JP4782549B2 - Method for producing polycarbonate film - Google Patents

Description

  The present invention relates to a thin-walled polycarbonate film used as a light transmission layer of an optical disc that records, reproduces, and erases information by laser light or the like. The present invention also relates to a method for producing a polycarbonate film, in which a light transmission layer film of the optical disc is produced by a melt film forming method.

<Optical recording layer and light transmission layer>
Polycarbonate resins are widely used in optical applications because of their excellent transparency, impact resistance, heat resistance, dimensional stability, and processability. For example, optical disks that use laser light have been variously researched, developed, and commercialized as high-density, large-capacity recording media. Various technologies have been developed that enable large-capacity storage including moving image information on an optical disc. As one of them, a technique of a film surface incidence type optical disk for reading information from one side has been proposed, and Patent Document 1, Non-Patent Documents 1 and 2, and the like have been published.

The film surface incidence type optical disc is a high-density recording medium provided with an optical recording layer in the form of a disc mainly formed of polycarbonate resin as described in the above-mentioned literatures. Is formed on a disk surface having a thickness of about 0.6 to 1.1 mm. Further, in order to protect the optical recording layer, a film having a thickness of about 0.01 to 0.1 mm is attached (adhered) to the optical recording layer as an optical transmission layer with an adhesive or the like.
In the present invention, the signal recording layer of the optical disk is referred to as an optical recording layer, and a thin film for protecting the optical recording layer is referred to as a light transmission layer film.

<Light transmission layer>
Conventionally, a melt film forming method or a solution film forming method has been adopted as a method for producing a polycarbonate resin film.
In Patent Document 2, a resin sheet produced by a melt casting method (substantially a solution casting method) is used as a light transmission layer, polycarbonate is used as one of the resins, A method of manufacturing an optical recording medium using a material having controlled birefringence and residual solvent has been proposed.

  Patent Documents 3 and 4 describe that a film for a light transmission layer is produced by a solution casting method using polycarbonate. Here, the film thickness, thickness variation, thermal dimensional change rate, total light transmittance, solvent content, in-plane retardation, maximum value of retardation K in the thickness direction, surface roughness, and the like are defined.

  According to the solution casting method, there is an advantage that an excellent film quality can be obtained as a film for an optical recording layer. However, the solution casting method is a casting method in which a polycarbonate resin is cast on a support surface as a methylene chloride solution. Therefore, in the drying process, much energy is consumed for evaporating and removing methylene chloride, and the apparatus has to be increased in size. And, since heat treatment is carried out while transporting a relatively soft film containing the solution, surface defects such as scratches and transfer scratches are likely to occur due to transfer of scratches and defects on the surface of the support and the transport roll. There are also problems in quality control, such as it is difficult to eliminate the problem in terms of equipment and operation.

  On the other hand, the melt-extruded polycarbonate film obtained by the melt film-forming method has several technical problems in production, for example, it is difficult to sufficiently reduce birefringence, the thickness unevenness is not sufficiently good (not small), and the surface At present, satisfactory characteristics cannot be obtained because problems such as many defects cannot be solved.

<About solution casting method>
In addition, further increase in the density of optical disks is being promoted. For example, in the case of an optical disc having two optical recording layers, a light transmission layer film of about 50 μm and about 100 μm is used. The 50 μm light transmission layer film is used for the inner layer portion of the optical disc, and the 100 μm light transmission layer film is used for the surface layer portion of the optical disc.

  However, the solution casting method using methylene chloride as a solvent has limitations in terms of the thickness of the polycarbonate film that can be produced. That is, when a solution film is formed using polycarbonate, there is a problem that polycarbonate (particularly bisphenol A-PC) is crystallized during the drying process of the solvent, making it difficult to obtain a transparent and flexible film.

  If a film is to be produced from a methylene chloride solution of bisphenol A-PC (viscosity average molecular weight of 15,000) used as an optical disk substrate, it is difficult to produce a thick transparent film of 50 μm or more. From this result, it was found that it is difficult to produce a film that covers all the films having a thickness of about 10 to 150 μm as required in the present invention by the solution casting method. . As described above, even with the solution casting method, there is still a problem to clear the above-mentioned film quality problems and to efficiently produce a film for a light transmission layer of an optical disk. is there.

  On the other hand, the melt film-forming method has an advantage that a highly transparent film can be easily produced because the melted bisphenol A-PC is formed into a film and rapidly cooled to prevent crystallization from the molten state.

<Technical issues related to conventional melt film-forming methods>
However, in order to use the film of the melt film-forming method obtained by the conventional method for the film for the light transmission layer, (i) the problem that foreign matter and surface defects are likely to occur, (ii) the thickness unevenness is not sufficiently small, In addition, there is a technical problem that (iii) a film having a sufficiently small birefringence and retardation is not obtained with a wide and long (large format) film.

(I) Foreign matter / surface defects Polycarbonate resins generally have a high melt viscosity, and are susceptible to foreign matter defects due to the long residence time and high extrusion temperature of the resin in the extruder. As a result of analyzing the defects of a 150 μm-thick transparent film obtained by melt-forming a commercially available bisphenol A-PC resin having a viscosity average molecular weight of 23,000, the size of the defects is about 20 to 50 μm. The number of heat-degraded products of polycarbonate (colored brown to black) was 60% in number, 30% of fine fragments of metal and glass, and 10% of the keratin of the human body. Metals and glass fragments can be removed if sufficient measures are taken on the raw materials used before synthesizing the polymer, and the stratum corneum of the human body can be removed by increasing the degree of cleanliness of the film forming apparatus and the person working there. However, once the thermal degradation product of polycarbonate, which occupies most of the foreign matter, is generated sporadically in the product film, it is difficult to remove. One of the problems is to develop a technique for forming a film without generating heat-deteriorated foreign matter in a polycarbonate light transmission film. In addition, surface defects such as cooling roll surface scratches and transfer roll surface scratches transferred to a film increase the cleanliness of the film forming chamber and reduce roll surface scratches and deposits as much as possible. Can be solved.

Non-Patent Document 3 describes thermal stability during molding of polycarbonate resin. Here, it is described that when water is present at the time of melt extrusion, it undergoes hydrolysis and the molecular weight is remarkably lowered, and when the resin is retained at a high temperature, it is thermally decomposed while generating carbon dioxide gas. . The molding processing temperature of ordinary polycarbonate for preventing these heat deteriorations as much as possible is 260 to 320 ° C., except that in the case of high-purity polycarbonate used for optical applications such as a compact disk (CD), 360 to It is described that it may be molded under a high temperature condition such as 350 ° C. Polycarbonate has a tendency to oxidize and yellow when contacted with oxygen in the air at high temperatures, and when it remains in that state for a long time, brown carbide is formed. Therefore, it is avoided that the polycarbonate stays at high temperatures for a long time. What should be done is clarified.
However, even if such basic results are known, it has not been clarified how to prevent the generation of thermally deteriorated materials.

(Ii) Thickness unevenness There are roughly two types of thickness unevenness in the melt-extruded film of bisphenol A-PC. One is a large wavy thickness unevenness when viewed in the width direction of the running direction, and the width is about 1 m. When a film having an average thickness of several tens of μm is examined, a film having a difference (difference R between the maximum value and the minimum value) of several μm or more can be seen.

  The other is a fine streaky defect (the present inventors may call this a die or lip). If there is a scratch on the edge of the extrusion die, it becomes a relatively strong continuous line on the film surface. However, even when melt extrusion is performed using a die in which the lip edge is sufficiently maintained and the lip is not damaged, minute streaks in the running direction may be visually detected. In many cases, such fine streaks cannot be detected by a continuous thickness meter that continuously contacts the film surface and measures the thickness. However, when a parallel ray is projected on the film surface from an oblique direction while changing the angle, and projected on a screen and visually observed, a streaky defect can be clearly seen. The streaks seen in this way are extremely small with a height of about 0.2 μm (200 nm) or less.

  In the melt film forming method, as a method for closely attaching a film to a cooling roll and cooling and solidifying, a method of producing a film in a state of low birefringence by properly combining a resin temperature, an air gap, and a cooling roll temperature is disclosed. For example, in Patent Document 5, in order to obtain a predetermined birefringence within a polycarbonate film thickness range of 0.02 to 2.0 mm, the melt extrusion molding conditions are (i) a resin temperature of 300 to 330 ° C., and (ii) air. It is shown that the gap is 80 to 100 mm and (iii) the cooling roll temperature is 100 to 140 ° C.

Further, according to Patent Document 6, as a method for producing a polycarbonate film used for an electrode substrate for a liquid crystal display panel, a method in which both ends of the film are brought into close contact with and / or pressure bonded to a cooling drum is shown.
However, the polycarbonate film obtained by the melt extrusion film-forming method of these polycarbonates has a small retardation value to some extent, but has a large retardation value and is not suitable as a light transmission layer film of an optical disk.

(Iii) Re reduction technique In the melt film-forming method, a technique for obtaining a film having a small retardation (birefringence) has been proposed.
Patent Document 7 discloses a method for producing a non-optical rotatory thermoplastic resin film characterized in that, in extrusion molding of an amorphous thermoplastic resin, the film is electrostatically applied and closely fixed on a cooling roll. Yes. And when this technique is implemented, it is described that an electrostatic wire is used as an electrode.

In Patent Document 8, a polycarbonate resin having a viscosity average molecular weight in the range of 14,000 to 19,000 is melt-extruded to usually have a thickness of about 0.1 to 3 mm, and the birefringence in the extrusion width direction is 40 nm or less. A manufacturing method for obtaining the sheet has been proposed.
Furthermore, in patent document 9, it consists of a polycarbonate resin whose viscosity average molecular weight is 14,000-19,000, birefringence is 20 nm or less, a curvature rate is 0.5% or less, and thickness is 0.1-1 mm. A method for producing an optical polycarbonate resin sheet is described.

  However, these techniques cannot stably produce a film having low retardation (birefringence) that is uniform in the width direction to the extent that it can be used for a light transmission layer. That is, the retardation is larger at both ends in the width direction of the film than at the center. It is presumed that the phenomenon that the retardation at both ends is high is that the molten resin flowing down from the die lip flows so that the width is narrowed at both ends, and in this state, the polymer is easily flow-oriented.

Japanese Patent Laid-Open No. 08-235638 Single-sided 12 Gbyte high-capacity optical disc Oplus E, 20 volumes, no. 2, 183 pages (February 1998) Optical Discs and Peripheral Materials 98-2 Polymer Optoelectronics Research Meeting Abstracts Polymer Electronics Society of Japan (January 22, 1999) Japanese Patent Application Laid-Open No. 2002-074749 JP 2001-243658 A JP 2001-243659 A Polycarbonate resin handbook, 401 pages, published by Seiichi Honma, August 28, 1992 Published by Nikkan Kogyo Shimbun Japanese Patent Laid-Open No. 04-275129 Japanese Patent Laid-Open No. 08-171001 JP-A-60-214922 Japanese Patent Laid-Open No. 04-166319 JP-A-10-217313

  An object of the present invention is to provide a film having physical properties and optical characteristics preferable as a light transmission layer film of an optical disc and a method for producing such a polycarbonate film.

  In order to achieve this object, the present inventors have intensively studied the melt film-forming method of a polycarbonate film. As a result, a polycarbonate film having good physical properties and optical characteristics, particularly as a light transmission layer film for an optical disk, has been obtained. The present inventors have found a melt extrusion method to produce and have reached the present invention.

That is, according to the present invention,
1. A film obtained by obtaining a polycarbonate resin film by any of the following methods (A) to (B) , and heat-treating the obtained polycarbonate resin film under the following conditions (1) to (3): Thickness is 10 to 150 μm, thickness variation is ± 2 μm or less, thermal dimensional change after heat treatment at 140 ° C. for 1 hour is 0.08% or less, total light transmittance is 89% or more, in-plane retardation is 1 to 15 nm, A method for producing a polycarbonate resin film having a thickness direction retardation of 100 nm or less and a centerline average surface roughness of 1 to 5 nm on both sides,
(A) A method in which a polycarbonate resin is melt-extruded from a die into a film, an air gap between the die and a cooling roll is 10 to 30 mm, and the entire surface of the film is closely adhered to the roll by an electrostatic adhesion method. More melt-extruded into a film, the air gap between the die and the cooling roll is 10 to 30 mm, a liquid thin film is applied to the surface of the cooling roll, and the molten film is extruded onto the thin film to adhere to the roll and cool ( 1) Heat treatment temperature; (Tg-10) to Tg (where Tg is the glass transition temperature of the polycarbonate resin)
(2) Heat treatment tension: 0.5 to 3 Kg / square centimeter as film cross-sectional load (3) Heat treatment time: 30 seconds or more
2 . A polycarbonate resin film is obtained by the following method (C) , and the obtained polycarbonate resin film is heat-treated under the following conditions (1) to (3). The thickness of the film is 10 to 150 μm, Thickness variation is ± 2 μm or less, thermal dimensional change rate after heat treatment at 140 ° C. for 1 hour is 0.08% or less, total light transmittance is 89% or more, in-plane retardation is 1 to 15 nm, thickness direction retardation is 100 nm Hereinafter, a method for producing a polycarbonate resin film having a center line average surface roughness in the range of 1 to 5 nm on both sides,
(C) A method in which a polycarbonate resin is melt-extruded from a die into a film shape, the air gap between the die and the cooling roll is 40 to 150 mm, the molten film is extruded, and both ends of the film are in close contact with the cooling roll and cooled (1) Heat treatment Temperature; (Tg-10) to Tg (where Tg is the glass transition temperature of the polycarbonate resin)
(2) Heat treatment tension: 0.5 to 3 Kg / square centimeter as film cross-sectional load (3) Heat treatment time: 30 seconds or more
3 . 3. The method for producing a film made of polycarbonate resin according to item 1 or 2 , wherein the polycarbonate resin is a polycarbonate resin obtained from a dihydroxy component having at least 50 mol% of bisphenol A.
4 . The method for producing a polycarbonate resin film according to item 1 or 2 , wherein the polycarbonate resin has a viscosity average molecular weight in the range of 14,000 to 30,000,
5 . Obtaining a polycarbonate resin film by the production method according to 1 or 2 above, and laminating and winding up the obtained polycarbonate resin film,
6 . The method for producing a polycarbonate resin film according to the preceding item 1 or 2 , wherein the heat treatment step is a heat treatment step using a roll-suspended heat treatment machine,
Is provided.

The polycarbonate film obtained by the method for producing a polycarbonate resin film of the present invention has small thickness unevenness and a retardation as small as 15 nm over the entire width direction of the film. A film for a liquid crystal display panel electrode substrate, a photoconductive photoreceptor electrode Suitable as a film for substrates, a film for electrode substrates for planar heating elements, a film for organic EL electrode substrates, a film for non-stretched film of retardation film, a film for light transmission layer for optical disks, especially for optical disks It is suitable as a film for a transmission layer.

<Optical recording layer>
Optical recording layers in optical discs include a ROM type that can only be read, a WORAM type that can only read and write, and a rewritable type that can read, write, and erase. The ROM type is a CD, CD-ROM or video disc that uses a light reflecting film such as a dielectric or AL, and the write type is a CD-R or a general write-once disc that uses an inorganic material such as an organic dye or Te. The rewritable type includes a magneto-optical recording medium represented by TbFeCo and a phase change recording medium represented by GeTeSb. However, the optical recording layer of the optical disk used in the present invention is not limited to these materials.

  Further, as the resin for the optical disk substrate, a polycarbonate resin having a viscosity average molecular weight of about 15,000 is often used. This is one in which the molecular weight of a polycarbonate resin (generally a polycarbonate resin obtained from bisphenol A) is lowered to improve the fluidity at the time of melting. Therefore, the optical distortion and birefringence caused by the flow orientation of the resin can be reduced, and the recorded signal can be finely engraved (the signal is less deteriorated due to the movement of molecules due to creep after the signal transfer). have.

<Light transmission layer>
The present invention is a polycarbonate film for protecting the optical recording layer of the optical disc and for use as a light transmission layer.

The polycarbonate resin is usually obtained by reacting a dihydroxy component and a carbonate precursor by an interfacial polymerization method or a melt polymerization method. Representative examples of the dihydroxy component include 2,2-bis (4-hydroxyphenyl) propane (commonly referred to as bisphenol A), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2- Bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis ( 4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis {(4-Hydroxy-3-methyl) phenyl} fluorene and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenze Etc. The. These dihydric phenols can be used alone or in admixture of two or more. Among these, a carbonate precursor, which is a polycarbonate resin obtained from a dihydroxy component having preferably at least 50 mol%, more preferably at least 60 mol%, more preferably at least 75 mol%, particularly preferably at least 90 mol% of bisphenol A. For example, carbonyl halide, carbonate ester or haloformate can be used, and specific examples include phosgene, diphenyl carbonate or dihaloformate of dihydric phenol.

  In producing polycarbonate resin by reacting the above dihydric phenol and carbonate precursor by interfacial polymerization method or melt polymerization method, a catalyst, a terminal terminator, a dihydric phenol antioxidant, etc. are used as necessary. May be. The polycarbonate resin may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, or may be a polyester carbonate resin copolymerized with an aromatic or aliphatic difunctional carboxylic acid, Moreover, the mixture which mixed 2 or more types of the obtained polycarbonate resin may be sufficient.

  The molecular weight of the polycarbonate resin is usually in the range of 10,000 to 40,000, preferably in the range of 13,000 to 30,000, more preferably in the range of 14,000 to 19,000, expressed as a viscosity average molecular weight. .

  Since a polycarbonate resin having a viscosity average molecular weight of about 15,000 is used for the optical disk substrate, if the polycarbonate film used as the light transmission layer is in the above range, the resulting film is unlikely to become brittle, and the end face is punched into a disk shape. It is less likely to generate a notch. Moreover, it is preferable at the point which a foreign material does not generate | occur | produce easily at the time of melt-extrusion, and it becomes difficult to generate a thickness spot. Furthermore, since the polymer of the resulting film tends to relax, the retardation value tends to decrease during the subsequent heat treatment, and after unwinding the roll after being rolled up, it is punched into a disk shape, for example. Even in the case of transporting the sheet, it is preferable because the flatness is good and troubles are less likely to occur when being bonded to the recording layer.

  The range of the viscosity average molecular weight of the most preferable polycarbonate resin is 14,500 to 17,500. In addition, it is preferable to use a polycarbonate resin that does not contain foreign matter having a high molecular weight as much as possible and heat degradation products.

The viscosity average molecular weight referred to in the present invention is obtained by inserting the specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C. into the following equation.
η _sp /c=[η]+0.45×[η] ² c
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
(Where c = 0.7, [η] is the intrinsic viscosity)

  In addition, it is optimal to use a film made of a polycarbonate resin having the same characteristics (that is, the same raw material and having an approximate viscosity average molecular weight) as that of the optical disk substrate for the light transmission layer. As a quality requirement of the light transmitting layer film, it is preferable to match the physical characteristics of the optical disk substrate having the optical recording layer and the physical characteristics of the light transmitting layer as much as possible. Physical properties include thermal expansion coefficient, hygroscopic expansion coefficient, thermal shrinkage ratio, viscoelastic behavior, and the like. If the optical disk substrate and the light transmission layer have different expansion and thermal expansion / contraction characteristics due to heat or moisture absorption, or if the viscoelastic behavior of the two is different, the optical disk substrate having the optical recording layer and the light transmission layer are bonded together. The optical disk may be deformed and distorted unequally due to a durability promotion test or a long-term change over time, and a skew phenomenon may occur.

  The light transmitting layer film of the optical disk of the present invention has a thickness in the range of 10 to 150 μm, preferably in the range of 10 to 100 μm. This thickness is important in order to input and output optical disc signals in an optimum state.

  The optical transmission layer film of the present invention has a thickness variation of ± 2 μm or less, preferably ± 1.5 μm or less. When the thickness unevenness increases, optical distortion becomes remarkable, and signal input / output fluctuation (noise) increases.

  The optical transmission layer film of the optical disk of the present invention has a thermal dimensional change rate of 0.08% or less, preferably 0.07% or less after heat treatment at 140 ° C. for 1 hour. When the thermal dimensional change rate is increased, micro peeling easily occurs at the interface between the optical recording layer and the light transmission layer.

  The light transmission layer film of the optical disk of the present invention has a total light transmittance of 89% or more, preferably 90% or more. In order to prevent the deterioration of the optical signal through the light transmission layer, the higher the total light transmittance, the better. If it is less than 89%, the optical signal may not be allowed to deteriorate as the optical disk.

  The film for the light transmission layer of the optical disk of the present invention has an in-plane retardation in the range of 1 to 15 nm, preferably in the range of 1 to 10 nm, more preferably in the range of 1 to 7 nm, and particularly preferably 1. The range is ˜5 nm. When the in-plane retardation becomes high, the modulation of the read light into the reproduction signal becomes large and the reproduction signal level becomes unstable.

  Further, in order to reduce the modulation of the read light to the reproduction signal and stabilize the reproduction signal level, the in-plane retardation variation in the film plane is preferably 1 to 8 nm, more preferably 1 to 6 nm. .

  The light transmitting layer film of the optical disk of the present invention has a retardation in the thickness direction of 100 nm or less, preferably 80 nm or less. The retardation in the thickness direction means the maximum K value (a value of 0 nm or more) obtained by a measurement method described later. As the maximum K value increases, noise increases.

  The film for the light transmission layer of the optical disk of the present invention has a center line average surface roughness in the range of 1 to 5 nm on both sides, preferably in the range of 1 to 3 nm. If the center line average surface roughness is too large, the surface irregularities will scatter light, resulting in increased noise.

  The light transmitting layer film of the optical disk of the present invention preferably has few surface defects and internal foreign matter in order to prevent noise. That is, the surface defect having a maximum length of 10 μm or more and a height of 3 μm or more is 10 pieces / square meter or less, preferably 5 pieces / square meter or less, and the bulky foreign matter having a maximum length of 20 μm or more is 5 pieces / square meter or less, The number of dent-like surface defects having a maximum length of 200 μm or more is preferably 1 piece / square meter or less, preferably 0 piece / square meter. The height of the surface defect may be a problem when the film is surface-coated such as by hard coating, and the defect with a height exceeding 3 μm is problematic because the top cannot be filled with the coating agent. Such protrusions on the film surface are transferred to the film surface to become protrusions due to scratches (mostly indentations) on the cooling roll or the film transport roll. The dent is a relatively gentle dent and is often shallow. When a strong dent on the film surface is observed with a scanning electron microscope, it can be cracked at almost the center of the defect, or a minute foreign matter may adhere to it. In general, small dents of less than 200 μm are applied during subsequent surface processing, or the strain is relaxed and disappears by heating.

  The light transmitting layer film of the optical disk of the present invention includes a stabilizer, an ultraviolet absorber, a toning agent, an antistatic agent and the like, as long as the characteristics of the film formed by melt film formation, such as transparency of the film, are not impaired. You can leave. In order to facilitate the electrostatic adhesion method suitably used in the production method of the present invention, a substance dissolved in a polycarbonate such as a small amount of sodium acetate or potassium acetate is used as a metal ion such as Na ion or K ion. An amount capable of enhancing the electroadhesion effect can also be added.

<Method for producing film for light transmitting layer>
Next, a method for producing a light transmitting layer film having the above characteristics will be specifically described.

(Melt extrusion conditions)
It is preferable to devise measures that do not cause thermal degradation of the polycarbonate resin during melt extrusion. For example, before melt extrusion, the raw material is sufficiently dried at about 120 ° C. and charged into a hopper of an extruder, and this hopper is heated from the outside and kept at about 110 ° C. Thus, deterioration of the resin due to chemical reaction such as hydrolysis is prevented. In order to prevent the air (oxygen) in the hopper from promoting the thermal deterioration of the resin, a method of replacing the atmosphere with hot nitrogen gas or circulating hot nitrogen gas is adopted.

  The present inventors are apt to generate heat degradation products in any part of the extrusion process, and what kind of thermal degradation of the polycarbonate resin (specifically, bisphenol A-PC) occurs between the processes from the screw extruder to the die extrusion. The screw was taken out of the extruder to see what happened in place. As a result, the part of the supply port that first bites the resin, the resin becomes sticky between the screw biting start part and the barrel at this part and becomes entangled with the screw, and the subsequent resin supply is obstructed. Causes discharge fluctuations. It has been found that when such a resin stays for a long time, it gradually deteriorates to produce a brown or black thermally deteriorated product. This entanglement of the resin can be prevented by water cooling the barrel portion of the screw biting portion (feeding portion).

  Also, the flange part that connects the tip of the extruder and the filter housing, the molten resin conduit, the molten resin conduit that connects the filter housing and the extrusion die, and the structure of the filter housing should not cause heat degradation as much as possible. It is important to design. For this purpose, first, measures such as not having a structure in which the resin is suddenly bent so as not to cause local stagnation of resin in the conduit of the molten resin can be cited.

  The filter housing is generally cylindrical, and has a structure in which a large number of filter elements having a necessary filtration area are combined and housed in the housing. In general, the cylindrical filter housing is set horizontally. However, this filter is preferably a vertical type. In the horizontal type (or horizontal type), when the molten resin is first injected into the filter housing, air cannot be completely pushed out, and air can be trapped in the housing in many cases. And this air pocket is compressed and becomes small by the high pressure at the time of extruding resin. Such a high-temperature air reservoir and the polycarbonate resin come into contact with each other and heat deterioration due to oxygen gradually proceeds. Further, when the residence time becomes longer, the thermally deteriorated material stays, and the minute deteriorated material sometimes passes through the filter element and is released into the extruded resin to become an internal foreign matter of the film. As one of the countermeasures, it can be prevented by making the filter housing into which molten resin is injected vertical. In this case, it is difficult for the air to stay in the air, so that heat degradation products in the filter are hardly generated. When the melt extrusion is started up, the resin is generally extruded from the screw tip, and the initial heat degradation product is discharged to the tip of the extruder to completely flow out, and then the polymer conduit portion of the filter housing incorporating the filter element is extruded. It is preferable to connect to the machine tip.

  According to the result of a simulated test of resin injection by pouring a highly viscous candy into a transparent plastic filter housing, it was confirmed that air stays in the housing. It was estimated that this stagnation phenomenon occurred even when the resin was actually flowed into the filter at a high temperature. In addition, air retention in the housing (in addition to the air retention, it is thought that gaseous substances produced by the reaction of high-temperature air (oxygen) and resin) are mixed during the operation of the extruder. For example, when the discharge amount of extrusion is reduced, the air in the air pool expands, and a part of the air may be discharged in the form of bubbles. In such a case, the surface defect of the film is caused by the heat-degraded product of polycarbonate and the gas generated by the deterioration.

  According to Non-Patent Document 3 (Polycarbonate Resin Handbook) described above, it is necessary to avoid retaining the polycarbonate at a high temperature for a long time. In addition, according to the result of examining the amount of carbon dioxide gas generated in the air and the holding temperature of the polycarbonate resin (treatment time 30 minutes), the result is that the temperature is less at 260 to 280 ° C., but rapidly increases at a temperature of 300 ° C. or higher. It has been shown that a very small amount of carbon dioxide gas is generated even at 340 to 360 ° C. in a nitrogen atmosphere.

  Thus, the thermal deterioration when the residence time of polycarbonate resin at high temperature is long cannot be ignored. The capacity of the melt extruder is such that the residence time from the resin extruder to the extrusion die tip outlet is shortened as much as possible so that the film thickness, width, and production speed (that is, the amount of molten resin discharged) are appropriate for its production. It is necessary to decide on. When taking measures such as enhancement of production capacity, it is necessary to make the residence time short as much as possible so that the resin can be sufficiently dissolved and the heat-deteriorated foreign matter is not generated. These factors determine the discharge capacity of the extruder. When forming a bisphenol A-PC resin (viscosity average molecular weight of about 14,000 to 19,000) suitably used in the present invention, the resin extrusion temperature is set to 270 to 320 ° C., and the residence time is within 30 minutes. Preferably it is within 20 minutes, more preferably within 10 minutes. In particular, the residence time is preferably 5 to 10 minutes. When the residence time is too short, particularly when the resin used for melt extrusion is crystallized, unmelted material may remain and appear as a foreign matter defect in the film. Such a thing often passes the resin filter element as a gel-like foreign material. By setting the melting temperature and the residence time within the above ranges, the thermal decomposition of the polycarbonate resin is suppressed, and as a result, heat-deteriorated foreign matter is hardly generated.

It is preferable to select a melt extruder having a discharge rate of about 130 kg / hr. For example, when an extrusion die having a width of 1200 mm, a film width of 1100 mm with uniform width characteristics and a film thickness of 50 μm is to be manufactured, the film take-up speed is about 30 m / min in calculation. . And the discharge amount at this time is about 130 kg / hr. As the screw, either a normal screw for melt-extruding polycarbonate or a known two-groove screw that separates solid and liquid in a resin melting step can be used. It is preferable to continuously measure and control the resin temperature at the screw tip.
Further, by passing a gear pump capable of precisely controlling the flow rate of the molten resin, it is possible to suppress a variation in the thickness of the film, particularly in the length direction (running direction).

  In the present invention, a conventionally known filter element for filtration can be used. It is preferable to use a heat-resistant and pressure-resistant filter element such as a commercially available metal sintered metal mold or an aggregate type of ultrafine metal fibers. In the case of using a filter element, it is also necessary to select a material that does not promote thermal deterioration or the like even if the resin stays.

The resin used is preferably an optical disk grade polycarbonate resin (for example, AD-5503 manufactured by Teijin Chemicals Ltd.). Optical disc grades are synthesized with great attention to foreign matter, so there is very little foreign matter in the polymer itself, and there is almost no foreign matter produced when melt-extrusion of this resin is used to produce optical discs. It is said that there is no problem even if the filter to be trapped does not use a precise filter, which is suitable for the present invention.
In the polymer conduit connecting the filtration device and the die, the thickness unevenness can be further improved by making the temperature and viscosity of the resin uniform using a mixer immediately before the die.

(Die extrusion conditions)
When extruding molten polycarbonate resin from the die, the resin film extruded from the die lip is affected by shrinkage in the air gap (between the die tip and the cooling roll) and turbulence in the atmosphere, resulting in thick spots. And die lines are likely to occur. In particular, when the melt viscosity is low (viscosity average molecular weight 14,000 to 19,000), it is remarkable. It is difficult to form a uniform film by a melt film-forming method in which a conventional air gap (distance between the die tip and the cooling roll) is wide.

The inventors of the present invention have a wave-like shape that appears prominently in the polycarbonate resin film obtained by the melt film-forming method by sufficiently narrowing the gap between the die lip tip of the melt extrusion and the cooling roll to eliminate the fluctuation in the space of the molten resin. It has been found that a polycarbonate resin film satisfying desired physical properties and optical characteristics can be obtained without causing uneven thickness and fine streaks (die streaks).
That is, the distance between the die lip tip of the extrusion die and the cooling roll surface is preferably in the range of 10 to 30 mm, and more preferably in the range of 15 to 30 mm.

  Also, the die structure causes abnormal flow of ambient air especially at the protruding part and causes film thickness unevenness, so measures to eliminate or reduce the uneven structure of the die as much as possible should be taken. Is preferred.

  The polycarbonate melt extrusion die is a T-die (coating hanger type die) that supplies resin from the central portion in the width direction of the die or a die having a shape that bisects the T-die at the inflow portion of the resin. A conventionally well-known thing, such as an I-die of the type which flows in resin from the one end part of the width direction, can be used. At this time, it is preferable that the lip from which the resin is discharged by the extrusion die is sufficiently sharpened. In addition, the lip is not a protruding type that is generally used, and when there are a screw, a screw hole, or the like that fixes the lower surface of the lip and the lip to the die body, it is preferable that the lip be flattened as much as possible. . In order to flatten, a method of fitting a member having a mirror surface on the lower surface of the die lip is preferably employed. By carrying out like this, the resin temperature and fluidity | liquidity of the polycarbonate resin melt-discharged can be made uniform in the width direction.

  The opening degree of the die (lip opening degree) is preferably about 1 mm to 2 mm when a film having a thickness of 100 μm is extruded and formed, for example. Furthermore, it is preferable that the die opening is set so as to gradually increase as the distance from the resin inflow portion increases in the die width direction. In this way, the pressure applied to the die lip in the width direction of the die is almost uniform, so that the molten resin flows easily. In practice, the lip opening is adjusted before use. After the start of melt extrusion, it is preferable to adjust the bolts on the lip part of the die automatically or manually while watching the film thickness (spots), particularly in terms of reducing the thickness spot. For automatic adjustment of thickness spots, the die lip bolt is mechanically rotated to adjust the lip gap, or a heating device is attached to the die lip at regular intervals, and the temperature of the melt is adjusted individually. A method (temperature lip) for adjusting the film thickness by utilizing the change can be adopted. From the viewpoint of easy adjustment of thickness spots, it is preferable to use a temperature lip rather than a mechanical lip opening adjustment method. In particular, when manufacturing a wide film, it is preferable to use a temperature lip having no mechanically moving part.

(About cooling roll)
The molten resin film extruded from the die is extruded onto the surface of a cooling roll that rotates uniformly (does not cause uneven thickness, does not cause streak, does not make retardation large and non-uniform, etc.). The cooling roll (cooling device) used at this time is a known method such as a method in which several small diameter rolls having a diameter of about 300 mm are combined (FIG. 1), or a method of cooling with a large diameter roll having a diameter of about 800 mm (FIG. 2). The method can be applied.

  In order to make the surface temperature of the cooling roll uniform, water whose temperature is controlled as a cooling medium can be poured into the inside of the roll for cooling. It is preferable that the flow path for flowing the cooling medium for cooling uniformly is counterflow. The water temperature is preferably 20 ° C to 70 ° C. The surface of the cooling roll is preferably subjected to hard chrome plating or the like and further superfinished (superfinished), and the surface is a mirror surface. The surface roughness Ra of such a surface is about 1 to 5 nm. Since the molten polycarbonate resin is discharged onto the ultra-mirror surface and is closely adhered and cooled, the surface roughness of the film surface transfers the surface roughness of the cooling roll. The surface of the cooling roll not only maintains the surface roughness in this way, but also keeps the surface from scratches and deposits. The surface of the take-up roll for taking the cooled film in the next step is also a flat surface without scratches or deposits. The surface roughness Ra of the light transmitting layer film of the present invention is in the range of 1 to 5 nm on both sides.

  The roll diameter is preferably about 800 mm, and the roll surface length is preferably about 1500 mm. When the diameter of the roll is about 800 mm, for example, a film having a thickness of 100 μm can be cooled at a speed of several tens of meters per minute.

(Adhesion cooling method of molten film to cooling roll)
The molten resin extruded from the die is solidified on a cooling roll to produce a film. At this time, as described above, the distance between the die lip tip of the extrusion die and the cooling roll surface is preferably in the range of 10 to 30 mm. The resin discharged from the die lip is allowed to flow down almost to the top of the cooling roll.

  In order to cool the film uniformly by bringing it into close contact with the cooling roll, in the present invention, a method in which the film is brought into close contact with the cooling roll by the electrostatic contact method over the entire width and the film is rapidly cooled and solidified is preferably employed. For electrostatic adhesion, a conventionally known SUS metal wire can be used for the positive electrode. What is necessary is just to stretch | stretch this metal wire to the space about 4-7 mm away on the film surface with moderate tension | tensile_strength. The installation position and voltage of the metal wire can be easily determined by trial and error. This condition of electrostatic adhesion affects the occurrence of film thickness spots and surface defects. The voltage of the electrostatic field is several kilovolts to 10 kilovolts, and when close contact is achieved, a current of several milliamperes flows. When the voltage is too low, a place where electrostatic adhesion occurs and a place where it does not occur appear as spots, resulting in extremely poor thickness unevenness of the film. In addition, when the voltage is too high, the film that is cooled and solidified from the molten state may cause dielectric breakdown, and the production of the film must be interrupted. A DC power source is used as the power source, the electrostatic wire is connected to the positive electrode, and the cooling roll side is connected to the ground. In the present invention, in order to broaden the adjustment range of electrostatic adhesion of the film and stabilize the effect, a metal ion such as Na ion may be added to the polycarbonate so as not to deteriorate the optical characteristics of the film.

  Further, the lower surface of the die lip is preferably flattened without any unevenness. By flattening the lower surface of the die lip, the electrostatic force works uniformly as a film adhesion force.

  In order to uniformly cool the film by bringing it into close contact with the cooling roll, a method of applying a liquid to the surface of the cooling roll and then bringing the molten film into close contact with the extruding roll on the liquid thin film and cooling it off is preferably employed. The arrangement of the die and the cooling roll is performed in the same manner as in the electrostatic contact method. For example, a thin film of water having a thickness of about several μm to several tens of μm is applied to the surface of the cooling roll by a roll coater, A molecular film is adhered and cooled and solidified. Note that if the water film is too thick, the cooled and solidified polymer film slides on the roll surface, so that the film cannot be taken out. If the water film is too thin, the film surface sticks to the cooling roll and it is difficult to remove. The film thickness of water can be determined by trial and error methods.

  In the present invention, the whole surface electrostatic adhesion method to the cooling roll and the whole surface water coating method may be used in combination. In the case of these combined use, the voltage between the cooling roll surface used for electrostatic adhesion and the electrostatic wire can be lowered, so that the film is liable to cause dielectric breakdown, such as when the film is thin. Then, the range of uniform adhesion can be further expanded.

  The melt-extruded film thus obtained does not have large wavy thickness spots in the width direction, and has no streaky surface defects. In particular, when water is applied to a cooling roll to form a film, a film free from defects such as die streaks can be produced. This is probably because the polycarbonate adhering to the tip of the die lip is hydrolyzed and removed due to the presence of water in this tight atmosphere.

(Method for taking film and reducing birefringence)
The melt-extruded film cooled by the cooling roll is usually taken up via the take-up roll. The obtained film has a so-called pan-bottom type retardation distribution in which the birefringence near the both ends is large even if the in-plane retardation (birefringence) at the center in the width direction is relatively small. Many. This is presumably because the birefringence due to the flow orientation of the polymer differs in the width direction of the extrusion. Even if the distance between the die tip and the cooling roll is narrowed as in the present invention, the narrowing of the polycarbonate resin film extruded from the die between the air gaps cannot be completely eliminated, and so-called polycarbonate flow orientation Since birefringence occurs, it is difficult to make this retardation small and uniform in the film width direction. Therefore, it is preferable to heat-treat the film in the next step. By performing such heat treatment, a film having a film width of 1,000 to 1,500 mm and a retardation of less than 10 nm in all the width directions can be obtained.

  For the heat treatment of the film, a method of passing the film through a heat treatment apparatus in which hot air at a desired temperature is adjusted is preferably adopted. By performing this step, the birefringence (retardation value) of the melt-extruded film can be easily reduced to the desired value of the polycarbonate film for the light transmission layer and can be made uniform in the plane of the film.

  The heat treatment temperature is preferably in the range of (Tg-10) ° C. to Tg ° C., where Tg is the glass transition temperature of the melt-extruded polycarbonate resin, (Tg-10) ° C. to (Tg-2) ° C. It is more preferable to set the range. In addition, the lower the tension (conveying tension) applied to the film, the better. When the retardation before the heat treatment is low, conditions for a higher heat treatment temperature and a lower conveying tension are selected. More specifically, the tension per cross-sectional area of the film during heat treatment is 0.5 to 3 Kg / square centimeter, preferably 0.5 to 2.8 Kg / square centimeter, more preferably 0.5 to 2.5 Kg / square centimeter, and even more preferably. Is 0.5 to 1.8 kg / square centimeter. The lower the tension, the better. However, since the film is transported, it cannot be made zero, and more preferably 1 Kg / square centimeter or more. In addition, according to our experiments, it is sufficient that the heat treatment time can be heated until the temperature of the entire cross section of the film to be processed is substantially the same as the temperature of the hot air to be heated. According to an estimate when a polycarbonate film having a thickness of 100 μm is heated with hot air, the heating time at which the hot air and the film introduced into the hot air become approximately the same temperature is about 30 seconds. Therefore, it is necessary to set the size of the hot air oven so that the film can stay for at least 30 seconds. The heat treatment time is sufficient within 1 hour.

  With respect to the tension applied to the film, the tension at the exit when the film is conveyed to the heat treatment oven can be measured with a tension detector. Equipment for heat-treating polymer films under high temperature and low tension includes (i) a so-called roll-suspended heat treatment device that transports the film on multiple rolls installed in an air oven, and (ii) air floating This is a heat treatment machine that blows high-speed air onto the film from above and below in the oven, and heats the film in a non-contact manner on the roll surface, etc. (iii) opens many small holes on the surface of the large drum There is an apparatus in which hot air is blown out from the child hole, a film is placed on the child hole, and the film is floated slightly from the drum surface and heat-treated. The method (ii) is surprisingly easy to apply tension to the film, and it is difficult to reduce the birefringence of the film. This seems to be because an excessive force is applied to draw the sine curve film out of the furnace.

  As described above, although some facilities have been conventionally used, it is most preferable that the heat treatment apparatus used in the present invention uses the above-described roll suspension type (i) (see FIG. 1). The tension applied to the film is the tension that pulls the film that has entered the heat treatment oven after the heat treatment, and this tension is the sum of the rotational resistance of all the rolls when the film is run on the roll (the roll applied to the film in the heat treatment zone). And the tension applied to the film in the cooling zone (cooling device) 11 immediately after that, and the tension required to run the film. The tension applied to the nip roll after cooling is measured and controlled, that is, the tension applied to the film can be controlled by measuring with a tension detector at the nip rolls 6 and 7 before entrance of the apparatus and the nip rolls 13 and 14 after exit of the apparatus. .

  In order to reduce the film tension of the heat treatment, the roll 10 used in the suspension type heat treatment machine needs to be able to rotate with a very weak force when the film is applied. The rotational force of one roll is 50 g or less, more preferably 30 g or less, and still more preferably 20 g or less. For this purpose, the support portion of the free rotating roll must be structured such that the rotation of the shaft of the roll does not become defective or burnt due to the thermal expansion of the shaft. In addition, the roll must be structured so that it can rotate with a weak rotational force. One countermeasure is to install the roll support outside the heat treatment machine, or to a temperature at which the hardness of the sliding part grease does not change even if the temperature changes significantly. Structural care is needed to keep it.

The heat treatment roll 10 is preferably made of a material such as light aluminum in order to make its rotational resistance as small as possible, and chrome plating or the like in order to maintain the surface hardness. It is preferable that the surface of the roll has a super-mirror surface, since defects such as scratches and transfer are hardly generated in the heat-treated film. In the present invention, it is desirable that the roll has a diameter of 95 mm or more and 150 mm or less, the outer shell is made of aluminum, the entire roll is lightened, and the roll is rotated with low resistance. Thus, it is preferable to set the resistance applied to the film in the suspension type heat treatment machine to 3 kg / cm ² . It should be noted that, by changing the diameter of the roll 10 within the above range, if a trouble occurs that causes scratches on the film surface, it is preferable because the roll that became the source can be easily identified (scratches are generated from the pitch of the scratches). Rolls can be identified relatively easily).

  The distance between horizontal surfaces of the heat treatment roll 10 is preferably 95 mm to 150 mm. The distance between the upper and lower rolls is 2 m or less, more preferably 1.7 m or less. If the horizontal plane distance between rolls is too small or the top and bottom roll distances are too large, the running film on the rolls will rub against each other or fuse together due to its low tension, causing the film to surface. It may cause defects or interrupt film formation. Moreover, if the diameter of the roll and the distance between the surfaces are too large, there is a disadvantage that the dryer must be unduly enlarged. Moreover, if the upper and lower roll intervals are too large, the effect of heat treatment that lowers the retardation due to the tension of the film on the rolls due to its own weight may be diminished.

  In a preferred roll-suspended heat treatment machine to be applied to the present invention, in order to heat-treat the entire film uniformly and make the birefringence small and uniform, hot air is caused to flow down from the ceiling of the oven through the punching plate, It is preferable to install a punching plate on the floor of the heat treatment apparatus, suck the heated air, readjust the temperature outside the heat treatment machine 8, and circulate. The wind speed at this time is several m / sec or less.

  It is preferable that the heat-treated film is subsequently passed through a similar roll-suspended film cooling zone 11. The hot air temperature for film cooling here is preferably 80 to 50 ° C., and then the film is taken out to room temperature. When the film is gradually cooled in this manner, the film does not change rapidly in length or width, and therefore, problems such as scratches caused by the film and scratches or poor running can be prevented.

(Film surface treatment)
The film of the present invention can be subjected to a known surface treatment such as application of an antistatic agent or a hard coat treatment.
The polycarbonate resin film according to the present invention is preferably used for a light transmission layer of an optical disk. The optical disc in which the optical recording layer of the present invention is laminated on the surface of the optical recording layer is preferably subjected to a treatment for preventing surface damage and preventing damage when handled. For this purpose, at least one surface of the light transmission layer film of the present invention may be subjected to surface hardening treatment (hard coat treatment) by a conventionally known method. Moreover, the process etc. which raise the surface energy of the film surface of this invention by a corona treatment and an anchor coat process, and raise adhesiveness etc. can be suitably implemented by a well-known method. In such a so-called post-processing treatment, a roll once wound up can be post-processed in a separate process, and again wound together with a protective film to form a roll-up roll, which can be sent to the next processing step.

(Winding of film and formation of film winding layer)
The film for a light transmission layer of the present invention can be used in the state of a wound layer wound up into a roll having a width of about 1 m, or can be slit for further use as a narrower winding roll.

  As a method of winding in a roll shape, (i) so-called unevenness is applied to both ends of a wide film by a narrow or mechanical method such as mechanical or thermal, and the inner film surface is separated from the inner film surface to prevent scratching and so-called winding. Winding with knurling, (ii) Co-winding (or wrapping) that protects the inner film surface from scratching by overlapping only a narrow film of other material and both ends, and (iii) Other polymer Adopting a method of wrapping the film and the film of the present invention over the entire surface, (iv) a method of wrapping the protective film having the weak adhesive layer on the surface and the light transmission layer film of the present invention for use, etc. Can do. As a method for protecting the surface of the light-transmitting layer film, a preferable method is selected depending on conditions for use. Before using the film of a film winding roll (rolled layer body) as a light transmission layer, when the surface treatment or the roll is slit narrowly, the light transmission layer of the present invention has weak adhesion on one side. It is preferable to use it with the surface protected by such a protective film.

  Patent Document 3 and Patent Document 4 describe winding bodies using a protective film. The light-transmitting layer film of the present invention is generally punched into a disk shape while being weakly attached to a protective film, and is then transported through a narrow transporting process of an optical disk manufacturing apparatus and attached to the optical recording layer of the optical disk. In this attaching process, it has been pointed out that the punched film disk may be curled and caught on the components of the transport device, causing trouble. It has been found that this problem can be avoided if the curl is 10 mm or less.

  In general, a protective film having a low Young's modulus and a relatively soft film as a base material and processed so that the surface has weak adhesion is often used. These protective films are overlaid on the film during the film production process of the present invention. First, the protective film is set on an unwinding machine and unwound. At this time, the protection film must be unwound as much as possible so as not to be deformed by being pulled by the unwinding tension. The protective film wound in this way is merged with the light transmitting layer film of the present invention, and the adhesive surface of the protective film is bonded to the surface of the light transmitting layer film with a weak nip, and then wound. take. In addition, the composite bonded with the protective film is also wound with a weak winding tension. The temperature and tension conditions at the time of winding influence the size of the curl after the winding roll is unwound and punched into a disk shape. Furthermore, as the winding core (winding core), use a large-diameter core, wind it with as low a tension as possible, and cause distortion of the so-called light-transmitting layer film due to the winding force during storage on the roll film after winding. We must make it as small as possible.

In order to reduce the curl, it is also possible to use a biaxially stretched heat-fixed polyester film that is not easily deformed as a protective film and has a relatively high Young's modulus.
Moreover, when the roll is stored, the film of the light transmission layer is slightly deformed by so-called winding, so when the film of the present invention is unwound and used, it is preliminarily heat treated and wound up. The optical distortion when stored as a body can also be removed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this. In addition, the measurement of this invention in an Example and evaluation of an effect were based on the following method.

(1) Measuring method of viscosity average molecular weight The viscosity average molecular weight M of polycarbonate resin calculated | required intrinsic viscosity [(eta)] from the viscosity measurement in 20 degreeC of the methylene chloride solution with a density | concentration of 0.7 g / dl, and computed it from the following formula.
η _SP /c=[η]+0.45×[η] ² c (where [η] is the intrinsic viscosity)
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
c = 0.7

(2) Measuring method of film thickness A sample of 1.0 m in total width (1.3 m) was taken in the winding direction of the polycarbonate film on which the protective film was not laminated. The film is divided into a 10 cm × 10 cm grid in the width direction (perpendicular to the winding direction) and the winding direction (if the fraction in the width direction exceeds 5 cm, that portion is also taken as the measurement sample), At the center, the thickness was measured using a micrometer manufactured by Mitutoyo Corporation. And the average value of the thickness of 130 measurement points was calculated | required, and this was displayed as the thickness of a film.

(3) Measurement method of film thickness unevenness In the measurement method using the micrometer of (2) above, there is a possibility of missing a thickness unevenness other than the measurement point, for example, a wide strip or thin streaky thickness unevenness. Therefore, the thickness spot was continuously measured using an Anritsu Co., Ltd. film sickness tester KG601. The measurement film was sampled as follows. That is, 20 samples of the full width were continuously cut out at intervals of 5 cm in the film winding direction (total of 100 cm in the film winding direction). Each of these thickness distributions was measured with the above-mentioned film thickness tester and recorded on a recording paper. Thus, the difference (thickness range) between the maximum value and the minimum value of the recorded thickness was determined for the 20 films (5 cm × 130 cm), and the average thickness of the film was determined from the maximum thickness range. It was displayed as a thick spot from.

(4) Rate of thermal dimensional change A parent sample of an appropriate size was collected from three places in the width direction of the polycarbonate film (film width is approximately 1.3 m). Further, a total of 30 samples were prepared from each of the parent samples, 10 samples for measuring the rate of thermal dimensional change. The size of the sample for measuring the rate of thermal dimensional change is set to 150 mm for the film winding direction for 10 out of the 10 parent samples, 10 mm for the direction perpendicular thereto, and the film winding for the remaining 5 samples. The taking direction was 10 mm, and the perpendicular direction was 150 mm. And about each sample, the mark for a heat | fever dimensional change rate measurement was marked at an interval of 100 mm in the 150 mm length direction. Thus, 15 measurement samples were prepared in the film winding direction at 15 points and in the direction perpendicular to the film (width direction).

The sample for measurement was suspended in a 140 ° C. constant temperature bath under no load and treated for 1 hour, then taken out to room temperature and cooled, and the gauge interval was measured. The measurement of the dimensions was carried out using a reading microscope under conditions of constant temperature and humidity at 23 ° C. and 55% RH. The dimensional change rate was obtained from 15 points in the winding direction and 15 points in the width direction as follows from the dimensions before and after the 140 ° C. heat treatment. The maximum value was displayed as the thermal dimensional change rate.
Thermal dimensional change rate = [{(dimension before treatment) − (dimension after treatment)} / (dimension before treatment)] × 100 (%)

(5) Total light transmittance About 300 mm square samples were collected from three places in the width direction of the polycarbonate film (film width was about 1.3 m). The total light transmittance of the sample was measured using a color difference / turbidity measuring device COH-300A manufactured by Nippon Denshoku Industries Co., Ltd. Five points were measured for each sample, and an average value of a total of 15 points for three samples in the width direction was defined as the total light transmittance.

(6) Measurement of in-plane retardation value (Re.) A strip-shaped sample having a length of 40 mm in the winding direction in the width direction of the polycarbonate film was collected at three locations in the winding direction at intervals of 50 cm. Next, this strip-shaped film was cut at intervals of 40 mm to prepare a 40 mm square sample for measurement. That is, since there are 33 strip samples from 1300 mm in length in the full width direction of the film, a total of 99 measurement samples were obtained. The in-plane retardation value (Re.) Of these samples was measured. The numerical display is Re. The value range was displayed as the minimum value to the maximum value.
The measuring instrument used was a product name KOBRA-21ADH, which is a birefringence measuring instrument manufactured by Oji Scientific Instruments Co., Ltd. The value was measured.

(7) Measurement of retardation value K in the thickness direction Sampling was performed in the same manner as the measurement in the above item (6), and measurement was performed with KOBRA-21ADH. The polycarbonate film sample was rotated about its slow axis or fast axis, the retardation was measured by changing the incident angle, and the refractive indexes nx, ny and nz were calculated from these data. Furthermore, K value = ((nx + ny) / 2−nz) × d was calculated from these values.
Here, nx represents the refractive index in the winding direction, ny represents the refractive index in the direction orthogonal to the winding direction, nz represents the refractive index in the thickness direction, and d represents the thickness of the measurement film (unit: μm). . The unit of K value is calculated in μm at the time of the above calculation, but is converted to nm unit when this is displayed. In the present specification, the maximum K value means the maximum value among them.

(8) Measurement of centerline average surface roughness (Ra) The centerline average surface roughness (Ra) is a value defined by JIS-B0601, and the numerical values in this specification are those of Kosaka Laboratory. It measured using the contact-type surface roughness meter (Surfcoder, SE-30C).
The measurement conditions for Ra were as follows.
Stylus tip radius: 2μm
Measurement pressure: 30mg
Cut-off: 0.08mm
Measurement length: 1.0mm

  In the same manner as the parent sample of (4) above, three points in the width direction of the film were sampled and used for measurement. Repeat measurement for the same sample 5 times, and remove the largest value for the measured value (value up to the 4th decimal place in μm unit), and obtain the remaining 4 data. The fourth decimal place of the average value of 12 values is rounded off, and the third decimal place is shown in nm.

(9) Measurement of foreign matter and surface defects The polycarbonate film immediately before co-winding with the masking film was sampled about 1 square meter (film 1.3 m width × extrusion direction length about 1 m) and subjected to measurement.

(I) Bulk foreign matter such as heat-degraded material The sampled film was dissolved in methylene chloride to form a low-concentration (1% by weight) polycarbonate solution, and this foreign matter was filtered off with a 10 μm filter. This was observed with a microscope, and those having a maximum length of 20 μm or more were counted. Moreover, the feature (cause) of the foreign matter was confirmed by qualitative analysis using FT-IR and EPMA.

(Ii) Projection on film surface A major defect was found by irradiating the film surface with light from obliquely above and visually observing the reflected light. The height of the defective portion was measured using a laser microscope manufactured by Keyence Corporation. In addition, small defects that could not be found by visual observation were sampled on a 5 cm square of the film and found by observation with a transmission microscope. A mark was placed around the film and observation was performed with a laser microscope to measure the height and spread of the defect. Those having a maximum length of 10 μm or more and a height of 3 μm or more were counted.

(Iii) Indentation The appearance frequency of indentations was counted with a 1 square meter film. The dents were counted when the maximum length was 200 μm or more by oblique illumination. When the film surface is viewed from the front, a small dent is hardly found by visual observation, but can be easily found by oblique illumination visual observation. In this method, light is irradiated from an oblique direction on a film spread on a black flat plate, and the reflected light is visually observed to find a non-uniform portion of minute light reflection.

(10) Measurement of curl Seven 150 mm square samples were cut out uniformly in the film width direction. In the case of a film in which the protective film is adhered with a weak force, it was cut into a 150 mm square as it was. The sample with the protective film was placed on a flat plate subjected to an antistatic treatment with the protective surface facing down and the polycarbonate film surface facing up. At this time, care was taken not to cause abnormal measurement due to static electricity generated on the film. In this state, the film was placed for 5 minutes, and the amount of lift at each of the four corners of each film sample was measured with a scale. The maximum value in the four corners was taken as the curl value.

[Example 1]
Optical grade polycarbonate pellets (trade name AD-5503, Tg; 147 ° C., viscosity average molecular weight M; 15,000), a homopolymer of bisphenol A manufactured by Teijin Chemicals Ltd. And dried at 120 ° C. for 3 hours. This was put into a heating hopper of a melt extruder heated to 110 ° C. and melt extruded at 290 ° C. As a filter for removing foreign matters from the molten polymer, a disk-shaped SUS nonwoven fabric having an average opening of 10 μm was used. The molten resin after filtration was extruded onto a rotating cooling roll surface (surface temperature set to 60 ° C.) with an I-die set to 290 ° C. The cooling roll used had a diameter of 800 mm and a roll surface length of 1800 mm. A structure having a structure in which a coolant flows so that the surface temperature of the roll is uniform was used. The extrusion die had a lip width of 1500 mm and a lip gap of about 2 mm. The die lip was flat with no irregularities on its lower surface.

  The resin flowing down from the extrusion die was wound around the top of the cooling roll (see FIG. 2). The distance between the die lip tip and the cooling roll surface was 25 mm. In order to uniformly cool the film and take it out, the entire width of the film was brought into close contact with the surface of the cooling roll using an electrostatic contact method. As an electrode for electrostatic adhesion, a SUS piano wire having a thickness of about 180 μmφ was used which was cleanly polished. A positive electrode of a DC power source was connected to this piano wire, and the cooling drum side was grounded. The applied voltage was 7 KV. Thus, a film having a thickness of 97 μm was taken up through the take-off roll at a cooling roll rotational speed of 10 m / min.

Subsequently, the film was heat-treated by passing through a roll-suspended heat treatment machine. 100 mmφ rolls were alternately arranged in a roll-suspended heat treatment machine. The distance between the upper and lower rolls was 1.6 m, and the distance from the next roll placed was 100 mmφ, the same as the roll diameter. And the film which should be processed was created so that the length which stays in the oven in this roll suspension type heat processing machine might be set to about 50 m (residence time 60 seconds). The hot air temperature in the oven in the heat treatment machine was 142 ° C., and the film tension at the oven outlet was 3.0 kg / (thickness 97 μm × total film width 1440 mm) (2.1 kg / square centimeter per cross-sectional load). The film after exiting the oven was similarly cooled to 60 ° C. or lower with a roll suspension type processor, and then taken out to room temperature.
Both ends of the heat-treated film are cut off by 70 mm each to form a 1300 mm wide film, a biaxially stretched polyethylene terephthalate with a thickness of 29 μm, and a heat-fixed film surface is wound together with a protective film having a weak adhesive process, and 500 m is wound together. A wound layer was completed.

The characteristics of the obtained film were as follows, and were excellent as a light transmission layer application.
Film thickness and thickness variation; average thickness is 97 μm, thickness variation range is ± 1.5 μm
The thickness spots were spots that changed gently in the width direction of the film. No streaky spots or streaky surface defects were detected on this film. (I projected a parallel light source on the film and projected it on the screen to look for fine streaks, but I couldn't find it.)
Birefringence, retardation: In-plane retardation distribution in the width direction had an average value of 4 nm, a maximum value of 5 nm, and a minimum value of 3 nm. The thickness direction retardation was 80 nm.
Internal foreign matter: One internal foreign matter with a maximum length of 20 μm or more / square meter Surface defect: Scratched surface with a maximum length of 10 μm or more, height of 3 μm or more, 2 surface defects / square meter, and a maximum length of 200 μm or more Zero defects / square meter Thermal dimensional change rate of film; 0.06%
Total light transmittance: 90%
Curl amount; the maximum curl amount is 10mm
Film surface roughness: 2 nm on both sides
Linear expansion coefficient of the film: 0.7 × 10 ⁻⁴ / ° C.
Moisture absorption rate of film: 0.2% (23 ° C. water, 24 hours)

[Example 2]
The polycarbonate resin, melt extrusion apparatus, and film cooling roll used in Example 1 were also applied in this case. In addition, instead of using the electrostatic contact method, in this example, a method of applying water to the cooling roll was applied as a method for attaching the film melt-extruded from the die to the cooling roll. The position where water was applied to the cooling roll was between the time when the film was taken up via the take-off roll and the time when the melt-extruded film from the extrusion die landed. As a method for supplying water to the cooling roll, a three-roll type coating device for transferring the water drawing roll, the metering roll, and the water film onto the cooling roll surface was used.

  The resin flowing down from the extrusion die was wound around the top of the cooling roll. The distance between the tip of the die lip and the cooling roll surface was 20 mm. Thus, the film having a thickness of 50 μm was cooled and taken up at 20 m / min. Thereafter, the film is subsequently fed into a roll-suspended heat treatment apparatus, the hot air temperature in the oven is set to 140 ° C. (residence time 60 seconds), and then the film is cooled to 60 ° C. in the roll-suspended heat treatment apparatus to room temperature. I took it out. At this time, the nip tension of the film at the outlet of the oven was 1.5 kg / (thickness 50 μm × width 1400 mm) (cross-sectional load was 2.1 kg / square centimeter). This film was overlaid with care as a protective film in the same manner as in Example 1 to produce a 500 m roll film.

The characteristics of the obtained film were as follows, satisfying the predetermined characteristics, and excellent as a light transmission layer application.
Film thickness and thickness variation; average thickness 50 μm, thickness variation range is ± 0.8 μm
No streaky spots or streaky surface defects were detected on this film. In addition, a parallel light source was projected onto the film, and it was projected onto the screen to look for fine streaks, but this defect was not found.
Birefringence, retardation: In-plane retardation distribution in the width direction had an average value of 4 nm, a maximum value of 5 nm, and a minimum value of 2 nm. The thickness direction retardation was 80 nm.
Internal foreign matter: One internal foreign matter with a maximum length of 20 μm or more per square meter,
Surface defects: 0 / square meter surface defect with a maximum length of 10 μm or more and a height of 3 μm or more, 0 scratch / square meter surface defect with a maximum length of 200 μm or more. %
Total light transmittance: 90%
Curl amount; the maximum curl amount is 8mm
Film surface roughness: 2 nm on both sides
Linear expansion coefficient of the film: 0.7 × 10 ⁻⁴ / ° C.

[Example 3]
A film was obtained under exactly the same production conditions as in Example 1 except that polycarbonate pellets having a viscosity average molecular weight of 18,000 (Tg; 149 ° C.) were used. The characteristics of the obtained film were as follows.
Film thickness and thickness variation; average thickness is 97 μm, thickness variation range is ± 1.5 μm
No streaky spots or streaky surface defects were detected on this film.
Birefringence, retardation: In-plane retardation distribution in the width direction had an average value of 5 nm, a maximum value of 7 nm, and a minimum value of 4 nm. The thickness direction retardation was 80 nm.
Internal foreign matter: 3 internal foreign matters with a maximum length of 20 μm or more / square meter Surface defect: surface with a maximum length of 10 μm or more, height of 3 μm or more with 1 surface defect / square meter, maximum length of 200 μm or more Zero defects / square meter Film dimensional change rate: 0.08%
Total light transmittance: 90%
Curl amount; the maximum curl amount is 10mm
Film surface roughness: 2 nm on both sides
Linear expansion coefficient of the film: 0.7 × 10 ⁻⁴ / ° C.

[Examples 4-6, Comparative Examples 1-2]
A light transmitting layer film was produced in the same manner as in Example 1. At that time, the heat treatment temperature of the film in the heat treatment step and the tension at that time were changed as shown in Table 1. The film characteristics at this time are shown in Table 2.

  Under the heat treatment conditions of Examples 4 to 6, if the heat treatment temperature was (Tg-10) to Tg and the tension of the heat treatment was selected, a uniform film having a small retardation could be obtained. In addition, Tg of the polycarbonate resin used here was 147 degreeC. Comparative Example 1 shows a case where the heat treatment temperature is lower than (Tg-10) ° C. and the tension is low. In this case, since the temperature is too low to cause relaxation of the molecular chain, the retardation could not be lowered to a desired value. Further, Comparative Example 2 shows a case where the heat treatment temperature is higher than Tg and heat treatment is performed at a relatively low tension. However, in this condition, the temperature is too higher than Tg, and the molecular chain is not affected even by a considerably weak tension. Was stretched during the heat treatment to increase the birefringence and retardation.

[Example 7]
Polycarbonate resin powder (viscosity average molecular weight M; 24,600, Tg; 153 ° C.) which is a homopolymer of bisphenol A manufactured by Teijin Chemicals Ltd. is dried in a packed tower dryer (drying temperature 125 ° C .; drying time) 6 hours). Next, this resin powder is melted, and foreign substances in the resin are removed using a filtering device (element average opening is 10 μm) made of ultrafine metal fibers, and then a 1800 mm wide T-die (set temperature 282 ° C.) 1 The resin was extruded at a discharge rate of 127 kg / hour. As shown in FIG. 1, the melt-extruded film was passed through a first cooling roll 2, a second cooling roll 3, a third cooling roll 4, and a transfer roll (also serving as a dancer roll) 5 and cooled.

  The distance from the resin discharge part of the T die to the contact of the molten film of the first cooling roll, the air gap is 135 mm, and electrostatic wires (applied voltage = applied voltage = about 50 mm each from the film end face) 10 KV; application effective length = 45 mm), and a film was obtained by a method in which both ends of the film were in close contact with the cooling drum.

  The diameters of the first, second, and third cooling rolls are all specular rolls having a diameter of 300 mm, and the transfer roll 5 is a specular roll having a diameter of 120 mm. The temperature of the 1st cooling roll 2 was 140 degreeC, the temperature of the 2nd cooling roll 3 was 152 degreeC, and the temperature of the 3rd cooling roll 4 was 150 degreeC. The transfer roll 5 was kept at a constant temperature by circulating a heat medium at 50 ° C. inside. A mirror roll having a surface speed of 10 m / min and a film thickness of 95 μm was prepared.

Next, in order to heat-treat this film, the film was immediately passed through a roll suspension type heat treatment apparatus 8. In this apparatus, the tension was detected by the nip roll 13 and the guide roll 14 so that the tension applied to the film was 2.5 kg / cm ² and was automatically adjusted. In addition, the hot air temperature in the heat treatment apparatus was adjusted to be 143 ° C. ± 0.5 ° C. Further, the film suspension roll 10 used in the treatment apparatus was made to be the same as the hot air temperature. The residence time of the film in this apparatus was 10 minutes, and then the film was sent to the film cooling chamber 11 whose temperature was adjusted to 65 ° C. and cooled, and then the film was taken out of the cooling chamber to the external room temperature and cooled during melt extrusion. Both ends of the film that is in close contact with the roll and has poor surface properties were cut out by 75 mm each, and then overlapped with the protect film 15, and both were wound into a roll 18. Thus, an optical film excellent in transparency and uniformity having no thickness defects of ± 1.5 μm, a center line average surface roughness of 2 nm, a film width of 1500 mm, and no surface defects. Obtained. The retardation value of this film was an average value: 5 nm, a maximum value: 7 nm, and a minimum value: 2 nm. The film forming conditions are shown in Table 3, and the film characteristics are shown in Table 4.

[Comparative Example 3]
The temperature of the heat treatment apparatuses 8 and 11 in Example 7 was set to room temperature, and the film was directly guided from the guide roll 9 to the guide roll 12 without passing through the suspension roll 10 to transport the nip roll 13 / guide roll 14 film. Next, the masking film 15 was overlaid on this film, and the film was nipped between rolls 16 and 17 and wound into a roll 18. Other conditions were the same as in Example 1. In this case, the retardation value of the obtained film had an average value of 20 nm, a maximum value of 32 nm, and a minimum value of 10 nm. In addition, the film has excellent thickness uniformity, no surface defects, no surface defects, and excellent transparency and uniformity. However, this film has high retardation at both ends in the width direction (so-called pan bottom type). The retardation distribution was poor, and the uniformity of the retardation was poor, and the retardation was uniform and the small characteristics could not be obtained. The film forming conditions are shown in Table 3, and the film characteristics are shown in Table 4.

[Example 8]
Polycarbonate resin powder (viscosity average molecular weight M; 28,000, Tg; 154 ° C.) which is a homopolymer of bisphenol A manufactured by Teijin Chemicals Ltd. is dried in a packed tower dryer (drying temperature 125 ° C .; drying time) 6 hours). Resin powder is melt-extruded using a single screw extruder with a screw diameter of 90 mm, and this molten resin is rotated by a coat hanger type T die (set temperature 280 ° C.) with a width of 1,800 mm and rotated at a discharge rate of 175 kg / hr. It flowed down to the top of the surface (see FIG. 2). As the cooling roll, a cooling roll having a diameter of 800 mm and a width of 2,000 mm, the temperature of which can be adjusted, was used.

  The distance from the resin discharge part of the T die to the contact of the molten film of the cooling roll 101, that is, the air gap is 135 mm, and the tension in the running direction is a tension adjusting roll (also called a dancer roll) provided immediately after the take-off roll 102. Through 103. Furthermore, the electrostatic film (applied voltage = 10 KV; applied effective length) is applied to both ends of the film (in the range of about 50 mm from the film end surface) in the process where the molten film extruded into a film contacts the cooling drum 101 and solidifies. The film was obtained by a method in which both ends of the film were brought into close contact with the cooling drum. The film forming speed was 15 m / min, and the film thickness was adjusted to 90 μm.

Next, the obtained polycarbonate film was passed through a roll suspension heat treatment apparatus 8. The hot air temperature for the heat treatment was 145 ° C., the tension was 1.5 kg / cm ² , and the heat treatment time was 5 minutes. Thereafter, the film cooling chamber 11 was passed through, taken out to room temperature and cooled. At the time of melt-extrusion, the end portion which is in close contact with the cooling roll 101 and has poor surface properties was removed, and a film having a total width of 1,500 mm was obtained. As for the retardation of the obtained film, the average value was 8 nm, the maximum value was 10 nm, and the minimum value was 7 nm. The film had no die-like spots, and the thickness spots were ± 1.5 μm. The center line average surface roughness Ra was 3 nm on both sides of the film. The film forming conditions are shown in Table 3, and the film characteristics are shown in Table 4.

[Examples 9 and 10]
A polycarbonate resin (viscosity average molecular weight M; 15,000, Tg; 147 ° C.), a homopolymer of bisphenol A manufactured by Teijin Chemicals Ltd., is dried in a packed tower dryer (drying temperature 125 ° C .; drying time 6). Time). The resin was melted, extruded from a T-die having a width of 1,800 mm (set temperature: 280 ° C.), and cooled using three mirror surface cooling rolls having a diameter of 300 mm (see FIG. 1). A method was used in which the air gap between the tip of the melt extrusion die and the first cooling roll was 50 mm, and both ends of the film on the first cooling roll surface were closely fixed by electrostatic wires. At this time, the surface temperature of the cooling roll was set to 75 ° C. Films with thicknesses of 50 μm and 25 μm were obtained by adjusting the positions of the first cooling roll and the second cooling roll. The film forming speed was 20 m / min.

  Next, the film was passed through a roll suspension type heat treatment apparatus 8 in order to heat-treat this film. In this apparatus, the hot air temperature for film processing, the tension applied to the film, and the heat treatment time are adjusted, and then the film is sent to a film cooling device 11 whose temperature is adjusted to 65 ° C. and cooled to room temperature. And rolled up into a roll 18 to obtain a film wound layer having a film width of 1,400 mm. The film forming conditions are shown in Table 3, and the film characteristics are shown in Table 4.

[Comparative Example 4]
A film wound layer having a film width of 1,400 mm was obtained in the same manner as in Example 10 except that the heat treatment was not performed using a roll-suspended heat treatment apparatus. The film forming conditions are shown in Table 3, and the film characteristics are shown in Table 4.

The schematic of the film forming apparatus used in the present invention (Examples 7, 8 and 10) is shown. The schematic of the film forming apparatus (Examples 1-6 and 9) used by this invention is shown.

Explanation of symbols

1: Molten resin extrusion die 2: First cooling roll (mirror surface roll)
3: Second cooling roll (mirror roll)
4: Third cooling roll (mirror roll)
5: Transport roll (dancer roll)
6: Nip roll 7: Guide roll 8: Heat treatment apparatus 9: Guide roll 10: Suspension roll 11: Cooling apparatus 12: Guide roll 13: Nip roll 14: Guide roll 15: Masking film 16: Guide roll 17: Nip roll 18: Winding roll 100 : Melt extrusion die 101: Cooling roll 102: Take-up roll 103: Conveyance roll (dancer roll)
104: Nip roll 105: Guide roll

Claims (6)

A film obtained by obtaining a polycarbonate resin film by any of the following methods (A) to (B) , and heat-treating the obtained polycarbonate resin film under the following conditions (1) to (3): Thickness is 10 to 150 μm, thickness variation is ± 2 μm or less, thermal dimensional change after heat treatment at 140 ° C. for 1 hour is 0.08% or less, total light transmittance is 89% or more, in-plane retardation is 1 to 15 nm, A method for producing a polycarbonate resin film having a thickness direction retardation of 100 nm or less and a centerline average surface roughness of 1 to 5 nm on both sides.
(A) A method in which a polycarbonate resin is melt-extruded from a die into a film, an air gap between the die and a cooling roll is 10 to 30 mm, and the entire surface of the film is closely adhered to the roll by an electrostatic adhesion method. More melt-extruded into a film, the air gap between the die and the cooling roll is 10 to 30 mm, a liquid thin film is applied to the surface of the cooling roll, and the molten film is extruded onto the thin film to adhere to the roll and cool ( 1) Heat treatment temperature; (Tg-10) to Tg (where Tg is the glass transition temperature of the polycarbonate resin)
(2) Heat treatment tension: 0.5 to 3 Kg / square centimeter as film cross-sectional load (3) Heat treatment time: 30 seconds or more A polycarbonate resin film is obtained by the following method (C) , and the obtained polycarbonate resin film is heat-treated under the following conditions (1) to (3). The thickness of the film is 10 to 150 μm, Thickness variation is ± 2 μm or less, thermal dimensional change rate after heat treatment at 140 ° C. for 1 hour is 0.08% or less, total light transmittance is 89% or more, in-plane retardation is 1 to 15 nm, thickness direction retardation is 100 nm Hereinafter, the manufacturing method of the film made from polycarbonate resin whose centerline average surface roughness is the range of 1-5 nm on both surfaces.
(C) A method in which a polycarbonate resin is melt-extruded from a die into a film shape, the air gap between the die and the cooling roll is 40 to 150 mm, the molten film is extruded, and both ends of the film are in close contact with the cooling roll and cooled (1) Heat treatment Temperature; (Tg-10) to Tg (where Tg is the glass transition temperature of the polycarbonate resin)
(2) Heat treatment tension: 0.5 to 3 Kg / square centimeter as film cross-sectional load (3) Heat treatment time: 30 seconds or more The method for producing a polycarbonate resin film according to claim 1 or 2 , wherein the polycarbonate resin is a polycarbonate resin obtained from a dihydroxy component having at least 50 mol% of bisphenol A. The method for producing a polycarbonate resin film according to claim 1 or 2 , wherein the polycarbonate resin has a viscosity average molecular weight in the range of 14,000 to 30,000. Claim 1 or obtain a polycarbonate resin film by the method according to 2, the obtained polycarbonate resin film was laminated, the film production method of winding layers thereof, characterized in that winding up. The method for producing a polycarbonate resin film according to claim 1 or 2 , wherein the heat treatment step is a heat treatment step using a roll suspension heat treatment machine.

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