JP2010069676A - Method of manufacturing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical film excelling in optical characteristics with few spot-like defects. <P>SOLUTION: The method of manufacturing the optical film for forming a film of amorphous thermoplastic resin by a melt-extrusion method using a single screw extruder having a mechanism controlling temperature respectively at a resin supply part screw and a resin measuring part screw, satisfies (1) the temperature of the resin supply part screw A in the single screw extruder is a glass transition temperature -70°C or higher and the glass transition temperature +10°C or lower, and (2) the temperature of the resin measuring part screw C is the glass transition temperature -30°C or higher and the glass transition temperature +50°C or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an optical film which is excellent in optical properties such as transparency and has few appearance defects.

  2. Description of the Related Art In recent years, electronic devices have become increasingly smaller, and liquid crystal display devices that take advantage of the features of light weight and compactness, such as notebook personal computers, mobile phones, and portable information terminals, have been increasingly used. These liquid crystal display devices start with a polarizing film, and various films are used to maintain the display quality. Also, a plastic liquid crystal display device using a resin film instead of a glass substrate has been put into practical use for the purpose of further reducing the weight of the liquid crystal display device for portable information terminals and mobile phones.

  In the case of handling polarized light as in a liquid crystal display device, the resin film used is optically transparent, optically homogeneous, less colored or discolored, and has a dotted or streaky appearance. It is required that there are few defects.

  Examples of the film forming method include a solution casting film forming method and a melt extrusion method. However, in recent years, the melt extrusion method has attracted attention due to environmental problems caused by equipment costs, productivity, and solvent. Yes.

  However, when a film is formed by the melt extrusion method, the resin charged in the extruder is deteriorated due to heat generation of the resin due to shear stress in the extruder, and the film is colored or discolored, or the resin is crosslinked. There is a problem that a point defect occurs.

  Furthermore, if the extrusion amount is unstable, the resin deteriorates in the extruder, and the film is colored or discolored, or unmelted due to kneading failure in the extruder, or brown or black spots due to burnt resin There is a problem that defects in the shape occur.

  Generally, various types of filters are used for the purpose of removing foreign substances. However, it is difficult to completely remove very small foreign substances with the cause of point defects such as the above unmelted material and brown burnt resin. There is.

On the other hand, Patent Document 1 discloses a method for producing an optical film in which the screw temperature in the entire length is controlled at a time in order to suppress cross-linking of the resin in the extruder. In such a method, it is difficult to control the temperature in each part of the screw, and it has been impossible to achieve both suppression of resin heat generation due to shear stress in the extruder and extrusion stability.
JP 2006-327110 A

  The present invention has been made to solve the above-described problems, and provides a method for producing an optical film having few point defects and excellent optical characteristics.

  In order to solve the above problems, the present inventors have conducted intensive studies. As a result, in the method for producing an optical film for forming an amorphous thermoplastic resin by a melt extrusion method using a single screw extruder, the screw temperature of the resin supply section in the single screw extruder, and the resin metering The inventors have found that the above-mentioned problems can be solved by controlling the internal screw temperature within a certain range, and have completed the present invention.

  That is, according to the present invention, the following method for producing an optical film is provided.

(I) A method for producing an optical film in which an amorphous thermoplastic resin is formed by a melt extrusion method using a single-screw extruder having a temperature controllable mechanism with a resin supply unit screw and a resin metering unit screw. And (2) satisfying the following (1) and (2).
(1) Resin supply section screw temperature in the single screw extruder is glass transition temperature −70 ° C. or higher and glass transition temperature + 10 ° C. or lower (2) Resin metering section screw temperature is glass transition temperature −30 ° C. or higher and glass transition temperature +50 Below ℃.

  (Ii) The method for producing an optical film as described in (i), wherein the amorphous thermoplastic resin is an acrylic resin.

  (Iii) An imide resin in which the acrylic resin has a unit represented by the following general formula (1), a unit represented by the following general formula (2) and / or a unit represented by the following general formula (3) (I) or the manufacturing method of the optical film as described in (ii) characterized by the above-mentioned.

（但し、Ｒ１及びＲ２は、それぞれ独立に、水素又は炭素数１〜８のアルキル基を示し、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を示す。）

(However, R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or the number of carbon atoms. The substituent containing a 5-15 aromatic ring is shown.)

（但し、Ｒ４及びＲ５は、それぞれ独立に、水素又は炭素数１〜８のアルキル基を示し、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を示す。）

(However, R4 and R5 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a carbon number. The substituent containing a 5-15 aromatic ring is shown.)

（但し、Ｒ７は、水素又は炭素数１〜８のアルキル基を示し、Ｒ８は、炭素数６〜１０のアリール基を示す。）

(However, R7 represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 represents an aryl group having 6 to 10 carbon atoms.)

  According to the present invention, in the method for producing an optical film for forming an amorphous thermoplastic resin by a melt extrusion method using a single screw extruder, the resin supply part screw temperature in the single screw extruder, Further, by controlling the resin measuring section screw temperature within a certain range, it is possible to provide a method for producing an optical film having few point defects and excellent optical characteristics. Moreover, the optical film formed by this method can satisfy the small number of point-like defects required for an optical film used in a liquid crystal display device or the like.

The method for producing an optical film according to the present invention is based on a melt extrusion method using a single-screw extruder having a mechanism capable of controlling the temperature of an amorphous thermoplastic resin with a resin supply screw and a resin metering screw. In the method for producing an optical film to be formed, the following (1) and (2) are satisfied.
(1) Resin supply section screw temperature in the single screw extruder is glass transition temperature −70 ° C. or higher and glass transition temperature + 10 ° C. or lower (2) Resin metering section screw temperature is glass transition temperature −30 ° C. or higher and glass transition temperature +50 ℃ or less

  An example of a screw of a single screw extruder used in the method for producing an optical film according to the present invention is shown in FIG. Here, the screw used in the present invention is not limited to such a specific example. A screw 1 shown in FIG. 1 includes a supply unit A, a compression unit B, and a measuring unit C. Specifically, the raw material resin is stably supplied to the compression unit B by the supply unit A, and is uniformly melt-kneaded by the compression unit B and the measurement unit C.

  More specifically, the raw material resin is propelled by the frictional difference between the resin on the surface of the extruder cylinder 2a and the surface of the screw supply part A, and is supplied to the compression part B. As a result, the extruder cylinder temperature in the screw supply section and the screw supply section temperature have a great influence on the extrusion amount stability, and the extrusion amount fluctuation is large depending on the above-mentioned extruder cylinder temperature and screw supply section temperature conditions. As a result, an unmelted product is generated, and as a result, point-like defects are generated, which may be undesirable.

  In addition, the stably supplied raw material resin is uniformly kneaded by the compression unit B and the metering unit C. Here, in particular, the resin is cross-linked by an excessive shear stress of the screw metering section C and a point defect is generated, which is not preferable.

  In contrast, the present invention is characterized in that the temperature in each part of the screw is controlled.

  Specifically, if the resin supply screw temperature is less than the glass transition temperature of −70 ° C., it greatly affects the extruder cylinder temperature control, causing variations in the extruder internal temperature and increasing the amount of extrusion, which is not preferable. Accordingly, the resin supply part screw temperature in the single screw extruder when forming a film by the melt extrusion method using a single screw extruder is preferably a glass transition temperature of −70 ° C. or more, more preferably a glass transition temperature. It is −60 ° C. or higher, particularly preferably the glass transition temperature is −50 ° C. or higher.

  Moreover, when the resin supply part screw temperature is higher than the glass transition temperature + 10 ° C., the molten resin is wound around the screw resin supply part, and the amount of extrusion increases, which is not preferable. Therefore, the resin supply part screw temperature in the single screw extruder when forming a film by a melt extrusion method using a single screw extruder is preferably a glass transition temperature + 10 ° C. or less, more preferably a glass transition temperature or less. Particularly preferred is a glass transition temperature of −10 ° C. or lower.

  If the resin metering part screw temperature is less than the glass transition temperature of −30 ° C., it is preferable because excessive resin cooling hinders uniform kneading of the resin, resulting in variation in the viscosity of the resin in the extruder, and fluctuation in the amount of extrusion increases. Absent. Accordingly, the resin measuring section screw temperature in the single screw extruder when forming a film by melt extrusion using a single screw extruder is preferably a glass transition temperature of −30 ° C. or more, more preferably a glass transition temperature of −20 ° C. As described above, the glass transition temperature is preferably −10 ° C. or higher.

  Further, when the resin measuring section screw temperature is higher than the glass transition temperature + 50 ° C., the heat removal effect on the resin heat generation due to the shear stress in the extruder is small, and the resin crosslinks to generate point defects. Therefore, the resin metering section screw temperature in the single screw extruder when forming a film by the melt extrusion method using a single screw extruder is preferably a glass transition temperature + 50 ° C. or less, more preferably a glass transition temperature + 40 ° C. or less. Especially preferably, it is glass transition temperature +30 degrees C or less.

  In the method for producing an optical film according to the present invention, the cylinder temperature in each part of the extruder is appropriately adjusted within a range in which the above-described extrusion amount stability is ensured and resin crosslinking does not occur. Specifically, the preferable temperature of the cylinder corresponding to the screw supply unit is the glass transition temperature + 70 ° C., more preferably the glass transition temperature + 60 ° C. Moreover, the preferable temperature of the cylinder corresponding to a screw metering part is glass transition temperature +150 degreeC, More preferably, it is glass transition temperature +140 degreeC.

  The method for adjusting the screw temperature in the method for producing an optical film according to the present invention is not particularly limited, and the method for adjusting the cylinder temperature as described above, for example, heating oil or water is circulated inside the screw. The method of controlling the temperature and the method of controlling the temperature by installing an electric heater inside the screw are included, but the method of adjusting the cylinder temperature and heating oil or water are circulated inside the screw to control the temperature. It is preferable to combine these methods.

  The screw in the method for producing an optical film according to the present invention has a mechanism capable of controlling the temperature different between the resin supply unit screw and the resin metering unit screw. In the screw, it is not preferable to control the temperature of the resin supply unit, the resin compression unit, and the resin metering unit at the same time, because the amount of extrusion is changed.

  In addition to the full flight screw shown in FIG. 1, the screw in the method for producing an optical film of the present invention can be applied to a screw for an extruder with a vent, a screw with a mixing mechanism, a dam flight screw, and the like. Among these, from the viewpoint of uniform kneading properties of the resin, a screw with a mixing mechanism is preferable as the screw.

  Further, the material on the screw surface is not particularly limited, but from the viewpoint of cross-linking of the resin due to the resin staying on the screw surface, plating or ceramic coating treatment is preferably performed. Among these, the screw is preferably subjected to a plating treatment, and is preferably subjected to a chromium plating treatment.

  The molding method in the method for producing an optical film according to the present invention is not particularly limited as long as it can be molded by a melt extrusion method, and examples thereof include a T-die extrusion method and an inflation extrusion method.

  The amorphous thermoplastic resin used in the optical film according to the present invention is a polymer that maintains an amorphous state that cannot take on a crystal structure, and its glass transition temperature varies depending on the resin, and thus is particularly limited. Although it is not a thing, it is a thing 100 degreeC or more generally. Examples of the amorphous thermoplastic resin include polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin resin, cellulose resin, vinyl chloride resin, polysulfone resin, polyethersulfone resin, Examples thereof include a single resin such as a maleimide / olefin resin, a lactone resin, and a glutarimide resin, or a resin composition obtained by mixing these resins. Among these, in the present invention, acrylic resins such as polymethyl methacrylate resins, lactone resins, and imide resins are preferable, and imide resins are particularly preferable. Hereinafter, the imide resin will be described. (In the present invention, the acrylic resin refers to a polymer mainly composed of an acrylic monomer and a resin obtained by modifying and / or reacting them.)

  As the imide resin, an imide resin having a unit represented by the following general formula (1), a unit represented by the following general formula (2) and / or a unit represented by the following general formula (3) preferable.

（但し、Ｒ１及びＲ２は、それぞれ独立に、水素又は炭素数１〜８のアルキル基を示し、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を示す。）

(However, R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or the number of carbon atoms. The substituent containing a 5-15 aromatic ring is shown.)

（但し、Ｒ４及びＲ５は、それぞれ独立に、水素又は炭素数１〜８のアルキル基を示し、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を示す。）

(However, R4 and R5 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a carbon number. The substituent containing a 5-15 aromatic ring is shown.)

（但し、Ｒ７は、水素又は炭素数１〜８のアルキル基を示し、Ｒ８は、炭素数６〜１０のアリール基を示す。）

(However, R7 represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 represents an aryl group having 6 to 10 carbon atoms.)

  The first structural unit constituting the imide resin is represented by the general formula (1) and is generally called a glutarimide unit (hereinafter, the general formula (1) is often referred to as a glutarimide unit. And may be abbreviated.)

  As a preferred glutarimide unit, R1 and R2 are hydrogen or a methyl group, and R3 is hydrogen, a methyl group, a butyl group, or a cyclohexyl group. The case where R1 is a methyl group, R2 is hydrogen, and R3 is a methyl group is particularly preferable.

  The glutarimide unit may be a single type, or may include a plurality of types in which R1, R2, and R3 are different.

  The glutarimide unit can be formed by imidizing the second structural unit described below. In addition, acid anhydrides such as maleic anhydride, or half esters thereof with linear or branched alcohols having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride Further, α, β-ethylenically unsaturated carboxylic acids such as crotonic acid, fumaric acid and citraconic acid can be imidized and can be used to form glutarimide units.

  The second structural unit constituting the imide resin is represented by the general formula (2), and is generally called a (meth) acrylic acid ester unit (here, (meth) Acrylic acid ester refers to acrylic acid ester and methacrylic acid ester.Hereinafter, general formula (2) may be abbreviated as (meth) acrylic acid ester unit).

  When the imide resin is produced, first, a (meth) acrylic acid ester-aromatic vinyl copolymer or a (meth) acrylic acid ester polymer is polymerized and post-imidized to form, specifically, The raw material that gives the (meth) acrylic acid ester unit as a residue is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, Examples thereof include t-butyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate and the like. Of these, methyl methacrylate is particularly preferred.

  These second structural units may be of a single type or may include a plurality of types in which R4, R5, and R6 are different. Similarly, a plurality of types of raw materials that give the (meth) acrylic acid ester unit as a residue may be used.

  The third structural unit contained in the imide resin of the present invention as needed is represented by the general formula (3), and is generally called an aromatic vinyl unit (hereinafter referred to as the general formula). (3) may be abbreviated as an aromatic vinyl unit.

  Preferred aromatic vinyl structural units include styrene, α-methylstyrene, and the like. Of these, styrene is particularly preferred.

  These third structural units may be of a single type or may include a plurality of types in which R7 and R8 are different.

  The content of the glutarimide unit represented by the general formula (1) in the imide resin depends on, for example, the structure of R3, but is preferably 20% by weight or more of the imide resin. The preferable content of the glutarimide unit is 20% to 95% by weight, more preferably 40 to 90% by weight, and still more preferably 50 to 80% by weight. When the ratio of the glutarimide unit is smaller than this range, the resulting imide resin has insufficient heat resistance and transparency may be impaired. On the other hand, if it exceeds this range, the heat resistance and melt viscosity are unnecessarily increased, the molding processability is deteriorated, the mechanical strength of the resulting film becomes extremely brittle, and the transparency may be impaired.

  The content of the aromatic vinyl unit represented by the general formula (3) in the imide resin is preferably 1% by weight or more based on the total repeating unit of the imide resin. The content of the aromatic vinyl unit is preferably 1 to 40% by weight, more preferably 1 to 30% by weight, and still more preferably 1 to 25% by weight. When the aromatic vinyl unit is larger than this range, the resulting imide resin has insufficient heat resistance. If it is smaller than this range, the mechanical strength of the resulting film may be lowered.

  By adjusting the ratios of the general formulas (1), (2), and (3), it is possible to adjust various required physical properties. For example, when the imide resin is first formed by polymerizing a (meth) acrylic acid ester-aromatic vinyl copolymer such as methyl methacrylate-styrene copolymer and then imidizing, for example, (meth) acrylic acid ester and The ratio of the general formula (3) is determined by adjusting the polymerization ratio of the aromatic vinyl (the ratio of the general formula (3) can be set to 0), and further, the addition ratio of the primary amine during post-imidation is adjusted. By doing so, the ratio of the general formulas (1) and (2) can be further adjusted.

  If necessary, the imide resin of the present invention may further be copolymerized with a fourth structural unit. A constitution obtained by copolymerizing nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide as the fourth structural unit Units can be used. These may be directly copolymerized in a thermoplastic resin or may be graft copolymerized.

  When producing the imide resin of the present invention, first, a (meth) acrylic acid ester-aromatic vinyl copolymer such as methyl methacrylate-styrene copolymer or a (meth) acrylic acid ester weight such as methyl methacrylate polymer is used. When a polymer is polymerized and converted into an imide resin, the (meth) acrylate-aromatic vinyl copolymer and (meth) acrylate polymer that can be used in the present invention can undergo an imidization reaction. As long as it is a linear polymer, it may be a block polymer, a core-shell polymer, a branched polymer, a ladder polymer, or a crosslinked polymer. The block polymer may be an A-B type, an A-B-C type, an A-B-A type, or any other type of block polymer. The core-shell polymer may be composed of only one core and only one shell, or each may be a multilayer.

The imide resin preferably has a weight average molecular weight of 1 × 10 ⁴ to 5 × 10 ⁵ . When the weight average molecular weight is less than 1 × 10 ⁴ , the mechanical strength in the case of a film is insufficient, and when it exceeds 5 × 10 ⁵ , the viscosity at the time of melt extrusion is high and the molding processability is lowered. , Productivity of molded products may decrease.

  The imide resin is a (meth) acrylic acid ester-aromatic vinyl copolymer such as methyl methacrylate-styrene copolymer or a (meth) acrylic acid ester polymer such as methyl methacrylate polymer treated with an imidizing agent. If it is a method to do, it can manufacture with various methods, An extruder etc. may be used and a batch type reaction tank (pressure vessel) etc. may be used.

    When the method for producing the imide resin is performed with an extruder, various extruders can be used. For example, a single screw extruder, a twin screw extruder, a multi-screw extruder, or the like can be used. In particular, a twin-screw extruder is preferable as an extruder that can promote mixing of an imidizing agent or a ring closure accelerator with respect to the raw polymer. There are non-mesh type co-rotating type, meshing type co-rotating type, non-meshing type bi-directional rotating type, meshing type bi-directional rotating type, etc. The meshing type co-rotating type is preferable because it can rotate at a high speed and can promote mixing of an imidizing agent or a ring-closing accelerator to be used if necessary. These extruders may be used alone or connected in series.

  The extruder is preferably equipped with a vent port that can be depressurized below atmospheric pressure in order to remove unreacted imidizing agent or by-products such as methanol and monomers.

  For example, instead of an extruder, imide resin can be produced by using a high-viscosity reactor such as a horizontal biaxial reactor such as Violac manufactured by Sumitomo Heavy Industries, Ltd. or a vertical biaxial agitation tank such as Super Blend. It can be used suitably.

  When the production method of the imide resin is performed in a batch-type reaction vessel (pressure vessel), there is no particular limitation as long as the raw material polymer can be melted by heating and stirred, and an imidizing agent or a ring closure accelerator can be added. The polymer viscosity may increase with the progress of the reaction, and those with good stirring efficiency are preferred. For example, Sumitomo Heavy Industries, Ltd. agitation tank Max blend etc. can be illustrated.

  The glass transition temperature of the amorphous thermoplastic resin is preferably 110 ° C. or higher, and more preferably 120 ° C. or higher. When the glass transition temperature is lower than the above value, the application range is limited in applications where heat resistance is required.

  The amorphous thermoplastic resin according to the present invention may contain additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, and a plasticizer within the range not impairing the effects of the present invention. . In addition, the said additive may be individual and may use 2 or more types together.

  Examples of the shape of the raw material resin in the method for producing an optical film according to the present invention include powder, flakes, and pellets. A pellet shape is preferable.

The number of point defects on the surface of the optical film manufactured using the method for manufacturing an optical film of the present invention is 50 / m ² or less. When the number of point defects exceeds 50 / m ² , the display quality is deteriorated when used as a liquid crystal display device or the like as an optical film.

  Here, the point defect in the present specification means a resin-derived defect such as cross-linking of resin and unmelted material. Specifically, it is a defect having a maximum length of 20 μm or more observed in a microscope and having the same refractive index as that of a normal film portion.

  The preferable thickness of the optical film manufactured using the method for manufacturing an optical film of the present invention is 20 μm or more and 350 μm or less. More preferably, they are 50 micrometers or more and 300 micrometers or less, Most preferably, they are 80 micrometers or more and 200 micrometers or less.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited only to these examples. Before describing the specific contents of the examples, first, methods for measuring physical properties and evaluation values shown as results of each experiment will be described below.

(1) Glass transition temperature Using a differential scanning calorimeter (DSC, model DSC-50 manufactured by Shimadzu Corporation) using 10 mg of resin, the glass transition temperature was measured at a heating rate of 20 ° C./min in a nitrogen atmosphere. Determined by point method.
(2) Extrusion amount fluctuation At the resin discharge port, the extrusion amount was measured for 30 minutes every minute, and the variation with respect to the average extrusion amount was calculated.
(3) Resin temperature It measured using the contact-type resin thermometer in the resin discharge port.
(4) Number of point-like defects A 1 m ² film was visually observed in a dark room, and the maximum refractive index was 20 μm or more and the same refractive index as that of a normal film portion with a digital microscope (VH-Z75) manufactured by Keyence Corporation. The number of defects having

Example 1
As the resin, an imide resin obtained by imidizing a commercially available methyl methacrylate-styrene copolymer (MS-800 manufactured by Nippon Steel Chemical Co., Ltd.) using monomethylamine as an imidizing agent was used. Specifically, using a co-meshing twin screw extruder having a diameter of 40 mm and L / D (ratio of the length L to the diameter D of the extruder) of 60, each barrel temperature of the extruder is 250 ° C., screw rotation The number is 150 rpm, the raw material resin supply amount is 20 kg / hour, and the addition amount of monomethylamine is a resin prepared under the conditions of 20 parts with respect to 100 parts of the raw material resin. The glass transition temperature of this imide resin is 130 ° C.

  Next, the imide resin is dried at 100 ° C. for 5 hours, and then extruded into a sheet using a 40 mm single-screw extruder and a 400 mm wide T-die, and the sheet is cooled with a metal cooling roll to have a width of 350 mm and a thickness of A 150 μm film was obtained. Here, as the screw used in the single screw extruder, a dull image screw constituted by a supply unit, a compression unit, a metering unit, and a mixing mechanism (dalmage) after the metering unit was used. Furthermore, the screw has a structure in which the temperature of the screw supply unit and the metering unit and thereafter can be controlled, and the screw temperature is controlled by circulating heating oil inside the screw. Specifically, the screw supply part temperature was 90 ° C., and the temperature after the metering part was 150 ° C. The heater of the single screw extruder is composed of four zones, C1 corresponding to the screw supply section, C2 corresponding to the compression section, C3 corresponding to the measuring section, and C4 corresponding to the mixing mechanism. Was 200 ° C, C2 was 240 ° C, C3 was 270 ° C, and C4 was 270 ° C.

In this case, the variation in the amount of extrusion was 15.0 ± 0.1 kg / hour, the resin temperature was 270 ° C., and the number of point defects on the film surface was 5 / m ² .

(Example 2)
A film was obtained in the same manner as in Example 1 except that the screw supply temperature was 60 ° C.

At this time, the amount of extrusion was 16.0 ± 0.1 kg / hour, the resin temperature was 270 ° C., and the number of point-like defects on the film surface was 5 / m ² .

Example 3
A film was obtained in the same manner as in Example 1 except that the screw supply temperature was 140 ° C.

The amount of extrusion at this time was 14.0 ± 0.1 kg / hour, the resin temperature was 271 ° C., and the number of point defects on the film surface was 5 / m ² .

Example 4
A film was obtained in the same manner as in Example 1 except that the temperature after the screw metering section was 100 ° C.

The amount of extrusion at this time was 15.0 ± 0.1 kg / hour, the resin temperature was 265 ° C., and the number of point defects on the film surface was 3 / m ² .

(Example 5)
A film was obtained in the same manner as in Example 1 except that the temperature after the screw metering section was 180 ° C.

The amount of extrusion at this time was 15.0 ± 0.1 kg / hour, the resin temperature was 280 ° C., and the number of point defects on the film surface was 10 / m ² .

(Comparative Example 1)
A film was obtained in the same manner as in Example 1 except that the screw supply temperature was 50 ° C.

At this time, the amount of extrusion was 20.0 ± 2.0 kg / hour, the resin temperature was 265 ° C., and the number of point defects on the film surface was 60 / m ² .

(Comparative Example 2)
A film was obtained in the same manner as in Example 1 except that the screw supply temperature was 150 ° C.

At this time, the amount of extrusion was 10.0 ± 5.0 kg / hour, the resin temperature was 270 ° C., and the number of point defects on the film surface was 70 / m ² .

(Comparative Example 3)
A film was obtained in the same manner as in Example 1 except that the temperature after the screw metering section was 90 ° C.

The amount of extrusion at this time was 15.0 ± 3.0 kg / hour, the resin temperature was 260 ° C., and the number of point defects on the film surface was 65 / m ² .

(Comparative Example 4)
A film was obtained in the same manner as in Example 1 except that the temperature after the screw metering section was 190 ° C.

The amount of extrusion at this time was 15.0 ± 0.1 kg / hour, the resin temperature was 290 ° C., and the number of point defects on the film surface was 100 / m ² .

(Comparative Example 5)
A film was obtained in the same manner as in Example 1 except that the temperature control after the screw supply unit and the metering unit was not performed.

The amount of extrusion at this time was 15.0 ± 5.0 kg / hour, the resin temperature was 285 ° C., and the number of point defects on the film surface was 100 / m ² .

  The following table summarizes the results of the above experiments.

It is a schematic diagram which shows an example of the screw used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw 2 Extruder cylinder A Screw supply part B Screw compression part C Screw measurement part 2a Extruder cylinder equivalent to a screw supply part 2b Extruder cylinder equivalent to a screw compression part 2c Extruder cylinder equivalent to a screw measurement part

Claims (3)

In an optical film manufacturing method, an amorphous thermoplastic resin is formed by a melt extrusion method using a single-screw extruder having a temperature controllable mechanism with a resin supply screw and a resin metering screw. The manufacturing method of the optical film characterized by satisfy | filling following (1) and (2).
(1) Resin supply section screw temperature in the single screw extruder is glass transition temperature −70 ° C. or higher and glass transition temperature + 10 ° C. or lower (2) Resin metering section screw temperature is glass transition temperature −30 ° C. or higher and glass transition temperature +50 ℃ or less   2. The method for producing an optical film according to claim 1, wherein the amorphous thermoplastic resin is an acrylic resin. The acrylic resin is an imide resin having a unit represented by the following general formula (1), a unit represented by the following general formula (2) and / or a unit represented by the following general formula (3). The method for producing an optical film according to claim 1 or 2.

(However, R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or the number of carbon atoms. The substituent containing a 5-15 aromatic ring is shown.)

(However, R4 and R5 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a carbon number. The substituent containing a 5-15 aromatic ring is shown.)

(However, R7 represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 represents an aryl group having 6 to 10 carbon atoms.)

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