TWI477396B - White accumulated polyester film for a reflection sheet - Google Patents

Description

White laminated polyester film for reflective sheet

The present invention relates to a white laminated polyester film for a reflective sheet. More specifically, the present invention relates to a polyester film having a laminated structure, superior reflection characteristics, concealability, and good productivity, and a reflective sheet which can be applied to a backlight device for image display and a lamp mirror. A white laminated polyester film such as a reflection sheet for an illumination device, a reflection sheet for an illumination sign, and a back reflection sheet for a solar cell.

The white polyester film has a uniform and high reflectance, dimensional stability, and low cost, and has been widely used for a reflector of a surface light source device for a liquid crystal display or the like, a reflector, a reflection sheet, and a reflection for an illumination sign. For sheet, solar cell back reflectors, etc. In the method of exhibiting high reflection performance, the following methods are widely used: in the polyester film, for example, inorganic particles containing a large amount of barium sulfate, etc., which are used for the interface between the polyester resin and the particles, and the fine void interface formed by the particles as the core. Method of light reflection (refer to Patent Document 1); a method of reflecting light of a void interface of a fine cavity formed by using an incompatible resin as a core by mixing a resin which is incompatible with a polyester (see Patent Document 2) A method of reflecting light reflected in a void interface formed internally by infiltrating an inert gas in a pressure vessel into a polyester film (see Patent Document 3); and inorganic particles and polyester contained in the polyester film; A method of difference in refractive index of a resin and a difference in refractive index between a fine void and a polyester resin.

In recent years, especially the use of liquid crystal displays has been attracting attention, in addition to In addition to notebook computers, monitors, and portable terminals, LCD TVs are also widely used. In response to this, high-definition and high-definition screens are sought. In response to the high brightness of the screen, the reflective sheet is further required to have high reflectance and high concealment. Therefore, in order to increase the amount of the inorganic particles in the polyester film and the amount of the resin which is incompatible with the polyester, it is important to increase the number of reflective interfaces in the polyester film by using inorganic particles or The incompatible resin in the polyester is increased, and when the biaxial stretching is performed, the film rupture often occurs, which causes a problem of deterioration in productivity, so that high reflectance, high concealability, and film productivity can be combined. For the sake of difficulty.

Therefore, it is attempted to obtain high reflectance and high concealability by using a small amount of titanium dioxide particles having a large refractive index difference from a polyester resin having a basic structure of a film (see Patent Documents 4, 5, and 6). . However, by containing a highly scattering titanium dioxide particle, a portion of the light that is scattered will have a tendency to be lost due to loss, and a larger amount is added. Although the concealing property of the emission reflection sheet is exhibited, the reflection is caused by the loss of light. The rate is lowered, and conversely, in the case of a small amount of addition, there is a problem that the reflectance or the concealing property of the reflection sheet is insufficient, which is difficult. Both the reflectance and the concealability are combined, and the demand for a polyester film which is difficult to be broken and which is excellent in productivity is gradually increased.

Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-330727 Patent Document 2: Japanese Patent Laid-Open No. Hei 04-239540 Patent Document 3: International Patent Publication No. 97/01117 Patent Document 4: Japanese Patent Laid-Open Publication No. 2001-225433 Patent Document 5: Japanese Patent Laid-Open Publication No. 2002-138150 Patent Document 6: Japanese Patent Laid-Open Publication No. 2004-294611

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a white laminated polyester film for a reflective sheet which has high reflectance and high concealability, and which is difficult to produce film breakage and has high productivity. .

In order to solve such a problem, the present invention uses the following technical means. That is, the white laminated polyester film for a reflective sheet of the present invention is attached to at least one side of the polyester layer (B) having voids therein, and a laminated polyester film of the polyester layer (A) is laminated, and the laminate is laminated. The polyester film conforms to all of the following (1) to (5): (1) The thickness of the polyester layer (A) on at least one side is 5 to 15 μm.

(2) The polyester layer (A) contains 3 to 15% by weight of particles having a refractive index of 2.0 or more with respect to the polyester layer (A).

(3) The thickness of the polyester layer (B) is 150 μm or more.

(4) The amount of the particles having a refractive index of 2.0 or more contained in the polyester layer (B) is 2% by weight or less based on the polyester layer (B).

(5) In the polyester layer (B), the polyester layer (B) contains 12 to 25% by weight of a resin which is incompatible with the polyester resin, and/or has a low refractive index of 30 to 50% by weight. Inorganic particles at 2.0.

Further, the void-containing white polyester film of the present invention has the following preferred forms (a) to (j): (a) particles having a refractive index of 2.0 or more contained in the polyester layer (A) are two Titanium oxide particles.

(b) The polyester layer (A) has a thickness of 5 to 10 μm, and the polyester layer (B) has a thickness of 200 to 400 μm.

(c) The titanium dioxide particles contained in the polyester layer (A) are mainly composed of a rutile type.

(d) The titanium dioxide particles contained in the polyester layer (A) are mainly composed of a rutile type produced by a chlorination method.

(e) The resin constituting the polyester layer (A) and the polyester layer (B) has polyethylene terephthalate as a basic structure.

(f) The resin contained in the polyester layer (B) which is incompatible with the polyester resin is polymethylpentene.

(g) The average particle size of the polymethylpentene in the polyester layer (B) is 3 μm or less in the width direction and 2 μm or less in the thickness direction.

(h) The inorganic particles having a refractive index lower than 2.0 contained in the polyester layer (B) are barium sulfate.

(i) providing a coating layer having ultraviolet absorbing energy at least on one side surface.

(j) 0.05 to 10% by weight of a light stabilizer is contained in the polyester layer (A) with respect to the polyester layer (A).

(k) The polyester layer (A) side is used as a light reflecting surface.

(l) A back surface reflection sheet of a backlight for a liquid crystal display having a polyester layer (A) side as a light reflection surface.

According to the present invention, a white laminated polyester for a reflective sheet can be obtained. The film has both high reflectance and high concealability, and film breakage during production is difficult to occur and productivity is high.

Best form for implementing the invention

The present inventors have solved the problem, that is, a white laminated polyester film for a reflective sheet which has high reflectance and high concealability and which is difficult to be produced during film formation and has high productivity. As a result of the investigation, it was found that the identification of a polyester film having a specific structure can solve such a problem in one fell swoop.

In the reflective sheet of the present invention, a white laminated polyester film is attached to at least one side of the inner polyester layer (B) containing voids, and a polyester film containing a polyester layer (A) of titanium oxide particles is laminated. By dividing into a fine void containing a large number of inorganic voids and/or polyester-immiscible resin, in addition to the light reflecting function, the polyester layer (B) exhibiting cushioning or softening function; and having a surface A polyester layer (A) which exhibits a film-forming property or a film strength while maintaining the rigidity of the film, and a single-layer structure cannot be achieved. It is possible to form a film having both high reflectivity and productivity. . Further, the polyester layer (A) and the polyester layer (B) are preferably subjected to a co-extrusion method, and after laminating in a film forming line, they are further stretched in a biaxial direction. In the case of the method of providing the polyester layer (A) by the coating method, it is difficult to stably impart a film thickness necessary for exhibiting sufficient rigidity.

The laminated structure of the white laminated polyester film for a reflecting plate of the present invention is preferably a polyester layer (A) and a polyester layer (B) such as A/B 2 layer or A/B/A 3 layer. Construction, for example, can be made into a laminated polyester layer (A) or A three-layer structure of A/B/C of the polyester layer (C) other than the polyester layer (B), or a more laminated structure. The polyester layer (A) having a surface light diffusing reflection function is preferably disposed on the one-side outermost layer of the laminated structure laminated by the co-extrusion method. Further, in the present invention, the polyester layer (B) containing a plurality of fine voids can be improved in productivity by having a laminated structure, which is nucleated by containing a large number of inorganic particles or incompatible resins for expressing voids. The detachment of the agent may become a problem, and it may damage the part that is in contact with the film forming apparatus (drum, drum, coater, etc.) during a long period of film formation, thereby impairing productivity, and is preferably disposed by coextrusion. The inner layer of the laminated structure.

The components of the polyester resin used in the present invention include the following components. Examples of the dicarboxylic acid component, for example, an aromatic dicarboxylic acid: terephthalic acid, isophthalic acid, sodium 5-sulfonate isophthalate, phthalic acid, biphenyl acid, and ester derivatives thereof; The aliphatic dicarboxylic acid may, for example, be adipic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, dimer acid and ester derivatives thereof; and the alicyclic dicarboxylic acid may be exemplified by 1, 4-cyclohexanedicarboxylic acid and its ester derivative; and a polyfunctional acid is a representative example of trimellitic acid, pyromellitic acid, and an ester derivative. Further, examples of the diol component include "ethylene glycol, propylene glycol, butanediol, neopentyl glycol, pentanediol, hexanediol, octanediol, decanediol, cyclohexanedimethanol, and two. Ethylene glycol, triethylene glycol, polyethylene glycol, 1,4-butanediol, or polyethers such as polyethylene glycol and poly-1,4-butanediol are representative examples. The polyester layer (A) and the polyester layer (B) of the present invention preferably have polyethylene terephthalate as a basic structure, such as mechanical strength, heat resistance, and production cost of the polyester film. It The basic structure means that more than 50% by weight of the polyester resin contained is polyethylene terephthalate.

Further, in the present invention, a copolymerization component may be introduced into the polyethylene terephthalate basic structure. In the method of introducing a copolymerization component, a copolymerization component may be added to a pellet of a polymerized copolymer component in advance during polymerization of a polyester pellet of a raw material, and, for example, a polybutylene terephthalate may be used. A mixture of pellets and polyethylene terephthalate polymerized separately by an ester is supplied to an extruder, and a copolymerization reaction is carried out by a transesterification reaction upon melting. The amount of these copolymerization components is not particularly limited with respect to each component from the respective characteristic surfaces, and is preferably from 1 to 50 mol%, more preferably from 1 to 20 mol%.

Further, isophthalic acid is preferably used as a copolymerization component from the viewpoints of crack resistance, film stability, and production cost between the polyester layer (A) and the polyester layer (B). In addition, since the polyester layer (A) and the polyester layer (B) both contain a common copolymerization component, the crack resistance between the polyester layer (A) and the polyester layer (B) is further improved. Preferably.

The catalyst used for the polycondensation reaction of the polyester resin is preferably, for example, a ruthenium compound, a titanium compound, a ruthenium compound or a manganese compound. These catalysts may be used alone or in combination. Among these catalysts, a titanium compound or a ruthenium compound is preferable because it is difficult to form a metal catalyst agglomerate; and a titanium compound is suitable from the viewpoint of cost. Specifically, as the titanium compound, a main gold such as a titanium alkoxide such as tetrabutyl titanium oxide or tetraisopropoxide titanium oxide or a titanium dioxide-cerium oxide composite oxide can be used. The genus element is a composite oxide composed of titanium and bismuth or a titanium salt or the like. Further, ultrafine titanium oxide such as titanium-cerium composite oxide (trade name: C-94) manufactured by Acordis Co., Ltd. can also be used.

In the present invention, in the polyester layer (A), particles having a refractive index of 2.0 to 5% by weight of 3 to 15% by weight based on the polyester layer (A) are suitably 5 to 10% by weight. When the amount of particles having a refractive index of 2.0 or more is less than 3% by weight, the film having a reflectance and concealability is deteriorated; in the case of more than 15% by weight, the light loss due to scattering is increased, and the reflectance is changed. difference.

In the present invention, the amount of the particles having a refractive index of 2.0 or more contained in the polyester layer (B) is 2% by weight or less, and preferably 1% by weight or less, based on the polyester layer (B). When the amount of the particles having a refractive index of 2.0 or more contained in the polyester layer (B) exceeds 2% by weight, the light scattering loss in the polyester layer (B) which is the main structural component of the laminated film increases, and the reflectance becomes Poor film.

In the present invention, by using particles having a high refractive index, the refractive index difference with the polyester resin constituting the film becomes large, and the light diffusing reflectance at the interface between the particles and the resin becomes strong, so that high can be obtained. Reflectivity and concealment. Examples of the particles having a refractive index of 2.0 or more include titanium dioxide, zinc oxide, zirconium oxide, zinc sulfide, and basic lead carbonate (lead white), and are based on reflection characteristics, concealability, light stability, and production cost. Suitable as titanium dioxide particles. When a particle having a refractive index of less than 2.0 is used, since the difference in refractive index from the polyester resin constituting the film becomes small, the reflection property or concealability is deteriorated.

In the present invention, when titanium dioxide is used as a particle having a refractive index of 2.0 or more, titanium dioxide is preferably titanium dioxide having an anatase type and a rutile type crystal structure. Compared with the anatase type, since the crystal structure of the rutile type is dense and the refractive index is high, the refractive index difference with the polyester resin is increased, so that a high reflection effect at the interface can be obtained. It is preferred to use rutile titanium dioxide.

The method for producing titanium dioxide is mainly exemplified by a sulfuric acid method and a chlorination method. In the sulfuric acid process, the ilmenite is dissolved in concentrated sulfuric acid, and the iron component is separated into iron sulfate, and then the solution is hydrolyzed to precipitate titanium by using titanium as a hydroxide. Next, titanium dioxide can be obtained by burning the hydroxide using a high-temperature rotary kiln or the like. On the other hand, in the chlorination process, chlorine and carbon are reacted at a high temperature of about 1000 ° C by using a rutile type ore as a raw material, and titanium tetrachloride is separated after the formation of titanium tetrachloride. At the same time as high-speed spraying, oxidation is performed to obtain titanium dioxide. Compared with the sulfuric acid process, the titanium dioxide produced by the chlorination process is synthesized by a gas phase reaction involving only gas, so that high-purity titanium dioxide having a small amount of impurities such as vanadium, iron, and manganese can be obtained, because of impurities It is particularly desirable that the absorption loss of the resulting light will be reduced.

The titanium dioxide used in the present invention is preferably subjected to surface treatment in order to suppress the photocatalytic activity of titanium dioxide or to improve the dispersibility in the polyester resin. In order to suppress photocatalytic activity, for example, a method of coating a surface with an inorganic oxide such as ceria or alumina is mentioned. In addition, since the dispersibility is improved, for example, "utilizing 矽" A method of surface treatment of an oxyalkyl compound or a polyol.

The titanium dioxide in the present invention preferably has an average particle diameter of from 0.1 μm to 0.5 μm. The wavelength at which the light-reflecting ability of titanium dioxide can be maximized is about twice the wavelength of the average particle diameter of titanium dioxide. Therefore, the average particle diameter of titanium dioxide is particularly preferably 0.2 μm to 0.4 μm. When the average particle diameter of the titanium oxide is less than 0.1 μm, the titanium dioxide particles tend to be easily aggregated and dispersed, and when the thickness exceeds 0.5 μm, the reflection efficiency in the visible light region tends to decrease.

In addition, the average particle diameter of the titanium dioxide here is observed by the scanning electron microscope (SEM) at a magnification of 20,000 times after the ashing treatment of the laminated film, and the observed 50 particles are observed. The value of the number average particle diameter is determined.

In the present invention, the polyester layer (B) contains voids inside. Since the inside contains many voids, the difference in refractive index between the polyester resin and the void is used to control the scattering loss and the reflectance can be improved. A method of providing a fine void in the polyester layer (B) and exhibiting high reflectance and concealability includes (1) a foaming agent contained in the polyester, and heating by extrusion or film formation. Foaming, or a method of foaming by chemical decomposition to form a void; (2) a method of adding a gas or a vaporizable substance during extrusion of the polyester; (3) by A method in which a polyester-immiscible thermoplastic resin (immiscible resin) is added to a polyester to perform uniaxial or biaxial stretching to cause fine voids; (4) a large amount of inorganic matter in which bubble formation is added A method in which fine particles are substituted for the immiscible resin. In the present invention, based on The use of the incompatible resin of (3) must be used for the comprehensiveness of the film properties, the ease of adjustment of the amount of voids contained in the interior, the ease of formation of voids of finer and uniform size, and even lightness. 4) A method of inorganic fine particles. In the method, the content of the incompatible resin and/or the inorganic particles in the polyester is increased, or the stretching ratio is higher in the step of biaxial stretching, and light is reflected inside the polyester. Interface, so high reflectivity and concealment are possible.

The term "immiscible resin" as used herein refers to a thermoplastic resin other than polyester, and a thermoplastic resin which exhibits incompatibility with polyester is preferably dispersed in a form of particles in a polyester, and is stretched into a film. The effect of forming a void is a large resin. More specifically, the so-called immiscible resin is preferably melted by using a scanning differential heat meter (DSC), dynamic viscoelasticity measurement or the like to determine the melting of the polyester and the incompatible resin by a conventional method. In the case of the latter system, in addition to the glass transition temperature (hereinafter, abbreviated as Tg) corresponding to the polyester, a Tg corresponding to the immiscible resin was observed.

Among the immiscible resins, a crystalline polyolefin resin such as polyethylene, polypropylene, polybutene, polymethylpentene or the like; bicyclo[2,2,1]hept-2-ene, is preferably used. 6-Methylbicyclo[2,2,1]hept-2-ene, 5,6-dimethylbicyclo[2,2,1]hept-2-ene, 1-methylbicyclo[2, 2, 1 Hept-2-ene, 6-ethylbicyclo[2,2,1]hept-2-ene, 6-n-butylbicyclo[2,2,1]hept-2-ene, 6-isobutylbicyclo [2, 2, 1]hept-2-ene, 7-methylbicyclo[2, 2, 1]hept-2-ene, tricyclo[4,3, 0, 1 ^2.5 ]-3-decene, 2 -Methyltricyclo[4,3,0,1 ^2.5 ]-3-decene, 5-methyltricyclo[4,3,0,1 ^2.5 ]-3-decene, tricyclo[4, 4, 0, 1 ^2.5 ]-3-decene, 10-methyltricyclo[4, 4, 0, 1 ^2.5 ]-3-decene, etc., amorphous cyclic olefin resin, polystyrene resin, polyacrylate Resin, polycarbonate resin, polyacrylonitrile resin, polyphenylene sulfide resin, fluorine resin, and the like. These immiscible resins may be homopolymers or copolymers, or even two or more immiscible resins may be used in combination. Among these resins, a polyolefin resin such as polypropylene having a small surface tension or polymethylpentene is preferable, and further, polymethylpentene is preferable. Polymethylpentene has the following characteristics: since the difference in surface tension between the polymethylpentene and the opposite polyester is large, and the melting point is high, the void formation effect of the average addition amount is large, as incompatibility Resin is particularly desirable.

The content of the incompatible resin in the polyester layer (B) of the present invention is from 12 to 25% by weight, suitably from 15 to 20% by weight, based on the entire polyester layer (B). When the content is less than the range, the film having poor reflectance or concealability is formed. On the contrary, when the content is more than the above range, the apparent density of the entire film is excessively lowered, and the film is stretched. Cracking or the like easily occurs, productivity is lowered, or the degree of rigidity of the produced polyester film is low, and it becomes a film which is difficult to handle.

In the present invention, fine voids are formed by using the above-mentioned immiscible resin as a core. The fine void of the present invention can be observed by a scanning electron microscope (SEM) or a transmission electron microscope (TEM) of a cross section (thickness direction) of the polyester layer (B).

In the present invention, in the case where the polyester layer (B) contains an incompatible resin, The voids formed by using the immiscible resin as a core are preferably independent of each other. For the size of the void, the average width of the voids observed along the longitudinal and transverse directions of the film is suitably 3~ 25 μm, more preferably 5 to 20 μm, and the average thickness of the void thickness is desirably 0.3 to 10 μm, more preferably 0.5 to 5 μm. If the average size of the void width is larger than 25 μm and the average thickness of the void thickness is larger than 10 μm, the difference in the surface cushioning property of the laminated film is partially increased, the reflectance becomes uneven, or when the film is formed, The rupture becomes easy to occur. Further, when the average size of the void width is less than 3 μm and the average size of the void thickness is less than 0.3 μm, a sufficient reflectance cannot be obtained. Further, the term "longitudinal direction" refers to the direction in which the film is conveyed in the step of film production, and the direction perpendicular to the longitudinal direction is the width direction. In addition, the average size of the thickness and width of the void disclosed herein is a section which is cut along the longitudinal direction and the width direction after the film is frozen, and a scanning electron microscope (for example, (SEM) S-2100A (Japan Hitachi) is used. Manufactured by (manufacturing) system), observing the photographed cross-section photograph from 4000 times magnification to investigate the presence or absence of a fine void, and observing the size of the void and the size of the immiscible resin from the photograph, measuring the width direction and the thickness direction The length is calculated by reversing the magnification to determine the size of each void and each immiscible resin. The average size of the void size and the incompatible resin is the cross-sectional photograph 50 of the cross-sectional view cut from the longitudinal direction, and the cross-sectional photograph of the cross-section cut along the width direction is 50, and the total of 100 voids and incompatible The resin was obtained in the width direction and the thickness direction, and the average value was obtained. Also, the long side direction, In the case where the width direction is not clear, the measurement is performed by cutting the cross section in two planes perpendicular to the sample.

The size shown in Fig. 1 was measured for the size of the void and the size of the immiscible resin. Further, except that no incompatible resin was observed in the void as shown in Fig. 2 was excluded.

The average size of the incompatible resin in the polyester layer (B) used in the present invention in the width direction is preferably 7 μm or less, more preferably 3 μm or less. Further, the average thickness is 3 μm or less, and more preferably 2 μm or less. When the average size of the incompatible resin in the width direction exceeds 7 μm, or the average size in the thickness direction exceeds 3 μm, the reflectance is lowered, or the film is easily broken at the time of film formation. Although the incompatible resin is preferably slightly dispersed in the polyester resin, in the width direction and the thickness direction, when the average size is less than 0.5 μm, depending on the void formed in the stretching step, there will be a subsequent heat treatment step. It is not good to be blocked and become unsustainable. Further, the above method is also used for the average size and average thickness of the incompatible resin in the width direction.

The method of controlling the average dispersion diameter of the immiscible resin within the above preferred range is not particularly limited. For example, a resin which is incompatible with the above polyester may be a suitable method of adding a dispersant. By adding a dispersing agent, the dispersion diameter of the incompatible resin is reduced, and the voids generated can be further refined by stretching, and as a result, the reflectance of the film, the total light transmittance, and the film stability can be made. improve. As the dispersing agent exhibiting the above effects, an olefin-based polymer or copolymer having a reactive group such as a carboxyl group or an epoxy group or a polyester, a diethylene glycol or a polyalkane can be used. Alcohol, surfactant, and heat-adhesive resin. Of course, these dispersing agents may be used singly or in combination of two or more. Among them, based on the compatibility with the polyester resin of the main structural unit of the polyester layer (B) and the improvement of the dispersibility of the system resin, the polyalkylene glycol and the aliphatic diol component having a carbon number of 2 to 6 and the pair are used. A copolymer resin of a polyester resin composed of phthalic acid is preferred, and in particular, a block copolymer of polyethylene glycol and polybutylene terephthalate is particularly preferred. Such a dispersing agent is used in advance in the polymerization reaction, and the dispersing agent may be used as a copolymerized polyester or may be used as it is.

The amount of the dispersant used in the present invention is suitably from 0.05 to 10% by weight, more preferably from 0.1 to 7% by weight, most preferably from 0.2 to 5% by weight, based on the entire polyester layer (B) which already contains a dispersing agent. When the amount of addition is less than 0.05% by weight, the effect of refining the bubbles will be small. Further, when the amount of addition is more than 10% by weight, on the contrary, the effect of adding an immiscible resin is small, and problems such as a decrease in production stability or an increase in cost are likely to occur.

In the present invention, in the case where the polyester layer (B) contains inorganic particles having a refractive index of less than 2.0, the voids formed by the inorganic particles as the core are preferably independent of each other, and the size of the cavity is along the long side of the film. The average width of the cavity width observed by the section cut in the direction and the width direction is preferably 1 to 25 μm, more preferably 2 to 20 μm, and the average size of the cavity thickness is preferably 0.1 to 10 μn, more preferably 0.3 to 5 μm. . In the case of using inorganic particles, it is difficult to reaggregate after extrusion compared to the incompatible resin, or nuclear heat deformation and voiding rate do not occur due to heat treatment in the film forming step. It is preferable to use a plurality of voids having a small average size, and in the case of using inorganic particles in the opposite direction, since it is difficult to form voids between the polyester resins, it is necessary to contain a large amount of inorganic particles in order to achieve high reflection and high concealment. If the average size of the void width is larger than 25 μm, or the average thickness of the void thickness is larger than 10 μm, the difference in the surface cushioning property of the laminated film may be partially increased, uneven in appearance, or cracked when the film is formed. It becomes easy to happen. Further, if the average size of the void width is less than 1 μm, or the average size of the void thickness is less than 0.3 μm, a sufficient reflectance cannot be obtained. Here, the longitudinal direction referred to herein is a direction in which the film is conveyed in the step of film production, and a direction perpendicular to the longitudinal direction is defined as a width direction. The value was measured by the same method as the above-mentioned void size and the size of the incompatible resin.

In the polyester layer (B) of the present invention, inorganic particles having a refractive index of less than 2.0 are used, and for example, wet and dry cerium oxide, colloidal cerium oxide, calcium carbonate, aluminum silicate, or the like can be used. Calcium phosphate, aluminum oxide, magnesium carbonate, zinc oxide (zinc white), magnesium oxide, barium carbonate, zinc carbonate, barium sulfate, calcium sulfate, mica, talc, clay, kaolin, etc., particularly preferably barium sulfate.

The inorganic particles having a refractive index of less than 2.0 are preferably from 0.05 to 10 μm, more preferably from 0.1 to 3 μm, in the polyester. In the case where the average particle diameter exceeds 10 μm, the film breakage at the time of stretching will occur, or the productivity of the film may be lowered, which is not preferable. In addition, the average particle diameter is 0.05 μm or less, especially since the reflectance on the long wavelength side is lowered. Not good. Here, the average particle diameter is a number average particle diameter. The content of the inorganic particles having a refractive index of less than 2.0 in the present invention is preferably from 30 to 50% by weight, more preferably from 35 to 45% by weight, based on the polyester layer (B). When the content is less than the above range, the film having a reflectance or a total light transmittance is deteriorated. Conversely, when the content is more than the above range, film breakage or the like is likely to occur during stretching. There is a situation of reduced productivity. Further, inorganic particles having a refractive index of less than 2.0 can also be contained in the polyester layer (A).

In the polyester layer (B) of the present invention, both of the above-mentioned inorganic particles having a refractive index of less than 2.0 and a resin incompatible with the polyester may be contained. When an immiscible resin is used as a nucleating agent, it is easy to generate a flat and large cavity, and it is possible to reflect light over a wide range of wavelengths. Since the size of the cavity itself is large, the number of voids tends to decrease. In addition, once the content of the immiscible resin in the polyester is increased, since the dispersion size of the immiscible resin will become large, problems such as cracking in the process will occur, and it is difficult to improve the reflection in the case of seeking further high reflectance. Rate problem. Further, in the case of using inorganic particles having a refractive index of less than 2.0 such as barium sulfate, compared with the incompatible resin, since the content in the polyester film can be increased, many voids having a small size can be formed, although superior. The reflectance on the low-wavelength side is high, but it is difficult to form a large-sized void, and the reflectance on the long-wavelength side is deteriorated. Therefore, it is possible to compensate for the mutual disadvantages by combining large voids caused by the incompatible resin in the polyester and small voids caused by the inorganic particles having a refractive index lower than 2.0.

In the present invention, at least the thickness of the polyester layer (A) on one side is 5~ 15 μm, suitably 5 to 10 μm. When the thickness of the polyester layer (A) is less than 5 μm, the contribution of the diffuse reflection of the surface portion due to the particles having a refractive index of 2.0 or more in the polyester layer (A) is small, and the reflectance becomes small. If the thickness of the polyester layer (A) E which is poor or the rigidity is high, the rigidity of the polyester film is lowered, and the problem of cracking or the like often occurs during production. When the thickness of the polyester layer (A) exceeds 15 μm, the loss due to light diffusion in the polyester layer (A) is increased, and the reflectance is lowered.

In the present invention, the polyester layer (B) has a thickness of 150 μm or more, and is preferably 200 to 400 μm. In the present invention, the light-reflecting property is mainly exhibited by the voids in the polyester layer (B). When the thickness of the polyester layer (B) is less than 150 μm, the reflectance or concealability becomes a film which is deteriorated. Although the upper limit of the thickness of the polyester layer (B) is not particularly limited, the thickness is preferably 500 μm or less from the viewpoint of productivity or cost of the polyester film.

In this manner, a thin layer of polyester layer (B) having a small light diffusion loss exhibits basic light reflection performance, and a thin polyester layer having an efficient reflection ability on the surface side is laminated. (A), the reflection efficiency on the portion close to the surface of the film on which the light is incident is increased, and the light diffusion loss is suppressed, and the effect of increasing the reflectance can be obtained regardless of the lower titanium oxide content. Therefore, it is preferable to use the polyester layer (A) layer side of the white laminated polyester film of the present invention for the light reflecting surface from the viewpoint of reflectance.

Further, the thickness of each polyester layer was measured for the length in the thickness direction of each polyester layer based on the observation photograph obtained by the scanning microscope of the above cross section, and the thickness of each layer was determined by reversing the magnification. Suitable for finding each polyester layer In the cross section cut along the width direction, a total of five cross-sectional photographs arbitrarily selected from mutually different measurement fields were used as the average value. The longitudinal direction and the width direction are not clear, and the cross section in any direction can also be measured.

In the present invention, the apparent density of the entire film is suitably from 0.5 to 1.3 g/cm ³ , more preferably from 0.6 to 1.3 g/cm ³ , particularly preferably from 0.7 to 1.3 g/cm ³ . The apparent density of the laminated white polyester film containing voids is reduced according to the fine voids contained in the polyester layer (B), and is adjusted to an appropriate range. If the apparent density is less than 0.5, the following problems are not preferable: the strength of the film is deteriorated to cause breakage, or wrinkles are generated during the three-dimensional processing, or in the film process, cracking often occurs, and production occurs. Sexual deterioration, etc. On the other hand, when the apparent density exceeds 1.3 g/cm ³ , the amount of voids present in the polyester film is insufficient, and the reflectance is deteriorated. Further, the apparent density in the present invention is that the film is cut into a size of 100 mm × 100 mm, and a measuring instrument having a diameter of 10 mm is placed in a dial gauge, and the thickness of 10 points is measured, and the average value d (μm) of the thickness is calculated. Thereafter, the film was weighed using a direct reading balance until a unit of 10 ^-4 g was read to calculate the value of the weight w (g).

Further, in the present invention, it is preferable that the polyester layer (B) is contained in the polyester layer (B) in an amount of 0.05 to 1.0% by weight of an antioxidant, more preferably 0.1 to 0.5% by weight, to carry out a more stable polymer. Extrusion and film making are possible. From the viewpoint of dispersibility, it is particularly preferable that an antioxidant hindered phenol-based or hindered amine-based antioxidant.

Further, in the present invention, the particles used can also be used as organic particles. Child use. Examples of the organic particles include crosslinked polymer particles, calcium oxalate, acrylic particles, and quinone imine particles.

In addition, the light-resistant agent may be contained in at least one of the polyester layers of the white-coated polyester film for a reflector of the present invention, and may be contained in the polyester layer (A) in an appropriate form. By containing a light stabilizer, the change in color tone of the film due to ultraviolet rays will be prevented. In the present invention, the light stabilizer to be used is not particularly limited as long as it has a range in which other characteristics are not impaired, and it is desired to select a superior heat resistance, and it is compatible with a polyester resin and can be uniformly dispersed. At the same time, it is a resin which is less colored, and a light stabilizer which does not adversely affect the reflection characteristics of a resin and a film. Examples of such a light stabilizer include salicylic acid, benzophenone, benzodiazole, cyanoacrylate, and trisole. An ultraviolet absorber such as a UV absorber or a hindered amine-based ultraviolet absorber. Specifically, for example, salicylic acid-based p-tert-butylphenyl salicylate, p-octylphenyl salicylate; benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, Bis(2-methoxy-4-hydroxy-5-phenylindolephenyl)methane; benzotriazole 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2- (2'-Hydroxy-5'-methylphenyl)benzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-( 2H-benzotriazol-2-yl)phenol]; cyanoacrylate-based ethyl-2-cyano-3,3'-diphenylacrylate; 2-(4,6-diphenyl-1,3,5-three 2-yl)-5-[(hexyl)oxy]phenol or the like.

Further, examples of the ultraviolet stabilizer include a hindered amine-based bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and dimethyl succinate 1-(2- Polyhydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, other examples are: bis(octylphenyl) nickel sulfide and 2,4-di third Phenylphenyl-3',5'-di-p-butyl-4'-hydroxybenzoate and the like. Among these light stabilizers, 2,2',4,4'-tetrahydroxybenzophenone and bis(2-methoxy-4-hydroxy-5-) which are superior in compatibility with polyester are preferably used. Phenylhydrazine phenyl)methane, 2,3'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol And 2-(4,6-diphenyl-1,3,5-three 2-yl)-5-[(hexyl)oxy]phenol. These light stabilizers may be used alone or in combination of two or more.

The content of the light stabilizer in the white laminated polyester film for a reflector of the present invention is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight, most preferably 0.15 to 3% by weight, based on the layer containing the light stabilizer. . When the content of the light stabilizer is less than 0.05% by weight, the light resistance is insufficient, and the change in color tone during long-term storage becomes large; and when the content of the light stabilizer exceeds 10% by weight, it is caused by the light stabilizer The coloring is changed by the color tone of the film, and the reflectance is lowered depending on the light absorbed by the light-resistant agent itself.

In the white laminated polyester film for a reflector of the present invention, by using a light stabilizer and titanium oxide in combination, it is possible to have both excellent light resistance and light reflectivity.

In the present invention, a coating layer having ultraviolet absorbing energy is provided on at least one side, since it is possible to prevent yellowing of the film during long-term use. The ultraviolet absorbing layer may be a single layer or a plurality of layers, in the plural layer In any case, any layer is a layer containing an ultraviolet absorber, and it is preferable that the layer containing the ultraviolet absorber is two or more layers from the viewpoint of maintaining weather resistance. The ultraviolet ray absorbing layer can contain, for example, a benzophenone-based, benzotriazole-based, triazole-based or cyanopropionic acid in a resin component containing a thermoplastic resin, a thermosetting property, or an active-curing resin. An ester, a salicylate, a benzoate or an inorganic ultraviolet shielding agent or the like can be obtained by copolymerization. Among them, a benzotriazole-based ultraviolet absorber is more preferred.

The benzotriazole-based ultraviolet absorbing monomer preferably has a benzotriazole in the basic backbone and is a monomer having an unsaturated double bond, and although it is not particularly limited, a suitable monomer is suitably 2-(2). '-Hydroxy-5'-propenyloxyethylphenyl)-2H-benzotriazole, 2-(2'-hydroxy-5'-methylpropenyloxyethylphenyl)-2H-benzotriene Oxazole, 2-(2'-hydroxy-3'-tert-butyl-5'-propenyloxyethylphenyl)-5-chloro-2H-benzotriazole. Examples of the acrylic monomer and/or oligomer copolymerized with these monomers include alkyl acrylate, alkyl methacrylate, and a monomer having a crosslinkable functional group, for example, having a carboxyl group and a hydroxyl group. A monomer such as an acid group, an acid anhydride group, a sulfonic acid group, a decylamino group, an amine group, a hydroxyl group, an epoxy group or the like.

In the present invention, one or two or more kinds of the acrylic monomers and/or oligomers may be copolymerized at any ratio in a coating layer having a suitable ultraviolet absorbing energy, based on the lamination. From the viewpoint of film hardness, methyl methacrylate or styrene is preferably copolymerized in an amount of 20% by weight or more, more preferably 30% by weight or more based on the acrylic monomer. a copolymerization ratio of a benzotriazole monomer to an acrylic monomer based on durability or From the viewpoint of the adhesion of the base film, the ratio of the benzotriazole-based monomer is 10% by weight or more and 70% by weight or less, and more preferably 20% by weight or more and 65% by weight or less, and more preferably It is 25% by weight or more and 60% by weight or less. The molecular weight of the copolymerized polymer is not particularly limited, and the molecular weight is suitably 5,000 or more, and more preferably 10,000 or more, from the viewpoint of durability of the coating layer. The preparation of the copolymer can be obtained, for example, by a method such as radical polymerization, and is not particularly limited. The copolymer is laminated on a base film as an organic solvent or a water dispersion, and the thickness thereof is usually from 0.5 to 15 μm, preferably from 1 to 10 μm, more preferably from 1 to 5 μm, from the viewpoint of light resistance.

In the coating layer having the ultraviolet absorbing energy in the present invention, organic and/or inorganic particles may be added to the coating layer for the purpose of adjusting the surface glossiness and the like. As the inorganic particles, cerium oxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, calcium carbonate, zeolite, kaolin, talc, or the like can be used, and the organic particles can use an fluorenone compound, crosslinked styrene, crosslinked acrylic acid, and crosslinked melamine. Wait. The particle diameter of the organic and/or inorganic particles is suitably from 0.05 to 15 μm, more preferably from 0.1 to 10 μm. Further, the content is preferably from 5 to 50% by weight, more preferably from 6 to 30% by weight, most preferably from 7 to 20% by weight, based on the dry weight of the coating layer having ultraviolet absorbing energy. By setting the particle diameter of the particles to be contained in the above range, it is preferable to prevent the particles from falling off and to adjust the glossiness of the surface.

In the coating layer having the ultraviolet absorbing energy of the present invention, various additives can be added within a range not inhibiting the effects of the present invention. Additives can be used For example, a fluorescent whitening agent, a crosslinking agent, a heat stabilizer, an antistatic agent, a coupling agent, and the like.

Further, the coating layer having ultraviolet absorbing energy can be applied by any method. For example, gravure coating, roll coating, spin coating, reverse roll coating, rod coating, screen coating, knife coating, air knife coating, impregnation extrusion lamination, etc., especially using a kiss coating of a micro gravure roll The method of coating is preferred because of the superior coating appearance or gloss uniformity. Further, in the case where the coating layer is hardened after coating, the curing method can be carried out by a conventional method. For example, a method of performing heat curing or an active line such as ultraviolet rays, electron beams, or radiation can be further employed. In the present invention, it is preferably a thermal curing method by a hot air oven or an ultraviolet curing method by ultraviolet irradiation. Further, the method of providing the coating layer may be carried out by a method of coating (line coating) at the time of production of the base film, or by coating (off-line coating) on the base film after completion of the crystallization alignment.

In the white laminated polyester film for a reflecting sheet of the present invention, the heat shrinkage ratio at 80 ° C for 30 minutes is preferably 0.5% or less, more preferably 0.0 to 0.3%, more preferably 0.0 to 0.3% in the longitudinal direction and the width direction. 0.0~0.1% or less. When the heat shrinkage ratio exceeds 0.5%, the dimensional change of the film for reflection will become large, and the planarity of the film will be deteriorated, and uneven brightness will occur. Further, the heat shrinkage ratio is preferably larger than 0%. In the case of less than 0.0%, that is, when the film is stretched during heating, since the film is assembled in the backlight unit, the film will stretch, bend or undulate due to the heat of the cold cathode tube or the like. Easy to happen. The method of setting the heat shrinkage ratio to less than 0.5% is not particularly limited, and generally, the stretching ratio at the time of producing the biaxially stretched film is lowered, the heat treatment temperature is increased, and the width direction and/or the long side are simultaneously performed with the heat treatment. The mitigation of the direction and other methods. Both the longitudinal direction and the width direction are for the purpose of obtaining a predetermined heat shrinkage ratio, and it is preferable to carry out the relaxation treatment in the longitudinal direction as well. For the tempering treatment, it is preferable to carry out the method (in-line treatment) in the production of the biaxially stretched polyester film from the viewpoint of the production cost, and it is also possible to pass the film after the primary film formation again through the oven. Method of mitigation processing (offline processing).

Next, an example of the method for producing a white laminated polyester film for a reflecting sheet of the present invention will be described, and the present invention is not limited to such an example.

In the composite film forming apparatus having the extruder (A) and the extruder (B), first, in order to form the polyester layer (A), the titanium oxide particles are mixed in a range of 3 to 15% by weight to melt the melting point of 230 to 280. The pellets of the polyester pellets and the titanium dioxide particles of °C were sufficiently dried under vacuum. In the dry raw material, if necessary, other inorganic particles or ultraviolet absorbers may be added. Next, the dried raw material is supplied to an extruder (A) heated to a temperature of 240 to 300 ° C, melt-extruded, filtered through a 10 to 50 μm filter, and then introduced into a T-die composite nozzle. On the other hand, in order to form the polyester layer (B), the polyester layer (B) is mixed so that the incompatible resin is 12 to 30% by weight and/or the inorganic particles are 30 to 50% by weight. The polyester pellets after vacuum drying, if necessary, are mixed with the incompatible resin pellets in the vacuum dried polyester, and are supplied to the temperature which has been heated to 260 to 300 ° C. In the same manner as in the case of the polyester layer (A), the extruder (B) was melted, filtered, and introduced into a T-die composite nozzle. Further, if necessary, 0.05 to 10% by weight of a dispersing agent may be added to the raw material. Further, the addition of the immiscible resin is carried out by vacuum drying the material previously prepared as the masterbatch. In the T-die compound nozzle, the polymer of the extruder (B) is laminated in a central portion and the polymer of the extruder (A) is A/B/A on both surface sides, and co-extrusion molding is carried out. After being in the form of a sheet, a molten laminated sheet was obtained.

The unmelted laminated film was produced by electrostatically adhering the molten laminated sheet to a rotating drum having a surface temperature of 10 to 60 ° C. The unstretched laminated film is introduced into a roll group heated to a temperature of 70 to 120 ° C, and stretched 3 to 4 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), and is used at a temperature of 20 to 50 ° C. The roller group is cooled.

Next, the both ends of the film are gripped by a clip, and introduced into a tenter, and stretched in a direction perpendicular to the longitudinal direction (width direction) by 3 to 4 times in a gas atmosphere heated to a temperature of 90 to 150 °C.

The stretching ratio in the longitudinal direction and the width direction is set to 3 to 5 times, respectively, and the area magnification (longitudinal stretching ratio × transverse stretching ratio) is preferably 9 to 15 times. When the area magnification is less than 9 times, the reflectance or concealability and film strength of the obtained biaxially stretched laminated film become insufficient. Conversely, if the area magnification exceeds 15 times, it becomes easy to stretch. The tendency to break.

After the crystal alignment of the obtained biaxially stretched laminated film is completed, in order to impart planarity and dimensional stability, heat treatment is performed in a tenter at a temperature of 150 to 240 ° C for 1 to 30 seconds. After uniform annealing, cold However, it is necessary to obtain a void-containing white laminated polyester film of the present invention by coiling, if necessary, by performing corona discharge treatment or the like in order to further improve the adhesion to other substrates. In the above heat treatment step, if necessary, a relaxation treatment of 3 to 12% may be performed in the width direction or the longitudinal direction.

In addition, the biaxial stretching may be either a sequential stretching or a simultaneous biaxial stretching. In the case of the simultaneous biaxial stretching method, the film of the process can be prevented from being broken, and it is difficult to cause the polyester layer (A) to adhere to the heating. The transfer defects that occur with the rollers. Further, after biaxial stretching, re-stretching may be performed in either of the longitudinal direction and the width direction.

The white laminated biaxially stretched film obtained in this manner was provided with a coating layer having ultraviolet absorbing energy by a micro gravure and contact coating, dried at 80 to 140 ° C, and then irradiated with ultraviolet rays to harden the coating layer. Before the application of the ultraviolet absorbing energy thin layer, it is also possible to carry out the prior treatment such as setting the easy adhesion layer.

[Measurement method and evaluation method of characteristics] The characteristic values of the present invention are determined according to the following evaluation methods and evaluation criteria: (1) the size of the microvoid inside the film, the size of the immiscible resin, and the thickness of the polyester layer. After the film was frozen, the cross section was cut along the longitudinal direction and the width direction, and a scanning electron microscope (SEM) S-2100A (manufactured by Hitachi, Ltd., Japan) was used to observe the observed profile by 4000 times magnification. Photographs to explore the presence or absence of tiny voids.

The length of the void and the size of the immiscible resin are measured by the observation photograph obtained by the scanning microscope of the above cross section, and the lengths of the width direction and the thickness direction are measured, and the voids and the respective cavities are calculated by reversing the magnification. The size of the incompatible resin. The average of the size of the void size and the incompatible resin is the cross-sectional photograph 50 of the cross-sectional view cut away from the longitudinal direction, and the cross-sectional photograph of the cross-sectional view cut along the width direction is 50, and the total of 100 holes and the phase are not the same. The resin was dissolved to determine the size in the width direction and the thickness direction, and the average value was obtained. Further, in the case where the longitudinal direction and the width direction are not clear, the measurement may be performed by cutting the cross section in two planes which are arbitrarily perpendicular to the sample.

The size shown in Fig. 1 was measured for the size of the void and the size of the incompatible resin. Further, as shown in Fig. 2, the case where an incompatible resin is observed at the end of the cavity is excluded.

The thickness of each polyester layer was measured by the observation photograph obtained by the scanning microscope of the above-mentioned cross section, and the length of each polyester layer in the thickness direction was measured, and the thickness of each layer was calculated by inversely calculating the magnification. Further, it is suitable to obtain a cross-sectional photograph of the thickness of each ester layer which is cut along the width direction, and to use five cross-section photographs which are arbitrarily selected from mutually different measurement fields, and calculate the average value. Further, in the case where the longitudinal direction and the width direction are not clear, the cross section in any direction may be measured.

(2) Apparent Density The film was cut into a size of 100 mm × 100 mm, and a measuring instrument (No. 7002) having a diameter of 10 mm was placed in a No. 2109-10 manufactured by Mifune Co., Ltd., and the measurement was carried out. The thickness of the dots is calculated as the average value d (μm) of the thickness. In addition, a direct reading balance was used to weigh the film up to a unit of 10 ^-4 g to read the weight w (g). The calculated value was set as apparent density using the following formula: (apparent density) = w/d × 100 (g/cm ³ ).

(3) Average reflectivity The integrating sphere attachment device (ISR 2200 manufactured by Shimadzu Corporation of Japan) was installed in a spectrophotometer (UV2450 manufactured by Shimadzu Corporation, Japan), and the measurement was performed using barium sulfate as a standard plate under the following conditions. The standard board is set to 100% relative reflectance. In the wavelength range of 420 to 670 nm, the average value of the relative reflectance per 10 nm of the wavelength is defined as the average reflectance, and the determination is made using the following criteria. Further, ◎, ○, and △ are acceptable.

◎: very good (102% or more), ○: good (101% or more, less than 102%), △: slightly deteriorated (100% or more, less than 101%), ╳: deterioration (less than 100%) .

<Measurement conditions> Scanning speed: medium speed, Slit: 5.0nm, Reflection angle: 8 inches.

<Standard plate preparation method> 34 g of sulphuric acid white standard reagent (EASTMAN White Reflectance Standard Cat No. 6091) was placed in a cylindrical recess having a diameter of 50.8 mm and a depth of 9.5 mm, and compressed using a glass plate to prepare a compression density. 2 g/cm ³ barium sulfate white standard plate.

Further, the evaluation index of the ultraviolet absorbing ability was measured in the same manner as described above, and the average reflectance of 320 nm to 360 nm was measured. If it is less than 10%, it is good.

(4) Concealment The haze meter (Suga Tester Co., Ltd. HZ-2) and JIS-K7105 (1981) were used to measure the total light transmittance of the polyester film, and the following criteria were used to determine the concealability. Further, ◎, ○, and △ are acceptable.

◎: very good (all light transmittance is less than 2%), ○: good (all light transmittance is 2.0% or more, less than 2.5%), △: slightly deteriorated (all light transmittance is 2-5% or more) , less than 3.0%), ╳: deterioration (all light transmittance is 3.0% or more).

(5) Film stability The number of occurrences of film rupture was utilized for evaluation. The evaluation was performed on the number of daily breaks, and the following criteria were used for the judgment. Further, ○ and △ are acceptable.

○: Good (breaking hardly occurs (less than 1 time/day)), △: slightly deteriorated (rupture happens occasionally (1~2 times/day)), ╳: Deterioration (rupture often occurs (2 times/day or more)).

Example

The following examples are used to illustrate the invention, but the invention is not limited by the examples.

<Example 1>

(Manufacture of polyethylene terephthalate pellets (PET)) By using terephthalic acid as an acid component and ethylene glycol as a diol component, a tricondensation reaction is carried out by adding antimony trioxide (polymerization catalyst) to the obtained polyester pellets in an amount of 300 ppm in terms of a ruthenium atom, and a polycondensation reaction is carried out. Polyethylene terephthalate (PET) having an ultimate viscosity of 0.63 dl/g and a carboxyl terminal group of 40 equivalents/ton was obtained.

(Production of isophthalic acid copolymerized polyethylene terephthalate pellet (PET/I ¹² )) A mixture of 88 mol% of terephthalic acid and 12 mol% of isophthalic acid was used as an acid component. Glycol as a diol component, and the polymerization catalyst is added to the polymerization catalyst in a manner of 300 ppm in terms of a ruthenium atom, and a polycondensation reaction is carried out to obtain a terminal viscosity of 0.68 dl/g and a carboxyl terminal. A terephthalic acid copolymerized polyethylene terephthalate (PET/I ¹² ) with a basis weight of 40 eq/ton.

In the composite film forming apparatus having the extruder (a) and the extruder (b), in order to form the polyester layer (A), vacuum drying of the raw material mixture shown in Table 1 was carried out at a temperature of 160 ° C for 5 hours. Thereafter, it was supplied to the side of the extruder (a), and after melt extrusion at a temperature of 280 ° C, the filter was filtered through a 30 μm filter. After the foreign matter is filtered, the T-die composite nozzle is introduced.

Further, the abbreviation in Table 1 has the following meanings: ● TiO ₂ -A (50): Anatase-type titanium particles produced by a sulfuric acid step containing 50% by weight of an average particle diameter of 0.25 μm and a refractive index of 2.5. Titanium dioxide masterbatch PET pellets.

TiO ₂ -R1 (50): A titanium oxide masterbatch PET pellet containing 50% by weight of rutile-type titanium particles produced by a sulfuric acid method having an average particle diameter of 0.25 μm and a refractive index of 2.7.

TiO ₂ -R ₂ (50): A titanium dioxide masterbatch PET pellet containing 50% by weight of an average particle diameter of 0.22 μm and a refractive index of 2.7 of rutile-type titanium oxide particles produced by a chlorination step.

BaSO ₄ (60)-PET/I ¹² : barium sulfate masterbatch isophthalic acid copolymerized polyethylene terephthalate containing 60% by weight of barium sulfate particles having an average particle diameter of 1 μm and a refractive index of 1.6 (PET) /I ¹² ) pellets

●PMP: polymethylpentene (TPX DX820 manufactured by Mitsui Chemicals Co., Ltd.)

PBT/PAG: "Hytrel (R)" (registered trademark) 7277 (block of Toray Dupont Co., Ltd.) of a block copolymer of polybutylene terephthalate (PBT) and polyalkylene glycol (PAG)

● PEG (6): PET pellets copolymerized with 6% by weight of polyethylene glycol having a molecular weight of 4000

● Light stabilizer (10): contains 10% by weight of three UV absorber (CGX UVA006, manufactured by Ciba Special Chemicals), light stabilizer masterbatch, PET pellets

On the other hand, in order to form the polyester layer (B), after vacuum drying of the raw material mixture shown in Table 1 at a temperature of 160 ° C for 5 hours, it was supplied to the side of the extruder (b) and melted at a temperature of 280 ° C. After the extrusion, the filter was filtered through a 30 μm filter to carry out foreign matter filtration, and then introduced into a T-die composite nozzle.

Next, in the T-die compound nozzle, the polyester layer (A) is laminated on the surface layer of the polyester layer (B) by (A/B/A), and then coextruded into a sheet shape. On the drum having a surface temperature of 180 ° C, a molten laminated sheet was adhered to the molten laminated sheet by a static charge method, and cooled and solidified to obtain an unstretched laminated film. Then, the unstretched laminated film was preheated by a roll group heated to a temperature of 85 ° C according to a conventional method, and then stretched by 3.3 times in the longitudinal direction (longitudinal direction) using a heating roll at a temperature of 90 ° C. A roll group at a temperature of 25 ° C was cooled to obtain a uniaxially stretched film.

While holding both ends of the obtained uniaxially stretched film by a clip, it is introduced into a preheating zone at a temperature of 90 ° C in the tenter, followed by a heating zone continuous at a temperature of 100 ° C, and a direction perpendicular to the longitudinal direction (width direction) ) stretched 3.2 times. Further, the heat treatment in the tenter is performed at a temperature of 200 ° C for 10 seconds, further at a temperature of 180 ° C, a relaxation treatment of 4% in the width direction, and further at a temperature of 140 ° C. 1% relaxation treatment in the width direction. Then, after uniformly annealing, it is taken up to obtain a composite layer of a polyester layer (A) and a polyester layer (B) having a void inside to form a 5/240/5 (μm) A/B/A 3 layer composite structure. Thickness 250μm White laminated polyester film. The white laminated polyester film contained a plurality of fine voids in the polyester layer (B), and the average size of the voids in the width direction was 11.0 μm, and the average size in the thickness direction was 1.3 μm.

One side of the obtained film was coated by contact coating using a micro gravure roll so as to have a thickness of 2 μm after coating the layer (C) of the following formulation, and dried at 120 ° C for 1 minute. Further, on the layer (C), a contact coating using a micro gravure roll was applied so that the thickness of the surface hardened layer (D) layer of the following formulation was hardened to 4 μm, and a hot air dryer of 80 ° C was used to dry the solvent. Thereafter, it was cured by a belt-type metal halide lamp (manufactured by EYE GRAPHIC Co., Ltd.) under an ultraviolet light amount of 300 mJ/cm ² to obtain a white laminated polyester film having a light-resistant hardened layer on one side.

(C) layer coating composition 2-(2'-Hydroxy-5'-methacryloxyethylphenyl)-2H-benzotriazole (30% by weight) copolymerized methyl methacrylate: 95 parts by weight Modified saturated polyester resin "NIKKA COAT" (registered trademark) FS-12 (manufactured by Nippon Chemical Co., Ltd.): 4 parts by weight Methylated melamine "CYMEL" (registered trademark) 370 (manufactured by Mitsui Chemicals Co., Ltd.): 1 part by weight Toluene/methyl ethyl ketone = 1/1: 400 parts by weight

(D) layer coating composition 2-(2'-hydroxy-5'-methacryloxyethylphenyl)-2H-benzotriazole: 20 parts by weight Dipentaerythritol hexaacrylate: 68 parts by weight Acrylic oligomer "ARONIX" (registered trademark) M-7100 (manufactured by Kyoeisha Chemical Co., Ltd.): 8 parts by weight Acrylate 2-hydroxypropyl ester: 4 parts by weight "IRGACURE" (registered trademark) 183 (manufactured by Ciba Geigy Co., Ltd.): 4 parts by weight Toluene/methyl ethyl ketone = 1/1: 312 parts by weight

The characteristics of the white-layered polyester film having the light-resistant hardened layer thus obtained are as shown in Table 3, and have high reflectance and concealability, and also have excellent film stability.

<Example 2>

In the same manner as in Example 1, except that the materials and conditions shown in Table 1 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 15/200/15 (μm). A white laminated polyester film having a thickness of 230 μm in the A/B/A three-layer composite structure was placed in the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardening layer are as shown in Table 3, and the reflectance and the concealability are within the acceptable range of the object which is slightly deteriorated.

<Example 3>

Except that the materials and conditions shown in Table 1 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/234/8 (μm). A white laminated polyester film having a thickness of 250 μm in a three-layer composite structure of A/B/A. Also, in this embodiment In the middle, no light-resistant hardened layer is provided.

The characteristics of the obtained white laminate are as shown in Table 3, and have high reflectance and concealability, and also have superior film stability. Further, since the light-resistant hardened layer is not provided, the ultraviolet absorbing ability is slightly deteriorated.

<Example 4>

Except that the materials and conditions shown in Table 1 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/234/8 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardenable layer are as shown in Table 3. Although the film forming stability was observed to be slightly deteriorated, it had a particularly high reflectance.

<Example 5>

Except that the materials and conditions shown in Table 1 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 15/170/15 (μm). A white laminated polyester film having a thickness of 200 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardening layer are as shown in Table 3, and the concealability is within the acceptable range of the slightly deteriorated material.

<Example 6>

Except for using the raw materials and conditions shown in Table 1, the same implementation was carried out. In the manner of Example 1, it is possible to obtain a white layer having a thickness of 250 μm in a composite structure of a polyester layer (A) and a polyester layer (B) having voids therein to have an A/B/A 3 layer of 8/234/8 (μm). The laminated polyester film was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardening layer are as shown in Table 3, and the reflectance was within the acceptable range of the object which was slightly deteriorated.

<Example 7>

In the same manner as in Example 1, except that the materials and conditions shown in Table 1 and the heat treatment temperature were changed to 185 ° C, the thickness of the polyester layer (A) and the polyester layer (B) having voids therein were obtained. A white laminated polyester film having a thickness of 190 μm in a 15/160/15 (μm) A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardening layer are as shown in Table 3, and the reflectance and the concealability are within the acceptable range of the object which is slightly deteriorated. Further, this embodiment 7 is a reference example.

<Example 8>

In the same manner as in Example 1, except that the materials and conditions shown in Table 1 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/284/8 (μm). A white laminated polyester film having a thickness of 300 μm in the A/B/A three-layer composite structure was placed in the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 3, and both reflectance and concealability are particularly high, and the characteristics are excellent.

<Example 9>

Except that the materials and conditions shown in Table 1 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/384/8 (μm). A white laminated polyester film having a thickness of 400 μm in the A/B/A three-layer composite structure was placed in the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 3, and both reflectance and concealability are particularly high, and the characteristics are excellent.

<Example 10>

Except that the materials and conditions shown in Table 1 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 5/240/5 (μm). A white laminated polyester film having a thickness of 250 μm in a three-layer composite structure of A/B/A. However, the light-resistant hardened layer is not provided. The characteristics of the obtained white laminated polyester film are as shown in Table 3, and the reflectance and the concealing property were both particularly high, and the characteristics were excellent.

<Example 11>

Except that the materials and conditions shown in Table 1 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 15/150/15 (μm). A white laminated polyester film having a thickness of 180 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are shown in Table 3.

<Comparative Example 1>

Except that the materials and conditions shown in Table 2 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 20/210/20 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer were as shown in Table 4, and the reflectance was deteriorated.

<Comparative Example 2>

In the same manner as in Example 1, except that the materials and conditions shown in Table 2 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 3/244/3 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4. Although the reflectance and the concealability were acceptable, the film forming stability was deteriorated.

<Comparative Example 3>

Except that the materials and conditions shown in Table 2 were used, the same manner as in Example 2 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 15/220/15 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4, and the reflectance Getting worse.

<Comparative Example 4>

In the same manner as in Example 1, except that the materials and conditions shown in Table 2 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/234/8 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4, and the reflectance and the concealability were deteriorated.

<Comparative Example 5>

In the same manner as in Example 1, except that the materials and conditions shown in Table 2 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/234/8 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer were as shown in Table 4, and the reflectance was deteriorated.

<Comparative Example 6>

Except that the materials and conditions shown in Table 2 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was tried to be 8/234/8 (μm). In the manufacture of a white laminated polyester film having a thickness of 250 μm in a three-layer composite structure of A/B/A, cracking often occurs, and film formation is impossible.

<Comparative Example 7>

In the same manner as in Example 1, except that the materials and conditions shown in Table 2 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/234/8 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4, and the reflectance and the concealability were deteriorated.

<Comparative Example 8>

In the same manner as in Example 1, except that the materials and conditions shown in Table 2 were used, the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 8/234/8 (μm). A white laminated polyester film having a thickness of 250 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4, and the reflectance and the concealability were deteriorated.

<Comparative Example 9>

Except that the materials and conditions shown in Table 2 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 15/130/15 (μm). A white laminated polyester film having a thickness of 160 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4, and concealability Getting worse.

<Comparative Example 10>

In the same manner as in Example 1, except that the materials and conditions shown in Table 2 and the heat treatment temperature were changed to 185 ° C, the thickness of the polyester layer (A) and the polyester layer (B) having voids therein were obtained. A white laminated polyester film having a thickness of 180 μm of a 15/150/15 (μm) A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer are as shown in Table 4, and the reflectance and the concealability were deteriorated.

<Comparative Example 11>

Except that the raw materials and conditions shown in Table 2 and the heat treatment temperature were changed to 185 ° C, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was tried. /150/15 (μm) A/B/A three-layer composite structure The thickness of a 180 μm white laminated polyester film is produced, and cracking often occurs, making it impossible to form a film.

<Comparative Example 12>

Except that the materials and conditions shown in Table 2 were used, the same manner as in Example 1 was carried out, and the thickness of the polyester layer (A) and the polyester layer (B) having voids inside was obtained to be 15/158/15 (μm). A white laminated polyester film having a thickness of 188 μm in the A/B/A three-layer composite structure was subjected to the same manner as in Example 1, and a light-resistant hardened layer was provided on one side thereof. The characteristics of the white laminated polyester film having the obtained light-resistant hardened layer were as shown in Table 4, and the reflectance was greatly deteriorated.

Industrial use possibility

The present invention relates to a white laminated polyester film for a reflective sheet. More specifically, the present invention relates to a polyester film having a laminated structure, superior reflection characteristics, concealability, and good productivity, and a reflective sheet which can be applied to a backlight device for image display and a lamp mirror. A white laminated polyester film such as a reflection sheet for an illumination device, a reflection sheet for an illumination sign, and a back reflection sheet for a solar cell.

1‧‧‧Resin incompatible with polyester resin

2‧‧‧ hollow

3‧‧‧The width of the void

4‧‧‧ thickness of void

5‧‧‧Width of immiscible resin

6‧‧‧ Thickness of immiscible resin

Figure 1 is a cross-sectional view of a void occurring around an immiscible resin.

Figure 2 is a cross-sectional view of a void in which no incompatible resin is observed.

Claims (13)

A white laminated polyester film for a reflective sheet which is attached to at least one side of a polyester layer (B) having voids therein, and a laminated polyester film having a polyester layer (A) laminated thereon, the laminated polyester film conforming All of the following (1) to (8): (1) at least the polyester layer (A) on one side is 5 to 15 μm thick; (2) in the polyester layer (A), relative to the polyester layer ( A) containing 3 to 15% by weight of particles having a refractive index of 2.0 or more; (3) having a thickness of the polyester layer (B) of 150 μm or more; and (4) being opposite to the polyester layer (B) in the polyester layer ( The amount of the particles having a refractive index of 2.0 or more contained in B) is 2% by weight or less; (5) the polyester layer (B) contains 12 to 25% by weight of the polyester layer (B) with respect to the polyester layer (B). a resin incompatible resin, and/or 30 to 50% by weight of inorganic particles having a refractive index of less than 2.0; (6) a resin which is incompatible with the polyester resin contained in the polyester layer (B) Polymethylpentene; (7) The average particle size of the polymethylpentene in the polyester layer (B) is 3 μm or less in the width direction and 2 μm or less in the thickness direction; and (8) Polyester layer (B) Copolymerization of a polyester resin composed of a polyalkylene glycol, an aliphatic diol component having 2 to 6 carbon atoms, and terephthalic acid Fat, and relative to the entire polyester layer (B), the content of the copolymerized resin is 0.05 to 10 wt%. A white laminated polyester film for a reflective sheet according to the first aspect of the invention, wherein the particles having a refractive index of 2.0 or more contained in the polyester layer (A) are titanium dioxide particles. A white laminated polyester film for a reflective sheet according to item 2 of the patent application scope, The content of the titanium dioxide particles in the polyester layer (A) is from 3 to 7% by weight based on the entire polyester layer (A). A white laminated polyester film for a reflective sheet according to item 3 of the patent application, wherein the polyester layer (A) has a thickness of 5 to 10 μm, and the polyester layer (B) has a thickness of 200 to 400 μm. A white laminated polyester film for a reflective sheet according to the fourth aspect of the invention, wherein the titanium dioxide particles contained in the polyester layer (A) are mainly composed of a rutile type. A white laminated polyester film for a reflective sheet according to claim 5, wherein the titanium oxide particles contained in the polyester layer (A) are mainly composed of a rutile type produced by a chlorination method. A white laminated polyester film for a reflective sheet according to the first aspect of the invention, wherein the resin constituting the polyester layer (A) and the polyester layer (B) has polyethylene terephthalate as a basic structure. A white laminated polyester film for a reflective sheet according to the first aspect of the patent application, wherein the copolymerization of a polyalkylene glycol, a polyester diol having a carbon number of 2 to 6 and a polyester resin composed of terephthalic acid The resin is a block copolymer of polyalkylene glycol and polybutylene terephthalate. A white laminated polyester film for a reflective sheet according to the first aspect of the invention, wherein the inorganic particles having a refractive index lower than 2.0 contained in the polyester layer (B) are barium sulfate. A white laminated polyester film for a reflective sheet according to the first aspect of the invention, wherein a coating layer having ultraviolet absorbing energy is provided on at least one side surface. A white laminated polyester film for a reflective sheet according to the first aspect of the patent application, wherein the polyester layer (A) contains 0.05 to 10 with respect to the polyester layer (A). % by weight of light stabilizer. The white laminated polyester film for a reflective sheet according to any one of claims 1 to 11, wherein the polyester layer (A) side is used as a light reflecting surface. A white laminated polyester film for a reflection sheet according to claim 12, which is a back surface reflection sheet for a backlight for a liquid crystal display having a polyester layer (A) side as a light reflection surface.