JP2016203489A - Method for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical film having improved uneven peeling and suppressed haze.SOLUTION: A method for manufacturing an optical film includes a step of drawing a film in the film transfer direction using at least three drawing rolls. The film consists of a thermoplastic resin composition comprising a rubber-containing graft copolymer and an amorphous thermoplastic resin. In the film drawing step, the surface temperature of the most downstream side drawing roll among the drawing rolls is higher than that of any of drawing rolls located on the upstream side of the most downstream side drawing roll. In the film drawing step, the surface temperatures of the drawing rolls located on the upstream side of the most downstream side drawing roll are all in a range from T-5 to T+15 (°C), and the surface temperature of the most downstream side drawing roll is in a range from Tto T+25 (°C).SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an optical film.

  Plastic films used in devices that handle polarized light, such as liquid crystal display devices, are required to be optically transparent and optically uniform. Examples of such a plastic film include a polarizer protective film for protecting a polarizer, and an optical film represented by a film substrate for a liquid crystal display device. The optical film is required to have a small phase difference represented by the product of birefringence and thickness, and in particular, it is required that an image distortion phenomenon due to a so-called lens effect due to the unevenness of the film surface hardly occurs. . By using a film with uneven thickness, streak-like defects on the surface, and noticeable irregularities due to foreign matter as an optical film, color loss phenomenon such as partial thinning of the color, and surface quality degradation such as image distortion This is because problems arise.

Patent Document 1 discloses that a high-performance retardation film having excellent energy efficiency in the production process and little deterioration can be produced, and a temperature T (unit) that satisfies the following formula (A) in the stretched polymer film: A heat treatment step in which heat treatment is performed at ° C) is described. Formula (A): T _g <T <T _m0 [wherein T _g before heat treatment represents the glass transition temperature (unit: ° C.) of the polymer film, and T _m0 represents the melting point (unit; ° C). ]

  Patent Document 2 contains a specific amount of rubber-containing copolymer particles having a multilayer structure in which a refractive index and an average particle diameter are controlled as a dispersed phase (b) in a continuous phase (a) having a specific composition ratio. It is described that an optical film having excellent toughness and a small photoelastic coefficient that maintains transparency is provided by the optical film.

JP 2009-241396 A JP 2012-052023 A

  An object of this invention is to provide the manufacturing method of the optical film by which peeling nonuniformity was improved and haze was suppressed.

  The present inventor has found that by stretching under specific conditions, it is possible to produce an optical film in which peeling unevenness is improved and haze is suppressed, and the present invention has been achieved.

  That is, this invention has the process of extending | stretching a film in the conveyance direction of a film using at least 3 extending | stretching rolls, and the said film contains the rubber containing graft copolymer and an amorphous thermoplastic resin. In the step of stretching the film, comprising the resin composition, the surface temperature of the most downstream stretching roll among the stretching rolls is any surface of a plurality of stretching rolls upstream from the most downstream stretching roll. The present invention relates to a method for producing an optical film that is higher than a temperature.

In the step of stretching the film, the surface temperatures of the plurality of stretching rolls on the upstream side of the most downstream stretching roll are all in the range of T _g −5 (° C.) or more and T _g +15 (° C.) or less. It is preferable that the surface temperature of the most downstream drawing roll is in a range of T _g (° C.) or more and T _g +25 (° C.) or less.

  In the step of stretching the film, it is preferable that the stretching ratio in the transport direction of the film is 1.1 or more and 3.0 or less.

  The step of stretching the film preferably includes a step of stretching in the width direction.

  The amorphous thermoplastic resin is preferably an acrylic resin.

  The haze value of the optical film is preferably 1.0% or less.

  According to the present invention, it is possible to produce an optical film in which peeling unevenness is improved and haze is suppressed.

It is a figure which shows an example of a roll extending | stretching method. It is a figure which shows an example of a roll extending | stretching method. It is a figure which shows the evaluation method of peeling nonuniformity.

Stretching in order to control the phase difference or obtaining an optical film with improved transparency is considered, and a film made of a rubber-containing acrylic resin composition is stretched in the film transport direction using a roll. problem haze when stretched at a low temperature (near T _g) increases has occurred when. And although the haze value could be lowered by extending the temperature and stretching, peeling unevenness occurred.

  The method for producing an optical use film of the present invention will be described in detail below. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

(Molding)
There is no particular limitation on the method for forming a film comprising a thermoplastic resin composition containing a rubber-containing graft copolymer and an amorphous thermoplastic resin, and any conventionally known method can be used. For example, it is preferable to use the method described in JP-A-2002-221312.

  Examples thereof include a solution casting method and a melt extrusion method. Any of them can be adopted, but the melt extrusion method without using a solvent is preferable from the viewpoint of the global environment, the working environment, and the production cost.

  Before molding the optical film, it is preferable to go through a step of pre-drying the thermoplastic resin composition used as a raw material. This is because methanol remaining in the raw material that may cause foaming in the film is removed to further reduce foaming. The drying process is performed with a hot air dryer or the like, for example, by converting the raw material into a pellet form.

  When the raw material is a composition containing an acrylic resin, it is preferable that the methanol in the pellet is 500 ppm or less.

  As drying conditions in the drying step, in order to remove moisture in the resin in addition to removing methanol, the temperature is preferably 80 ° C. or higher and 120 ° C. or lower, and the drying time is preferably 5 hr or longer.

  When using the melt extrusion method, first, the thermoplastic resin composition is supplied to an extruder. The thermoplastic resin composition heated and melted in the extruder is supplied to the T die through a gear pump and a filter. The use of a gear pump is very useful because it improves the uniformity of the extrusion amount of the resin and reduces the thickness unevenness. The use of a filter is useful for removing a foreign substance in the thermoplastic resin composition and obtaining a film having an excellent appearance without defects.

  Next, the sheet-like molten resin extruded from the T-die is sandwiched between two cooling drums and cooled to form a film. One of the two cooling drums is preferably a rigid metal drum having a smooth surface, and the other is a flexible drum having an elastically deformable metal elastic outer cylinder having a smooth surface. A rigid drum and a flexible drum sandwich the sheet-like molten resin extruded from the T-die and cool it to form a film, thereby correcting surface irregularities and die lines, and smoothing the surface. This is because a film having a thickness unevenness of 5 μm or less can be obtained.

  The cooling drum is sometimes called a “touch roll” or a “cooling roll”, but the term “cooling drum” in this specification includes these rolls.

  The thickness of the film after molding may be 40 μm or more, more preferably 60 μm or more, and still more preferably 100 μm or more, because touch loss due to pinching may occur. Here, touch omission refers to a defect caused by the occurrence of a film portion that is not in contact with the surface of the cooling drum.

(Stretching)
As a method of stretching the film in the film transport direction, there is roll longitudinal stretching. The roll longitudinal stretching is a method in which the film is stretched in the traveling direction of the film while being heated to a predetermined temperature by a low peripheral speed roll and a high peripheral speed roll which are close to each other. In order to stably convey the film being stretched, it is preferable to stretch with a roll having a nip roll.

  The method of roll stretching is not particularly limited, but includes one-stage stretching in which stretching is performed with two rolls having different peripheral speeds and multi-stage stretching in which stretching is performed with three or more stretching rolls, and peeling unevenness and haze are controlled. Therefore, it is preferable to perform stretching by the latter multistage stretching.

  Of the two or more stretching rolls, at least the downstream speed of the stretching roll on the most downstream side can be stretched faster than the circumferential speed of the most upstream stretching roll.

  In addition, the roll longitudinal stretching is preferably performed in the transport direction of the film while heating the film to a predetermined temperature by a low circumferential speed roll and a high circumferential speed roll, which are at least a pair of rolls having different circumferential speeds. . The method is not particularly limited, and includes one-stage stretching in which stretching is performed with a pair of rolls having different peripheral speeds, multi-stage stretching in which stretching is performed with two or more sets of rolls, and the latter two or more sets of rolls. Stretching is preferably performed by multistage stretching.

  It is preferable that the surface temperature of the drawing roll on the most downstream side among the drawing rolls is higher than any surface temperature of a plurality of drawing rolls on the upstream side of the drawing roll on the most downstream side.

The glass transition temperature of the thermoplastic resin composition is defined as T _g (° C.). When the film made of the thermoplastic resin composition is stretched using at least three stretching rolls, the surface temperature of a plurality of stretching rolls upstream of the most downstream stretching roll among at least three stretching rolls. The lower limit is preferably T _g −5 (° C.) or more, and more preferably T _g (° C.) or more. In addition, the upper limit is preferably T _g +15 (° C.) or less, and more preferably T _g +10 (° C.) or less. If the surface temperature of the plurality of drawing rolls upstream from the most downstream drawing roll is less than T _g −5 (° C.), the film may be broken and may not be drawn, and T _g +15 (° C.) If it exceeds, peeling unevenness may occur.

When a film made of the thermoplastic resin composition is stretched using at least three stretching rolls, the lower limit of the surface temperature of the most downstream stretching roll among the stretching rolls is T _g (° C.) or more. It is preferable that T _g +10 (° C.) or more. Further, the upper limit is preferably T _g +25 (° C.) or less, and more preferably T _g +20 (° C.) or less. This is because if the surface temperature of the drawing roll on the most downstream side is lower than T _g (° C.), the haze value increases, and if it exceeds T _g +25 (° C.), uneven peeling appears.

The surface temperature of the plurality of stretching rolls upstream from the most downstream stretching roll is T _g −5 (° C.) or more and T _g +15 (° C.) or less, and the surface of the most downstream stretching roll The temperature is preferably T _g (° C.) or higher and T _g +25 (° C.) or lower. This is because a film having excellent transparency can be obtained when the surface temperatures of the plurality of stretching rolls on the upstream side of the most downstream stretching roll and the most downstream stretching roll all fall within the above range.

Here, the measurement method of the glass transition temperature The T _g is as follows. Using a differential scanning calorimeter (DSC) SSC-5200 manufactured by Seiko Instruments Inc., the sample was once heated to 200 ° C. at a rate of 25 ° C./minute, held for 10 minutes, and then at a rate of 25 ° C./minute to 50 ° C. Measurement is performed while the temperature is raised to 200 ° C. at a rate of temperature increase of 10 ° C./min through preliminary adjustment to lower the temperature, and an integral value is obtained from the obtained DSC curve (DDSC), and the glass transition temperature is determined from the maximum point. T _g can be determined.

  FIG. 1 and FIG. 2 show drawings for explaining three consecutive rolls when stretching is performed with three or more rolls, and they are close to the stretching roll 1, the stretching roll 2, and the stretching roll 3, respectively. The portions where the film 7 is sandwiched by the nip roll 4, the nip roll 5, and the nip roll 6 are referred to as a sandwiching portion 8, a sandwiching portion 9, and a sandwiching portion 10, respectively. As shown in FIG. 1, as a method of extending a film in the film conveyance direction, a method in which the film is in contact with a stretching roll between adjacent sandwiching portions and includes contact regions 11 to 14, and as shown in FIG. A method in which the film does not contact the stretching roll between the adjacent sandwiching portions and the contact regions 12 and 13 are not provided. It is preferable to use a method in which the film does not contact each roll between adjacent sandwiching portions as shown in the latter and does not include the contact regions 12 and 13. This is because if the contact area is small, the film is easily peeled off from the roll.

  In addition, a contact area means the area | region where a film contacts a extending | stretching roll except a clamping part.

  Peeling unevenness (peeling pattern) is a stripe in the film width direction that occurs when the film leaves the stretching roll in the step of stretching the film using a stretching roll or the like and occurs at regular intervals in the film longitudinal direction. In addition, it is different from stretching unevenness in which stretching is performed in a state where the film temperature is not uniform and the film thickness is not stable.

  The draw ratio in the film transport direction is defined by the peripheral speed ratio between the most upstream drawing roll and the most downstream drawing roll. That is, it is expressed by the following formula.

  Stretch ratio in the film transport direction = (peripheral speed of the most downstream stretching roll) / (peripheral speed of the most upstream stretching roll)

  The preferred draw ratio in the film transport direction depends on the stretching temperature, but is preferably selected in the range of 1.1 to 3.0, for example, and in the range of 1.3 to 2.7. More preferably, it is selected in the range of 1.6 or more and 2.4 or less. When the draw ratio is less than 1.1, the film is not substantially stretched in the stretching step, and thus the mechanical properties of the film cannot be sufficiently improved. Thereby, the stretched film is easily broken. When a draw ratio exceeds 3.0, the film before extending | stretching will become too thick, and will fracture | rupture at the time of unstretched film manufacture.

  In the process of extending | stretching a film, you may include both extending | stretching to the conveyance direction of a film, and extending | stretching to the width direction. It is preferable to further stretch the film stretched in the transport direction in the width direction of the film. This is because a film with better transparency having a haze value of 1.0% or less can be obtained, and an optical film with higher toughness strength can be obtained. The width direction refers to a direction orthogonal to the transport direction. Further, stretching in the width direction is also referred to as transverse stretching.

  Although it does not specifically limit as a method of extending | stretching in the width direction, The method of extending | stretching, etc., holding a film edge part in a tenter is mentioned.

  The stretching ratio in the width direction is preferably the same as the stretching ratio (longitudinal stretching) in the transport direction. If the draw ratio is different, uniform optical characteristics cannot be obtained.

  Here, the draw ratio in the width direction is represented by the ratio of the film width exiting the transverse stretching furnace to the film width entering the transverse stretching furnace.

The stretching temperature in the width direction when the film stretched in the transport direction is further stretched in the width direction of the film is preferably T _g −5 (° C.) or more and T _g +40 (° C.) or less. If the stretching temperature in the width direction is less than T _g -5 (° C), the film may break and may not be stretched. If it exceeds T _g +40 (° C), the thickness variation in the transport direction becomes severe, and it is used as an optical application. This is because it cannot be done. Here, the stretching temperature in the width direction is the temperature in the transverse stretching furnace.

(Take-up)
It is preferable to have a step of winding the film after stretching the film.

  The film winding speed is preferably 5 m / min to 50 m / min, more preferably 10 m / min to 45 m / min, and even more preferably 15 m / min to 40 m / min.

(A thermoplastic resin composition containing a rubber-containing graft copolymer and an amorphous thermoplastic resin)
Examples of the thermoplastic resin composition containing the rubber-containing copolymer and the amorphous thermoplastic resin include acrylic resin compositions.

  As the acrylic resin composition, an acrylic resin composition in which a rubber-containing graft copolymer is blended with an amorphous thermoplastic resin can be used for the purpose of improving mechanical strength. In this embodiment, the amorphous thermoplastic resin may be a resin component having a structural unit of unsaturated carboxylic acid ester and unsaturated carboxylic acid, or the rubber-containing graft copolymer may be unsaturated carboxylic acid ester and The resin component which has a structural unit of unsaturated carboxylic acid may be sufficient. Of course, both the rubber-containing graft copolymer and the amorphous thermoplastic resin may contain a resin component having constituent units of a saturated carboxylic acid alkyl ester and an unsaturated carboxylic acid.

  When the amorphous thermoplastic resin is a resin component having a structural unit of unsaturated carboxylic acid ester and unsaturated carboxylic acid, the rubber-containing graft copolymer is not particularly limited, but from the viewpoint of transparency, acrylic A rubber-like polymer can be preferably used.

(Rubber-containing graft copolymer)
The rubber-containing graft copolymer is obtained by polymerizing a monomer mixture composed of a vinyl monomer or the like in one or more stages in the presence of a rubber-like polymer. The rubber-containing graft copolymer is composed of a layer containing one or more rubbery polymers and one or more layers composed of different polymers, and one or more rubbery polymers inside. It is sometimes referred to as a multi-layered structure polymer having a structure including a so-called core-shell type. The multilayer structure polymer refers to the same polymer as the rubber-containing graft copolymer, and is included in the form of the rubber-containing graft copolymer of the present invention.

  The rubbery polymer may be a polymer having a glass transition temperature of less than 20 ° C., and examples thereof include a butadiene-based cross-linked polymer, a (meth) acrylic cross-linked polymer, and an organosiloxane cross-linked polymer. . Among these, a (meth) acrylic crosslinked polymer (acrylic rubbery polymer) is particularly preferable in terms of weather resistance (light resistance) and transparency of the film. Examples of the acrylic rubber-like polymer include ABS resin rubber and ASA resin rubber.

  As the rubber-containing graft copolymer, an acrylic graft copolymer including an acrylic ester rubber-like polymer shown below can be preferably used from the viewpoint of transparency and the like.

  The rubber-containing graft copolymer is obtained by polymerizing a monomer mixture containing an unsaturated carboxylic acid ester and an unsaturated carboxylic acid monomer in one or more stages in the presence of an acrylic ester rubbery polymer. Is preferred.

  The acrylic ester rubbery polymer is preferably a rubbery polymer based on an acrylic ester, specifically, 50 to 100% by weight of an acrylic ester and other vinyl monomers that can be copolymerized. 0.05 to 10 polyfunctional monomer having 2 or more non-conjugated reactive double bonds per molecule with respect to 100 parts by weight of the monomer or monomer mixture consisting of 50 to 0% by weight Those obtained by polymerizing parts by weight are preferred. The monomers may be mixed and polymerized all at once, or may be used in two or more stages by changing the monomer composition at each reaction stage.

  As the acrylate ester, an alkyl acrylate ester is preferable from the viewpoint of polymerizability and cost, and an alkyl group having 1 to 12 carbon atoms is more preferable. For example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, phenoxyethyl acrylate, phenyl acrylate, acrylic acid 2 -Ethylhexyl, n-octyl acrylate, glycidyl acrylate, and the like, and two or more of these monomers may be used in combination.

  Of the monomer mixture used for polymerization to obtain an acrylate ester rubbery polymer, the amount of acrylate ester is preferably 50% by weight to 100% by weight, preferably 60% by weight, based on 100% by weight of the monomer mixture. It is more preferably 99 wt% or less, more preferably 70 wt% or more and 99 wt% or less, and most preferably 80 wt% or more and 99 wt% or less. If it is less than 50% by weight, the impact resistance is lowered, the elongation at the time of tensile rupture is lowered, and cracks tend to be generated when the film is cut.

  As other vinyl monomers that can be copolymerized, methacrylic acid esters are particularly preferred from the viewpoint of weather resistance and transparency. Examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacrylic acid. Examples include 2-butyl acid, isobutyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, phenoxyethyl methacrylate, phenyl methacrylate, and glycidyl methacrylate. Aromatic vinyls and derivatives thereof, and vinyl cyanides are also preferable, and examples thereof include styrene, methylstyrene, acrylonitrile, methacrylonitrile and the like. Other examples include unsubstituted and / or substituted maleic anhydrides, (meth) acrylamides, vinyl esters, vinylidene halides, (meth) acrylic acid and salts thereof, and (hydroxyalkyl) acrylate esters.

  The polyfunctional monomer may be a commonly used one such as allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate, divinyl adipate, divinyl benzene, ethylene glycol dimethacrylate, Diethylene glycol methacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetromethylol methane tetramethacrylate, dipropylene glycol dimethacrylate and acrylates thereof can be used. Two or more of these polyfunctional monomers may be used.

  Among the monomer mixture used for the polymerization for obtaining an acrylic ester rubbery polymer, the amount of the polyfunctional monomer is 0.05 to 10 parts per 100 parts by weight of the total amount of the monomer mixture. Part by weight is preferable, and 0.1 to 5 parts by weight is more preferable. If the addition amount of the polyfunctional monomer is less than 0.05 parts by weight, there is a tendency that a crosslinked product cannot be formed, and even if it exceeds 10 parts by weight, the crack resistance of the film tends to be lowered.

  The average particle size of the rubber-like polymer (rubber-like particles up to the rubber-like polymer layer) of the rubber-containing graft copolymer is preferably 20 to 450 nm, more preferably 20 to 400 nm, still more preferably 30 to 150 nm, 40 Most preferred is ˜250 nm. If it is less than 20 nm, the crack resistance of the optical film may deteriorate. On the other hand, when it exceeds 450 nm, the transparency of an optical film may fall. In addition, an average particle diameter can be measured using the light scattering of a wavelength of 546 nm by the dynamic scattering method, for example, with a U-5100 type ratio beam spectrophotometer of Hitachi High-Technologies Corporation.

  The rubber-containing graft copolymer is an unsaturated carboxylic acid ester and an unsaturated carboxylic acid monomer in the presence of 5 to 90 parts by weight (more preferably, 5 to 75 parts by weight) of an acrylic ester rubbery polymer. What is obtained by polymerizing 95 to 25 parts by weight of a monomer mixture containing is at least one stage is preferable.

  From the viewpoint of the hardness and rigidity of the film, the graft copolymer composition (monomer mixture) preferably contains 50% by weight or more of methacrylic acid ester. As monomers used for graft copolymerization, the above-mentioned methacrylic acid esters, acrylic acid esters, and vinyl monomers copolymerizable with these can be used in the same manner, and methacrylic acid esters and acrylic acid esters are preferably used. Is done. When the amorphous thermoplastic resin is an acrylic resin, methyl methacrylate from the viewpoint of compatibility with the acrylic resin, methyl acrylate, ethyl acrylate, n-butyl acrylate from the point of suppressing zipper depolymerization Is preferred.

  As the unsaturated carboxylic acid ester, a (meth) acrylic acid ester is preferable, and the above examples can be used similarly. As the unsaturated carboxylic acid monomer, (meth) acrylic acid, (meth) acrylic acid salt, maleic acid, hydrolyzed maleic anhydride and the like can be used, but (meth) acrylic acid and its salts are preferred. . Examples of the salt of (meth) acrylic acid include sodium (meth) acrylate, calcium (meth) acrylate, magnesium (meth) acrylate, and ammonium (meth) acrylate. The amount of the unsaturated carboxylic acid monomer used is 100% by weight of the total amount of the monofunctional monomer (the total amount of the unsaturated carboxylic acid monomer and other monofunctional monomers copolymerizable therewith). 0.1-30 wt% is preferable, 0.1-20 wt% is more preferable, 0.1-15 wt% is further preferable, 0.1-10 wt% is further more preferable, 0.1-7 wt% % Is most preferred. The structure of the unsaturated carboxylic acid monomer is present in the polymer layer obtained by polymerizing the monomer mixture, so that the carboxyl group of the unsaturated carboxylic acid monomer and the (meth) acrylic acid are adjacent to each other. The ester group of the unsaturated carboxylic acid ester present is cyclized by dealkyl alcoholation during the molding process to take an acid anhydride structure. For example, if (meth) acrylic acid is next to methyl (meth) acrylate, a demethanol reaction occurs, resulting in an acid anhydride structure. As the other monofunctional monomer copolymerizable therewith, the above-mentioned methacrylic acid ester, acrylic acid ester, and other copolymerizable vinyl monomers can be used in the same manner.

  From the viewpoint of excellent optical isotropy, the monomer mixture includes a (meth) acrylic monomer having an alicyclic structure, a heterocyclic structure or an aromatic group (“ring structure-containing (meth)”. (Referred to as “acrylic monomer”). Specific examples include benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and phenoxyethyl (meth) acrylate. The amount used is from 1 to 99.1 in the total amount of the monomer mixture (the total amount of the ring structure-containing (meth) acrylic monomer and other monofunctional monomers copolymerizable therewith) of 100% by weight. % By weight is preferred, 5 to 70% by weight is more preferred, and 5 to 50% by weight is most preferred. As the other monofunctional monomer copolymerizable therewith, the above-mentioned methacrylic acid ester, acrylic acid ester, and other copolymerizable vinyl monomers can be used in the same manner.

  The graft ratio with respect to the acrylic ester rubbery polymer is preferably 10 to 250%, more preferably 40 to 230%, and most preferably 60 to 220%. If the graft ratio is less than 10%, the rubber-containing graft copolymer tends to aggregate in the molded product, which may cause a decrease in transparency or cause foreign matters. Moreover, there exists a tendency for the elongation at the time of a tensile fracture to fall and to become easy to generate | occur | produce a crack at the time of film cutting. If it is 250% or more, the melt viscosity at the time of molding, for example, at the time of film molding tends to be high, and the moldability of the film tends to decrease.

  The graft ratio is a weight ratio of the graft component in the rubber-containing graft copolymer, and is measured by the following method.

  2 g of the obtained rubber-containing graft copolymer was dissolved in 50 ml of methyl ethyl ketone, and centrifuged for 1 hour at a rotational speed of 30000 rpm and a temperature of 12 ° C. using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CP60E) to obtain an insoluble matter. And soluble components (set a total of three centrifuge operations). The obtained insoluble matter is calculated as a rubber-containing graft polymer by the following formula.

  Graft rate (%) = [{(weight of methyl ethyl ketone insoluble matter) − (weight of rubbery polymer)} / (weight of rubbery polymer)] × 100

The rubber-containing graft copolymer may further have a hard polymer layer or a rubber-like polymer (soft polymer) layer in addition to the polymer layer described above. The rubber-containing graft copolymer includes, for example, a structure having a hard polymer layer on the inner layer side of an acrylic ester rubber-like polymer, an innermost layer made of a hard polymer, and a rubber-like polymer (soft polymer). The structure which has at least 1 layer of the outer layer which consists of an inner layer which consists of a hard polymer further may be sufficient.
“The term“ hard ”as used herein means that the glass transition temperature of the polymer is 20 ° C. or higher. On the other hand, “soft” means that the glass transition temperature of the polymer is less than 20 ° C. From the viewpoint of enhancing the impact absorbing ability of the soft layer and enhancing the impact resistance improving effect such as crack resistance, the glass transition temperature of the polymer is preferably less than 0 ° C, more preferably less than -20 ° C. .

  The glass transition temperature of the polymer distinguishing between “soft” and “hard” is calculated using the Fox equation using the values described in the Polymer Handbook (Polymer Hand Book (J. Brandrup, Interscience 1989)). The calculated value is used (for example, polymethyl methacrylate is 105 ° C. and polybutyl acrylate is −54 ° C.).

  The rubber-containing graft copolymer can be produced by a general emulsion polymerization method. Specifically, a method of continuously polymerizing an acrylate monomer using an emulsifier in the presence of a water-soluble polymerization initiator can be exemplified.

  In the emulsion polymerization method, it is preferable to carry out continuous polymerization in a single reaction tank, and using two or more reaction tanks is not preferable because the mechanical stability of the latex decreases.

  The polymerization temperature is preferably 30 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 80 ° C. or lower. If the temperature is lower than 30 ° C., the productivity tends to decrease, and if the temperature exceeds 100 ° C., the quality tends to decrease due to the excessive increase in the target molecular weight. Raw materials such as acrylate monomers, initiators, emulsifiers and deionized water that are continuously added to the polymerization reactor are added accurately under the control of the metering pump, but the polymerization heat generated in the reactor In order to ensure the amount of heat removal, there is no problem even if it is cooled in advance if necessary. The latex discharged from the reaction vessel may be added with a polymerization inhibitor, a coagulant, a flame retardant, an antioxidant, and a pH adjuster as necessary. You can go. Thereafter, the copolymer can be obtained through known methods such as coagulation, heat treatment, dehydration, washing with water, and drying. Examples of the pH adjuster include sodium carbonate and boric acid.

  In emulsion polymerization, a usual polymerization initiator can be used. For example, inorganic peroxides such as potassium persulfate and sodium persulfate, organic peroxides such as cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide (BHPO), and azobisisobutyronitrile. Oil soluble initiators are also used. These may be used alone or in combination of two or more. These initiators are used as normal redox polymerization initiators in combination with reducing agents such as sodium sulfite, sodium thiosulfate, sodium formaldehyde, sulfoxylate, ascorbic acid, ferrous sulfate and disodium ethylenediaminetetraacetate complex. May be used.

  A chain transfer agent may be used in combination with the polymerization initiator. Examples of the chain transfer agent include C2-C20 alkyl mercaptan, mercapto acids, thiophenol, carbon tetrachloride and the like. Examples of the alkyl mercaptan having 2 to 20 carbon atoms include mercapto group-containing compounds such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and lauryl mercaptan. The chain transfer agents may be used alone or in combination of two or more.

  There is no particular limitation on the emulsifier used in the emulsion polymerization method, and any emulsifier for ordinary emulsion polymerization can be used. For example, sulfate ester surfactants such as sodium alkyl sulfate, sulfonate surfactants such as sodium alkylbenzene sulfonate, sodium alkyl sulfonate, sodium dioctyl sulfosuccinate, sodium alkyl phosphate, polyoxyethylene alkyl ether Anionic surfactants such as phosphate surfactants such as sodium phosphate, N-acyl sarcosinate surfactants such as sodium N-lauroyl sarcosinate, and fatty acid surfactants such as potassium oleate Is mentioned. The sodium salt may be other alkali metal salt such as potassium salt or ammonium salt. These emulsifiers may be used alone or in combination of two or more. Furthermore, nonionic surfactants represented by polyoxyalkylenes or alkyl-substituted or aryl-substituted terminal hydroxyl groups may be used or partially used together. Among these, from the viewpoint of polymerization reaction stability and particle system controllability, sulfonate surfactants or phosphate surfactants are preferable. Among them, dioctylsulfosuccinate or polyoxyethylene alkyl ether phosphate is preferable. Ester salts can be used more preferably.

  The use amount of the emulsifier is preferably 0.05 part by weight or more and 10 parts by weight or more preferably 0.1 part by weight or more and 1.0 part by weight or less with respect to 100 parts by weight of the whole monomer component. If the amount is less than 0.05 parts by weight, the copolymer particle system tends to be too large. If the amount is more than 10 parts by weight, the copolymer particle system tends to be too small, and the particle size distribution tends to deteriorate. .

  The blending amount of the rubber-containing graft copolymer is such that the rubber-containing graft copolymer is an acrylic rubbery polymer in 100 parts by weight of the thermoplastic resin composition containing the rubber-containing graft copolymer and the amorphous thermoplastic resin. It is preferable that 1 to 60 parts by weight (rubber-like particles up to the rubbery polymer layer) is contained, more preferably 1 to 30 parts by weight, and still more preferably 1 to 25 parts by weight. If it is less than 1 part by weight, the crack resistance and vacuum formability of the film may deteriorate, the photoelastic constant may increase, and optical isotropy may deteriorate. On the other hand, when it exceeds 60 parts by weight, the heat resistance, surface hardness, transparency, and bending whitening resistance of the film tend to deteriorate.

(Amorphous thermoplastic resin)
Examples of amorphous thermoplastic resins include acrylic resins, polycarbonate resins, polystyrene resins, cycloolefin resins, cellulose resins, vinyl chloride resins, polysulfone resins, polyethersulfone resins, maleimides. -Single resin, such as olefin resin and glutarimide resin, or a resin composition obtained by mixing these.

  When the rubber-containing graft copolymer having the structural units of unsaturated carboxylic acid ester and unsaturated carboxylic acid as described above is used, an acrylic resin is preferable as the amorphous thermoplastic resin. Moreover, it is preferable that acrylic resin contains the resin component which has a structural unit of unsaturated carboxylic acid ester and unsaturated carboxylic acid. For example, a methacrylic resin having methyl methacrylate as a monomer component can be used, and those containing 30 to 100% by weight of methyl methacrylate are preferable.

  Examples of the resin component having a constituent unit of unsaturated carboxylic acid ester and unsaturated carboxylic acid include, for example, an acrylic resin having a glutaric anhydride unit that has undergone an intramolecular cyclization reaction or a partial intramolecular cyclization reaction, And glutarimide acrylic resin.

  Although it does not specifically limit as unsaturated carboxylic acid ester, For example, the C1-C10 (meth) acrylic acid ester of an alkyl residue is preferable. Specifically, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, glycidyl methacrylate, epoxy cyclohexyl methyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methacryl Methacrylic acid esters such as dicyclopentanyl acid, 2,2,2-trifluoroethyl methacrylate, 2,2,2-trichloroethyl methacrylate, isobornyl methacrylate; methyl acrylate, ethyl acrylate, butyl acrylate, acrylic Acrylic esters such as 2-ethylhexyl acrylate, glycidyl acrylate, epoxycyclohexylmethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc. And the like. These monomers can be used alone or in combination of two or more.

  The unsaturated carboxylic acid is not particularly limited as long as it is an unsaturated carboxylic acid copolymerizable with an unsaturated carboxylic acid ester, and examples thereof include hydrolysates of (meth) acrylic acid, maleic acid, and maleic anhydride. These salts can also be used, and examples thereof include (meth) acrylic acid salts such as sodium (meth) acrylate, calcium (meth) acrylate, magnesium (meth) acrylate, and ammonium (meth) acrylate. . (Meth) acrylic acid is preferred from the viewpoint of excellent thermal stability.

  The resin component which has a structural unit of unsaturated carboxylic acid ester and unsaturated carboxylic acid may have structural units other than unsaturated carboxylic acid ester and unsaturated carboxylic acid. Such a structural unit is not particularly limited, but examples thereof include vinylcyans such as acrylonitrile and methacrylonitrile; vinylarenes such as styrene, α-methylstyrene, monochlorostyrene and dichlorostyrene; esters of maleic acid and fumaric acid Etc .; vinyl halides such as vinyl chloride, vinyl bromide, chloroprene; vinyl acetate; alkenes such as ethylene, propylene, butylene, butadiene, isobutylene: halogenated alkenes; allyl methacrylate, diallyl phthalate, triallyl cyanurate, Examples thereof include polyfunctional monomers such as monoethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and divinylbenzene. These monomers can be used alone or in combination of two or more.

  As a suitable example of the resin component having a structural unit of unsaturated carboxylic acid ester, an acrylic resin obtained by polymerizing 30 to 100% by weight of methyl methacrylate and 70 to 0% by weight of a monomer copolymerizable therewith is used. Can be mentioned. In this acrylic resin, methyl methacrylate is preferably contained in an amount of 30 to 100% by weight, more preferably 50 to 99.9% by weight, still more preferably 50 to 98% by weight, and a monomer copolymerizable with methyl methacrylate. Is preferably 70 to 0% by weight, more preferably 50 to 0.1% by weight, still more preferably 50 to 2% by weight. If the content of methyl methacrylate is less than 30% by weight, the optical characteristics, appearance, weather resistance, and heat resistance unique to acrylic resins tend to be lowered. Moreover, it is desirable not to use a polyfunctional monomer from the viewpoint of processability and appearance.

  Further, as the amorphous thermoplastic resin, a heat-resistant acrylic resin can be used. For example, an acrylic resin in which an N-substituted maleimide compound is copolymerized as a copolymerization component, an anhydrous glutaric acid acrylic resin, an anhydrous Maleic acid acrylic resins, acrylic resins having a lactone ring structure, glutarimide acrylic resins, acrylic resins containing hydroxyl and / or carboxyl groups, aromatic vinyl monomers and other monomers copolymerizable therewith Aromatic vinyl-containing polymers obtained by polymerizing monomers or hydrogenated aromatic vinyl-containing polymers obtained by partially or fully hydrogenating the aromatic ring (for example, styrene monomer and copolymerized therewith) Partially Hydrogenated Styrene Polymerization Obtained by Partial Hydrogenation of the Aromatic Ring of a Styrene Polymer Obtained by Polymerizing Other Possible Monomers ), And the like acrylic polymer having a cyclic acid anhydride repeating units. From the viewpoints of heat resistance and optical properties, a glutarimide acrylic resin can be more preferably used. These can be used alone or in combination of two or more.

  Although it does not restrict | limit especially as a glutaric anhydride acrylic resin which is a glutaric anhydride resin, It can manufacture according to the method of Unexamined-Japanese-Patent No. 2007-254703, etc. The resin having a lactone ring structure can be produced according to the method described in JP-A-2008-9378. Moreover, the manufacturing method in particular of the said glutarimide acrylic resin is although it does not restrict | limit, For example, the method etc. which are described in Unexamined-Japanese-Patent No. 2008-273140 are mentioned.

  About the manufacturing method of glutarimide acrylic resin, specifically, the 1st stage reaction which processes acrylic resin and an imidizing agent with a 1st extruder is performed, and the reaction in a 1st extruder with a 2nd extruder An example of the reaction is a second-stage reaction in which the product is further treated with an esterifying agent.

  A tandem type extruder having a first extruder, a second extruder, and a component connecting a resin discharge port of the first extruder and a raw material supply port of the second extruder can be used.

  It does not specifically limit as said imidating agent, For example, ammonia or a primary amine can be used. Examples of the primary amine include aliphatic hydrocarbon group-containing primary amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, and n-hexylamine; Examples include aromatic hydrocarbon group-containing primary amines such as aniline, benzylamine, toluidine, and trichloroaniline, and alicyclic hydrocarbon group-containing primary amines such as cyclohexylamine.

  As the imidizing agent, urea compounds that generate ammonia or primary amines by heating, such as urea, 1,3-dimethylurea, 1,3-diethylurea, 1,3-dipropylurea, can also be used.

  Among the imidizing agents, ammonia, methylamine, and cyclohexylamine are preferably used, and methylamine is particularly preferably used from the viewpoints of cost and physical properties.

  In this imidization step, a ring closure accelerator may be added as necessary in addition to the imidizing agent.

  The addition amount of the imidizing agent is not particularly limited, and may be adjusted according to the content of the glutarimide unit in the obtained glutarimide acrylic resin.

  The ring-opening accelerator is not particularly limited as long as the ester group or carboxyl group remaining in the glutarimide acrylic resin can be converted to glutaric anhydride. For example, potassium hydroxide, sodium hydroxide, lithium hydroxide, water Inorganic base compounds such as calcium oxide and magnesium hydroxide, amines such as triethylamine, trimethylamine, diethylamine and dimethylamine, imines such as 2-phenylmethylimidazole and guanidine, trimethylphenylammonium hydroxide, trimethylbenzylammonium hydroxide, water Alkali metal derivatives such as quaternary ammonium salts such as tetramethylammonium oxide, p-toluenesulfonium base, sodium methylate, sodium ethylate, potassium methylate, potassium ethylate Kokishido and the like.

  Next, a suitable example of a glutarimide acrylic resin that can be used in the present invention will be described. A suitable glutarimide acrylic resin preferably has a glass transition temperature of 120 ° C. or higher and includes a unit represented by the following general formula (1) and a unit represented by the following general formula (2).

In the general formula (1), R ¹ and R ² are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ is hydrogen, an alkyl group having 1 to 18 carbon atoms, or a carbon number. It is a C3-C15 cycloalkyl group or a C5-C15 substituent containing an aromatic ring. Hereinafter, the unit represented by the general formula (1) is also referred to as “glutarimide unit”.

In the general formula (1), preferably, R ¹ and R ² are each independently hydrogen or a methyl group, and R ³ is hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and more preferably, R ¹ is a methyl group, R ² is hydrogen, and R ³ is a methyl group.

The glutarimide acrylic resin may contain only a single type as a glutarimide unit, or a plurality of different ones or all of R ¹ , R ² , and R ^{3 in} the general formula (1). The type may be included.

  The glutarimide unit can be formed by imidizing a (meth) acrylic acid ester unit represented by the following general formula (2). Further, an acid anhydride such as maleic anhydride, a half ester of the acid anhydride and a linear or branched alcohol having 1 to 20 carbon atoms, or an α, β-ethylenically unsaturated carboxylic acid (for example, acrylic acid) The glutarimide unit can also be formed by imidizing methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, citraconic acid).

In the glutarimide acrylic resin, the content of the glutarimide unit is not particularly limited, and can be appropriately determined in consideration of, for example, the structure of R ³ . However, the content of the glutarimide unit is preferably 1.0% by weight or more, more preferably 3.0% by weight to 90% by weight, and more preferably 5.0% by weight to 60% by weight in the total amount of the glutarimide acrylic resin. Further preferred. When the content of the glutarimide unit is less than the above range, the resulting glutarimide acrylic resin tends to have insufficient heat resistance or its transparency may be impaired. On the other hand, if it exceeds the above range, the heat resistance and melt viscosity will be unnecessarily high, the molding processability will be poor, the mechanical strength during film processing will be extremely low, and the transparency will be impaired. Tend.

  The content of the glutarimide unit is calculated by the following method.

^{Using 1} H-NMR BRUKER Avance III (400 MHz), ¹ H-NMR measurement of the resin is performed to determine the content (mol%) of each monomer unit such as glutarimide unit or ester unit in the resin, and the content The amount (mol%) is converted to the content (% by weight) using the molecular weight of each monomer unit.

For example, in the case of a resin comprising a glutarimide unit in which R ³ is a methyl group in the above general formula (1) and a methyl methacrylate unit, it is derived from the O-CH ₃ proton of methyl methacrylate appearing in the vicinity of 3.5 to 3.8 ppm. From the peak area a and the peak area b derived from the N—CH ₃ proton of glutarimide that appears in the vicinity of 3.0 to 3.3 ppm, the content (% by weight) of the glutarimide unit is obtained by the following formula. Can do.
[Methyl methacrylate unit content A (mol%)] = 100 × a / (a + b)
[Content B (glut%) of glutarimide unit] = 100 × b / (a + b)
[Content of glutarimide unit (% by weight)] = 100 × (B × (molecular weight of glutarimide unit)) / (A × (molecular weight of methyl methacrylate unit) + B × (molecular weight of glutarimide unit))

  In addition, also when a unit other than the above is included as a monomer unit, content (weight%) of a glutarimide unit can be calculated | required similarly from content (mol%) and molecular weight of each monomer unit in resin.

In the general formula (2), R ⁴ and R ⁵ are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁶ is an alkyl group having 1 to 18 carbon atoms or 3 to 3 carbon atoms. 12 cycloalkyl groups or substituents having 5 to 15 carbon atoms including an aromatic ring. Hereinafter, the unit represented by the general formula (2) is also referred to as “(meth) acrylic acid ester unit”. In the present application, “(meth) acryl” refers to “methacryl or acrylic”.

In the general formula (2), preferably, R ⁴ and R ⁵ are each independently hydrogen or a methyl group, R ⁶ is hydrogen or a methyl group, and more preferably R ⁴ is hydrogen, ⁵ is a methyl group, and R ⁶ is a methyl group.

The glutarimide acrylic resin may contain only a single type as a (meth) acrylic acid ester unit, or any or all of R ⁴ , R ⁵ and R ⁶ in the above general formula (2) A plurality of different types may be included.

  The glutarimide acrylic resin may further contain a unit represented by the following general formula (3) (hereinafter also referred to as “aromatic vinyl unit”) as necessary.

In the general formula (3), R ⁷ is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁸ is an aryl group having 6 to 10 carbon atoms.

  Although it does not specifically limit as an aromatic vinyl unit represented by the said General formula (3), A styrene unit and (alpha) -methylstyrene unit are mentioned, A styrene unit is preferable.

The glutarimide acrylic resin may contain only a single type as an aromatic vinyl unit, or may contain a plurality of units in which either or both of R ⁷ and R ⁸ are different.

  In the glutarimide acrylic resin, the content of the aromatic vinyl unit is not particularly limited, but is preferably 0 to 50% by weight, more preferably 0 to 20% by weight, and more preferably 0 to 15% by weight of the total amount of the glutarimide acrylic resin. Is particularly preferred. When the content of the aromatic vinyl unit is larger than the above range, sufficient heat resistance of the glutarimide acrylic resin cannot be obtained.

  However, in the present invention, it is preferable that the glutarimide acrylic resin does not contain an aromatic vinyl unit from the viewpoints of improvement of bending resistance and transparency, reduction of fish eyes, and improvement of solvent resistance or weather resistance.

  The glutarimide acrylic resin may further contain other units other than the glutarimide unit, the (meth) acrylic acid ester unit, and the aromatic vinyl unit, if necessary.

  Examples of other units include amide units such as acrylamide and methacrylamide, glutaric anhydride units, nitrile units such as acrylonitrile and methacrylonitrile, maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. And maleimide-based units.

  These other units may be contained in the glutarimide acrylic resin by random copolymerization or may be contained by graft copolymerization.

  These other units may be those introduced by copolymerizing the monomer constituting the unit with a resin that is a raw material for producing a glutarimide acrylic resin. Further, when the imidization reaction is performed, these other units may be by-produced and included in the glutarimide acrylic resin.

Although the weight average molecular weight of glutarimide acrylic resin is not specifically limited, It is preferable to exist in the range of 1 * 10 < ⁴ > -5 * 10 < ⁵ >. If it is in the said range, moldability will not fall or the mechanical strength at the time of film processing will not be insufficient. On the other hand, when the weight average molecular weight is smaller than the above range, the mechanical strength when formed into a film tends to be insufficient. Moreover, when larger than the said range, the viscosity at the time of melt-extrusion is high, there exists a tendency for the moldability to fall and the productivity of a molded article to fall.

  The glass transition temperature of the glutarimide acrylic resin is preferably 115 ° C. or higher, and more preferably 120 ° C. or higher in that the film can exhibit good heat resistance. More preferably, it is 125 degreeC or more.

  The haze value of the optical film according to the present disclosure is preferably 1.0% or less, more preferably 0.7% or less, and further preferably 0.5% or less. When the haze value is 1.0% or less, it is suitable for optical applications.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this. In the following description, “parts” represents “parts by weight” unless otherwise specified. In addition, the measuring method of each physical property as described in a following manufacture example, an Example, and a comparative example is as follows.

(Resin temperature)
The temperature of the molten resin in the production of the thermoplastic resin composition pellets was measured with a non-contact radiation thermometer (TMC50, manufactured by Japan Sensor Co., Ltd.) for the molten resin at the die discharge port. Similarly, the temperature of the molten resin in film production was measured with a non-contact radiation thermometer (TMC50, manufactured by Japan Sensor Co., Ltd.).

(Glass-transition temperature)
Using a differential scanning calorimeter (DSC) SSC-5200 manufactured by Seiko Instruments Inc., the sample was once heated to 200 ° C. at a rate of 25 ° C./minute, held for 10 minutes, and then at a rate of 25 ° C./minute to 50 ° C. Measurement is performed while the temperature is raised to 200 ° C. at a rate of temperature increase of 10 ° C./min through preliminary adjustment to lower the temperature, and an integral value is obtained from the obtained DSC curve (DDSC), and the glass transition temperature is determined from the maximum point. Asked.
(Polymerization conversion)
The polymerization conversion rate of the polymer obtained in the polymerization was determined by the following method.
Approximately 2 g of a sample (polymer latex) containing a polymer was collected from the polymerization system and precisely weighed, and then dried in a hot air dryer at 120 ° C. for 1 hour, and the weight after drying was precisely weighed as the solid content. . Next, the ratio of the precision weighing result before and after drying was determined as the solid content ratio in the sample. Finally, using this solid content ratio, the polymerization conversion rate was calculated by the following formula. In this calculation formula, the polyfunctional monomer and the chain transfer agent were handled as charged monomers.
Polymerization conversion rate (%) = {(total weight of charged raw materials × solid content ratio—total weight of raw materials other than water and monomers) / weight of charged monomers} × 100
(Average particle diameter of rubbery polymer)
The average particle size of the rubbery polymer was measured in the latex state. The measurement was performed using light scattering at a wavelength of 546 nm using a U-5100 ratio beam spectrophotometer manufactured by Hitachi High-Technologies Corporation.
(Average particle size of rubber-containing graft copolymer)
The average particle size of the rubber-containing graft copolymer was measured in the latex state, and was determined in the same manner as the average particle size of the rubber-like polymer.

(Roll surface temperature)
The roll surface temperature was measured using a non-contact radiation thermometer (TMC50, manufactured by Japan Sensor Co., Ltd.).

(Stretching temperature in the width direction)
The stretching temperature in the width direction was measured with a thermocouple installed in the furnace.

(Evaluation of peeling unevenness)
As shown in FIG. 3, a xenon lamp 31 (150 W xenon lamp C2577 manufactured by Hamamatsu Photonics Co., Ltd.) is used as a point light source, and the optical film 32 cut into an A4 size (210 mm × 297 mm) is separated from a position 400 mm away. Light was irradiated at an angle of 90 degrees, and the transmitted light was projected onto a screen 33 arranged parallel to the optical film at a position 300 mm away from the optical film. The film and screen were tilted at an angle of 30 ° or more to observe the peeling pattern, and peeling unevenness was evaluated.

  When there was no occurrence of peeling unevenness, it was marked as ◯, when peeling unevenness occurred on the entire surface in the film width direction, x, and when peeling unevenness partially occurred in the film width direction.

(Evaluation of haze)
Evaluation of haze was performed by measuring a haze value using the haze meter (MDH2000, Nippon Denshoku) about the center part of the width direction of a film.

(Production Example 1)
<Manufacture of amorphous thermoplastic resin>
A glutarimide acrylic resin (A1) was produced as an amorphous thermoplastic resin using polymethyl methacrylate as a raw material resin and monomethylamine as an imidizing agent.

  In this production, a tandem reaction extruder in which two extrusion reactors were arranged in series was used. As for the tandem type reactive extruder, the meshing type co-directional twin-screw extruder having a diameter of 75 mm for both the first and second extruders and L / D (ratio of the length L to the diameter D of the extruder) of 74. The raw material resin was supplied to the raw material supply port of the first extruder using a constant weight feeder (manufactured by Kubota Corporation).

  The degree of vacuum of each vent in the first extruder and the second extruder was set to -0.095 MPa. Furthermore, the pressure control mechanism in the part connects the first extruder and the second extruder with a pipe having a diameter of 38 mm and a length of 2 m, and connects the resin discharge port of the first extruder and the raw material supply port of the second extruder. Used a constant flow pressure valve.

  The resin (strand) discharged from the second extruder was cooled by a cooling conveyor and then cut by a pelletizer to form pellets. Here, in order to determine the pressure in the component connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder, or to determine the extrusion fluctuation, the discharge port of the first extruder, the first extruder and the first extruder Resin pressure gauges were provided at the center of the connecting parts between the two extruders and at the discharge port of the second extruder.

  In the 1st extruder, the polymethyl methacrylate resin (Mw: 105,000) was used as raw material resin, and the imide resin intermediate body 1 was manufactured using monomethylamine as an imidation agent. At this time, the temperature of the highest temperature part of the extruder is 280 ° C., the screw rotation speed is 55 rpm, the raw material resin supply amount is 150 kg / hour, and the addition amount of monomethylamine is 2.0 parts by weight with respect to 100 parts by weight of the raw material resin. did. The constant flow pressure valve was installed immediately before the raw material supply port of the second extruder, and the monomethylamine press-fitting portion pressure of the first extruder was adjusted to 8 MPa.

  In the second extruder, the imidizing agent and by-products remaining in the rear vent and the vacuum vent were devolatilized, and then dimethyl carbonate was added as an esterifying agent to produce an imide resin intermediate 2. At this time, each barrel temperature of the extruder was 260 ° C., the screw rotation speed was 55 rpm, and the addition amount of dimethyl carbonate was 3.2 parts by weight with respect to 100 parts by weight of the raw material resin. Furthermore, after removing the esterifying agent with a vent, it was extruded from a strand die, cooled in a water tank, and then pelletized with a pelletizer to obtain a glutarimide acrylic resin (A1).

  The obtained glutarimide acrylic resin (A1) is an acrylic resin obtained by copolymerizing a glutamylimide unit and a (meth) acrylic acid ester unit.

(Production Example 2)
<Production of rubber-containing graft copolymer>
(A) Polymerization of crosslinked methacrylic polymer (innermost layer) A mixture of the following composition was charged into a glass reactor, heated to 80 ° C. with stirring in a nitrogen stream, and then 25 parts by weight of methyl methacrylate, methacrylic 25% of the mixed solution of the innermost monomer component consisting of 0.1 parts by weight of allyl acid and 0.1 parts by weight of t-dodecyl mercaptan and 0.1 parts by weight of t-butyl hydroperoxide (BHPO) The polymerization was carried out for 45 minutes.

Mixture: (parts by weight)
Ion exchange water 220
Boric acid 0.3
Sodium carbonate 0.03
Sodium N-lauroyl sarcosinate 0.09
Sodium formaldehyde sulfoxylate 0.09
Ethylenediaminetetraacetic acid disodium 0.006
Ferrous sulfate heptahydrate 0.002

  Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the polymerization was completed by maintaining at the same temperature for 2 hours. During this period, 0.2 part by weight of sodium N-lauroyl sarcosinate was added. The average particle diameter of the polymer particles in the obtained innermost cross-linked methacrylic polymer latex was 1600 mm (determined using light scattering at a wavelength of 546 nm), and the polymerization conversion rate was 98%.

(B) Polymerization of rubber-like polymer The crosslinked methacrylic polymer latex obtained in (a) above was kept at 80 ° C. in a nitrogen stream, and after adding 0.1 part by weight of potassium persulfate, n-butyl acrylate A monomer mixture consisting of 41 parts by weight, 9 parts by weight of styrene and 1 part by weight of allyl methacrylate was continuously added over 5 hours. During this time, 0.1 part by weight of potassium oleate was added in three portions. After completing the addition of the monomer mixture, 0.05 part by weight of potassium persulfate was further added and held for 2 hours in order to complete the polymerization. The rubbery polymer obtained had an average particle size of 2300 mm and a polymerization conversion rate of 99%.

(C) Polymerization of outermost layer The rubber-like polymer latex obtained by (b) was kept at 80 ° C., 0.02 part by weight of potassium persulfate was added, 24 parts by weight of methyl methacrylate, and n-butyl acrylate A monomer mixture of 1 part by weight and 0.1 part by weight of t-dodecyl mercaptan was continuously added over 1 hour. The rubber-containing graft copolymer aqueous latex was obtained by holding for 1 hour after the addition of the monomer mixture was completed. The average particle size of the rubber-containing graft copolymer in the latex was 2530 mm, and the polymerization conversion rate was 99%. The resulting rubber-containing graft copolymer latex was subjected to salting out coagulation, heat treatment and drying by a known method to obtain a rubber-containing graft copolymer.

(Production Example 3)
<Manufacture of a thermoplastic resin composition pellet (C1)>
A mixture of 95 parts by weight of the glutarimide acrylic resin (A1) obtained in Production Example 1 and 5 parts by weight of the rubber-containing graft copolymer obtained in Production Example 2 was mixed with a 58 mmφ vented twin screw extruder (Toshiba Machine ( Supplied). Melting and kneading were performed by setting the number of revolutions of the extruder screw to 210 rpm, the discharge amount to 180 kg / hr, and the head temperature of the extruder to 250 ° C. The resin that came out as a strand from the die via the gear pump was cooled in a water tank to obtain a thermoplastic resin composition (C1) pelletized by a pelletizer. The temperature of the molten resin at the die discharge port was 260 ° C. The obtained thermoplastic resin composition pellet (C1) had a glass transition temperature of 122 ° C.
(Production Example 4)
<Production of thermoplastic resin composition pellet (C2)>
In Production Example 3, a mixture of 90 parts by weight of the glutarimide acrylic resin (A1) obtained in Production Example 1 and 10 parts by weight of the rubber-containing graft copolymer obtained in Production Example 2 was used. Obtained a pelletized thermoplastic resin composition (C2) in the same manner as in Production Example 3. The obtained thermoplastic resin composition pellet (C2) had a glass transition temperature of 122 ° C.

Example 1
The thermoplastic resin composition pellets (C1) obtained in Production Example 3 were dried at 90 ° C. for 4 hours with a dryer, and then supplied to a φ65 mm single screw extruder. The resin was heated and melted so that the resin temperature became 270 ° C. at the exit of the extruder, and the molten resin was extruded to a T die through a gear pump. This was cooled and solidified to obtain a film.

About the obtained film, it extended | stretched in the conveyance direction of the film. It extended | stretched using the 1st-3rd extending | stretching roll and nip roll. The first stretching roll is the most upstream stretching roll, and the third stretching roll is the most downstream stretching roll. As the positional relationship of the rolls, a method was used in which the film does not contact each roll between adjacent clamping portions as shown in FIG. The film width was 1000 mm. The radii R1, R2, and R3 of the first, second, and third drawing rolls were 100 mm, respectively. In addition, nip rolls having a smaller radius than the stretching rolls are arranged so that the film transport path is parallel to the plane including the rotation axis of all stretching rolls, and each of the stretching rolls and the nip rolls adjacent to the stretching rolls respectively. By sandwiching the film, the film was transported and stretched in the transport direction (longitudinal stretching). Each stretching roll was the film transport direction and was rotated in the same direction. Further, the sandwiching portion interval L was set to 250 mm. Moreover, roll surface temperature of the first draw roll and a second draw _roll, T g +8 _(℃), roll surface temperature of the third stretching roll _was set to T g +13 (℃). The peripheral speed of the third stretching roll was 1.8 times the peripheral speed of the first stretching roll.

After the film was stretched in the transport direction (longitudinal stretching), the film was continuously stretched in the width direction (transverse stretching) using a clip-type tenter lateral stretching machine. The stretching temperature in the width direction was T _g +13 (° C.), and the stretching ratio was the same as the stretching ratio in the transport direction (1.8 times).

  After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

(Example 2)
Using the thermoplastic resin composition pellets (C2) obtained in Production Example 4, the roll surface temperature of the first stretching roll and the second stretching roll is T _g +9 (° C.), and the roll surface temperature of the third stretching roll is T _A stretched film was obtained in the same manner as in Example 1 except that _g + 14 (° C.) and the peripheral speed of the third stretching roll was twice that of the first stretching roll. After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

Example 3
The roll surface temperature of the first stretching roll and the second stretching roll is T _g −5 (° C.), the roll surface temperature of the third stretching roll is T _g (° C.), and the peripheral speed of the stretching roll is the same as in Example 2. A stretched film was obtained in the same manner as in Example 1 except that. After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

Example 4
The roll surface temperature of the first stretching roll and the second stretching roll is T _g +15 (° C.), the roll surface temperature of the third stretching roll is T _g +25 (° C.), and the peripheral speed of the stretching roll is the same as in Example 2. A stretched film was obtained in the same manner as in Example 1 except that. After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

(Comparative Example 1)
Using the thermoplastic resin composition pellet (C2) obtained in Production Example 4, the roll surface temperatures of the first stretching roll, the second stretching roll, and the third stretching roll are all set to T _g -5 (° C), and the stretching is performed. A stretched film was obtained in the same manner as in Example 1 except that the peripheral speed of the roll was the same as that in Example 2. After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

(Comparative Example 2)
Example 1 except that the roll surface temperatures of the first drawing roll, the second drawing roll, and the third drawing roll were all set to T _g +30 (° C.), and the peripheral speed of the drawing roll was the same as in Example 2. Similarly, a stretched film was obtained. After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

(Comparative Example 3)
The roll surface temperature of the first stretching roll and the second stretching roll is T _g +15 (° C.), the roll surface temperature of the third stretching roll is T _g +5 (° C.), and the peripheral speed of the stretching roll is the same as in Example 2. A stretched film was obtained in the same manner as in Example 1 except that. After stretching in the transport direction (longitudinal stretching) and after stretching in the width direction (lateral stretching), haze and peeling unevenness were evaluated. The results are shown in Table 1.

From Table 1, the evaluation results in Examples 1 to 4 and Comparative Examples 1 to 4 were verified. First, when the surface temperatures of the first to third drawing rolls were equal, the haze value was high at T _g -5 (° C.) (Comparative Example 1), and the peeling unevenness was noticeably generated at T _g +30 (Comparative Example 2). Further, when the surface temperature of the third drawing roll was lower than the first and second drawing roll surface temperatures, peeling unevenness occurred (Comparative Example 3). Furthermore, the haze value became 1.0% or less in Examples 1 to 4 by stretching in the width direction under the same conditions (same stretching ratio), that is, by lateral stretching. On the other hand, Comparative Examples 1 and 2 showed that the haze value after longitudinal stretching exceeded 3.0%, and the haze value after stretching in the width direction was 1.0% or more. On the other hand, although the comparative example 3 had a low haze value, it resulted in the peeling nonuniformity remaining in the film. From the above, it was found that when the third stretching roll temperature was higher than the first and second stretching roll temperatures, there was no occurrence of peeling unevenness, the haze value was low, and a particularly excellent optical film was obtained.

Claims (6)

Having a step of stretching the film in the film transport direction using at least three stretching rolls;
The film comprises a thermoplastic resin composition comprising a rubber-containing graft copolymer and an amorphous thermoplastic resin;
In the step of stretching the film, the surface temperature of the most downstream stretching roll among the stretching rolls is higher than any of the surface temperatures of a plurality of stretching rolls upstream from the most downstream stretching roll. A method for producing a film. In the step of stretching the film, the surface temperatures of the plurality of stretching rolls on the upstream side of the most downstream stretching roll are all in the range of T _g −5 (° C.) or more and T _g +15 (° C.) or less.
2. The method for producing an optical film according to claim 1, wherein a surface temperature of the most downstream drawing roll is in a range of T _g (° C.) or more and T _g +25 (° C.) or less.   The method for producing an optical film according to claim 1 or 2, wherein in the step of stretching the film, a stretching ratio in the transport direction of the film is 1.1 or more and 3.0 or less.   The manufacturing method of the optical film of any one of Claims 1-3 including the process of extending | stretching in the width direction in the process of extending | stretching the said film.   The method for producing an optical film according to claim 1, wherein the amorphous thermoplastic resin is an acrylic resin.   The manufacturing method of the optical film of any one of Claims 1-5 whose haze value of the said optical film is 1.0% or less.

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