JP5092904B2 - Method for producing transparent polycarbonate film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent polycarbonate film suitable as a film for an electro-optical device that has heat resistance, transparency and mechanical strength and is useful for an electro-optical component such as an organic electroluminescent device or the like, and to provide a method for producing the transparent polycarbonate film. <P>SOLUTION: The transparent polycarbonate film is a transparent film comprising a polycarbonate resin wherein the polycarbonate resin has a glass transition temperature of 200&deg;C or higher and the transparent film formed in thickness of 80 &mu;m has a haze value of less than 3.0. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a transparent polycarbonate film and a method for producing the transparent polycarbonate film.

  Various plastics have been proposed as films for electronic and optical devices. The required properties of these films include heat resistance, transparency, impact resistance, mechanical strength, low dielectric constant, etc. Polymethyl methacrylate, polycarbonate, polyarylate, polyethersulfone, polyimide as materials that satisfy these properties Etc. have been used. In recent years, with higher performance and smaller size of electronic / optical devices, further heat resistance and transparency have been demanded.

  However, for example, polymethylmethacrylate does not have sufficient heat resistance and impact resistance, and conventional polycarbonates and polyarylates cannot be said to have sufficient heat resistance when forming an electrical insulating layer. Polyethersulfone has a high heat resistance but is fading, and easily causes optical anisotropy even with a slight molecular orientation. Since polyimide has a high water absorption rate and causes a decrease in solder heat resistance due to water absorption, there is a problem that it is necessary to perform sufficient drying.

  On the other hand, an attempt has been made to obtain a polycarbonate having improved heat resistance, transparency, and mechanical strength by using compounds having various chemical structures as dihydric phenol as a raw material instead of conventional polycarbonate. .

  For example, Patent Documents 1 and 2 disclose an aromatic polycarbonate using a bisphenol derivative of adamantane as a dihydric phenol, but the aromatic polycarbonate has high heat resistance but is easy to crystallize. There is a problem that the solubility is poor, the moldability is inferior, and the transparency is lowered.

  Conventionally, a polycarbonate film is formed by a melting method. However, in the case of a high heat-resistant polycarbonate, the melting temperature becomes high due to its high glass transition temperature, and coloring and mechanical strength are increased. This causes problems such as deterioration of the resin such as lowering and lowering of flatness due to the die line. Therefore, in order to obtain a film having no problems such as coloring and flatness, film formation by a solution method can be considered instead of the melting method, but depending on the characteristics of the polycarbonate resin, there is a problem that the film becomes clouded (for example, patents) References 3, 4).

In addition, when melt-polymerized polycarbonate is formed into a solution, or a film obtained by dissolving a pellet formed by melt-kneading into a solvent and forming a solution has a problem of becoming cloudy.
JP 2005-68216 A JP 2005-206834 A JP 2002-328614 A JP-A-8-277360

  Therefore, in view of the above problems, the present invention provides a transparent polycarbonate film having heat resistance, transparency, and mechanical strength and suitable as a film for electronic / optical devices and a method for producing the same. The polycarbonate film is useful for electronic and optical parts such as organic electroluminescence.

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

  1. A transparent polycarbonate film comprising a polycarbonate resin, wherein the polycarbonate resin has a glass transition temperature of 200 ° C. or higher, and a haze value of the transparent film at a film thickness of 80 μm is less than 3.0.

  2. 2. The transparent polycarbonate film according to 1 above, wherein the polycarbonate resin has a weight average molecular weight of 10,000 or more and less than 100,000 and the content of a component having a weight average molecular weight of 1,000 or less is less than 1% by mass.

  3. 3. The method for producing a transparent polycarbonate film according to 1 or 2, wherein the polycarbonate is dissolved using a mixed solvent containing methylene chloride as a main solvent and at least one selected from the group consisting of ethanol, methanol, and THF as a secondary solvent. A method for producing a transparent polycarbonate film, characterized by forming a film by a solution casting method.

  4). 4. The method for producing a transparent polycarbonate film as described in 3 above, wherein a ratio of methylene chloride in the mixed solvent is 80 vol% or more and 99 vol% or less.

  ADVANTAGE OF THE INVENTION According to this invention, the transparent polycarbonate film suitable as a film for electronic and optical apparatuses which has heat resistance, transparency, and mechanical strength can be provided, and its manufacturing method. The polycarbonate film is suitable for electronic and optical parts such as organic electroluminescence.

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

  The transparent film made of the polycarbonate resin of the present invention is characterized in that the glass transition temperature of the polycarbonate resin is 200 ° C. or higher and the haze value at a film thickness of 80 μm of the transparent film is less than 3.0.

  As a result of intensive studies on the above problems, the present inventor has found that the cloudiness of the film generates a low molecular weight component having a weight average molecular weight of 1000 or less due to thermal decomposition at the time of synthesis of polycarbonate or at the time of melting. As a result, it became clear that it became cloudy because it scattered visible light. Therefore, this cloudiness becomes remarkable as the thickness of the film is increased.

  Therefore, the present inventor, if the transparent polycarbonate film satisfies the conditions described in claim 1 or claim 2, there is no generation of low molecular weight components due to thermal decomposition at the time of melting, and hence the haze is small, and the electronic / optical It has been found that a film with good quality having heat resistance, transparency and mechanical strength suitable for a film for equipment can be obtained. According to the production method of the present invention, even if the film thickness is increased to 250 μm, it does not become cloudy.

  Furthermore, the manufacturing method of the transparent polycarbonate film of Claim 3 and 4 is a polycarbonate using the specific mixed solvent containing at least 1 sort (s) chosen from three types, ethanol, methanol, and THF as a subsolvent, and methylene chloride as a main solvent. Is dissolved, and a film is formed by a solution casting method, whereby a transparent polycarbonate film having good heat resistance, transparency and mechanical strength of the present invention can be obtained.

  Hereinafter, the present invention will be described in detail.

(Aromatic polycarbonate)
The polycarbonate resin used in the present invention is not particularly limited as long as the glass transition temperature of the resin is 200 ° C. or higher and the haze value at a film thickness of 80 μm when formed into a film is less than 3.0. It is preferable to use the following aromatic polycarbonate resin.

  The polycarbonate resin has a glass transition temperature of 200 ° C. or higher in order to obtain a high heat resistant film, and preferably 230 ° C. or higher. These can be obtained by appropriately selecting the use ratio of the types of copolymerization components described below.

  The glass transition temperature can be measured with a DSC apparatus (differential scanning calorimetric analyzer). For example, the baseline is unevenly determined by a temperature rising condition of 10 ° C./min with RDC220 manufactured by Seiko Instruments Inc. It is the temperature that begins to do.

  The haze value can be measured with a commercially available haze meter. For example, the total light transmittance of a film adjusted to a film thickness of 80 μm is measured using COH-300A manufactured by Nippon Denshoku Industries Co., Ltd.

  In general, a polymer material generically called polycarbonate is a generic term that uses a polycondensation reaction in its synthesis method and has a main chain linked by a carbonic acid bond. Among these, a phenol derivative, It means the one obtained by polycondensation from phosgene, diphenyl carbonate and the like. Usually, an aromatic polycarbonate represented by a repeating unit having 2,2-bis (4-hydroxyphenyl) propane called bisphenol-A as a bisphenol component is preferably selected, and various bisphenol derivatives should be appropriately selected. Thus, an aromatic polycarbonate copolymer can be constituted.

  In addition to this bisphenol-A, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 1,1 -Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) -2-phenyl Ethane, 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 terephthalic acid and / or isophthalic acid components. By using such a structural unit as a part of the structural component of the aromatic polycarbonate composed of bisphenol-A, the properties of the aromatic polycarbonate, such as heat resistance and solubility, can be improved. The present invention is also effective for coalescence.

  Specific examples of the aromatic polycarbonate that can be used in the present invention include JP-A-6-16800, JP-A-10-77338, JP-A-10-130382, and JP-A-2002-328614. JP 2003-221986, JP-A 2003-212987, JP-A 2003-226746, JP-T 2004-534889, JP-T 2005-53682, JP-A 2005-68216, JP-A 2005 -206834, JP-A-2005-206836, JP-A-2006-131775, and the like, and examples thereof include compounds having a glass transition temperature of 200 ° C. or higher, and more specifically, the followings. However, it is not limited to these.

  The aromatic polycarbonate having a weight average molecular weight of 10,000 or more and less than 100,000 is preferably used. A weight average molecular weight of 20,000 to 60,000 is particularly preferred. If a resin having a weight average molecular weight lower than 10,000 is used, the mechanical strength of the resulting film may be insufficient, and if it has a high molecular weight of 100,000 or more, the viscosity of the dope becomes too large, which causes a problem in handling.

  In the present invention, the content of the component having a weight average molecular weight of 1000 or less in the polycarbonate resin to be used is preferably less than 1% by mass, particularly from the viewpoint of enhancing transparency. In order to control the content of a component having a weight average molecular weight of 1000 or less, it is preferable to use a resin having a high glass transition temperature, or to remove the low molecular weight component by reprecipitation treatment with methanol or ethanol.

  The weight average molecular weight can be measured by a commercially available high performance liquid chromatography or the like.

  For example, the weight average molecular weight (Mw) is measured using the following gel permeation chromatography (GPC).

  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 Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  In order to produce a transparent polycarbonate film, it is possible to form a film by either a melt casting method or a solution casting method, but from the viewpoint of suppressing an increase in low molecular weight components due to heat melting, a solvent is used. It is preferable to prepare a dope composition (hereinafter also simply referred to as a dope) by dissolving a resin and form a film by a solution casting method.

  The solvent used in preparing the dope composition is preferably a mixed solvent containing methylene chloride as the main solvent and at least one selected from the group consisting of ethanol, methanol, and THF as the auxiliary solvent. The methylene chloride ratio in the mixed solvent is preferably 80 vol% or more and 99 vol% or less in order to completely dissolve the aromatic polycarbonate.

  These alcohols 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 can provide particularly good peelability. As mentioned above, it is 1-20 vol% with respect to a methylene chloride, Preferably it is 4-12 vol%. When the addition amount is in the range of 4 to 12 vol% with respect to the amount of methylene chloride, the solubility of the solvent in the polymer and the dope stability are improved, and the effect of improving the peelability is increased.

  The solvent used in the dope composition is composed of at least one selected from the above-mentioned methylene chloride and ethanol, methanol, and THF, but other solvents can be used as long as the effects of the present invention are not impaired. The remaining solvent is not particularly limited as long as it dissolves the aromatic polycarbonate at a high concentration and is compatible with alcohol, and further has a low boiling point. For example, as a solvent having a solubility in aromatic polycarbonate, other solvents suitably used besides methylene chloride include halogen solvents such as chloroform and 1,2-dichloroethane, and hydrocarbon solvents such as toluene and xylene. Ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, and ether solvents such as ethylene glycol dimethyl ether and methoxyethyl acetate.

  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.

  The dope 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. However, since alcohol is a poor solvent as described above, there is a possibility of dope clouding due to polymer precipitation in the method of adding later as in the former, so there is a method of dissolving in a mixed solvent as in the latter. preferable.

  The dope composition containing the aromatic polycarbonate in the present invention depends on the cosolvent used and the molecular weight of the aromatic polycarbonate, but the amount of the solvent is 15 to 55% by mass with respect to 15 to 45% by mass of the aromatic polycarbonate. Furthermore, it is preferable to make it contain in 20-50 mass%. If the amount of solvent exceeds this, the stability of the solution will not be a problem, but the effective concentration of the aromatic polycarbonate will be low, so when the solution composition is used to form a film by the solution casting method, the solution viscosity is low and the external viscosity is low. Disturbance is likely to occur, and it is difficult to obtain surface smoothness. Conversely, if the amount of 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.

  After the dope composition is cast on a support, it is peeled from the support to form a web, and 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 step is a step of casting the dope smoothly, the pre-drying step is a step of evaporating and removing most of the solvent from the cast dope, and the post-drying step is a step of removing the remaining solvent.

  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. Examples of the support used include glass, metal substrates such as stainless steel and ferrotype, and plastic substrates such as polyethylene terephthalate. Needless to say, the material and surface state of the support also have a great influence on the peelability of the cast film. For example, in a substrate coated with Teflon (registered trademark) or the like 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 a very important factor in forming a transparent and smooth film from a dope. Although the solution viscosity depends on the polymer concentration, molecular weight, and type of solvent, 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 to uniformly discharge the dope 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.

  Although the temperature at the time of casting of this invention depends on the solvent composition used, it is 10 to 40 ° C., preferably 15 to 35 ° C. In order to obtain a film having excellent smoothness, it is necessary to cast and smooth the solution extruded from the die on the support. 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 during casting according to the present invention is preferably cast onto the endless belt in an atmosphere in which the dew point is controlled to 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 condensation portion on the surface, and in an atmosphere exceeding 25 ° C., the film is entirely whitened, and the film may be broken and fractured 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 shifting 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 drying step, it is necessary to evaporate and remove the solvent from the dope cast on the support 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 drying efficiency should be increased by increasing the temperature sequentially or continuously. 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 contained in a high concentration, foaming occurs when the temperature is higher than that, which is not preferable. 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 support and is peeled off from the support 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, the cast film cast from the dope composition has high adhesion to the support and the peelability is poor. Therefore, stress distortion, peeling muscles, and peeling flaws occur. Accordingly, the residual solvent amount is an important factor, and preferably the residual solvent concentration represented by the following formula (i) is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Yes, particularly preferably 20 to 30% by mass or 70 to 120% by mass.

Formula (i) 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 attaches to the surface, which starts to work like an adhesive layer, etc. It is estimated. 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 can be favorably maintained without such work.

  In order to produce the transparent polycarbonate film of the present invention, it is preferable that the web is peeled from the metal substrate and then the width of the web is maintained or stretched in a state where the residual solvent concentration is 0.5 to 35%. It is preferable to use a tenter method for maintaining the width, and the stretching is preferably performed using a longitudinal stretching device when stretching in the transport direction (= long direction or longitudinal direction), and when stretching in the width direction. It is preferable to carry out by a tenter method in which the web is gripped with a clip or the like.

  The stretching operation may be carried out in multiple stages. Biaxial stretching may be performed in the casting direction and the width direction, or the stretching may be performed in an oblique direction using an oblique stretching apparatus. Moreover, when extending | stretching, you may carry out at once and may implement in steps. 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.

  Further, the “stretch direction” in the present invention is usually used to mean a direction in which a stretching stress is directly applied when performing a stretching operation, but in the case of being biaxially stretched in multiple stages, In some cases, it is used in the sense of the one having a higher draw ratio (that is, the direction usually serving as the slow axis).

  The stretching ratio of the film is preferably 1.01 to 3 times, more preferably 1.1 to 2 times with respect to the casting direction, the width direction or the oblique direction. When stretching in the biaxial direction, the side to be stretched at a high magnification is 1.01 to 3 times, preferably 1.1 to 2 times, and the stretching ratio in the other direction is 0.8 to 1.5. The film can be stretched by a factor of preferably 0.9 to 1.2.

  Next, the post-drying step is a step of further drying the film peeled off from the substrate so that the residual solvent concentration is 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 finally a large amount of residual solvent, deformation occurs over time, or dimensional change, so-called thermal shrinkage, occurs when heat is applied in a subsequent processing step such as a display device. In general, in the post-drying process, industrially, a method of drying while transporting the film by a roll suspension method or the like is adopted. However, in these methods, various forces are applied to the film during the drying. Therefore, the drying temperature must be selected from a range where deformation of the film does not occur in the production of a film that requires optically high homogeneity, such as a display device. Generally, when the glass transition temperature of the aromatic polypolycarbonate used is Tg (° C.), the range is (Tg−120 ° C.) to Tg, preferably (Tg−100 ° C.) to (Tg−10 ° C.). To be elected. 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 pre-drying step.

  In the present invention, when the transparent polycarbonate film is produced, 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 drying thermal energy and recovery efficiency. The oxygen concentration in the inert gas atmosphere is preferably 10% by volume or less.

  The thickness of the transparent polycarbonate 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 a plastic substrate and a raw film for an optical film constituting a display device. If it is the thickness of this range, it is easy to remove a residual solvent and generation | occurrence | production of thickness spots can also be suppressed and it is preferable.

<Display device>
The transparent polycarbonate film of the present invention has excellent flatness and is used for films for various electronic / optical devices such as plasma displays, field emission displays, organic EL displays, inorganic EL displays, and electronic paper.

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

  The organic EL element has a transparent electrode disposed on the inside 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 between them. 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 element, for example, a substrate (including a patterned transparent conductive layer and an auxiliary electrode layer) using the transparent polycarbonate film of the present invention / hole injection layer / hole transport layer / light emitting layer / electron. The layer structure which consists of an 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 transparent polycarbonate film of the present invention can be applied to the outside of the glass substrate, or the transparent polycarbonate film of the present invention can be used instead of the glass substrate. If the two glass substrates are both replaced with the transparent polycarbonate film of the present invention, the entire display can be made flexible.

  As a method of forming the transparent conductive layer, a sputtering method is mainly used, and a direct current sputtering method, a high frequency magnetron sputtering method, an ion beam sputtering method, and the like can be applied. From the viewpoint of productivity, the magnetron sputtering method is preferable. The film thickness of the transparent conductive layer is preferably 10 to 1000 nm in order to obtain sufficient conductivity. The transparent polycarbonate film of the present invention preferably has a total light transmittance of 80% or more in the visible light region, more preferably 85% or more, and particularly preferably 90% or more. If it is less than 80%, problems such as a reduction in visibility may occur.

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

<Synthesis of polycarbonate>
Polycarbonate PC-1-6 was produced by the interfacial polymerization method at the following monomer ratio.

(Synthesis of PC-1)
By the interfacial polymerization method, a polycarbonate in which the bisphenol component consists only of 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as BisA) was synthesized.

  The obtained polycarbonate was heated at 25 ° C. to 350 ° C. under a nitrogen stream (20 ml / min) at a temperature rising rate of 10 ° C./min using DSC220, and then immediately cooled immediately to obtain a sample. The glass transition temperature was measured according to JIS K 7121 at the same rate of temperature increase. As a result, the glass transition temperature of this polycarbonate was 154 ° C.

  Moreover, as a result of measuring the weight average molecular weight of the said polycarbonate according to the following measuring method, it was 60000, and content of the component of the weight average molecular weight 1000 or less was 4 mass% from the profile.

  The weight average molecular weight Mw was measured using the following gel permeation chromatography (GPC) to confirm the removal of low molecular weight components.

  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 Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples were used at approximately equal intervals.

(Synthesis of PC-2)
Similarly to PC-1, a polycarbonate was synthesized in which the bisphenol component was BisA: 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (hereinafter referred to as BCF) = 40: 60 (molar ratio). (PC-2A).

  The glass transition temperature of PC-2A measured in the same manner as PC-1 is 220 ° C. The weight average molecular weight of PC-2A is 40000, and the content of components having a weight average molecular weight of 1000 or less is 1.5% by mass. there were.

  Further, reprecipitation treatment with ethanol was performed so that the low molecular weight component ratio of the polycarbonate was less than 1% by mass shown in Table 1, and the low molecular weight components were removed (PC-2B, PC-2C).

(Synthesis of PC-3)
A 500 ml Morton flask was charged with 18.9 g (50 mmol) of fluorenylidene-9- (bis-3-methyl-4-hydroxybenzene) (referred to as DMBPF), 90 ml of methylene chloride and 90 ml of water. The pH was adjusted to 11.5 with 50% by weight NaOH. Phosgene is added at 0.6 g / min, p-cumylphenol (0.43 g, 4 mol%) is added at 5.0 g (50 mmol), and 6.0 g (20 mol% excess) is added. The addition of phosgene was continued. The pH dropped to 10.5 (due to phosgene), but at this point 50 μL of triethylamine (TEA) was added and after 3 minutes an additional 50 μL of TEA was added. After the chloroformate disappeared, an additional 2.25 g of phosgene was added. The reaction mixture was tested for the presence of chloroformate. When present, it was hydrolyzed by adding dimethylbutylamine (DMBA) (5 μL). The polymer solution was separated from the brine, washed with aqueous HCl, washed with water, and steam agglomerated in a blender. Similarly, the content of components having a weight average molecular weight of 32,000 and a weight average molecular weight of 1,000 or less was 0.1% by mass. The glass transition temperature was 240 ° C.

(Synthesis of PC-4)
51 g of 2,2-bis (4-hydroxyphenyl) adamantane represented by the following formula (A) and 19 g of 1,1-bis (4-hydroxyphenyl) cyclohexane represented by the following formula (B) were added at 2 mol / liter. 700 ml of methylene chloride was added to a solution dissolved in 1,360 ml of a potassium chloride aqueous solution having a concentration, and phosgene gas was blown into the liquid at a rate of 950 ml / min for 30 minutes under cooling. This reaction solution was allowed to stand to obtain an oligomeric methylene chloride solution having a degree of polymerization of 2 to 5 in the organic phase and having a chloroformate group at the molecular end.

  Methylene chloride was added to 110 ml of the resulting methylene chloride solution to make a total volume of 150 ml, and then a solution of 3 g of 2,2-bis (4-hydroxyphenyl) adamantane dissolved in a 2 mol / liter aqueous potassium chloride solution was added thereto. In addition, 0.2 g of p-tert-butylphenol was added as a molecular weight regulator. Next, while vigorously stirring the reaction solution, 1 ml of a 7% strength triethylamine aqueous solution was added as a catalyst and reacted at room temperature for 1 hour.

  After completion of the reaction, the resulting reaction product was diluted with 200 ml of methylene chloride and washed twice with 100 ml of water. The obtained organic phase was put into methanol and purified by reprecipitation to obtain a white powder of polycarbonate copolymer.

  The chemical structure confirmed by 1H-NMR spectral analysis was a polycarbonate having a composition ratio of 70:30 consisting of the following repeating units.

  Similarly, the content of the component having a weight average molecular weight of 55000 and a weight average molecular weight of 1000 or less was 0.2% by mass. The glass transition temperature was 265 ° C.

(Synthesis of PC-5)
To a solution prepared by dissolving 45 g of 2,2-bis (4-hydroxyphenyl) adamantane (dihydric phenol (A)) and 45 g of dihydric phenol (B) having the following structure in 1360 ml of a 2N aqueous potassium hydroxide solution, While adding 700 ml of the solvent methylene chloride and stirring, phosgene gas was blown into the liquid at a rate of 950 ml / min for 30 minutes under cooling. Subsequently, this reaction liquid was left and separated to obtain a methylene chloride solution of an oligomer having a degree of polymerization of 2 to 5 in the organic layer and having a chloroformate group at the molecular end.

  Then, after adding methylene chloride to 110 ml of the obtained methylene chloride solution to make the total amount 150 ml, a solution prepared by dissolving 9 g of the dihydric phenol (B) in 50 ml of 2N potassium hydroxide aqueous solution was added thereto, Further, 0.2 g of p-tert-butylphenol was added as a molecular weight regulator. Subsequently, 1.0 ml of a 7% strength triethylamine aqueous solution was added as a catalyst while vigorously stirring the mixture, and the mixture was reacted at 25 ° C. for 1.5 hours with stirring.

  After completion of the reaction, the obtained reaction product was diluted with 1 liter of methylene chloride and washed twice with 1.5 liter of water. Then, after washing with 0.05 N hydrochloric acid, it was further washed twice with 1 liter of water. The obtained organic phase was put into methanol and purified by reprecipitation to obtain a polycarbonate copolymer powder.

  As a result of structural confirmation by 1H-NMR spectrum analysis, the obtained polycarbonate was found to have a chemical structure consisting of the following repeating units. The molar ratio of the following repeating units (A) :( B) was 60:40.

  Further, the polycarbonate obtained above had a weight average molecular weight of 85,000 and a content of components having a weight average molecular weight of 1000 or less was 0.2% by mass. The glass transition temperature was 285 ° C., and it was confirmed that the glass transition temperature was extremely high.

(Synthesis of PC-6)
To a solution obtained by dissolving 75 g of 2,2-bis (4-hydroxyphenyl) adamantane (dihydric phenol (A)) in 1,360 ml of 2N aqueous potassium hydroxide solution, 700 ml of methylene chloride as a solvent was added and stirred. Under cooling, phosgene gas was blown into the liquid at a rate of 950 ml / min for 30 minutes. Subsequently, this reaction liquid was left and separated to obtain a methylene chloride solution of an oligomer having a degree of polymerization of 2 to 5 in the organic layer and having a chloroformate group at the molecular end.

  Then, methylene chloride was added to 110 ml of the obtained methylene chloride solution to make the total amount 150 ml, and then 6.2 g of dihydric phenol (C) having the following structure was dissolved in 50 ml of 2N aqueous potassium hydroxide solution. Then, 0.2 g of p-tert-butylphenol was added as a molecular weight regulator. Next, 1.4 ml of a 7% strength triethylamine aqueous solution was added as a catalyst while vigorously stirring the mixture, and the mixture was reacted at 25 ° C. for 1.5 hours with stirring.

  After completion of the reaction, the obtained reaction product was diluted with 0.5 liter of methylene chloride and washed twice with 0.5 liter of water. Next, after washing with 0.01 N hydrochloric acid, it was further washed twice with 0.5 liter of water. The obtained organic phase was put into methanol and purified by reprecipitation to obtain a polycarbonate copolymer powder.

  As a result of structural confirmation by 1H-NMR spectrum analysis, the obtained polycarbonate was found to have a chemical structure consisting of the following repeating units. The molar ratio (A) :( C) of these repeating units was 85:15.

  The polycarbonate obtained above had a weight average molecular weight of 26000 and a content of components having a weight average molecular weight of 1000 or less was 0.1% by mass. When the glass transition temperature was measured in the same manner, it was 295 ° C., and it was confirmed that the glass transition temperature was extremely high.

<Production of polycarbonate film>
Dopes were prepared from the synthesized polycarbonates PC-1 to PC-6 using methylene chloride as the main solvent and the solvents shown in Table 1 and the subsolvents in the ratios. This was poured on a glass plate so that the film thickness after drying was 80 μm, and after peeling, it was dried at 120 ° C. for 60 minutes to obtain a polycarbonate film.

<Evaluation>
(Measure haze)
A haze meter (turbidity meter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) was used. The light source was measured in accordance with JIS K-7136 using a 5V9W halogen bulb, and the light receiving part using a silicon photocell (with a relative visibility filter).

(transparency)
The total light transmittance was measured using COH-300A manufactured by Nippon Denshoku Industries Co., Ltd., and evaluated according to the following criteria.

◎ 90% or more ○ 88 or more to less than 90% △ 86 or more to less than 88% × less than 86% (heat resistance)
Dimensional change rate: A film having a size of 10 cm in length and breadth was cut out, the length before and after heat treatment at 200 ° C. for 1 hour was measured accurately with a micrometer, and the shrinkage change rate before and after heating was calculated. This was evaluated according to the following criteria.

◎ 0 to less than 0.05% ○ 0.05 or more to less than 0.1% △ 0.1 or more to less than 0.2% x 0.2% or more Table 1 shows the above evaluation results.

  From Table 1, it is clear that the polycarbonate films 3 to 13 of the present invention are films excellent in transparency and heat resistance.

Example 2
<Production of organic EL element>
A transparent conductive layer was formed on the polycarbonate film produced in Example 1 by a photolithography method to obtain a display electrode. Next, TPD (N, N′-bis (3-methylphenyl) 1,1′-biphenyl-4,4′-diamine) which is a triphenylamine derivative as a hole transport layer is formed on the transparent electrode by vacuum deposition. Next, Alq ₃ (tris- (8-hydroxyquinoline) aluminum) was deposited as a light emitting layer to a thickness of 50 nm. Furthermore, magnesium and silver were vapor-deposited on this to a thickness of 200 nm to form an organic EL layer as a metal electrode. Subsequently, using the same film as the polycarbonate film on which the EL layer is formed, an ultraviolet curable sealant is applied on the surface on which the transparent conductive layer is formed, and then the organic EL layer is formed as described above. The organic EL layer was sealed by ultraviolet irradiation. Next, when a voltage was applied to the organic EL device to confirm the degree of light emission and the lifetime, the organic EL device using the polycarbonate films 3 to 11 of the present invention has high luminance, and the luminance can be maintained over a long period of time. I understood. Since the organic EL element using the polycarbonate film 1 of the comparative example has high haze and inferior heat resistance, it has a low luminance and a short life. Moreover, it turned out that the organic EL element using the polycarbonate film 2 of a comparative example has high haze and low brightness.

Claims (6)

A transparent film made of a polycarbonate resin, wherein the polycarbonate resin has a glass transition temperature of 200 ° C. or higher, and a transparent polycarbonate film having a haze value of less than 3.0 at a film thickness of 80 μm. , polycarbonate resin reprecipitation process, have rows in the removal of weight average molecular weight of 1000 or less of a low molecular weight component of polycarbonate resin, transparent polycarbonate, characterized in that controlling the content of the low molecular weight component to below 1% by weight A method for producing a film.   The manufacturing method according to claim 1, wherein the reprecipitation treatment is a reprecipitation treatment with methanol or ethanol.   After the reprecipitation treatment, the polycarbonate resin is dissolved using methylene chloride as a main solvent and a mixed solvent containing at least one selected from the group consisting of ethanol, methanol, and THF as a sub solvent, and a film is formed by a solution casting method. The manufacturing method according to claim 1 or 2. The manufacturing method of Claim 3 whose methylene chloride ratio in the said mixed solvent is 80 vol% or more and 99 vol% or less. The manufacturing method of any one of Claims 1-4 whose glass transition temperature of the said polycarbonate resin is 230 degreeC or more. The manufacturing method of any one of Claims 1-5 whose weight average molecular weights of the said polycarbonate resin are 10,000 or more and less than 100,000.