JP2010100746A - Optical film and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having high heat resistance, transparency, optical isotropy, toughness, zero-defect property and less thickness unevenness. <P>SOLUTION: The optical film comprises a thermoplastic resin (A) as a structural component having a glass transition temperature of 120°C or higher, a melt viscosity of 6,000 to 100,000 poise at 260°C at a shear velocity of 12 sec<SP>-1</SP>, and a cyclic structure, and a second component (B) comprising a polymer by 5 to 40 mass%; and the film has a haze value of not more than 1%, b-value of not more than 1, a thickness of 10 to 100 μm, less than 0.5 mass% content of a component having a boiling point of 100 or lower, and foreign matter defects having a size of 20 μm or larger by less than 20 by number/m<SP>2</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical film excellent in transparency and defect-free property and a method for producing the same.

  Amorphous transparent resins typified by polycarbonate resins and polymethyl methacrylate resins are widely used in the electric and electronic fields (Non-patent Documents 1 and 2). In particular, polycarbonate resin is used as a base material for recording media such as compact discs, but has a problem that the photoelastic coefficient is large and the birefringence is large. Polymethyl methacrylate resin, on the other hand, has low birefringence and excellent optical properties, but it is not sufficient in heat resistance and has problems when used in applications that require heat resistance such as laser write-once optical disks. is there. With regard to improving the heat resistance of acrylic thermoplastic resins such as polymethylmethacrylate resin, the heat resistance can be improved by improving the polymer skeleton and composition, such as copolymerization with acid anhydrides and maleimide compounds, and introduction of glutarimide structures. A method (for example, Patent Document 1) is disclosed.

  However, in recent years, the demand for acrylic thermoplastic resin films used in optical parts has become more sophisticated and diversified. In addition to the above heat resistance, etc., extremely high transparency, defect-freeness, thinning, and reduction in thickness unevenness. Has come to be required. Patent Documents 2 and 3 describe the improvement of transparency in addition to the improvement of heat resistance of acrylic thermoplastic resin films. However, Patent Document 2 discloses so-called solution film formation in which a polymer component is dissolved in a solvent. Since the method is used, a process and cost for removing the solvent are required, and in terms of quality and physical properties, there are problems such as a bumping defect when removing the solvent and a decrease in physical properties due to the residual solvent.

In order to increase the toughness when an acrylic thermoplastic resin film is produced by the melt film-forming method, for example, as disclosed in Patent Document 4, an acrylic resin film by the melt film-forming method has been proposed. When the elastomer particles are added, coarse protrusions called “coagulum” are statistically generated during the formation of the elastomer particles, and this causes a defect in which the defect of the foreign matter can be visually observed, a so-called bright spot defect. Therefore, the improvement was essential. However, since the elastomer particles are very soft, such fine defects cannot be improved even if the accuracy of the filter in the extrusion is improved because the filter penetrates the filter due to the high viscosity at the time of extrusion.
“Current status and future prospects of plastic films and sheets”, Fuji Chimera Research Institute, Inc. (Publisher: Ryoyoshi Omotesaki), June 4, 2004, p165-p168 "Transparent resin for optics", Technical Information Association, Inc. (Issue: Kazuhiro Takahisa), December 17, 2001, p59 JP-A-7-268036 JP 2006-206881 A JP 2006-283013 A Japanese Patent No. 2008-201981

  The object of the present invention is to solve the above-mentioned conventional problems, have excellent optical properties, and have excellent heat resistance, transparency, optical isotropy, defect-free property, thin film, mechanical strength, and a thermoplastic resin film. And providing a manufacturing method thereof.

The present invention for solving the above-described problems has the following configuration.
(1) Thermoplastic resin A having a cyclic structure having a glass transition temperature of 120 ° C. or higher, a temperature of 260 ° C., and a melt viscosity at a shear rate of 12 sec ⁻¹ in the range of 6,000 to 100,000 poise, is a constituent component. The second component B made of a polymer is contained in the range of 5 to 40% by mass, the haze value is 1% or less, the b value is 1 or less, the thickness is 10 to 100 μm, and the boiling point is 100 ° C. or less. An optical film having a component content of less than 0.5% by mass and a foreign matter defect size of 20 μm or more of less than 20 / m ² .
(2) The optical film according to (1), wherein the second component B is elastomer particles.
(3) The optical film as described in (1) or (2) above, wherein the thickness is in the range of 10 to 30 μm and the in-plane and thickness direction retardation is 5 nm or less in absolute value.
(4) The optical film according to any one of (1) to (3), wherein the thermoplastic resin A is at least one selected from an acrylic resin, an olefin resin, and a polycarbonate resin.
(5) The molten thermoplastic resin A to which the second component B is added is discharged from the die onto a cast roll in a sheet form and cooled and solidified to obtain a thermoplastic resin sheet. When producing a film, before adding the second component B to the thermoplastic resin A, filter with a filter of 10 μm or less in absolute filtration accuracy, or filter with a filter of 5 μm or less with 95% cut in filtration accuracy (1) The manufacturing method of the optical film in any one of (4).
(6) The molten thermoplastic resin A to which the second component B is added is discharged from the die onto a cast roll in a sheet form and cooled and solidified to obtain a thermoplastic resin sheet. When producing a film, the thermoplastic resin A to which the second component B is added is filtered with a filter of 10 μm cut or less with absolute filtration accuracy, or filtered with a filter of 5 μm or less with 95% cut with filtration accuracy (1 )-(4) The manufacturing method of the optical film in any one.

  As will be described below, according to the present invention, an optical film made of a thermoplastic resin having excellent mechanical strength such as toughness having high transparency and defect-free property and having few foreign object defects is obtained. And the optical film obtained by this invention is suitable for uses, such as an optical disc, a display member, an optical lens, and a light-guide plate for liquid crystal backlights, making use of excellent heat resistance, transparency, and thickness accuracy.

  The optical film of the present invention can use various thermoplastic resins, particularly polycarbonate resin, polyolefin resin, cyclic polyolefin resin, polyacrylic resin, etc. as a constituent component, and in particular, a polymer having a cyclic structure, for example, cyclic polyolefin resin. As a cyclic norbornene resin or a resin containing a cyclopentane structure, while acrylic resins include polymethacrylic acid resins, polymethyl methacrylate resins and other polymethacrylic ester resins and their derivatives, and glutaric anhydride. , Glutarimide, maleic anhydride, lactone ring, and the like, and copolymers having these cyclic structures.

In the optical film of the present invention, the component content having a boiling point of 100 ° C. or less needs to be less than 0.5% by mass. That is, if such a low boiling component is contained, it causes a decrease in the intermolecular force of the polymer of the resin, resulting in a decrease in mechanical properties and heat resistance, and also the low boiling component in long-term storage. This is because the occurrence of swell and the accompanying adhesive degradation occurs, or so-called “blocking” occurs in which the film adheres to the film when it is rolled. The amount of the low boiling point is preferably as low as possible, and is practically preferably 100 ppm or less. The amount of low-boiling substances is determined by the following evaluation method. Using a thermal mass measuring device, the thermal loss of the thermoplastic resin film is measured in a nitrogen atmosphere under the condition of a temperature rising rate of 10 ° C./min, and obtained from the mass at 35 ° C. and 100 ° C. by the following formula.
Residual volatile matter (parts by mass) of the thermoplastic resin film = ((mass at 35 ° C.−mass at 100 ° C.) / Mass at 35 ° C.) × 100.

The optical film of the present invention is preferably free from the above-mentioned low boiling substances, and is preferably a melt film forming method from the viewpoint of cost and productivity. The melt film forming method can be classified into a straight die method, a cross head die method, a flat die method, and a special die method according to the shape of the die used. For the verification of the thermoplastic resin film of the present invention, a flat die method is used. Do the membrane. Resin melted by a melt extrusion apparatus or the like is measured by a gear pump and then continuously sent to a die. The die has only to be designed so that the molten resin does not stay therein, and any type of commonly used manifold die, coat hanger die, and fish tail die may be used in the flat die method. The molten resin extruded from the die into a sheet can be cooled and solidified on a cooling medium such as a drum to obtain a film. In melt film formation by the flat die method, a predetermined film thickness can be obtained by adjusting the extrusion temperature, the take-up speed during take-up, and the lip gap of the die. For the melt film forming method, an extruder type melt extruder equipped with a single screw or a twin screw can be used. The L / D of the screw is preferably 25 to 120 in order to prevent coloring. The melt extrusion temperature is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. The melt shear rate is preferably 1,000 sec ⁻¹ or more and 5,000 sec ⁻¹ or less. Moreover, when melt-kneading using a melt-extrusion apparatus, it is preferable to perform melt-kneading under a reduced pressure using a vent or nitrogen stream from a viewpoint of coloring suppression.

  The glass transition temperature (Tg) of the optical film of the present invention is 120 ° C. or higher, and particularly preferably 150 ° C. or higher in view of heat resistance. In addition, although the upper limit of glass transition temperature is not specifically limited, Usually, it is about 170 degreeC.

The thermoplastic resin A used in the present invention preferably has a melt viscosity of 6,000 to 100,000 poise (600 to 1,000 Pa · s) at a temperature of 260 ° C. and a shear rate of 12 sec ⁻¹ . If the melt viscosity at 260 ° C. and 12 sec ⁻¹ is less than 6,000 poise, the mechanical strength such as toughness is insufficient when formed into a film, and therefore breakage occurs during film production or when processed as a product. Tend. In addition, when it exceeds 100,000 poise, since it has a high viscosity, high-accuracy filtration with a filter is impossible, and it is very difficult to improve the foreign matter defect. The melt viscosity at 260 ° C. and 12 sec ⁻¹ is preferably in the range of 10,000 to 70,000 poise, and more preferably in the range of 15,000 to 70,000 poise. In order to set the melt viscosity of the thermoplastic resin A within the above range, the mass average molecular weight of the resin (copolymer) is set within the range of 70,000 to 150,000, and / or various fillers are added. realizable. There is no restriction | limiting in particular about the molecular weight control method, For example, a conventionally well-known technique is applicable. For example, in the case of acrylic resins, the addition amount of radical polymerization initiators such as azo compounds and peroxides, or chain transfer of alkyl mercaptans, carbon tetrachloride, carbon tetrabromide, dimethylacetamide, dimethylformamide, triethylamine, etc. It can be controlled by the amount of the agent added. In particular, a method of controlling the amount of alkyl mercaptan added as a chain transfer agent can be preferably used from the viewpoint of stability of polymerization, ease of handling, and the like. Resin melted by a melt extrusion apparatus or the like is measured by a gear pump and then continuously sent to a die. The die has only to be designed so that the molten resin does not stay therein, and any type of commonly used manifold die, coat hanger die, and fish tail die may be used in the flat die method. The molten resin extruded from the die into a sheet can be cooled and solidified on a cooling medium such as a drum to obtain a film. In melt film formation by the flat die method, a predetermined film thickness can be obtained by adjusting the extrusion temperature, the take-up speed during take-up, and the lip gap of the die.

  The optical film of the present invention preferably has a thickness in the range of 10 to 100 μm. The film thickness should be adjusted as appropriate depending on the film properties, handling properties, target final thickness, etc., but if the film thickness is less than 10 μm, the yield may be deteriorated, such as tearing is likely to occur during film formation. When the thickness exceeds 100 μm, the transparency is lowered or the thickness of the member becomes too large. The thickness of the optical film is more preferably in the range of 10 to 80 μm, and more preferably in the range of 10 to 30 μm from the recent trend of thinning the display.

  In the optical film of the present invention, the retardation in the thickness direction and the plane direction with respect to a light beam having a wavelength of 590 nm is preferably 5 nm or less as an absolute value, and more preferably 2 nm or less. When the retardation in the thickness direction and the plane direction with respect to a light beam having a wavelength of 590 nm is 5 nm or less, it can be suitably used in applications requiring optical isotropy, such as a polarizing plate and a protective film for an optical disk. In order to obtain such a low retardation thermoplastic resin film, it is effective not to introduce an additive or a copolymer component that exhibits a retardation. In applications where optical isotropy is required, the absolute values of the in-plane retardation and thickness direction retardation are preferably small, but the lower limit is considered to be about 0.1 nm in practice. In order to obtain such an optically isotropic thermoplastic resin film, as described above, the resin contains an alicyclic structure such as a glutaric anhydride structure, a lactone ring structure, a norbornene structure, or a cyclopentane structure. It is most preferable, and it is effective not to introduce an additive or a copolymerization component that develops a phase difference, or to reduce the draw ratio during film formation.

  The optical film of the present invention has a haze of 1.0% or less, preferably 0.6% or less. That is, if the film has a haze exceeding 1.0%, it gives a cloudy impression, is unsatisfactory in appearance, leaks light due to light scattering, and is not used in a liquid crystal display. In order to reduce the haze value of the optical film to 1.0% or less, (1) to lower the extrusion temperature, (2) to shorten the extrusion residence time, as far as possible in carrying out the film formation, (3 ) Narrow the lip gap of the die, (4) Decrease the ratio of the average film thickness to the lip gap of the die, or (5) In the flow path of the thermoplastic resin, the part deteriorated on the wall surface is diverted to the film edge. It is effective to employ means, (6) means for dynamically or statically stirring the deteriorated portion on the wall surface.

  The optical film of the present invention preferably has a b value, which is an index of color tone, of 1.0 or less. For this purpose, it is effective to (1) lower the extrusion temperature and (2) shorten the extrusion residence time as far as possible in film formation.

  The optical film of the present invention preferably has a long dimension of 1,000 mm or more, and more preferably 1,000 mm or more in all directions, from the recent trend of increasing the screen size of displays. As a result, the film of the present invention can be applied to a large-screen display whose vertical and horizontal dimensions exceed 1,000 mm.

  The optical film of the present invention is excellent in heat resistance, transparency, and optical properties, but by adding 5 to 40% by mass of a second component B made of a polymer, for example, elastomer particles, to the thermoplastic resin A of the present invention. Improve impact strength dramatically. By selecting an elastomer particle having a small difference in refractive index from the copolymer used in the present invention, it is possible to improve impact resistance and elongation at break while maintaining transparency. When such elastomer particles are added, the content thereof can be appropriately selected in light of each application, but usually it is preferably contained in the range of 5 to 40% by mass in the optical film. Thus, by containing elastomer particles, it becomes possible to make the breaking elongation of the optical film excellent in handling such that it is in the range of 30 to 70% in an arbitrary direction. That is, if the elongation at break is less than 30%, it will break during handling, while if it exceeds 70%, it will be too flexible and will be used in applications and processes. It is because it may be limited to the thing which does not start. Such an elastomer particle preferably has a mass average particle diameter of 50 to 400 nm, more preferably 100 to 200 nm. When the mass average particle diameter is less than 50 nm, the toughness may not be sufficiently improved, and when it exceeds 400 nm, the Tg may decrease. In addition, the mass average particle diameter of the elastomer particles is a sodium alginate method described in “Rubber Age, Vol. 88, p. 484-490 (1960), by E. Schmidt, PH B. Biddison”, that is, sodium alginate. Utilizing the fact that the diameter of the polybutadiene to be creamed differs depending on the concentration, it can be measured by a method of obtaining a particle size of 50% cumulative mass fraction from the mass proportion creamed and the cumulative mass fraction of sodium alginate concentration. Alternatively, a core-shell structure having an elastomer component as a core and a shell layer having the same or affinity as the first component thermoplastic resin may be used. The mass ratio of the core and the shell is not particularly limited, but the core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more, with respect to 100 parts by mass as a whole. More preferably, it is 80 parts by mass or less. As the second component B made of the polymer of the present invention, a commercially available product that satisfies the above-described conditions may be used, or it may be prepared by a known method. For example, commercially available products include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paraloid” manufactured by Kureha Chemical Co., Ltd., “Acryloid” manufactured by Rohm and Haas Co. “Staffyroid” and “Parapet SA” manufactured by Kuraray Co., Ltd. may be mentioned, and these may be used alone or in combination of two or more. As a method for adding the second component B to the first component thermoplastic resin A, for example, after pre-blending the second component B to the first component thermoplastic resin A, usually at 200 to 350 ° C., A method of uniformly melting and kneading with a single screw or twin screw extruder can be used.

The optical film of the present invention preferably has a foreign matter defect having a size of 20 μm or more of less than 20 pieces / m ² . That is, when a thermoplastic resin film is used for optical applications, it is preferable that it is defect-free. In addition to the above foreign matter in the alkali resin solution, defects may occur in the coating and drying processes. Therefore, the drying conditions are optimized, and the number of bubble defects having a maximum diameter of 20 μm or more per 1 m ^{2 of} film. Is preferably 10 pieces / m ² or less, more preferably 5 pieces / m ² or less, and further preferably 2 pieces / m ² or less.

  In addition, in order to achieve the above defect-free property, the optical film of the present invention, when adding the second component B to the thermoplastic resin A, the polymer of the second component B with absolute filtration accuracy before the addition. Filter through a 10 μm or smaller filter. In other words, the elastomer component forms coarse particles called “coagulum” in its production process, which contributes to the defect of foreign matter. However, since the elastomer component is soft, it passes through the filter under high pressure, and is kneaded once. After that, it is virtually impossible to remove the coarse particles. Therefore, it is necessary to filter with a filter of 10 μm or less in absolute filtration accuracy in a state before kneading, for example, in a slurry state. The absolute filtration accuracy is preferably as small as possible, but the target elastomer particles themselves may be thinned, and the absolute filtration accuracy is preferably in the range of 1 to 5 μm.

  In order to remove other foreign substances, it is preferable to filter the molten thermoplastic resin A with a metal fiber sintered type, metal powder sintered type or metal wire mesh type filter, or a combination filter thereof. Is a high-precision filter with a filtration accuracy of 95% cut and 5 μm cut or less, and more preferably a high-precision filter with 3 μm cut or less.

  Further, the optical film of the present invention includes hindered phenol, benzotriazole, benzophenone, benzoate and cyanoacrylate UV absorbers and antioxidants, higher fatty acids, acid esters and acid amides, and higher alcohols. Lubricants and plasticizers such as, montanic acid and salts thereof, esters thereof, half esters thereof, release agents such as stearyl alcohol, stellar amide and ethylene wax, anti-coloring agents such as phosphites and hypophosphites, Contains additives such as halogen flame retardants, phosphorous and silicone non-halogen flame retardants, nucleating agents, amine-based, sulfonic acid-based, polyether-based antistatic agents, pigments and other colorants Good. When these additives are added, the content can be appropriately selected in light of each application.

  The optical film of the present invention is provided with an antistatic layer or an easy-adhesion layer by coating on the surface depending on the purpose of use, a hard coat layer made of an ultraviolet curable resin, a triangular prism layer, a microlens array, or the like, or a metal or metal oxide It is possible to use a laminated layer with other optically isotropic films, optical films such as polarizers, retardation films, etc., glass substrates, etc. via an adhesive layer. it can.

Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not necessarily limited to the following examples. Prior to describing each example, a method for measuring various physical properties will be described.
(1) Gel permeation chromatograph (pump: 515 type, manufactured by Waers, column: TSK-) equipped with a DAWN-DSP type multi-angle light scattering photometer (manufactured by Wyatt Technology) using dimethylformamide as a mass average molecular weight gel-GMHXL, manufactured by Tosoh Corporation).

(2) Melt viscosity thermoplastic resin pellets were pre-dried at 80 ° C. for 12 hours, and measured at a temperature of 260 ° C. and a shear rate of 12 sec ⁻¹ using a Toyo Seiki Capillograph Type 1C (die diameter φ1 mm, die length 5 mm). did.

(3) Glass transition temperature (Tg)
About 5 mg of a sample is taken and measured with a differential scanning calorimeter (Seiko Denshi Kogyo RDC220 type) in a nitrogen atmosphere in the range of 25 ° C. to 200 ° C. at a rate of temperature increase of 20 ° C./min. It was determined based on the measurement results. The glass transition temperature is determined by equidistant from the extended straight line of each baseline of the measurement chart to the vertical axis according to the method for determining the midpoint glass transition temperature in 9.3 of JIS-K-7121 (1987). The temperature was the point at which a straight line and the curve of the step-like change part of the glass transition intersect.

(4) Elongation at break of film It was measured under the following conditions using an automatic film strength measuring device “Tensilon AMF / RTA-100” manufactured by Orientec Co., Ltd.
Sample size: width 10mm, length 150mm
Chuck distance 50mm
Tensile speed: 300 mm / min Measurement environment: 23 ° C., 65% RH, film length under atmospheric pressure, which is obtained by dividing the distance between chucks by the distance between chucks, multiplied by 100 to obtain the elongation at break. did. The measurement was performed 5 times and the average value was taken.

(5) Haze of film It measured using the haze meter (made by Suga Test Instruments) according to JIS-K-6714 (1995).

(6) In-plane retardation and thickness direction retardation measurement of the film Elliptical polarization measuring device (KOBRA-WPR) and retardation measuring device KOBRA-RE (software for KOBRA-WR) Ver. 1.21 was used. Measurement is performed in a single N calculation mode of incident angle dependence measurement, using a low phase difference measurement method, with the slow axis as the tilted central axis and an incident angle of 40 ° (wavelength 590 nm). A phase difference (Δnd) and a thickness direction retardation (Rth) were obtained. The R0 value, which is the phase difference at an incident angle of 0 °, was defined as the in-plane phase difference (Δnd). Further, the measurement was performed on a sample stored for 24 hours in a desiccator, and the average value of N = 5 times was defined as an in-plane retardation (Δnd) and a thickness direction retardation (Rth).

(7) Based on film color tone JIS-Z-8722 (2000), using a spectroscopic color difference meter (SE-2000 manufactured by Nippon Denshoku Industries Co., Ltd., light source halogen lamp 12V4A, 0 ° to −45 ° post spectral method) The color tone (b value) of each film was measured by the transmission method. The measurement was performed in an atmosphere at a temperature of 23 ° C. and a relative humidity of 65%. Measurement was carried out by selecting five arbitrary positions on the film, and the average value was adopted.

(8) A foreign matter defect inspection film sample is laid on a 1 m ² black sheet, and a film appearance defect inspection is performed visually with the reflected light of one fluorescent lamp in a dark room. The found appearance defects are all classified and checked with a microscope or the like, and among them, the number of foreign matter defects in the film having a maximum diameter of 20 μm or more is counted for the foreign matter present inside the film. In the case where the measurement area is less than 1 m ^2, after the observation and classification, in terms of the per appropriate 1 m ^2.

(9) Measurement of the amount of low-boiling substances Using a thermal mass measuring device (TGA-50H) manufactured by Shimadzu Corporation and an analyzer thermal analyzer (TA-50) in combination with a personal computer for data processing And measured. About 7 mg of the film was set in a furnace, the inside of the furnace was placed in a nitrogen atmosphere, and the film was heated from room temperature to 100 ° C. at a temperature rising rate of 10 ° C./min. The low boiling point amount of the film was determined from the obtained thermal mass curve by the following formula. The measurement was performed twice per sample, and the average value was used as the low boiling point amount. The measurement was performed once.
Residual volatile matter (parts by mass) of the thermoplastic resin film = ((mass at 35 ° C.−mass at 100 ° C.) / Mass at 35 ° C.) × 100.

(Examples 1-5, Comparative Examples 1-3)
(1) The production capacity of the copolymer (A-1) containing glutaric anhydride units is 20 liters, and a stainless steel autoclave equipped with a baffle and a foudra-type stirring blade is used as a suspending agent, methyl acrylate / acrylamide. Copolymer (mass ratio 20/80, described in Example 1 of Japanese Examined Patent Publication No. 45-24151) A solution obtained by dissolving 0.05 part by mass in 165 parts of ion-exchanged water was stirred at 400 rpm, and the system was replaced with nitrogen gas. did. Next, a reaction system of the following mixed substances was added with stirring, and the temperature was raised to 60 ° C. to initiate suspension polymerization.
Methacrylic acid 20 parts by weight Methyl methacrylate 80 parts by weight t-dodecyl mercaptan (chain transfer agent) 0.3 parts by weight 2,2′-azobisisobutyronitrile (polymerization initiator) 0.4 parts by weight over 15 minutes After raising the reaction temperature to 65 ° C, the temperature was raised to 100 ° C over 50 minutes. Thereafter, the reaction system was cooled, the polymer was separated, washed, and dried in accordance with ordinary methods to obtain a bead-shaped vinyl copolymer (prepolymer (A-1-0)).

This bead-like vinyl copolymer (A-1-0) is supplied from the hopper port of a vented co-rotating twin-screw extruder (PCM-30 manufactured by Ikekai Tekko) with a screw diameter of 30 mm and an L / D of 25. Then, it was melt-extruded at a resin temperature of 250 ° C. and a screw rotation speed of 100 rpm to obtain a copolymer (A-1) containing pellet-like glutaric anhydride units. It was 141 degreeC as a result of measuring the glass transition temperature (Tg) by DSC about obtained (A-1). ^{The 1} H-NMR spectrum was measured, and the spectrum was assigned with a peak of 0 to 0.8 ppm. The hydrogen of the α-methyl group of methacrylic acid, methyl methacrylate and glutaric anhydride ring compounds, 0.8 to 1.6 ppm. The peak of is the water of the methylene group of the polymer main chain, the peak of 3.0 ppm is the hydrogen of the carboxylic acid ester of methyl methacrylate (—COOCH ₃ ), and the peak of 11.9 ppm is the hydrogen of the carboxylic acid of methacrylic acid. As a result of calculating the composition of each copolymer unit from the integral ratio of the spectrum, it was as follows.
Methacrylic acid unit: 1.3% by mass
Methyl methacrylate unit: 81.0% by mass
Glutaric anhydride unit: 17.7% by mass.

(2) Preparation of copolymer (A-2) containing glutar anhydride units (A-1-0) In the same manner, the monomer composition was changed to 30 parts by weight of methacrylic acid and 70 parts by weight of methyl methacrylate. Thus, a bead-shaped vinyl polymer (A-2-0) was obtained. This vinyl copolymer was melt-kneaded by the same method to obtain a copolymer (A-2) containing pellet-like glutaric anhydride units. The Tg of this (A-2) was 155 ° C. The composition of each copolymer unit calculated from the integration ratio of the ¹ H-NMR spectrum was as follows.
Methacrylic acid unit: 0.1% by mass
Methyl methacrylate unit: 69.8% by mass
Glutaric anhydride unit: 30.1% by mass.

(3) Manufacturing method of elastomer particle (B) The core-shell polymer obtained by the following was used.
A nitrogen container is charged with 120 parts by mass of deionized water, 0.5 parts by mass of potassium carbonate, 0.5 parts by mass of dioctyl sulfosuccinate, and 0.005 parts by mass of potassium persulfate in a glass container with a condenser (capacity 5 liters). After stirring under, 53 parts by mass of butyl acrylate, 17 parts by mass of styrene, and 1 part by mass of allyl methacrylate (crosslinking agent) were charged. These mixtures were reacted at 70 ° C. for 30 minutes to obtain a core layer polymer. Next, a mixture of 21 parts by weight of methyl methacrylate, 9 parts by weight of methacrylic acid, and 0.005 parts by weight of potassium persulfate was continuously added over 90 minutes, and further maintained for 90 minutes to polymerize the shell layer. The polymer latex was coagulated with sulfuric acid and neutralized with caustic soda, washed, filtered and dried to obtain acrylic elastic particles (B) having a two-layer structure. The average particle diameter of the polymer particles measured with an electron microscope was 155 nm.

(4) Kneading method of thermoplastic resins (A-1, A-2) and elastomer particles (B) Screw rotation speed using a twin screw extruder (TEX30 (manufactured by Nippon Steel Co., Ltd., L / D = 44.5)) Kneading was performed at 150 rpm and a cylinder temperature of 280 ° C. to obtain a pellet-shaped resin.

(5) Film formation (Example 1)
The thermoplastic resin composition (A-1-1) having a mass average molecular weight of 100,000, and elastomer particles (B) filtered with a 3 μm cut filter with absolute filtration accuracy in a slurry after neutralization before kneading ) Was dried under reduced pressure at 80 ° C. for 8 hours, and then extruded at 260 ° C. using a vented φ65 mm uniaxial extruder, and the discharge rate was made constant with a gear pump, and then a metal fiber sintered type 5 μm cut filter was used. The sheet is provided through a flat die (set temperature 260 ° C.) with a lip gap of 0.6 mm, and a flow dividing means is provided immediately before the die, the ratio of the divided flow rate of the resin between the wall surface and the central portion is 15/85% by mass. It was made to discharge in the shape. The thermoplastic resin sheet is discharged from the lip in the vertical direction, and is cooled by embracing it in a tangential direction with a stainless steel cooling roll (110 ° C .: conveyance speed 20 m / min) having a surface finish of 0.2 mm with a diameter of 350 mm, Subsequently, it was conveyed and cooled by a roll of the same diameter and the same material. At that time, the distance between the lip to the sheet and the contact point of the cast roll is 125 mm, and a heating stainless steel roll (110 ° C .: driving speed 10 m / min, rectifying roll) having a diameter of 350 mm is placed on the front surface of the cast roll. Heating was performed while the distance from the contact point was close to 5 mm. Thereafter, the end of the sheet was cut to obtain a thermoplastic resin film having a thickness of 40 μm. The film had few defects, was excellent in transparency, had a break elongation that could withstand handling, and was excellent in optical use. Further, when the film roll was confirmed after being stored in an environment of 60 ° C.-90% RH for 72 hours, blocking between the films did not occur.

(Examples 2 to 8)
Mass average molecular weight, thermoplastic resin composition, elastomer particle size and addition amount, absolute filtration accuracy of filter before kneading of elastomer particles, filtration accuracy at 95% cut of filter during extrusion after mixing, The thermoplastic resin films shown in Tables 1 and 2 were obtained in the same manner as in Example 1 except that the film thickness was changed.

(Comparative Example 1)
In Example 1, a thermoplastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that filtration was not performed before kneading the elastomer particles. The film had many drawbacks and was not suitable for an optical film.

(Comparative Examples 2 and 3)
In Example 1, the thickness is the same as in Example 1 except that the absolute filtration accuracy of the filter before kneading the elastomer particles and the filtration accuracy at 95% cut of the filter at the time of extrusion after mixing are changed. A 40 μm thermoplastic resin film was obtained.

(Comparative Example 4)
In Example 1, a thermoplastic resin film was obtained in the same manner as in Example 1 except that the elastomer particles were not added. Although there were few defects, the handling property was low and the elongation at break was poor.

(Comparative Example 5)
In Example 1, a thermoplastic resin film was obtained in the same manner as in Example 1 except that the elastomer particles were not added, and the filtration accuracy at 95% cut of the filter at the time of extrusion after mixing was changed. . There were also many drawbacks, and the handling property was low with a low elongation at break.

(Comparative Example 6)
In Example 1, a thermoplastic resin film was obtained in the same manner as in Example 1 except that the addition amount of the elastomer particles was 45% by mass. It was not suitable for optical applications with many defects.

(Comparative Example 7)
The thermoplastic resin composition (A-1-1) having a mass average molecular weight of 100,000, and elastomer particles (B) filtered with a 3 μm cut filter with absolute filtration accuracy in a slurry after neutralization before kneading ) Was obtained. This pellet is dissolved in a methyl ethyl ketone solvent, and a resin concentration of 25 parts by mass is filtered through a 1 μm cut filter. This resin solution is applied to a polyethylene terephthalate film and dried at a step temperature increase from 60 ° C. to 145 ° C. A film having a residual amount of methyl ethyl ketone of 5.2% by mass was obtained. After this acrylic resin film was stored for 490 hours, it was re-dried at a stepwise temperature increase from 148 ° C. to 176 ° C. to obtain a film having a thickness of 40 μm with a residual amount of methyl ethyl ketone of 1.5% by mass. The film itself had few defects and excellent transparency, and the elongation at break could withstand handling, and was excellent for optical use. However, when the film roll was peeled off from the polyethylene terephthalate film and re-rolled and stored for 72 hours in an environment of 60 ° C.-90% RH, the film was partially stuck between the films and blocked. I was waking up.
The evaluation results of each thermoplastic resin film are shown in Table 1.

  From the above examples and comparative examples, the following is clear. In the present invention, a film with few foreign matter defects is obtained. As described above, since the optical film of the present invention is excellent in transparency, heat resistance, and defect-free properties, it can be suitably used as a material for optical disks, display members, optical lenses, and light guide plates for liquid crystal backlights.

  The film of the present invention has few foreign substance defects, is excellent in retardation accuracy, and is excellent in handling properties. Therefore, it can be suitably used as a material for optical disks, display members, optical lenses, and light guide plates for liquid crystal backlights. .

Claims (6)

A thermoplastic resin A having a cyclic structure in which the glass transition temperature is 120 ° C. or higher, the melt viscosity at a temperature of 260 ° C. and a shear rate of 12 sec ^{−1 is} in the range of 6,000 to 100,000 poise, is used as a constituent component, and The second component B is contained in the range of 5 to 40% by mass, the haze value is 1% or less, the b value is 1 or less, the thickness is 10 to 100 μm, and the boiling point is 100 ° C. or less. Is less than 0.5% by mass, and the number of foreign matter defects having a size of 20 μm or more is less than 20 / m ² . The optical film according to claim 1, wherein the second component B is an elastomer particle. The optical film according to claim 1 or 2, wherein the thickness is in the range of 10 to 30 µm, and the in-plane and thickness direction retardations are 5 nm or less in absolute value. The optical film according to claim 1, wherein the thermoplastic resin A is at least one selected from an acrylic resin, an olefin resin, or a polycarbonate resin. The molten thermoplastic resin A, to which the second component B has been added, is discharged from the die onto a cast roll in a sheet form and cooled and solidified to form a thermoplastic resin sheet. The thermoplastic resin sheet is heat-treated to produce an optical film. In this case, before adding the second component B to the thermoplastic resin A, it is filtered with a filter of 10 μm or less in absolute filtration accuracy, or is filtered with a filter of 5 μm or less with 95% cut in filtration accuracy. 4. The method for producing an optical film according to any one of 4 above. The molten thermoplastic resin A, to which the second component B has been added, is discharged from the die onto a cast roll in a sheet form and cooled and solidified to form a thermoplastic resin sheet. The thermoplastic resin sheet is heat-treated to produce an optical film. In doing so, the thermoplastic resin A to which the second component B is added is filtered with a filter of 10 μm cut or less with absolute filtration accuracy, or is filtered with a filter of 5 μm or less with 95% cut with filtration accuracy. The manufacturing method of the optical film in any one.