JP2002326330A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film having hardly destructible projections uniform in height and excellent in abrasion resistance, transparency, slip properties, workability, dimensional stability or the like. SOLUTION: The laminated polyester film is obtained by laminating a polyester layer (A) on at least the single surface of a polyester layer (B). The polyester layer (A) contains inert particles with a void diameter ratio of 2.0 or less, and the melting point TmA of the polyester layer (A) and the melting point TmB of the polyester layer (B) satisfy the formula (1): TmB-80<=TmA<=TmB-10. The coefficient of the projection height distribution of at least the single surface of the film is not more than -10 and the average roughness Ra of the single surface of the film is not less than 10 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film excellent in abrasion resistance, transparency, slipperiness, workability and the like and having a low heat shrinkage. For more information,
TECHNICAL FIELD The present invention relates to a polyester film suitable for uses such as thermal transfer, packaging, plate making printing, X-ray photography, microfilm, electrophotography, and metal deposition.

[0002]

2. Description of the Related Art One of the main uses of a polyester film is a so-called transparent film. In order to facilitate not only the transparency but also the handling workability,
Abrasion resistance is required to prevent slippage and surface damage.
As a means for achieving such properties, a method of providing lubricity to the surface layer by a coating method or blending a lubricant is also known, but there are many difficulties in terms of cost, reliability, and the like. In addition, the types and properties of the particles have been limited, and a laminated film has been proposed. For example, JP-A-3-20664
No. 5 proposes that the transparency, lubricity and abrasion resistance of the film are satisfied by using organic polymer fine particles coated with aluminum oxide. Japanese Patent Application Laid-Open No. 4-325532 discloses that by using crosslinked polymer particles having a narrow particle size distribution, transparency and film surface condition are good (prevention of so-called marbling defects) and satisfactory lubricity is satisfied. Japanese Patent Application Laid-Open No. 7-314626 describes that a laminated film reduces the amount of added particles to achieve both high transparency and easy lubrication.

However, with regard to the transparency of a base film in recent years, the problem is that the decrease in transparency due to light scattering and absorption inside the base film is more problematic than the decrease in transparency due to light scattering on the base film surface. Has become. On the other hand, transparent film applications are sometimes exposed to high temperatures, and there is a strong demand for small shrinkage of the film due to heating. Furthermore, film manufacturing processes and processing processes in various applications, such as printing processes in packaging applications,
In the step of applying a transfer layer in thermal transfer applications, as the process speed increases, deterioration of the surface state due to abrasion of projections on the film surface due to the contacting roll has recently become a problem.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laminated polyester having projections of uniform height which are not easily broken, and which are excellent in abrasion resistance, transparency, slipperiness, workability, dimensional stability and the like. It is to provide a film.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that the film characteristics can be significantly improved by using a laminated film having a specific structure. The present invention has been completed.

That is, the gist of the present invention is a film in which a polyester layer (A) is laminated on at least one surface of a polyester layer (B), wherein the polyester layer (A) comprises:
It contains inert particles having a void diameter ratio of 2.0 or less, the melting point TmA of the polyester layer (A) and the melting point TmB of the polyester layer (B) satisfy the following expression, and the projection height distribution on at least one of the film surfaces. The laminated polyester film has a coefficient of −10 or less and an average roughness Ra of the surface of 10 nm or more. TmB-80 ≦ TmA ≦ TmB-10 ............

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester of the polyester layer (B) in the present invention includes aromatic dicarboxylic acids such as terephthalic acid and naphthalene-2,6-dicarboxylic acid, and ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, It is a polyester having an ester with a glycol such as 4-cyclohexanedimethanol as a main component. The polyester can be obtained by directly polymerizing an aromatic dicarboxylic acid and a glycol, or by subjecting a transalkylation reaction of an aromatic dicarboxylic acid dialkyl ester and a glycol to a polycondensation method, or a diglycol of an aromatic dicarboxylic acid. It can also be obtained by a method such as polycondensation of an ester. Representative examples of the polyester include polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate (PEN).

Further, the polyester used for the polyester layer (B) is preferably synthesized without adding particles having an average particle diameter of 0.1 μm or more which are added for purposes other than the purpose of the polymerization catalyst. Such a polyester does not contain or contains insoluble particles that absorb or scatter light, so that a film having high transparency can be obtained.
The polyester used for the polyester layer (B) may be a mixture of two or more types of polyester raw materials, or a polyester mixture in which recycled materials are mixed. Further, although not particularly limited, it is preferable that the copolymer component is small or not contained. Although depending on the film forming conditions, when the copolymer component is contained to a certain extent or more, the heat shrinkage of the film tends to increase. Further, if necessary, additives such as an antistatic agent, a coloring agent, an antioxidant, an antifoaming agent, a fluorescent whitening agent, and a light-shielding agent may be contained.

In the present invention, it is essential that a specific polyester layer (A) is laminated on at least one surface of the transparent polyester layer (B). In the polyester layer (A), in order to improve the lubricity of the film,
Specific projections are formed on the film surface using specific inert particles. Although the particle size distribution of the inert particles used in the present invention is not particularly limited, narrowing the particle size distribution of the particles leads to narrowing the distribution of the film surface protrusion height.
Specifically, Dw / Dn, which is a parameter indicating the sharpness of the particle size distribution, is preferably 1.8 or less, more preferably 1.5 or less. Dw / Dn is 1.8
When the inert particles exceed the above, coarse projections are formed on the film surface, and as a result, surface defects of the film may occur. Further, the height of the projections formed on the surface becomes uneven, and the load applied to the large projections is concentrated, so that the abrasion resistance during running of the film tends to deteriorate.

The void diameter ratio representing the size of the voids around the inert particles is 2.0 or less, preferably 1.7 or less. When the void diameter ratio exceeds 2.0, particles are dropped off from the film surface due to friction generated on the film surface, and the wear resistance is deteriorated. Furthermore, since the voids (voids) around the particles are large, the scattered light transmittance increases and the transparency of the film deteriorates. The average particle size of the inert particles is not particularly limited, but is usually in the range of 1.0 to 5.0 μm, and preferably in the range of 1.2 to 4.0 μm. Average particle size is 1.0μ
When the particle size is less than m, a large amount of addition is required in order to impart lubricity to the film and lower the coefficient of friction, and as a result, the transmittance of light scattered inside the film tends to increase. On the other hand, when the average particle diameter exceeds 5.0 μm, the formed protrusions become large, and the film surface state and transparency tend to deteriorate.

The amount of the crosslinked polymer particles is not particularly limited, but is usually 0.001 to 0.45% by weight, preferably 0.005 to 0.3% by weight. If the addition amount is less than 0.001% by weight, the effect of improving the slipperiness may be insufficient, and if the content exceeds 0.45% by weight, the slipperiness does not change, and conversely the abrasion resistance and the transparency are improved. May worsen. These inert particles imparting slipperiness are:
One or two or more can be contained. Typical examples include monodisperse polymer particles having an appropriate cross-linking structure. For example, a monovinyl compound (A) having only one aliphatic unsaturated bond in a molecule and a molecule as a cross-linking agent A copolymer with the compound (B) having two or more aliphatic unsaturated bonds therein can be exemplified.
Such monodisperse polymer particles preferably have a group capable of reacting with the polyester on the particle surface. Examples of such a functional group include a hydroxyl group and a carboxylic acid group.

As the inert particles, inorganic particles having a narrow particle size distribution and a high affinity for polyester, such as silica, capable of keeping the projection height distribution coefficient of the film within the above-mentioned range. Particles, calcium carbonate particles, hydroxyapatite particles and the like may be used. In the present invention, the height distribution coefficient (defined later) of the protrusions on at least one surface is -10 or less, preferably-
20 or less. If the height distribution coefficient of the projections is larger than -10, the projection heights on the film surface are not uniform, so that the load is concentrated on the large projections and the wear of the film increases.
Further, the surface satisfying the above-mentioned projection height distribution coefficient has an average surface roughness Ra of 10 nm or more, preferably 15 nm or more. Average surface roughness Ra is 10
In the case of a film having a thickness of less than nm, workability such as slipperiness and film winding property deteriorates.

In the film of the present invention, the melting point TmA of the polyester layer (A), which is the lubricant particle-containing layer, needs to be 10 to 80 ° C. lower than the melting point TmB of the polyester layer (B). This is based on the finding that the size of voids (voids) generated around the particles during film stretching is affected by the affinity of the particles with the polyester, but also depends on the melting point of the polyester. Although the reason is not clear, it is considered that since the hardness of the polyester at the stretching temperature is lower in the polyester having a lower melting point, voids generated around the inert particles become smaller. Also, the load in the thickness direction of the particles applied during stretching is reduced,
The degree of deformation of inert particles that cause deformation, such as crosslinked polymer particles, is reduced. As a result, the film surface roughness becomes high, the film shows good slipperiness, winding workability and abrasion resistance, and the resulting voids are small and have excellent transparency.

When the difference between the melting points of the polyester layer (B) and the polyester layer (A) is less than 10 ° C., there is almost no effect of suppressing the formation of voids around the particles, and the inert particles that cause deformation have a large degree of deformation. As a result, the surface roughness of the film decreases, and the slip characteristics and winding workability deteriorate.
On the other hand, if the melting point difference exceeds 80 ° C., the film sticks to the roll, making film formation difficult and abrasion resistance worsening. The thickness of the polyester layer (A) in the present invention is not particularly limited, but is usually in the range of 0.2 to 5 times the average particle diameter of the inert particles contained in the polyester layer (A), and is preferably. The range is 0.5 to 3 times. If the thickness of the polyester layer (A) is less than 0.2 times the average particle size, the inert particles tend to fall off the film surface due to friction during film running, and the abrasion resistance tends to deteriorate. If the particle size is 5 times or more, even if inert particles having a narrow particle size distribution are used, there is a difference in the height of projections generated between particles near the film surface and particles near the polyester layer (B). As a result, the height distribution of the protrusions becomes large, which may cause deterioration of wear resistance.

The internal scattered light transmittance of the laminated polyester film of the present invention is usually 2% or less, preferably 1% or less. When the internal scattered light transmittance exceeds 2%, it may not be suitable for photographic applications and display substrate films, which require strict transparency. Further, the heat shrinkage of the laminated polyester film of the present invention is usually 5% or less, preferably 3% or less. If the heat shrinkage exceeds 3%, the dimensional change of the film due to heat increases, and it may not be suitable as a film substrate for a display device having a heat source.

The polyester used in the polyester layer (A) in the present invention includes an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, ethylene glycol, diethylene glycol, tetramethylene glycol, The main component is an ester with glycol such as pentyl glycol, 1,4-cyclohexanedimethanol or the like, and 30 mol% or less of the dicarboxylic acid component is a dicarboxylic acid component other than the main component, and / or 30 mol% of the diol component. The following are copolymer polyesters that are diol components other than the main component.

The polyester can be obtained by directly polymerizing an aromatic dicarboxylic acid and a glycol, or by subjecting an aromatic dicarboxylic acid dialkyl ester and a glycol to a transesterification reaction followed by polycondensation, or Can also be obtained by a method such as polycondensation of the diglycol ester of Representative examples of the polyester include a copolymer of terephthalic acid (main component) and isophthalic acid (subcomponent) and ethylene glycol, and a copolymer of terephthalic acid, ethylene glycol (main component) and propylene glycol (subcomponent). There is. The polyester layer (A) contains, if necessary, other inert particles and additives such as an antistatic agent, a coloring agent, an antioxidant, an antifoaming agent, a fluorescent whitening agent and a light-shielding agent. You may.

Next, the method for producing the film of the present invention will be described specifically, but the present invention is not particularly limited to the following examples as long as the constitutional requirements of the present invention are satisfied. After melt-extruding a polyester containing substantially no particulate lubricant and a polyester containing a predetermined amount of particles from separate extruders, they are joined and laminated in a laminar flow form in a molten polymer channel tube or an extrusion die. And discharge it from the extrusion die,
Create an unstretched laminated film. The unstretched film thus obtained is subjected to the next stretching step. In the stretching step, the film is stretched in a longitudinal direction (longitudinal direction) and / or an area magnification of 1.1 to 50 times, preferably 6 to 30 times in a temperature range of Tg-10 ° C. to Tc-10 ° C.
Or it is stretched in the width direction (lateral direction). The stretching method may be uniaxial stretching or biaxial stretching depending on the application. When performing biaxial stretching, any of sequential biaxial orientation stretching, simultaneous biaxial orientation stretching, and a combination thereof may be used. In the case of sequential biaxial stretching, generally, a method of stretching in the longitudinal direction and then stretching in the transverse direction is preferably adopted.

When the film is stretched in the longitudinal and transverse directions, it may be stretched in one step, but may be stretched in multiple steps or may be provided with a heat treatment step for relaxing the orientation between the multiple steps. During or after the stretching step, in order to impart adhesiveness, antistatic ability, and releasability to the film, a coating layer is formed on one or both surfaces of the film, or a discharge treatment such as corona treatment is performed. You can also.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples and comparative examples, “parts” means “parts by weight”. The measurement methods and the definitions of terms used in the present invention are as follows.

(1) Coefficient of protrusion height distribution Three-dimensional surface roughness measuring instrument (SE-3AK) manufactured by Kosaka Laboratory Co., Ltd.
The tip radius of the stylus is 5 μm, the stylus pressure is 30 mg, the measurement length is 0.5 mm, the sampling pitch is 1.0 μm, the cutoff is 0.25 mm, the vertical magnification is 5,000 to 50,000, and the horizontal magnification is 200.
The projection height and the number of projections were measured under the conditions of 2 times and 500 operations. The projection height X (μm) referred to in the present invention is defined as the height of the surface where the number of projections (pieces / mm ² ) is the maximum, and the height from this level is defined as the projection height X, and the number of projections Y The relationship with LogY at each protrusion height X was processed by the least-squares method for data having a height of 300 or more. Then, a in logY = aX + b was set as the projection height distribution coefficient.

(2) Average roughness (Ra) Using a surface roughness measuring instrument (SE-3F) manufactured by Kosaka Laboratory Co., Ltd.
It measured according to JIS-B-0601-1982. However, the cutoff value was 80 μm and the measurement length was 2.5 mm.

(3) Film Melting Point (° C.) The film is ashed by plasma etching to obtain only a target layer. Using the obtained film as a sample film, a differential scanning calorimeter DSC7 manufactured by PerkinElmer
A mold was used. The DSC measurement conditions were as follows.
The apparatus was set in the apparatus, the temperature was raised at a rate of 10 ° C./min, and the melting point was detected.

(4) Layer Thickness A sample film is embedded in an epoxy resin, sectioned with an ultramicrotome, and the obtained thin section is observed with a scanning electron microscope to observe the cross section. The thickness was measured as (A), and the thickness of the polyester layer (B) was obtained by subtracting the polyester layer (A) from the entire thickness.

(5) Average particle size and particle size distribution of particles The inert particles contained in the polyester layer (A) are observed with a scanning electron microscope, and the maximum size and the minimum size are obtained for at least 100 particles. The arithmetic mean was defined as the number average particle size (Dn). Further, the particle diameter at a point of 50% by weight in terms of equivalent sphere was calculated as an average particle diameter (Dw). The ratio (Dw / Dn) was used as an index of the particle size distribution.

(6) Void diameter ratio In the low temperature ashing plasma apparatus, ashing is performed from the film surface to a depth of half the average particle diameter in the thickness direction, and then the average particle diameter is determined by a scanning electron microscope. Observe the particle diameter and voids formed around it for at least 100 particles that fall within ± 10% of the average particle diameter, and calculate the average of the maximum and minimum diameters of the particles and the average of the maximum and minimum diameters of the voids. Was defined as the particle diameter and the void diameter, and the void diameter ratio was determined from the following equation. Void diameter / particle diameter = void diameter ratio

(7) Abrasion resistance A fixed pin made of hard chrome having a diameter of 6 mm and fixed (material SU)
S420-J2, finish 0.2S), wrap a film of 10mm width and make contact at an angle of 135 °, speed is 11.4.
A 200 m film was run over a total of 5000 m at m / min and an initial tension of 300 g, and the amount of abrasion white powder adhering to the pins was visually evaluated and evaluated according to the rank shown below. Rank A: Not adhered at all Rank B: Adhered in a small amount Rank C: Adhered in a small amount (more than rank B) Ranks A and B are at a level that can be used without any practical problem.

(8) Transparency The internal scattered light transmittance of the film was measured using a spectroscopic turbidimeter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. In addition, it measured in the quartz cell using ethanol as a rough surface compensation solvent.

(9) Slippery Coefficient of friction Two films cut to a width of 15 mm and a length of 150 mm are stacked on a smooth glass plate, a rubber plate is placed thereon, and a weight is further placed thereon. The frictional force was measured by sliding the films at a contact pressure of 2 g / cm ² at 10 mm / min. The measurement was performed at a temperature of 23 ° C. ±
The test was performed in an atmosphere at 1 ° C. and a humidity of 50% ± 5%, and the value at the point of sliding by 2 mm was defined as the friction coefficient.

(10) Winding workability When a polyester film was produced, the film was once wound on a master roll, then slit to a predetermined width and wound up, and the film was classified into the following three ranks. A: No wrinkles were found on the winding roll, and the end faces were uniform. B: Some wrinkles were found on the winding roll, but the end faces were uniform. C: Many wrinkles were found on the winding roll, but the end faces were uniform. D: Many wrinkles are observed on the take-up roll, and the end faces are also irregular. The above-mentioned ranks A and B are levels at which there is no problem in winding workability when producing a polyester film.

(11) Heat Shrinkage Five widths 2c each in the machine direction (MD) and the transverse direction (TD) of the film.
A 100 cm long sample is cut out and 150
Heat treatment in an atmosphere of 5 ° C. for 5 minutes, measure the length of the sample before and after that, calculate the thermal shrinkage (SMD) in the longitudinal direction of the film, and the thermal shrinkage (STD) in the transverse direction by the following formulas. Five samples were measured, and the average value of SMD and STD was defined as the heat shrinkage of the film. Heat shrinkage (%) = (I0−I1) / I0 × 100 (wherein I0 is a sample length (mm) before heat treatment,
I1 means the sample length (mm) after the heat treatment. However, I0 <I1 (that is, when the film expands)
Is represented by-(minus))

Example 1 [Preparation of Raw Material Resin Containing Polyester Layer (A) Particles] Ethylene glycol was added to a water slurry of crosslinked polymer particles having an average particle size of 2.5 μm produced by seed polymerization, and heated.
Water was distilled off under reduced pressure to obtain an ethylene glycol slurry of crosslinked polymer particles. Next, 85 parts by weight of dimethyl terephthalate, 15 parts by weight of dimethyl isophthalate, 60 parts by weight of ethylene glycol, and 10 parts by weight of an ethylene glycol slurry containing 3 parts by weight of crosslinked polymer particles were placed in a reactor, and ethyl acid phosphate was used as a stabilizer and a polymerization catalyst. A polycondensation reaction was carried out by adding 0.04 part of fate and 0.04 part of antimony trioxide. The reaction initiation temperature was set to 150 ° C., and the reaction temperature was gradually increased with the distillation of methanol to 240 ° C.
The pressure gradually decreased from normal pressure, and finally 0.3
mmHg. After 5 hours from the start of the reaction, the reaction was stopped when 5 hours had elapsed, and the polymer was discharged under nitrogen pressure to obtain a raw material chip containing crosslinked polymer particles. These added particle-containing copolymerized polyesters were obtained by the same method as described above so as to obtain the added amount in the polyester layer (A) shown in Table 1 below. Blended. [Preparation of Polyester Layer (B) Raw Material Resin] Starting with 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 part by weight of magnesium acetate tetrahydrate as a catalyst was placed in a reactor, and the reaction starting temperature was adjusted. Fifteen
The temperature was raised to 0 ° C., and the reaction temperature was gradually increased with the removal of methanol, and the temperature was raised to 230 ° C. after 3 hours. After 4 hours, 10 parts by weight of an ethylene glycol slurry was added to the reaction mixture in which the transesterification reaction was substantially completed, and 0.07% of ethyl acid phosphate was used as a stabilizer and a polymerization catalyst.
4 parts and 0.04 part of antimony trioxide were added, and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from the normal pressure, and finally was 0.3 mmHg. After the reaction starts, 4
After a lapse of time, the reaction was stopped, and the polymer was discharged under nitrogen pressure to obtain a raw material chip. [Production of Film] After drying these raw material chips of polyethylene terephthalate at 170 ° C. for 3 hours, the raw material chips of the polyester layer (A) are supplied to the sub-extruder, and the raw material chips of the polyester layer (B) are supplied to the main extruder. 2
After melting at 80 ° C to 300 ° C, the molten polymer of the sub-extruder is branched into two layers, front and back, of the film. To obtain an unstretched film. At the time of casting, an electrostatic contact method was adopted. The thus-obtained two-layer and three-layer laminated unstretched film is fed to a longitudinal stretching roll, stretched 2.9 times at a film temperature of 83 ° C. (with an IR heater), and further at 97 ° C. (with an IR heater). The film was stretched twice, guided to a tenter and stretched 3.9 times in the transverse direction at 120 ° C. to obtain a biaxially oriented film. Next, the obtained biaxially oriented film is led to a heat setting zone,
Heat fixing was performed at 225 ° C. for 5 seconds while relaxing 3% in the width direction. In addition, the thickness of the polyester layer (A) was controlled by adjusting the discharge amount of the gear pump of the sub-extruder. The total thickness of the obtained laminated film was 20 μm, and the thickness of the polyester layer (A) was 4.0 μm.

Example 2 A film was obtained in the same manner as in Example 1 except that 1.2 μm crosslinked polymer particles were used.

Example 3 A film was obtained in the same manner as in Example 1 except that 2.7 μm spherical porous silica particles were used.

Example 4 Using 0.1% by weight of 10 μm spherical porous silica particles,
A film was obtained in the same manner as in Example 1 except that the thickness of the polyester layer (A) was 5.0 μm.

Comparative Example 1 A film was obtained in the same manner as in Example 1 except that spherical silica having a void diameter ratio of 3.3 and an average particle diameter of 1.5 μm was used.

Comparative Example 2 A film was obtained in the same manner as in Example 1 except that amorphous silica having an average particle size of 2.5 μm was used.

Comparative Example 3 A film was obtained in the same manner as in Example 1 except that the addition amount of Example 1 was changed to 0.003% by weight.

Comparative Example 4 The polyester layer (A) and the polyester layer (B) had a melting point of 2.
Example 1 except that polyethylene terephthalate at 60 ° C. and crosslinked polymer particles having an average particle size of 1.2 μm were used.
A film was obtained in the same manner as described above.

Comparative Example 5 The polyester layer (A) and the polyester layer (B) had a melting point of 2.
A film was obtained in the same manner as in Example 1, except that a copolymerized polyester at 10 ° C. was used.

Comparative Example 6 Polyester of terephthalic acid and hexamethylene glycol having a melting point of 154 ° C. was used for the polyester layer (A).
The film could not be formed. Table 1 shows the physical properties and properties of the thus obtained films of Examples, and Table 2 below shows the physical properties and properties of the films of Comparative Examples.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

According to the present invention, there is provided a laminated polyester film having projections of uniform height which are not easily broken, and excellent in abrasion resistance, transparency, slipperiness, workability, dimensional stability and the like. And its industrial value is high.

Continued on front page F-term (reference) 2H023 FA01 FA12 4F100 AA20 AK01A AK01C AK41A AK41B AK41C AK42 BA02 BA03 BA10A BA10C BA16 DE01A DE01C EH20 EJ05A EJ05C EJ38 GB15 CF90 JA03 JA04A04 CF051 CF061 CF071 CF081 DE236 DH046 DJ016 FA082 FA086 GG02 GS00

Claims (3)

[Claims] 1. A film in which a polyester layer (A) is laminated on at least one surface of a polyester layer (B), wherein the polyester layer (A) contains inert particles having a void diameter ratio of 2.0 or less, Melting point Tm of polyester layer (A)
A and the melting point TmB of the polyester layer (B) satisfy the following formula, the projection height distribution coefficient of at least one film surface is -10 or less, and the average roughness R of the surface is
a. The laminated polyester film, wherein a is 10 nm or more. TmB-80 ≦ TmA ≦ TmB-10 ............ 2. An inert particle having an average particle size of 1.0 to 5.0 μm.
The polyester film according to claim 1, which is a crosslinked polymer particle of m. 3. The polyester film according to claim 1, wherein the film has an internal scattered light transmittance of 2% or less and an absolute value of a thermal shrinkage of the film of 5% or less.