JP2014233901A - Laminate polyester film roll for optical use - Google Patents

Abstract

An optical polyester film roll that can suppress the occurrence of film deflection even when subjected to a thermal history.
A film roll having a film width of 2500 mm or more obtained by winding a laminated polyester film having a thickness of 188 to 350 μm consisting of at least three layers, and having a shrinkage ratio of 1.0% in the longitudinal direction of the film after treatment at 150 ° C. for 30 minutes. The difference in shrinkage between the end position and the center position in the film roll width direction of the heat shrinkage rate under the same conditions is 0.30% or less, and the film elongation at 100 ° C. is 0.20% or less. A laminated polyester film roll for optics,
[Selection figure] None

Description

  The present invention relates to a laminated polyester film roll suitable for optical use that can suppress the occurrence of film deflection even when subjected to a thermal history during processing or use.

  Polyester films, especially biaxially stretched films of polyethylene terephthalate and polyethylene naphthalate, have excellent mechanical properties, heat resistance, and chemical resistance, so magnetic tape, ferromagnetic thin film tape, photographic film, packaging film, electronic It is widely used as a material for parts films, electrical insulating films, metal laminate films, films to be attached to glass surfaces such as glass displays, and protective films for various members.

  In recent years, polyester films have been widely used for various optical films, in particular, prism films for LCD members, light diffusion sheets, reflectors, touch panels, and other base films, antireflection base films, display explosion-proof base films, and PDPs. It is used for various applications such as filter films. In these optical products, in order to obtain a bright and clear image, the base film used as an optical film needs to have good transparency and no defects such as foreign matter and scratches that affect the image. .

  In addition, it is necessary for obtaining an image having no unevenness even when polarized light is used, in particular, that there is no retardation unevenness due to uneven orientation of the polymer and uneven thickness.

  Polyester film can be obtained by melt-extrusion, usually in the form of a sheet, and by stretching an amorphous sheet obtained by rapid cooling and solidification in the machine direction and transverse direction, followed by heat treatment. If the property is not sufficient, the above-mentioned retardation unevenness remains, and there is a problem that the image deteriorates when used for optics.

  In addition, heat resistance is an important characteristic in displays, and it is known that the polyester film used as a member affects the heat resistance. In particular, in order to obtain a high quality image, high heat resistance has been required. For this purpose, it goes without saying that the polyester film has a high heat resistance, but in addition to this, it is necessary that the polyester film has a further advantageous property in terms of luminance.

JP 2006-292838 A Japanese Patent Application No. 2006-181746 JP 2002-350617 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is a polyester film roll suitable for optical use that can suppress the occurrence of film deflection even when subjected to thermal history during processing or use. It is to provide.

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

  That is, the gist of the present invention is a film roll having a film width of 2500 mm or more obtained by winding a laminated polyester film having a thickness of 188 to 350 μm consisting of at least three layers, and has a shrinkage ratio in the longitudinal direction of the film after treatment at 150 ° C. for 30 minutes. 1.0% or less, the shrinkage difference between the end position and the center position in the film roll width direction of the heat shrinkage rate under the same conditions is 0.30% or less, and the film elongation rate at 100 ° C. is 0.00. It exists in the laminated polyester film roll for optics characterized by being 20% or less.

  According to the present invention, it is possible to provide a polyester film roll suitable for optical use that can suppress the occurrence of film deflection even when subjected to thermal history during processing or use, and the industrial value of the present invention is high.

  The polyester used for the polyester film in the present invention refers to a polyester obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like.

  The polyester in the present invention is a conventionally known method, for example, a method of directly obtaining a low-polymerization degree polyester by reaction of a dicarboxylic acid and a diol, or a lower alkyl ester of a dicarboxylic acid and a diol reacted with a conventionally known transesterification catalyst. Then, it can obtain by the method of performing a polymerization reaction 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. Preferably, the amount of antimony compound is zero or 100% or less as antimony to reduce film dullness. .

  The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dl / g or more, and preferably 0.40 to 0.90 dl / g.

  In the polyester layer of the film of the present invention, particles can be blended mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples include inorganic particles such as magnesium, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

The shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc.
These series of particles may be used in combination of two or more as required.

  The average particle diameter of the particles is usually 5 μm or less, preferably 0.01 to 3 μm. When the average particle diameter exceeds 5 μm, the surface roughness of the film becomes too rough, and the transparency may be insufficient.

  Further, the content of particles in the polyester layer is usually less than 5% by weight, preferably in the range of 0.0003 to 3% by weight. When there are no or few particles, the transparency of the film becomes high and the film becomes a good film, but the slipperiness may be insufficient. There are cases where improvement is required. Further, when the particle content exceeds 5% by weight, the transparency of the film may be insufficient.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, heat stabilizers, ultraviolet absorbers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary. Can do.

  The thickness of the polyester film of the present invention is in the range of 188 to 350 μm. Outside the above range, it is not suitable for optical use.

  The polyester film of the present invention has a total light transmittance of usually 88.0% or more, preferably 88.5% or more, more preferably 89.0% or more. The film of the present invention is widely used for optical applications because of its excellent light transmittance. However, when the total light transmittance is less than 88.0%, it may be inappropriate for optical use. .

  The film haze of the polyester film of the present invention is usually 2.5% or less, preferably 0.5 to 2.0%, more preferably 0.5 to 1.8%. The film of the present invention is widely used in optical applications because of its excellent transparency. However, when the film haze exceeds 2.5%, it may be unsuitable for optical use.

  The polyester film of the present invention has a film longitudinal direction (MD) value of 1.0% or less with respect to the heat shrinkage after treatment at 150 ° C. for 30 minutes. Further, the heat shrinkage in the film width direction (TD) is usually 0.3% or less, preferably 0.2% or less. If the film shrinkage rate in the longitudinal direction (MD) exceeds 1.0%, the dimensional stability of the film will be impaired when used as a display product member, resulting in distortion and unevenness in the image, and high image quality. Cause deterioration.

  Furthermore, in the film roll of the present invention, the difference in shrinkage ratio between the end position and the central position in the film roll width direction is 0.30% or less in the shrinkage ratio in the film longitudinal direction after treatment at 150 ° C. for 30 minutes. If the difference in thermal shrinkage rate exceeds 0.30%, the shrinkage rate is different at each position of the film and cannot be used as an optical application.

  The polyester film of the present invention has a film longitudinal direction (MD) value of 0.20% or less, preferably 0.15 or less, with respect to the elongation percentage of the film at 100 ° C. If this elongation exceeds 0.20%, when used as a member of a display product, the film will bend due to the heat generated by the backlight or electronic circuit, and the image will be distorted or uneven, which is not suitable for display applications. Appropriate.

The color tone y value when the polyester film of the present invention is measured by the reflection method is preferably 0.3250 or less, more preferably 0.3230 or less. When the color tone y value exceeds 0.3250, when the film has a strong yellowish color and is used for a display, the color tone of the image becomes inferior or the luminance becomes low. There is.
In order to obtain a film having such a color tone, the catalyst and auxiliary agent for producing the raw material polyester are selected, the amount of the catalyst is reduced as much as possible, and the temperature of the polyester becomes higher than necessary during polymerization and film formation. Or a method such as preventing the melting time from becoming long.

  The film of the present invention can be formed into a laminated structure using a co-extrusion method. In this case, it is preferable that the outermost layer thickness is usually 3 μm or more and ¼ or less of the total thickness on one side. When the thickness is less than 3 μm, oligomers (cyclic trimers) contained in the inner layer are deposited on the film surface due to heat history during processing, etc., and contamination of the production line and an increase in the amount of foreign matter on the film surface are observed. On the other hand, if it is thicker than 1/4 of the total thickness, the amount of particles to be blended in the outermost layer may increase and the transparency may be impaired.

  On the other hand, when the present invention is carried out with a single layer, it is also preferable that the film is made to contain no particles as much as possible, and the particles are contained in the front and back coating layers.

  Moreover, when adding additives, such as the said ultraviolet absorber and dye, it is preferable to mix | blend with the intermediate | middle layer of a laminated | multilayer film.

Hereinafter, although the manufacturing method of the polyester film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.
First, a dried or undried polyester chip by a known method is supplied to a melt extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer and melted. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 5 times in the longitudinal direction at 70 to 145 ° C. to form a longitudinal uniaxially stretched film, and then in the transverse direction at 90 to 160 ° C. It is preferable to perform 2 to 5 times stretching and to perform heat treatment at 200 to 240 ° C. for 10 to 600 seconds. Further, at this time, a method of relaxing 1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the outlet of the heat treatment is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

In the present invention, as described above, two or more polyester melt extruders can be used to form a laminated film of three or more layers by a so-called coextrusion method. As the structure of the layer, an A / B / A structure using the A raw material and the B raw material, and further a film having an A / B / C structure or other structure using the C raw material can be obtained. For example, the surface shape of the A layer can be designed by using specific particles as the A raw material, and a film having an A / B / A structure can be obtained by using a raw material not containing particles as the B raw material. In this case, since the raw material of B layer can be selected freely, a cost advantage etc. are large.

In particular, since the film of the present invention is used for optical applications, a hard coat layer, an antireflection layer, an antiglare layer, or the like is provided, or a vapor deposition layer or the like is provided. A coating layer as an undercoat layer can be provided for the purpose of improving adhesion or preventing charging in order to keep the surface clean. In forming such a coating layer, the method of forming a film, in particular, after stretching in the longitudinal direction and before stretching in the lateral direction can form a very thin coating layer, and the coating solution drying and curing reaction Is preferable in that it can be carried out in the film forming process. The coating layer is preferably a combination of a crosslinking agent and various binder resins, and as the binder resin, a polymer selected from polyester, acrylic polymer and polyurethane is usually employed from the viewpoint of adhesiveness. Each of the above polymers shall also include derivatives thereof. The derivative here refers to a polymer obtained by reacting a reactive compound with a copolymer or a functional group with another polymer.
In addition, you may coat by an offline coat after manufacture of a film as needed. Moreover, it does not matter on one side or both sides. The coating material may be either water-based and / or solvent-based for offline coating, but is preferably water-based or water-dispersed for in-line coating.

  In addition, since the film of the present invention is used for optics, it is also preferable to form a functional multilayer thin film for the purpose of preventing dust reflection due to reflection of external light and static electricity, as well as electromagnetic shielding, in addition to improving adhesiveness. .

  Among the polyesters, acrylic polymers, and polyurethanes that are used as coating agents in the present invention, particularly preferred polymers have a glass transition temperature (Tg) of 0 ° C. or higher, more preferably 40 ° C. or higher. It is a polyurethane having a carboxylic acid residue, at least a part of which is made water-based using an amine or ammonia.

  As the crosslinking agent resin, melamine-based, epoxy-based, and oxazoline-based resins are generally used, but melamine-based resins are particularly preferable from the viewpoints of coatability and durable adhesiveness. The melamine-based resin may be either a monomer, a condensate composed of a dimer or higher multimer, or a mixture thereof.

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

Examples of the inorganic particles include silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black, molybdenum sulfide, and antimony oxide. Among these, silicon dioxide is easy to use because it is inexpensive and has various particle sizes. On the other hand, examples of the organic particles include polystyrene or polyacrylate polymethacrylate in which a crosslinked structure is achieved by a compound containing two or more carbon-carbon double bonds in one molecule (for example, divinylbenzene).
The above inorganic particles and organic particles may be surface-treated. Examples of the surface treatment agent include a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, and the like. The content of the particles in the coating layer is preferably 10% by weight or less, more preferably 5% by weight or less as an appropriate addition amount that does not impair the transparency.

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

  As long as water is the main medium, the coating agent may contain a small amount of an organic solvent for the purpose of improving dispersion in water or improving the film-forming performance. It is necessary to use the organic solvent as long as it is soluble in water. Examples of the organic solvent include aliphatic or alicyclic alcohols such as n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, and methyl alcohol, glycols such as propylene glycol, ethylene glycol, and diethylene glycol, n-butyl cellosolve, Examples thereof include ketones such as ethyl cellosolve, methyl cellostel, methyl ethyl ketone and acetone, and amides such as N-methylpyrrolidone. These organic solvents may be used in combination of two or more as required.

  Examples of the coating method of the coating agent include gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze coating, impregnation coating, kiss coating, Conventionally known coating methods such as spray coating, calendar coating and extrusion coating can be used.

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

  The thickness of the coating layer is usually 0.01 to 0.5 μm, preferably 0.015 to 0.3 μm as the final dry thickness. When the thickness of the coating layer is less than 0.01 μm, the effect of the present invention may not be sufficiently exhibited. When the thickness of the coating layer exceeds 0.5 μm, the films tend to stick to each other, and particularly when the coated film is re-stretched to increase the strength of the film, it adheres to the roll in the process. There is a tendency to become easy. The above problem of sticking appears particularly when the same coating layer is formed on both sides of the film.

  When such a coating film is applied to an optical application, the coating layer surface coating is problematic when an antireflection layer or the like is provided on the coating layer. The reason for the occurrence of coating leakage is not clear, but foreign matter in the film creates coarse protrusions on the surface of the film, which acts as a core and the coating agent repels and stretches to cause coating leakage or the film surface. There may be a case where the oligomer or dust attached to the core becomes a nucleus and the coating agent repels and disappears from the nucleus. Therefore, it is necessary to form a film under such a condition that dust and foreign matters that can become nuclei are removed as much as possible. Such foreign substances include oligomers adhered or deposited on the film, so that reducing the amount of oligomers contained in the film has the effect of reducing the amount of coating.

When the film of the present invention thus obtained has a coating layer, the number (N) of coating spots is preferably 50 or less per 10 m ^{2 of} film, more preferably 30 or less, particularly preferably 10 or less. It is. In any case, in an optical film that will become more and more severe in the future, it is necessary to reduce the coating amount to 0 as much as possible.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measuring method used in the present invention is as follows.

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

(2) Total light transmittance, haze Total light transmittance is JIS-K-7361, and haze is based on JIS-K-7136 by Nippon Denshoku Industries Co., Ltd. integrating sphere turbidimeter “NDH2000”. The rate and haze were measured.

(3) Heat shrinkage rate The sample was treated for 30 minutes in an oven maintained at 150 ° C. in a tensionless state, the length of the sample before and after that was measured, and the heat shrinkage rate was calculated by the following equation.
Heat shrinkage rate (%) = {(L0−L1) / L0} × 100
(In the above formula, L0 is the sample length before the heat treatment, L1 is the sample length after the heat treatment), and the heat shrinkage in the longitudinal direction is measured at 7 points in the width direction of the film roll, and the average value thereof. Asked.

(4) Heat shrinkage difference The film shrinkage ratio in the film longitudinal direction after treatment at 150 ° C. for 30 minutes at the end position and the center position in the film roll width direction is determined, respectively, and from the value of the larger shrinkage ratio at the positions at both ends. The difference was obtained by subtracting the shrinkage value at the center position.

(5) Reflection method y value The film surface was measured using a spectral colorimeter CM-3700d manufactured by Konica Minolta so that the films were overlapped to have a thickness of about 1000 μm (4 sheets at 250 μm). A C light source and a 2 ° field of view were used, and the color system was XYZ (CIE 1931).
y = Y / (X + Y + Z)

(6) Elongation Measurement by TMA (Thermomechanical Analysis) Using TMA SS6000 manufactured by SII, a sample cut out to 2 mm × 20 mm is set in a sample holder, and the initial load is 50 mN, the temperature rising rate is 5 ° C./min. The elongation rate up to 180 ° C. was measured.
Elongation rate (%) = {(L1-L0) / L0} × 100
(In the above formula, L0 is the sample length before the heat treatment, L1 is the sample length after the heat treatment) 5 points were measured in the film longitudinal direction (MD), and the MD elongation at around 100 ° C. was measured.

(7) Film flatness measurement A film cut to a size of 1 m × 1 m was placed on a horizontal glass plane, the film surface was visually observed after 3 minutes to allow air between the glass plane and the film to escape, and the film The flatness was confirmed from the presence or absence of the upper deflection. When the flatness is evaluated based on the number of deflections with a size of 100 mm or more, ◎ when there is no deflection, ○ when there are 1-2 deflections, and when 3-6 △, and x when 7 or more places occurred.

(8) Luminance measurement Using Konica Minolta Color Luminance Meter CS-200, samples cut into A4 size are superposed so that the thickness is about 1000 μm (4 pieces at 250 μm), placed on a measurement table, and brightness is measured. went. As a result of measuring the luminance, the luminance of Example 1 was set to 100%, and the evaluation was performed with relative luminance.

Examples and Comparative Examples are shown below, and the method for producing the polyester used in the Examples and Comparative Examples is as follows.
<Manufacture of polyester>
<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 0.04 part of ethyl acid phosphate was added to this reaction mixture, 0.03 part of antimony trioxide was added and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.68 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 0.68.

<Method for producing polyester (B)>
In the production method of polyester (A), after adding 0.04 part of ethyl acid phosphate, 0.3 part of silica particles having an average particle diameter of 2.2 μm dispersed in ethylene glycol and 0.03 part of antimony trioxide were added. In addition, polyester (B) was obtained using the same method as the production method of polyester (A) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.66. The obtained polyester (B) had an intrinsic viscosity of 0.66.

<Method for producing polyester (C)>
In the method for producing polyester (A), the starting material is 100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol and 2 parts by weight of diethylene glycol, and the method for producing polyester (A) is used except that germanium oxide is used as a polymerization catalyst. A polyester (C) was obtained using the same method as described above. In addition, the addition method of germanium oxide employ | adopted the well-known method, The addition amount was 100 ppm with respect to the raw material weight as germanium. The intrinsic viscosity of the obtained polyester (C) was 0.68.

Example 1:
Two vented twin-screw extrusions using the above-mentioned polyesters (A) and (B) mixed at a ratio of 90% and 10%, respectively, as the raw material for the A layer and the polyester (C) as the raw material for the B layer Each is supplied to the machine and melted at 285 ° C., and two types and three layers with the A layer as the outermost layer (surface layer) and the B layer as the intermediate layer (A / B / A = 1: 18: 1 discharge amount) Coextruded with a layer structure of the above, extruded from a die, and cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method, to obtain an unstretched sheet. Next, the film was stretched 3.0 times in the machine direction at a film temperature of 80 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 3.7 times in the transverse direction at 130 ° C., and heat-treated at 232 ° C. Thereafter, the film was relaxed by 2% in the transverse direction to obtain a laminated polyester film having a thickness of 250 μm.

Example 2:
A polyester film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was changed to 227 ° C. in Example 1.

Example 3:
A polyester film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was changed to 222 ° C. in Example 1.

Example 4:
A polyester film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was changed to 217 ° C. in Example 1.

Comparative Example 1:
A polyester film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was 240 ° C. in Example 1.

Comparative Example 2:
A polyester film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was 210 ° C. in Example 1.

  The physical properties and flatness of the obtained film are summarized in Table 1 below. A film satisfying the requirements of the present invention was excellent in heat resistance and good in flatness. Furthermore, the effect of increasing the brightness due to the low heat treatment temperature in the tenter was confirmed. This is considered to be an effect in which the thermal deterioration of the film is suppressed.

  The film roll of the present invention can be suitably used as a base material for, for example, a diffusion sheet, a prism sheet, or a composite sheet.

Claims (1)

It is a film roll having a film width of 2500 mm or more obtained by winding up a laminated polyester film having a thickness of 188 to 350 μm consisting of at least three layers, and the shrinkage ratio in the film longitudinal direction after treatment at 150 ° C. for 30 minutes is 1.0% or less, The difference in shrinkage rate between the end position and the center position in the film roll width direction of the heat shrinkage rate under the same conditions is 0.30% or less, and the film elongation rate at 100 ° C. is 0.20% or less. An optical laminated polyester film roll.