JP2006187910A - Biaxially oriented laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated film having a practically sufficient reflecting capacity in a visible region, stably formed even if fine particles are added in a high concentration, having excellent ply separation force and suitable as a base material for a reflecting panel for use in a liquid crystal display or an internal illumination type decorative illumination signboard. <P>SOLUTION: The biaxially oriented laminated film comprises a layer A consisting of a polyester composition, which is composed of 45-80 wt.% of fine particles with an average particle size of 0.1-10 μm and 20-55 wt.% of a polyester with an intrinsic viscosity of 0.45-0.65, and a layer B, which is adjacent to the layer A and consists of a polyester composition composed of 0.1-15 wt.% of fine particles with an average particle size of 0.1-10 μm and 85-99.9 wt.% of the polyester with an intrisic viscosity of 0.45-0.65, and the peel strength of the layers A and B is 200 g or above. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biaxially oriented laminated film, and more particularly to a biaxially oriented laminated film having high stretching performance and high reflectance.

  Conventionally, a liquid crystal display employs a backlight system in which light is applied from the back of the display. In recent years, a sidelight system as disclosed in Japanese Patent Laid-Open No. 63-62104 has been widely used because of its merit of being thin and uniform. This sidelight method is a method of illuminating a cold cathode tube or the like from an edge of an acrylic board or the like with a certain thickness. For halftone printing, the illumination light is evenly distributed and has a uniform brightness. A screen is obtained. This method can be made thinner than the backlight method because the lighting is installed not at the back of the screen but at the edge. In this case, in order to prevent the illumination light from escaping to the back of the screen, a reflector is installed on the back of the screen. This reflector is required to have high light reflectivity and high diffusibility.

  As a method for obtaining a polyester film suitable for a liquid crystal display reflector that meets this purpose, a method of incorporating an incompatible resin is known. This is a method that can be made relatively inexpensive. For example, it is described in Japanese Patent Publication No. 8-16175.

JP-A-63-137927 Japanese Patent Publication No. 8-16175 Japanese Patent Laid-Open No. 3-76727 JP-A-3-132331

  However, the addition of an incompatible resin is not sufficient in terms of improving the reflectance, and the brightness of the resulting liquid crystal display screen is also insufficient. In addition, when a high concentration of fine particles such as titanium oxide is added, an improvement in reflection efficiency can be expected. However, when a high concentration is added up to about 45% by weight, for example, the concentration of the fine particles is so high that breakage frequently occurs. It is very difficult to form a film. Further, when a high concentration of fine particles is present in the layer, the film is inferior in the delamination force, and the problem of peeling between the layers is likely to occur.

  An object of the present invention is to solve the problems of the prior art. That is, the present invention provides a practically sufficient visible light region reflection performance, a liquid crystal display having a high delamination force while being a laminated film that can be stably formed even if fine particles are added at a high concentration. An object is to provide a biaxially oriented laminated film suitable for a reflector for an internally illuminated electric signboard.

  That is, the present invention relates to a layer A of a polyester composition comprising 45 to 80% by weight of fine particles having an average particle size of 0.1 to 10 μm and 20 to 55% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65. A layer B of polyester composition consisting of 0.1 to 15% by weight of fine particles having an average particle size of 0.1 to 10 μm and 85 to 99.9% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65. It is a laminated film, and is a biaxially oriented laminated film having a peel strength between layer A and layer B of 200 g or more.

  According to the present invention, a liquid crystal display having a high delamination force while being a laminated film that has a practically sufficient visible light region reflection performance and can be stably formed even if fine particles are added at a high concentration. A biaxially oriented laminated film that is suitable as a base material for a reflector for an internally illuminated electric signboard can be provided.

Hereinafter, the present invention will be described in detail.
[polyester]
As the polyester of the polyester composition, a polyester composed of a dicarboxylic acid component and a diol component is used. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, and sebacic acid. Examples of the diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol. Of these polyesters, polyethylene terephthalate is preferred.

  The polyester is preferably a copolyester, particularly preferably copolyethylene terephthalate. The ratio of the copolymerization component is preferably 4 to 15 mol%, more preferably 5 to 14 mol%, further preferably 3 to 14 mol%, and particularly preferably 6 to 13 mol% per total dicarboxylic acid component. When the proportion of the copolymerization component is less than 4 mol%, a layer containing fine particles, for example, 45% by weight or more of inert particles may not be formed, which is not preferable. If the proportion of the copolymerization component exceeds 15 mol%, it may be a film lacking in thermal dimensional stability, or a situation where even film formation cannot be achieved is not preferable.

When the polyester is polyethylene terephthalate, examples of the copolymer component include isophthalic acid and 2,6-naphthalenedicarboxylic acid. Copolymerized polyethylene terephthalate using isophthalic acid and / or 2,6-naphthalenedicarboxylic acid and having a total copolymerization amount of 4 to 15 mol% is a preferred polyester.
Additives such as antioxidants, antistatic agents, fluorescent whitening agents, and ultraviolet absorbers may be added to the polyester.

[Layer structure]
In the present invention, layer A is a layer of a polyester composition comprising 45 to 80% by weight of fine particles having an average particle size of 0.1 to 10 μm and 20 to 55% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65. The intrinsic viscosity of this polyester is preferably 0.47 to 0.63, more preferably 0.49 to 0.61. If the intrinsic viscosity is less than 0.45, the stretchability may be extremely impaired and the film may not be formed. If it exceeds 0.65, the extrusion pressure is high, and the pressure during melt filtration is too high. Problem arises.

Layer B adjacent to layer A is a polyester composition comprising 0.1 to 15% by weight of fine particles having an average particle size of 0.1 to 10 μm and 85 to 99.9% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65. It is a layer of things. The intrinsic viscosity of this polyester is preferably 0.46 to 0.63, more preferably 0.47 to 0.61. If the intrinsic viscosity is less than 0.45, the stretchability may be extremely impaired and the film may not be formed. If it exceeds 0.65, the extrusion pressure is high, and the pressure during melt filtration becomes too high. Problems arise.
In the present invention, the layer A and the layer B are adjacent to each other, but an embodiment of a laminated film having a three-layer structure in which the layer B is disposed on both sides of the layer A is a preferable embodiment.

[Fine particles]
In the present invention, the layer A contains 45 to 80% by weight, preferably 50 to 70% by weight, more preferably 50 to 60% by weight of fine particles having an average particle size of 0.1 to 10 μm. If it is less than 45% by weight, the reflectivity is low, and if it exceeds 80% by weight, it tends to break and may not be a film.

  Layer B contains 0.1 to 15% by weight, preferably 0.5 to 14% by weight, and more preferably 1.0 to 13% by weight of fine particles having an average particle size of 0.1 to 10 μm. If it is less than 0.1% by weight, it is also used for the outermost layer, so that the film has poor slipperiness and is very difficult to handle. If it exceeds 15% by weight, the stretchability may become unstable.

  The average particle diameter of the fine particles is 0.1 to 10 μm, preferably 0.1 to 5 μm, and more preferably 0.3 to 3 μm. If the average particle size is less than 0.1 μm, the dispersibility becomes extremely poor and the aggregation of the particles occurs. Therefore, troubles in the production process are likely to occur, and coarse projections are formed on the film, resulting in a film with poor gloss. There is a possibility. When it exceeds 10 μm, the film surface becomes rough or the film has poor stretchability.

  As the fine particles, it is preferable to use a white pigment from the viewpoint of improving the reflection performance. Examples of the fine particles include titanium oxide, barium sulfate, calcium carbonate, and silicon dioxide. The titanium oxide is preferably a rutile type. This is because the rutile type has less yellowing after irradiating the polyester film with light for a longer time than the anatase type, and is suitable for suppressing the change in color difference.

  Among the fine particles, barium sulfate is particularly preferable from the viewpoint of improving the reflectance. Barium sulfate may have a plate-like or spherical particle shape. In particular, rutile titanium oxide is preferably used after treatment with a fatty acid such as stearic acid or a derivative thereof in order to improve dispersibility, since the glossiness of the film can be further improved.

  When rutile titanium oxide is used, it is preferable to adjust the particle size and remove coarse particles using a purification process before adding to the polyester. As industrial means of the purification process, for example, a jet mill or a ball mill can be applied as a pulverizing means, and as a classification means, for example, dry or wet centrifugation can be applied. Two or more of these means may be combined and purified step by step.

Various methods can be used as a method of incorporating the fine particles into the polyester. The following method can be mentioned as the typical method.
(A) A method of adding before transesterification or esterification reaction at the time of polyester synthesis or adding before the start of polycondensation reaction.
(A) A method of adding to polyester and melt-kneading.
(C) A method of producing master pellets to which a large amount of inert particles are added in the method (a) or (b) above, and kneading these with a polyester not containing an additive to contain a predetermined amount of additive.
(D) A method of using the master pellet of (c) as it is.

  It is preferable to take the above method (c) or (d). In addition, when using the method of said (a), it is preferable to add to a reaction system as a slurry disperse | distributed to glycol in titanium oxide.

  In general, fine particles often aggregate to become coarse aggregate particles. In the present invention, in order to reduce the number of coarse agglomerated particles, a non-woven filter having an average opening of 10 to 100 μm, preferably an average opening of 15 to 50 μm, made of stainless steel fine wire having a wire diameter of 15 μm or less is used as a filter during film formation. It is preferred to use and filter the molten polymer.

[Additive]
In the polyester composition, other additives such as aluminum oxide, magnesium oxide, acrylic resin, urea resin, organic filler such as melamine resin, polyethylene, polypropylene, ethylene-propylene terpolymer, olefinic ionomer as additives. In addition, an antioxidant and an ultraviolet absorber may be blended as necessary within a range not departing from the scope of the present invention.

  When using a fluorescent brightening agent, the concentration relative to the polyester composition is preferably 0.005 to 0.5% by weight, more preferably 0.01 to 0.3% by weight. If it is less than 0.005% by weight, the reflectance in the wavelength region near 350 nm is not sufficient, and the illuminance is not sufficient when the reflector is used. If it exceeds 0.5% by weight, a characteristic color of the fluorescent brightening agent appears, which is not preferable.

As the fluorescent brightening agent, for example, OB-1 (manufactured by Eastman), Uvitex-MD (manufactured by Ciba Geigy), or JP-Conc (manufactured by Nippon Chemical Industry Co., Ltd.) can be used.
Further, if necessary, a coating agent having an antioxidant, an ultraviolet absorber, a fluorescent brightening agent, and the like can be applied to at least one surface of the film.

[Lamination]
The biaxially oriented laminated film of the present invention is a laminated film including a two-layer constitution of A layer / B layer, and may be a two-layer constitution of A layer / B layer, for example, B layer / A layer / B It may be a three-layer structure of layers. In particular, a three-layer structure of B layer / A layer / B layer is preferable because good reflection characteristics can be obtained.

  The delamination strength between the A layer and the B layer is 200 g or more, preferably 220 g or more, more preferably 240 g or more, and most preferably 250 g or more. If it is less than 200 g, scratches on the film will be the starting point, and it will be easy to peel off. The upper limit of the delamination strength is not specifically defined, but will be 1000 g at most. This is because production of a film exceeding 1000 g is extremely difficult in consideration of adhesion between layers.

  Moreover, in order to provide other functions to one side or both sides of the film, a laminate in which other layers are further laminated may be used. Examples of other layers herein include a transparent polyester resin layer, a metal thin film, a hard coat layer, and an ink receiving layer.

[Production method]
An example of the method for producing the film of the present invention will be described. A laminated unstretched sheet is produced by a simultaneous multilayer extrusion method using a feed block from a polymer melted from a die. That is, the polymer melt for forming the A layer and the polymer melt for forming the B layer are laminated to form, for example, B layer / A layer / B layer using a feed block, and developed on a die and extruded. carry out. At this time, the polymer laminated by the feed block maintains the laminated form. A multi-manifold die can also be used to form a film, but it is more preferable to use a feed block in terms of increasing the peel strength.

  The unstretched sheet extruded from the die is cooled and solidified by a casting drum to form an unstretched film. This unstretched film is heated by roll heating, infrared heating or the like, and stretched in the longitudinal direction to obtain a longitudinally stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The stretching temperature is preferably a temperature equal to or higher than the glass transition point (Tg) of the polyester, and more preferably a temperature higher by Tg to 70 ° C. The draw ratio is preferably 2.5 to 4.0 times, more preferably 2.8 to both the longitudinal direction and the direction orthogonal to the longitudinal direction (hereinafter referred to as the transverse direction), although it depends on the required characteristics of the application. 3.9 times. If it is less than 2.5 times, the thickness unevenness of the film is deteriorated, and if it exceeds 4.0 times, breakage tends to occur during film formation, which is not preferable.

  The film after longitudinal stretching is subsequently subjected to lateral stretching, heat setting, and thermal relaxation to form a biaxially oriented film. These treatments are performed while the film is running. The transverse stretching process starts from a temperature higher than the glass transition point (Tg) of the polyester. And it is performed while raising the temperature to (5 to 70) ° C. higher than Tg. Although the temperature rise in the transverse stretching process may be continuous or stepwise (sequential), the temperature is usually raised sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone. The transverse stretching ratio is preferably 2.5 to 4.5 times, more preferably 2.8 to 3.9 times, although it depends on the required characteristics of this application. If the thickness is less than 2.5 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained.

  The film after transverse stretching is preferably heat treated at (Tm-10) to (Tm-100) ° C. with a constant width or a width reduction of 10% or less while lowering both ends to reduce the thermal shrinkage. When the temperature is higher than this, the flatness of the film is deteriorated, and the thickness unevenness becomes large, which is not preferable. On the other hand, if the heat treatment temperature is lower than (Tm-80) ° C., the thermal shrinkage rate may increase. Moreover, in order to adjust the thermal shrinkage in the region of (Tm-10) to (Tm-100) ° C. or lower in the process of returning the film temperature to room temperature after heat setting, both ends of the film being held are cut off, The direction take-up speed can be adjusted and relaxed in the vertical direction. As a means for relaxing, the speed of the roll group on the tenter exit side is adjusted. As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, and preferably the speed is reduced by 0.1 to 1.5%, that is, relaxation (hereinafter this value is referred to as the relaxation rate). More preferably, a relaxation rate of 0.2 to 1.2%, more preferably a relaxation rate of 0.3 to 1.0% is performed to adjust the heat shrinkage rate in the longitudinal direction. Further, the width of the film in the horizontal direction can be reduced in the process until both ends are cut off, so that a desired heat shrinkage rate can be obtained.

  The laminated film of the present invention thus obtained has a heat shrinkage rate of 85 ° C. of 0.7% or less, more preferably 0.6% or less, and most preferably 0.5% or less in two orthogonal directions. Is possible. The thickness of the film after biaxial stretching is preferably 25 to 250 μm, more preferably 30 to 220 μm, and still more preferably 40 to 200 μm. If the thickness is 25 μm or less, the reflectance is lowered, and if it exceeds 250 μm, the reflectance cannot be increased even if it is thicker than this, which is not preferable.

  The reflectance of at least one surface of the laminated white polyester film of the present invention is 90% or more, more preferably 92% or more, more preferably 94% or more, with an average reflectance of a wavelength of 400 to 700 nm. If it is less than 90%, sufficient screen brightness cannot be obtained.

Hereinafter, the present invention is described in detail by way of examples.
Each characteristic value was measured by the following method.
(1) Film thickness A film sample was measured for 10-point thickness with an electric micrometer (K-402B manufactured by Anritsu), and the average value was taken as the thickness of the film.

(2) Thickness of each layer A sample was cut into a triangle, fixed in an embedded capsule, and then embedded in an epoxy resin. Then, after embedding the embedded sample with a microtome (ULTRACUT-S), a cross section parallel to the longitudinal direction was made into a thin film section having a thickness of 50 nm, and then observed and photographed with a transmission electron microscope at an acceleration voltage of 100 kv. The thickness of each layer was measured and the average thickness was determined.

(3) an integrating sphere attached to the reflectance spectrophotometer (Shimadzu UV-3101PC), the reflectance when BaS0 ₄ white plate was 100% was measured over 400 to 700 nm. The reflectance was read from the obtained chart at intervals of 2 nm. An average value was determined within the above range.

(4) Stretchability The film was stretched in the longitudinal direction of 2.9 to 3.4 times and in the lateral direction of 3.5 to 3.7 times to observe whether it could be stably formed. Evaluation was made according to the following criteria.
○: Stable film formation for 1 hour or more Δ: Cutting occurs for 10 minutes or more and less than 1 hour.
X: Cutting occurs within 10 minutes, and stable film formation is not possible.

(5) Thermal shrinkage rate The film was held in an oven set at 85 ° C. for 30 minutes in an unstrained state, the distance between the gauge points before and after the heat treatment was measured, and the thermal shrinkage rate (85 ° C. thermal shrinkage rate) according to the following formula: ) Was calculated.
Thermal shrinkage% = ((L0−L) / L0) × 100
L0: Distance between gauge points before heat treatment L: Distance between gauge points after heat treatment

(6) Glass transition point (Tg), melting point (Tm)
Using a differential scanning calorimeter (TA Instruments 2100 DSC), the measurement was performed at a heating rate of 20 m / min.

(7) Interlaminar peel strength of film A strip of film having a length of 150 mm and a width of 20 mm was cut in advance by 50 mm from the layer to be measured, sandwiched between chucks of a tensile tester, and pulled at 100 mm / min. The flat part was read from the chart, and the average value of five measurements was taken as the delamination strength.

(8) Intrinsic viscosity number measurement About 0.1 g of each peeled layer is precisely weighed and dissolved in 25 ml of orthochlorophenol by heating. After standing to cool, fine particles were separated with a centrifuge and measured with a viscometer. Thereafter, the obtained value A was corrected by the following equation.
Intrinsic viscosity number = A / {(100−fine particle concentration%) / 100}

(9) Average particle diameter of fine particles The average particle diameter was measured using an LA-750 particle size analyzer (Particle Size Analyzer) manufactured by HORIBA. The particle diameter corresponding to 50 mass percent was read, and this value was taken as the average particle diameter.

[Examples 1 to 4]
132 parts by weight of dimethyl terephthalate, 18 parts by weight of dimethyl isophthalate (12 mol% with respect to the acid component of the polyester), 96 parts by weight of ethylene glycol, 3.0 parts by weight of diethylene glycol, 0.05 part by weight of manganese acetate, 0. 012 parts by weight were charged into a rectification column and a flask equipped with a distillation condenser, and heated to 150 to 235 ° C. with stirring to distill methanol to conduct a transesterification reaction. After the methanol was distilled off, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of germanium dioxide were added, and the reaction product was transferred to the reactor. Subsequently, while stirring, the pressure in the reactor was gradually reduced to 0.5 mmHg and the temperature was raised to 290 ° C. to carry out a polycondensation reaction. The intrinsic viscosity of the obtained copolyester was as shown in Table 1, the melting point was 224 ° C., and the diethylene glycol component amount was 2.5 wt%. The fine particles shown in Table 1 are added to this polyester resin and supplied to two extruders each heated to 270 ° C., and the A layer polymer and B layer polymer are composed of B layer / A layer / B The layers were merged using a three-layer feed block device so as to form layers, and formed into a sheet shape from a die while maintaining the laminated state. Further, an unstretched film obtained by cooling and solidifying the sheet with a cooling drum having a surface temperature of 25 ° C. was heated at a temperature described in Table 2 to be stretched in the longitudinal direction (longitudinal direction), and cooled with a roll group at 25 ° C. Subsequently, while holding both ends of the longitudinally stretched film with clips, the film was drawn into a tenter and stretched in a direction (lateral direction) perpendicular to the longitudinal direction in an atmosphere heated to 120 ° C. Thereafter, heat setting was performed in the tenter at the temperature shown in Table 2, longitudinal relaxation and lateral width entered in the temperature range shown in Table 2 were performed, and the resultant was cooled to room temperature to obtain a biaxially stretched film. Table 2 shows the physical properties of the obtained film as a reflector substrate.

[Examples 5 to 6]
The same procedure as in Example 1 was carried out except that 0.05 part by weight of manganese acetate was changed to 0.02 part by weight of titanium acetate to give 360 parts by weight of dimethyl terephthalate and 62 parts by weight of dimethyl 2,6-naphthalenedicarboxylate. A copolyester was obtained. The intrinsic viscosity of the obtained copolyester was as shown in Table 1, the melting point was 225 ° C., and the diethylene glycol component amount was 2.5 wt%. Fine particles shown in Table 1 were added to this polyester resin, and films were produced as shown in Table 2 in the same manner as in Example 1.

[Examples 7 to 8]
The same procedure as in Example 5 was performed, except that dimethyl isophthalate was changed to 4 mol% and 15 mol%, respectively, with respect to the acid component of the polyester (here, dimethyl terephthalate and dimethyl isophthalate). The results are shown in Table 1.

[Comparative Example 1]
After transesterification according to a conventional method using 85 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as a catalyst using 0.09 part by weight of calcium acetate, 0.18% by weight as a phosphorus compound with respect to the polymer is obtained. An ethylene glycol solution containing 10% by weight of trimethyl phosphate was added, and then 0.03 part by weight of antimony trioxide was added as a polymerization catalyst. Thereafter, a polycondensation reaction was carried out according to a conventional method under high temperature and reduced pressure to obtain polyethylene terephthalate having intrinsic viscosity shown in Table 1. The melting point was 257 ° C., and the diethylene glycol component amount was 1.2 wt%. The fine particles shown in Table 1 were added to this resin to form layers A and B. It produced on the conditions described in Table 2.

[Comparative Example 2]
It carried out on the conditions shown in Table 1, 2 like the comparative example 1.

[Comparative Examples 3 and 4]
In the same manner as in Comparative Example 1, films were formed under the conditions shown in Tables 1 and 2. Stretching performance was extremely low, and cutting during film formation occurred frequently.

[Comparative Examples 5 and 6]
A copolymer polyester resin was obtained in the same manner as in Example 1 except that 0.04 part by weight of germanium dioxide was changed to 0.04 part by weight of antimony trioxide. Using this resin, the same procedure as in Example 1 was performed as shown in Tables 1 and 2.

[Comparative Example 7]
Using the resin of Comparative Example 1, 14% by weight of calcium carbonate was added as inorganic fine particles as the surface layers (front and back surfaces) of the three-layer film, and polymethylpentene resin, which is an incompatible resin with polyethylene terephthalate, was used as the core layer resin. A film was prepared in the same manner as in Comparative Example 1 by mixing 10% by weight and 1% by weight of polyethylene glycol. As shown in Tables 1 and 2, the reflectance was inferior.

  The biaxially oriented laminated film of the present invention has high light reflectivity, and is most suitable as a reflector for various reflectors, especially for liquid crystal display reflectors, solar cell backsheets, and internally illuminated signboards. Can be used.

  Also, paper replacement, ie cards, labels, stickers, home delivery slips, video printer image paper, ink jet, barcode printer image paper, posters, maps, dust-free paper, display boards, white boards, thermal transfer, offset printing, telephone cards It can also be used as a base material for receiving sheets used for various printing records such as IC cards.

Claims (4)

  Layer A of a polyester composition comprising 45 to 80% by weight of fine particles having an average particle size of 0.1 to 10 μm and 20 to 55% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65, an average particle size adjacent to this layer A laminated film comprising layer B of a polyester composition comprising 0.1 to 15% by weight of fine particles of 0.1 to 10 μm and 85 to 99.9% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65, A biaxially oriented laminated film having a peel strength between A and layer B of 200 g or more.   A layer A of a polyester composition comprising 45 to 80% by weight of fine particles having an average particle size of 0.1 to 10 μm and 20 to 55% by weight of a polyester having an intrinsic viscosity of 0.45 to 0.65 is provided on both sides of this layer. A layer B comprising a polyester composition layer B comprising 0.1 to 15% by weight of fine particles having an average particle size of 0.1 to 10 μm and 85 to 99.9% by weight of polyester having an intrinsic viscosity of 0.45 to 0.65 A biaxially oriented laminated film which is a film and has a peel strength between layer A and layer B of 200 g or more.   The biaxially oriented laminated film according to claim 1 or 2, wherein the polyester of the A layer and / or the B layer is a copolymerized polyethylene terephthalate containing a copolymer component of 4 to 15 mol%.   The biaxially oriented laminated film according to any one of claims 1 to 3, wherein the reflectance is 90% or more.