DESCRIPTION Process for Producing White Laminated Film and White Laminated Polyester Film TECHNICAL FIELD [0001] The present invention relates to improvement of a white film, and more particularly to a white film that is suitable as a reflecting member for a surface light source (reflecting plate and reflector) and is able to have low glossiness, productivity, and reflectance properties. BACKGROUND ART [0002] In liquid crystal displays which are used frequently in an information displaying device and the like, in order to ensure high luminance, a surface light source called backlight is installed at the back of the display to radiate light. In addition, the backlight needs not only to simply radiate light but also to illuminate the whole screen uniformly. As a method that satisfies this property, there are structures of a surface light source that are called side-light type and direct type. In particular, to a flat display used in a notebook computer and the like, a side-light type backlight, i.e., a backlight that radiates light from the side of a screen is applied. [0003] Generally, this side-light type employs a light guide plate method in which, using as an illumination source a cold cathode fluorescent lamp at an edge of a light guide plate, a light guide plate which uniformly propagates/diffuses light is utilized to illuminate the whole liquid crystal display uniformly. In this method, to make more efficient use of light, a reflector is arranged around the cold cathode fluorescent lamp, and, in addition, a reflecting plate is arranged under the light guide plate in order to reflect the light diffused from the light guide plate efficiently toward the liquid crystal screen. This reduces the loss of the light from the cold cathode fluorescent lamp and provides a function to brighten the liquid crystal screen. PRIOR ART DOCUMENTS PATENT DOCUMENTS [0004] Patent Document 1: JP 2004-90523 A SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0005] In the case of using the method described in Patent Document 1 mentioned above, when obtaining an unstretched film by solidifying a melt extruded sheet by cooling on a drum, a drum with a roughened surface has been used to provide low glossiness on the film surface. This method suffers from poor productivity due to, for example, the introduction and maintenance of the drum with a roughened surface and is disadvantageous in terms of cost. [0006] It is difficult to obtain a white film with low glossiness at low cost by the prior art described above. [0007] Thus, an object of the present invention is to provide a process for producing a white film with excellent low glossiness and excellent productivity, which could not be achieved by the conventional study described above. Another object is to inexpensively provide a reflecting member for a surface light source with excellent low glossiness by using the white film. MEANS FOR SOLVING THE PROBLEMS [0008] The present inventors intensively studied to discover that a white film with low glossiness can be produced readily and inexpensively in a stable manner by providing a biaxially-oriented white laminated polyester film having, for example, a coating layer (hereinafter referred to as a resin layer) on at least one surface of the white film, the resin layer having at least five cracks (hereinafter referred to as depressions) with an area of 1 to 20 (am2 per 900 ^m2 of the resin layer. [0009] Thus, the present invention uses the following means. 1) A biaxially-oriented white laminated polyester film having a resin layer on at least one side of a white polyester film, wherein at least five depressions with an area of 1 to 20 um2 are present per 900 (am2 of film surface area on a resin layer-side surface of the biaxially-oriented white laminated polyester film. 2) The biaxially-oriented white laminated polyester film according to 1), wherein the surface roughness Rz on the resin layer-side of the biaxially-oriented white laminated polyester film is not less than 1.0 um. 3) The biaxially-oriented white laminated polyester film according to 1) or 2), wherein the resin layer is formed by using an acrylic binder. 4) The biaxially-oriented white laminated polyester film according to any one of 1) to 3), wherein the resin layer contains inorganic particles and (1) to (3) are satisfied: 7.17.6-P (3) wherein P is a surface pH of the resin layer, and R is a number density of particles in the resin layer (R) [number/urn ]. 5) The biaxially-oriented white laminated polyester film according to 4), excluding the range where the following equations (4) and (5) are simultaneously satisfied: 0.37.6-P (3) ■ Further, it is more preferable to exclude the range where the following equations (4) and (5) are simultaneously satisfied in terms of glossiness. 0.3 60 integrating sphere 130-0632 (Hitachi Ltd.) (with an inner surface made of barium sulfate) and a 10° inclined spacer were installed in a spectrophotometer U-3410 (Hitachi Ltd.), in which conditions an optical reflectance at 560 nm was determined. For the optical reflectance, the value determined by measurement from the resin layer side of the white laminated film was used as a reflectance of the white film. As a reference white plate, a part number 210-0740 (aluminum oxide) available from Hitachi Instruments Service Co., Ltd. was used. [0077] E. Line Contamination during Production A taking-up roll of a winder after transverse stretching was visually observed, and assessment was made according to the criteria below. A: Contamination not observable B: Readily visually observable [0078] F. Method of Measuring Surface pH (P) A film sample was left to stand in the ordinary state (temperature 23 °C, relative humidity 65%) for 24 hours, and then a surface pH was measured using a pH meter available from HORIBA, Ltd. "COMPACT pH meter twin pH (type B-212)" by the following method. Ultrapure water with (23°C) a pH of 7.0 in an amount of 1.0 ml was added dropwise to a sensor to cover the sensor with ultrapure water. Then, a sample that had been cut into a rectangle of 5 x 15 mm such that two electrodes of the sensor part was covered was set such that a coating surface was in contact with droplets, and a measurement value after 1 minute was read out at a temperature of 23°C and a relative humidity of 65%. In the measurement, five from some of the film samples prepared were cut into the above size, and each of the five samples were measured once; the mean value was used as a surface pH value. [0079] G. Method of Measuring pH of Coating Solution A pH of a coating solution was measured using a pH meter available from HORIBA, Ltd. "COMPACT pH meter twinpH (type B-212)" by the following method. A prepared coating solution (23°C) in an amount of 1.0 ml was added dropwise to a sensor to cover the sensor with the coating solution, and a measurement value after 1 minute was read out at a temperature of 23 °C and a relative humidity of 65%. The measurement was made five times in a similar manner, and the mean value was used as a pH value of the coating solution. [0080] H. Method of Measuring Number Density of Particles (R) The resin layer-side surface of the white laminated film was observed under x 5,000 magnification using a field-emission scanning electron microscope "JSM- 6700F" (manufactured by JEOL Ltd.) to take a photograph, from which the particle number in a visual field area of 10 (am square was counted, and the particle number per (im2 was calculated. The calculation was carried out in a similar manner at different five visual fields, and the mean value of the values was used as a number density of particles. For aggregation parts where 10 or more particles per 2 urn square are aggregated when observed in a surface photograph, the value three times the number observed on the surface shall be counted. [0081] I. Surface Roughness Rz (Ten-Point Average Roughness) An atomic force microscope (AFM) was used to scan an image at an area of 100-um square measured view of 10000 um2 on the resin layer-side surface of the biaxially-oriented white laminated polyester film. For the measured image obtained, a three-dimensional surface roughness was calculated by Off-Line Roughness Analysis to determine a ten-point average roughness Rz. Further, the measurement was made in a similar manner at five visual fields in different areas, and Rz was calculated by the mean value of the values. The measurement conditions are as follows: Apparatus: NanoScope Ilia ver. 3.2 using AFM J scanner (available from Digital Instruments) Probe: SPM probe NCH-W type available from Nanosensors, single-crystal silicon Scanning mode: Tapping mode Scan field: 100 um x 100 urn Scan rate: 0.5 Hz EXAMPLES [0082] The present invention will now be described more specifically by way of Examples and the like, but the present invention is not limited thereto. [0083] (1) White Film Polyester Resin (a 1) Using terephthalic acid as an acid component and ethylene glycol as a glycol component, antimony trioxide (polymerization catalyst) was added in an amount of 300 ppm in terms of antimony atoms relative to a resulting polyester pellet to carry out a polycondensation reaction, whereby a polyethylene terephthalate pellet (PET) with a limiting viscosity of 0.63 dl/g and a terminal carboxyl group amount of 40 equivalents/ton was obtained. Using a differential thermal analyzer, the heat of crystal fusion was measured to be not less than 4.186 J/g, showing that the polyethylene terephthalate pellet was a crystalline polyester resin. The melting point Tm of this resin was measured to be 250°C. [0084] Cyclic Olefin Copolymer Resin (bl) A cyclic olefin resin "TOPAS" (available from Polyplastics Co., Ltd.) having a glass transition temperature of 178°C and a melt volume rate MVR (260°C/2.16 kg) of 4.5 ml/10 mim was used. Using a differential thermal analyzer, the heat of crystal fusion was measured to be less than 4.186 J/g, showing that the cyclic olefin resin was an amorphous resin. [0085] Inorganic Particles (B2) Titanium oxide (available from ISHIHARA SANGYO KABUSHIKI KAISHA, LTD., rutile-type titanium dioxide R-980, average particle size 0.24 urn). [0086] Copolyester Resin (C) As other additives, CHDM (cyclohexanedimethanol) copolymerized PET was used. This is a PET obtained by copolymerizing 30 mol% of cyclohexanedimethanol as the copolymerization glycol component. Using a differential thermal analyzer, the heat of crystal fusion was measured to be less than 4.186 J/g, showing that the CHDM copolymerized PET was an amorphous resin. [0087] Copolyester Resin (D) As other additives, CHDM (cyclohexanedimethanol) copolymerized PET was used. This is a PET obtained by copolymerizing 60 mol% of cyclohexanedimethanol as the copolymerization glycol component. Using a differential thermal analyzer, the heat of crystal fusion was measured to be less than 4.186 J/g, showing that the CHDM copolymerized PET was an amorphous resin. [0088] Copolyester Resin (E) As other additives, isophthalic acid copolymerized PET was used. This is a PET obtained by copolymerizing 17.5 mol% of isophthalic acid as dicarboxylic acid component. Using a differential thermal analyzer, the heat of crystal fusion was measured to be less than 4.186 J/g, exhibiting amorphous properties. [0089] Dispersant (F) As other additives, PBT-PAG (polybutylene terephthalate-polyalkylene glycol) block copolymer (available from DU PONT-TORAY CO., LTD., Hytrel 4047) was used. The resin is a block copolymer of PBT and PAG (mainly, polytetramethylene glycol). Using a differential thermal analyzer, the heat of crystal fusion was measured to be not less than 4.186 J/g, showing that the PBT-PAG block copolymer was a crystalline resin. [0090] (2) Coating Solution Acrylic Binder (G) WATERSOL PW-1100 (available from DIC Corporation, 45% by weight solution) was diluted with purified water to a 35% by weight solution. Acrylic Binder (K) Nikasol A-08 (available from NIPPON CARBIDE INDUSTRIES CO., INC., 35% by weight solution) Lithium Salt (H) Lithium polystyrenesulfonate (available from TOSOH ORGANIC CHEMICAL CO., LTD., "SPINOMAR" (registered trademark) LiSS, 16% by weight solution). Ammonium Salt (J) Ammonium polystyrenesulfonate (available from TOSOH ORGANIC CHEMICAL CO., LTD., "SPINOMAR" (registered trademark) AmSS, 16% by weight solution). Inorganic Particles (I) Water dispersion of 10% by weight solution obtained by mixing silica particles having an average particle size of 0.3 um with distilled water. pH Adjuster (L) Polyethyleneimine (available from NIPPON SHOKUBAI CO., LTD., "EPOMIN" (registered trademark) 100% by weight solution). [0091] (Example 1) A mixture of materials shown in Tables 1 to 4 was vacuum-dried at a temperature of 180°C for 3 hours and then fed to an extruder. After melt extrusion at a temperature of 280°C, the mixture was filtered through a 30-um cut filter, and then introduced into a T-die head. [0092] Then, the mixture was extruded from inside the T-die head into a sheet form to obtain a melt monolayer sheet, and the melt monolayer sheet was solidified by contact cooling on a drum, the surface temperature of which was maintained at 25°C, using the electrostatic application method to obtain an unstretched monolayer film. Thereafter, after preheating with a group of rollers heated to a temperature of 70°C, the unstretched monolayer film was stretched 3.6-fold in the longitudinal direction (machine direction) while being irradiated by a infrared ray heater (output: 1.4 kW, distance from the film: 15 mm, irradiation time: 0.72 sec) from both sides, and cooled with a group of rollers at a temperature of 25 °C to obtain a uniaxially stretched film. [0093] Further, thereafter, the drum-contacting side of the unstretched laminated film was subjected to corona discharge treatment in air, and a coating solution for forming a coated layer described below was applied to the treated surface by the bar coating method using a metering bar. [0094] The uniaxially stretched film coated with the coating solution for forming a coated layer described above was conducted to a preheating zone at 110°C in a tenter with both ends held by clips, dried while being subjected to 5% slight stretching, and then successively and continuously stretched 3.5-fold in the direction perpendicular to the longitudinal direction (transverse direction) in a heating zone at 120°C. Further, successively, the film was subjected to heat treatment of 220°C in a heat treatment zone in the tenter, further, subjected to 4% relaxation treatment at 180°C in the transverse direction, followed by further 1% relaxation treatment at 110°C, and then took up after uniform slow cooling to thereby obtain a white film having the degree of whiteness of 86.0% in which a coated layer with a thickness of 150 nm was provided on a film with a thickness of 188 urn. The composition and production conditions of the film are as shown in Tables 1 to 4. The evaluation results of physical properties are shown in Tables 5 and 6. [0095] (Preparation of Coating Solution) Each component described above was formulated based on the formulation ratio value in Tables 1 to 4 such that the solid content ratio was as shown in Tables 1 to 4, and purified water was used to make an adjustment such that the solid content concentration after formulation was 6.0%. For the ratio of the solid contents other than the inorganic particles, the solid content ratio (% by weight) of each component was calculated based on the total weight of G, K, H, J, and L, components other than the inorganic particles (I). For the order of the formulation, the above-described coating agents G, K, H, J, I, and L were formulated into a vessel containing weighed purified water in the order mentioned. After the formulation, the formulation was stirred with a universal stirrer for 10 minutes, and then the coating solution was adjusted. [0096] (Examples 2 to 31) Films were produced in the same manner as in Example 1 using the film composition, production conditions, and coating solution composition shown in Tables 1 and 3. The evaluation results of physical properties are shown in Table 5. [0097] (Comparative Examples 1 to 21) Films were produced in the same manner as in Example 1 using the film composition, production conditions, and coating solution composition shown in Tables 2 and 4. The evaluation results of physical properties are shown in Table 6. In Comparative Example 7, film breakage occurred in the transverse stretching process, and a film could not be produced. DESCRIPTION OF SYMBOLS [0104] 1,2, 8, 9, 10,11: Depressions 3, 7,12,13,15, 16: Resin layer 4: Resin layer thickness 5: Threshold line at 30% of resin layer thickness percentage 6: White film 14: Inorganic particles CLAIMS 1. A biaxially-oriented white laminated polyester film having a resin layer on at least one side of a white polyester film, wherein at least five depressions with an area of 1 to 20 um2 are present per 900 um2 of film surface area on a resin layer-side surface of the biaxially-oriented white laminated polyester film. 2. The biaxially-oriented white laminated polyester film according to claim 1, wherein the surface roughness Rz on the resin layer-side of the biaxially-oriented white laminated polyester film is not less than 1.0 urn. 3. The biaxially-oriented white laminated polyester film according to claim 1 or 2, wherein the resin layer is formed by using an acrylic binder. 4. The biaxially-oriented white laminated polyester film according to any one of claims 1 to 3, wherein the resin layer contains inorganic particles and (1) to (3) are satisfied: 7.17.6-P (3) wherein P is a surface pH of the resin layer, and R is a number density of particles in the resin layer (R) [number/p.m ]. 5. The biaxially-oriented white laminated polyester film according to claim 4, excluding the range where the following equations (4) and (5) are simultaneously satisfied: 0.3