JP2007050631A - Substrate film for manufacturing plastic film by cast method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent substrate film for a manufacturing process, which enables a transparent film, particularly, for optical use etc. to be efficiently manufactured with high productivity, and which enables a clear image to be obtained for display by preventing the adhesion of foreign matter to the obtained cast film and the appearance of streaks on the obtained cast film, so as to prevent a defect in optical use. <P>SOLUTION: This substrate film for manufacturing a plastic film by the cast method is used as a substrate in the process of manufacturing the plastic film by the solution cast method. The substrate film is characterized as follows: a layer constituting a cast surface of the film contains a polyester constituent except a main polyester constituent in the range of 2-25 mol%; the center line average roughness Ra of the film surface is in the range of 3.0-20.0 nm; and the maximum height Rt thereof is in the range of 20-500 nm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a support film used for producing a plastic film by a casting method. Specifically, the present invention can produce a transparent film particularly for optical use with good productivity and has no deposit on the surface of the obtained cast film, and is used for optical applications. It is related with the support film for the outstanding manufacturing processes which can prevent the defect of this and can obtain a clear image for displays.

  In recent years, highly transparent films have been used for optical applications, and films having various functions have been used particularly in the display field. For example, in an LCD (liquid crystal) display, a polarizing film, a retardation film, a viewing angle enhancement film, a brightness enhancement film, a diffusion film, a reflection film, etc. In a PDP (plasma display panel) display, an electromagnetic wave cut, a near infrared cut, Films having functions such as ultraviolet cut and color tone correction are used as so-called PDP filters. Among these films, a film that is very highly transparent and has no optical anisotropy is required particularly in the LCD display field. A film satisfying such a requirement is a so-called solution casting method in which a raw material is limited, a film is highly transparent and is free from defects due to foreign matters, and the polymer is extruded into a sheet form as a solution and manufactured through a drying process. Is adopted. In addition, an optical recording medium used as a high-density recording medium for recording various kinds of information for computers, audios, and the like is manufactured in the same manner.

  When a film for optical use is formed by the solution casting method, a method using a metal endless belt or drum as a support and a method using a plastic or metal film or sheet are generally used. In particular, when a plastic film is used as a support, since it is excellent in transportability and flexibility, and the replacement of the support is relatively simple, it has been adopted as a method having a high degree of freedom in equipment design and use. In addition, since there is no problem of periodic appearance defects due to the step difference of the seam peculiar to an endless belt or the like, this method is suitable for obtaining a good film. Among them, a polyester film excellent in mechanical properties, heat resistance, dimensional stability, solvent resistance and the like is preferably used.

  When a polyester film is used as a support, the film is unrolled and travels while contacting several rolls and is carried to the casting process. In this process, the film is scraped by receiving some friction. If this happens, it will be transferred to a cast sheet and cause quality degradation when used for optics. In the casting process, the polymer is usually dissolved in a solvent at a high concentration and discharged from a slit-shaped die. When the support film is scraped by contact with the die, foreign matter adheres or stripe-like defects occur. And incurring quality degradation.

Regarding the polyester film used as the support in the casting process, it is strongly required that the transfer of foreign matters and the generation of streaks due to scraping of the support described above do not occur.
JP 2003-326542 A JP 2003-326543 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is that it is possible to efficiently and efficiently produce a transparent film particularly used for optics and the like, and foreign matter on the obtained cast film It is to provide an excellent support film for a manufacturing process capable of preventing defects when used in optical applications by preventing adhesion and streaking and obtaining a clear image for display. .

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problems can be easily solved by a film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is a film used as a support in a process for producing a plastic film by a solution casting method, and a layer constituting the cast surface of the film contains a polyester constituent other than the main polyester constituent. Production of a plastic film by a casting method, which is contained in a range of 2 to 25 mol%, Ra on the film surface is in a range of 3.0 to 20.0 nm, and Rt is in a range of 20 to 500 nm. It exists in the support film.

Hereinafter, the present invention will be described in more detail.
The support polyester film of the present invention is used in the step of forming a film by a solution casting method, but the material of the film-forming film is not particularly limited as long as such a step can be adopted. For example, a polycarbonate film, a polyarylate film, a triacetyl cellulose film, a norbornene resin film, a polyimide film, and the like can be used.

  In the present invention, the polyester is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, 1,4-butanediol, 1, 4-cyclohexanedimethanol etc. are mentioned. Typical polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN) and the like.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of the copolyester, it is a copolymer containing 40 mol% or less of the third component. Examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, and oxycarboxylic acid (for example, P -One kind or two or more kinds of oxybenzoic acid etc.), and the glycol component is one kind such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. Or 2 or more types are mentioned.

  The polyester film referred to in the present invention is a polyester film extruded by a so-called extrusion method in which the above-mentioned polyester is usually melt-extruded from an extrusion die, and is a film oriented in the biaxial direction of the vertical direction and the horizontal direction. It is. Further, the film may have a laminated structure using a so-called coextrusion method using two or more extruders. Such a laminated structure may be a two-layer structure of A / B, a three-layer structure of A / B / A or A / B / C, or a structure having a larger number of layers.

  In the film of the present invention, the layer constituting the cast surface when used as a support for producing a film by a casting method is a polyester constituent other than the main polyester constituents (dicarboxylic acid component and glycol component) (the dicarboxylic acid). It is necessary to comprise a polyester containing a dicarboxylic acid component or glycol component, which is a different kind from the acid component and glycol component, in the range of 2 to 25 mol%. Specifically, for example, when polyethylene terephthalate is used as the main polyester component, it contains 2 to 25 mol% of components constituting the polyester other than terephthalic acid and ethylene glycol. When such polyester is used, it is possible to prevent the polyester film from being scraped by contact with a roll or contact with a cast cap in the casting process, thereby reducing the quality of the cast film. That is, by using such polyester, it becomes difficult to cause abrasion due to contact with a hard material such as metal, and as a result, the quality of the cast sheet obtained in this application can be remarkably improved.

  When the film of the present invention is a single layer, that is, a film consisting of one layer, it is necessary that the film itself is made of the above-mentioned polyester, but A / B, A / B / A, A / B / C, etc. In the case of having the laminated structure, at least the layer constituting the cast surface may be made of the above-described polyester.

  Hereinafter, in the present invention, the layer constituting the cast surface will be described as layer A. The polyester constituting the A layer needs to contain the third polyester component in the range of 2 to 25 mol%, but such component may be one type or two or more types. . Further, the raw material may be produced as a copolymer and used as it is, or may be a blend of a copolymer and a homopolymer or a copolymer component or a copolymer having a different content. Components other than the main polyester constituents may be contained in total in an amount of 2 mol% or more, preferably 3 mol% or more, more preferably 5 mol% or more, and the upper limit is 25 mol%, preferably 20 It is mol%, More preferably, it is 15 mol%. If it is less than 2 mol%, the anti-shave effect of the present invention will be insufficient. On the other hand, if it exceeds 25 mol%, the crystallinity of the polymer is lowered and the solvent resistance in the casting process is insufficient, so troubles may eventually occur in the process of peeling from the cast film, or the surface of the cast film will be flat. As a result, problems such as deterioration in quality and deterioration in quality occur.

  When the polyester constituting the A layer of the film of the present invention has the following characteristics relating to the crystallization temperature in addition to the above-described requirements, the abrasion resistance can be highly improved. That is, the difference (Tc2−Tc1) between the crystallization exothermic peak temperature (Tc1) at the time of temperature rise measured by DSC and the crystallization exotherm peak temperature (Tc2) at the time of temperature drop after melting is preferably 40 ° C. or less, preferably When the temperature is 35 ° C. or lower, more preferably 30 ° C. or lower, the abrasion resistance of the surface of the layer A is highly improved, and the quality of the cast film can be prevented from being deteriorated due to adhesion of the cut material. Polyester is a polymer having crystallinity, but if the degree of crystallinity is too high, the polymer tends to be scraped off. Therefore, it is advantageous for the film of the present invention that crystallization by heat hardly occurs. On the other hand, if the crystallinity is lost, the solvent resistance is insufficient, the solvent is damaged when it comes into contact with the cast sheet containing the solvent, and the surface of the resulting cast sheet becomes extremely rough. Occur.

  The total thickness of the film is usually 25 to 300 μm, preferably 50 to 200 μm. If it is less than 25 μm, the mechanical strength and heat resistance of the film will be insufficient, and problems such as wrinkling of the film and curling of the obtained sheet will occur in the cast sheet manufacturing process, particularly in the drying process. There is. On the other hand, when the thickness of the film exceeds 300 μm, the stiffness of the film is too strong, and the handleability in the casting process may be poor.

  In the case of a laminated film, the thickness of the A layer is usually 0.1 μm or more, preferably 0.5 μm or more, and more preferably 1.0 μm or more. If it is less than 0.1 μm, the effect of the abrasion resistance of the film may be insufficient. On the other hand, the upper limit of the thickness is usually 30 μm or less because the effect of giving abrasion resistance exceeds 30 μm with respect to the thickness, and is usually 30 μm or less.

  Further, the mechanical strength and shrinkage ratio of the film itself are in an appropriate range, and the thickness of the A layer is 30% or less of the total thickness, further 20% or less, in order to improve the handleability and process suitability during casting. In particular, 10% or less is desirable. About layers other than A layer, it is preferable that content of an above-described copolymerization component is less than A layer, and it is still more preferable that a copolymerization component is less than 2 mol%.

  The polyester film of the present invention preferably contains fine particles in the film to form appropriate protrusions in order to improve surface slipperiness and improve handling without causing problems such as blocking. . Examples of such fine particles include inorganic particles such as silica, alumina, kaolin, clay, talc, calcium carbonate, titanium oxide, barium sulfate, lithium fluoride, organic particles such as calcium terephthalate and calcium oxalate, styrene-based, acrylic Examples thereof include crosslinked polymer particles such as a system, and so-called precipitated particles obtained by precipitating a catalyst and an auxiliary agent in a polyester production process. The average particle size of the fine particles to be blended is not particularly limited, but is usually 0.01 μm to 5 μm, preferably 0.02 μm to 3 μm, and more preferably 0.05 μm to 3 μm. When particles having an average particle size of less than 0.01 μm are used, protrusions having an effective height cannot be formed on the film surface, and the film is flattened and the winding characteristics in the film manufacturing process are inferior. In some cases, the surface of the film may be damaged. Further, when the average particle size exceeds 5 μm, the degree of roughening of the film surface becomes too large, and surface shape transfer occurs when used as a support in the casting process, resulting in an optical film In some cases, the quality of the film deteriorates and the surface of the film is easily scraped off, causing problems such as transfer to an optical film.

  In particular, it is preferable to add 0.05 to 1.00% by weight of alumina particles having an average primary particle size of 0.05 μm or less to the A layer. By blending such particles, the abrasion resistance of the film surface is further improved and scraped. The effect of preventing deterioration of cast film quality due to transfer of objects becomes high.

  Moreover, in this invention, the method of adding 2 or more types as an above-mentioned particle | grain as a particle type, or adding 2 or more types as an average particle diameter can be used. In particular, in order to improve the slipperiness of the surface and improve the handleability, particles having a small particle diameter are added, and in order to further improve the winding property, a large amount of particles smaller than the small particles is blended. A method is preferably employed. In this case, the average particle diameter of all the particles is in the above-described range, but the average particle diameter of the small particles is preferably 1.0 μm or less, and more preferably 0.8 μm or less. On the other hand, the larger particles preferably have an average particle size exceeding 1.0 μm, more preferably 1.3 μm or more. The blending amount of the particles is usually in the range of 0.001 to 5% by weight in the film, preferably in the range of 0.01 to 3% by weight, and more preferably in the range of 0.05 to 1% by weight. When two or more kinds of particles are contained, the total amount is preferably in the above range. In addition, when the film has a laminated structure by a coextrusion method or the like, it is desirable that the particle content of the layer forming the surface is in the above-described range.

  When the film is a single layer, the surface shape can be adjusted by blending the particles described above into the film. In addition, in the case of a laminated structure, the surface shape can be adjusted by blending particles into the layer forming the surface, but as another method, the particles can be blended into the inner layer of the surface layer to form the surface layer. Does not contain particles, or contains particles smaller than the particles contained in the inner layer, and the surface layer has a thickness in the range of 0.1 to 2.0 μm, and is projected on the surface by the particles mixed in the inner layer. A method of forming can also be adopted. For example, the A layer in the present invention is a thin layer having a thickness of 2.0 μm or less, and particles having an average particle diameter of 1.0 times or more the thickness of the A layer are blended in the inner layer to give an appropriate surface roughness. In addition, a method that satisfies a high degree of wear resistance can also be preferably employed. Further, in this case, by adding 0.05 to 1.00% by weight of alumina particles having an average primary particle size of 0.05 μm or less in the A layer, the abrasion resistance of the film surface can be further satisfied. .

  In the present invention, a film is provided with roughness on the surface by a method such as forming protrusions on the surface by such a method or blending particles in a coating layer to be described later, but the surface roughness Ra is 3 The range is from 0.0 to 20.0 nm, preferably from 4.0 to 18.0 nm, and more preferably from 5.0 to 10.0 nm. Rt is in the range of 20 nm to 500 nm, preferably in the range of 30 to 300 nm, and more preferably in the range of 40 to 150 nm. When the surface roughness of the film increases, the above-mentioned problem of shape transfer occurs. On the other hand, if the surface roughness is too small, the handling of the film will be inferior, so that the winding property during production will be hindered, or the surface during film running when used as a film production process or cast support Problems such as scratches will occur.

  In order to obtain such a surface shape of the support, in addition to setting the particles to be blended in the film to the above-mentioned particle size range, the particle size distribution value is 3.0 or less, further 2.5 or less, especially 2.2 or less. It is preferable that If the particle size distribution is sharp, coarse protrusions are not generated, and an extremely high effect as a support can be exhibited.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage of producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction, The polycondensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  Hereinafter, the polyester film of the present invention will be specifically described, but the present invention is not particularly limited to the following examples as long as the gist of the present invention is satisfied.

  First, the polyester chip is supplied to a melt extrusion apparatus, and the polymer is heated to a temperature equal to or higher than the melting point to melt. Next, the molten polymer is extruded from a slit-shaped die and rapidly cooled and solidified on the rotary cooling drum so as to have a temperature not higher than the glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times in the longitudinal direction at 70 to 145 ° C. to form a longitudinal uniaxially stretched film, and then in the transverse direction at 90 to 160 ° C. It is preferable to perform 2-6 times stretching and to heat-process at 150-240 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  In the present invention, two or more polyester melt extruders can be used to form a laminated film of two or more layers by a so-called coextrusion method. As the structure of the layer, A / B using A raw material and B raw material, or A / B / A structure, and further using a C raw material, a film having an A / B / C structure or a film having more layers can do.

  In order to maintain the abrasion resistance of the A layer at a high level, the intrinsic viscosity of the polyester constituting the A layer is preferably 0.60 or more, more preferably 0.62 or more, and particularly preferably 0.64 or more. In addition, since the film is scraped on both sides of the film, in order to maintain a high degree of cleanness in the process, the intrinsic viscosity is preferably set to the above-described range on both sides of the film. 55 or more, preferably 0.58 or more, and more preferably 0.6 or more. By setting it as the film which has an intrinsic viscosity of this range, it can be set as the film which has the durability required regarding the abrasion of a film, and fully satisfies the characteristic required in this use. On the other hand, the upper limit of the intrinsic viscosity is usually about 0.90 in order to keep the extrusion pressure problem in the film production process and the thickness uniformity when extruding the molten polymer from the slit-shaped die at a good level. More preferably, it should be lower than 80.

  In addition, the polyester film of the present invention has good wettability with the solvent at the time of casting and good uniformity such as the thickness of the cast sheet, and also has an appropriate peelability after removing the solvent to form a sheet. Therefore, a coating layer can be provided on the surface. In forming such a coating layer, the method of forming a film, in particular, after stretching in the longitudinal direction and before stretching in the lateral direction can form a very thin coating layer, and the coating solution drying and curing reaction Is preferable in that it can be carried out in the film forming process. The coating layer is preferably composed of a combination of a crosslinking agent and various binder resins, and as the binder resin, at least one polymer selected from polyester, acrylic polymer and polyurethane is used in combination from the viewpoint of adhesiveness. To do. Each of the above polymers shall also include derivatives thereof. The derivative here refers to a polymer obtained by reacting a reactive compound with a copolymer or a functional group with another polymer. Polyvinylidene chloride, chlorinated polyolefin, etc. also form a tough film and show good adhesion to the topcoat, but since these contain chlorine, they can generate harmful dioxin compounds containing chlorine during combustion. This is not preferable in this respect. Further, when the scrap of the coated film is reused, there is a problem of coloring and generation of corrosive gas, which is not preferable in this respect.

  As the crosslinking agent resin, melamine-based, epoxy-based, and oxazoline-based resins are generally used, but melamine-based resins are particularly preferable from the viewpoints of coatability and durable adhesiveness. The melamine-based resin is not particularly limited, but melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting methylolated melamine with a lower alcohol, And a mixture thereof can be used.

  In the present invention, it is preferable to contain inorganic particles or organic particles in the coating layer in order to further improve the slipperiness, adhesion and the like. The amount of the particles in the coating agent is usually 0.5 to 10% by weight, preferably 1 to 5% by weight. When the blending amount is less than 0.5% by weight, the blocking resistance may be insufficient. When the blending amount exceeds 10% by weight, the transparency of the film is hindered. Tend to be.

  Examples of the inorganic particles include silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black, molybdenum sulfide, and antimony oxide. Among these, silicon dioxide is easy to use because it is inexpensive and has various particle sizes.

  Examples of the organic particles include polystyrene or polyacrylate polymethacrylate in which a crosslinked structure is achieved by a compound (for example, divinylbenzene) containing two or more carbon-carbon double bonds in one molecule.

  Further, the coating layer may contain an antistatic agent, an antifoaming agent, a coating property improving agent, a thickener, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like.

  As a coating method of the coating agent, for example, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating apparatus other than these as shown in Yuji Harasaki, Tsuji Shoten, published in 1979, “Coating Method” Can be used.

  The coating layer may be formed only on the surface of the A layer or on both surfaces. When formed only on one side, other characteristics can be imparted by forming a coating layer different from the above-mentioned coating layer on the opposite surface as necessary. In addition, in order to improve the applicability | paintability and adhesiveness to the film of a coating agent, you may give a chemical process and an electrical discharge process to a film before application | coating. Further, in order to further improve the surface characteristics, a discharge treatment may be performed after the coating layer is formed.

  The thickness of the coating layer is usually in the range of 0.02 to 0.5 μm, preferably 0.03 to 0.3 μm, as the final dry thickness. When the thickness of the coating layer is less than 0.02 μm, the effect of the present invention may not be sufficiently exhibited. When the thickness of the coating layer exceeds 0.5 μm, the films tend to stick to each other, and particularly when the coated film is re-stretched to increase the strength of the film, it adheres to the roll in the process. There is a tendency to become easy. The above problem of sticking appears particularly when the same coating layer is formed on both sides of the film. In addition, when it has a coating layer, Ra and Rt of the coating layer surface need to satisfy the said range.

  The polyester film of the present invention can be mixed with other thermoplastic resins such as polyethylene naphthalate and polytrimethylene terephthalate as long as the effects of the present invention are not impaired. Moreover, you may mix | blend coloring agents, such as a ultraviolet absorber, antioxidant, surfactant, a fluorescent whitening agent, a lubricant agent, a light-shielding agent, a matting agent, and a dye, a pigment.

  Next, a method for producing a film suitable for optical use by a casting method using the film of the present invention will be described. In the production of the cast method film of the present invention, the resin composition solution is cast on a support film to form a film, and the film used at that time is the polyester film of the present invention. By using the polyester film as the support, it is possible to prevent the appearance defect due to the joint, which is a problem when using a metal endless belt, from occurring. In addition, in the case of a metal endless belt, there is a problem that it takes enormous labor and cost for processing such as when the metal surface is scratched for some reason, but it is required by using the film of the present invention as a support. The problem is solved. In addition to the polyester film, the support other than the endless belt includes a metal film or a sheet-like molded body. However, the transportability, the flexibility for deformation, the re-collection by winding, the ease of reuse, etc. Therefore, a support made of plastic, especially a polyester film, is preferable to a metal.

  Examples of the material of the sheet or film obtained by the casting method include, but are not limited to, polycarbonate, norbornene resin, triacetyl cellulose, polyimide, polyarylate, and aromatic polyamide. In a normal solution casting method, a resin composition is dissolved in an appropriate solvent to prepare a solution, the solution is cast on a support by casting or coating, and then dried to form a film. When the film of the present invention is used as the support, the support film can be wound up without being peeled after the drying process. Usually, the surface opposite to the surface in contact with the support of the film produced by the casting method is an extremely flat surface, so that problems such as insufficient slipping and scratches on the surface are likely to occur. On the other hand, it can be said that it is advantageous in that appropriate slipperiness can be imparted and scratches can be prevented by winding the polyester film of the support without peeling.

  As described above in detail, since the film of the present invention has a specific surface shape, it can be obtained when a plastic film used for an optical application is used as a support in producing by a casting method. The surface flatness and transparency of the cast film are very highly satisfied, and its industrial value is superior to its conventional method using endless belts, because its quality and process efficiency are good. Is expensive.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. In the examples and comparative examples, “parts” means “parts by weight”. The measuring method used in the present invention is as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measurement was performed at 30 ° C. For the measurement of the intrinsic viscosity of only the surface layer, in the process of coextrusion from the melt extruder, the method of measuring the intrinsic viscosity of the polyester extruded with the same discharge amount, or the surface layer only using a suitable tool such as a knife It was scraped off and used for measurement.

(2) Average particle size (d50) and particle size distribution value (d25 / d75)
The size of the particles was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation. The average particle diameter (d50) was determined using a value of 50% of integration (weight basis) in the equivalent spherical distribution of the measured particles. Further, integration was performed from the large particle side in the equivalent spherical distribution measured with the same apparatus, and the particle size distribution value (d25 / d75) was obtained from the following equation.
Particle size distribution value = (particle size when the cumulative weight of particles is 25%) ÷ (particle size when the cumulative weight of particles is 75%)
The particle size distribution value has a sharper particle size distribution as it approaches 1.0.

(3) Centerline average roughness (Ra) and maximum height (Rt)
It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-sectional curve in the direction of the center line, and the roughness curve y = where the center line of the extracted portion is the x axis and the direction of the vertical magnification is the y axis. When expressed by f (x), the value given by the following formula was defined as the centerline average roughness (Ra), and expressed in [nm]. The maximum height (Rt) is determined by setting the distance between the two straight lines in the direction of the vertical magnification of the cross-sectional curve when the extracted part is sandwiched by two straight lines parallel to the average line of the extracted part of the film cross-sectional curve obtained above. The measured value was the maximum height (Rt) and expressed in [nm]. The maximum height and the center line average roughness were expressed as average values of the respective values of the extracted portions obtained from 10 cross-sectional curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.
Ra = (1 / L) ∫ | f (x) | dx

(4) Exothermic peak temperature due to crystallization A DSC apparatus “MDSC 2920 type” manufactured by TI Instruments Inc. was used, and measurement was performed under the following conditions. That is, about 5 mg of polymer was sampled and set in a DSC apparatus, and the temperature was raised from room temperature to 300 ° C. at a rate of 20 ° C./min under a nitrogen stream and held for 5 minutes. A sample was removed and quenched with liquid nitrogen. This sample was set again in the DSC apparatus, and the temperature was raised from room temperature to 300 ° C. at a rate of 10 ° C./min to obtain a DSC curve. The peak temperature (Tc1) of exotherm due to crystallization of the polymer obtained in this measurement was read. After maintaining at 300 ° C. for 5 minutes, the temperature was lowered at a rate of 5 ° C./min, and the peak temperature (Tc2) of exotherm due to crystallization was read. When measuring the polymer of layer A of the laminated film, use the polymer obtained by extruding the raw material of layer A under the same melt extrusion conditions, or scrape the surface layer with a suitable knife or the like to remove the polymer. Were collected.

(5) Quality of cast film A 20 wt% solution of polycarbonate was prepared using dichloromethane as a solvent.
This solution is applied onto a support film, primarily dried at 70 ° C., and further dried at 100 ° C. until the amount of residual solvent in the cast film is 0.5% by weight or less, and wound together with the support film. It was. The obtained cast film had a thickness of 45 μm. The cast film was evaluated by peeling the support film. In addition, in order to obtain the product of a cast film, the protective film which has an adhesive layer may be bonded together, but in this invention, evaluation of the cast film was performed immediately after peeling a support body. The evaluation criteria were as follows.

-Transparency of film Rank A: Obtained as a highly transparent film and high quality as an optical member.
Rank B: Transparent and usable as an optical member, but slightly inferior to A.
Rank C: Inferior in transparency and cannot be used as an optical member.
・ Optical defects (observed visually under crossed Nicols using two polarizing plates)
Rank A: 1 defect / m2 or less Rank B: 3 defects / m2 or less Rank C: 20 defects / m2 or less

Film winding characteristics Rank A: Obtained as a highly transparent film and high quality as an optical member.
Rank B: Transparent and usable as an optical member, but slightly inferior to A.
Rank C: Practically hindered as an optical member.

The production method of the polyester used in the following examples and comparative examples is as follows.
<Manufacture of polyester>
[Production Method of Polyester (a)]
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After 0.04 part of ethyl acid phosphate was added to this reaction mixture, 0.035 part of antimony trioxide was added and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.67 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (a) was 0.67.

[Method for producing polyester (b)]
In the method for producing polyester (a), the same method as the method for producing polyester (a) was used except that starting materials were 80 parts by weight of dimethyl terephthalate, 20 parts by weight of dimethyl isophthalate and 60 parts by weight of ethylene glycol. Thus, polyester (b) was obtained. The obtained polyester (b) had an intrinsic viscosity of 0.68.

[Production method of polyester (c)]
In the method for producing polyester (a), after adding 0.04 part of ethyl acid phosphate, styrene-based crosslinked polymer particles having an average particle size of 0.35 μm and a particle size distribution value of 1.95 dispersed in ethylene glycol were added to 0. .3 parts and 0.04 part of antimony trioxide were added, and the polyester (a) was prepared using the same method as the production method of polyester (a) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.66. c) was obtained. The obtained polyester (c) had an intrinsic viscosity of 0.67.

[Production method of polyester (d)]
In the production method of the polyester (c), the same method as the production method of the polyester (c) is used except that the particles to be added are alumina particles having an average primary particle size of 0.02 μm and the addition amount is 1.0 part. Used to obtain a polyester (d). The obtained polyester (d) had an intrinsic viscosity of 0.64.

[Production method of polyester (e)]
In the method for producing polyester (c), the method is the same as the method for producing polyester (c) except that the particles to be added are amorphous silica particles having an average particle diameter of 2.5 μm and the addition amount is 0.3 parts. Was used to obtain a polyester (e). The obtained polyester (e) had an intrinsic viscosity of 0.66.

[Production method of polyester (f)]
The starting material is 100 parts by weight of dimethyl terephthalate, 54 parts by weight of ethylene glycol and 25 parts by weight of 1,4-cyclohexanedimethanol, 0.008 parts by weight of tetrabutoxy titanate is used as a catalyst, and the reaction start temperature is 150 ° C. The reaction temperature was gradually increased with the distillation of methanol, and the temperature was raised to 230 ° C. after 3 hours, and the reaction was continued for another hour. Thereafter, the temperature of the reaction product was gradually raised from 230 ° C., and the pressure was gradually reduced from the normal pressure, and finally the temperature was 280 ° C. and the pressure was 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.70 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (f) was 0.70.

  The raw materials obtained by mixing 50 parts of the polyester (b) and 50 parts of the (c) are used as raw materials for the A layer and the B layer, and the polyester (a) is used as a raw material for the C layer. After each melted at 285 ° C., the A layer and the B layer are the outermost layer (surface layer), the C layer is the intermediate layer, and a three-layer three-layer (A / C / B) layer on a casting drum cooled to 40 ° C. The composition was coextruded and cooled and solidified to obtain a non-oriented sheet. Next, the film was stretched 3.3 times in the machine direction at a film temperature of 81 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 3.6 times in the transverse direction at 120 ° C., and heat-treated at 225 ° C. Thereafter, the film was relaxed by 2% in the lateral direction to obtain a laminated polyester film having a thickness of 125 μm. The thickness of each layer of the obtained film was 15/95/15 μm. Further, the intrinsic viscosity of the polyester of the A layer and the B layer extruded under the same conditions was 0.64.

  In Example 1, the raw material for layer A and layer B was the same as in Example 1 except that a raw material in which 50 parts of polyester (b), 30 parts of polyester (c) and 20 parts of polyester (e) were mixed was used. Thus, an (A / C / B) laminated polyester film having a total thickness of 125 μm was obtained. The intrinsic viscosity of the polyester of layer A and layer B extruded under the same conditions was 0.65.

  Example 1 is the same as Example 1 except that a raw material obtained by mixing 38 parts of polyester (a), 12 parts of polyester (b) and 50 parts of polyester (c) is used as the raw material for the A layer and the B layer. Thus, an (A / C / B) laminated polyester film having a total thickness of 125 μm was obtained. The intrinsic viscosity of the polyester of layer A and layer B extruded under the same conditions was 0.64.

  In Example 1, 50 parts of polyester (b), 30 parts of polyester (c) and 20 parts of polyester (d) are mixed as the A layer material, and 50 parts of polyester (a) and polyester (c) are mixed as the B layer material. ) A (A / C / B) laminated polyester film having a total thickness of 125 μm was obtained in the same manner as in Example 1 except that a raw material mixed with 50 parts was used. The intrinsic viscosity of the polyesters of layer A and layer B extruded under the same conditions was 0.65.

  In Example 1, 80 parts of polyester (b) and 20 parts of polyester (c) were mixed as the A layer material, and 50 parts of polyester (a) and 50 parts of polyester (c) were mixed as the B layer material. A (A / C / B) laminated polyester film having a total thickness of 125 μm was obtained in the same manner as in Example 1 except that the raw materials were used. The intrinsic viscosity of layer A polyester extruded under the same conditions was 0.66, and the intrinsic viscosity of layer B polyester was 0.65.

  In Example 1, the raw materials for the A layer and the B layer were the same as in Example 1 except that 20 parts of polyester (a), 50 parts of polyester (c) and 30 parts of polyester (f) were mixed. A (A / C / B) laminated polyester film having a thickness of 125 μm was obtained. The intrinsic viscosity of the polyester of layer A and layer B extruded under the same conditions was 0.66.

  In Example 1, A layer raw material was supplied to one extruder, and (A) it was set as the single layer, and the film was obtained. A polyester film having a thickness of 125 μm was obtained. The intrinsic viscosity of the polyester of layer A extruded under the same conditions was 0.65. The quality of the optical film produced using the obtained film was equivalent to that of Example 1, but the cost for obtaining the polyester film was higher than that of Example 1, which was disadvantageous in this respect. It became.

(Comparative Example 1)
In Example 1, the raw material of the A layer and the B layer was the same as in Example 1 except that 50 parts of polyester (a) and 50 parts of polyester (c) were mixed (A / C / B) A laminated polyester film was obtained. The intrinsic viscosity of the polyester of layer A and layer B extruded under the same conditions was 0.65.

(Comparative Example 2)
In Example 1, the raw material of the A layer and the B layer was the same as that of Example 1 except that 40 parts of polyester (b) and 60 parts of polyester (e) were mixed (A / C / B) A laminated polyester film was obtained. The intrinsic viscosity of the polyester of layer A and layer B extruded under the same conditions was 0.64.

(Comparative Example 3)
In Example 1, 70 parts of polyester (a) and 30 parts of polyester (b) were mixed as the A layer material, and 50 parts of polyester (b) and 50 parts of polyester (c) were mixed as the B layer material. A (A / C / B) laminated polyester film having a total thickness of 125 μm was obtained in the same manner as in Example 1 except that the raw materials were used. The intrinsic viscosity of the polyesters of layer A and layer B extruded under the same conditions was 0.65.
The obtained results are summarized in Table 1 below.

  The film of the present invention can be used as, for example, a support film used for producing a plastic film by a casting method.

Claims (3)

A film used as a support in a process of producing a plastic film by a solution casting method, wherein the layer constituting the cast surface of the film contains a polyester constituent other than the main polyester constituent in a range of 2 to 25 mol%. A support film for producing a plastic film by a casting method, characterized in that Ra on the surface of the film is in the range of 3.0 to 20.0 nm and Rt is in the range of 20 to 500 nm. The polyester film having a laminated structure by a coextrusion method, wherein the thickness of the layer constituting the cast surface is 0.1 to 30 µm, and the thickness of the layer is 30% or less of the total thickness. A support film for producing a plastic film according to the casting method according to 1. The difference (Tc2−Tc1) between the crystallization exothermic peak temperature (Tc1) at the time of temperature rise of the polymer constituting the cast surface and the crystallization exothermic peak temperature (Tc2) at the time of temperature drop after melting, It is 40 degrees C or less, The support film for plastic film manufacture by the casting method of Claim 1 or 2 characterized by the above-mentioned.