JP5338673B2 - Method for producing aromatic polycarbonate film - Google Patents

Description

  In the present invention, after casting a polycarbonate solution on a support such as a metal, the polycarbonate solution is peeled off from the support in a state containing a certain amount of solvent, and dried to obtain various optical materials, glass substitute substrates, and the like. The present invention relates to a method for forming a polycarbonate resin film having excellent optical properties and smoothness used in the above field.

  In an industrial production method of a film or the like by a solution casting film forming method of polycarbonate, a metal substrate such as a steel belt is generally used as a support. On this support, a polycarbonate solution is cast from an extrusion die, a film-like material called a web is formed, the solvent contained in the web is volatilized to some extent, and then peeled off from the support ( For example, see Patent Document 1.)

  By the way, in such a manufacturing method, since it was necessary to volatilize the solvent sufficiently, the casting speed (hereinafter referred to as CS) had to be slowed down in a normal facility, and the productivity was poor. In addition, when the belt length was increased in order to enable high CS, strong static electricity was generated at the time of peeling, and this caused damage to the belt, film streaks, unevenness, and micro scratches. For this reason, it was very difficult to produce a high-quality film with high productivity over the long term.

  Conventionally, several techniques have been proposed for stripping a film or the like from a support. For example, a method of adding a release agent in a polymer resin solution to help stripping, or a method of covering the surface of a support with, for example, a fluororesin to reduce its surface energy and reduce the peel force of a film or the like Etc. have been proposed.

  For example, Patent Documents 2 to 5 are disclosed as the main definition of conditions for stripping a film or the like from a support.

  In particular, Patent Document 2 is characterized in that the amount of residual solvent at the time of peeling is 10 to 30% based on the dry amount, and the surface temperature of the support is kept at 20 ° C. or lower and 15.5 ° C. or higher at the peeled portion. A casting film forming method is described.

  In Patent Document 6, in the method of producing a film by peeling a film-like material from a support, the film-like material is peeled off and the surface temperature of the support is changed while the next casting is performed on the support. A casting film forming method is described in which a portion having a dew point lower than the surface temperature of the support is filled with a portion at 15 ° C. or lower and the support is exposed.

  In Patent Document 7, when a polymer solution is cast on a support and dried to produce an optical polymer film, the liquid film is cast and supported at a temperature of −40 ° C. to 10 ° C. A method for producing an optical polymer film characterized by drying on the body and a method for producing a film having optical anisotropy only in the thickness direction are described.

In these technologies, surface defects such as transfer, peeling scratches, adhesive scratches, and scratches, and transparency are certainly improved. However, in applications such as glass substitute substrates for organic EL, these known technologies are used. Even if it is used, it cannot be said that it is sufficient, and since the belt is gradually damaged by the charge generated at the time of peeling, it has been difficult to stably produce a high-quality resin film in the long term. This problem has become more apparent when it is desired to improve the film forming speed, or when it is desired to increase the thickness of the film to be formed.
JP-A-5-239229 Japanese Patent No. 2640189 JP-A-5-239229 JP-A-2-111511 Japanese Patent Laid-Open No. 7-304048 JP-A-2-111511 Japanese Patent Laid-Open No. 7-304048

  For this reason, in the prior art, when the web is peeled from the support, peeling with a low residual solution is indispensable, which makes it very easy to be charged during peeling, and stable continuous film formation at high CS is very easy. It was difficult.

  An object of the present invention is to provide a casting film forming method for a polycarbonate film that solves the above-described problems and is excellent in optical properties and smoothness.

  The above object of the present invention is achieved by the following configurations.

  1. A dope composition in which 15 to 45% by mass of an aromatic polycarbonate is dissolved in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 6 carbon atoms, the methylene chloride and the aliphatic A dope composition having an alcohol ratio (MA represented by the following formula (i)) of 4 to 14 is cast on an endless belt under an atmosphere in which the dew point is controlled to 0 to 15 ° C., and the following formula ( A method for producing an aromatic polycarbonate film, comprising peeling in a state where the residual solvent concentration represented by ii) is 35 to 45%.

Formula (i) MA = mass of aliphatic alcohol / (mass of aliphatic alcohol + mass of methylene chloride) × 100
Formula (ii) Residual solvent concentration (%) = solvent amount / (solvent amount + solvent mass) × 100
2. 2. The method for producing an aromatic polycarbonate film according to 1 above, wherein a dope composition having a ratio (MA) of methylene chloride to aliphatic alcohol of 5 to 12 is used.

  3. 3. The method for producing an aromatic polycarbonate film as described in 1 or 2 above, wherein peeling is performed in an atmosphere in which the dew point of the peeling portion is controlled to 0 to 5 ° C.

  4). 4. The method for producing an aromatic polycarbonate film according to any one of 1 to 3 above, wherein the time from casting on a belt to peeling is 120 to 270 seconds.

  According to the present invention, it is possible to provide a casting film forming method for a polycarbonate film which is very excellent in optical properties and smoothness.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  As a result of intensive studies on the casting film forming method, the present inventors have found the following points and completed the present invention. That is, by adjusting the solvent composition and solid content concentration of the dope appropriately and controlling the temperature and humidity at the time of film formation and peeling, it is possible to peel with a high residual solution, and to produce a polycarbonate film with high CS and good quality for a long time. Therefore, it is possible to manufacture stably.

  In the method for producing an aromatic polycarbonate film of the present invention, 15 to 45% by mass of an aromatic polycarbonate is dissolved in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 6 carbon atoms. An atmosphere having a dew point controlled at 0 to 15 ° C., which is a dope composition having a ratio of methylene chloride to aliphatic alcohol (MA represented by the following formula (i)) of 4 to 14 It is cast on an endless belt below and peels in a state where the residual solvent concentration represented by the following formula (ii) is 35 to 45%.

Formula (i) MA = mass of aliphatic alcohol / (mass of aliphatic alcohol + mass of methylene chloride) × 100
Formula (ii) Residual solvent concentration (%) = solvent amount / (solvent amount + solvent mass) × 100
Hereinafter, the present invention will be described in detail.

(Aromatic polycarbonate)
The aromatic polycarbonate used in the present invention is not particularly limited, and is not particularly limited as long as it is an aromatic polycarbonate capable of obtaining desired film characteristics. In general, polymer materials collectively referred to as polycarbonate are generically referred to as those in which the polycondensation reaction is used in the synthesis method and the main chain is linked by a carbonic acid bond. , Phenol derivative, phosgene, diphenyl carbonate and the like are obtained by polycondensation. Usually, an aromatic polycarbonate represented by a repeating unit having a bisphenol component of 2,2-bis (4-hydroxyphenyl) propane, which is called bisphenol-A, is preferably selected. An aromatic polycarbonate copolymer can be constituted by appropriately selecting various bisphenol derivatives.

  In addition to this bisphenol-A, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, , 1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) -2 -Phenylethane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) sulfide, Bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) -3,3,5-to It can be exemplified methyl cyclohexane.

  It is also possible to use an aromatic polyester carbonate partially containing a terephthalic acid and / or isophthalic acid component. By using such a structural unit as a part of the constituent component of the aromatic polycarbonate composed of bisphenol-A, the properties of the aromatic polycarbonate, such as heat resistance and solubility, are improved. However, the present invention is also effective for such a copolymer.

  The viscosity average molecular weight of the aromatic polycarbonate used here is preferably 10,000 to 200,000. A viscosity average molecular weight of 20,000 to 120,000 is particularly preferred. If a resin having a viscosity average molecular weight lower than 10,000 is used, the mechanical strength of the obtained film may be insufficient, and if the molecular weight is higher than 400,000, the viscosity of the dope becomes too high, causing problems in handling. . The viscosity average molecular weight can be measured by commercially available high performance liquid chromatography.

  In the present invention, among the solvents used in the aromatic polycarbonate solution composition, the ratio of methylene chloride to aliphatic alcohol (MA represented by the following formula (i)) is 4 to 14. To do.

Formula (i) MA = mass of aliphatic alcohol / (mass of aliphatic alcohol + mass of methylene chloride) × 100
The ratio (MA) is preferably 5-12.

  The present invention comprises the above methylene chloride and aliphatic alcohol in the dope composition, but other solvents can also be used. The remaining solvent is not particularly limited as long as it dissolves aromatic polycarbonate at a high concentration and is compatible with alcohol, and furthermore, it is a low boiling point solvent. For example, as a solvent having a solubility in aromatic polycarbonate, halogen solvents such as chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, 1,3-, in addition to methylene chloride, Examples thereof include cyclic ether solvents such as dioxolane, 1,4-dioxane and tetrahydrofuran, and ketone solvents such as cyclohexanone.

  When using other solvent, there is no limitation in particular and it may use it in consideration of an effect. The effects here include mixing the solvent without sacrificing solubility and stability, for example, improving the surface properties of the film formed by the solution casting method (leveling effect), evaporation rate and system These include viscosity adjustment and crystallization suppression effects. What is necessary is just to determine the kind and addition amount of the solvent to mix by the degree of these effects, and you may use 1 type (s) or 2 or more types as a solvent to mix.

  Other solvents preferably used include halogen solvents such as chloroform and 1,2-dichloroethane, hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ethyl acetate and butyl acetate. Ether solvents such as ester solvents, ethylene glycol dimethyl ether, methoxyethyl acetate and the like can be mentioned.

  The type of alcohol added is limited by the solvent used. It is a necessary condition that the alcohol and the solvent are compatible. These may be added alone or in combination of two or more. The alcohol in the present invention is preferably a linear or branched aliphatic alcohol having 1 to 6, preferably 1 to 4, more preferably 2 to 4 carbon atoms. Specific examples thereof include methanol, ethanol, isopropanol, and tertiary butanol. Of these, ethanol, isopropanol, and tertiary-butanol have almost the same effect, but methanol has a slightly lower effect. Although the reason is not clear, it is assumed that the boiling point of the solvent, that is, the ease of flying during drying is related. Higher alcohols beyond that are not preferable because they have a high boiling point and are likely to remain after film formation.

  The amount of alcohol added must be carefully selected. These are completely poor in solubility in aromatic polycarbonate and are completely poor solvents. Therefore, it cannot be added too much, and should be the minimum amount that provides satisfactory peelability. In general, it is 1 to 10% by mass, preferably 1 to 8% by mass, more preferably 1.5 to 5% by mass with respect to the total amount of solvent. It is preferable to be adjusted to.

  When the addition amount is in the range of 1 to 10% by mass, the solubility of the solvent in the polymer and the dope stability are improved, and the effect of improving the peelability is increased.

  The solution composition of the present invention may be prepared by any method as long as a transparent solution having a low haze is obtained as a result. A predetermined amount of alcohol may be added to the aromatic polycarbonate solution dissolved in a certain solvent in advance, or the aromatic polycarbonate may be dissolved in a mixed solvent containing alcohol. Good. However, as described above, since alcohol is a poor solvent, there is a possibility of doping cloudiness due to precipitation of polymer in the method of adding after the former, so the method of dissolving in the latter mixed solvent. Is preferred.

  The aromatic polycarbonate solution composition (dope) in the present invention depends on the cosolvent used and the molecular weight of the aromatic polycarbonate, but the amount of aromatic polycarbonate is 15 to 45. It is preferable to make it contain in the range of 15-55 mass%, and also 20-50 mass% of solvent amount with respect to mass% containing. If the amount of solvent exceeds this, the stability of the solution will not be a problem, but since the effective concentration of the aromatic polycarbonate becomes low, the solution viscosity becomes low when the solution composition is used to form a film by the solution casting method. Since it is low, external disturbance is likely to occur, and it is difficult to obtain surface smoothness. Conversely, if the amount of the solvent is less than this, it is difficult to obtain a stable dope. These concentrations are determined mainly in consideration of the dope stability and the solution viscosity.

  In the present invention, after casting an aromatic polycarbonate solution composition (dope) on a support substrate, the solvent is evaporated to obtain a film. The solvent can be evaporated by heating. An industrial continuous film-forming process generally comprises three steps: a casting step, a pre-drying step, and a post-drying step. The casting process is a process for smoothly casting the dope, the pre-drying process is a process for removing most of the solvent from the cast dope, and the post-drying process is for removing the remaining solvent. It is a process.

  In the casting process, a method of extruding from a die, a method using a doctor blade, a method using a reverse roll coater, or the like is used. Industrially, the most common method is to continuously extrude the dope from the die onto a belt-like or drum-like support substrate. Examples of the support substrate used include a glass substrate, a metal substrate such as stainless steel and ferrotype, and a plastic substrate such as polyethylene terephthalate. Needless to say, the material and surface state of the support substrate also have a great influence on the peelability of the cast film. For example, in the case of a substrate coated with Teflon (registered trademark) having a very low surface tension, the peelability is good. However, a metal substrate having a mirror-finished surface is most commonly used for industrially forming a film having a high surface property and optical homogeneity on an industrial scale, and the present invention uses such a metal substrate. The effect is recognized.

  In general, the solution viscosity is an extremely important factor in forming a transparent and smooth film from a dope. The solution viscosity depends on the polymer concentration, molecular weight, and type of solvent, but the viscosity of the solution composition of the present invention is 500 to 50000 cps, preferably 700 to 30000 cps. Exceeding this is not preferable because the fluidity of the solution is lowered and a smooth film may not be obtained. If it is less than that, the fluidity is too high, and it becomes difficult for the dope to be discharged uniformly from the T die usually used for casting, or the surface is disturbed due to external disturbance, and a uniform and smooth film cannot be obtained. The effect on the viscosity of the solution due to the addition of the alcohol is slight because the addition amount is very small.

  The temperature at the time of casting of the present invention depends on the solvent used, but is 10 to 40 ° C, preferably 15 to 35 ° C. In order to obtain a film with excellent smoothness, the solution extruded from the die needs to be cast and smoothed on the support substrate. At this time, if the casting temperature is too high, the surface is dried and solidified before being smoothed, which is not preferable. On the other hand, if the temperature is too low, the casting solution is cooled to increase the viscosity, and it is difficult to obtain smoothness and condensation is not preferable.

  The humidity at the time of casting of the present invention is characterized by being cast on an endless belt in an atmosphere in which the dew point is controlled at 0 to 15 ° C. Preferably it is 0-5 degreeC. By controlling the dew point within the above range, the releasability is improved and a polycarbonate film having excellent optical properties and smoothness can be obtained. When a film is formed in an atmosphere where the dew point exceeds 15 ° C., water droplets that are condensed on the surface adhere to the surface, resulting in a loss of flatness and a cause of dust and foreign matter. Further, in an atmosphere exceeding 20 ° C., whitening occurs at the dew portion on the surface, and in an atmosphere exceeding 25 ° C., the film is entirely whitened, and the film may be broken and broken at the time of peeling.

  For the control of the dew point, the entire casting process may be divided into one or a plurality of zones. In particular, it is preferable to control the dew point as an independent zone by blowing dry air around the peeling portion or by providing an enclosure around the peeling portion.

  Before moving from the casting process to the drying process, the surface property of the film can be highly smoothed (leveling effect) by suppressing the drying for a certain period of time and ensuring the fluidity of the dope.

  In the pre-drying step, it is necessary to evaporate and remove most of the solvent from the dope cast on the support substrate in as short a time as possible. However, the drying conditions should be carefully selected because they undergo deformation due to foaming when rapid evaporation occurs. In the present invention, the drying should be started from the lowest boiling point of the solvent to be used, preferably within the range having its upper limit (boiling point−5 ° C.). Thereafter, the temperature should be raised sequentially or continuously to increase the drying efficiency. The upper limit of the temperature at the final stage in this process is 120 ° C, preferably 100 ° C. In this step, since the residual solvent is 35 to 45% by mass in the case of the present invention, if the temperature is higher than that, it is not preferable because foaming occurs. Moreover, you may send a wind as needed. In that case, generally, a wind speed of 20 m / sec or less, preferably 15 m / sec or less is used. Beyond that, a smooth surface cannot be obtained due to wind disturbance, which is not preferable. The wind speed may be increased stepwise or continuously, but is preferable. There may be no wind at the initial stage to avoid wind turbulence.

  In this pre-drying step, the film is on the substrate and is peeled off from the substrate at the end of the step. At that time, if the amount of residual solvent is large, the film is soft and deforms, and if the amount of residual solvent is small, even a cast film cast from the solution composition of the present invention has high adhesiveness to the support substrate and peelability. Causes stress distortion, peeling muscles, and peeling scratches. Therefore, the amount of residual solvent is an important factor, and the range where the amount of residual solvent represented by the following formula (ii) is preferably 35 to 45% by mass is selected.

Formula (ii) Residual solvent concentration (%) = solvent amount / (solvent amount + solvent mass) × 100
In the solution casting method using a metal substrate, the peelability is generally good at the beginning of film formation, but the peelability often decreases gradually as the peeling is repeated. The cause of this is not clear, but gradually many metal atoms with high surface tension are exposed on the surface of the substrate, or a very small amount of polymer adheres to the surface, which starts to work like an adhesive layer. It is estimated that. As a countermeasure, the releasability can be recovered by periodically cleaning the substrate surface, for example, wiping the substrate surface with water, but this is an extremely troublesome operation in an industrial continuous film forming process and is not efficient. According to the present invention, the peelability of the cast film from the support substrate can be maintained well without performing such work.

  In the post-drying step, the film peeled off from the substrate is further dried, and the residual solvent amount must be 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less. This is because when there is a large amount of residual solvent, deformation occurs over time, or when heat is applied in a subsequent processing step such as a liquid crystal display device, dimensional change, so-called thermal shrinkage, occurs. In general, in the post-drying process, a method of drying while conveying a film by a pin tenter method or a roll suspension method is adopted industrially. In these methods, various forces are applied to the film during the drying. Therefore, in film formation where a high degree of optical homogeneity is required, such as for liquid crystal display devices, the drying temperature must be selected from a range where deformation of the film does not occur. Generally, when the glass transition temperature of the aromatic polycarbonate used is Tg (° C.), the range is (Tg−120 ° C.) to Tg, preferably (Tg−100 ° C.) to (Tg−10 ° C.). Is selected. If it is more than that, thermal deformation of the film occurs, which is not preferable, and if it is less than that, the drying speed is remarkably slow. Thermal deformation becomes less likely to occur as the residual solvent decreases. Therefore, it is preferable to use a method in which the temperature is initially lowered within this range, and then stepwise or continuously. In the subsequent drying step, air may be blown in the same manner as in the predrying step.

  In the present invention, when producing the aromatic polycarbonate film, the solvent gas concentration is high, and drying may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. When a flammable solvent is used, the drying method in an inert gas atmosphere is preferable from the viewpoint of safety considering the explosion limit of the solvent. In this case, the gas concentration of the solvent is preferably 3% by volume or more in consideration of the drying heat energy and the recovery efficiency. The oxygen concentration in the inert gas atmosphere is preferably 10% by volume or less.

  The thickness of the film of the present invention is in the range of 10 to 300 μm, preferably 50 to 200 μm. In particular, a thickness of 50 to 200 μm is preferably used for the plastic substrate and the retardation film for the retardation film constituting the display device. If it is thicker than this, it is difficult to remove the residual solvent, and if it is thinner than this, it is difficult to suppress thickness unevenness.

<Display device>
By using the aromatic polycarbonate film produced according to the present invention, various display devices having excellent visibility can be produced. The aromatic polycarbonate film of the present invention can be used in various types of driving such as reflective, transmissive, transflective LCD or TN, STN, OCB, HAN, VA (PVA, MVA), IPS, etc. It is preferably used in the LCD of the type. The aromatic polycarbonate film of the present invention is excellent in flatness and is preferably used for various display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and electronic paper.

(Organic EL device)
An organic EL (electroluminescence) element in which the aromatic polycarbonate film of the present invention is particularly preferably used will be described.

  The organic EL element has a transparent electrode disposed on the inner side of two substrates, and a layer having, for example, (a) an injection function, (b) a transport function, and (c) a light emission function is laminated therebetween. An organic EL element layer made of a composite layer or the like is sandwiched between and the periphery is sealed. In the case of constituting an organic EL device, for example, a substrate (including a patterned transparent conductive layer and an auxiliary electrode layer) using the aromatic polycarbonate film of the present invention / hole injection layer / hole transport layer / light emitting layer / The layer structure which consists of an electron injection layer / cathode / sealing layer can be mentioned. The layer structure is not particularly limited, and specifically, anode / light emitting layer / cathode, anode / hole injection layer / light emitting layer / cathode, anode / light emitting layer / electron injection layer / cathode, anode / Many layer structures such as hole injection layer / light emitting layer / electron injection layer / cathode, anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode can be handled. It is not limited to this configuration, and may be accompanied by a color filter for colorization or other means (layers). The organic EL element can use a glass substrate as a substrate, but the aromatic polycarbonate film of the present invention can be applied to the outside of the glass substrate, or the aromatic polycarbonate film of the present invention can be used instead of the glass substrate. If both of the two glass substrates are replaced with the aromatic polycarbonate film of the present invention, the entire display can be made flexible.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Polycarbonate resin used>
・ Teijin Chemicals Ltd. Panlite L-1225Y
・ Teijin Chemicals Ltd. Panlite K-1300Y
Copolymer A: BCF (9,9-bis- (3-methyl-4-hydroxyphenyl) fluorene) and BPA (2,2-bis- (4-hydroxyphenyl) -propane) as monomers and BCF30 Copolymerization at mol% / 70 mol% BPA (Tg 195 ° C)
Copolymer B: BCF (9,9-bis- (3-methyl-4-hydroxyphenyl) fluorene) and BPA (2,2-bis- (4-hydroxyphenyl) -propane) as monomers and BCF70 Copolymerization at mol% / BPA30mol% (Tg230 ℃)
The present invention and a comparative aromatic polycarbonate film were prepared by the following production method.

[Example 1]
35 parts by mass of polycarbonate resin (Teijin Chemicals Ltd. Panlite L-1225Y) containing bisphenol A as a structural unit is stirred at 25 ° C. with respect to 65 parts by mass of a mixed solvent of methylene chloride and ethanol containing 3.3 parts by mass of ethanol. The resulting solution was dissolved to obtain a transparent and viscous dope. This dope was blown on a stainless steel belt having a dew point controlled to 7 ° C. or less by blowing dry air, and peeled after 220 seconds. The residual solvent at that time was 42% by mass. Since the peelability was good and there was little charge, no peeling step or peeling streaks were visually observed on the film surface. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 115 μm.

[Example 2]
30 parts by mass of polycarbonate resin (Teijin Chemicals Corporation Panlite K-1300Y) containing bisphenol A as a structural unit is stirred at 25 ° C. with respect to 70 parts by mass of a mixed solvent of methylene chloride and ethanol containing 8.4 parts by mass of ethanol. The resulting solution was dissolved to obtain a transparent and viscous dope. This dope is blown with dry air to flow on a stainless steel belt whose dew point is controlled to 5 ° C. or lower, and after 200 seconds in an atmosphere where the dew point is 3 ° C. or lower by covering the peeled portion with a dehumidifier and attaching a dehumidifier. It peeled. The residual solvent at that time was 42% by mass. Since the peelability was good and there was little charge, no peeling step or peeling streaks were visually observed on the film surface. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 114 μm.

[Example 3]
Transparently dissolve 32 parts by mass of copolymer polycarbonate resin (copolymer A) containing bisphenol A with stirring at 25 ° C. with respect to 68 parts by mass of methylene chloride and ethanol mixed solvent containing 2.7 parts by mass of ethanol. A thick dope was obtained. This dope was blown on a stainless steel belt having a dew point controlled to 10 ° C. or less by blowing dry air, and peeled off after 250 seconds. The residual solvent at that time was 40% by mass. Since the peelability was good and there was little charge, no peeling step or peeling streaks were visually observed on the film surface. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 125 μm.

[Example 4]
Transparently dissolve 37 parts by mass of copolymer polycarbonate resin (copolymer B) containing bisphenol A with stirring at 25 ° C. with respect to 63 parts by mass of methylene chloride and ethanol mixed solvent containing 4.4 parts by mass of ethanol. A thick dope was obtained. The dope was blown on a stainless steel belt with a dew point controlled to 8 ° C. or less by blowing dry air, and the residual solvent was peeled off at 42% by mass. The time from casting to peeling was 130 seconds. Since the peelability was good and there was little charge, no peeling step or peeling streaks were visually observed on the film surface. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 85 μm.

[Examples 5 to 13]
As described in Table 1, the polycarbonate resin, solvent, MA, dew point, residual solvent, time from stretching to peeling, and film thickness were changed, and the aromatic polycarbonate film of Examples 5 to 13 was changed in the same manner as in Example 1. Produced.

[Comparative Example 1]
10 parts by mass of polycarbonate resin (Teijin Chemicals Ltd. Panlite K-1300Y) containing bisphenol A as a structural unit was stirred at 25 ° C. with respect to 90 parts by mass of methylene chloride and ethanol mixed solvent containing 5.4 parts by mass of ethanol. The resulting solution was dissolved to obtain a transparent and viscous dope. This dope was poured on a stainless steel belt whose dew point was controlled to 10 ° C. or less by blowing dry air, and was peeled off after 300 seconds. The residual solvent at that time was 40 mass%, and the film thickness was 115 μm. Since the solid content was small, it took a very long time to peel off, and the production efficiency was extremely low. Moreover, since the dope concentration was low, the viscosity was low, and when fluent, reticulated or yuzu skin appeared on the surface, resulting in poor surface flatness and high haze.

[Comparative Example 2]
Dissolve 50 parts by mass of polycarbonate resin (Teijin Chemicals Ltd. Panlite L-1225Y) having bisphenol A as a structural unit with stirring at 25 ° C. with respect to 50 parts by mass of methylene chloride and ethanol mixed solvent containing 2 parts by mass of ethanol. The dope was too viscous and solidified. For this reason, no fluid could be formed on the stainless steel belt, and no film could be formed.

[Comparative Example 3]
30 parts by mass of a copolymer polycarbonate resin (copolymer A) containing bisphenol A is dissolved with stirring at 25 ° C. with respect to 70 parts by mass of methylene chloride containing 9.8 parts by mass of ethanol and 70 parts by mass of an ethanol mixed solvent. A viscous dope was obtained. This dope was poured on a stainless steel belt peeled off at a place where the dew point was 0 degrees or less by blowing dry nitrogen, and peeled off after 230 seconds. The residual solvent at this time was 43 mass%. The peelability was good, and no peeling step or peeling streaks were found on the film surface. However, since the dew point was lowered too much, the charge was increased and discharge occurred between the film and the roll, and protrusions appeared on the film surface, resulting in poor surface flatness. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 116 μm.

[Comparative Example 4]
To 70 parts by mass of methylene chloride containing 7 parts by mass of ethanol and 70 parts by mass of an ethanol mixed solvent, 30 parts by mass of copolymer polycarbonate resin (copolymer B) containing bisphenol A is dissolved while stirring at 25 ° C. A good dope was obtained. This dope was poured on a stainless steel belt and peeled after 210 seconds at a temperature of 15 ° C. or higher without controlling the dew point. The residual solvent at this time was 41 mass%. The peelability was good, and no peeling step or peeling streaks were found on the film surface. However, because the dew point was high, when the film was peeled, the belt surface of the film was condensed due to the influence of latent heat due to evaporation of methylene chloride, and the film became cloudy due to the presence of pores. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 110 μm.

[Comparative Example 5]
30 parts by mass of polycarbonate resin (Teijin Chemicals Ltd. Panlite L-1225Y) containing bisphenol A as a structural unit was stirred at 25 ° C. with respect to 70 parts by mass of methylene chloride and ethanol mixed solvent containing 5.6 parts by mass of ethanol. The resulting solution was dissolved to obtain a transparent and viscous dope. This dope was poured on a stainless steel belt under an atmosphere in which the dew point was controlled at 7 ° C. by blowing dry air, and was peeled off after 300 seconds. At this time, the residual solvent was 20% by mass. Since the residual solvent at the time of peeling was as small as 20% by mass, electrification occurred at the time of peeling, and peeling steps, peeling stripes and the like were visually observed on the film surface. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 120 μm.

[Comparative Example 6]
30 parts by mass of a polycarbonate resin (Teijin Chemicals Ltd. Panlite L-1225Y) containing bisphenol A as a structural unit was stirred at 25 ° C. with respect to methylene chloride containing 3.5 parts by mass of ethanol and 70 parts by mass of an ethanol mixed solvent. The resulting solution was dissolved to obtain a transparent and viscous dope. This dope was poured on a stainless steel belt under an atmosphere in which the dew point was controlled at 6 ° C. by blowing dry air, and was peeled off after 100 seconds. The residual solvent at this time was 53 mass%. When it peeled, it fractured | ruptured and the film was not able to be produced.

[Comparative Example 7]
30 parts by mass of copolymer polycarbonate resin (copolymer A) containing bisphenol A is dissolved while stirring at 25 ° C. with respect to methylene chloride containing 1.4 parts by mass of ethanol and 70 parts by mass of an ethanol mixed solvent. A viscous dope was obtained. This dope was poured on a stainless steel belt in an atmosphere in which the dew point was controlled at 7 ° C. by blowing dry air, and was peeled off after 230 seconds. The residual solvent at this time was 42 mass%. However, since the proportion of ethanol was as small as 2 mass, the tension against peeling became very large, and peeling steps, peeling stripes and the like were visually observed on the film surface. It dried until the residual solvent density | concentration became 1 mass% or less. The film thickness was 114 μm.

[Comparative Example 8]
30 parts by mass of a copolymer polycarbonate resin (copolymer B) containing bisphenol A is dissolved while stirring at 25 ° C. with respect to 70 parts by mass of methylene chloride containing 11.2 parts by mass of ethanol and 70 parts by mass of an ethanol mixed solvent. A viscous dope was obtained. This dope was poured on a stainless steel belt under an atmosphere in which the dew point was controlled at 7 ° C. by blowing dry air, and peeled after 200 seconds. The residual solvent at this time was 42 mass%. However, since the ratio of ethanol was as large as 16 masses, dew condensation was remarkable when the film was peeled off, and voids opened on the belt surface of the film, resulting in cloudiness. The film thickness was 112 μm.

[Comparative Examples 9 and 10]
As described in Table 1, the polycarbonate resin, solvent, MA, dew point, residual solvent, time from stretching to peeling, and film thickness were changed, and the aromatic polycarbonate film of Comparative Examples 9 and 10 was changed in the same manner as Comparative Example 1. Produced.

  The composition, production conditions, productivity evaluation, surface roughness (Ra), and haze of the aromatic polycarbonate film sample are summarized in Table 1 below.

  In addition, the following evaluation was performed about productivity evaluation, surface roughness (Ra), and haze.

(productivity)
○: Productivity is high with no failures or defects. △: Slightly failures and defects and poor productivity. ×: Many failures and defects and poor productivity (Surface roughness (Ra))
JIS B 0601: 2001, the surface roughness (Ra) was measured using an optical interference type surface roughness meter RST / PLUS (manufactured by WYKO).

(Haze)
One film sample was measured according to ASTM-D1003-52 using T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd.

  It is clear that the aromatic polycarbonate film samples of Examples 1 to 13 of the present invention are excellent in productivity, surface roughness (Ra), and haze.

  Subsequently, the aromatic polycarbonate film produced in Examples 1-13 and Comparative Examples 1-10 (except Comparative Examples 2 and 6 which were not able to produce a film) was used as a plastic substrate, and a transparent conductive layer (ITO) was formed. Then, an organic EL (electroluminescence) element was produced on the transparent conductive film.

In order of CuPc (10 nm) / NPD (30 nm) / CBP: Ir (ppy) 33% by mass / Alq ₃ (50 nm) / LiF (0.5 nm) / Al (120 nm) on a polycarbonate film provided with an ITO conductive layer 100 nm. Then, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electrode were formed by vacuum deposition, and finally sealed in an N ₂ gas atmosphere.

<Evaluation of organic EL>
(Light emission unevenness)
Using a KEITHLEY source measure unit type 2400, a direct current voltage was applied to the organic EL element to emit light. With respect to the light-emitting element that emitted light at 200 cd, light emission unevenness was observed with a 50 × microscope.

Evaluation rank of light emission unevenness ◎: 90% or more emit light uniformly ○: 80% or more emit light uniformly △: 70% or more emit light uniformly ×: Less than 70% emit light uniformly Not (display defect)
The area of the display defect site when the organic EL element was made to emit light and displayed in white was evaluated according to the following rank.

◎: No display defect ○: Display defect is less than 1% in area △: Display defect is 1% or more and less than 3% in area ×: Display defect is 3% or more in area (voltage increase)
When driven at a constant current of 10 mA / cm ² , the initial voltage and the voltage after 150 hours were measured. The relative value of the voltage after 100 hours with respect to the initial voltage was defined as the voltage increase rate, and the following ranks were used.

A: 100 to 105
○: 106-115
Δ: 116-125
X: 125 or more (decrease in luminance)
The time required for the luminance to decrease to 90% of the initial luminance was measured, and this was used as an index of deterioration of the device at the initial stage as 10% attenuation time (τ0.9). The results were classified into the following ranks as relative values with Example 1 as 100.

A: 100
○: 90-99
Δ: 80-89
×: 79 or less (dark spot)
After each organic EL device was stored in an environment of 60 ° C. and 90% RH for 300 hours and 500 hours, 50-times magnified photographs were taken to visually observe the occurrence of dark spots and dark according to the following criteria. Spot resistance was evaluated.

A: No occurrence of dark spots was observed even after 500 hours. O: Generation of dark spots was not observed after storage for 300 hours, but slight dark spots were observed after storage for 500 hours. Δ: 300 hours Some dark spots are observed even after storage. ×: Many dark spots are observed after 300 hours storage.

  Luminescence was observed in all films other than Comparative Examples 4 and 8, but the organic EL using the aromatic polycarbonate film of the Comparative Example is a substrate having many strips and protrusions on the surface. Due to poor surface flatness, light emission unevenness, display defects, and a decrease in light emission luminance that increased voltage appeared. In addition, the resistance of the conductive layer is not uniform, and there is a problem that a dark spot is formed due to the concentration of charges from one point, thereby shortening the life.

  It was found that the aromatic polycarbonate film produced by the production method of the present invention has a very smooth surface, excellent light emission unevenness, display defects, voltage rise, and dark spots, and is very suitable for an organic EL substrate.

Claims (4)

A dope composition in which 15 to 45% by mass of an aromatic polycarbonate is dissolved in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 6 carbon atoms, the methylene chloride and the aliphatic A dope composition having an alcohol ratio (MA represented by the following formula (i)) of 4 to 14 is cast on an endless belt under an atmosphere in which the dew point is controlled to 0 to 15 ° C., and the following formula ( A method for producing an aromatic polycarbonate film, comprising peeling in a state where the residual solvent concentration represented by ii) is 35 to 45%.
Formula (i) MA = mass of aliphatic alcohol / (mass of aliphatic alcohol + mass of methylene chloride) × 100
Formula (ii) Residual solvent concentration (%) = solvent amount / (solvent amount + solvent mass) × 100 The method for producing an aromatic polycarbonate film according to claim 1, wherein a dope composition having a ratio (MA) of methylene chloride to aliphatic alcohol of 5 to 12 is used. The method for producing an aromatic polycarbonate film according to claim 1 or 2, wherein peeling is performed in an atmosphere in which the dew point of the peeling portion is controlled to 0 to 5 ° C. The method for producing an aromatic polycarbonate film according to any one of claims 1 to 3, wherein a time from casting on a belt to peeling is 120 to 270 seconds. .