope of the present invention.

  Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to this. Hereinafter, for convenience, “part by mass” may be simply referred to as “part”, and “liter” may be simply referred to as “L”.

<Weight average molecular weight>
The weight average molecular weight was determined by polystyrene conversion of GPC (GPC system manufactured by Tosoh Corporation). Chloroform was used as the developing solution.

<Thermal analysis of resin>
Thermal analysis was performed using DSC (manufactured by Rigaku Corporation, apparatus name: DSC-8230) under the conditions of a sample of about 10 mg, a heating rate of 10 ° C./min, and a nitrogen flow of 50 cc / min. The glass transition temperature (Tg) was determined by the midpoint method according to ASTM-D-3418.
<Melt flow rate>
The melt flow rate was measured at a test temperature of 240 ° C. and a load of 10 kg based on JIS-K7210.

[Production Example 1]
In a 100 L stainless steel polymerization tank equipped with a submerged tank and a stirrer, 42.5 parts of methyl methacrylate, 5 parts of N-phenylmaleimide, 0.5 part of styrene, 50 parts of toluene, 0.2% acetic anhydride as organic acid In addition, 0.06 part of n-dodecyl mercaptan was added as a chain transfer agent, and nitrogen gas was bubbled for 10 minutes while stirring at 100 rpm, and then the temperature was raised under a nitrogen atmosphere.
When the temperature in the polymerization tank reached 100 ° C., 0.075 part of t-butyl peroxyisopropyl carbonate was added to the polymerization tank, and at the same time, 2 parts of styrene and t -The liquid mixture with 0.075 part of butyl peroxy isopropyl carbonate began to be added at a constant rate over 5 hours. The polymerization reaction was carried out at a polymerization temperature of 105 to 110 ° C. for 15 hours under reflux.
Thereafter, 9,10-dihydro-9-oxa-10-phosphanenanthrene-10-oxide (manufactured by Sanko Co., Ltd., trade name “HCA”) as a phosphorus-based antioxidant for the obtained polymerization solution. 0.1 wt%, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (“AO-60” manufactured by Asahi Denka) as a phenonol-based antioxidant is 0 0.02 wt% was added and mixed.
Next, the obtained polymerization solution is supplied to a vented 30 mm biaxial extruder controlled at a cylinder temperature of 240 ° C., vacuum degassed from the vent port, the extruded strand is pelletized, and the main chain has an imide ring structure An acrylic resin pellet (1A) was obtained.
The obtained acrylic resin pellet (1A) has a resin physical property of a weight average molecular weight of 100,000, a melt flow rate of 15 g / 10 min, a glass transition temperature of 132 ° C., 270 ° C., a shear rate of 100 (1 / The viscosity in s) was 390 Pa · s.

  The obtained pellet (1A) was charged into a single screw extruder with a vent having a φ65 mm, L / D = 32, barrier flight type screw. The temperature of the pellet (1A) was set to around 60 ° C. by blowing dehumidified air heated in a hopper. Further, a nitrogen introduction pipe was provided at the lower part of the hopper, and nitrogen gas was introduced into the extruder. While suctioning from the vent port at 40 Torr, the mixture was melt kneaded with a barrier flight screw. After melt-kneading, an optical film having an imide ring structure was formed on a main chain having a thickness of 350 μm by extrusion from a T die onto a 90 ° C. cooling roll using a gear pump.

[Example 1]
To the optical film obtained in Production Example 1, a surface protective film having a film thickness of 30 μm (trade name: Toraytec 7332, manufactured by Toray Film Processing Co., Ltd., substrate: polyolefin, adhesive strength at 23 ° C .: 0.07 N / 50 mm width) was pasted. Then, using a winding device (maximum winding width: φ600 mm), the initial tension is 50 N and the tension taper is 15%, and the film (optical laminated film) to which the surface protective film is attached is wound into a roll shape. I took it. In the winding of the optical laminated film, a roll-shaped optical laminated film could be obtained continuously for 100 hours or more without breaking the optical film.

  In addition, the roll-shaped winding of the optical laminated film is performed by using a core having an inner diameter of 76 mm until the winding diameter reaches 600 mm, and thereafter repeating the operation of replacing the roll and restarting the winding. It was.

  The obtained roll-shaped optical laminated film did not collapse and did not crack at the end of the roll. Also, the optical film was not broken when the surface protective film was peeled off.

[Comparative Example 1]
A surface protective film having a film thickness of 60 μm (trade name: Toraytec 7141, manufactured by Toray Film Processing Co., Ltd., substrate: polyolefin, adhesive strength at 23 ° C .: 0.50 N / 50 mm width) was used as the surface protective film. Except for the above, the same operation as in Example 1 was performed to produce a roll-shaped optical laminated film. The obtained roll-shaped optical laminated film did not collapse and was not cracked at the end of the roll, but cracked in the optical film when the surface protective film was peeled off.

[Comparative Example 2]
When the same operation as in Example 1 was performed except that the surface protective film was not attached, the film frequently cracked and fractured before reaching the winder, and could not be operated continuously. It was. Moreover, although the film which reached the winder did not collapse, both ends of the roll were cracked and a lot of fine film fragments adhered, so that only a product with a poor appearance was obtained.

[Comparative Example 3]
When the same operation as in Comparative Example 2 was performed except that the film was wound at a constant tension (50 N), roll roll collapse occurred in addition to cracks at both ends of the product roll.

[Example 2]
The optical film obtained in Production Example 1 was heated to a temperature of 130 ° C. and stretched 2.4 times in the longitudinal direction under auxiliary heating with an infrared heater. Next, the film was supplied to a tenter, stretched twice in the transverse direction at a temperature of 140 ° C., and biaxially stretched to produce an optical film having a thickness of 80 μm. On one side of this optical film, a surface protective film (trade name: Tretec 7332, manufactured by Toray Film Processing Co., Ltd., substrate: polyolefin, adhesive strength at 23 ° C .: 0.07 N / 50 mm width) is provided. Pasted. Then, using a winding device (maximum winding width: φ400 mm), initial tension is 80 N, tension taper is 15%, and the film (optical laminated film) to which the surface protective film is attached is wound into a roll. I took it. In the winding of the optical laminated film, a roll-shaped optical laminated film could be obtained continuously for 100 hours or more without breaking the optical film.

  In addition, the roll-shaped winding of the optical laminated film is performed by repeating the operation of using a core having an inner diameter of 152 mm until the winding diameter reaches 400 mm, then exchanging the roll and restarting the winding. It was.

  The obtained roll-shaped optical laminated film did not collapse and did not crack at the end of the roll. Also, the optical film was not broken when the surface protective film was peeled off.

[Comparative Example 4]
A surface protective film having a film thickness of 60 μm (trade name: Toraytec 7141, manufactured by Toray Film Processing Co., Ltd., substrate: polyolefin, adhesive strength at 23 ° C .: 0.50 N / 50 mm width) was used as the surface protective film. Except for the above, the same operation as in Example 2 was performed to produce a roll-shaped optical laminated film. The obtained roll-shaped optical laminated film did not collapse and did not crack at the end of the roll, but the optical film was broken when the surface protective film was peeled off.

[Comparative Example 5]
When the same operation as in Example 2 was performed except that the surface protective film was not attached, breakage occurred frequently before the film reached the winder, and continuous operation was not possible.

  As described above, by using the method for producing an optical film of the present invention, an optical film excellent in appearance can be produced stably. Therefore, this invention can be used suitably for manufacture of various optical films, such as a polarizer protective film, an antireflection film, retardation film, and a polarizing film, used for flat panel display apparatuses, such as a liquid crystal display device.

Claims (5)

An optical laminated film in which a surface protective film is laminated on at least one surface of an optical film containing an acrylic resin having an imide ring structure in the main chain,
A laminated film for optics in which the adhesive force at 23 ° C. of the surface in contact with the optical film in the surface protective film is in the range of 0.02 N / 50 mm width or more and less than 0.4 N / 50 mm width.   2. The optical laminated film according to claim 1, wherein the optical film is an unstretched film having a thickness in the range of 20 μm to 600 μm.   2. The optical laminated film according to claim 1, wherein the optical film is a stretched film having a thickness in the range of 20 μm to 100 μm.   The optical laminated film according to any one of claims 1 to 3, wherein the surface protective film has a thickness in a range of 20 µm to 50 µm. A method for producing an optical film comprising a step of laminating a surface protective film on an optical film comprising an acrylic resin having an imide ring structure in the main chain,
The manufacturing method of the optical film whose adhesive force in 23 degreeC of the surface which contact | connects the said optical film in the said surface protection film exists in the range of 0.02 N / 50mm width or more and less than 0.4 N / 50mm width.