JP2012031427A - Polyester film roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film roll for a diffusion plate in which there are few troubles at the surface of the film by the generation of static electricity when coating a light diffusing layer, and there is little generating of a running trouble when coating by a coater.SOLUTION: The polyester film roll is such that a biaxially oriented polyester film which comprises performing tentering treatment or relaxation treatment in a 100-160°C temperature region after heat setting, has a coating layer containing a cationic polymer on at least one side, and in which the surface resistivity of the coating layer is at most 1×10Ω is wound by the width of at least 800 mm, and is characterized in that when the tension of 0.39 MPa is equally applied at the interval of 1.5 m in the longitudinal direction of the film, the amount of slack generated on the film is at most 12 mm.

Description

  The present invention relates to a polyester film roll suitable for a diffusion plate, and more specifically, relates to a polyester film roll that is less likely to generate static electricity in the film and has excellent flatness and excellent processing characteristics. is there.

  In recent years, liquid crystal displays have been widely used as various mobile communication terminals such as mobile phones, personal computer monitors, liquid crystal televisions, and other display devices. In particular, liquid crystal displays as flat-screen televisions have been developed to large screens of 37 inches or more, and the demand that can be said to be explosive is increasing.

  The liquid crystal display does not display an image when the liquid crystal itself emits light, but displays an image using light such as a plurality of cold cathode tubes or LEDs (light emitting diodes) as a backlight. The light from the backlight is converted into an image by controlling the transmission and non-transmission of light with a liquid crystal panel. If the light used for the backlight is white light, color display can be performed by passing the light through each of the pixels divided into the three primary colors RGB of the color filter. A field sequential color display system has been developed that performs color display by combining a liquid crystal panel with an LED backlight configured to emit light sequentially.

  By the way, in the case of the direct type backlight, the cold cathode tube is a linear light source, and the LED is a point light source. Therefore, it is necessary to display the image by making light emitted from these light sources as close as possible to a uniform surface light source. There is. It is the diffusion plate that plays this role, and the light that has passed through the diffusion plate is literally diffused and approaches the surface light source. If a plurality of these are used, the light is more diffused and closer to the surface light source.

  The diffusion plate described above is a method in which the surface of the transparent resin film is directly physically uneven (Patent Document 1), and a method in which a light diffusion layer made of a transparent resin containing fine particles is coated on the transparent resin film (Patent Document 1). 2, 3), a method in which fine particles are melt-mixed in a transparent resin and obtained by extrusion molding (Patent Document 4) is known, but the most widely used at present is a light diffusion layer. It is a method of coating.

  By the way, as the demand for liquid crystal televisions increases, the selling price tends to decrease. For this reason, there is an urgent need to reduce production costs, and the basic performance is required to be maintained. This applies not only to the display assembly process, but also to various parts and components. For example, it can reduce the cost while maintaining or improving the performance of key parts such as panels that display images. Therefore, improving productivity is a major issue.

  As described above, in order to provide a light diffusion layer on the surface of a polyester film by coating, a method of applying a coating solution in which particles such as beads and a binder resin are dispersed or dissolved in an organic solvent is often used. At this time, if static electricity is generated on the polyester film, the static electricity is generally removed so as not to cause ignition due to electrostatic discharge. However, the static electricity on the film surface cannot be completely removed no matter how much charge removal treatment is performed, and coating defects such as coating removal and uneven coating occur in the same pattern as the static electricity distribution pattern remaining on the polyester film surface, resulting in poor quality. Is a problem. In addition, if there is a large amount of tarmi at the edge or center of the polyester film that is the base material, troubles such as wrinkling of the film will occur when the film is run to be coated with a coater. There is a problem that becomes easier. This problem is increasing in importance as the size of the diffuser plate is increased with the recent increase in the screen size of the display, and the polyester film base for this purpose is also widened. Under such circumstances, in order to increase the productivity of the diffusion plate, improvement of the polyester film serving as a base material is required.

JP-A-4-275501 JP-A-6-59108 Japanese Patent Laid-Open No. 10-142406 JP-A-6-123802 JP 2004-35761 A JP 2005-105255 A JP 2002-350617 A

  The present invention has been made in view of the above circumstances, and its purpose is that when coating the light diffusing layer, there are few troubles due to the generation of static electricity on the film surface, and moreover, traveling troubles occur when coating with a coater. An object of the present invention is to provide a polyester film roll suitable for a diffusion plate that is less likely to occur.

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

That is, the gist of the present invention is that after heat setting, a tentering treatment or a relaxation treatment is performed in a temperature range of 100 to 160 ° C., and has a coating layer containing a cationic polymer on at least one surface. A film roll in which a biaxially oriented polyester film having a resistance value of 1 × 10 ¹³ Ω or less is wound with a width of 800 mm or more, and a tension of 0.39 MPa is applied at an interval of 1.5 m in the longitudinal direction of the film. When added evenly, the amount of tarmi generated in the film is 12 mm or less.

  The polyester film roll of the present invention has less occurrence of coating defects such as coating leakage and coating unevenness due to static electricity when the light diffusion layer is applied, and the film has good flatness and the amount of talmi generated in the film. Since there are few, it is hard to generate the driving trouble with a coater. Furthermore, since it corresponds to the demand for widening as a polyester film for a diffusion plate, it contributes to the productivity improvement of the diffusion plate.

<Base film>
The biaxially oriented polyester film in the present invention is composed of aromatic polyester such as polyethylene terephthalate and polyethylene-2,6-naphthalate, or a copolymer mainly composed of these resin components as its constituent components. Is mentioned.

  When the polyester is a copolyester, it is preferably a copolymer having a third component content of 10 mol% or less. As the dicarboxylic acid component of the copolymer polyester, one or more selected from isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid and the like Is mentioned. Examples of the glycol component include one or more selected from ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, ethylene oxide adduct of bisphenol A, and the like. In addition, when the usage-amount of such a copolymerization component exceeds 10 mol%, the fall of the heat resistance of a film, mechanical strength, solvent resistance, etc. will become remarkable.

  Among the above polyesters, a film using polyethylene terephthalate as a constituent component or a film using the copolyester is preferable in terms of a balance between characteristics as a base film and cost.

  The above polyester is obtained by a conventionally known method, for example, by directly reacting a dicarboxylic acid and a diol to obtain a low polymerization degree polyester, or by reacting a lower alkyl ester of a dicarboxylic acid and a diol with a conventionally known transesterification catalyst. Then, it can obtain by the method of superposing | polymerizing in presence of a polymerization catalyst. As the polymerization catalyst, a known catalyst such as an antimony compound, a germanium compound, or a titanium compound may be used, but a method of reducing the dullness of the film by setting the amount of the antimony compound to zero or 100 ppm or less as antimony is also preferably used. be able to. In addition, these polymerizations can be carried out in a molten state to a predetermined degree of polymerization, or solid phase polymerization can be used in combination. In particular, in order to reduce the amount of oligomers contained in the polyester, it is preferable to use solid phase polymerization in combination.

  The intrinsic viscosity of the polyester used for the biaxially oriented polyester film is preferably 0.40 to 0.90 dl / g, more preferably 0.45 to 0.85 dl / g. If the intrinsic viscosity is too low, the mechanical strength of the film tends to decrease. Moreover, when intrinsic viscosity is too high, the load in the melt extrusion process at the time of film formation will be large, and there exists a tendency for productivity to fall.

  The biaxially oriented polyester film in the present invention may have a laminated film structure in which three or more layers of polyester are laminated by a coextrusion method. At this time, the film is composed of two outermost layers and an intermediate layer which may itself be a laminated structure. The thickness of the two outermost layers is usually 2 μm or more, preferably 5 μm or more, On the other hand, the total thickness of the film is usually 1/4 or less, preferably 1/10 or less.

  In the biaxially oriented polyester film of the present invention, inorganic fine particles or organic fine particles can be added to the film in order to ensure slipperiness and prevent the generation of scratches in the process. The fine particles added to the polyester film are not particularly limited. For example, inorganic fine particles such as silicon oxide, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium phosphate, kaolin, and alumina, or a cross-linked acrylic resin And crosslinked polymer fine particles such as a crosslinked polystyrene resin. Among these, in order to obtain a high degree of transparency, it is preferable to use amorphous silica particles having a refractive index relatively close to that of polyester and less void formation in the biaxially oriented polyester film. These fine particles having an average particle size in the range of usually 0.02 to 5 μm can be used alone or in combination of two or more. The addition amount is usually in the range of 0.0005 to 1.0% by weight.

  These fine particles are added to the entire film when the polyester film has a single layer structure, but when the polyester film has a laminated structure of three or more layers, by adding the fine particles only to both surface layers, It is preferable because it is easy to ensure slipperiness while maintaining the transparency of the polyester film. In particular, when the film thickness is thick (for example, 100 μm or more), it is effective to add fine particles only to both surface layers.

  In addition, the oligomers contained in the polyester film are deposited on the surface of the film due to heat history during film processing, etc., so that it becomes a foreign object and deteriorates the transparency of the film. It is possible to use polyester that has been removed. As polyester which reduced the amount of oligomers, the polyester polymerized by combining the solid phase polymerization mentioned above can be used. When the film has a single layer structure, it can be used for the entire film, and when the film has a multilayer structure, a low oligomerized polyester can be used only for both surface layers.

  Furthermore, in the biaxially oriented polyester film in the present invention, additives such as conventionally known antioxidants, heat stabilizers, lubricants, fluorescent brighteners, dyes, pigments, etc., if necessary, in addition to the above fine particles Can be added. These additives are preferable because the polyester film has a laminated structure of three or more layers, and is added to the intermediate layer in order to prevent the additive from being deposited on the film surface.

Although the thickness of the biaxially oriented polyester film in the present invention is not particularly limited, it is preferably in the range of usually 50 to 300 μm, particularly 75 to 250 μm for use as a diffusion plate film.
<Coating layer>
The biaxially oriented polyester film in the present invention has a coating layer containing a cationic polymer on at least one surface, and the surface resistivity of the coating layer is required to be 1 × 10 ¹³ Ω or less.

  In the present invention, a cationic polymer is used as an antistatic agent used in the coating layer. A low molecular weight antistatic agent is not preferred because the antistatic agent tends to transfer onto the overlapping surface when the film is wound. Among polymer antistatic agents, nonionic polymers are generally not preferred because they often lack antistatic performance. An anionic polymer antistatic agent is strongly acidic, for example, polystyrene sulfonic acid, and there are difficulties in handling, and in the case of a neutralized salt thereof, a coating film is applied at the time of application / stretching by the in-line coating method described later. Is not preferred because it tends to whiten. On the other hand, the cationic polymer is preferably used in the present invention because it is relatively excellent in antistatic performance and is excellent in terms of handleability and little whitening during stretching.

  The cationic polymer in the coating layer used in the present invention is preferably a polymer containing a unit containing a quaternized nitrogen as a repeating unit, and in particular, a main chain represented by the following formula (1) or (2) A cationic polymer containing a unit having a pyrrolidinium ring as a main repeating unit is preferable in that excellent antistatic performance can be obtained. In addition, even if the blending amount of the cationic polymer in the coating layer is reduced, the decrease in the antistatic performance is small. Instead, the blending amount of the component having adhesiveness can be increased and the adhesiveness of the coating layer can be improved. This is advantageous.

In the structure of the above formula (1) or (2), R ¹ and R ² are usually an alkyl group having 1 to 4 carbon atoms or hydrogen, and these may be the same group or different. In addition, the alkyl group of R ¹ and R ² may be substituted with a hydroxyl group, an amide group, an amino group, or an ether group. Further, R ¹ and R ² may be chemically bonded to have a ring structure. The (1) or (2) the X ^- is a halogen ion, a nitrate ion, methanesulfonate ion, ethanesulfonate ion, monomethyl sulfate ion, monoethyl sulfate ion, trifluoroacetate ion, trichloroacetate ion.

Among the above-mentioned cationic polymers containing a unit having a pyrrolidinium ring in the main chain as a main repeating unit, particularly when the structure of formula (1) and X ⁻ is a chlorine ion, the antistatic performance is excellent. In addition, the humidity dependency of the antistatic performance is small, which is preferable in that the decrease in the antistatic performance is reduced even under a low humidity. In applications where halogen ions cannot be used in the coating layer, antistatic performance close to that of chlorine ions can be obtained by using methanesulfonic acid or monomethyl sulfate ions instead of chlorine ions.

  The polymer having the unit of the formula (1) as a repeating unit is polymerized by using the diallylammonium salt represented by the following formula (3) as a monomer and ring-closing by radical polymerization in a medium mainly containing water. It is obtained by. The polymer having the unit of the formula (2) as a repeating unit can be obtained by cyclopolymerizing the monomer of the formula (3) in a system using sulfur dioxide as a medium.

  In addition, when the polymer having the unit represented by the formula (1) or (2) as a repeating unit is a homopolymer composed of a single unit, better antistatic performance can be obtained. As will be described later, in order to improve the transparency of the coating layer when the polyester film is further stretched after the coating solution containing the cationic polymer is applied to the polyester film, it is expressed by the formula (1) or (2). 0.1 to 50 mol% of the unit to be prepared may be replaced with other copolymerizable components.

  As the monomer component used as the copolymer component, one or more compounds having a carbon-carbon unsaturated bond copolymerizable with the diallylammonium salt of the formula (3) can be selected.

  These are specifically acrylic acid and its salts, methacrylic acid and its salts, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) Acrylamide, N-methylol (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, maleic acid and its salt or maleic anhydride, fumaric acid and its salt or fumaric anhydride, monoallylamine And quaternized products thereof, acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylidene chloride, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, dihydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, (meth) A Liloyloxyethyldialkylamine and its quaternary product, (meth) acryloyloxypropyldialkylamine and its quaternary product, (meth) acryloylaminoethyldialkylamine and its quaternary product, (meth) acryloylaminopropyldialkylamine and its quaternary product A quaternized product can be exemplified, but is not limited thereto.

  The cationic polymer contained in the coating layer is, for example, represented by the formula (4) or (5) in addition to the cationic polymer containing a pyrrolidinium ring as a repeating unit in the main chain represented by the formula (1) or (2). A cationic polymer having a repeating unit as a repeating unit may be used.

In the structure of the above formula (4) or (5), R ³ and R ⁸ are each independently hydrogen or a methyl group, and R ⁴ and R ⁹ are each independently independently usually having 2 carbon atoms. ˜6 alkyl groups. R ⁵ , R ⁶ , R ⁷ , R ¹⁰ , R ¹¹ and R ¹² are a methyl group, a hydroxyethyl group or hydrogen, and these may be the same group or different. Further, X ⁻ in the formula (4) or (5) is a halogen ion, nitrate ion, methanesulfonate ion, ethanesulfonate ion, monomethyl sulfate ion, monoethyl sulfate ion, trifluoroacetate ion, or trichloroacetate ion.

  The average molecular weight (number average molecular weight) of the cationic polymer in the coating layer used in the present invention is usually in the range of 1,000 to 500,000, more preferably 5,000 to 100,000. If the average molecular weight is less than 1000, it may cause the cationic polymer to transfer or block on the overlapping surface when the film is wound, and conversely if the average molecular weight exceeds 500,000, the coating solution containing this It becomes difficult to uniformly apply to the film surface.

  In the biaxially oriented polyester film of the present invention, the binder polymer is used in the coating layer in order to improve the adhesion with the light diffusion layer provided on the coating layer containing the cationic polymer and the adhesion with the polyester film as the substrate. It is preferable to add to. Examples of the binder polymer include polyester, polyacrylate, and polyurethane. These polymers can be rendered water-soluble or water-dispersed by copolymerizing a nonionic, cationic, or amphoteric hydrophilic component as one component of the monomer. In addition, nonionic, cationic, or amphoteric surfactants are used to disperse in water by so-called forced emulsification, or emulsion polymerization is performed using nonionic, cationic, or amphoteric surfactants. It can also be made into a dispersion. Furthermore, these polymers can also be used as copolymers, and may be any of random copolymers, block copolymers, and graft copolymers, or may be a conjugate with a different polymer. Examples include, but are not limited to, urethane-graft-polyacrylate or polyester-graft-polyacrylate obtained by emulsion polymerization of an acrylic monomer in the presence of an aqueous solution or dispersion of polyurethane or polyester. Absent.

  In the biaxially oriented polyester film of the present invention, a crosslinking agent can be added to the coating layer containing the cationic polymer for the purpose of improving the heat-resistant adhesiveness, solvent resistance, blocking resistance and the like of the coating layer. Examples of the crosslinking agent include methylolated or alkoxymethylolated melamine compounds, urea compounds, acrylamide compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, oxazoline compounds, silane coupling agent compounds, and the like. It is preferable to contain at least one selected.

  In the biaxially oriented polyester film of the present invention, inorganic or organic fine particles can be added to a coating layer containing a cationic polymer for the purpose of imparting slipperiness on the surface of the coating layer and improving blocking resistance. The fine particles include at least selected from fine particles such as silicon oxide, alumina, cross-linked acrylic resin, cross-linked polystyrene resin, and conductive fine particles such as tin oxide, indium-tin composite oxide fine particles, and antimony-tin composite oxide fine particles. It is preferable to contain 1 type.

  In the biaxially oriented polyester film of the present invention, a surfactant can be added to the coating layer containing a cationic polymer. As this surfactant, a nonionic surfactant such as an alkylene oxide addition polymer of acetyl glycol can be preferably used for the purpose of improving the wettability of the coating solution. Further, for the purpose of maintaining the transparency of the coating layer in the step of stretching the coating layer together with the film, a polyalkylene oxide adduct of glycerin or a polyalkylene oxide adduct of polyglycerin can be preferably used.

  In the biaxially oriented polyester film of the present invention, the composition constituting the coating layer containing the cationic polymer, that is, the amount ratio of the cationic polymer, the binder, the crosslinking agent, the fine particles, and the surfactant has an optimum value depending on the selected compound. Therefore, although not particularly specified, in order to impart antistatic performance to the surface of the coating layer, the content of the cationic polymer is usually 5% or more, preferably 10 to 80%.

The surface specific resistance value of the coating layer containing the cationic polymer described above needs to be 1 × 10 ¹³ Ω or less, preferably 1 × 10 ¹¹ Ω or less, more preferably 1 × 10 ¹⁰ Ω or less. The lower limit is not particularly limited, but is usually 1 × 10 ⁸ Ω. If the surface resistivity exceeds 1 × 10 ¹³ Ω, static electricity generated on the film surface cannot be effectively removed even if normal charge removal is performed. For example, a light diffusion layer is applied using an organic solvent. In this case, coating unevenness and coating leakage are likely to occur in the same pattern as the static electricity distribution pattern (called a charging pattern or static mark) remaining on the film, which is not preferable.

  The coating layer containing the cationic polymer described above is coated on the polyester film as a coating solution mainly using water as a medium. For the purpose of improving the stability of the coating solution or improving the coating properties and coating film characteristics. In addition to water, it is usually possible to add an organic solvent in an amount of 10% by weight or less. Examples of the organic solvent include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin, ethyl cellosolve, t-butyl cellosolve, ethers such as propylene glycol monomethyl ether and tetrahydrofuran, ketones such as acetone and methyl ethyl ketone, Examples thereof include amines such as dimethylethanolamine and trimethanolamine, and amides such as N-methylpyrrolidone. These can be used alone or in combination.

  In the present invention, the above aqueous coating solution is applied to at least one side of a polyester film. This film is a polyester film before crystal orientation is completed, and after application, is further stretched in at least one direction and then heat-set. It is preferred that Specifically, after applying an aqueous coating solution to an unstretched film, when the film is stretched simultaneously or sequentially in the machine direction and the transverse direction, and then heat-set, after applying the film uniaxially stretched in the machine direction or the transverse direction When stretched in a direction perpendicular to the previous stretching and then heat-set, after being applied to a film biaxially stretched in the vertical and horizontal directions, then stretched again in the vertical or horizontal or both directions and then heat-set Can be illustrated. By using such a so-called in-line coating method, the coating layer is usually heat-set at a high temperature of 200 ° C. or higher, so that the adhesion between the coating layer and the polyester film is improved.

  Any known method can be applied as a method of applying the coating solution to the polyester film as the substrate. Specifically, roll coating method, gravure coating method, micro gravure coating method, reverse coating method, bar coating method, roll brush method, spray coating method, air knife coating method, impregnation method, curtain coating method, die coating method, etc. It can be applied alone or in combination.

  The thickness of the coating layer containing the cationic polymer of the biaxially oriented polyester film in the present invention is preferably 0.01 to 0.5 μm, more preferably 0.02 to 0.3 μm, as a final dry thickness. When the thickness of the coating layer is less than 0.01 μm, antistatic performance and adhesiveness are insufficient, and when it exceeds 0.5 μm, blocking tends to occur. Moreover, the coating layer containing a cationic polymer may be coated only on one side of the film, or may be coated on both sides. Furthermore, in the case of coating only on one side of the film, it is possible to simultaneously coat another coating layer different from the coating layer described above.

Since the biaxially oriented polyester film in the present invention is used for a diffusion plate, the film haze including the coating layer is preferably 5.0% or less, and more preferably 3.0% or less.
<Film roll>
The polyester film roll for a diffusion plate of the present invention is a film roll wound up with a width of 800 mm or more, and when a tension of 0.39 MPa is evenly applied at an interval of 1.5 m in the longitudinal direction of the film, It is necessary that the amount of tarmi generated in the film is 12 mm or less at maximum. This amount of talmi is preferably 8 mm or less, more preferably 6 mm or less. When the amount of the tarmi of the film exceeds 12 mm, when the film roll is set on the coater and the light diffusing layer is applied, a running trouble such as a wrinkle is likely to occur in the film, which is not preferable.

  The amount of tarmi of the film in the present invention was measured by the following method. That is, the film is unwound from the film roll, and spanned over two rolls installed in parallel and horizontally with an interval of 1.5 m so that the longitudinal direction of the film straddles. When a tension of 0.39 MPa (a tension at which the film does not stretch and deform) is evenly applied to the film between the two rolls, the film between the rolls is not always stretched uniformly as a whole. Either one or both ends, or the central portion may sag and hang down. This maximum sagging depth is measured at the center of the two rolls to determine the amount of tarmi.

  It is considered that this sagging occurs when the dimension of the film in the longitudinal direction is slightly different depending on the position in the width direction of the film. That is, since no tension is applied to a portion where the length of the film is long, the film hangs down and becomes tarmi, and in a portion where the length is short, the tension concentrates and becomes a tension state, and no tarmi is generated. Moreover, the location where tarmi occurs may be not only the end of the film roll, but also the center of the film roll.

  In order to reduce the amount of tarmi, when cooling the biaxially stretched and heat-set film, preferably in the temperature range of 100 to 160 ° C., depending on the shape of the tarmi (position of the tarmi) and the amount of tarmi, A method of performing a process of slightly spreading or shrinking on one or both side edges of the film can be used. This process can usually be adjusted by moving in the direction of widening the tenter clip interval (hereinafter referred to as “breading out process”) or moving in the direction of contraction (hereinafter referred to as relaxation process). The amount of the tentering or relaxation treatment is 0.1 to 2.0% with respect to the length from the center in the width direction of the film to the side edge (that is, half the length of the tenter clip interval). You can select and adjust within the range.

  When the side edge portion of the film is subjected to the tentering process, the length of the side edge part (the dimension in the longitudinal direction) becomes longer than before the tentering process, and conversely, it becomes shorter when the relaxation process is performed. The change in the length of the film due to the tentering or relaxation treatment is the largest at the side edge of the film, and the effect only slightly affects the center of the film. Accordingly, it is preferable to determine whether to select the tentering process or the relaxation process on the basis of the film length at the central portion of the film which is difficult to process.

  The above method is a method for improving the tarmi with a film of the master roll width, but in practice, the shape and amount of the tarmi are measured with a plurality of film rolls that are cut by winding the master roll into a product width. By connecting them, the shape and amount of talmi of the entire master roll are estimated. Based on the result, it is common to select the width setting or the relaxation treatment so that the amount of tarmi of the master roll becomes small. However, in that case, the amount of tarmi of the entire master roll may be minimized and the point at which the amount of tarmi of each film roll cut to the product width is minimized may not completely coincide. At this time, it is preferable to adjust so that the amount of talmi of the film roll cut into the product width becomes smaller.

  Furthermore, it is also possible to combine a relaxation treatment for reducing the shrinkage rate in the width direction of the biaxially stretched film, in addition to the above-described widthening and relaxation treatment for the purpose of reducing the amount of tarmi. In this case, the biaxially stretched film has a low shrinkage in the range of 0.1 to 10% of the tenter clip interval in the cooling zone of the maximum temperature region or lower temperature in the heat setting zone in the tenter. It is preferable that the order is such that a relaxation process is performed, and then, in the cooling zone where the temperature is lower, the above-described squeezing or relaxation process is performed for the purpose of reducing the amount of tarmi. At this time, the shrinkage rate in the film width direction is preferably 1.5% or less, more preferably 1.0% or less after the heat treatment at 180 ° C. for 5 minutes.

  The polyester film roll for a diffusion plate of the present invention is a film roll obtained by winding a biaxially stretched polyester film having a width of 800 mm or more, preferably 1000 mm or more. In the case of a film roll having a width of less than 800 mm, the demand for widening during film processing cannot be met.

  Using the polyester film roll for diffusion plate of the present invention, a known coating type light diffusion layer can be suitably provided on the coating layer containing the cationic polymer of the film. The coating type light diffusing layer is not particularly limited, but usually, a composition comprising at least one kind of inorganic particles or organic particles and a binder is preferably dissolved or dispersed in an organic solvent, and coated with a coater. It is coated on the coating layer containing the cationic polymer of the film. This light diffusion layer may be coated only on one side of the base film, or may be coated on both sides.

  The particles to be contained in the light diffusion layer are not particularly limited as long as they exhibit a light diffusion effect, but if exemplified, inorganic particles such as glass and silica, acrylic resin particles, polystyrene resin particles, nylon resin particles, Spherical particles such as organic particles such as polyester resin particles, polyurethane resin particles, silicone resin particles, and polyolefin resin particles are usually used. Although the particle diameter of these particles is not particularly limited, those having 1 to 50 μm are preferably used. Moreover, the particle diameter may be uniform or may not be uniform.

  Further, regarding the binder used for the light diffusion layer, a polymer having light resistance and transparency is preferable, and examples thereof include an acrylic resin, a polyester resin, a silicone acrylic resin, a fluororesin, and the like, or UV based on these. It may be crosslinked by curing, EB curing, heat curing, isocyanate curing, epoxy curing, or the like. The above binders may be used alone, or two or more kinds may be used in combination, and two or more kinds of prepolymers, oligomers, monomers, and crosslinking agents may be reacted.

  In addition, for the purpose of preventing damage to the prism layer or the like that may come into contact with the light diffusing layer, a known silicone-based or fluorine-based anti-sticking agent or polymer particles may be added to the light diffusing layer. Is possible.

  When the light diffusion layer is coated using an organic solvent, various solvents such as toluene, methyl ethyl ketone, xylene, ethyl acetate, butyl acetate, and cyclohexane are used as the solvent.

  Hereinafter, the configuration and effects of the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Various physical properties and characteristics are measured or defined as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester is precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added and dissolved, and measured at 30 ° C.

(2) Average particle size of fine particles (d ₅₀ : μm)
The value of 50% integration (weight basis) in the equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution measuring apparatus (SA-CP3 type manufactured by Shimadzu Corporation) is defined as the average particle diameter.

(3) Film haze (%)
According to JIS K7136, it measures using a haze measuring apparatus (HAZE METER HM-150 made by Murakami Color Research Laboratory).

(4) Thermal contraction rate of film (%)
In a hot air oven manufactured by Tabai Espec, the film sample length after heating at 180 ° C. for 5 minutes is defined as L1, and the film sample length before heating is defined as L0.
Thermal contraction rate (%) = (L0−L1) × 100 / L0

(5) Surface resistivity (Ω)
Using a high resistance measuring instrument HP4339B and measuring electrode HP16008B manufactured by Hewlett-Packard Japan, surface resistivity of the coating layer (Ω) after 1 minute at an applied voltage of 100 V in a measurement atmosphere of 23 ° C. and 50% RH Measure.

(6) Talmi amount of film (mm)
The film is unwound from the film roll, and spanned over two rolls installed in parallel and horizontally with an interval of 1.5 m so that the longitudinal direction of the film extends. When a tension of 0.39 MPa is evenly applied to the film between the two rolls, the film between the rolls is not always stretched uniformly, and either one or both ends in the width direction. Or, the central part may sag and hang down. The maximum depth of the sagging film is measured with an ultrasonic displacement sensor (UD-500 manufactured by Keyence Corporation) installed at the center of the two rolls to obtain the amount of talmi (mm). The ultrasonic displacement sensor is moved in the width direction of the film to continuously measure the amount of tarmi, thereby obtaining the shape of the tarmi in the film width direction.

(7) Running condition of film on coater A polyester film roll is set on the unwinder of the coater, and the running condition when the film is run is examined. The coater has a distance from the roll of the unwinding machine to the first roll of the next roll group of 0.9 m, observes the running state of the film during this period, and classifies it according to the following criteria.
A: There is no diagonal wrinkle on the film between rolls.
○: Although weak diagonal wrinkles are generated between rolls, the film on the entry side roll is stable.
(Triangle | delta): Generation | occurrence | production of the diagonal wrinkle is observed between rolls and a film repeats a slip periodically on an entrance side roll. (Tolerance)
X: Strong diagonal wrinkles are observed between the rolls, and the wrinkles are broken on the entrance roll.

(8) Degree of occurrence of coating defects (coating defects, coating unevenness) at the time of applying the light diffusion layer A polyester film roll is set on the coater used in (7), and the film is unwound. After disposing the blower type static eliminator on both sides of the polyester film and applying an ionic wind to the surface, remove the coating solution for forming the light diffusion layer shown below on the coating layer surface containing the cationic polymer of this film. Is applied by a reverse gravure method so that the coating amount after drying is 12 g / m ² . Thereafter, the light diffusion layer is applied by drying and curing with hot air. A three-wavelength fluorescent lamp is applied to the light diffusing layer, and the reflected light is visually observed to count the number per 100 m ² of the coating missing of 0.5 mm or more. The results are classified into the following criteria rank.
○: No coating missing Δ: One coating or less and less than five coatings ×: Five coatings or more coating missing Also, the light diffusion layer on the film was visually observed while running at a speed of 10 m / min. The presence or absence of unevenness is classified according to the following criteria.
○: No coating unevenness is seen Δ: Coating unevenness is slightly visible but cannot be determined when the film travel is stopped ×: Coating unevenness is clearly visible and can be determined even when the film travel is stopped

<Composition of coating solution for forming light diffusion layer>
Acrylic polyol (Acridick A-807, manufactured by Dainippon Ink and Chemicals, Inc.) 150 parts by weight Isocyanate (Takenate D11N, manufactured by Takeda Pharmaceutical Co., Ltd.) 30 parts by weight Methyl ethyl ketone 200 parts by weight Butyl acetate 200 parts by weight Acrylic resin fine particles (MX by Soken Chemical Co., Ltd.) -1000, average particle diameter 10 μm) 40 parts by weight

(9) Adhesive strength with light diffusing layer The diffusion plate created in (8) and using a polyester film as a base material. Cross-cut crosscuts (100 squares of 1 mm ² ) are applied, and 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) is applied on it, and rapidly with a peeling angle of 180 degrees. After peeling, observe the peeled surface, count the peeled area, and classify it into the following criteria rank.
○: Peeling area is less than 20% Δ: Peeling area is 20% or more and less than 50% ×: Peeling area is 50% or more

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing 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 adding 0.04 part of ethyl acid phosphate to this reaction mixture, germanium oxide in an ethylene glycol solution was added as germanium metal so as to be 100 ppm in the polymer, and a polycondensation reaction was performed 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 0.65 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 0.65.

<Method for producing polyester (B)>
The polyester (A) was pre-crystallized in advance at 160 ° C., and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C. to obtain an intrinsic viscosity 0.75 polyester (B).

<Method for producing polyester (C)>
In the method for producing polyester (A), after adding 0.04 part of ethyl acid phosphate, 0.2 part of silica particles dispersed in ethylene glycol having an average particle diameter of 2.2 μm and germanium oxide in an ethylene glycol solution Polyester (C) using the same method as the production method of polyester (A) except that the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65 in addition to 100 ppm as germanium metal in the polymer. ) The obtained polyester (C) had an intrinsic viscosity of 0.65.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Cationic polymer: (a1)
Quaternary ammonium salt-containing cationic polymer using diallyldimethylammonium chloride (a pyrrolidinium ring-containing cationic polymer of (formula 1)) average molecular weight of about 30,000.
Cationic polymer: (a2)
Quaternary ammonium salt-containing cationic polymer using diallylmonomethylammonium methanesulfonate (a pyrrolidinium ring-containing cationic polymer of (formula 1)) average molecular weight of about 30,000.
Cationic polymer: (a3)
Poly (trimethylammonium ethyl methacrylate) monomethyl sulfate homopolymer (cationic polymer of formula (5))
-Binder polymer: (b)
Water-based acrylic resin (Nicarbazole with an acid value of 6 mgKOH / g, manufactured by Nippon Carbide Industries Co., Ltd.)
・ Crosslinking agent: (c)
Crosslinkable resin of alkylol melamine / urea copolymer (Bekkamin manufactured by Dainippon Ink and Chemicals)
・ Fine particles: (d)
Ethylene glycol grafted silicon dioxide fine particles (average particle size 0.15 μm, graft rate 1.7 mmol / g)
・ Additive: (e)
Polyethylene oxide adduct to diglycerin skeleton (average molecular weight 450)

Examples 1, 2, 3 and Comparative Example 1:
A mixed raw material in which polyesters (B) and (C) are mixed at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer), and a raw material for the polyester (A) is used as a raw material for the intermediate layer. Each was melted at 285 ° C. and then coextruded in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set to 40 ° C. to obtain an unstretched sheet. . Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the difference in roll peripheral speed. Corona discharge treatment is applied to both sides of this longitudinally stretched film, and a coating liquid having a solid content composition of a1 / b / c / d / e = 27/45/20/3/5 (weight%) is applied by a reverse gravure method. did. After this, it was led to a tenter, dried and preheated at 120 ° C, stretched 4.0 times in the width direction, further heat treated at 220 ° C, and then relaxed 4% in the width direction in the 180 ° C cooling zone. A polyester film having a thickness of 100 μm (surface layer 5 μm each, intermediate layer 90 μm) having a 0.08 μm coating layer. This film was once wound up as a master roll, and further slit into a plurality of film rolls having a product width of 1000 mm. About this film roll, when the amount of talmi and the shape of talmi were measured, it was a shape in which talmi was generated at the center of the master roll. The amount of talmi of the film roll was 14 mm at maximum (Comparative Example 1) and 12 mm at minimum. (Example 3). For this reason, as a feedback to the film forming conditions, in the cooling zone of the tenter at 130 ° C., a tentering process was performed so as to widen the distance between the left and right tenter clips. After this adjustment, a film roll having a product width of 1000 mm was similarly collected from the master roll, and the amount of tarmi was measured. As a result, the maximum was 8 mm (Example 2), and the minimum was 5 mm (Example 1). A light diffusion layer was applied to these film rolls. The results and the characteristics of the biaxially oriented polyester film are shown in Tables 1 and 2, and the width of the film roll is 1000 mm, which meets the demand for widening. Moreover, in Examples 1, 2, and 3, since the surface resistivity value of the coating layer containing the cationic polymer of the film and the amount of talmi of the film are within the scope of the present invention, when applying the subsequent light diffusion layer, There was no trouble in coating unevenness due to static electricity and troubles in coating, and the film runnability on the coater was good or within an acceptable range, and the polyester film roll for diffusion plate had good productivity. On the other hand, in Comparative Example 1, although the surface specific resistance value is good, since the amount of tarmi of the film exceeds the range of the present invention, the running property of the film on the coater is poor, and the light diffusion layer is Could not be applied.

Example 4:
In Example 3, the composition of the coating solution applied to both surfaces of the film was changed to a solid content composition of a2 / b / c / d / e = 27/45/20/3/5 (% by weight). The other coextrusion and film formation were carried out in the same manner to obtain a polyester film having a thickness of 100 μm (surface layer: 5 μm, intermediate layer: 90 μm) having a coating layer of 0.08 μm on both sides. This film was once wound up as a master roll and further slit into a plurality of film rolls having a product width of 1500 mm. About this film roll, when the amount of talmi and the shape of talmi were measured, it was a shape where talmi was generated in the central part of the master roll. For this reason, as a feedback to the film forming conditions, in the cooling zone of the tenter at 130 ° C., a tentering process was performed so as to widen the distance between the left and right tenter clips. After this adjustment, a film roll having a product width of 1500 mm was again collected from the master roll, and the amount of talmi was measured to be 5 mm at maximum (Example 4). A light diffusion layer was applied to the film roll. The results and the characteristics of the biaxially oriented polyester film are shown in Table 1. The width of the film roll is 1500 mm, which meets the demand for widening. Further, in Example 4, since the surface specific resistance value of the coating layer containing the cationic polymer of the film and the amount of talmi of the film are within the scope of the present invention, the coating unevenness due to static electricity is applied when the subsequent light diffusion layer is applied. In addition, there was no trouble in coating and coating, and the film runnability on the coater was good, and the polyester film raw material for the diffusion plate had good productivity.

Example 5:
In Example 3, the composition of the coating solution applied to both surfaces of the film was changed to a solid content composition of a3 / b / c / d = 32/45/20/3 (% by weight). The other coextrusion and film formation were carried out in the same manner to obtain a polyester film having a thickness of 100 μm (surface layer: 5 μm, intermediate layer: 90 μm) having a coating layer of 0.08 μm on both sides. This film was once wound up as a master roll, and further slit into a plurality of film rolls having a product width of 1000 mm. About this film roll, when the amount of talmi and the shape of talmi were measured, it was a shape where talmi was generated at one end of the master roll. For this reason, as a feedback to the film forming conditions, in the cooling zone of the tenter at 130 ° C., a relaxation process was performed so as to narrow only the tenter clip on the end side where the tarmi was generated. After this adjustment, a film roll having a product width of 1000 mm was similarly collected from the master roll, and the amount of talmi was measured to obtain a maximum of 4 mm (Example 5). A light diffusion layer was applied to the film roll. The results and the characteristics of the biaxially oriented polyester film are shown in Table 1. The width of the film roll is 1000 mm, which meets the demand for widening. Further, in Example 5, since the surface specific resistance value of the coating layer containing the cationic polymer of the film and the amount of talmi of the film are within the scope of the present invention, the coating unevenness due to static electricity is applied when the subsequent light diffusion layer is applied. In addition, since there was little trouble with coating and removal, and the film runnability on the coater was good, the polyester film roll for the diffusion plate had good productivity.

Comparative Example 2:
In Example 3, the composition of the coating solution applied to both surfaces of the film was changed to a solid content composition of a3 / b / c / d = 5/72/20/3 (% by weight). The other coextrusion and film formation were carried out in the same manner to obtain a polyester film having a thickness of 100 μm (surface layer: 5 μm, intermediate layer: 90 μm) having a coating layer of 0.08 μm on both sides. This film was once wound up as a master roll, and further slit into a plurality of film rolls having a product width of 1000 mm. About this film roll, when the amount of talmi and the shape of talmi were measured, it was a shape where talmi was generated at both ends of the master roll. For this reason, as a feedback to the film forming conditions, in the cooling zone of the tenter at 130 ° C., a relaxation treatment was performed so as to narrow both the left and right tenter clip intervals. After this adjustment, a film roll having a product width of 1000 mm was similarly collected from the master roll, and the amount of talmi was measured to obtain a maximum of 5 mm (Comparative Example 2). A light diffusion layer was applied to the film roll. The results and the characteristics of the biaxially oriented polyester film are shown in Table 2. The width of the film roll is 1000 mm, which meets the demand for widening. However, in Comparative Example 2, the runnability of the film on the coater is good, and the coating layer of the film contains a cationic polymer, but the surface resistivity is outside the range of the present invention. Thus, a uniform light diffusion layer could not be applied.

  The film roll of the present invention can be suitably used for a diffusion plate.

Claims (1)

After heat setting, it is subjected to a tentering treatment or a relaxation treatment in a temperature range of 100 to 160 ° C., and has a coating layer containing a cationic polymer on at least one surface, and the coating layer has a surface resistivity of 1 × 10 ¹³ Ω. The following biaxially oriented polyester film is a film roll wound up with a width of 800 mm or more, and when a tension of 0.39 MPa is evenly applied at an interval of 1.5 m in the longitudinal direction of the film, A polyester film roll characterized in that the amount of tarmi generated is 12 mm or less.