JP6549884B2 - Optical film manufacturing method and optical film - Google Patents

Description

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

  Optical transparency and optical homogeneity are required for an optical film represented by a polarizer protective film for protecting a polarizer, a film substrate for liquid crystal display and the like. In particular, the polarizer protective film is required to have a thinner film thickness for the purpose of improving the brightness, and a production method of biaxially stretching a melt-extruded film is known as a production of such a thin film polarizer protective film. (Patent document 1: Unexamined-Japanese-Patent No. 2010-95567). In addition, as the film becomes thin, there may be problems such as cracking during handling even after biaxial stretching, and the demand for imparting strength to the film is also increasing. It is known that, for example, rubber particles are added to a brittle thermoplastic resin to obtain a melt-extruded film excellent in bending resistance as an existing method for imparting strength (Patent Document 2: JP-A-2004-137299).

Unexamined-Japanese-Patent No. 2010-95567 JP 2004-137299 A

  In order to obtain a thin film having high strength required, a method of biaxially stretching a melt-extruded film (a film before this stretching process is also referred to as a raw fabric hereinafter) in which rubber particles are blended can be considered.

  However, according to the study of the inventor of the present invention, it has been found that although biaxial stretching of a raw fabric containing rubber particles can achieve strength application, the film is significantly whitened. When the film containing the rubber particles is biaxially stretched, the rubber particles present in the vicinity of the film surface protrude from the film surface, and the surface roughness drops and the incident light is scattered. It was identified that

  The present invention can obtain an optical film of high strength in a thin film while suppressing whitening caused by rubber particles when producing a film by biaxially stretching a melt-extruded film containing the rubber particles in view of the above-mentioned present situation It aims at providing a manufacturing method and an optical film.

  As a result of intensive investigations by the inventor of the present invention for solving the above problems, it was found that the phenomenon of protruding from the surface of the rubber particles which occurs during biaxial stretching is aggravated as the protruding state of the rubber particles on the raw fabric surface increases. Based on this finding, in order to suppress the rubber particle pop-out state on the surface of the melt extruded film, sandwich molding is performed when the melt extruded film is cooled, and a sandwiching roll having high rigidity is used as the sandwich roll to specify the sandwiching linear pressure. By doing this, it was found that the convex state of the micro particles can be smoothed on both sides, and a raw fabric with a good surface roughness can be obtained. It has been specified that it is possible to suppress the whitening problem in the stretching step by biaxially stretching using this smooth raw fabric with few surface irregularities on the surface, and reached the present invention.

That is, the present invention
(I) A method for producing an optical film comprising a thermoplastic resin composition containing a thermoplastic resin and core-shell particles, wherein in melt film formation, using a low elasticity sandwiching roll, sandwiching molding at a sandwiching linear pressure of 10 kg / cm or more A method of producing an optical film comprising: stretching a raw film having a film thickness of 200 μm or less subjected to at least 1.5 times and at most 2.6 times by biaxial stretching to obtain a stretched film.
(Ii) The method for producing an optical film according to (i), wherein the sandwiching roll is a metal roll having a crowning structure.
(Iii) The melt viscosity of the thermoplastic resin composition during die discharge is in the range of 7000 poise or more and 12000 poise or less at a shear rate of 122 sec ^-1 , and the temperature of the sandwiching roll is in the range of Tg -60 ° C. or more and Tg -20 ° C. or less The method for producing an optical film as described in (i) or (ii), which is characterized in that
(Iv) The average surface roughness Ra of a 5 μm viewing angle on both sides of the film after melt film formation is 0.1 nm or more and 4.0 nm or less, and the difference in average surface roughness on both sides is 2.0 nm or less The manufacturing method of the optical film in any one of (i)-(iii) characterized by these.
(V) The method for producing an optical film according to any one of (i) to (iv), wherein the pinching linear pressure is controlled by a load control device provided in the pinching roll pressing device.
(Vi) A thermoplastic resin composition comprising a thermoplastic resin and core-shell particles, and the average surface roughness Ra of 5 μm viewing angle of both surfaces of the film is 0.1 nm or more and 4.0 nm or less, and the average surface roughness of both surfaces A raw film having a thickness difference of not more than 2.0 nm and a film thickness of not more than 200 μm is stretched by 1.5 times or more and 2.6 times or less by biaxial stretching to obtain a stretched film. Method of producing an optical film.
(Vii) The method for producing an optical film according to any one of (i) to (vi), wherein the thermoplastic resin is an acrylic resin.
(Viii) The optical film according to any one of (i) to (vii), wherein the orientation birefringence of the optical film is −1.7 × 10 ⁻⁴ to 1.7 × 10 ^−4. Method.
(Ix) The method for producing an optical film according to any one of (i) to (viii), wherein the photoelastic constant of the optical film is −10 × 10 ⁻¹² to 4 × 10 ⁻¹² Pa ⁻¹ .
(X) The method for producing an optical film according to any one of (i) to (ix), wherein the thickness of the stretched film is in the range of 15 μm to 50 μm.
(Xi) The haze of the stretched film measured based on JISK7105 is 1.0% or less, The manufacturing method of the optical film in any one of (i)-(x) characterized by the above-mentioned.
(Xii) An optical film comprising a thermoplastic resin composition containing a thermoplastic resin and core-shell particles, and having a haze of 1.0% or less measured in accordance with JIS K 7105.
(Xiii) A thermoplastic resin composition comprising a thermoplastic resin and core-shell particles, and the average surface roughness Ra of 5 μm viewing angle of both surfaces of the film is 0.1 nm or more and 4.0 nm or less, and the average surface roughness of both surfaces The raw film for optical film manufacture whose difference of height is 2.0 nm or less and film thickness is 200 micrometers or less.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the optical film which can suppress the film whitening after biaxial stretching using the thermoplastic resin composition containing a rubber particle can be provided. According to the production method of the present invention, a thin film optical film having high transparency and high strength can be produced from a thermoplastic resin composition containing rubber particles.

FIG. 5 is a schematic view of sandwich molding according to an embodiment of the present invention.

  The present invention relates to a method for producing an optical film comprising a thermoplastic resin composition, and an optical film is produced by continuously or discontinuously biaxially stretching a film original obtained by a melt film-forming method.

  FIG. 1: is a figure which shows typically the sandwiching | molding in the melt film forming method among the manufacturing methods of this invention. The rubber particle-containing thermoplastic resin composition as a film raw material is introduced into the extruder 10, and is heated to a temperature above the glass transition temperature in the extruder 10 to be in a molten state. The thermoplastic resin composition in the molten state is transferred to the T die 11 attached to the outlet side of the extruder 10, and discharged from the die outlet 12 at the tip of the die in the molten state. The thermoplastic resin composition 13 in a molten state takes a sheet shape due to the shape of the die outlet at the time of discharge.

By sandwiching the sheet-like thermoplastic resin composition 13 in the molten state between a pair of smoothing rolls, the thermoplastic resin composition is cooled to a temperature equal to or lower than its glass transition temperature, and the sheet surface is smoothed. . One of the smoothing rolls is the sandwiching roll 14 and the other is the cast roll 15. The cast roll 15 is a hard roll made of metal. In addition, by using a roll having a crowning shape with high rigidity (a shape in which the roll diameter decreases from the center to the end in the roll width direction) as the sandwiching roll 14, high pressure is uniformly applied across the entire film. It is preferable because it can be sandwiched between and crush out the particles. As described above, the linear pressure required to crush the protrusion of the particles is 10 kg / cm or more and 30 kgf / cm or less. If the linear pressure is lower than 10 kg / cm, a portion which is not pressed by the film is generated, and it is not preferable because it is detected as a defect due to the difference in surface property with the pressed portion. Moreover, when it is higher than 30 kg / cm, there is a possibility that both ends of the cast roll / pinch roll which are not in contact with the film even if they are low elasticity rolls may contact and break, which is not preferable. According to the present invention, by controlling the conditions other than the linear pressure in a preferable range, it is possible to suppress the particle pop-out without raising the linear pressure to the area where the low elastic roll breaks. On the other hand, in order to sandwich the entire surface of the film uniformly, as a sandwiching roll, a rubber roll or a rubber roll covered with a metal sleeve, the sandwiching roll is deformed and high in which circumferential pressure can be pinched by surface contact of about several mm to several 10 mm. An elastic roll may be used as a sandwiching roll, but it is not preferable because the high elastic roll can not withstand the sandwiching linear pressure necessary to suppress the protrusion of the particles as in the present invention and thus it is broken. When the sandwich molding is performed at such a high linear pressure, optical distortion may occur due to fine sandwiching pressure unevenness, so it is preferable to use a thermoplastic resin having a low intrinsic orientation birefringence as described later.
FIG. 1 is a side view of the sheet-like thermoplastic resin composition.

  In the present invention, the pressing mechanism of the sandwiching roll uses a sensor so that the gap between the cast roll and the touch roll can be detected by the position sensor, and the load by which the sandwiching roll presses the film can be detected by using a pressure sensor. It is preferable to use a pressing mechanism that can automatically control the value of the position sensor or the value of the pressure sensor to an arbitrary value. Among them, it is preferable to control the linear pressure stably in the above-mentioned range during film production and using the value of the pressure sensor in order to eliminate the particle jumping out of the film surface. In the present invention, the linear load is easily set during operation by adjusting the pressing load by the pressing cylinder operation amount using a value obtained by dividing the pressing load sensed by the pressure sensor by the film width as the linear pressure. It is possible.

Further, in the present invention, it is preferable that the melt viscosity at the time of die discharge be in the range of 7000 to 12000 poise at a shear rate of 122 sec ⁻¹ . The temperature of the rubber-containing thermoplastic resin composition at the time of die discharge may be set so as to satisfy this condition. This temperature is a resin composition temperature which is measured immediately after being discharged from the die and which is measured before sandwiching by a pair of smoothing rolls. For this resin composition temperature, change the set temperature of the extrusion device such as extruder cylinder temperature, adapter, die temperature, etc., or control the conditions of extruder screw rotation speed, extruder screw type (compression ratio etc.) Can be adjusted by When the melt viscosity is less than 7000 poise, it is necessary to raise the temperature of the resin composition to a temperature exceeding the decomposition start temperature, thermal degradation of the resin occurs, and many bumps occur in the film. When the melt viscosity exceeds 12000 poise, the viscosity of the resin composition becomes too high, so it becomes easy to take in air during sandwich molding, and a large number of fine depressions are formed on the film surface, which is not preferable. Preferably, it is not less than 7000 poise and not more than 12000 poise. In addition, preferably, the melt viscosity is a molecular weight of the matrix of the rubber-containing thermoplastic resin composition, a composition / molecular weight of rubber particles, etc. so as to be 7000 poise or more and 12000 poise or less when measured at a shear rate of 122 sec-1 at 270 ° C. It is preferable to design. In this case, it is preferable because the molding which suppresses the particle popping out at a temperature lower than the decomposition temperature at the molding temperature becomes easy.

  The average surface roughness Ra of a 5 μm viewing angle when observing both sides of the film raw fabric after this melt extrusion with a scanning probe microscope is 0.1 nm or more and 4.0 nm or less, and the difference in the average surface roughness of both sides Is preferably 2.0 nm or less. More preferably, the difference in average surface roughness Ra between both surfaces is 0.1 nm or more and 3 nm or less. Thus, according to the observation in the extremely fine range, the existence state of the rubber particles on the film surface can be known, and if the average surface roughness Ra is in this range as an index of the unevenness state, both sides of the film It is in a state where the rubber particles are sufficiently suppressed from coming out similarly, and it is possible to suppress the protrusion of the rubber particles in the biaxial stretching step, and as a result, whitening is also caused in the film after biaxial stretching which is the final form. It is preferable because it does not occur. If the difference in surface roughness on both sides is greater than 2.0 nm, the deformation behavior in the stretching step in each case is different, and it is not preferable because the particles are likely to fly out on either side.

  The cooling temperature of the casting roll may be usually set based on the glass transition temperature, and the setting temperature of the casting roll which the film first contacts is in the range of glass transition temperature -70 ° C or more of thermoplastic resin, glass transition temperature -20 ° C It is preferable to If the cast roll temperature is higher than the glass transition temperature -20 ° C, the film is not cooled sufficiently and is transported while being stuck to the cast roll, and streak defects occur intermittently in the film width direction, which is preferable. Absent. If the glass transition temperature is lower than -60 ° C, the film is less likely to be deformed during sandwiching, and the film surface smoothing effect is low, that is, it is difficult to suppress the particle popping out, so the whitening suppression effect after stretching is reduced. Unfavorable. If it is in the said range, since a smoothing effect can fully be taken out without a defect, it is preferable. More preferably, it is the range of glass transition temperature -65 degreeC or more and glass transition temperature -30 degreeC. It is preferable that the cooling roll after a cast roll shall be +/- 30 degreeC with respect to cast roll preset temperature. The cooling roll can be optionally installed between one and a plurality of rolls so that the film can be sufficiently cooled and solidified depending on the film transport speed. The touch roll is preferably set to ± 10 ° C. with respect to the cast roll set temperature.

  Further, in the present invention, as an extruder, a single screw extruder, a same direction meshing type twin screw extruder, a same direction non meshing type twin screw extruder, a different direction meshing type twin screw extruder, a different direction non meshing type twin screw Various extruders, such as an extruder and a multi-screw extruder, can be used. Among them, the single-screw extruder is preferable because it has few resin retention parts in the extruder, it is possible to prevent the thermal deterioration of the resin during extrusion, and the facility cost is low. In addition, it is preferable to use an extruder having a vent mechanism to remove residual volatile components in the resin and heat generation products in the extruder. The size (bore size) of the extruder is preferably selected in accordance with the desired discharge rate.

  As a form of a raw material of the thermoplastic resin to be introduced into the extruder, it is preferable to use a solid resin, preferably a pellet shape of 3 mm square. The resin in pellet form is fed into the extruder through a hopper attached to the feed port of the extruder. It is preferable that the resin supplied to the extruder is in a state where it is dried by heating in advance to remove water, in order not to cause hydrolysis or oxidative deterioration of the resin. The water content in the resin is preferably 200 ppm or less, and the drying conditions can be achieved in an atmosphere temperature of 90 to 100 ° C. in 3 hours or more. At the time of drying, it is preferable to remove the atmosphere oxygen in the dryer to remove oxygen in the resin, and to remove the atmosphere oxygen in the dryer, it is preferable to make the inside of the dryer an inert gas atmosphere such as nitrogen. .

  Drying is performed by using a hopper type drier in which a drying mechanism is provided to the hopper supplying the pellets to the extruder in view of the necessary drying time and resin consumption time, or using a drier before supplying the resin to the hopper There is a method of supplying the hopper so as not to absorb moisture, or a method of using both of them. Among them, the method using a hopper type drier is preferable because the amount of water can be surely suppressed until immediately before the resin is supplied to the extruder, and further, by using a drier before the hopper, the high temperature in the hopper drier In the hopper type drier, it is further preferable to use a dehumidifying atmosphere so as to prevent moisture from entering, since moisture is not mixed even at low temperatures. Elevated temperatures in the hopper are preferred because they cause blocking problems and fluctuations in the extruder feed. Specifically, after drying under necessary conditions using a hopper pre-drier, by setting the atmosphere temperature in the hopper-type drier to 40 to 100 ° C., the moisture content can be suppressed and the extrusion stability can be compatible. When the temperature is different as described above, the pellet temperature in the hopper type drier is about 2 to 5 times the discharge amount per hour (that is, 2 to 5 hours) in order to stabilize from the hopper pre-drier drying temperature. It is preferable to follow the procedure.

  As a screw used in a single screw extruder, a general full-flight configuration having a compression ratio of about 2 to 3 with no vent or with an extruder can be used, but a special is used so that unmelted matter does not remain. It may have a kneading mechanism (mixing element).

  The molten resin obtained by the melting means such as an extruder is then preferably supplied to the die using a gear pump. By using the gear pump, the discharge amount fluctuation in the extruder is absorbed, the quantitativeness of the supply is remarkably improved, and the stability of the film thickness with time is improved.

  The molten resin quantitatively supplied from the gear pump or the molten resin directly supplied from the extruder is supplied to the die through, for example, a tubular flow path and discharged from the die in the form of a film. It is preferable to provide a foreign matter removing device in the resin flow path from the gear pump to the die, or in the resin flow path from the melting means to the die when not via a gear pump or the like. As a result, it is possible to trap foreign particles contained in the raw material resin and foreign particles generated by the extruder or gear pump, and to reduce foreign particle defects in the film. As the foreign matter removing device, a screen mesh, a pleated filter, a leaf disc filter or the like is used. Among them, the use of a leaf disk type filter enables filtration with a small volume and a large filtration area, so that the filtration accuracy can be made finer, and it is preferable from the relationship between the pressure limit and the time until clogging of the filter by foreign matter. The filter medium of the filter to be used may be a sintered non-woven fabric of metal fibers, and it is preferable to select a filter filtration accuracy of 1 to 20 μm cut, preferably 3 to 10 μm cut for optical use. Thereby, it is possible to remove the foreign matter of 20 μm size which causes a problem in the optical film to a level which does not cause a problem. Then, the number and the size of the filter element are determined, but in order to shorten the residence time at that time, it is preferable to reduce the size as much as possible with respect to the withstand pressure. In addition, it is preferable to design a flow path such as a gap of each part in the filter so as to eliminate stagnation of each part.

  Although the thing of various structures can be used for the die | dye used by this invention, T die | dye is preferable, for example, a common coat hanger die | dye can be used. Furthermore, as a width direction thickness adjustment mechanism, it is preferable to be able to adjust the gap at an arbitrary portion in the width direction of the lip by pushing in a bolt or the like. Furthermore, the film thickness can be measured online, and it is possible to automatically adjust the part where there is a deviation from an arbitrary thickness profile, for example, adjusting the thickness profile automatically using a thermally actuated bolt. It is preferable because it can be accurately performed without the use of hands.

  For the T-die lip portion, the edge bright line width when the lip edge accuracy is observed with a microscope from an angle of 45 ° with respect to the die is 10 μm or less, more preferably within the full die width, particularly the width of the film used as a product. The range of 5 μm or less is preferable. If the die lip portion is subjected to ceramic spray treatment, the line width accuracy can be increased to the scope of the present invention, which is preferable. In addition, since chipping is likely to occur when the ceramic thermal spray treatment is performed, it is preferable to control in a state where there is no chipping of 10 μm width or less in width and depth. When a chipping occurs, it is preferable to make the bright line width accuracy within the above range without chipping again by polishing or the like.

  In addition, it is preferable that the molten resin residence time from the extruder to T-die discharge be 15 minutes or less, more preferably 10 minutes or less. If the residence time is longer than this, even if the temperature is lowered as in the present invention, the resin thermal deterioration occurs, which is not preferable. When a leaf disc filter is used, it is the leaf disc filter that takes the most residence time from the extruder to the T-die discharge, so in order to achieve this residence time, it was adjusted to the desired output as described above It is preferable to give priority to filter size design.

  Further, the film can be taken up by various methods, and for example, it can be obtained as a film original fabric by taking it up with a nip roll installed after a cooling roll and then winding it around a take-up core. At this time, since the film thickens due to the effect of neck-in generated when the resin is discharged from the T-die, when the film thickness of the end affects the thickness profile after biaxial stretching, The ends may be trimmed with various cutters (for example, shear blades or leather blades). The width direction thickness profile of the raw fabric manufactured in this way can set an optimum value arbitrarily according to the biaxial stretching method and conditions, and makes the height in the width direction flat or higher than the center, or Make both ends lower than the center, etc.

  In order to give a desired product thickness and impart strength, it is necessary to draw a thin film obtained in this manner into a thin film by stretching in two directions by biaxial stretching. At this time, the raw fabric is 70 μm to 200 μm, and is stretched by 1.5 times to 2.6 times by biaxial stretching to obtain a film having a film thickness of 15 μm to 50 μm. By stretching to 1.5 times or more and 2.6 times or less by biaxial stretching, it is possible to provide strength and to suppress whitening. When the draw ratio is less than 1.5 times, the molecular orientation becomes small by drawing, and sufficient strength can not be obtained, which is not preferable. The strength is preferably 500 times or more in a bending fatigue test (MIT test) of a 40 μm thick film as an index of bending resistance. More preferably, it is 1000 times or more. If it is higher than 2.6 times, the film will be whitened without suppressing the particle popping out in the stretching step even when the particle popping out in the raw fabric is suppressed. When the film thickness of the raw fabric is 70 μm or less, since the raw fabric is thin, smoothing in sandwich molding is not sufficiently performed, and the protrusion of rubber particles can not be suppressed even by the method of the present invention, and the film becomes white after biaxial stretching. Unfavorable because it is easy. From the viewpoint of strength and whitening, a film excellent in quality can be obtained by setting the draw ratio in the above-mentioned range in order to obtain a desired final film thickness. The desired film thickness is set in the range of 15 μm or more and 50 μm or less required for the optical film, while the original film is set in the range of 70 μm or more and 200 μm or less so that the draw ratio becomes the above range. preferable.

  The biaxial stretching in the present invention may be sequential biaxial stretching or simultaneous biaxial stretching. In addition, although the raw fabric obtained by the melt extrusion method may be treated either continuously or by rolling up the raw fabric and unwinding the wound roll, either may be treated, but from the viewpoint of productivity, it is continuous. It is preferable to As the sequential biaxial stretching, longitudinal stretching in the longitudinal direction (film flow direction) and stretching in the transverse direction (film width direction) can be performed in any order. As a longitudinal stretching method, a film is plasticized by two or more heating rolls provided with a nip roll, and a roll stretching method of stretching with a roll peripheral speed difference, a film is plasticized in a heating oven, and nip rolls are provided before and after the oven. It is possible to use various methods such as a zone stretching method in which stretching is performed at the peripheral speed difference using a roll to be used. As the transverse stretching method, various methods can be used such as a method in which both ends of the film are gripped with clips and pins, plasticized in the oven, and the distance between gripping parts is expanded in the width direction in the oven. In the case of the transverse stretching, a grip portion is present, and the grip portion is not suitable as a product because a grip mark remains and it is preferable to slit both ends. Although various cutters (for example, a shear blade, a leather blade, etc.) can be used for the slit, a shear blade is preferable from the viewpoint of continuous formability.

  According to the present invention, it is possible to suppress the protrusion of rubber particles even after biaxial stretching, and to obtain a film excellent in transparency. With regard to transparency, the haze of the film after biaxial stretching is preferably 1.0% or less, more preferably 0.8% or less, and still more preferably 0.5% or less. In the biaxial stretching, if the popping out of the surface particles is not suppressed in the melt extrusion method as in the present invention, the popping out of the rubber particles during stretching becomes remarkable, light is scattered on the film surface, and the film is whitened. Such a film is not preferable as an optical film because it lowers the luminance. However, according to the present invention, even a film containing rubber particles can effectively suppress whitening and can be suitably used as an optical film. In addition, in this specification, a haze means the haze measured based on JISK7105.

  The thermoplastic resin composition that can be used in the present invention is not particularly limited as long as it is a thermoplastic resin composition that can be used as an optical film and can be molded by melt extrusion. For example, polycarbonate resin, aromatic vinyl resin and its hydrogenated substance, polyolefin resin, acrylic resin, polyester resin, polyarylate resin, polyimide resin, polyether sulfone resin, polyamide resin, cellulose resin, The thermoplastic resin composition containing thermoplastic resin and core-shell particle | grains, such as polyphenylene oxide resin, is mentioned.

  Although a thermoplastic resin composition containing rubber particles can be used as a material of an optical film, rubber particles may be present on the film surface and the surface smoothness of the film may be impaired. In such a case, it is expected that the rubber particles are pushed into the inside of the film by carrying out sandwich molding after melt extrusion, and the surface smoothness of the film is improved. However, when the compatibility between the rubber particles and the matrix resin is low, the rubber particles are easily aggregated in the film, and as a result, the unevenness of the film surface may be increased. In such a case, in the sandwich molding under the normal conditions, it is not possible to reduce the fine irregularities on the surface, and as a result, there is a disadvantage that the surface unevenness which is undesirable for the optical film is observed.

  However, according to the present invention, even if the thermoplastic resin composition contains rubber particles, and the rubber particles have low compatibility with the matrix resin, the fine unevenness on the surface is reduced, and the surface unevenness is reduced. The effect of reducing can be achieved.

  Hereinafter, a rubbery polymer-containing acrylic resin composition which is an example of a rubber particle-containing thermoplastic resin composition to which the present invention can be suitably applied will be specifically described.

  Examples of the rubbery polymer include polymers having a glass transition temperature of less than 20 ° C. More specifically, for example, a butadiene-based crosslinked polymer, a (meth) acrylic-based crosslinked polymer, and an organosiloxane-based polymer A crosslinked polymer etc. are mentioned. Among them, a (meth) acrylic crosslinked polymer (acrylic rubbery polymer) is particularly preferable in view of the weather resistance (light resistance) and transparency of the film.

  Examples of the acrylic rubber-like polymer include ABS resin rubber and ASA resin rubber, but from the viewpoint of transparency etc., an acrylic graft copolymer containing an acrylic ester-based rubbery polymer (described below) , And simply referred to as "acrylic graft copolymer" can be preferably used.

  The acrylic graft copolymer can be obtained by polymerizing a monomer mixture containing a methacrylic acid ester as a main component in the presence of an acrylic acid ester rubbery polymer.

  An acrylic acid ester type rubbery polymer is a rubbery polymer containing an acrylic acid ester as a main component, and specifically, 50 to 100% by weight of acrylic acid ester and another vinyl monomer which can be copolymerized Monomer mixture (100% by weight) consisting of 50 to 0% by weight, and 0.05 to 10 parts by weight of multifunctional monomer having two or more nonconjugated reactive double bonds per molecule (single Those obtained by polymerizing 100 parts by weight of the mixture of monomers are preferred. All of the monomers may be mixed and used, or the monomer composition may be changed and used in two or more stages.

  As an acrylic ester, it is preferable to use a C1-C12 thing of an alkyl group from the point of polymerizability or cost. For example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, etc. These monomers may be used in combination of two or more. The amount of acrylic ester is preferably 50% by weight to 100% by weight in 100% by weight of the monomer mixture, more preferably 60% by weight to 99% by weight, still more preferably 70% by weight to 99% by weight, and 80 % To 99% by weight is most preferable. If the content is 50% by weight or more, impact resistance is unlikely to be reduced, elongation at the time of tensile fracture is not likely to be reduced, and cracking tends to be difficult to occur at the time of film cutting.

  As the other copolymerizable vinyl-based monomer, (meth) acrylic acid esters are particularly preferable from the viewpoint of weatherability and transparency, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid n -Butyl, 2-butyl methacrylate, isobutyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, phenoxyethyl (meth) acrylate, phenyl (meth) acrylate and the like. Further, aromatic vinyls and derivatives thereof and vinyl cyanides are also preferable, and examples thereof include styrene, methylstyrene, acrylonitrile and methacrylonitrile. In addition, unsubstituted and / or substituted maleic anhydrides, (meth) acrylamides, vinyl esters, vinylidene halides, (meth) acrylic acids and salts thereof, (hydroxyalkyl) acrylic esters and the like can be mentioned.

  Multifunctional monomers may be those commonly used, 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, tetromethylolmethane tetramethacrylate, dipropylene glycol dimethacrylate and acrylates thereof can be used. Two or more of these polyfunctional monomers may be used.

  The amount of the polyfunctional monomer is preferably 0.05 to 10 parts by weight, and more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the total amount of the monomer mixture. When the addition amount of the polyfunctional monomer is 0.05 parts by weight or more, a crosslinked body tends to be easily formed, and when the addition amount is 10 parts by weight or less, the crack resistance of the film tends to be hardly reduced.

  The volume average particle diameter of the rubbery polymer is preferably 20 to 450 nm, more preferably 20 to 300 nm, still more preferably 20 to 150 nm, and most preferably 30 to 80 nm. The crack resistance hardly deteriorates at 20 nm or more. On the other hand, transparency is hard to fall that it is 450 nm or less. In the present specification, the volume average particle size means a volume average particle size measured by a dynamic scattering method, and can be measured, for example, by using MICROTRAC UPA 150 (manufactured by Nikkiso Co., Ltd.).

  The acrylic graft copolymer is a monomer mixture 95 composed mainly of methacrylic acid ester in the presence of 5 to 90 parts by weight (more preferably 5 to 75 parts by weight) of an acrylic acid ester type rubbery polymer. Those obtained by polymerizing 25 parts by weight in at least one step are preferred. The methacrylic acid ester in the graft copolymerization composition (monomer mixture) is preferably 50% by weight or more. If the content is 50% by weight or more, the hardness and the rigidity of the obtained film tend to be hardly reduced. As monomers used for graft copolymerization, the above-mentioned methacrylic acid esters, acrylic acid esters, vinyl-based monomers capable of copolymerizing these can be similarly used, and methacrylic acid esters and acrylic acid esters are suitably used. Be done. From the viewpoint of compatibility with the acrylic resin, methyl methacrylate is preferable, and from the viewpoint of suppressing zipper depolymerization, methyl acrylate, ethyl acrylate, and n-butyl acrylate are preferable.

  From the viewpoint of optical isotropy, it is referred to as (meth) acrylic monomer ("ring structure-containing (meth) acrylic monomer") having an alicyclic structure, a heterocyclic structure or an aromatic group. Are preferred, and specific examples thereof include benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate and phenoxyethyl (meth) acrylate. The amount thereof used is 1 to 100% by weight in 100% by weight of the total of the monomer mixture (the total of the ring structure-containing (meth) acrylic monomer and the other monofunctional monomer copolymerizable therewith) Is preferred, 5 to 70 wt% is more preferred, and 5 to 50 wt% is most preferred. As the other monofunctional monomers copolymerizable therewith, the above-mentioned methacrylic acid esters, acrylic acid esters and other copolymerizable vinyl monomers can be used in the same manner.

  The grafting ratio to the acrylic acid ester rubbery polymer is preferably 10 to 250%, more preferably 40 to 230%, and most preferably 60 to 220%. When the graft ratio is 10% or more, the acrylic graft copolymer is difficult to aggregate in the molded body, and there is little possibility that the transparency is lowered or foreign matter is generated. In addition, the elongation at the time of tensile fracture is less likely to be reduced, and there is a tendency that cracking is less likely to occur at the time of film cutting. When it is 250% or less, for example, the melt viscosity at the time of film formation is difficult to increase, and the formability of the film tends not to be reduced. The calculation formula is described below.

The graft ratio is the weight ratio of the graft component in the acrylic graft copolymer, and is measured by the following method.
2 g of the obtained acrylic graft copolymer is dissolved in 50 ml of methyl ethyl ketone, and centrifuged at 30,000 rpm at a temperature of 12 ° C. for 1 hour using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CP 60 E) And solubles (total centrifugation 3 times). The obtained insoluble matter is calculated by the following equation as an acrylic ester graft polymer.
Graft ratio (%) = [{(weight of methyl ethyl ketone insoluble matter) − (weight of acrylic acid ester type rubbery polymer)} / (weight of acrylic acid ester type rubbery polymer)] × 100

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

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

  The polymerization temperature is preferably 30 ° C. or more and 100 ° C. or less, more preferably 50 ° C. or more and 80 ° C. or less. When the temperature is 100 ° C. or less, the target molecular weight tends not to be excessively large and the quality tends to be hardly deteriorated at a temperature of 100 ° C. or less. Raw materials such as acrylic acid ester monomer, initiator, emulsifier, and deionized water continuously added to the polymerization reaction tank can be accurately added under the control of the metering pump, but the heat of polymerization generated in the reaction tank In order to secure the heat removal amount of the above, it is possible to cool in advance if necessary. If necessary, a polymerization inhibitor, a coagulant, a flame retardant, an antioxidant, and a pH adjuster may be added to the latex discharged from the reaction tank, so that recovery and post polymerization of unreacted monomers may be performed. You may go. Thereafter, the copolymer can be obtained through known methods such as coagulation, heat treatment, dehydration, water washing and drying.

  In the emulsion polymerization, conventional polymerization initiators can be used. For example, inorganic peroxides such as potassium persulfate and sodium persulfate, organic peroxides such as cumene hydroperoxide and benzoyl peroxide, and oil-soluble initiators such as azobisisobutyronitrile are also used. These may be used alone or in combination of two or more. These initiators are used as conventional redox type polymerization initiators in combination with a reducing agent such as sodium sulfite, sodium thiosulfate, sodium formaldehyde, sulfoxylate, askorobinic acid, ferrous sulfate and disodium ethylenediaminetetraacetic acid complex. You may use it.

  A chain transfer agent may be used in combination with the polymerization initiator. The chain transfer agent includes alkyl mercaptan having 2 to 20 carbon atoms, mercapto acids, thiophenol, carbon tetrachloride and the like, and these 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 conventional emulsifier for emulsion polymerization can be used. For example, sulfate ester surfactants such as sodium alkyl sulfate, sulfonate sodium surfactants such as sodium alkyl benzene sulfonate, sodium alkyl sulfonate, sodium dioctyl sulfosuccinate, sodium alkyl alkyl phosphate, polyoxyethylene alkyl ether Anionic surfactants such as phosphate surfactants such as sodium phosphate ester may be 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 forms of terminal hydroxyl groups may be used or partially used in combination. Among them, sulfonate surfactants or phosphate surfactants are preferable from the viewpoint of polymerization reaction stability and particle system controllability, and among them, dioctyl sulfosuccinate or polyoxyethylene alkyl ether phosphoric acid Ester salts can be more preferably used.

  The amount of the emulsifier used is preferably 0.05 parts by weight or more and 10 parts by weight, more preferably 0.1 parts by weight or more and 1.0 parts by weight or less, based on 100 parts by weight of the entire monomer component. If it is 0.05 parts by weight or more, the particle size of the copolymer does not become too large, and if it is 10 parts by weight or less, the particle size of the copolymer does not become too small, and the particle size distribution hardly deteriorates.

  The rubbery polymer-containing acrylic resin composition in the present invention is not particularly limited, but is preferably a mixed composition of one or more acrylic rubbery polymers and one or more acrylic resins.

  The acrylic rubber-like polymer is preferably compounded such that the rubber-like polymer contained in the acrylic rubber-like polymer is contained in an amount of 1 to 60 parts by weight in 100 parts by weight of the thermoplastic resin composition, It is more preferable to be blended so as to be contained by 30 to 30 parts by weight, and it is further preferable to be blended so as to be contained 1 to 25 parts by weight. If it is 1 part by weight or more, the film is hardly deteriorated in crack resistance and vacuum formability, or the photoelastic constant is increased to be inferior in optical isotropy. On the other hand, when the amount is 60 parts by weight or less, the heat resistance, surface hardness, transparency, and resistance to bending whitening of the film tend not to deteriorate.

  The mixture of the acrylic rubbery polymer and the acrylic resin may be directly mixed at the time of film production, and once the acrylic rubbery polymer and the methacrylic resin are mixed and pelletized, the film production is performed again. May be implemented.

（式中、Ｒ１及びＲ２は、それぞれ独立して、水素又は炭素数１〜８のアルキル基であり、Ｒ３は、炭素数１〜１８のアルキル基、炭素数３〜１２のシクロアルキル基、又は炭素数５〜１５の芳香環を含む置換基である。）
で表される単位（以下、「グルタルイミド単位」ともいう）と、
下記一般式（２）

（式中、Ｒ４及びＲ５は、それぞれ独立して、水素又は炭素数１〜８のアルキル基であり、Ｒ６は、炭素数１〜１８のアルキル基、炭素数３〜１２のシクロアルキル基、又は炭素数５〜１５の芳香環を含む置換基である。）
で表される単位（以下、「（メタ）アクリル酸エステル単位」ともいう）とを含むグルタルイミドアクリル系樹脂を好適に用いることができる。 The acrylic resin is not particularly limited, but a methacrylic resin containing methyl methacrylate as a monomer component can be used, and one containing 30 to 100% by weight of methyl methacrylate is preferable. In addition, a heat-resistant acrylic resin can be used. For example, an acrylic resin in which an N-substituted maleimide compound is copolymerized as a copolymer component, a glutaric anhydride acrylic resin, an acrylic resin having a lactone ring structure, glutar resin Imido acrylic resin, acrylic resin containing a hydroxyl group and / or carboxyl group, aromatic vinyl monomer, and aromatic vinyl-containing polymer obtained by polymerizing another monomer copolymerizable therewith, or aroma thereof Aromatic vinyl-containing polymer obtained by partially or completely hydrogenating the aromatic ring (eg, styrene polymer obtained by polymerizing styrene monomer and other monomer copolymerizable therewith) (A partially hydrogenated styrenic polymer obtained by partially hydrogenating the aromatic ring of the above), an acrylic polymer containing a cyclic acid anhydride repeating unit, etc. Kill. Glutarimide acrylic resins can be more preferably used from the viewpoint of heat resistance and optical properties. The glutarimide acrylic resin is described in detail below. Specifically as glutar imide acrylic resin, for example, the following general formula (1)

(Wherein, R 1 and R 2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 3 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or It is a substituent containing a C5-C15 aromatic ring.)
A unit represented by (hereinafter also referred to as "glutarimide unit"),
Following general formula (2)

(Wherein, 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, a cycloalkyl group having 3 to 12 carbon atoms, or It is a substituent containing a C5-C15 aromatic ring.)
Glutarimide acrylic resin containing a unit represented by (hereinafter also referred to as “(meth) acrylic ester unit”) can be suitably used.

（式中、Ｒ７は、水素又は炭素数１〜８のアルキル基であり、Ｒ８は、炭素数６〜１０のアリール基である。）
で表される単位（以下、「芳香族ビニル単位」ともいう）を更に含んでいてもよい。 Further, the above glutarimide acrylic resin may, if necessary, be represented by the following general formula (3)

(Wherein, 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.)
And the unit represented by (hereinafter, also referred to as "aromatic vinyl unit") may be further included.

  In the above general formula (1), R 1 and R 2 are each independently hydrogen or methyl, R 3 is preferably hydrogen, methyl, butyl or cyclohexyl, and R 1 is methyl It is more preferable that R2 is hydrogen and R3 is a methyl group.

  The glutarimide acrylic resin may contain only a single kind of glutarimide unit, or may contain plural kinds of different R1, R2 and R3 in the general formula (1). .

  The glutarimide unit can be formed by imidizing the (meth) acrylic acid ester unit represented by the above general formula (2).

  And acid anhydrides such as maleic anhydride, or half esters of such acid anhydrides and linear or branched alcohols having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, The glutarimide unit can also be formed by imidizing an .alpha.,. Beta.-ethylenically unsaturated carboxylic acid such as itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, citraconic acid and the like.

  In the above general formula (2), R4 and R5 are each independently hydrogen or methyl, R6 is preferably hydrogen or methyl, R4 is hydrogen, R5 is methyl, More preferably, R 6 is a methyl group.

  The above glutarimide acrylic resin may contain only a single type of (meth) acrylic acid ester unit, and includes a plurality of types in which R4, R5, and R6 in the general formula (2) are different. It may be.

  The glutarimide resin preferably contains styrene, α-methylstyrene or the like as the aromatic vinyl structural unit represented by the general formula (3), and more preferably contains styrene.

  Further, the glutarimide acrylic resin may contain only a single type as an aromatic vinyl structural unit, or R7 and R8 may contain a plurality of different types.

  In the glutarimide acrylic resin, the content of the glutarimide unit represented by the general formula (1) is not particularly limited. For example, it is preferable to change depending on the structure of R 3 and the like.

  Generally, the content of the glutarimide unit is preferably 1% by weight or more of the glutarimide resin, more preferably 1% by weight to 95% by weight, and 2% by weight to 90% by weight. It is more preferable to do, and it is especially preferable to set it as 3 weight%-80 weight%.

  If the content of the glutarimide unit is within the above range, the heat resistance and transparency of the resulting glutarimide resin may be reduced, or the moldability and mechanical strength when processed into a film may not be reduced. .

  In the glutarimide acrylic resin, the content of the aromatic vinyl unit represented by the general formula (3) is not particularly limited, and can be appropriately set according to the physical properties to be obtained. Depending on the use to be used, the content of the aromatic vinyl unit represented by the general formula (3) may be zero. When it contains the aromatic vinyl unit represented by General formula (3), it is preferable to be 10 weight% or more on the basis of the total repeating unit of glutar imide acrylic resin, and 10 weight%-40 weight% It is more preferably 15 wt% to 30 wt%, and particularly preferably 15 wt% to 25 wt%.

  When the content of the aromatic vinyl unit is within the above range, the heat resistance of the obtained glutarimide acrylic resin is not sufficient, and the mechanical strength at the time of film processing is hardly reduced.

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

  The other unit is formed, for example, by copolymerizing a nitrile monomer such as acrylonitrile and methacrylonitrile, and a maleimide monomer such as maleimide, N-methyl maleimide, N-phenyl maleimide, N-cyclohexyl maleimide and the like. A structural unit can be mentioned.

These other units may be directly copolymerized or graft copolymerized in the glutarimide acrylic resin.
The weight-average molecular weight of the glutarimide acrylic resin is not particularly limited, but is preferably 1 × 10 ^{4 to} 5 × 10 ⁵ . Within the above range, the viscosity at the time of melt extrusion becomes high, the molding processability is reduced, the productivity of the molded product is reduced, and the mechanical strength at the time of film processing is unlikely to be insufficient.

  The glass transition temperature of the glutarimide acrylic resin is not particularly limited, but is preferably 110 ° C. or more, and more preferably 120 ° C. or more. If the glass transition temperature is within the above range, the application range of the obtained thermoplastic resin composition can be expanded.

  Although the manufacturing method in particular of the said glutar imide acrylic resin is not restrict | limited, For example, the method etc. which are described in Unexamined-Japanese-Patent No. 2008-273140 are mention | raise | lifted.

  In the thermoplastic resin composition used in the present invention, an antioxidant for improving the stability to heat and light, an ultraviolet absorber, an ultraviolet stabilizer and the like may be added singly or in combination of two or more.

  The optical film produced by the present invention may be used as a member used in a display device such as a liquid crystal display device, for example, a polarizing plate protective film, a retardation film, a brightness enhancement film, a liquid crystal substrate, a light diffusion sheet, a prism sheet, etc. Can. Among them, it is suitable for a polarizing plate protective film and a retardation film.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the measuring method of each physical property measured by the following example and a comparative example is as follows. The results are shown in Tables 1 and 2.

(Glass-transition temperature)
Using a Differential Scanning Calorimeter (DSC) SSC-5200 manufactured by Seiko Instruments Inc., heat the sample once to 200 ° C. at a rate of 25 ° C./min, hold for 10 minutes, and then to 50 ° C. at a rate of 25 ° C./min. After preliminary adjustment to lower the temperature, measurement is performed while raising the temperature to 200 ° C at a heating rate of 10 ° C / min, and an integral value is obtained from the obtained DSC curve (DDSC), and the glass transition temperature from its maximum point I asked for.

(Melt viscosity)
The melt viscosity of the pellets was measured using a capillary rheometer at the resin temperature at the extruder outlet in each of the examples and the comparative examples, and under the conditions of a shear rate of 122 sec ⁻¹ .

(Surface roughness)
Using a scanning probe microscope made by Hitachi High-Tech Science, the surface in contact with the cast roll of the original film and the surface in contact with the touch roll are measured with a contact mode AFM at a viewing angle of 5 μm to measure the average surface roughness Ra. did.

(Alignment birefringence)
After cutting out a 40 mm × 40 mm test piece from the film, the in-plane retardation is measured at a wavelength of 590 nm and an incident angle of 0 ° using an automatic birefringence meter (KOBRA-WR) manufactured by Oji Scientific Co., Ltd. The orientation birefringence was calculated.

(Photoelastic constant)
A test piece was cut out of a film into a strip of 90 mm in the film width direction and 15 mm in the film flow direction, and then measured at a wavelength of 590 nm and an incident angle of 0 ° using an automatic birefringence meter (KOBRA-WR) manufactured by Oji Measurement. For measurement, one side of the long film of the film is fixed, and the other side is measured from no load to 4 kgf under a load of 0.5 kgf, and the change in birefringence due to unit stress is calculated from the obtained result. did.

(Haze)
The haze value of the film was measured by the method described in JIS K7105 using a Nippon Denshoku Industries manufactured turbidity meter (NDH-300A).

(Bending resistance)
The bending resistance of the film was measured according to the method of JIS C5016 using a Toyo Seiki Seisakusho Co., Ltd. MIT folding fatigue tester. Measurement conditions were R = 0.38 and a load of 100 g. The measurement result is shown by the number of bending at break (hereinafter sometimes referred to as "MIT").

(Surface)
After cutting out a test piece of A4 size from the film, the projected image was copied on a screen with a point light source, and the presence or absence of a flow direction streak and a width direction streak was observed. The case where there was no streak was evaluated as ○, the case where it was seen lightly as Δ, and the case where it was seen thickly as x.

(Production Example 1)
<Production of Glutarimide Acrylic Resin (A1)>
A glutarimide acrylic resin (A1) was produced using polymethyl methacrylate as a raw material resin and monomethylamine as an imidization agent.
In this production, a tandem reaction extruder in which two extrusion reactors were arranged in series was used.
With regard to a tandem-type reactive extruder, a mesh-type co-directional twin-screw extruder having a diameter of 75 mm and a L / D ratio (the ratio of the length L to the diameter D of the extruder) of both the first extruder and the second extruder 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 pressure reduction of each vent in the first extruder and the second extruder was -0.095 MPa. Furthermore, to the pressure control mechanism in the parts connecting the 1st extruder and the 2nd extruder with piping of diameter 38 mm and 2 m in length and connecting the resin discharge port of the 1st extruder and the material supply port of the 2nd extruder Used a constant flow pressure valve.
The resin (strand) discharged from the second extruder was cooled by a cooling conveyer and then cut by a pelletizer to form pellets. Here, the discharge port of the first extruder, the first extruder, and the first extruder in order to check the pressure adjustment in the part connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder, or the extrusion fluctuation. The resin pressure gauge was provided in the center part of the connection part between 2 extruders, and the discharge port of the 2nd extruder.
In the first extruder, polymethyl methacrylate resin (Mw: 150,000) was used as a raw material resin, and imide resin intermediate 1 was produced using monomethylamine as an imidization agent. At this time, the temperature of the maximum temperature part of the extruder is 280 ° C., the screw rotation speed is 55 rpm, the feed amount of raw resin is 150 kg / hour, and the addition amount of monomethylamine is 2.0 parts by weight with respect to 100 parts by weight of raw resin. did. The constant flow pressure valve was installed immediately before the raw material supply port of the second extruder, and the pressure of the monomethyl amine press-in portion of the first extruder was adjusted to 8 MPa.
In the second extruder, after remaining the imidization agent and byproducts remaining in the rear vent and vacuum vent, dimethyl carbonate was added as an esterification agent to produce an imide resin intermediate 2. At this time, each barrel temperature of the extruder was 260 ° C., screw rotation speed was 55 rpm, and the amount of dimethyl carbonate added 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, the resin was extruded from a strand die, cooled in a water bath, and pelletized with a pelletizer to obtain a glutarimide acrylic resin (A1).
The obtained glutarimide acrylic resin (A1) is an acrylic resin in which glutamyl imide units and (meth) acrylic acid ester units are copolymerized.

(Production Example 2)
<Production of Graft Copolymer (B2)>
The following substances were charged into an 8 L polymerization apparatus equipped with a stirrer.
Deionized water 200 parts by weight polyoxyethylene lauryl ether sodium phosphate 0.05 parts by weight sodium formaldehyde sulfoxylate 0.11 parts by weight ethylenediaminetetraacetic acid-2-sodium 0.004 parts by weight ferrous sulfate 0.001 parts by weight Part After the inside of the polymerization machine is sufficiently replaced with nitrogen gas to make it substantially oxygen free, the internal temperature is brought to 40 ° C., and the raw material mixture of acrylic rubber particles (B-1) (butyl acrylate 90 mol%, methacrylic) A compound containing 0.45 parts by weight of allyl methacrylate and 0.041 parts by weight of cumene hydroperoxide with respect to 45 parts by weight of a monofunctional monomer consisting of 10 mol% of methyl acid. Was added continuously. Polyoxyethylene lauryl ether sodium phosphate (polyoxyethylene lauryl ether phosphoric acid (manufactured by Toho Chemical Industry Co., Ltd., trade name: phosphanol RD-) 20 minutes, 40 minutes, 60 minutes after the start of the addition of the raw material mixture 0.2 parts by weight of sodium salt of 510Y) was added to the polymerization machine. After completion of the addition, polymerization was further continued for 0.5 hour to obtain acrylic rubber particles (B-1) (polymer of the above-mentioned raw material mixture). The polymerization conversion was 98.6%.
Thereafter, the internal temperature is brought to 60 ° C. and 0.2 parts by weight of sodium formaldehyde sulfoxylate is charged, and then the raw material mixture of the hard polymer layer (B-2) (57.8 mol% of methyl methacrylate, butyl acrylate) 0.3 parts by weight of t-dodecyl mercaptan and 0.254 parts by weight of cumene hydroperoxide with respect to 55 parts by weight of a monofunctional monomer consisting of 4% and 38.2 mol% of benzyl methacrylate). 554 parts by weight were continuously added over 210 minutes, and polymerization was continued for another hour to obtain a graft copolymer latex. The polymerization conversion was 100.0%. The obtained latex was salted out with magnesium sulfate, coagulated, washed with water and dried to obtain a white powdery graft copolymer (B2).
The average particle diameter of the rubber particles (B-1) in the graft copolymer (B2) was 121 nm. The graft ratio of the graft copolymer (B2) was 56%.

(Production Example 3)
<Production of resin pellets 1>
Using a single-screw extruder using a full-flight screw with a diameter of 40 mm, the setting temperature of the temperature control zone of the extruder is 255 ° C., screw rotation speed is 52 rpm, 95 parts by weight of glutarimide acrylic resin (A1), and white A mixture of 5 parts by weight of the powdery graft copolymer (B2) was supplied at a rate of 10 kg / hr. The resin which came out as a strand from the die provided at the extruder outlet was cooled in a water bath and pelletized by a pelletizer. The melt viscosity was measured on the pellets as described above.

(Production Example 4)
<Production of resin pellet 2>
Using a single-screw extruder using a full-flight screw with a diameter of 40 mm, the setting temperature of the temperature control zone of the extruder is 255 ° C, screw rotation speed is 52 rpm, and 10 kg / hr for glutarimide acrylic resin (A1) only Provided at a rate of The resin which came out as a strand from the die provided at the extruder outlet was cooled in a water bath and pelletized by a pelletizer. The melt viscosity was measured on the pellets as described above.

Example 1
The pellet (glass transition temperature Tg 122 ° C.) obtained in Production Example 3 was dried at 80 ° C. for 4 hours in a dryer as a rubber-containing thermoplastic resin composition, and then supplied to a φ65 mm single-screw extruder. At the outlet of the extruder, screen meshes were placed in order of # 40, # 100, # 400, # 400, # 100, # 40 from the extruder side. It heat-melted so that resin temperature might be 270 degreeC at the extruder exit, and after letting a leaf disc filter (5 micrometers of mesh openings) pass through a gear pump, molten resin was extruded to T-die. At this time, the resin temperature immediately after discharge at the T-die outlet was 270 ° C., and the melt viscosity at 122 sec ⁻¹ at this temperature was 1050 Pa · sec. The discharged molten film was cooled and solidified by a cast roll adjusted to 70 ° C. and a touch roll adjusted to 70 ° C. (metal roll having a crowning structure). At that time, the touch roll pressing position was adjusted and adjusted so that the sandwiching pressure, which is a value obtained by dividing the pressing load detected by the load sensor provided in the touch roll double-end shaft pressing cylinder by the film sandwiching width, would be 18 kgf / cm. . The film that had been cooled and solidified was taken up by a take-up roll to obtain a raw fabric with a thickness of 140 μm. The raw fabric line speed at this time was 15 m / min.
The obtained raw fabric was simply wound up, a small amount was obtained, and evaluated. The surface roughness of the surface in contact with the cast roll was 1.4 nm, and the surface roughness of the surface in contact with the touch roll was 2.2 nm. .
This raw fabric is continuously stretched twice in the longitudinal direction by the roll longitudinal stretcher under conditions of Tg + 10 ° C, and then continuously doubled in the transverse direction by the clip type tenter transverse stretcher, Tg + 10 ° C It stretched on conditions. After slitting both ends of the stretched film continuously, the film was taken up by a take-up roll to obtain a 40 μm thick film as a take-up core. The obtained stretched film had a haze of 0.4%, an MIT of 1,200 times, and a good surface property. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Example 2)
A biaxially stretched film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that the resin temperature was 250 ° C. (the melt viscosity at 122 sec ^-1 at this temperature was 100 Pa · sec) at the extruder outlet.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.3 nm, and the surface roughness of the surface in contact with the touch roll was 2.0 nm. Moreover, the haze of the obtained stretched film was 0.7%, the MIT was 1,200 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Example 3)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the cast roll temperature was set to 40 ° C.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 3.3 nm, and the surface roughness of the surface in contact with the touch roll was 4.5 nm. Moreover, the haze of the obtained stretched film was 0.9%, the MIT was 1,200 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Example 4)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the cast roll temperature was 110 ° C.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.1 nm, and the surface roughness of the surface in contact with the touch roll was 1.7 nm. In addition, the haze of the obtained stretched film was 0.3%, the MIT was 1,200 times, and with respect to the surface property, streak defects running in a slight width direction were intermittently observed in the longitudinal direction. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Example 5)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the resin temperature was changed to 290 ° C. (the melt viscosity at 122 sec ⁻¹ at this temperature was 400 Pa · sec) at the extruder outlet.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.1 nm, and the surface roughness of the surface in contact with the touch roll was 1.8 nm. In addition, the haze of the obtained stretched film was 0.3%, the MIT was 1050 times, and there was a slightly running streak in the longitudinal direction regarding the surface property. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Example 6)
The line speed was adjusted to obtain a thickness of 100 μm, the raw fabric was obtained, and the thickness was the same as in Example 1 except that the draw ratio during stretching was 1.7 times for both longitudinal stretching and transverse stretching. A 40 μm biaxially stretched film was obtained.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.4 nm, and the surface roughness of the surface in contact with the touch roll was 2.2 nm. Moreover, the haze of the obtained stretched film was 0.3%, MIT was 900 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Example 7)
The line speed is adjusted so that the thickness of the raw fabric is 200 μm, the raw fabric is obtained, and the thickness is the same as in Example 1 except that the draw ratio during stretching is 2.4 times for both longitudinal stretching and transverse stretching. A 40 μm biaxially stretched film was obtained.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.4 nm, and the surface roughness of the surface in contact with the touch roll was 2.2 nm. Moreover, the haze of the obtained stretched film was 0.7%, MIT was 1,500 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Comparative example 1)
A 40 μm biaxially stretched film was obtained in the same manner as in Example 1 except that sandwiching was not performed (the touch roll was not used).
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 5.1 nm, and the surface roughness of the surface that would be in contact with the touch roll if it was temporarily used was 5.4 nm. Moreover, the haze of the obtained stretched film was 1.5%, the MIT was 1,200 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Comparative example 2)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the sandwiching linear pressure was 6 kg / cm.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 2.0 nm, and the surface roughness of the surface in contact with the touch roll was 4.2 nm. Moreover, the haze of the obtained stretched film was 1.1%, MIT was 1,200 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Comparative example 3)
The line speed was adjusted to obtain a thickness of 70 μm, the raw fabric was obtained, and the thickness was the same as in Example 1 except that the draw ratio during stretching was 1.4 times for both longitudinal stretching and transverse stretching. A 40 μm biaxially stretched film was obtained.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 3.0 nm, and the surface roughness of the surface in contact with the touch roll was 4.1 nm. Moreover, the haze of the obtained stretched film was 0.3%, the MIT was 600 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Comparative example 4)
The line speed was adjusted to obtain a thickness of 210 μm, and the raw fabric was obtained, and 50 μm as in Example 1 except that the draw ratio during stretching was set to 2.2 for both longitudinal stretching and transverse stretching. A biaxially stretched film was obtained.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.3 nm, and the surface roughness of the surface in contact with the touch roll was 2.0 nm. Moreover, the haze of the obtained stretched film was 1.1%, MIT was 1,000 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Comparative example 5)
The line speed is adjusted so that the thickness of the raw fabric is 250 μm and the raw fabric is obtained, and the same procedure as in Example 1 is carried out except that the draw ratio at the time of stretching is 2.8 times for both longitudinal stretching and transverse stretching. A 40 μm biaxially stretched film was obtained.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 1.2 nm, and the surface roughness of the surface in contact with the touch roll was 2.0 nm. Moreover, the haze of the obtained stretched film was 1.3%, the MIT was 1,400 times, and the surface property was good. Moreover, the photoelastic constant of the film was 0.35 * 10 <^-12> Pa < ^-1 >, the orientation birefringence was -0.13 * 10 < ^-4 > and there was no birefringence.

(Comparative example 6)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the thermoplastic resin without rubber compounding obtained in Production Example 4 was used as a pellet.
At this time, the surface roughness of the surface in contact with the cast roll of the raw fabric was 0.7 nm, and the surface roughness of the surface in contact with the touch roll was 1.1 nm. Moreover, the haze of the obtained stretched film was 0.1%, the MIT was 300 times, the stretched film was very brittle, and the surface property was good. Moreover, the photoelastic constant of the film was -4.35 * 10 < ^-12 > Pa < ^-1 >, and orientation birefringence was -0.13 * 10 < ^-4 >.

(Comparative example 7)
In Example 1, an attempt was made to raise the linear pressure to 18 kgf / cm using an elastic roll instead of a cast roll and a touch roll, but some deformation was seen in the elastic roll at a stage of 10 kg / cm or more. It was not possible to obtain a biaxially stretched film.

10. .... Extruder 11. ... T die 12. .... Die exit 13. .... Thermoplastic resin composition 14. .... Interposing roll 15. .... Cast roll

Claims (12)

  A method for producing an optical film comprising a thermoplastic resin composition containing a thermoplastic resin and core-shell particles, wherein in melt film formation, sandwich molding is performed using a low elastic sandwich roll and a sandwich linear pressure of 10 kg / cm or more. A method for producing an optical film comprising: stretching an original film having a film thickness of 200 μm or less to 1.5 times or more and 2.6 times or less by biaxial stretching to obtain a stretched film.   The method for producing an optical film according to claim 1, wherein the sandwiching roll is a metal roll having a crowning structure. The melt viscosity of the thermoplastic resin composition at die discharge is in the range of 7000 poise to 12000 poise at a shear rate of 122 sec ^-1 , and the temperature of the sandwiching roll is in the range of Tg -60 ° C to Tg -20 ° C. The manufacturing method of the optical film of Claim 1 or 2 characterized by these.   The film is characterized in that the average surface roughness Ra of a 5 μm viewing angle on both sides of the film after melt film formation is 0.1 nm or more and 4.0 nm or less, and the difference in average surface roughness on both sides is 2.0 nm or less The manufacturing method of the optical film in any one of Claims 1-3.   The method of manufacturing an optical film according to any one of claims 1 to 4, wherein the pinching linear pressure is controlled by a load control device provided in the pinching roll pressing device.   A thermoplastic resin composition containing a thermoplastic resin and core-shell particles, and the average surface roughness Ra of 5 μm viewing angles on both sides of the film is 0.1 nm or more and 4.0 nm or less, and the difference in average surface roughness on both sides An optical film characterized in that an original film having a thickness of 2.0 nm or less and a film thickness of 200 μm or less is stretched by 1.5 times or more and 2.6 times or less by biaxial stretching to obtain a stretched film. Manufacturing method.   The method for producing an optical film according to any one of claims 1 to 6, wherein the thermoplastic resin is an acrylic resin. The method for producing an optical film according to any one of claims 1 to 7, wherein the orientation birefringence of the optical film is -1.7 ^10-4 to 1.7 ^10-4 . The photoelastic constant of an optical film is -10 * 10 <^-12> to 4 * 10 <^-12> Pa < ^-1 >, The manufacturing method of the optical film in any one of the Claims 1-8 characterized by the above-mentioned.   The film thickness of a stretched film is 15 micrometers or more and 50 micrometers or less, The manufacturing method of the optical film in any one of the Claims 1-9 characterized by the above-mentioned.   The haze of the stretched film measured based on JISK7105 is 1.0% or less, The manufacturing method of the optical film in any one of Claims 1-10 characterized by the above-mentioned. A thermoplastic resin composition containing a thermoplastic resin and core-shell particles, and the average surface roughness Ra of 5 μm viewing angles on both sides of the film is 0.1 nm or more and 4.0 nm or less, and the difference in average surface roughness on both sides A raw film film for producing an optical film having a thickness of 2.0 nm or less and a film thickness of 200 μm or less.

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