JP2006327157A - Laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a specular reflection film capable of exhibiting a high and homogeneous light reflection and being reduced in optical deffects, particularly a laminated polyester film being particularly suitable as a substrate of a reflection plate for a surface light source for an LCD, by forming a metallic thin film layer as a specular reflection plane on a flat surface (a surface layer A) of a laminated polyester film of this invention. <P>SOLUTION: The laminated polyester film comprises a layer composition comprising at least three layers of a surface layer (A)/a middle layer (M)/a surface layer (B), wherein the surface layer (A) has an SRz of ≤0.23 μm, the middle layer (M) is a white colored light shielding layer and the surface layer (B) contains particles and has a SRz of >0.23 μm and of ≤2.0 μm, the laminated polyester film has a light transmittance of ≤20% and flaws with a depth of ≥1 μm and a length of ≥3 mm are present on the surface of the surface layer (A) in an amount of ≤100 pieces/m<SP>2</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated polyester film. More specifically, a laminated polyester that can be suitably used as a substrate of a specular reflection film formed with a light reflection layer composed of a metal thin film layer, particularly as a surface light source reflector of a liquid crystal display (hereinafter abbreviated as LCD). Related to film.

  In recent years, the use of liquid crystal screens has been remarkably expanded, and in addition to conventional notebook personal computers, they have been widely used in stationary personal computers, liquid crystal televisions, mobile phone displays, and various game machines. In response to such expanded applications, higher brightness and higher definition of the screen are desired, and improvements such as higher output and increased number of light source lamps have been made even for illumination light sources. In addition, with respect to the reflector used in the light source, the demand for its reflection characteristics has been advanced. In particular, there is an increasing demand for higher brightness in the market.

  In order to meet the demand for higher brightness, it is preferable to use a reflector that uses mirror reflection of a metal thin film layer such as silver or aluminum. However, this method is strong in specular reflection light and can increase the brightness, but hardly reflects light at other angles with respect to the incident angle of light. Therefore, when it is used as a reflector for LCD, a phenomenon occurs that it is bright only when viewed from a certain direction and is dark and difficult to see when viewed from another angle. This phenomenon is generally called high directivity or narrow viewing angle. For this reason, conventionally, a method has been used in which specular reflection light with high directivity is reduced and diffuse reflection light with low directivity is increased.

For example, the following method is disclosed.
(1) A light reflecting layer made of a metal thin film is laminated on the opposite side of the reflective surface of a resin film substrate containing white inorganic particles such as titanium dioxide, and diffuse reflected light is increased by the light scattering effect of the inorganic particles. (For example, refer to Patent Documents 1 to 7)
(2) On the surface of the light reflection layer made of a silver-based metal thin film, a film containing a white pigment or a film in which a resin layer containing a white pigment is laminated is superimposed, and diffuse reflected light is emitted by the light scattering effect of the white pigment. Increasing method (for example, see Patent Documents 8 to 9)
(3) A method in which a light reflecting layer made of a silver thin film layer is formed on a flat surface opposite to a matted surface of a transparent film having a matted surface, and diffuse reflected light is increased by a light scattering effect on the matted surface. (See Patent Document 10)
(4) An ultraviolet absorber and a white pigment as required are used to form a light reflecting layer composed of a silver thin film layer on a matte film having a specific haze, and the ultraviolet absorber or white pigment in the film Method for increasing diffuse reflected light by scattering action of light beam (for example, see Patent Document 11)

(5) A resin layer containing particles is laminated on the surface of the base film, an uneven layer is formed on the surface of the base film, and a light reflecting layer made of silver or an aluminum-based metal thin film is provided on the surface of the uneven film. Method of increasing diffuse reflection light by unevenness of reflection layer (for example, see Patent Documents 12 to 14)
(6) A method of increasing diffuse reflection light by laminating an anchor layer on the surface of a base film, forming a light reflection layer made of a metal vapor deposition layer thereon, and heat-treating under specific conditions (see, for example, Patent Document 15) )
(7) By laminating a metal film on a transmitted light scattering control film composed of a thermoplastic polymer resin oriented film containing a large number of fine pores inside, and by entering light from the film side, depending on the incident direction Method for controlling scattering properties (see, for example, claims of Patent Document 16, paragraphs 0005 and 0060)

JP-A-5-301319 JP-A-10-730 Japanese Patent Laid-Open No. 10-731 Japanese Patent Laid-Open No. 10-732 JP-A-10-67067 JP-A-5-301318 JP-A-10-193494 JP-A-6-15775 JP-A-6-47870 JP-A-8-76112 Japanese Patent Laid-Open No. 7-108643 JP 2001-296410 A JP 2001-350004 A JP 2002-79605 A JP 2000-187207 A Japanese Patent Laid-Open No. 10-332911

  The above method is an effective method for solving the problem that directivity is strong, but the regular reflectance, which is specular reflection light, is reduced, so that the luminance is lowered. For this reason, there is a problem that the demand for high brightness cannot be answered.

  In recent years, the performance of lens films and light diffusing films incorporated in light sources for LCDs has been improved, and the problem that the viewing angle is narrowed even when a reflector with strong specular reflection is used has been improved. In conjunction with this, there has been an increasing demand for reflectors for high brightness using light reflection made of a metal thin film having strong specular reflection light, that is, regular reflection light. However, when the metal thin film layer is formed on the general-purpose film surface as described above, the required characteristics of the market cannot be sufficiently satisfied in the reflected light intensity and the uniformity thereof, and the required characteristics are improved. The development of a base film is strongly desired.

  From this, in order to obtain a film having more excellent specular reflection characteristics, the content of particles in the surface layer of the base film is also reduced, but in this case, the specular reflection characteristics are increased, but the optical defect is It tends to be clearer.

  Furthermore, the optical defect of the film is caused by a scratch on the surface of the base film. If there are minute scratches on the surface of the base film, the reflected light is scattered and the specular reflectivity may be lowered.

  The object of the present invention is to solve the above-described problems in the prior art, by forming a metal thin film layer serving as a reflective surface as a specular reflective layer on the smooth surface (surface layer A) of the laminated film of the present invention. An object of the present invention is to provide a specular reflection film capable of obtaining a high degree of uniform light reflectance, particularly a laminated polyester film which is suitable as a base material for a surface light source reflector for LCD and has few optical defects.

The laminated polyester film of the first invention in the present invention that can solve the above-mentioned problems is a laminate comprising at least three layers of surface layer (A) / intermediate layer (M) / surface layer (B). It is a polyester film, and the surface layer (A) is a smooth polyester resin layer having a three-dimensional ten-point average roughness (SRz) of 0.23 μm or less, and the intermediate layer (M) is hollow or inorganic inside. A white light-shielding layer comprising a polyester resin composition comprising at least one of particles, wherein the surface layer (B) comprises a resin composition comprising particles, and SRz is more than 0.23 μm and not more than 2.0 μm. The laminated polyester film has 100 scratches with a depth of 1 μm or more and a length of 3 mm or more existing on the surface of the surface layer (A). a laminated polyester film, characterized in that at m ² or less.

  In the second invention, the surface layer (B) comprises two layers of a layer (B1) on the intermediate layer (M) side and a slippery coating layer (B2) on the surface side. B2) is a laminated polyester film according to the first invention, which is composed of a resin composition containing particles a having an average particle size of 20 nm or more and less than 150 nm and particles b having an average particle size of 150 nm or more and 600 nm or less. is there.

  A third invention is the laminated polyester film according to the first or second invention, wherein the content of particles inside the surface layer (A) is 50 ppm or less.

  In a fourth aspect of the present invention, the cavity inside the intermediate layer (M) is expressed by stretching a polyester resin composition containing a polyester resin and a thermoplastic resin incompatible with the polyester resin in at least one direction. It is a laminated polyester film according to any one of the first to third inventions, which is a cavity.

A fifth invention is the laminated polyester film according to any one of the first to fourth inventions, wherein an apparent density of the laminated polyester film is 0.60 to 1.35 g / cm ³ .

  A sixth invention is any one of the first to fifth, wherein the total thickness of the laminated polyester film is 100 to 300 μm, and the thicknesses of the surface layers (A) and (B) are 5 to 30 μm, respectively. The laminated polyester film described in the invention.

  7th invention is the static friction coefficient at the time of superimposing the surface layer (A) and surface layer (B) of a lamination | stacking polyester film, It is any one of 1-6 characterized by the above-mentioned. It is a laminated polyester film as described in the invention.

  An eighth invention is the invention according to any one of the first to seventh inventions, wherein the laminated polyester film has a curl value of 1 mm or less after being heat-treated at 110 ° C. for 30 minutes under no load. It is a laminated polyester film of description.

  A ninth invention uses the laminated polyester film according to any one of the first to eighth inventions as a base of a specular reflection film in which a metal thin film layer is laminated on a surface layer A of the film, and the metal thin film layer It is a laminated polyester film for specular reflection film, characterized by being used as a reflection surface.

  Since the laminated polyester film of the present invention can increase the light reflectance by forming a light reflecting layer comprising a metal thin film layer on the surface layer (A) having excellent smoothness, a high-brightness specular reflecting film is obtained. be able to.

  Moreover, since the laminated polyester film of the present invention can utilize the light reflection function of the white light-shielding layer of the intermediate layer (M), the thickness of the metal thin film layer varies when the metal thin film layer is provided on the surface layer (A). Even if there is, non-uniformity of the specular reflection light can be suppressed. Further, even if the thickness of the metal thin film layer is reduced, high reflected light can be obtained, which is economically advantageous. Furthermore, even if there is a pinhole in the metal thin film layer, since the light transmitted through the pinhole is reflected by the white light shielding layer, it is possible to prevent the reflected light from being lowered at the pinhole portion.

  Moreover, in this invention, by setting it as the structure by which the inside of the said intermediate | middle layer (M) was made to contain a cavity, a laminated polyester film can also be reduced in weight besides the light-shielding property provision by a cavity.

  Moreover, since the laminated polyester film of the present invention has an average surface roughness of the surface layer (B) larger than that of the smooth surface layer (A), handling properties (sliding properties, winding properties) during film production and processing And excellent scratch resistance). Therefore, in the film manufacturing process and the processing process for forming the metal thin film layer, the film is easy to handle, and in these processes, the occurrence of scratches on the surface of the surface layer (A) is suppressed, and the flatness Therefore, it is possible to reduce a decrease in light reflectance when a metal thin film layer is formed on the surface layer (A). In addition, the laminated polyester film of the present invention is suppressed in curling due to heating and is excellent in handleability.

  In addition, the laminated polyester of the present invention can prevent the surface layer (A) from being scratched, thereby preventing a decrease in specular reflectivity at the place where the scratch exists, and preventing optical defects at the display portion of the LCD. .

(Laminated polyester film)
The laminated polyester film in the present invention is a laminated polyester film having a layer structure of at least three layers of surface layer (A) / intermediate layer (M) / surface layer (B), and the surface layer (A) is three-dimensional. It is a smooth polyester resin layer having a ten-point average roughness (SRz) of 0.23 μm or less, and the intermediate layer (M) is made of a polyester resin composition containing at least one of a cavity or inorganic particles therein. It is a white light-shielding layer, the surface layer (B) is made of a polyester resin composition containing particles, and is an easy-slip layer having an SRz of more than 0.23 μm and not more than 2.0 μm, and the laminated polyester film is a light beam It is important that the transmittance is 20% or less. A typical layer structure of an embodiment of the present invention is shown in FIG. Further, as another embodiment, FIG. 2 shows a layer structure in the case where the surface layer (B) has two layers.

  The laminated polyester film of the present invention preferably has a total thickness of 100 to 300 μm. The lower limit of the thickness is more preferably 150 μm and particularly preferably 170 μm. On the other hand, the upper limit of the thickness is more preferably 250 μm. If the thickness of the laminated film is less than 100 μm, the film becomes weak and, for example, when incorporated in a final product such as an LCD as a light reflecting plate, the handling property tends to be lowered. On the other hand, when the thickness of the laminated film exceeds 300 μm, it is economically disadvantageous from the viewpoint of productivity. In addition, the thickness of the base material currently used for the reflecting plate generally used for LCD is 188 micrometers now.

  The polyester constituting the surface layer (A), intermediate layer (M), and surface layer (B) of the laminated polyester film of the present invention is an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid or an ester thereof and ethylene. It is a polyester produced by polycondensation with glycols such as glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, and neopentyl glycol. In addition to the direct weight method in which an aromatic dicarboxylic acid and a glycol are directly reacted, these polyesters can be transesterified by an alkyl ester of an aromatic dicarboxylic acid and a glycol and then subjected to a polycondensation, or an aromatic method. It can be produced by a method such as polycondensation of diglycol ester of dicarboxylic acid.

  Typical examples of the polyester include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. The polyester may be a homopolymer or a copolymer of a third component. Among these polyesters, a polyester having an ethylene terephthalate unit, a trimethylene terephthalate unit, or an ethylene-2,6-naphthalate unit of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable. The polyester constituting each layer may be the same type or different types, but the same type is preferable from the viewpoint of curling suppression and economy.

  The laminated polyester film of the present invention is preferably a biaxially oriented polyester film from the viewpoint of mechanical strength and thermal dimensional stability.

When the laminated polyester film of the present invention is implemented by a method in which the intermediate layer (M) contains cavities, a white polyester film that does not contain cavities caused by a thermoplastic resin incompatible with the polyester resin, As compared with the transparent polyester film, there is a problem that the occurrence of curl curl is large. In particular, since the laminated polyester film of the present invention has a large film thickness, curling is likely to occur and countermeasures are required.
Because, in the production of a thick biaxially stretched film, the unstretched film becomes very thick first, so the cooling on the cooling roll is clearly different between the cooling surface and the opposite side. The resulting structure will be different on the front and back of the film. Furthermore, since it is a void-containing polyester film containing fine cavities inside, the size, shape and volume fraction of the cavities easily change over the thickness direction of the film, so the physical properties and structure of the film front and back are the same. Such films are extremely difficult to manufacture.

Therefore, in the present invention, it is preferable that the curled value after heat-treating the laminated polyester film at 110 ° C. for 30 minutes in an unloaded state is 1 mm or less. 0.9 mm or less is more preferable, and 0.8 mm or less is more preferable.
When the curl value exceeds 1 mm, for example, handling properties during work under no tension when incorporated into a final product as a light reflecting plate or the like is not preferable.

  As a technique for suppressing curling, (1) a method for suppressing the occurrence of curling by resisting internal strain by reducing the volume fraction of the cavities and suppressing the size of each cavity, and (2) film (3) In order to control the curl caused by the structural difference between the front and back of the film applied in each step starting from the difference in crystallinity in the film thickness direction due to the cooling difference during extrusion. In addition, a method of positively generating a structural difference between the front and back of the film and complementing the necessary structural difference to bring the curl value close to zero is preferable.

  Specifically, the degree of orientation of the film front and back is controlled independently by setting the temperature or heat quantity of the film front and back to different values in the stretching process and heat setting process such as longitudinal stretching and lateral stretching, and the structure of the film front and back By adopting conditions that balance the physical properties, zero curl film formation is realized.

  In addition, as a basic requirement for stable production in a state where the curl is low over the entire width, it is also important to form cavities with little change in the film thickness direction by a stretching formulation with little thickness unevenness.

  More specifically, for the longitudinal curl immediately after film formation, the structural difference between the front and back of the film during longitudinal stretching is controlled, and the lateral curl is controlled by controlling the structural difference between the front and back of the film during lateral stretching and heat setting. It is preferable to create an internal strain in the opposite direction and balance the internal strain due to the structural difference between the front and back of the film, which is inevitably generated, and suppress curling.

  Moreover, as a curling generation suppression method, it is also effective to make the surface layers (A) and (B) of the laminated polyester film have the same thickness.

(Intermediate layer M)
An intermediate | middle layer (M) is a white light shielding layer comprised from the resin composition formed by containing at least one of a cavity or an inorganic particle in a polyester resin, and since the light transmittance in a laminated polyester film shall be 20% or less Is an indispensable layer. In the present invention, when the intermediate layer (M) is provided with a metal thin film layer on the surface layer (A), even if the thickness of the metal thin film layer varies, there is little variation in reflectance at any location, and It is provided in order to maintain a high reflectance. That is, it is a layer having a function of complementing a decrease in reflectance due to non-uniform thickness of the metal thin film layer.

  In order to improve the light-shielding property, it is effective to contain many fine cavities in the intermediate layer (M) or to contain inorganic particles. The method of containing a large number of fine cavities is advantageous in that light-shielding properties are imparted and the laminated polyester film can be reduced in weight. Further, by using the fine cavities and the inorganic particles in combination, the light shielding property can be further improved. As an intermediate | middle layer (M), either embodiment of the polyester layer containing a fine cavity or a polyester layer containing an inorganic particle and a fine cavity is more preferable from the point of light-shielding property and lightweight.

  As the inorganic particles, white pigments composed of titanium oxide, calcium carbonate, barium sulfate and a composite thereof are preferable. It is preferable to contain 1-25 mass% of these inorganic particles with respect to the resin composition of the intermediate layer (M). If the content of inorganic particles is excessively increased to further improve the light shielding property, breakage occurs frequently during film production, and stable production at an industrial level cannot be performed.

  As a method for containing a cavity, (1) a method in which a foaming agent is contained and foamed by heat at the time of extrusion or film formation, or foamed by chemical decomposition, (2) a gas such as carbon dioxide gas at the time of extrusion or after extrusion, or A method in which a vaporizable substance is added and foamed, (3) a method in which polyester and an incompatible thermoplastic resin are added to the polyester, and after melt extrusion, the film is stretched uniaxially or biaxially; (4) organic or Examples thereof include a method in which inorganic fine particles are added and melt-extrusion is performed and the film is uniaxially or biaxially stretched.

  Among the above-mentioned void-containing methods, the method (3) described above, that is, a method of adding a thermoplastic resin incompatible with polyester and stretching it uniaxially or biaxially after melt extrusion is preferred. Here, the thermoplastic resin incompatible with the polyester resin is not limited in any way, but is a polyolefin resin represented by polypropylene or polymethylpentene, a polystyrene resin, a polyacrylic resin, a polycarbonate resin, Examples include polysulfone resins, cellulose resins, polyphenylene ether resins, and the like.

  These thermoplastic resins incompatible with the polyester resin may be used alone or in combination with a plurality of thermoplastic resins. The content of the thermoplastic resin incompatible with these polyester resins is preferably 3 to 20% by mass, more preferably 5 to 15% by mass with respect to the resin forming the void-containing polyester layer (intermediate layer M). . When the content of the thermoplastic resin incompatible with the polyester resin is less than 3% by mass with respect to the resin forming the void-containing polyester layer, the void content formed inside the film decreases, so that the light shielding property (hiding) ) Is reduced. For this reason, when the metal thin film layer is provided on the surface layer (A), the effect of suppressing the variation in reflectance due to the thickness fluctuation of the metal thin film layer tends to be insufficient. In addition, lightweight features are indispensable. On the other hand, when the content of the incompatible thermoplastic resin exceeds 20% by mass with respect to the resin forming the void-containing polyester layer (intermediate layer M), it is preferable because breakage frequently occurs in the film manufacturing process. Absent. The void content in the intermediate layer (M) of the laminated polyester film of the present invention is preferably 10 to 50% by volume, more preferably 20 to 40% by volume.

  As described above, the intermediate layer (M) used in the present invention is most preferably a method in which a method of forming a cavity by blending an incompatible thermoplastic resin with the above-described polyester resin and a method of blending a white pigment are used in combination. .

  In the laminated polyester film of the present invention, it is important that the light transmittance, which is one of the light-shielding indexes, is 20% or less, preferably 15% or less, particularly preferably 10% or less.

  When the light transmittance of the laminated polyester film exceeds 20%, that is, the light shielding property is inferior, the reflection effect of light transmitted through the metal thin film layer in the white light shielding layer (intermediate layer M) is likely to be reduced. The function of compensating the non-uniformity of the reflected light due to the thickness variation of the white light shielding layer (intermediate layer M) is reduced. In that case, unless the thickness of the metal thin film layer is increased, high reflected light cannot be obtained, which is economically disadvantageous.

  In addition, when the light transmittance exceeds 20%, when used as a light reflecting film in which a metal thin film layer is formed on the laminated polyester film of the present invention, the metal thin film layer is difficult to avoid when forming the metal thin film layer. The light transmitted from the generated pinhole is blocked by the intermediate layer (M), and it becomes difficult to return from the pinhole again.

  In order to make the light transmittance of the laminated polyester film 20% or less, it is preferable that the void content of the intermediate layer (M) and the content of inorganic particles are in the ranges described above. Further, the light transmittance is thickness dependent. That is, even if the intermediate layer (M) is the same resin composition, when the thickness of the intermediate layer (M) is reduced, the light transmittance is increased and the light shielding property is reduced. On the other hand, the thickness of the intermediate layer (M) is reduced. As the thickness increases, the light transmittance decreases and the light shielding property is improved.

  The layer thickness of the laminated polyester film is generally in the range of 100 to 300 μm, and is generally determined by the application and standard when used in the market. On the other hand, the thickness of the surface layer (A) is set to, for example, 5 to 30 μm in a range in which cavities and particles existing in the intermediate layer (M) do not adversely affect the smoothness of the surface layer (A). . Moreover, even if the thickness of the surface layer (A) is too thick, the effect of surface smoothness is saturated. If the thickness of the surface layer (A) needs to be more than 30 μm, a design that can maintain the light-shielding property even if the thickness of the intermediate layer (M) is made thin is designed. M) is important. Specifically, it is preferable to increase the void content of the intermediate layer (M) and the content of inorganic particles within the above ranges. In the case where this is insufficient, for example, a method in which the polyester serving as a cavity developing agent contains particles also in the non-compatible vegetable resin, the intermediate layer (M) as a laminated structure, and a thickness containing a large amount of inorganic particles A thin high-concealment formulation such as a method of laminating a thin layer of the above, a method of using a color pigment other than white, such as carbon black or a blue pigment, may be used.

  Since white reflects light most, the laminated polyester film of the present invention preferably has a whiteness measured according to JIS Z-8722 of 75 or more, more preferably 80 from the surface layer (A) side. That's it. If the whiteness is less than 75, the effect of reflecting the light transmitted through the metal thin film layer by the intermediate layer (M) tends to be reduced.

  In order to set the whiteness of the laminated polyester film to 75 or more, it is also effective to use a fluorescent whitening agent in combination with the above-described means for improving the light shielding property. As a means for improving the light shielding property, (1) a method of setting the void content of the intermediate layer (M) to 10 to 50% by volume, (2) white inorganic particles in the intermediate layer (M), and intermediate layer (M) The method of making it contain 1-25 mass% with respect to the resin composition of (3), combined use of both, etc. are mentioned.

The laminated polyester film of the present invention preferably has an apparent density of 0.6 to 1.35 g / cm ³ . The lower limit of the apparent density is more preferably 0.65 g / cm ³ and particularly preferably 0.7 g / cm ³ from the viewpoint of handleability. The upper limit of the apparent density, in terms of weight reduction, more preferably 1.30 g / cm ^3, particularly preferably 1.20 g / cm ^3. When the apparent density is less than 0.6 g / cm ³ , since the void content is too high, the strength of the laminated polyester film is lowered, the waist is weakened, and the handleability is deteriorated. There is. On the other hand, when the apparent density exceeds 1.3 g / cm ³ , the void content is too low and the effect of weight reduction becomes insufficient.

  In the present invention, the void content in the intermediate layer (M), the type and content of the incompatible thermoplastic resin, and the type and content of the inorganic particles are the light transmittance of the laminated polyester film. According to market requirements such as apparent density and the like, it may be set as appropriate within the range disclosed above.

(Surface layer A)
In this invention, a surface layer (A) is a layer which forms the metal thin film layer used as a reflective surface, when using the laminated polyester film of this invention as a base material of a specular reflection film. This surface layer (A) is excellent in smoothness and is a layer having a function of increasing the reflectance when the metal thin film layer is formed.

  In the laminated polyester film of the present invention, the thickness of the surface layer (A) is preferably 5 to 30 μm. The upper limit of the thickness of the surface layer (A) is more preferably 25 μm, particularly preferably 20 μm. On the other hand, the lower limit of the thickness of the surface layer (A) is more preferably 7 μm, particularly preferably 10 μm. When the thickness of the surface layer (A) is less than 5 μm, the fine cavities and particles contained in the intermediate layer (M) may adversely affect the surface smoothness of the surface layer (A), which is not preferable. On the other hand, when the thickness of the surface layer (A) exceeds 30 μm, the thickness of the intermediate layer (M) must be reduced while maintaining the light shielding property, and the design of the intermediate layer (M) is as described above. It may be necessary to change to a special prescription for concealing thin objects, and the operation becomes complicated.

  In the surface layer (A), it is important that the three-dimensional ten-point average roughness (SRz) is 0.23 μm or less. SRz is preferably 0.21 μm or less, more preferably 0.19 μm or less, and particularly preferably 0.16 μm or less.

  The higher the surface smoothness of the metal thin film layer, the higher the light reflectance. Therefore, it is preferable that the surface layer (A) is as excellent in surface smoothness as possible. When the three-dimensional ten-point average roughness (SRz) exceeds 0.23 μm, the light reflectance, particularly the regular reflectance, on the surface of the metal thin film layer when the metal thin film layer is formed decreases. For example, when such a specular reflection film with inferior regular reflectance is used as a surface light source reflector for LCD, the brightness of the display is lowered. In general, three-dimensional center plane average surface roughness (SRa) is often used as an index of surface smoothness. However, even if the surface has the same SRa, the surface morphology may be completely different, such as when there are a small number of high protrusions or when there are many low protrusions. In the present invention, it has been found that the higher protrusion among the surface protrusions has a greater influence on the light reflectance. In the present invention, for the reasons described above, three-dimensional ten-point average roughness (SRz) is used as an index of surface smoothness.

  The lower limit of SRz of the surface layer (A) is preferably as close to zero as possible from the viewpoint of smoothness. However, in consideration of the extremely high level of technology required for surface smoothing at the extreme level and the measurement accuracy of the measuring device for detecting it, considering the practical light reflectance and stable productivity at the industrial level, A lower limit of SRz is sufficient to be 0.05 μm.

  In the present invention, the method for imparting the above properties is not limited, but it is a preferred embodiment that the surface layer (A) is substantially free of particles. “Substantially free of particles” means, for example, in the case of inorganic particles, a fluorescent X-ray analysis method using a calibration curve prepared in advance from analysis results obtained by other analysis methods such as atomic absorption spectrometry and emission spectrometry. Means the content of 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less when the element attributed to particles is quantified. This is because even if the particles are not actively included in the film, a very small amount of adhering matter, dirt, or foreign matter may be mixed during the production of the raw polymer or the film.

Furthermore, in the present invention, the number of protrusions having a height of 1 μm or more and a maximum diameter of 20 μm or more present on the surface layer (A) is preferably 5 / m ² or less. It is more preferably 4 pieces / m ² or less, and further preferably 3 pieces / m ² or less. Projections having a height of 1 μm or more and a maximum diameter of 20 μm or more existing on the surface of the surface layer (A) are pinholes generated in the metal thin film layer when the metal thin film layer is formed on the surface layer (A). One of the causes. Therefore, when the number of protrusions exceeds 5 / m ² , when the metal thin film layer is formed on the surface layer (A), the frequency of occurrence of pin holes in the metal thin film layer increases, and this pin hole exists. In some cases, the reflected light is lowered at the location where the reflection occurs, and the entire reflected light becomes non-uniform.

In order to set the number of protrusions to 5 / m ² or less, it is preferable not to positively contain particles in the polyester resin forming the surface layer (A). Furthermore, it is preferable to reduce foreign substances that cause pinholes in the metal thin film layer as much as possible. Foreign matter mixed in the surface layer (A) is improved in electrostatic adhesion such as catalyst (polycondensation reaction catalyst, transesterification reaction catalyst) and additive (alkali metal salt / alkaline earth metal salt) in the raw material polyester resin. Agglomerates of additives, heat stabilizers such as phosphoric acid or phosphates, and the like, those resulting from these metal reduction products, contaminants mixed in from the outside, high-melting point organic substances, and the like. Further, dust adhering to the surface layer (A) during film production is also a cause of pinholes in the metal thin film layer.

In the laminated polyester film of the present invention, the total scratches having a depth of 1 μm or more and a length of 3 mm or more present on the surface of the surface layer (A) are preferably 100 pieces / m ² or less. Furthermore, it is more preferably 50 pieces / m ² or less, and further preferably 30 pieces / m ² or less.

Of course, in the laminated polyester film of the present invention, the number of all the scratches present on the surface of the surface layer (A) is most preferably 0 / m ² .

  The polyester resin used in the present invention is a polycondensation method in which a dicarboxylic acid and a glycol are esterified and then a polycondensation reaction, or a transesterification method in which a dicarboxylic acid salt and a glycol are transesterified and then a polycondensation reaction is performed. For example, it is manufactured by a conventionally known method.

  In this polyester resin, a polycondensation catalyst, further a transesterification catalyst, and a thermal stabilizer such as phosphoric acid or phosphate are used as essential components. In addition to these, an appropriate amount of alkali metal salt or alkaline earth metal salt is contained, and by controlling the molar ratio between these metal salt and phosphorus atom, the sheet-like molten polyester resin is electrostatically applied on the rotating cooling roll. An unstretched sheet having a uniform thickness can be stably obtained by adhesion and solidification by the method.

Typical polycondensation catalysts for polyester resins include Sb-based catalysts such as antimony trioxide and antimony glycolate, Ge-based catalysts, and Ti-based catalysts. Of these, antimony trioxide (Sb ₂ O ₃ ) is generally used as the polycondensation catalyst for the polyester resin for film from the viewpoint of transparency, thermal stability and price.

In particular, when Sb ₂ O ₃ is used as a polycondensation catalyst, Sb ₂ O ₃ is reduced to metal Sb during polymerization and / or during production of an unstretched polyester film, and tends to precipitate as an aggregate on the film surface. Since this corresponds to the foreign matter (A), it is preferable to reduce the content of Sb ₂ O ₃ as much as possible within a range in which the polycondensation time is not significantly delayed. In order to make the number of deformed parts as described above within the above range, the Sb ₂ O ₃ content in the polyester resin is 50 to 250 ppm, preferably 60 to 200 ppm, more preferably 70 to 200 ppm in terms of metal Sb. 150 ppm is recommended.

  After completion of the polycondensation, the polyester resin is filtered with a filter made of a filter material such as a sintered stainless steel having a pore size of 7 μm or less (initial filtration efficiency of 95%), or melted from an extruder for pelletization. When extruding the strands in the cooling water, the cooling water is filtered in advance (filter pore diameter: 1 μm or less), and this process is performed in a sealed room, and a foreign material of 1 μm or more existing in the environment is removed with a hepa filter. It is preferable to reduce it.

  Furthermore, also in the production of an unstretched sheet of a polyester resin, which will be described later, in order to remove foreign substances contained in the resin, the microfiltration is performed when the polyester resin is melted. The filter medium used for microfiltration is not particularly limited, but the filter medium of the stainless steel sintered body is a metal Sb produced by reduction of the polymerization catalyst of the polyester resin, Si mixed in at the stage from polymerization to pelletization, This is preferable because it is excellent in the removal performance of the aggregates mainly composed of Ti, Ge, and Cu and high-melting-point organic substances. The filterable particle size of the filter medium is preferably 15 μm or less (initial filtration efficiency 95%). When the particle size exceeds 15 μm, removal of particles having a size of 20 μm or more that needs to be removed may be insufficient. Although productivity may be lowered by performing microfiltration of a molten resin using a filter medium having the filtration performance as described above, it is extremely suitable for obtaining a film laminate having few optical defects.

  About dust adhering to the surface layer (A) at the time of film production, the adhesion of dust is reduced by producing a film in a clean environment in which foreign substances of 1 μm or more existing in the environment are reduced by using a hepa filter. be able to.

(Surface layer B)
In the present invention, the surface layer (B) is a layer having a function of imparting handling properties (sliding property, winding property, scratch resistance, etc.) to the laminated polyester film.

  Further, in the laminated polyester film of the present invention, the thickness of the surface layer (B) is not particularly limited from the function of imparting handling properties, and is, for example, 5 to 30 μm. However, as with the surface layer (A), when the thickness of the surface layer (B) is increased, the thickness of the intermediate layer (M) must be reduced while maintaining the light shielding property. As described above, the design may have to be changed to a prescription for concealing a thin object, and the operation becomes complicated.

  In the present invention, it is important that the three-dimensional ten-point average roughness (SRz) of the surface layer (B) is more than 0.23 μm and not more than 2.0 μm. The lower limit of SRz of the surface layer (B) is more preferably 0.25 μm, particularly preferably 0.27 μm. When the SRz of the surface layer (B) is 0.23 μm or less, the slipperiness between the surface layer (A) and the surface layer (B) is deteriorated when the laminated polyester film is wound, for example, In the manufacturing process of a polyester film and the process of processing a laminated polyester film such as forming a metal thin film layer, the winding property of the laminated polyester film on a roll is likely to deteriorate. In addition, in the film manufacturing process and the film processing process, scratches occur on the surface of the smooth surface layer (A), and the light reflection characteristics on the surface of the metal thin film layer when the metal thin film layer is formed on the surface layer (A) are reduced. It becomes easy.

On the other hand, the upper limit of SRz of the surface layer (B) is more preferably 1.8 μm, and particularly preferably 1.6 μm. When SRz of the surface layer (B) exceeds 2.0 μm, the effect of improving the handleability is saturated and the phenomenon as described in (1) or (2) below is likely to occur, and the surface layer (A) When a metal thin film layer is formed on the surface of the metal thin film layer, the reflective properties of the metal thin film layer surface may be adversely affected.
(1) A protrusion having a high surface layer (B) is scraped off, and the fallen material is transferred to the surface layer (A) in contact with the surface layer (B) when the laminated polyester film is rolled up. 2) When the laminated polyester film is wound into a roll, the coarse protrusions on the surface layer (B) make a mark on the surface layer (A), and the surface of the surface layer (A) becomes rough (hereinafter abbreviated as stamping property). )

  As a method of controlling the SRz of the surface layer (B), a method of incorporating particles that form surface protrusions into the resin forming the surface layer (B) is preferable. When the surface layer (B) is a single layer, the resin constituting the surface layer (B) preferably contains 0.05 to 5% by mass of particles.

  The resin constituting the surface layer (B) is preferably a polyester resin. It may be the same as or different from the polyester resin constituting the surface layer (A). The same is preferred.

  In the present invention, the coefficient of static friction between the surface layer (A) and the surface layer (B) of the laminated polyester film is preferably 0.60 or less, more preferably 0.55 or less, and particularly preferably 0.50. It is as follows. In addition, when the surface layer B is composed of the layer (B1) / easy-sliding composite layer (B2) from the intermediate layer (M) side, and the outermost layer is the easy-sliding composite layer (B2), The static friction coefficient means the static friction coefficient between the surface layer (A) and the easy-sliding multilayer (B2).

  When the static friction coefficient exceeds 0.60, the same problem as in the case where the three-dimensional ten-point average roughness (SRz) of the surface layer (B) is 0.23 μm or less is likely to occur. On the other hand, if the coefficient of static friction is too small, the effect of improving the handling property is reduced, and conversely, winding deviation is easily generated when winding in a roll shape. Therefore, the lower limit of the static friction coefficient is preferably 0.30, more preferably 0.35, and particularly preferably 0.40.

  In order to set the static friction coefficient to 0.60 or less, it is possible to control the SRz of the surface layer (B) to exceed 0.23 μm and to 2.0 μm or less by incorporating particles in the surface layer (B). It is valid. In addition to the method of controlling the surface roughness by the particles, for example, a lubricant comprising an ester derivative of higher fatty acid, an amide derivative or a metal salt in any one of the surface layer (A) and the surface layer (B). When the surface layer (B) is composed of the following laminated film, a method for improving slipperiness by combining a slippery coating layer (B2) with a low-polarity surfactant, etc. Is also possible.

  The particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, lithium fluoride, soju Inorganic particles such as um calcium aluminum silicate, organic salt particles such as terephthalate such as calcium oxalate, calcium, barium, zinc, manganese and magnesium, and vinyl of divinylbenzene, styrene, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid Cross-linked polymer particles consisting of a single monomer or copolymer, polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, thermosetting phenol resin Which inert particles of heat-resistant organic particles, and the like.

  Examples of the method of incorporating the particles in the resin include: (a) Dispersing the particles in a slurry form in a diol which is a polyester constituent component, and adding the particle slurry to a polyester polymerization reaction system; (b) In the melt extrusion process of the polyester film, a method of adding the particle slurry dispersed in the molten polyester resin with a bent twin screw extruder, (B2) a method of kneading the polyester resin and particles in a molten state (d) the polyester resin and particles And a method of kneading the master resin in a molten state.

  In the case of a method of adding to a polymerization reaction system, it is preferable to add a diol slurry of particles to a reaction system having a low melt viscosity before the esterification reaction or transesterification reaction and before the start of the polycondensation reaction. Moreover, when preparing the diol slurry of particles, it is preferable to perform a physical dispersion treatment such as a high-pressure disperser, a bead mill, or ultrasonic dispersion. Furthermore, in order to stabilize the dispersion-treated slurry, it is preferable to use an appropriate chemical dispersion stabilization treatment according to the type of particles used.

  For example, in the case of inorganic oxide particles or crosslinked polymer particles having a carboxyl group on the particle surface, an alkali compound such as sodium hydroxide, potassium hydroxide, or lithium hydroxide is added to the slurry. In addition, reaggregation between particles can be suppressed by electrical repulsion. In the case of calcium carbonate particles, hydroxyapatite particles, etc., it is preferable to add sodium tripolyphosphate or potassium tripolyphosphate to the slurry.

  In addition, when adding the diol slurry of particles to the polymerization reaction system of the polyester, the slurry can be heated to near the boiling point of the diol, or the heat shock (temperature difference between the slurry and the polymerization reaction system) when added to the polymerization reaction system. ) Can be reduced, which is preferable in terms of dispersibility of the particles.

  Further, as another layer configuration for controlling SRz of the outermost layer on the opposite side of the surface layer (A), the surface layer (B) from the intermediate layer (M) side, layer (B1) / slidable coating layer (B2 It is also possible to have a laminated structure consisting of For the layer (B1), the same polyester resin as the surface layer (A) that does not contain particles or a polyester resin having a particle content of less than 100 ppm is used. Furthermore, the slippery coating layer (B2) made of a resin layer containing particles is laminated on the layer (B1) to form the outermost layer and roughen the opposite surface of the surface layer (A). In addition, by using the same raw material as the surface layer (A) as the raw material for the layer (B1), there is an advantage that the coextrusion step when producing the laminated polyester film can be simplified as A / M / A (B1). Is a more preferred embodiment.

When the laminated polyester film has a laminated structure consisting of surface layer (A) / intermediate layer (M) / layer (B1) / slidable coating layer (B2), the laminated portion of A / M / B1 is a biaxially stretched film. The slippery coating layer (B2) is laminated with a coating layer, and the coating amount after final drying is 0.01 to 0.5 g / m ² or the slippery coating layer (B2) It is preferable to use a method of laminating by a coextrusion method and reducing the final thickness to 0.1 to 3 m.

  In the production process of the laminated polyester film, the slippery coating layer (B2) is coated with an application liquid for the slippery coating layer (B2) on an unstretched film or a uniaxially stretched film, dried, and then stretched in at least one direction. The so-called in-line coating method in which the slippery coating layer (B2) is formed by heat treatment is preferable from the viewpoint of film characteristics (sliding property, blocking property, transparency, etc.) and economical efficiency. A typical production example of a laminated polyester film composed of surface layer A / intermediate layer M / layer B1 (A) / slidable coating layer (B2) is shown below. In the following production example, the same raw material as that of the layer A was used as the raw material of the layer B1.

  Using two extruders, a laminated polyester film consisting of three layers in which the layer (A) is laminated on both sides of the intermediate layer (M) is melt-extruded in a sheet form onto a rotating cooling metal roll using a co-extrusion die. Then, it is cooled and solidified by an electrostatic application method to obtain an unstretched polyester sheet.

The obtained unstretched film is stretched 2.5 to 5.0 times in the longitudinal direction (longitudinal direction: traveling direction during production of optical laminated film) with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented film. In addition, the process of performing this uniaxial stretching may be called "longitudinal stretching process".

  In this case, in order to prevent the generation of scratches on the film, (a) the film surface itself or the roll surface, in particular, the roll surface in contact with the film should not generate “defects” that cause scratches, and (b) contact. It is important that the film does not shift in the machine and transverse directions on the surface of the roll to be rolled.

  The above-mentioned “defects” refer to all factors that cause fine scratches on the film by coming into contact with the film, such as scratches, deposits, deposits, and foreign matters formed on the roll surface. Therefore, by eliminating these defects, it is possible to reduce the occurrence of scratches on the film surface. In order to prevent the occurrence of the above defects, for example, the following methods can be employed.

  A method of setting the surface roughness of the roll in contact with the surface layer (A) used at the time of film production to 0.1 μm or less in Ra, and preventing the generation of scratches such as deposits, deposits and foreign matters on the roll surface. Therefore, a method of installing a roll cleaner at the preheating inlet and the cooling roll in the longitudinal stretching process (hereinafter referred to as “MD process”) can be mentioned.

  In addition, there is a method in which the degree of cleanliness in the film production process is class 1000 or less (1000 particles or less of 0.5 μm or more in a volume per cubic foot). It is preferable to use clean air of class 100 or less for the blower cooling device for cooling the roll surface.

  Further, there may be mentioned a method of cleaning the roll by an operation of scraping off defects on the roll using an abrasive before film production. In addition, in order to prevent the film from adsorbing dust or the like due to the generation of static electricity and causing a defect, there is a method of providing a static eliminator so that the charge amount of the film becomes ± 1500 V or less in all steps. The process from the casting of the base film to the tenter described later is a process in which scratches are mainly likely to occur, and laying out this section in a compact manner and reducing the passage time to 5 minutes or less can also contribute to the suppression of the occurrence of defects. .

  About a roll, it can be set as the structure where the fault of a roll surface does not contact a film directly by forming a water film on the roll surface or making it an air floating type roll. Moreover, the adhesion of the defect to a roll surface can be reduced and the defect of a roll surface can be reduced because the oligomer amount which precipitates from a film shall be 1000 ppm or less.

  Furthermore, in the winding process after stretching described below, the surface of the end side in the width direction of the film (lateral direction: the direction perpendicular to the traveling direction during the production of the optical laminated film) is pressed with a roller with a protrusion, In addition to forming a concavo-convex portion in the portion, the film on which the concavo-convex portion is formed is configured to be wound in a roll shape by a winding mechanism, and further, a protrusion on the roller with the protrusion is formed in a tapered shape, By rounding the top of the protrusion and setting the radius of curvature of the top surface to 0.4 mm or less, the film can be prevented from coming into contact with the defect in the film winding device.

  Moreover, as a method for preventing the film from shifting on the roll surface, for example, the following methods can be employed.

  By increasing the adhesion of the film to the roll by reducing the diameter of the roll, using a suction roll, electrostatic adhesion, or using a part nip adhesion device, the occurrence of long scratches can be suppressed. In particular, reducing the diameter of the roll also subdivides the amount of shift of the film and can contribute to the prevention of long scratches. In addition, many of the scratches increase in length and frequency toward the end in the roll width direction, and it is difficult to obtain a scratch-free portion at the end in the roll width direction. By trimming around the center of the direction, a film with few scratches can be obtained.

  As a cause of occurrence of longitudinal scratches or lateral scratches, deformations such as expansion and contraction in the longitudinal direction or the lateral direction of the film can be mentioned, respectively. These film deformations are mainly caused by changes in the film temperature. Therefore, for example, by suppressing the temperature change of the film on the roll surface, the amount of film deformation due to such temperature can be reduced, and the occurrence of vertical scratches and horizontal scratches can be prevented. Specifically, the temperature change of the film per roll is 40 ° C. or less, preferably 30 ° C. or less, more preferably 20 ° C. or less, still more preferably 10 ° C. or less, and particularly preferably 5 ° C. or less. Is recommended.

  Examples of the method for suppressing the temperature change of the film on the roll surface include air cooling between the rolls and water cooling through a water tank. Furthermore, the temperature change of the film on the roll surface per roll can be reduced by increasing the number of rolls. Preferably, the number of rolls in the MD process is 10 or more.

  Further, by setting the relationship between the relative speeds of the plurality of rolls to a speed profile that is closest to the amount of deformation due to the temperature and tension of the film, it is possible to reduce the vertical shift of the film.

  Furthermore, in the coating step of the coating liquid for forming the adhesive property-modified resin layer, which will be described later, the drying condition is completed at the beginning of the dryer section and is cooled to the outlet, whereby the film temperature at the outlet of the dryer is 40 ° C. In the following, film shift due to temperature change can be reduced.

  If the tension during running of the film is too low, the gripping force will be reduced and deviation will occur, and if it is too high, stress deformation will increase and deviation will occur, so the optimum tension range will be 4.9-29.4 MPa. It is preferable to adjust by the driving roll speed and tension adjusting means. Moreover, the shift | offset | difference of the film on a roll surface can be suppressed by making the friction coefficient between the film and roll in the use temperature at the time of manufacture 0.2 or more.

  Furthermore, it is preferable to use a special bearing for the free roll and to set the rotational resistance to 19.6 N or less. For the drive roll, the rotation spots are controlled to 0.01% or less.

  The obtained unstretched polyester sheet is stretched 2.5 to 5.0 times in the longitudinal direction with, for example, a roll heated to 80 to 120 ° C. to obtain a uniaxially stretched film. Furthermore, the edge part of a film is hold | gripped with a clip, for example, it guide | induced to the hot air zone heated at 70-140 degreeC, and is extended | stretched 2.5 to 5.0 times in the width direction after drying. Subsequently, it is guided to a heat treatment zone at 160 to 240 ° C., and heat treatment is carried out for 1 to 60 seconds to complete crystal orientation and obtain a laminated polyester film. At any stage in the film production process, particularly preferably at the stage of the uniaxially stretched film, a coating solution for forming the above-mentioned slippery coating layer (B2) is applied to one side of the laminated polyester film, and The conductive coating layer (B2) is laminated.

  In the present invention, the slippery coating layer (B2) is preferably composed of a resin composition containing particles a having an average particle size of 20 nm to 150 nm and particles b having an average particle size of 150 nm to 600 nm.

  Examples of such particles include (1) calcium carbonate, calcium phosphate, silica, silica-alumina composite oxide particles, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, etc. Inorganic particles, (2) crosslinked polymer particles such as crosslinked polystyrene, crosslinked polymethyl methacrylate, and crosslinked acryl, (3) heat-resistant polymer particles such as silicon resin particles, polyimide particles, and fluorine resin particles, (4 ) Organic particles such as calcium oxalate can be mentioned. Of these, silica particles are most preferred because of their good affinity with polyester resins.

  In the present invention, it is preferable to contain two types of particles (particle a and particle b) having different average particle diameters. The average particle size of the particles a is preferably 20 nm or more and less than 150 nm, and more preferably 30 to 100 nm. If the average particle size of the particles a is less than 20 nm, the slipping property is insufficient. On the other hand, when the average particle size of the particles a is 150 nm or more, the scratch resistance tends to deteriorate.

  In the present invention, in order to improve the balance between slipperiness, scratch resistance, and engraving properties, it is preferable to use particles b having a larger average particle size than particles a in addition to particles a. The average particle size of the particles b is preferably 150 to 600 nm, more preferably 200 to 500 nm. If the average particle size of the particles b is less than 150 nm, the slipping property and the scratch resistance tend to be deteriorated. On the other hand, when the average particle size of the particles b exceeds 600 nm, the wear resistance tends to deteriorate and the stampability tends to increase.

  Furthermore, the difference in the average particle diameter between the particles b and the particles a is preferably 100 nm or more, and particularly preferably 150 nm or more, which is more effective in terms of the balance of slipperiness, scratch resistance, and stampability.

  In the present invention, the three-dimensional ten-point average roughness (SRz) of the slippery coating layer (B2) is more than 0.23 μm and 2.0 μm, like the surface layer (B) in the case of the single layer configuration. It is important that: Thereby, even if the surface layer (A) is smooth, the deterioration of the handling property of the laminated polyester film can be improved. The lower limit of SRz of the slippery coating layer (B2) is more preferably 0.25 μm and particularly preferably 0.27 μm from the viewpoint of handling properties. On the other hand, the upper limit of SRz of the slippery coating layer (B2) has an adverse effect on the surface of the surface layer (A), such as adhesion of fallen substances and transfer marks of coarse protrusions when the laminated polyester film is wound up. From the standpoint, 1.8 μm is more preferable, and 1.6 μm is particularly preferable.

  When the three-dimensional ten-point average surface roughness (SRz) of the slippery coating layer (B2) is 0.23 μm or less, the surface layer (A) and the slippery coating layer are taken up when the laminated polyester film is wound. The slipperiness between (B2) deteriorates. For example, in the process of manufacturing a laminated polyester film such as forming a laminated polyester film or forming a metal thin film layer, the rollability of the laminated polyester film on a roll is reduced. It becomes easy to get worse. In addition, in the film manufacturing process and the film processing process, scratches occur on the surface of the smooth surface layer (A), and the light reflection characteristics on the surface of the metal thin film layer when the metal thin film layer is formed on the surface layer (A) are reduced. It becomes easy.

  On the other hand, when SRz of the slippery coating layer (B2) exceeds 2.0 μm, the effect of improving the handleability is saturated and the slippery coating layer (B2) on the surface of the surface layer (A) is saturated. It becomes easy to give bad influences, such as adhesion of the fallen thing of a coarse protrusion, and the transfer trace of a coarse protrusion. For this reason, when the metal thin film layer is formed on the surface layer (A), the reflection characteristics on the surface of the metal thin film layer may be adversely affected.

  In order to set the three-dimensional ten-point average roughness (SRz) of the slippery coating layer (B2) to more than 0.23 μm and 2.0 μm or less, particles a having an average particle size of 20 nm or more and less than 150 nm in the coating layer The mass ratio (a / b) with the particles b having an average particle size of 150 nm to 600 nm is 3 to 30, and the content of the particles B is 0.1 to 3% by mass with respect to the resin composition of the coating layer. Is preferred. In particular, when the content of the particles b exceeds 3% by mass with respect to the resin composition of the coating layer, the scratch resistance tends to be significantly reduced. Here, the resin composition of a coating layer means the sum total of solid content mass of resin, particle | grains a, and particle | grains b.

  In the present invention, the coating liquid used for forming the coating layer is mainly composed of a solvent, a resin, and particles. As the solvent, either an aqueous solvent or an organic solvent can be used, but an aqueous solvent is preferable from the viewpoint of working environment, environmental protection, productivity, and the like.

The water-soluble or water-dispersible resin used for the slippery coating layer (B2) in the present invention is not limited. Examples thereof include polymers such as polyester polymers, acrylic polymers, and polyurethane polymers, and copolymers of these and other components with other resins such as melamine resins.
Polyester resins consisting of any of the following (i) to (iii) are preferred.
(I) A graft copolymer of an aromatic polyester resin containing 5% by weight or more of a radical polymer composed of at least one monomer containing an acid anhydride having a double bond (ii) An acid value of 200 eq / t or more Acrylic resin or copolymer thereof (excluding (iii))
(Iii) A copolymer of an acrylic resin having an acid value of 200 eq / t or more, containing 5% by weight or more of a radical polymer comprising at least one monomer containing an acid anhydride having a double bond

  The aromatic polyester resin refers to a resin containing 30 mol% or more of an aromatic dicarboxylic acid component in the acid component of polyester. If the aromatic dicarboxylic acid component is less than 30 mol%, the hydrolyzability of the polyester resin becomes remarkable and the water resistance tends to deteriorate.

  The acid value in the acrylic resin is a value obtained by titrating a solid content after drying a resin solution or the like at 80 ° C. under a reduced pressure of 100 Pa for 2 hours with an ethanolic potassium hydroxide solution having a known concentration. It is.

  If the acid value of the acrylic resin is less than 200 eq / t, the dispersibility in an aqueous solvent may be lowered, which is not preferable.

  In order to make the acid value 200 eq / t or more, it is necessary to contain a polar group in the molecule. However, a stable polar group that does not change even when heated, such as sodium sulfonate, is not preferable because it deteriorates the water resistance of the coating layer.

  Examples of the polar group that does not deteriorate the water resistance of the coating layer include amine salts of carboxylic acids that decompose after heating and have a reduced polarity. The amine that can be used is preferably vaporized under the drying conditions of the coating film, and examples thereof include ammonium, diethylamine, and triethylamine.

  More preferably, at least one resin selected from an aromatic polyester resin or an acrylic resin having an acid value of 200 eq / t or more, or two or more copolymers contains an acid anhydride having a double bond. It is to contain 5% by mass or more of a radical polymer composed of at least one monomer. If it is less than 5% by mass, the effect of water resistance tends to be insufficient.

  By introducing the acid anhydride into the resin, a crosslinking reaction can be performed between the resin molecules. That is, the acid anhydride in the resin is converted to carboxylic acid by hydrolysis in the coating solution, and reacts with the acid anhydride or active hydrogen groups of other molecules between molecules due to thermal history during drying and film formation. Thus, ester groups and the like can be generated, and the resin of the coating layer can be cross-linked to exhibit water resistance and heat whitening prevention property.

  Examples of the monomer containing an acid anhydride having a double bond include maleic anhydride, itaconic anhydride, 2,5-norbornene dicarboxylic acid, and tetrahydrophthalic anhydride. The radical polymer may be a copolymer with another polymerizable unsaturated monomer.

  Other polymerizable unsaturated monomers include: (1) fumaric acid, monoethyl fumarate, diethyl fumarate, monoester or diester of fumaric acid such as dibutyl fumarate, (2) maleic acid, monoethyl maleate, malee Monoester or diester of maleic acid such as diethyl acid, dibutyl maleate, (3) itaconic acid, monoester or diester of itaconic acid, (4) maleimide such as phenylmaleimide, (5) styrene, α-methylstyrene, Styrene derivatives such as t-butylstyrene and chloromethylstyrene, (6) vinyltoluene, divinylbenzene, etc. (7) alkyl acrylate, alkyl methacrylate (the alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl group, isobutyl group, t- (8) 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl, and the like. (8) 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl, acryl group, 2-ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group Acrylate, hydroxy-containing acrylic monomer of 2-hydroxypropyl methacrylate, (9) acrylamide, methacrylamide, N-methyl methacrylamide, N-methyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-di Methylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, amide group-containing acrylic monomer of N-phenylacrylamide, (10) N, N-diethylaminoethyl acrylate , N, N-diethylaminoethyl methacrylate amino group-containing acrylic monomer, (11) glycidyl acrylate, glycidyl methacrylate epoxy group-containing acrylic monomer, (12) acrylic acid, methacrylic acid, and salts thereof (sodium salt) , Potassium salts, ammonium salts), and the like, and acrylic monomers containing a carboxyl group or a salt thereof.

  Moreover, in order to further improve the water resistance of the coating layer, it is particularly preferable to add an acid compound when adjusting the coating solution. By adding this acid compound, the acid anhydride and esterification reaction of the carboxylic acid group in the resin can be promoted and the crosslinking of the resin can be improved.

  The addition amount of the acid compound is preferably in the range of 1 to 10% by mass with respect to the resin. Although various compounds can be used as the acid compound, a low-boiling point carboxylic acid that is easily vaporized by heat during film formation, has a small residual amount in the coating layer, and has a small adverse effect at the time of residual is low. preferable. Examples of the low boiling point carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, heptanoic acid and the like.

  In the present invention, when performing a crosslinking reaction using the acid anhydride, it is possible to use a crosslinking agent that does not contain a nitrogen atom or phenols, which suppresses water resistance and discoloration during recovery and reuse. To preferred.

  Examples of the crosslinking agent containing no nitrogen atom or phenol include, for example, orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-oxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, Hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether and polyalkylene glycol diglycidyl ether, trimellitic acid triglycidyl ester, 1,4-diglycidyl Oxybenzene, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol triglycidyl ether, triglycidyl ether of glycerol alkylene oxide adducts, include multifunctional epoxy compounds such as.

  A crosslinking agent containing a nitrogen atom or a phenol is oxidized and decomposed by heat or the like to produce a compound having a conjugated structure centered on a nitrogen atom and an aromatic ring. As a result, coloring becomes remarkable. However, in the present invention, the use of these cross-linking agents is not completely denied, and the cross-linking agents (curing resins) can be used as long as they are within a range where excellent water resistance and discoloration during recovery and reuse can be suppressed. ) Can be used in an appropriate amount depending on the type.

  Examples of the crosslinking agent containing a nitrogen atom include (1) an adduct of urea, melamine, benzoguanamine and the like with formaldehyde, and (2) an alkyl ether compound comprising these adduct and an alcohol having 1 to 6 carbon atoms. (3) a polyfunctional epoxy compound containing a nitrogen atom, (4) a polyfunctional isocyanate compound, (5) a blocked isocyanate compound, (6) a polyfunctional aziridine compound, (7) an oxazoline compound, etc. Can be mentioned.

  Examples of the amino resin described in (2) include methoxylated methylol urea, methoxylated methylol N, N-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated. Examples include methylol benzoguanamine. Among these, methoxylated methylol melamine, butoxylated methylol melamine, methylolated benzoguanamine, and the like are preferable.

  Examples of the polyfunctional epoxy compound containing a nitrogen atom described in (3) include triglycidyl isocyanurate, diglycidyl propylene urea, and the like.

  Examples of the polyfunctional isocyanate compound described in (4) include low-molecular or high-molecular aromatic, aliphatic diisocyanates, and trivalent or higher polyisocyanates.

  Examples of polyisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and trimers of these isocyanate compounds. The

  Further, an excess amount of these isocyanate compounds and low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, or polyester polyols, poly Examples thereof include terminal isocyanate group-containing compounds obtained by reacting polymer active hydrogen compounds such as ether polyols and polyamides.

  The blocked isocyanate described in (5) can be synthesized by subjecting the isocyanate compound and a blocking agent to an addition reaction by a known method.

  Examples of the blocking agent for the isocyanate compound include (a) phenols such as phenol, cresol, xylenol, resorcinol, nitrophenol and chlorophenol, (b) thiophenols such as thiophenol and methylthiophenol, and (B2) acetoxime. Oximes such as methyl etiketooxime and cyclohexanone oxime, (d) alcohols such as methanol, ethanol, propanol and butanol, (e) halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol (F) Tertiary alcohols such as t-butanol and t-pentanol, (g) Lactams such as ε-caprolactam, δ-valerolactam, ν-butyrolactam, β-propyllactam, (h) aroma Amines, (i) imides, (j) active methylene compounds such as acetylacetone, acetoacetate, ethyl malonate, (k) mercaptans, (l) imines, (m), ureas, (n) And diaryl compounds, (o) sodium bisulfite, and the like.

  Examples of the crosslinking agent containing phenols include phenol formaldehyde resins and polyfunctional epoxy compounds containing bisphenol A, which are condensates with formaldehyde such as alkylated phenols and cresols.

  Examples of the phenol formaldehyde resin include alkylated (methyl, ethyl, propyl, isopropyl or butyl) phenol, p-ter-amylphenol, 4,4′-sec-butylidenephenol, p-ter-butylphenol, o-cresol. , M-cresol, p-cresol, p-cyclohexylphenol, 4,4'-isopropylidenephenol, p-nonylphenol, p-octylphenol, 3-pentadecylphenol, phenol, phenyl o-cresol, p-phenylphenol, xylenol And a condensate of phenols with formaldehyde.

  A polyfunctional epoxy compound is mentioned as a crosslinking agent which does not contain a nitrogen atom or phenols. However, since polyfunctional epoxy compounds often use amine-based crosslinking catalysts containing nitrogen atoms, there is a problem that coloring due to the catalyst occurs. Further, although it is possible to suppress coloring by reducing the amount of catalyst or using a catalyst that does not contain an amine or the like, it is preferable because crosslinking is insufficient or a gel-like mixture increases during recovery. Absent.

  Examples of the polyfunctional epoxy compounds described above include diglycidyl ether of bisphenol A and oligomers thereof, diglycidyl ether of hydrogenated bisphenol A and oligomers thereof, orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, and terephthalic acid diester. Glycidyl ester, p-oxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, ethylene glycol diglycidyl ester Ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether And polyalkylene glycol diglycidyl ethers, trimellitic acid triglycidyl ester, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tri And glycidyl ether, triglycidyl ether of glycerol alkylene oxide adduct, and the like.

  As catalysts for polyfunctional epoxy compounds, quaternary ammonium salts such as triethylbenzylammonium chloride and tetramethylammonium chloride, tertiary amines such as benzyldimethylamine, tributylamine and tris (dimethylamino) methylphenol, 2-methyl-4- Imidazole compounds such as ethyl imidazole and 2-methylimidazole, nitrogen-containing heterocyclic compounds such as pyridine and methylpyridine, and catalysts not containing amines include strong bases such as sodium hydroxide and potassium hydroxide, borofluorination Examples thereof include metal compounds such as zinc and tin tetrachloride.

  In addition, when the coating layer is formed using an aqueous coating solution, an anionic coating is used in order to improve the wettability to the substrate film and coat the coating solution uniformly when coating on the surface of the substrate film. It is preferable to add an appropriate amount of a surfactant or a nonionic surfactant to the coating solution.

  In the coating solution, a plurality of other resins may be added to the coating solution in order to improve performance. Further, in the coating solution, inorganic and / or organic particles, antistatic agent, ultraviolet absorber, organic lubricant, in order to impart other functions such as handling property, antistatic property and antibacterial property to the film, Additives such as antibacterial agents and photo-oxidation catalysts can be included.

  When an aqueous solvent is used as a solvent used in the coating solution, alcohols such as ethanol, isopropyl alcohol, and benzyl alcohol may be mixed in a range of less than 50% by mass with respect to the entire coating solution. Furthermore, if it is less than 10 mass%, you may mix in the range which can melt | dissolve organic solvents other than alcohol. However, the total amount of alcohols and other organic solvents in the coating solution is preferably less than 50% by mass.

  If the addition amount of the organic solvent is less than 50% by mass, the drying property is improved during coating and drying, and the appearance of the coating layer is improved as compared with the case of using only water. If the amount is 50% by mass or more, the evaporation rate of the solvent increases, so that the concentration change of the coating solution occurs during coating, the viscosity of the coating solution increases and the coating property decreases. As a result, the appearance defect of the coating layer tends to occur. Furthermore, it is not preferable from the viewpoints of the environment, the health of workers, and the risk of fire.

  Furthermore, removing the foreign matter in the coating solution is effective for improving the scratch resistance and engraving property of the slippery coating layer (B2).

  The filter medium for microfiltration of the coating solution preferably has a filtration particle size (initial filtration efficiency: 95%) of 25 μm or less. When the filtration particle size exceeds 25 μm, removal of coarse aggregates tends to be insufficient. Therefore, coarse agglomerates that could not be removed by filtration spread due to stretching stress in the uniaxial stretching or biaxial stretching process after coating and drying, causing a defect as aggregates of 100 μm or more.

  There is no particular limitation on the type of filter medium for finely filtering the coating solution as long as it has the above performance, and examples thereof include a filament type, a felt type, and a mesh type. The material of the filter medium for finely filtering the coating solution is not particularly limited as long as it has the above performance and does not adversely affect the coating solution, and examples thereof include stainless steel, polyethylene, polypropylene, and nylon.

  The coating solution can be applied by any known method. For example, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method and curtain coating method. These methods can be used alone or in combination.

  The above slippery coating layer (B2) may be applied to the biaxially stretched polyester film substrate (offline coating method) or applied to the unstretched or uniaxially stretched polyester film substrate. The solution may be applied, dried, and further subjected to uniaxial stretching or biaxial stretching, followed by heat setting (inline coating method), but the latter inline coating method is preferred from the viewpoint of performance and economy. The film coated with the coating solution can be led to a tenter for stretching and heat setting, and heated there to form a stable film by a thermal crosslinking reaction.

  In the case of the so-called in-line coating method, after applying the above coating liquid to an unstretched or uniaxially stretched polyester film substrate, drying and stretching, in the drying process after coating, only the solvent component such as water is removed, and the coating layer It is preferable to select a temperature and a time at which the crosslinking reaction does not proceed.

  The drying temperature is preferably 70 to 140 ° C., and the drying time is adjusted according to the solid content concentration and the coating amount of the coating solution, but the product of temperature (° C.) and time (seconds) is 3,000 or less. It is preferable. When the product exceeds 3,000, the coating layer undergoes a crosslinking reaction before stretching, and cracks and the like are likely to occur in the coating layer.

  Moreover, after extending | stretching a coating layer, in the state which fixed the film so that film width length does not change, it is bridge | crosslinking by heat-processing a coating layer for a short time of 0.5 to 1 second at 250-260 degreeC with an infrared heater. It is preferable for promoting the reaction.

  Under the present circumstances, when 1-10 mass% of acid compounds are added with respect to resin in the coating liquid, a crosslinking reaction will be further accelerated | stimulated and a coating layer will become firmer. Therefore, the oligomer which precipitates on the film surface when the film is heated can be blocked by the coating layer, and oligomer deposition on the surface of the coating layer can be suppressed.

  The stretched film is usually subjected to a relaxation treatment of about 2 to 10%, but in the present invention, the coating layer is coated with an infrared heater in a state where the coating layer is less distorted, that is, in a state where the film width is not changed. It is preferable to heat. By adopting such a method, crosslinking in the coating layer is promoted and becomes stronger. If the heating temperature or time is greater than the above conditions, crystallization or dissolution of the film tends to occur. On the other hand, if the one condition is lower than the heating temperature or time, crosslinking of the coating layer tends to be insufficient.

The coating amount after drying of the coating layer on the surface of the finally obtained coating film (solid content weight per unit area of the film) is preferably 0.01 to 0.50 g / m ² , more preferably 0.02 to 0.00. a 40 g / m ^2, particularly preferably 0.05~0.30g / m ^2. When the coating amount after drying is less than 0.01 g / m ² , the adhesiveness is insufficient. When the coating amount exceeds 0.50 g / m ² , it tends to be easily blocked, and the number of foreign matters in the coating layer is also likely to increase.

In addition, it is attached to the film surface that the cleanness in the air in the coating process (number of particles of 0.5 μm or more / ft ³ ) is controlled by a hepafilter so as to be class 100,000 after the unstretched film is formed. It is effective in reducing foreign matter.

(Specular reflection film)
The laminated polyester film of the present invention is designed so that the surface layer (A) has a smooth surface. By providing a metal thin film layer on the surface layer (A) surface, light reflectance, particularly regular reflectance, is provided. Therefore, it can be suitably used as a light reflecting member. Therefore, it is a preferred embodiment that the laminated polyester film of the present invention is provided with a metal thin film layer on the surface layer (A) excellent in surface smoothness. That is, by using the laminated polyester film of the present invention as a substrate of a reflective film, forming a metal thin film layer on the surface layer (A) of the laminated polyester film, and forming a specular reflective film having the metal thin film layer as a reflective surface. The effects of the present invention can be exhibited to the maximum. A typical layer structure is shown in FIG.

  Furthermore, the laminated polyester film of the present invention provides easy slipping to the surface layer (B) which is the opposite surface of the metal thin film layer, and the surface layer (A) from the surface layer (B) during film winding. Suitable surface design has been made to reduce the transfer of dirt and imprints, etc., and these functions are also reflected in the specular reflection film provided with a metal thin film layer, so it can be used suitably as a light reflecting member Can do.

  In the present invention, in order to evaluate the influence of the reflection characteristics on the layer structure of the laminated polyester film, in each example, a metal thin film layer made of aluminum is formed on the surface layer (A) of the laminated polyester film with a thickness of 40 nm. A specular reflection film was produced by vapor deposition. In this invention, it is preferable that the light reflectivity of the metal thin film layer surface in this specular reflection film is 79% or more, More preferably, it is 80% or more, Most preferably, it is 82% or more. By satisfying this characteristic, an LCD with high brightness can be obtained by using it as a surface light source reflector for LCD, for example.

  The metal which comprises the said metal thin film layer is not limited to the aluminum described above, What is necessary is just a metal with little light absorption, for example, silver, gold | metal | money, platinum, stainless steel, and those alloys can also be tried. By using silver or a silver alloy as the metal, a specular reflection film having a better light reflectivity than when aluminum is used can be obtained. What is necessary is just to select a metal material suitably according to a market demand. Further, the metal thin film may contain a small amount of a non-metallic element that does not impair the reflectance. The metal thin film may have a single layer configuration or a stacked configuration. The metal thin film layer is generally formed by vacuum vapor deposition, but can also be formed by sputtering or CVD. The thickness of the metal thin film is preferably in the range of 10 to 200 nm.

  Hereinafter, the present invention will be described in detail by way of examples. The film properties obtained in each example were measured and evaluated by the following methods.

(1) Intrinsic viscosity 0.1 g of the chip sample was precisely weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 6/4 (mass ratio), and measured at 30 ° C. using an Ostwald viscometer. In addition, the measurement was performed 3 times and the average value was calculated | required.

(2) Average particle diameter of particles The particles were observed with a scanning electron microscope (S-510, manufactured by Hitachi, Ltd.), the magnification was appropriately changed according to the size of the particles, and the photographed photographs were enlarged and copied. Next, the circumference of each particle was traced for at least 200 particles randomly selected. The equivalent circle diameters of the particles were measured from these trace images with an image analyzer, and the average value thereof was taken as the average particle diameter.

(3) Average surface roughness The surface of the film was measured using a stylus type three-dimensional surface roughness meter (SE-3AK, manufactured by Kosaka Laboratory Ltd.), a needle radius of 2 μm, a load of 30 mg, and a needle speed of 0. Under the condition of 1 mm / second, the film was measured in the longitudinal direction of the film with a cut-off value of 0.25 mm, measured over a measurement length of 1 mm, divided into 500 points at a 2 μm pitch, and the height of each point was measured with a three-dimensional roughness analyzer ( The product was incorporated into Kosaka Laboratory Ltd., TDA-21). The same operation was performed 150 times continuously at intervals of 2 μm in the width direction of the film, that is, over 0.3 mm in the width direction of the film, and the data was taken into the analyzer. Next, the three-dimensional average surface roughness SRa and the three-dimensional ten-point average roughness SRz were obtained using the analysis device. The unit of SRa and SRz is both μm.
In addition, the measurement was performed 3 times and those average values were employ | adopted.

(4) Number of coarse protrusions of surface layer (A) About 10 pieces of 100 mm × 100 mm film pieces, using a three-dimensional shape measuring device (Ryoka System Co., Ltd. Micromap TYPE500), wavelength 550 nm, WAVE mode, objective lens 10 Under the measurement condition of doubling, the number of coarse projections having a height of 1 μm or more and a maximum diameter of 20 μm or more present on the surface of the surface layer (A) is measured from the direction perpendicular to the surface of the test piece, Converted to “pieces / m ² ”.

(5) Film thickness Using a Millitron thickness meter, a total of 15 points were measured, 5 points per sheet, and the average value was determined.

(6) Layer thickness of laminated film The film was cut using a microtome to obtain a cross section perpendicular to the film surface. A sample obtained by coating the cross section with a platinum / palladium alloy by sputtering was used as an observation sample. The cross section of the film was observed using a scanning electron microscope (manufactured by Hitachi, Ltd., model S-510), and a photograph was taken at an appropriate magnification at which the total thickness of the film became one field of view. From this image, the thickness of each layer was measured using a scale. Measurement was performed on three independently prepared cross-sectional samples, and the average value was taken as the layer thickness of the laminated film.

(7) Light transmittance of laminated film According to JIS-B0601-1982, Poic integrating sphere type H.264 is used. T. T. et al. Measurement was performed using an R meter (manufactured by Nippon Seimitsu Optics). The smaller this value, the higher the light shielding property.

(8) Apparent density of laminated polyester film Four films were cut into 5.0 cm squares and used as samples. Four samples were stacked, and the total thickness was measured at 10 points using a micrometer with four significant figures, and the total value of the stacked thickness was determined. The average value was divided by 4 and rounded to 3 significant figures to obtain an average thickness per sheet (t: μm). The weight (w: g) of the four samples was measured using an automatic upper balance with four significant figures, and the apparent density was determined from the following equation. The apparent density was rounded to 3 significant figures.
Apparent density (g / cm ³ ) = w / (5.0 × 5.0 × t × 10 ⁻⁴ × 4)
= W × 100 / t

(9) Curled value of the laminated polyester film The laminated polyester film was cut into a sheet of 100 mm in the longitudinal direction and 50 mm in the width direction, heat-treated at 110 ° C. for 30 minutes under no load, and then the convex portion of the film was lowered. Measure the vertical distance between the glass plate and the bottom edge of the raised film 4 corners with a ruler in units of 0.5 mm at the minimum scale, and average the measured values at these four locations. Was the curl value. Three samples were prepared and repeatedly measured, and the average value was taken as the curl value.

(10) Scratches on surface layer (A) (i) Detection of scratches Using a three-dimensional shape measuring apparatus (Ryoka Systems Co., Ltd. Micromap TYPE500) for 10 pieces of 100 mm × 100 mm film, wavelength 550 nm, WAVE mode Under the measurement condition of 10 times the objective lens, the defect is observed due to a scratch recognized as a size of 50 μm or more by observing from the direction perpendicular to the surface of the test piece. The evaluation was made for 24 hours after the start of film formation.

(Ii) Measurement of Scratch Size The above test piece is cut into an appropriate size, and a wavelength of 550 nm, WAVE mode, objective lens 10 is measured using a three-dimensional shape measuring device (Ryoka System Co., Ltd. Micromap TYPE500). Under the measurement condition of double, the size of the scratch is measured. When observed from the direction perpendicular to the surface of the test piece, that is, the film surface, the concavity and convexity of the flaws that are close to each other within 50 μm are regarded as the same flaws, and the length and width of the rectangle with the smallest area covering the outermost part of those flaws The length and width of the scratch. Then, the scratch whose longitudinal direction is ± 45 ° or less from the vertical direction (traveling direction in the production of the optical laminated film) is defined as a vertical scratch, and ± 45 from the horizontal direction (orthogonal direction of the vertical direction). Measure the depth (difference between the highest and lowest flaws) and length, with the flaw less than ° as the horizontal flaw. From this result, the number of longitudinal scratches, lateral scratches, and total scratches having a depth of 1 μm or more and a length of 3 mm or more was determined, the unit was converted to “pieces / m ² ”, and the determination was made according to the following criteria.
◎: 30 pieces / m ² or less ○: 31-50 pieces / m ²
Δ: 51 to 100 / m ²
×: 101 pieces / m ² or more

(11) Coefficient of static friction Measured according to JIS K 7125. However, the load cell and the sample were directly connected without using a spring, the mass of the sliding piece was 1.5 kgf, and the test speed was 200 mm / min. Each sample was measured three times, and the average value was taken as the coefficient of static friction.

(12) Optical defects of specular reflection film A specular reflection film was produced by depositing a metal thin film layer made of aluminum with a thickness of 40 nm on the surface layer (A) of the laminated polyester film. Unless otherwise specified, the thickness of the metal thin film layer was 40 nm.
Ten samples were prepared by cutting the above test pieces into a size of 100 mm × 100 mm. With respect to each sample piece, it is left still on a flat table so that the metal vapor deposition surface of the specular reflection film becomes the upper surface. Next, the sample is irradiated with a fluorescent lamp from 2 m above, and is visually observed from the front at a distance of 30 cm from the metal deposition surface, and optical defects due to scratches on the sample film are measured. After the measurement, the sample is rotated 90 ° clockwise, and optical defects are similarly detected. The sum total of the number of optical defects of a total of 10 sample pieces was determined, the unit was converted to “pieces / m ² ”, and the determination was made according to the following criteria.

○: 10 pieces / m ² or less ×: Over 10 pieces / m ²

Example 1
[Production of polyester resin for surface layer (A) and layer (B1)]
When the temperature of the esterification reactor was raised to 200 ° C., a slurry consisting of 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was charged, and antimony trioxide was added as a catalyst while stirring. 0.017 parts by mass and 0.16 parts by mass of triethylamine were added. Next, the temperature was raised by heating, and a pressure esterification reaction was carried out under conditions of a gauge pressure of 0.34 MPa and 240 ° C.

  Thereafter, the inside of the esterification reaction vessel was returned to normal pressure, and 0.071 part by mass of magnesium acetate tetrahydrate and then 0.014 part by mass of trimethyl phosphate were added. Furthermore, the temperature was raised to 260 ° C. over 15 minutes, and 0.012 part by mass of trimethyl phosphate and then 0.0036 part by mass of sodium acetate were added. The obtained esterification reaction product was transferred to a polycondensation reaction can, gradually heated from 260 ° C. to 280 ° C. under reduced pressure, and subjected to a polycondensation reaction at 285 ° C. After the polycondensation reaction, filtration was performed with a stainless steel sintered filter having a pore size of 5 μm (initial filtration efficiency 95%).

  Next, polyethylene terephthalate (PET), which is the polycondensation reaction product, was pelletized in a sealed chamber in which foreign matters having a diameter of 1 μm or more existing in the air were reduced with a hepa filter. Pelletization was performed by a method of extruding molten PET into a cooling water tank from a nozzle of an extruder and cutting the formed strand-like PET resin while flowing cooling water that had been previously filtered (pore size: 1 μm or less). . The obtained PET pellets have an intrinsic viscosity of 0.62 dl / g, an Sb content of 144 ppm, an Mg content of 58 ppm, a P content of 40 ppm, a color L value of 56.2, and a color b value of 1.6. Inert particles and internally precipitated particles were not substantially contained.

[Preparation of Cavity Forming Agent-Containing Master Pellet (I)]
As one of the raw materials for the intermediate layer (M), a 20% by mass polystyrene resin having a melt flow rate of 1.5 (G797N, manufactured by Nippon Polystyrene Co., Ltd.) and a gas phase polymerization polypropylene resin having a melt flow rate of 3.0 (Idemitsu Petrochemical) 20% by mass (F300SP, manufactured by the company) and 60% by mass of polymethylpentene resin (Mitsui Chemicals Co., Ltd .: TPX DX-820) having a melt flow rate of 180 are mixed with pellets and supplied to a twin screw extruder and kneaded sufficiently. The strand was cooled and cut to prepare a cavity-forming agent-containing master pellet (I).

[Preparation of titanium oxide-containing master pellets (b)]
As one of the raw materials for the intermediate layer (M), anatase type titanium dioxide (manufactured by Fuji Titanium Co., Ltd.) having an average viscosity of 49.5% by mass of polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and an average particle size of 0.3 μm (electron microscopic method) (TA-300) 50% by mass and fluorescent whitening agent (manufactured by Eastman Chemical Co., Ltd., OB-1) 0.5% by mass were mixed into a vented twin screw extruder and pre-kneaded, and then melted. The polymer was continuously supplied to a bent type single-screw kneader and kneaded to prepare titanium oxide-containing master pellets (b).

[Preparation of coating solution for forming slippery coating layer (B2)]
(Preparation of copolyester resin)
In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, 345 parts by weight of dimethyl terephthalate, 211 parts by weight of 1,4-butanediol, 270 parts by weight of ethylene glycol, and tetra-n-butyl titanate 0.5 part by mass was charged, and a transesterification reaction was performed from 160 ° C. to 220 ° C. over 4 hours. Next, 14 parts by mass of fumaric acid and 160 parts by mass of sebacic acid were added, and the temperature was raised from 200 ° C. to 220 ° C. over 1 hour to carry out an esterification reaction. Next, the temperature was raised to 255 ° C., the pressure of the reaction system was gradually reduced, and the mixture was reacted for 1 hour 30 minutes under a reduced pressure of 29.3 Pa to obtain a copolyester. The obtained copolyester was pale yellow and transparent and had a weight average molecular weight of 20.000. Moreover, the ratio of the aromatic component by NMR analysis was 70 mol%.

(Preparation of graft modified resin)
A reactor equipped with a stirrer, a thermometer, a reflux device and a quantitative dropping device was charged with 75 parts by mass of copolyester, 56 parts by mass of methyl ethyl ketone and 19 parts by mass of isopropyl alcohol, and heated and stirred at 65 ° C. to dissolve the resin. . After the resin was completely dissolved, 15 parts by weight of maleic anhydride was added to the polyester solution.
Next, a solution prepared by dissolving 10 parts by mass of styrene and 1.5 parts by mass of azobisdimethylvaleronitrile in 12 parts by mass of methyl ethyl ketone was dropped into the polyester solution at 0.1 ml / min, and stirring was further continued for 2 hours. After sampling for analysis from the reaction solution, 5 parts by mass of methanol was added. Next, 300 parts by mass of water and 15 parts by mass of triethylamine were added to the reaction solution and stirred for 1 hour. Thereafter, the reactor internal temperature was raised to 100 ° C., and methyl ethyl ketone, isopropyl alcohol and excess triethylamine were distilled off to obtain a water-dispersible graft resin. This water-dispersible graft resin) was light yellow and transparent. The acid value of this resin was 1400 eq / t.

(Coating solution adjustment)
40 parts by weight of a 25% by weight aqueous dispersion of the water-dispersible graft resin prepared by the above method, 24 parts by weight of water and 36 parts by weight of isopropyl alcohol are mixed, and a 10% by weight aqueous solution of an anionic surfactant. 0.6 parts by mass, 1 part by mass of propionic acid, 20 masses of colloidal silica particles (Nissan Chemical Industries, Snowtex OL, average particle size 40 nm) (particles a) dispersed with a homogenizer in ion-exchanged water Dry silica particles obtained by dispersing 1.8% by weight of an aqueous dispersion with a homogenizer in ion-exchanged water (manufactured by Nippon Aerosil Co., Ltd., Aerosil OX50, average aggregate particle size 200 nm, average primary particle size 40 nm) (particle b) 1.1 parts by mass of a 4% by mass aqueous dispersion was added to prepare a coating solution. The mass ratio of the particles a and the particles b is 8, and the content of the particles b is 0.42% by mass with respect to the resin composition of the coating layer.

[Production of laminated polyester film]
A mixture comprising 7% by mass of the above-mentioned void forming agent-containing master pellets (A), 7% by mass of titanium oxide-containing master pellets (B), and 86% by mass of PET resin having an intrinsic viscosity of 0.62 dl / g is used for the intermediate layer (M). Used as raw material. The surface layer (A) and the polyester resin for the layer (B1) are supplied to two extruders so as to be laminated on both surfaces of the intermediate layer (M), and the surface layer (A) / intermediate layer (M ) / Layer (B1) were joined by a feed block so that the thickness ratio was 8/84/8. Subsequently, it was extruded from a three-layer die onto a cooling drum adjusted to 20 ° C. to produce a three-layer unstretched film having a thickness of 1.6 mm. At the time of extrusion, the polyester resin and the mixture of the polyester resin and the master pellet were previously dried in vacuum and then supplied to the extruder. In addition, regarding the surface layer (A) and the layer (B1), microfiltration is performed using a sintered filter material made of stainless steel having a filterable particle size of 10 μm (initial filtration efficiency 95%) as a filter material for removing foreign matter of molten PET. went. Further, the opposite surface of the cooling drum was cooled by blowing cold air adjusted to 20 ° C.

  The obtained unstretched film is uniformly heated to 65 ° C. using a heating roll, and 3.4 between two pairs of nip rolls (low speed roll: 1 m / min, high speed roll: 3.4 m / min) having different peripheral speeds. Stretched twice. At this time, as an auxiliary heating device for the film, an infrared heater (rated: 40 W / cm) provided with a gold reflective film in the middle part of the nip roll was placed opposite to both sides of the film (a distance of 1 cm from the film surface). Was heated at 18 W / cm and the opposite surface was heated at 12 W / cm. With respect to all rolls used in the production of the film, the surface roughness of the roll was controlled to be 0.1 μm or less by Ra, and roll cleaners were installed at the preheating inlet and the cooling roll in the longitudinal stretching step. The roll diameter in the longitudinal stretching step was 150 mm, and the film was brought into close contact with the roll by employing a suction roll, electrostatic close contact, and part nip contact apparatus.

  Regarding the cleanliness in the film manufacturing process, clean air of class 100 or less was used around the roll, and clean air of class 100 or less was used for the blower cooling device for cooling the anti-roll surface in the casting process. Furthermore, the work which scrapes off the fault of a roll surface using the abrasive | polishing material of the roll was performed before film manufacture. Moreover, the temperature change of the film on a roll was restrained to 10 degrees C or less by the air cooling between rolls. Furthermore, the number of rolls was set to 12 in the longitudinal stretching step, and the temperature change in one roll was reduced.

  In all the steps during film production, a static eliminator was provided so that the charge amount of the film was ± 1500 V or less. The transit time from casting to the tenter entrance is 4 minutes. Set the speed profile so that each roll speed is closest to the amount of deformation due to film temperature and tension. Was suppressed. The drying conditions in the coating step of the coating solution for forming the slippery coating layer were such that the drying was completed at the beginning of the dryer section and cooled toward the outlet, so that the film temperature at the dryer outlet was 29 ° C. Further, the speed of the driving roll and the adjustment with the tension adjusting device were adjusted so that the tension during running of the film was 11.8 MPa.

The coating solution for forming the slippery coating layer (B2) prepared by the above method is subjected to microfiltration with a felt type polypropylene filter medium having a filterable particle size of 10 μm (initial filtration efficiency of 95%), and the uniaxial coating is performed by a reverse roll method. It apply | coated and dried to the anti-cooling roll contact surface side of the extending | stretched PET film. The coating amount at this time was 0.1 g / m ² . Subsequently, after the coating, the edge of the film was held with a clip, guided to a hot air zone heated to 130 ° C. and dried, and then stretched 4.0 times in the width direction. Subsequently, with the film width fixed, the film was heated by an infrared heater at 250 ° C. for 0.6 seconds to obtain a biaxially oriented laminated polyester film having a thickness of 188 μm on which a slippery coating layer was formed. Table 1 shows the characteristic values of the obtained laminated polyester film. The whiteness of the obtained laminated polyester film was 84.

  A metal thin film layer made of aluminum was provided on the surface layer (A) surface, which is the opposite surface of the slippery coating layer (B2) of the laminated polyester film obtained by the above method, by the following method. That is, an aluminum metal piece (10 mg) was fixed to a tungsten filament of a bell jar type vacuum vapor deposition apparatus, and a polyester film to be evaluated was placed 10 cm away from this. After sealing the bell jar, the pressure was reduced to 0.01 Pa using a vacuum pump, and current was applied to the filament to evaporate aluminum. After almost all of the aluminum metal pieces were evaporated by heating for about 15 seconds, the system was cooled down to normal pressure, and the deposited film (specular reflection film) was taken out. The characteristic values of the obtained specular reflection film are shown in Table 1.

Example 2
The laminated polyester film and specular reflection film of Example 2 were obtained in the same manner as Example 1 except for the following conditions. The evaluation results are shown in Table 1.

  There is no static eliminator in all processes during film production, and each roll speed of multiple rolls does not set a speed profile so as to be closest to the amount of deformation due to the temperature and tension of the film. The deviation was not suppressed. The drying conditions in the coating process of the coating solution for forming the slippery coating layer were such that they were dried up to the outlet of the dryer section. Also, no special tension adjustment was performed during film running.

Example 3
In the method of Example 1, the number of extruders used in the production of the laminated polyester film was three, the surface layer (B) had a single film configuration, and 500 ppm of spherical silica particles having an average particle diameter of 2 μm were used as a polyester resin. A laminated polyester film and a specular reflective film of Example 3 were obtained in the same manner as in Example 1 except that the polyethylene terephthalate resin was changed and the coating solution for forming the slippery coating layer (B2) was stopped. . The evaluation results are shown in Table 1.

Comparative Example 1
A laminated polyester film and a specular reflection film of Comparative Example 1 were obtained in the same manner as in Example 1 except for the following conditions. The evaluation results are shown in Table 1.

  For all the rolls used during film production, the surface roughness of the roll was not controlled by Ra to 0.1 μm or less, and no roll cleaner was installed. Furthermore, the roll diameter in the longitudinal stretching step was 300 mm, and no contact equipment such as a suction roll, electrostatic contact, and part nip was used.

  There is no static eliminator in all processes during film production, and each roll speed of multiple rolls does not set a speed profile so as to be closest to the amount of deformation due to the temperature and tension of the film. The deviation was not suppressed. The drying conditions in the coating process of the coating solution for forming the slippery coating layer were such that they were dried up to the outlet of the dryer section. Also, no special tension adjustment was performed during film running.

Comparative Example 2
The laminated polyester film and the specular reflection film of Comparative Example 2 were obtained in the same manner as Comparative Example 1 except for the following conditions. The evaluation results are shown in Table 1.

  The degree of cleanliness in the film production process was set to class 5000, and the roll surface was not scraped off using a roll abrasive prior to film production. Further, the maximum temperature change of the film on the roll was 50 ° C., and the number of rolls was 8 in the longitudinal stretching step.

Comparative Example 3
In the method of Example 1, except that the surface layer (A) and the layer (B1) are both changed to use a polyester resin made of a mixture having the same composition as the intermediate layer (M), the same as in Example 1 A laminated polyester film and a specular reflection film were obtained. The evaluation results are shown in Table 1.

Comparative Example 4
In the method of Example 1, the layer of Comparative Example 4 was laminated in the same manner as in Example 1 except that the raw material of the intermediate layer (M) was changed to use the same polyester resin as that of the surface layer (A) and layer (B1). A polyester film and a specular reflection film were obtained. The evaluation results are shown in Table 1.

Comparative Example 5
In the method of Example 1, an unstretched film extruded from a die so that the layer thickness ratio of the laminated film is surface layer (A) / intermediate layer (M) / surface layer (B) = 8/90/2 The laminated polyester film and the specular reflective film of Comparative Example 5 were the same as Example 1 except that the cooling air was cooled to 20 ° C. on the opposite surface of the cooling drum during cooling by the cooling drum. Got. The evaluation results are shown in Table 1.

Comparative Example 6
In the method of Example 1, a laminated polyester film and a specular reflection film of Comparative Example 6 were obtained in the same manner as in Example 1 except that the application of the coating solution for forming the slippery coating layer (B2) was stopped. The evaluation results are shown in Table 1.

Comparative Example 7
In the method of Example 3, a laminated polyester film and a specular reflection film were obtained in the same manner as in Example 3 except that the same polyester resin as that for forming the surface layer (B) was used as the polyester resin for forming the surface layer (A). Got. The evaluation results are shown in Table 1.

  The laminated polyester film of the present invention is formed on the smooth surface (surface layer A) of the laminated film of the present invention using the metal thin film layer serving as a reflective surface as a mirror reflection layer, and the metal thin film layer is transmitted through the intermediate layer (M). Since it has a function of blocking and reflecting light, a high and uniform light reflectivity can be obtained. Therefore, it can be used for a high-brightness specular reflection film, particularly a surface light source reflector for LCD. . In addition, the laminated film of the present invention reduces the adverse effects such as the occurrence of defects in the metal thin film layer caused by the surface defects of the surface layer A and the decrease in the light reflectivity on the surface of the metal thin film layer. Quality products can be obtained stably. Therefore, the contribution to the industry is great.

It is explanatory drawing which shows the layer structure of the laminated polyester film of this invention. It is explanatory drawing which shows the other layer structure of the laminated polyester film of this invention. It is explanatory drawing which shows the laminated constitution of the specular reflection film using the laminated polyester film of this invention.

Explanation of symbols

1: Laminated polyester film 2: Surface layer (A)
3: Intermediate layer (M)
4: Surface layer (B)
5: Layer (B1)
6: Easy slip coating layer (B2)
7: Metal thin film layer 8: Specular reflection film 9: Light irradiation direction

Claims (9)

A laminated polyester film having a layer structure of at least three layers of surface layer (A) / intermediate layer (M) / surface layer (B), wherein the surface layer (A) has a three-dimensional ten-point average roughness (SRz). Is a smooth polyester resin layer of 0.23 μm or less, and the intermediate layer (M) is a white light-shielding layer made of a polyester resin composition containing at least one of cavities or inorganic particles therein, The surface layer (B) is made of a resin composition containing particles, and is an easy-sliding layer having an SRz of more than 0.23 μm and 2.0 μm or less. The laminated polyester film has a light transmittance of 20% or less. A laminated polyester film characterized in that the total scratches having a depth of 1 μm or more and a length of 3 mm or more existing on the surface of the surface layer (A), which are detected by the following measurement method, are 100 pieces / m ² or less. i Filmstrip ten detection 100 mm × 100 mm scratches (all measured area: 0.1 m ²⁾ for, using the three-dimensional shape measuring apparatus (Ryoka Systems Inc. Micro map TYPE500), wavelength 550 nm, WAVE mode, the objective lens Under the measurement condition of 10 times, a defect due to a scratch that is observed from a direction perpendicular to the surface of the surface layer (A) and recognized as a size of 50 μm or more is detected.
(Ii) Measurement of Scratch Size The above test piece is cut into an appropriate size, and a wavelength of 550 nm, WAVE mode, objective lens 10 is measured using a three-dimensional shape measuring device (Ryoka System Co., Ltd. Micromap TYPE500). Under the measurement condition of double, the size of the scratch is measured. When observed from the direction perpendicular to the surface of the test piece, that is, the film surface, the concavity and convexity of the flaws that are close to each other within 50 μm are regarded as the same flaws, and the length and width of the rectangle with the smallest area covering the outermost part of those flaws The length and width of the scratch. Then, the scratch whose longitudinal direction is ± 45 ° or less from the vertical direction (traveling direction in the production of the optical laminated film) is defined as a vertical scratch, and ± 45 from the horizontal direction (orthogonal direction of the vertical direction). Measure the depth (difference between the highest and lowest flaws) and length, with the flaw less than ° as the horizontal flaw. From this result, the number of longitudinal scratches, lateral scratches, and total scratches having a depth of 1 μm or more and a length of 3 mm or more was determined, and the unit was converted to “pieces / m ² ”.   The surface layer (B) consists of two layers, a layer (B1) on the intermediate layer (M) side and a slippery coating layer (B2) on the surface side, and an average particle diameter of 20 nm in the slippery coating layer (B2). 2. The laminated polyester film according to claim 1, comprising a resin composition containing particles a having a particle diameter of 150 nm or more and less than 150 nm and particles b having an average particle diameter of 150 nm or more and 600 nm or less.   Content of the particle | grains inside the said surface layer (A) is 50 ppm or less, The laminated polyester film of Claim 1 or 2 characterized by the above-mentioned.   The cavity inside the intermediate layer (M) is a cavity developed by stretching a polyester resin and a polyester resin composition containing a thermoplastic resin incompatible with the polyester resin in at least one direction. The laminated polyester film according to any one of claims 1 to 3. The laminated polyester film according to any one of claims 1 to 4, wherein an apparent density of the laminated polyester film is 0.60 to 1.35 g / cm ³ .   The total thickness of the said laminated polyester film is 100-300 micrometers, and the thickness of the surface layers (A) and (B) is 5-30 micrometers, respectively, The laminated polyester in any one of Claims 1-5 characterized by the above-mentioned. the film.   The laminated polyester film according to any one of claims 1 to 6, wherein a coefficient of static friction when the surface layer (A) and the surface layer (B) of the laminated polyester film are superposed is 0.60 or less. .   The laminated polyester film according to any one of claims 1 to 7, wherein the laminated polyester film has a curl value of 1 mm or less after being heat-treated at 110 ° C for 30 minutes in a no-load state.   The laminated polyester film according to any one of claims 1 to 8 is used as a substrate of a specular reflection film in which a metal thin film layer is laminated on a surface layer A of the film, and the metal thin film layer is used as a reflection surface. A laminated polyester film for specular reflection film.

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