JP5451438B2 - Film production method - Google Patents

Description

  The present invention relates to a film manufacturing method, and more particularly to a film manufacturing method used for a base film of a high-density magnetic recording medium.

  Thermoplastic resins such as polyester are used as raw materials for films and the like because of their excellent moldability. When this film is used, the required properties differ depending on the application, but in applications where flatness is required such as a base film of a magnetic recording medium, it is required that there are no surface defects.

In response to such a requirement, in Patent Documents 1 to 4, aluminum is vapor-deposited on the surface of the film with a thickness of 0.1 μm, and the surface is observed at a magnification of 200 times with an optical microscope in a 1 cm × 5 cm range, A projection having a major axis of 15 μm or more is marked, and the marked projection is measured using a non-contact three-dimensional roughness meter under a measurement magnification of 40 times and a measurement area of 242 μm × 239 μm (0.058 mm ² ). The number of protrusions having a height of 100 nm or more is counted. In Patent Document 5, light with a wavelength of 580 nm is irradiated, and surface defects are measured by the interference fringes.

  However, in the methods described in Patent Documents 1 to 4, the measurement area is very narrow, and the projections can only be seen having a major axis of 15 μm or more. It was not possible to use it in terms of productivity and credibility. On the other hand, since the method described in Patent Document 5 has a measurement wavelength of 580 nm, a surface defect having a relatively wide range can be easily confirmed as long as the surface defect has a height of 145 nm or more. On the other hand, the demands of the market in recent years have become increasingly higher, and protrusions whose height is less than 145 nm have become a problem as surface defects.

JP 2004-114492 A JP 2003-291288 A JP 2002-36311 A JP 2002-363310 A JP 2002-59520 A

  An object of the present invention is to provide a film production method capable of efficiently producing a film having few surface defects that can meet the market demand for reducing surface defects of very low height in recent years. is there.

  When the present inventors diligently research to solve the above-mentioned problem, the same principle as the method described in Patent Document 5 is adopted as a measurement method, and interference fringes due to extremely short wavelength light that has not been conventionally used as a measurement wavelength. Can be used to efficiently grasp surface defects with relatively low height, which has not been a problem until now, and as a result, it is suitable for base films of high-density magnetic recording media with few surface defects. The present inventors have found that a film can be produced efficiently and have reached the present invention.

Thus, according to the present invention, a melt extrusion process for extruding a molten thermoplastic resin into a sheet shape, a process for winding it, and a process for selecting a good product as a good product by sorting the wound film into a good product and a defective product A method for producing a film comprising the steps of: affixing at least one surface of a wound film to a transparent substrate, and irradiating light having a wavelength of 100 to 400 nm from the transparent substrate side; A film that measures the number of surface defects measured by interference fringes of reflected light reflected at the boundary between the gap and the gap and the boundary between the film surface, and a film having a measured number of surface defects equal to or less than a reference value A manufacturing method is provided.

  Furthermore, as a preferred embodiment of the present invention, the surface roughness of at least one of the films is in the range of 1 to 10 nm, the molten thermoplastic resin is filtered by a filter in the melt extrusion process, and the number of surface defects is increased. Based on the measured value, the filter is replaced. In the process of extruding the sheet and then winding it, the roll to be used is cleaned based on the measured value of the number of surface defects, and the film is polyester. There is also provided a method for producing a film comprising at least one of being a film and being used as a base film of a high-density magnetic recording medium.

  According to the method for producing a film of the present invention, when used in a base film of a high-density magnetic recording medium such as a data storage having a storage capacity of 1 TB or more in the film, defects such as dropout hardly occur. The film can be produced efficiently and its industrial value is extremely high.

Hereinafter, the present invention will be described in detail.
The method for producing a film according to the present invention includes a step of extruding a molten thermoplastic resin into a sheet, a step of winding it, and a step of selecting the non-defective product from the wound film as a non-defective product It consists of. For the step of extruding the molten thermoplastic resin into a sheet and the step of winding it, a method known per se can be adopted.

  First, the feature of the present invention is that the number of surface defects measured by interference of light having a wavelength of 100 to 400 nm is measured on at least one surface of the wound film, and the measured number of surface defects is below a reference value. It is to make the film a good product. When the measurement wavelength is less than the lower limit, the observed protrusions are very small, and it is difficult to accurately grasp the number of protrusions even in the manufacturing method of the present invention. On the other hand, when the measurement wavelength exceeds the upper limit, only a large surface defect as measured in the above-mentioned Patent Document 5 can be confirmed, and there are cases where it is insufficient even if judged as a non-defective product. A preferable wavelength of light is in the range of 150 to 350 nm, and further 200 to 300 nm.

  The measurement principle of the surface defect due to the interference fringes will be described. First, when the film is overlapped on a flat surface, there is a protrusion between the two because there is a protrusion on the surface of the film. When the light hits the reflected light, the reflected light cancels out at an interval of λ / 4 with respect to the wavelength of light (λ: nm). By this cancellation, a black dot or a black ring-shaped pattern appears around the protrusion, and the surface defect can be grasped by confirming them.

  What is important in the present invention is that light having a wavelength in the above-mentioned range is used as light to be irradiated. Since light in such a wavelength region cannot be confirmed with the naked eye, when actually measuring, the light receiving unit having sensitivity to the light with the measurement wavelength and the interference fringes of the light observed with the light receiving unit with the naked eye. An arithmetic device that performs conversion so that it can be confirmed, an image display device that displays the converted interference fringes, and a printing device that performs printing are required. Moreover, the light to irradiate should just contain the light of the said wavelength, and may contain the light of another wavelength. This can be done by passing a filter that passes only a specific wavelength before or after irradiating the film, or by adopting a light receiving part that can confirm only the specific wavelength as the light receiving part. This is because interference fringes due to light of the target wavelength can be confirmed.

  By the way, in Patent Document 5, measurement is performed by superimposing films to be measured. However, when the wavelength is shortened, the thermoplastic resin itself constituting the film absorbs light, and interference fringes may be difficult to judge. In such a case, a transparent base material such as a glass plate that absorbs light at the measurement wavelength is small, a film is attached to the transparent base material, and light is irradiated from the transparent base material side. By doing this, interference fringes caused by reflected light (light that does not pass through the film) reflected at the boundary between the transparent substrate and the gap and between the gap and the film surface can be observed, and the problem of absorption of the measurement light by the film can be observed. Measurements can be avoided.

  The surface defect due to such interference fringes may be measured at an arbitrary stage as long as the film is wound up and used as a product. However, if surface defects increase for some reason while the film is being formed, only defective products will be produced unless this measurement is made. It is particularly preferable to measure within 8 hours, more preferably within 4 hours.

Next, the step of extruding the thermoplastic resin into a sheet will be described in detail.
First, as long as the thermoplastic resin in the present invention can be formed into a film, a known one can be adopted, such as polyester resin, polycarbonate resin, polyamide resin, polyimide resin, polyvinyl resin. Resin and polyolefin resin can be used, and polyester resin (hereinafter simply referred to as polyester) is particularly preferable. Among polyesters, an aromatic polyester obtained by polycondensation of a diol component and an aromatic dicarboxylic acid component is preferable from the viewpoint of reducing mechanical properties and surface defects. Examples of the aromatic dicarboxylic acid component include terephthalic acid and isophthalic acid. 6,6 ′-(alkylenedioxy) di-2 such as acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid -Naphthoic acid is mentioned, and examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol. Among these, ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate is the main repeating unit from the viewpoint of dimensional stability during processing at high temperature, and ethylene-2,6-naphthalene is particularly preferable. Those having carboxylate as the main repeating unit are preferred. Further, from the viewpoint of further improving the dimensional stability against environmental changes, the 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component described in International Publication No. 2008/096612 pamphlet, 6,6 ′-( A copolymer obtained by copolymerizing a trimethylenedioxy) di-2-naphthoic acid component and a 6,6 ′-(butylenedioxy) di-2-naphthoic acid component is also preferred.

  By the way, it is preferable that the thermoplastic resin used in the method for producing a film of the present invention has as few foreign substances as possible that cause surface defects. The foreign substances that cause such surface defects include foreign substances contained in the raw material of the thermoplastic resin itself, foreign substances that enter during the process of manufacturing the thermoplastic resin and film, and the process of manufacturing the thermoplastic resin. It is preferable to reduce foreign substances as much as possible by adopting a method known per se.

  In reducing such foreign matter, as a method that is relatively simple and can cope with various foreign matters, when extruding the thermoplastic resin into a sheet, that is, between the molten state and the extrusion of the thermoplastic resin, Filtering with a filter can be mentioned. The filter used for the filtration may be a known filter as appropriate depending on the target level of surface defects. In general, a filter with a smaller 95% filtration accuracy (the particle size of glass beads that remain on the filter without passing glass beads of 95% or more when glass beads are passed) removes smaller foreign matters. be able to. Therefore, from the viewpoint of reducing foreign matters that cause minute surface defects, which is a problem in the present invention, the 95% filtration accuracy of the filter used is 1.5 μm or less, further 1.3 μm or less, particularly 1.0 μm or less. preferable. On the other hand, the smaller the 95% filtration accuracy is, the more foreign substances can be removed, which means that foreign substances trapped without passing through the filter are collected earlier. If foreign matter that cannot pass through such a filter accumulates, the amount of the thermoplastic resin that can pass through the filter is reduced even when the thermoplastic resin is filtered, and the amount when extruded into a sheet becomes unstable. The trapped foreign matter leaks from the filter under the pressure of pushing out the thermoplastic resin. Therefore, the lower limit of 95% filtration accuracy of the filter is preferably 0.2 μm or more, more preferably 0.3 μm or more, and particularly preferably 0.4 μm or more. In addition, when the accumulated foreign matter leaks out, the subsequent products become defective products, but according to the manufacturing method of the present invention, it is possible to quickly grasp the occurrence of such defective products, for example, By exchanging the filter or the like, it is possible to suppress the occurrence of defective products thereafter, and the filter is not excessively replaced, which is extremely beneficial from the viewpoint of productivity.

  By the way, from the viewpoint of reducing the number of minute surface defects, the film produced by the production method of the present invention preferably has a surface roughness (RaA) in the range of 1 to 10 nm. Preferred RaA is in the range of 1-9 nm, more preferably 2-9 nm. For example, from the viewpoint of maintaining high electromagnetic conversion characteristics when data storage is used, RaA is preferably in the range of 1 to 4 nm, and more preferably 2 to 4 nm. If RaA is less than the lower limit, the transportability and winding property are poor and wrinkles may be formed. On the other hand, when the upper limit is exceeded, the surface becomes too rough, and it becomes difficult to discriminate between non-defective products and defective products by the manufacturing method of the present invention. Even if the manufacturing method of the present invention is used, generation of defective products becomes difficult to hold down.

  Moreover, even if the film manufactured with the manufacturing method of this invention comprises the above-mentioned surface roughness (RaA), the thermoplastic resin which forms the surface does not contain or contains an inert particle. Inert particles having an average particle size of 0.05 to 0.5 μm, further 0.07 to 0.4 μm, based on the weight of the polyester forming the surface, 0.005 to 0.2 wt%, and further 0 It is preferably contained in the range of 0.007 to 0.2% by weight. In addition, for example, from the viewpoint of maintaining high electromagnetic conversion characteristics when data storage is performed, the thermoplastic resin forming the surface does not contain or contain inert particles, but has an average particle size of 0.05 to 0.15 μm, further 0.07 to 0.14 μm of inert particles, based on the weight of the polyester forming the surface, 0.005 to 0.2% by weight, further 0.007 to 0.18% by weight It is preferable to contain in the range. The term “not containing inert particles” as used herein means that the content of inert particles having an average particle size of 0.05 μm or more is less than 0.005% by weight.

  The inert particles to be contained are preferably inert particles which have no coarse particles or have a very small particle size distribution even if they are contained, and in which most of the primary particles are dispersed without agglomerating in the polymer. Such inert particles are preferably at least one particle selected from the group consisting of organic polymer particles such as silicone resin, crosslinked acrylic resin, crosslinked polyester, crosslinked polystyrene, and spherical silica, and particularly silicone resin. Preferably, the particles are at least one particle selected from the group consisting of crosslinked polystyrene and spherical silica. Of course, when these inert particles are contained, in order to further eliminate coarse particles, filtration with a filter, treatment of the surface of the inert particles with a dispersant, and strengthening of kneading with an extruder are performed. Is preferred.

  The film produced by the production method of the present invention is not particularly limited as long as it has the aforementioned surface roughness, and may be a single layer film or a laminated film composed of two or more polyester layers. In the case of a laminated film, if at least the surface on which the surface defect is measured by the production method of the present invention satisfies the above-mentioned surface roughness and inert particles, the other surface is not limited thereto, but the surface defect is reduced. From this point of view, it is preferable that both surfaces are satisfied.

  Next, a more preferable aspect of the film production method of the present invention will be described. First, polyester will be described as an example. For example, a first reaction in which an aromatic dicarboxylic acid or an ester-forming derivative thereof and an alkylene glycol are esterified or transesterified to synthesize a polyester precursor, It consists of a second reaction for polycondensation reaction, and a method known per se can be adopted. As described above, in order to reduce foreign substances derived from raw materials, it is preferable to repeat purification of the raw materials such as aromatic dicarboxylic acid or its ester-forming derivative and alkylene glycol to reduce foreign substances. If there are many foreign substances here, foreign substances may not be removed even by the filtration described above, and surface defects may increase.

  The raw material thus purified becomes a polyester precursor by the first reaction described above. This polyester precursor is filtered through a first filter having a 95% filtration accuracy of 10 μm or less before the second reaction is started, and when the resulting polyester is dissolved with tetraethylene glycol, the pore size is 8 μm. The purpose is to reduce the amount of insoluble coarse particles that cannot pass through the filter. Preferably, based on the weight of the polyester obtained, the amount of insoluble coarse particles that cannot pass through a straight filter having a pore diameter of 8 μm is 200 / mg or less, more preferably 150 / mg or less, particularly on the surface on the side where the magnetic layer is formed. The polyester used is preferably filtered through the first filter so that it is 40 pieces / mg or less, most preferably 30 pieces / mg or less. By reducing the amount of insoluble coarse foreign matter in this way, it becomes easier to further reduce the amount of insoluble coarse foreign matter by filtration after the second reaction described later. The filtration with the first filter is not limited to one time. If necessary, the filtration may be repeated further, or the filters may be used in multiple layers. Accordingly, the filtration accuracy of the first filter performed between the first reaction and the second reaction is preferably as small as possible from the viewpoint of reducing insoluble coarse foreign matter, and the 95% filtration accuracy is further 8 μm or less, further 5 μm or less. preferable. On the other hand, the lower limit of the 95% filtration accuracy of the first filter is not particularly limited. However, since the replacement cycle becomes shorter as the filter becomes smaller, it is preferably 3 μm or more, and more preferably 4 μm or more from the viewpoint of productivity. . In addition, the first filter has a structure in which metal fiber nonwoven fabrics are laminated, and the porosity of the laminated metal nonwoven fabrics is usually in the range of 40 to 80%. It is preferable because it can withstand. Although it is preferable to reduce the amount of such insoluble coarse foreign matter as much as possible from the raw material stage, it is difficult to remove it alone, and it is simple and extremely effective to remove it by filter filtration after the first reaction.

  Further preferable conditions for the first reaction will be described. The first reaction may be performed under normal pressure, but is preferably performed under a pressure of 0.05 MPa to 0.5 MPa because the reaction rate can be easily increased. Moreover, it is preferable to perform the temperature of a 1st reaction in the range of 210 to 270 degreeC. By making the reaction pressure within the above range, it is possible to suppress the generation of by-products typified by dialkylene glycol while facilitating the progress of the reaction. At this time, the alkylene glycol component is preferably used in an amount of 1.1 to 6 moles relative to the acid component present in the reaction system in which the first reaction is carried out from the viewpoint of maintaining the reaction rate and the physical properties of the resin. More preferably, it is 2-5 mol times, More preferably, it is 3-5 mol times.

  Further, in order to increase the reaction rate of the first reaction, it is preferable to use a catalyst known per se, for example, a metal compound having a metal component such as Li, Na, K, Mg, Ca, Mn, Co, and Ti. Among these, when performing under pressure, Mn and Ti compounds are preferable from the viewpoint of easy progress of the reaction. In particular, a Ti compound is preferable because it can be used as a polycondensation reaction catalyst, and the catalyst residue is less precipitated. The titanium compound used in the present invention is preferably an organic titanium compound that is soluble in polyester from the viewpoint of suppressing the generation of insoluble coarse particles due to precipitation of catalyst residues. Particularly preferable examples of the titanium compound include titanium tetraisopropoxide, titanium tetrapropoxide, titanium tetrabutoxide, titanium tetraethoxide, titanium tetraphenoxide, and trimellitic acid titanium.

  The amount of catalyst to be added is preferably in the range of 10 to 150 mmol%, more preferably 20 to 100 mmol%, especially 30, in terms of metal elements, based on the number of moles of all acid components present in the first reaction. It is preferable to be in the range of ˜70 mmol% because the reaction rate can be promoted, the formation of coarse insoluble foreign matters due to the catalyst can be suppressed, and the heat resistance of the resulting copolymerized aromatic polyester can be maintained at a high level. In addition, when adding a titanium compound, it is preferable to add so that it may exist from the time of the esterification reaction start of a 1st reaction, and as above-mentioned, it uses continuously as a polycondensation reaction catalyst. Of course, it may be added in two or more times for the purpose of controlling the polycondensation reaction rate.

Next, the second reaction in which the precursor obtained in the first reaction is polycondensed will be described.
In the present invention, for the purpose of imparting a high degree of thermal stability to the obtained polyester, it is preferable to add a thermal stabilizer composed of a phosphorus compound to the reaction system before the start of the polycondensation reaction in the second reaction. The specific phosphorus compound is not particularly limited as long as it has a phosphorus element in the compound. For example, phosphoric acid, phosphorous acid, phosphoric acid trimethyl ester, phosphoric acid tributyl ester, phosphoric acid triphenyl ester, phosphorus Examples include acid monomethyl ester, phosphoric acid dimethyl ester, phenylphosphonic acid, phenylphosphonic acid dimethyl ester, phenylphosphonic acid diethyl ester, ammonium phosphate, triethylphosphonoacetate, methyldiethylphosphonoacetate, and these phosphorus compounds May use 2 or more types together. The phosphorus compound is preferably added during the initial stage of the polycondensation reaction, which is the second reaction, after the first reaction is substantially completed. The addition may be performed at one time or two or more times. You may divide into.

  By the way, the polycondensation reaction is preferably performed at a temperature in the range of 270 ° C. to 300 ° C., and the pressure during the polycondensation reaction is preferably performed under a reduced pressure of 50 Pa or less. If the pressure during the polycondensation reaction is higher than the upper limit, the time required for the polycondensation reaction becomes long and it becomes difficult to obtain a copolymerized aromatic polyester having a high degree of polymerization. As the polycondensation catalyst, metal compounds such as Ti, Al, Sb and Ge known per se can be preferably used. Among them, the titanium compound added during the esterification reaction can be used continuously so that insoluble coarse particles due to catalyst residues can be used. It is preferable because the generation of foreign matter can be suppressed.

  By the way, as described above, from the viewpoint of further reducing surface defects, a polyester having a desired molecular weight obtained by polycondensation reaction is filtered with a second filter having a 95% filtration accuracy of 1.5 μm or less in a molten state. Is preferred. The polyester thus filtered, when dissolved with tetraethylene glycol, has an amount of insoluble coarse particles that cannot pass through a straight pore filter having a pore diameter of 8 μm, 40 / mg or less, and further 30 / mg or less, particularly a magnetic layer. It is preferable to filter with a second filter so that the surface on the side to be formed is 25 pieces / mg or less, and further 20 pieces / mg or less. Such a filter has a structure in which metal nonwoven fabric media is laminated, and the porosity of the laminated metal nonwoven fabric is usually in the range of 40 to 80%, and can withstand the filtration pressure while maintaining the filtration speed. Therefore, it is preferable.

  In addition, for the method of containing inert particles, select the one that has reduced the coarse particles as described above, make it an alkylene glycol slurry, further reduce the coarse particles with a filter, etc., and polymerize it. It is a surface defect due to agglomeration of inert particles that is added in the process to prepare a particle-containing master polyester having a particle content of 0.02 to 1.0% by weight, and the master polyester is diluted with a polyester not containing particles. It is preferable in reducing the amount.

  In addition, some surface defects are generated by a roll for conveying a film between a step of extruding a molten thermoplastic resin into a sheet shape and a step of winding it. From the viewpoint of reducing such surface defects, it is preferable to clean the surface of the roll interposed between the step of extruding the sheet and the step of winding it. At this time, the cleaning tool used for cleaning is preferably one that is less likely to generate foreign matter such as lint that itself causes surface defects, and one that can efficiently remove foreign matter adhering to the roll surface. preferable. From such a viewpoint, a fabric made of a synthetic fiber having a small fiber diameter is preferable, and a product name manufactured by Teijin Fibers Ltd., trade name: Achukuchi Fukkin is preferable.

  As described above, polyester has been described as an example, but it will be easily understood that other thermoplastic resins may be made in the same way. The thermoplastic resin thus obtained requires a stabilizer such as an ultraviolet absorber, an antioxidant, a plasticizer, a lubricant, a flame retardant, a release agent, and a nucleating agent as long as the effects of the present invention are not impaired. However, the polyester used on at least the surface on which the number of surface defects is to be measured is not limited to other thermoplastic resins, pigments, fillers or glass fibers, carbon fibers, layered silicas that are liable to form surface defects. It is preferable not to contain acid salts.

  The film produced by the production method of the present invention is preferably a biaxially oriented film when used as a data storage base film or the like. The biaxially oriented film can be produced by extruding the above-mentioned thermoplastic resin in a molten state and stretching in the biaxial direction, and a film forming method or the like can be employed. The filtration of the second filter described above is preferably used in the melt extrusion step during film formation because the effect of insoluble coarse particles generated later by reaggregation or the like can be reduced as the film is immediately before film formation. .

  For example, in the case of a biaxially oriented laminated film, a thermoplastic resin B containing inert particles in the extrusion die or before the die (generally, the former is called a multi-manifold method and the latter is called a feed block method) and necessary According to the above, the thermoplastic resin A containing inert particles is further filtered with a high-precision filter as described above, and then laminated and composited in a molten state to obtain a laminated structure with the above preferred thickness ratio. Then, after coextruding into a film form at a temperature of the melting point (Tm) to (Tm + 70) ° C. of the thermoplastic resin from the die, it is rapidly cooled and solidified with a cooling roll at 30 to 70 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is uniaxially (longitudinal or transverse) according to a conventional method at a temperature of (glass transition temperature (Tg) -10) to (Tg + 70) ° C. of 2.5 to 8. The film is stretched at a magnification of 0 times, preferably at a magnification of 3.0 to 7.5, and then perpendicular to the above stretching direction (if the first stage stretching is the longitudinal direction, the second stage stretching is the transverse direction). The film is stretched at a temperature of (Tg) to (Tg + 70) ° C. at a magnification of 2.5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times. Furthermore, you may extend | stretch again in the vertical direction and / or a horizontal direction as needed. That is, it is good to perform 2 steps | paragraphs, 3 steps | paragraphs, 4 steps | paragraphs, or multistage extending | stretching. The total draw ratio is usually 9 times or more, preferably 10 to 35 times, and more preferably 12 to 30 times.

  Further, the biaxially oriented film is imparted with excellent dimensional stability by heat-set crystallization at a temperature of (Tg + 70) to (Tm-10) ° C., for example, 180 to 250 ° C. in the case of a polyethylene terephthalate film. The At that time, the heat setting time is preferably 1 to 60 seconds.

  The thermoplastic resin film thus obtained is then wound around a cylindrical core or the like, and is cut into the desired product width or length as necessary. As described above, before use as a product, the number of surface defects measured by interference of light having a wavelength of 100 to 400 nm is measured. Sort as good. In addition, if necessary, the filter at each stage is changed or the filtration accuracy of the filter is adjusted so as to be equal to or less than the target reference value.

  Thus, according to the method for producing a film of the present invention, a film having a small number of surface defects measured by interference of light having a wavelength of 100 to 400 nm can be efficiently produced, and the storage capacity is, for example, 1 TB or more. Thus, it is possible to efficiently produce a film in which errors when used for a data storage base film are greatly reduced.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the characteristic of the polyester in this invention, the polyester film, and data storage was measured and evaluated by the following method.

(1) Intrinsic viscosity As described above, the intrinsic viscosity of the obtained thermoplastic resin is measured at o-chlorophenol at 35 ° C. If it is difficult to dissolve uniformly with o-chlorophenol, P-chloro It was determined by measuring at 35 ° C. using a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio).

(2) Content of insoluble coarse foreign matter (2-1) Coarse foreign matter amount 1
The amount of coarse foreign matter 1 is obtained by filtering the precursor before polymerization into a thermoplastic resin with a filter (first filter) during the transition to the second reaction after the completion of the first reaction in the thermoplastic resin polymerization step. Then, the filtered product was heated to 200 ° C. with tetraethylene glycol to be decomposed and dissolved to obtain a solution. Then, the solution is filtered through a straight membrane filter having a pore diameter of 8 μm, the number of insoluble coarse particles remaining on the filter is counted, and the weight of the thermoplastic resin obtained from the dissolved pre-polymerization precursor is calculated. As a reference, the content was calculated as number / mg.
In addition, since this value is calculated as the value of the resins 1 to 10 created in Reference Examples 1 to 10 described later, the values of the examples and comparative examples are based on the results of the resins 1 to 10, respectively. Based on the proportion of each resin used. Specifically, when the A layer of Example X is one using resins Y and Z at a ratio of 2: 1, the coarse foreign matter amount 1 is that of the resin Y (coarse foreign matter amount 1 × 2/3) and that of the resin Z. (The amount of coarse foreign matter 1 × 1/3).

(2-2) Coarse foreign matter amount 2
The amount of coarse foreign matter 2 is the resin 1-10 obtained in Reference Examples 1 to 10 described later at a desired ratio, dried, and then extruded from a die in a molten state. As described in Examples and Comparative Examples, filtration is performed with a filter (second filter). The polyester after passing through the second filter was decomposed and dissolved by heating to 200 ° C. with tetraethylene glycol to obtain a solution. Then, the solution is filtered through a straight membrane filter having a pore diameter of 8 μm, the number of insoluble coarse particles remaining on the filter is counted, and the content of each polyester layer is determined based on the weight of the dissolved polyester. Calculated as pieces / mg.

(3) Filtration accuracy of first and second filters Disperse glass beads of test powder (described in JIS-Z8901: 2006) in distilled water, measure the change in particle size distribution before and after filter filtration, and determine the 95% cut value. Hold it for filtration accuracy.

(4) Number of surface defects The film sample is superimposed on a quartz optical flat while being careful not to enter dust, and a mercury lamp having the shortest wavelength peak at 260 nm from the optical flat side is irradiated through a bandpass filter with a central wavelength of 260 nm. did. Then, the number of surface defects having a height of 65 nm or more observed from the interference fringes with a UV-CCD camera was confirmed. The measurement was performed at 10 locations with a measurement area of 25 cm ² , and the average value was converted to the number per 100 cm ² . At this time, the first decimal place was rounded off. In addition, the surface defect in this invention means a coarse protrusion, a film surface adhesion foreign material, and a film surface flaw.
Further, the same operation was repeated except that the bandpass filter was changed to one having a center wavelength of 200 nm, and the number of surface defects having a height of 50 nm or more at a wavelength of 200 nm was measured. Furthermore, the same operation was repeated except that the bandpass filter was changed to one having a center wavelength of 360 nm, and the number of surface defects having a height of 90 nm or more due to the wavelength of 360 nm was measured.
On the other hand, as a comparison, the number of surface defects having a height of 145 nm or more at a wavelength of 580 nm was similarly measured based on the method described in Patent Document 5 (Japanese Patent Laid-Open No. 2002-59520).

(5) Center plane average roughness (Ra)
Measured using a non-contact type three-dimensional surface roughness meter (manufactured by ZYGO: New View 5022) at a measurement magnification of 25 times and a measurement area of 283 μm × 213 μm (= 0.0603 mm ² ), and incorporated in the roughness meter The center surface average roughness (Ra) was determined by the surface analysis software Metro Pro.

(6) Average particle diameter of inert particles Measured using CP-50 Centrifuggle Particle Size Analyzer manufactured by Shimadzu Corp. (Centrifical Particle Size Analyzer). The particle size “equivalent sphere diameter” corresponding to 50 mass percent is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is used as the average particle size. (See Book “Particle Size Measurement Technology” published by Nikkan Kogyo Shimbun, 1975, pages 242-247).

(7) Glass transition point and melting point The glass transition point and the melting point were measured by DSC (TA Instruments Co., Ltd., trade name: Thermal list 2920) at a heating rate of 20 ° C / min.

(8) Young's modulus The obtained film was cut out with a sample width of 10 mm and a length of 15 cm, and a universal tensile testing device (manufactured by Toyo Baldwin, trade name: 100 mm between chucks, tensile speed of 10 mm / min, chart speed of 500 mm / min). Pull with Tensilon). The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve.

(9) Creation of data storage (magnetic tape)
A thermoplastic resin film slit to a width of 1 m is conveyed at a tension of 20 kg / m, and a magnetic coating and a nonmagnetic coating having the following composition are applied to the surface of the flat side of the film by an extrusion coater (the upper layer is a magnetic coating, The coating thickness was 0.1 μm, and the thickness of the nonmagnetic lower layer was 1.0 μm.), Magnetically oriented, and dried at a drying temperature of 100 ° C. Next, a back coat having the following composition was applied to the opposite surface so that the solid content had a thickness of 0.5 μm, and then a small test calender (steel / nylon roll, 5 steps) at a temperature of 85 ° C. and a linear pressure of 200 kg / cm. Calendar and roll up. The original tape was slit into a 1/2 inch width and incorporated into an LTO case to produce a data storage cartridge having a length of 850 m and a magnetic recording capacity of 0.8 TB.

(Composition of non-magnetic paint)
Nonmagnetic inorganic powder (α-iron oxide: average major axis length: 0.15 μm, average needle ratio: 7, BET specific surface area: 52 m ² / g): 100 parts by weight Vinyl acetate copolymer: 10 parts by weight-Nipporan 2304 (polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight-Coronate L (polyisocyanate made by Japanese polyurethane): 5 parts by weight-Lecithin: 1 part by weight-Methyl ethyl ketone: 75 parts by weight- Methyl isobutyl ketone: 75 parts by weight Toluene: 75 parts by weight Carbon black (average particle size: 20 nm): 2 parts by weight Lauric acid: 1.5 parts by weight (composition of magnetic paint)
Magnetic powder (Toda Kogyo Co., Ltd., trade name: NF30x): 100 parts by weight Eslek A (Sekisui Chemical vinyl chloride / vinyl acetate copolymer): 10 parts by weight Nipponran 2304 (Nippon Polyurethane Polyurethane Elastomer): 10 parts by weight Coronate L (polyisocyanate made from Japanese polyurethane): 5 parts by weight Lecithin: 1 part by weight Methyl ethyl ketone: 75 parts by weight Methyl isobutyl ketone: 75 parts by weight Toluene: 75 parts by weight Carbon black (average particle size : 20 nm): 2 parts by weight Lauric acid: 1.5 parts by weight (backcoat composition)
Carbon black (average particle size 20 nm): 95 parts by weight
Carbon black (average particle size 280 nm): 10 parts by weight
・ Α alumina: 0.1 parts by weight
・ Modified polyurethane: 20 parts by weight
・ Modified vinyl chloride copolymer: 30 parts by weight
・ Cyclohexanone: 200 parts by weight
・ Methyl ethyl ketone: 300 parts by weight
-Toluene: 100 parts by weight

(10) Dropout (DO)
The data storage cartridge created in (9) above was loaded into an IBM LTO4 drive (recording head equipped with an inductive head and playback head equipped with an MR head) to record a data signal of 14 GB and reproduce it. A signal having an amplitude (PP value) of 50% or less with respect to the average signal amplitude was detected as a missing pulse, and four or more consecutive missing pulses were detected as dropouts. In addition, dropout evaluates 1 volume of 850m, converts into the number per 1m, and determines by the following references | standards.
◎: Dropout less than 3 pieces / m ○: Dropout of 3 pieces / m or more, less than 9 pieces / m ×: Dropout of 9 pieces / m or more

[Reference Example 1] Preparation of Resin 1 100 parts and 70 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester and ethylene glycol, each of which was repeatedly purified by distillation, were prepared and provided with a stirrer, a rectifying column, and a cooler. The reaction vessel was charged and heated to 150 ° C. Thereafter, titanium trimellitic acid as Ti element amount was added so as to be 7 mmol% with respect to the number of moles of all dicarboxylic acid components, and the whole reaction vessel was heated with nitrogen under a pressure of 0.25 MPa, The internal temperature was raised to 240 ° C. As the reaction progressed, the internal temperature was increased to 250 ° C. with the pressure kept constant. Thereafter, the pressure in the reaction vessel is slowly returned to normal pressure, trimethyl phosphate is added in an amount of phosphorus element so as to be 12 mmol% with respect to the number of moles of the total dicarboxylic acid component, and excess ethylene glycol is driven out. The transesterification reaction was terminated.
The obtained reaction product was transferred to a polymerization reaction tank. At this time, it was filtered through a metal fiber filter with 95% filtration accuracy of 5 μm during transfer. In the polymerization reaction tank, the polycondensation reaction is carried out while slowly raising the temperature from 250 ° C. while reducing the pressure, and finally the polycondensation is carried out at 290 ° C. and 30 Pa until a predetermined polymerization degree is obtained. Thus, polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.6 dl / g was obtained.

[Reference Example 2] Preparation of Resin 2 100 parts and 70 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester and ethylene glycol, each of which was repeatedly purified by distillation, were prepared and provided with a stirrer, a rectifying column, and a cooler. The reaction vessel was charged and heated to 150 ° C. Thereafter, titanium trimellitic acid as Ti element amount was added so as to be 3 mmol% with respect to the number of moles of all dicarboxylic acid components, and the whole reaction vessel was heated with nitrogen at a pressure of 0.25 MPa, The internal temperature was raised to 240 ° C. As the reaction progressed, the internal temperature was increased to 250 ° C. with the pressure kept constant. Thereafter, the pressure in the reaction vessel is slowly returned to normal pressure, trimethyl phosphate is added in an amount of phosphorus element so as to be 7 mmol% with respect to the number of moles of all dicarboxylic acid components, and excess ethylene glycol is expelled, The transesterification reaction was terminated.
The obtained reaction product was transferred to a polymerization reaction tank. At this time, it was filtered through a metal fiber filter with 95% filtration accuracy of 5 μm during transfer. In the polymerization reaction tank, the polycondensation reaction is carried out while slowly raising the temperature from 250 ° C. while reducing the pressure, and finally the polycondensation is carried out at 290 ° C. and 30 Pa until a predetermined polymerization degree is obtained. Thus, polyethylene terephthalate having an intrinsic viscosity of 0.6 dl / g was obtained.

[Reference Example 3] Preparation of Resin 3 True spherical silica particles prepared by an alkoxide method having an average particle diameter of 0.1 μm and a relative standard deviation of 0.13 were added to ethylene glycol so as to be 10% by weight, After heating at 100 ° C. for 20 minutes, the mixture was circulated through a metal fiber filter having a 95% filtration accuracy of 5 μm to prepare an ethylene glycol slurry having a true spherical silica particle content of 10% by weight. Reference Example 1 was made except that this ethylene glycol slurry was added so that the content of the spherical silica particles was 0.5% by weight with respect to the weight of the polyester obtained at the stage of the transesterification reaction. The same operation was repeated to prepare Resin 3.

[Reference Example 4] Preparation of Resin 4 True spherical silica particles prepared by an alkoxide method having an average particle size of 0.1 μm and a relative standard deviation of 0.13 were added to ethylene glycol so as to be 10% by weight, After heating at 100 ° C. for 20 minutes, the mixture was circulated through a metal fiber filter having a 95% filtration accuracy of 5 μm to prepare an ethylene glycol slurry having a true spherical silica particle content of 10% by weight. Reference Example 2 was added except that this ethylene glycol slurry was added so that the content of the spherical silica particles was 0.5% by weight based on the weight of the polyester obtained at the stage of the transesterification reaction. The same operation was repeated to prepare Resin 4.

[Reference Example 5]
Resin 5 was prepared by repeating the same operation as in Reference Example 3 except that the true spherical silica particles were changed to true spherical silica particles having an average particle size of 0.3 μm and a relative standard deviation of 0.12.

[Reference Example 6]
Resin 6 was prepared by repeating the same operation as in Reference Example 4 except that the true spherical silica particles were changed to true spherical silica particles having an average particle size of 0.3 μm and a relative standard deviation of 0.12.

[Reference Example 7]
Resin 7 was prepared in the same manner as in Reference Example 3 except that silicone particles having an average particle size of 0.1 μm and a relative standard deviation of 0.19 were used instead of the spherical silica particles.

[Reference Example 8]
Resin 8 was produced in the same manner as in Reference Example 1 except that the metal fiber filter was changed to a filter with 95% filtration accuracy of 10 μm.

[Example 1]
Resins 1 and 3 were prepared as the polymer for the A layer so that the content of the true spherical silica particles having an average particle size of 0.1 μm was 0.1% by weight. 3 and 5 are prepared so that the content of true spherical silica particles having an average particle diameter of 0.1 μm is 0.1% by weight and the content of true spherical silica particles having an average particle diameter of 0.3 μm is 0.2% by weight. Each was dried at 170 ° C. for 6 hours. The chips thus dried are supplied to two extruder hoppers, melted at a melting temperature of 310 ° C., and the layer B is laminated on one side of the layer A using a multi-manifold coextrusion die, and the layers are not stretched. A film was obtained. The polymer for the A layer and the polymer for the B layer were each filtered through a filter (second filter) having a 95% filtration accuracy of 1 μm before being fed to the die. Further, the amount of coarse foreign matter 1 in the A layer resin is 31 / mg and the amount of coarse foreign matter 2 is 9 / mg, and the amount of coarse foreign matter 1 in the B layer resin is 108 pieces / mg and the amount of coarse foreign matter 2 is 17 / Mg.
The laminated unstretched film thus obtained was preheated to 120 ° C. on a metal roll cleaned with a fabric (manufactured by Teijin Fibers Ltd., trade name: Achi Kocchi Fukin), and further similarly cleaned with the fabric. The film was heated to 130 ° C. between high-speed rolls and stretched 4.8 times, and then rapidly cooled to obtain a longitudinally stretched film.
Then, it supplied to the stenter and extended | stretched 5.1 times in the horizontal direction at 150 degreeC. The obtained biaxially stretched film was stretched by 10% in the transverse direction while being heat-fixed with hot air at 200 ° C. for 3 seconds, and the thickness was 4.7 μm (A layer thickness 1.7 μm, B layer thickness 3.0 μm). A laminated biaxially oriented polyester film was produced for 1000 hours. In addition, since the increase in the number of surface defects was confirmed, the second filter was replaced in the middle of 600 hours, and the winding process preheating roll and the drawing roll were cleaned with the fabric. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Comparative Example 1]
The same operation as in Example 1 was repeated except that the second filter was not changed in the middle and the production was continued for 1000 hours. Table 1 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 2]
Resins 2 and 4 are prepared as the polymer for the A layer so that the content of the true spherical silica particles having an average particle size of 0.1 μm is 0.07% by weight, and the resins 2, 4 are used as the polymer for the B layer. 6 are prepared so that the content of true spherical silica particles having an average particle size of 0.1 μm is 0.1% by weight and the content of true spherical silica particles having an average particle size of 0.3 μm is 0.15% by weight. Each was dried at 170 ° C. for 6 hours. The chips thus dried are supplied to two extruder hoppers, melted at a melting temperature of 310 ° C., and the layer B is laminated on one side of the layer A using a multi-manifold coextrusion die, and the layers are not stretched. A film was obtained. The polymer for the A layer and the polymer for the B layer were each filtered through a filter (second filter) having a 95% filtration accuracy of 1 μm before being fed to the die. Further, the amount of coarse foreign matter 1 in the A layer resin is 30 pieces / mg and the amount of coarse foreign matter 2 is 10 pieces / mg, and the amount of coarse foreign matter 1 in the layer B resin is 106 pieces / mg and the amount of coarse foreign matter 2 is 18 pieces. / Mg.
The laminated unstretched film thus obtained was preheated to 100 ° C. on a metal roll cleaned with the fabric, and the film was heated to 110 ° C. between low-speed and high-speed rolls cleaned with the fabric as well. The film was stretched 3.5 times and then rapidly cooled to obtain a longitudinally stretched film.
Then, it supplied to the stenter and extended | stretched 4.6 times in the horizontal direction at 105 degreeC. The obtained biaxially stretched film was stretched 5% in the transverse direction while being heat-fixed with hot air at 210 ° C. for 3 seconds, and the thickness was 4.7 μm (A layer thickness 4.2 μm, B layer thickness 0.5 μm). A laminated biaxially oriented polyester film was produced for 1000 hours. In addition, since the increase in the number of surface defects was confirmed, the second filter was replaced in the middle of 600 hours, and the winding process preheating roll and the drawing roll were cleaned with the fabric. Table 2 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Comparative Example 2]
The same operation as in Example 1 was repeated except that the second filter was not changed in the middle and the production was continued for 1000 hours. Table 2 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 3]
Resins 3 and 8 are prepared as the polymer for the A layer so that the content of true spherical silica particles having an average particle size of 0.1 μm is 0.1% by weight. Also, as the polymer for the B layer, the resin 3, 5 and 7 are prepared so that the content of true spherical silica particles having an average particle size of 0.1 μm is 0.1% by weight and the content of true spherical silica particles having an average particle size of 0.3 μm is 0.2% by weight. A laminated biaxially oriented polyester film was produced for 1000 hours by repeating the same operation as in Example 1 except that the above procedure was repeated. It should be noted that the polymer for the A layer and the polymer for the B layer were each filtered through a filter (second filter) having a 95% filtration accuracy of 1 μm before being fed to the die. The coarse foreign matter amount 1 of the A layer resin is 267 pieces / mg and the coarse foreign matter amount 2 is 23 pieces / mg, and the coarse foreign matter amount 1 of the B layer resin is 487 pieces / mg and the coarse foreign matter amount 2 is 26 pieces. / Mg. Moreover, since the increase in the number of surface defects was confirmed, the second filter was replaced in the middle of 600 hours, and the winding process preheating roll and the drawing roll were cleaned with the fabric. Table 3 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Comparative Example 3]
The same operation as in Example 3 was repeated except that the production was continuously performed for 1000 hours without replacing the second filter. Table 3 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 4]
Resin 2 is prepared as the polymer for the A layer, and as the polymer for the B layer, the resins 2, 4, 6 are 0.1% by weight of the spherical silica particles having an average particle diameter of 0.1 μm, the average particle Except for preparing the content of true spherical silica particles having a diameter of 0.3 μm to be 0.15 wt%, and changing the thickness of the A layer to 1.7 μm and the thickness of the B layer to 3.0 μm, The same operation as in Example 2 was repeated to produce a laminated biaxially oriented polyester film for 1000 hours. The polymer for the A layer and the polymer for the B layer were each filtered through a filter (second filter) having a 95% filtration accuracy of 1 μm before being fed to the die. In addition, the coarse particle amount 1 of the A layer resin is 11 particles / mg and the coarse particle amount 2 is 4 particles / mg, and the coarse particle amount 1 of the B layer resin is 106 particles / mg and the coarse particle amount 2 is 18 particles. / Mg. Moreover, since the increase in the number of surface defects was confirmed, the second filter was replaced in the middle of 600 hours, and the winding process preheating roll and the drawing roll were cleaned with the fabric. Table 4 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Comparative Example 4]
The same operation as in Example 4 was repeated except that the production was continuously performed for 1000 hours without replacing the second filter. Table 4 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Example 5]
Resins 1 and 3 were prepared as the polymer for the A layer so that the content of the true spherical silica particles having an average particle size of 0.1 μm was 0.1% by weight. 3 and 5 are prepared so that the content of true spherical silica particles having an average particle diameter of 0.1 μm is 0.1% by weight and the content of true spherical silica particles having an average particle diameter of 0.3 μm is 0.2% by weight. Each was dried at 170 ° C. for 6 hours. The chips thus dried are supplied to two extruder hoppers, melted at a melting temperature of 310 ° C., and the layer B is laminated on one side of the layer A using a multi-manifold coextrusion die, and the layers are not stretched. A film was obtained. The polymer for the A layer and the polymer for the B layer were each filtered through a filter (second filter) having a 95% filtration accuracy of 1 μm before being fed to the die. Further, the amount of coarse foreign matter 1 in the A layer resin is 31 / mg and the amount of coarse foreign matter 2 is 9 / mg, and the amount of coarse foreign matter 1 in the B layer resin is 108 pieces / mg and the amount of coarse foreign matter 2 is 17 / Mg.
The laminated unstretched film thus obtained was preheated to 120 ° C. on a metal roll cleaned with the cloth, and the film was heated to 130 ° C. between low-speed and high-speed rolls similarly cleaned with the cloth. The film was stretched 4.8 times and then rapidly cooled to obtain a longitudinally stretched film.
Then, it supplied to the stenter and extended | stretched 5.1 times in the horizontal direction at 150 degreeC. The obtained biaxially stretched film was stretched by 10% in the transverse direction while being heat-fixed with hot air at 200 ° C. for 3 seconds, and the thickness was 4.7 μm (A layer thickness 1.7 μm, B layer thickness 3.0 μm). A laminated biaxially oriented polyester film was produced for 1000 hours. In addition, since the increase in the number of surface defects was confirmed, the second filter was replaced in the middle of 600 hours, and the winding process preheating roll and the drawing roll were cleaned with the fabric. Table 5 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

[Comparative Example 5]
The same operation as in Example 5 was repeated except that the production was continuously performed for 1000 hours without changing the second filter in the middle. Table 5 shows the properties of the obtained laminated biaxially oriented polyester film and the magnetic recording tape.

  The present invention can be suitably used as a method for producing a thermoplastic resin film, and can be particularly suitably used for a method for producing a base film of a magnetic recording medium.

Claims (6)

A method for producing a film comprising a melt extrusion process for extruding a molten thermoplastic resin into a sheet, a process for winding it, and a process for sorting the wound film into a non-defective product and a defective product to make the good product as a product And by sticking at least one surface of the wound film to a transparent substrate and irradiating light with a wavelength of 100 to 400 nm from the transparent substrate side , the boundary between the transparent substrate and the void and the void A film characterized by measuring the number of coarse surface defects measured by interference fringes of reflected light reflected from the boundary of the film surface, and making a film having a measured number of coarse surface defects below a reference value as a non-defective product Manufacturing method.   The method for producing a film according to claim 1, wherein the surface roughness of at least one of the films is in the range of 1 to 10 nm.   The method for producing a film according to claim 1, wherein, in the melt extrusion step, the molten thermoplastic resin is filtered by a filter, and the filter is replaced based on a measured value of the number of surface defects.   The method for producing a film according to claim 1, wherein, in the step of extruding the sheet into a sheet and then winding it, the roll used in the step is cleaned based on the measured value of the number of surface defects.   The method for producing a film according to claim 1, wherein the film is a polyester film.   The method for producing a film according to claim 1, wherein the film is used as a base film of a high-density magnetic recording medium.