JP5720458B2 - Kind switching method and optical film in manufacturing optical film - Google Patents

Description

  The present invention relates to a method for switching types in the production of an optical film by a solution casting method and an optical film produced using the method.

  Conventionally, an optical film containing a cellulose ester resin is generally used as an optical film used for a retardation film of a polarizing plate of a liquid crystal display device, a polarizer protective film, and the like.

  As a method for producing an optical film containing a cellulose ester resin, a solution casting film forming method is well known. In the solution casting method, first, a mixed solvent containing dichloromethane or methyl acetate as a main solvent is mixed with a cellulose ester resin and various additives such as an ultraviolet absorber, a matting agent, a retardation control agent, and a plasticizer. To prepare. Next, a dope is cast on a support from a casting die to form a casting film. Then, after the cast film becomes self-supporting on the support, the cast film is peeled off as a wet film from the support, dried, and then wound into a roll form as a product film.

  By the way, it is necessary to manufacture the resin film according to the application. However, it is not realistic to provide a solution casting apparatus for each product type, and it is usual to produce a plurality of product types with one solution film forming facility. Since the solution casting equipment cannot manufacture a plurality of varieties at the same time, when manufacturing a plurality of varieties with a single solution casting equipment, first, one varieties are manufactured and manufactured. After that, make other varieties, and so on.

  As a method of changing the type, first, a new dope with a changed type and amount of additive is prepared in a dissolution tank. Next, there is a method of switching the dope by flowing the prepared new dope into the film forming line and replacing the old dope with this new dope.

  However, in the case of the method of switching the type by replacing the old dope with a new dope of the new formulation, it is not necessary to provide a separate preparation device, but the configuration is simplified, but the extrusion replacement is performed and the replacement is completed. By then, it is necessary to flow a new dope of about three times the pipe capacity. For this reason, there exists a problem that the loss of time during extrusion and a product loss become large (for example, refer to patent documents 1).

  In addition, in this method, if it is attempted to reduce time loss and product loss, some of the components of the product before the product change may remain, and may become a foreign substance that causes quality failure for the product after the product change. Therefore, it is necessary to completely remove such foreign matters.

  For example, as a reference technique, Patent Document 2 proposes a method for reducing foreign matter by a flushing technique based on flow rate fluctuations. However, it has been found that a large flow rate fluctuation is difficult to apply to the replacement of the high-viscosity dope, and the effect of reducing foreign matter is insufficient.

JP 2010-100042 A JP 2003-88819 A

  The present invention has been made in view of the above-described problems and situations, and its solution is to change the type in the production of an optical film by the solution casting film forming method in a short time and to reduce the content of foreign matters. It is to provide a method for changing the product type. Moreover, it is providing the optical film manufactured using the said kind change method.

  The above-mentioned problem according to the present invention is solved by the following means.

1. A process of casting one kind of dope in which one kind of resin is dissolved in a solvent on a support at one temperature, and another kind of dope in which another kind of resin is dissolved in a solvent. In the production of an optical film by a solution casting film-forming method , including the step of casting on the support at another temperature, the kind at the time of switching the one kind of dope to the other kind of dope A method of switching, wherein in the step of preparing the other type of dope, the other temperature of the other type of dope is varied within a predetermined range with respect to the one temperature, thereby changing the temperature at the other temperature. the viscosity of the dope of the other varieties, the in one of the temperature, type switching method in the manufacture of an optical film characterized by varying from 30 to 300% lower viscosity of the dope of the other varieties.

2. 2. The method for switching types in the production of an optical film according to item 1, wherein the other temperature of the other types of dopes is varied within a range of −30 to 60 ° C.

  3. 3. A method for switching product types in the production of an optical film according to item 1 or 2, further comprising an ultrasonic cleaning step.

  4). An optical film produced by using the method for switching types in the production of an optical film according to any one of items 1 to 3.

  By the above means of the present invention, it is possible to provide a product type switching method capable of switching product types in the production of optical films by the solution casting film forming method in a short time and reducing the content of foreign substances. Moreover, the optical film manufactured using the said kind change method can be provided.

  In the present invention, in the replacement method of the high-viscosity dope, by changing the dope temperature, the viscosity is changed to change the fluidity, and the piping is ultrasonically vibrated, thereby shortening the type switching time.

The figure which showed typically the dope preparation process, casting process, and drying process of the solution casting film forming method used for this invention

The method for switching the type in the production of the optical film of the present invention includes a step of casting one type of dope, which is obtained by dissolving one type of resin in a solvent, on a support at one temperature, and another type of In the production of an optical film by a solution casting method comprising casting a dope of another kind in which a resin is dissolved in a solvent at another temperature on the support . a type switching method when switching the dope to the dope of the other varieties, in the step of preparing the dope of the other varieties, other temperature of the dope of the other varieties, given to said first temperature The viscosity of the dope of the other kind at the other temperature is changed by 30 to 300% lower than the viscosity of the dope of the other kind at the one temperature by changing within the range. To do. This feature is a technical feature common to the inventions according to claims 1 to 5.

As an embodiment of the present invention, it is preferable to change the other temperature of the other types of dopes within a range of −30 to 60 ° C. from the viewpoint of manifesting the effect of the present invention. Furthermore, it is also preferable to have an ultrasonic cleaning process from the viewpoint of completely removing foreign substances.

  The product type switching method of the present invention can be suitably used in the production of optical films.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

(Outline of product type switching method in optical film production)
The method for switching the type in the production of the optical film of the present invention includes a step of casting one type of dope, which is obtained by dissolving one type of resin in a solvent, on a support at one temperature, and another type of In the production of an optical film by a solution casting method comprising casting a dope of another kind in which a resin is dissolved in a solvent at another temperature on the support . This is a method for switching the type when the dope is switched to the dope of the other type . In particular, in the preparation step of the dope of the other varieties, other temperature of the dope of the other varieties, by varying the relative first temperature within a predetermined range, in the other temperature, of the other the viscosity of the dope varieties, the in one of the temperature, characterized in that varying the 30-300% than the viscosity of the dope other varieties low.

  If the viscosity fluctuation is less than 30%, the product change time becomes long. On the other hand, when the viscosity fluctuation is larger than 300%, the filter is damaged due to a sudden increase in the filtration pressure.

As a method of changing the viscosity of the dope, a method of changing the temperature, a method of changing the content of the solvent, or the like can be adopted. In the present invention, a method of changing the temperature of the dope is particularly preferable. In this case, it is preferable to change the other temperature of the other types of dopes within a range of −30 to 60 ° C.

  For example, in the case of a dope containing triacetyl cellulose as a main component, the dope is varied within a range of 5400 to 540000 mPa · s. For example, in the case of a dope containing an acrylic resin as a main component, the dope is varied within a range of 2700 to 27000 mPa · s.

  The viscometer used for measuring the viscosity according to the present invention is not particularly limited as long as it is tested with a standard solution for calibration of a viscometer defined in JIS Z 8809, and is a rotary type, a vibration type or a capillary type. The viscometer can be used. As a viscometer, it can measure with a Saybolt viscometer, a Redwood viscometer, etc., for example, Tokimec Co., Ltd., a conical plate type E type viscometer, an E Type Viscometer (rotary viscometer) manufactured by Toki Sangyo Co., Ltd., manufactured by Tokyo Keiki Co., Ltd. No. B type viscometer BL, FVM-80A manufactured by Yamaichi Electronics Co., Ltd., Viscoliner manufactured by Nametore Industries Co., Ltd., VISCO MATE MODEL VM-1G manufactured by Yamaichi Electronics Co., Ltd., and the like.

  In this invention, it measured using the vibration-type viscometer.

  As an embodiment of the present invention, it is also preferable that the method is a product type switching method having an ultrasonic cleaning process in order to completely remove foreign matters.

  As a frequency of the ultrasonic wave in the ultrasonic cleaning step, the frequency is preferably 10 to 500 kHz, more preferably 20 to 100 kHz, and further preferably 30 to 50 kHz.

  In the present invention, in the ultrasonic cleaning step, the pipe through which the dope passes is used by using an ultrasonic cleaning device (for example, SPC-P type, Shinka Sangyo Co., Ltd., ultrasonic frequency: 40 kHz, ultrasonic output: 1000 W). Ultrasonic vibration is applied to the inside, and foreign matter is removed and separated to be washed. In addition, as a washing | cleaning liquid, it is preferable to use the same kind of solvent as the solvent contained in dope.

  In addition, it is also preferable to provide a centrifugal separation step after the ultrasonic cleaning step, and to further change the product type in such a manner that foreign matters are separated and removed.

<Cellulose ester resin>
In the present invention, a cellulose ester resin can be used as a component constituting the optical film.

  When the optical film which concerns on this invention contains a cellulose ester, it is preferable that the content rate is in the range of 40-100 mass%.

  The cellulose ester resin that can be used in the present invention needs to select an appropriate cellulose ester resin according to the purpose, but may be substituted with either an aliphatic acyl group or an aromatic acyl group. The acetyl group is preferably substituted.

  When the cellulose ester resin according to the present invention is an ester having an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically, acetyl, propionyl, butyryl, isobutyryl, valeryl, Examples include pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the aliphatic acyl group is meant to include those having a substituent, and the substituent is a substitution of a benzene ring when the aromatic ring is a benzene ring in the above-mentioned aromatic acyl group. What was illustrated as a group is mentioned.

  When the cellulose ester resin is an ester with an aromatic acyl group, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, and particularly preferably One or two.

  Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  The cellulose ester resin has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. The structure used for the cellulose resin according to the present invention These may be single or mixed acid esters of cellulose.

  The substitution degree of the cellulose ester resin according to the present invention is such that the total substitution degree (T) of the acyl group is 2.00 to 3.00. The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms.

  In the cellulose ester resin according to the present invention, those having an acyl group having 2 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose It is preferably at least one selected from acetate benzoate and cellulose benzoate.

  Among these, particularly preferable cellulose ester resins include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate and having an acyl group having 2 to 4 carbon atoms as a substituent.

  The portion that is not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

  If the weight average molecular weight (Mw) of the cellulose ester resin according to the present invention is 75,000 or more, the object of the present invention can be achieved even if the weight average molecular weight is about 1,000,000. The thing of 100000-2400 is still more preferable.

<acrylic resin>
The optical film according to the present invention preferably contains an acrylic resin as a component constituting the optical film. For example, it is preferable to contain the acrylic resin and the cellulose ester resin at a mass ratio in the range of 95: 5 to 30:70.

  The acrylic resin used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These can be used alone or in combination of two or more.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  The acrylic resin used for the optical film according to the present invention preferably has a weight average molecular weight (Mw) of 80,000 to 1,000,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film.

  The weight average molecular weight of the acrylic resin according to the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin in this invention, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  With this molecular weight, both heat resistance and brittleness can be achieved.

  A commercially available thing can also be used as an acrylic resin which concerns on this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dialal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. .

  In the present invention, as the resin film substrate used as a component of the optical film according to the present invention, in addition to the above acrylic resin and cellulose ester resin, other types of thermoplastic resins may be used as long as the effects of the present invention are not impaired. It can also be used together. Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to the glass transition temperature or melting point and can be molded into a desired shape.

  General thermoplastic resins include polyethylene (PE), high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS). , Polyvinyl acetate (PVAc), Teflon (registered trademark) (polytetrafluoroethylene, PTFE), ABS resin (acrylonitrile butadiene styrene resin), AS resin, and the like. It is preferable to process by this method.

  When strength and resistance to breakage are particularly required, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), polybutylene terephthalate (PBT) ), Polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like.

  When higher heat distortion temperature and long-term use characteristics are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, polyetheretherketone, heat Plastic polyimide (PI), polyamideimide (PAI), or the like can be used.

  In addition, it is possible to perform the kind of resin and the combination of molecular weight according to the use of this invention.

<Other additives>
In the optical film according to the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 mPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing the film substrate. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

  The composition containing the film substrate according to the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based ones. It is done. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone And benzophenones.

  Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine Examples include hybrid systems having both structures, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  Furthermore, various antioxidants can also be added to the acrylic resin used in the optical film according to the present invention in order to improve thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

  As the acrylic resin composition according to the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

  Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphate esters, halogen-containing condensed phosphonate esters, halogen-containing phosphite esters, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

  In the present invention, additives such as a retardation adjusting agent and a matting agent can be added in addition to the above additives.

<Method for forming optical film>
The method for switching the type in the production of the optical film of the present invention includes a step of casting one type of dope, which is obtained by dissolving one type of resin in a solvent, on a support at one temperature, and another type of In the production of an optical film by a solution casting method comprising casting a dope of another kind in which a resin is dissolved in a solvent at another temperature on the support . A method for switching varieties when switching a dope to the other type of dope, wherein in the step of preparing the dope of the other type , another temperature of the dope of the other type is set to a predetermined value with respect to the one temperature. The viscosity of the dope of the other kind at the other temperature is changed by 30 to 300% lower than the viscosity of the dope of the other kind at the one temperature by changing within the range. To do.

<Solution casting film forming method>
(Organic solvent)
The organic solvent useful for forming the dope when the optical film according to the present invention is produced by the solution casting method is used without limitation as long as it dissolves acrylic resin, cellulose ester resin, and other additives simultaneously. be able to.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy, and when the proportion of alcohol is small, the acrylic resin and cellulose ester resin dissolve in a non-chlorine organic solvent system. There is also a role to promote.

  In particular, a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms contains at least a total of 15 types of acrylic resin, cellulose ester resin, and acrylic particles (C). It is preferable that it is a dope composition dissolved in 45% by mass.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, the preferable film forming method of the optical film according to the present invention will be described.

1) Dissolution process In an organic solvent mainly composed of a good solvent for acrylic resin and cellulose ester resin, the acrylic resin, cellulose ester resin, and in some cases acrylic particles (C) and other additives are dissolved in a dissolution vessel while stirring. This is a step of forming a dope, or a step of mixing the acrylic resin or cellulose ester resin solution with an acrylic particle (C) solution or other additive solution to form a dope that is a main solution.

  For dissolution of acrylic resin and cellulose ester resin, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9- Various dissolution methods such as a method of performing a cooling dissolution method as described in JP-A-95557 or JP-A-9-95538, a method of performing at high pressure as described in JP-A No. 11-21379 can be used, In particular, a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is preferable.

  The total amount of the acrylic resin and the cellulose ester resin in the dope is preferably 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Filtration is preferably performed using a filter medium having a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are only aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  FIG. 1 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

  If necessary, large agglomerates are removed from the acrylic particle charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

  The additive solution containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and 1 to 5% by mass. Most preferably.

  The above range is preferable because the smaller the acrylic particle content, the lower the viscosity and the easier the handling, and the higher the acrylic particle content, the smaller the addition amount and the easier the addition to the main dope.

  The return material is a product obtained by finely pulverizing an optical film, and is produced by forming an optical film by cutting off both sides of the film, or by using a film original that has been speculated out by scratches.

  In addition, an acrylic resin, a cellulose ester resin, and, in some cases, acrylic particles kneaded into pellets can be preferably used.

2) Casting process An endless metal belt 31, such as a stainless steel belt or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it infinitely. This is a step of casting the dope from the pressure die slit to the casting position on the support.

  A pressure die that can adjust the slit shape of the die base and facilitates uniform film thickness is preferred. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

  The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is preferably peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, and slippage and vertical stripes are likely to occur due to peeling tension, so the balance between economic speed and quality The amount of residual solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166 N / m, and then peel at a minimum tension of 137 N / m, and particularly preferably peel at a minimum tension of 100 N / m.

  In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 ° C, more preferably 10 to 40 ° C, and most preferably 15 to 30 ° C.

5) Drying and stretching step After peeling, a drying device 35 that transports the web alternately through rolls arranged in the drying device and / or a tenter stretching device 34 that clips and transports both ends of the web with clips. And dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  30-150 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-120 degreeC is more preferable, and 70-100 degreeC is the most preferable.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding process This is a process in which the amount of residual solvent in the web becomes 2% by mass or less, and is taken up by the winder 37 as a film, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. Can be obtained.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The optical film according to the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m, and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

  Although there is no restriction | limiting in particular in the film thickness of the optical film which concerns on this invention, When using for the polarizing plate protective film mentioned later, it is preferable that it is 20-200 micrometers, it is more preferable that it is 25-100 micrometers, and it is 30-80 micrometers. It is particularly preferred.

<Polarizing plate>
The polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the optical film according to the present invention, and is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution.

  On the other surface, the optical film according to the present invention may be used, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, OP Etc.) are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. Preferably, a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded is suitably used.

  Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate types and oxidized polyether methacrylates, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-pack type instantaneous pressure-sensitive adhesives.

  The pressure-sensitive adhesive may be a one-component type or a type that is used by mixing two or more components before use.

  The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the optical film according to the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced.

  The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate according to the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. In particular, in a large-screen display device having a screen size of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen, and the effect is maintained for a long time.

  In addition, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even during long-time viewing.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Fine particle dispersion 1>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass [Preparation of dope]
A dope 1 having the following composition was prepared.

(Composition of dope 1)
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Triacetyl cellulose (acetyl substitution degree 2.79, weight average molecular weight 230,000; described as TAC in the table) 100 parts by mass Triphenyl phosphate 5 parts by mass Ethylphthalyl ethyl glycolate 5 Part by mass Particulate additive solution 1 1 part by mass The above was put into a closed container and dissolved while stirring to prepare a dope.

(Composition of dope 2)
Next, a dope 2 having the following composition was prepared.

Acrylic resin (weight average molecular weight: 130000 (Tg 140 ° C.), polymerization rate 97%)
70 parts by weight Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000)
30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above was put into a closed container and dissolved while stirring to prepare a dope.

(Dope 1 filling)
Dope 1 was completely filled into the factory piping.

(Substitution with dope 2)
The dope 2 started to flow through the pipe filled with the dope 1. The flow rate was 500 L / hr.

  In order to vary the viscosity, the temperature of the dope 2 was changed. Every hour, the temperature of the dope 2 was varied in the range of 5 ° C to 60 ° C. The method for changing the dope temperature was changed by paying out the dope 2 prepared in a sealed container and temperature-controlled by a jacket.

The viscosity was measured with an in-line type vibration viscometer, and the viscosity change when the temperature was changed was 30 to 300% of the viscosity before the change .

[Evaluation]
(Product change time)
The product change time was determined as follows according to the time taken for the foreign matter to disappear.

A: Time required for disappearance of foreign matter is within 12 hours. ○: Time required for disappearance of foreign matter is longer than 12 hours and within 48 hours. X: Time required for disappearance of foreign matter is longer than 48 hours. Far from possible (filter breakage)
The filter breakage was judged by the presence or absence of a sudden increase in foreign matter due to the mesh opening accompanying the filter breakage.

◎: There is almost no increase in foreign matter, and the quality is sufficiently good. ○: The increase in foreign matter is small and the quality is good. ×: The number of foreign matters increases sharply, causing a problem in quality. Example 2
Except for the fact that an ultrasonic cleaning device (SPC-P type, manufactured by Shinshin Sangyo Co., Ltd.) is attached to the pipe, ultrasonic vibration is applied to the pipe through which the dope passes, and foreign matter is peeled off, separated and washed. The filling and viscosity variation were performed in the same manner as in Example 1.

  The conditions when the ultrasonic waves were applied were ultrasonic frequency: 40 kHz and ultrasonic output: 1000 W.

Comparative Example 1
The same procedure as in Example 1 was performed, except that the dope temperature variation for causing the viscosity variation at the time of substitution was 38 to 45 ° C. The viscosity variation was less than 30%.

Comparative Example 2
The same procedure as in Example 2 was performed except that the dope temperature variation for causing the viscosity variation at the time of substitution was 38 to 45 ° C. The viscosity variation was less than 30%.

Comparative Example 3
The same method as in Example 1 was carried out except that the dope temperature fluctuation for causing the viscosity fluctuation at the time of substitution was 2 to 70 ° C. Viscosity variation was greater than 300%.

Comparative Example 4
The same method as in Example 2 was performed except that the dope temperature variation for causing the viscosity variation at the time of substitution was 2 to 70 ° C. Viscosity variation was greater than 300%.

  The evaluation results are shown in Table 1.

  As is clear from the results shown in Table 1, in the dope replacement at the time of product change in the production of optical films, the viscosity of the dope is varied in the range of 30 to 300%, and an ultrasonic cleaning process is provided. Thus, it can be seen that the time for switching the type can be shortened.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 17 Three-way valve 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roll dryer 41 Particle charging vessel 42 Stock tank 43 Pump 44 Filter

Claims (4)

A process of casting one kind of dope in which one kind of resin is dissolved in a solvent on a support at one temperature, and another kind of dope in which another kind of resin is dissolved in a solvent. In the production of an optical film by a solution casting film-forming method , including the step of casting on the support at another temperature, the kind at the time of switching the one kind of dope to the other kind of dope A switching method,
In the step of preparing the dope of the other kind, the other temperature of the dope of the other kind is changed within a predetermined range with respect to the one temperature, thereby changing the temperature of the other kind of dope . A method for changing the type in the production of an optical film , wherein the viscosity of the dope is changed by 30 to 300% lower than the viscosity of the dope of the other type at the one temperature . The method for switching types in the production of an optical film according to claim 1, wherein other temperatures of the other types of dopes are varied within a range of -30 to 60 ° C.   The method for switching the type in the production of an optical film according to claim 1, further comprising an ultrasonic cleaning step.   An optical film manufactured by using the method for switching types in manufacturing an optical film according to any one of claims 1 to 3.

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