TW202227269A - Polyester release film - Google Patents

Abstract

This invention relates to a polyester release film, particularly to a release film for surface protection used for electronic materials such as multilayer ceramic capacitor (MLCC), polarizing plate protection and OCA. The polyester release film of this invention is a thin film and has excellent winding property and slipperiness to a roll. Pinholes are less likely to occur when a thin-film ceramic sheet is produced by applying it to a ceramic slurry.

Description

polyester release film

The invention relates to a polyester release film, in particular to a release film for surface protection of electronic materials such as Multi-layer Ceramic Condenser (MLCC), polarizer protection and OCA.

Polyester film has excellent physical property stability in a wide temperature range from low temperature to high temperature, and has excellent chemical resistance compared with other polymer resins. In addition, the uniformity of mechanical strength, surface properties, and thickness is good, and therefore, it can be applied to various applications and process conditions. Therefore, it is being used for capacitors, films, labels, pressure-sensitive tapes, decorative laminates, transfer films, polarizers, and green sheets for ceramic release, etc., and with the recent trend of high speed and automation, its Demand is increasing.

Recently, with the trend of miniaturization of electronic equipment, electronic parts such as capacitors and inductors are also miniaturized, among which, the ceramic green sheet itself is also being thinned, and the emphasis is on making the ceramic sheet into a thin film so as to have the same volume in the same volume. Laminate more ceramic layers. On the silicon release layer formed on the surface of the polyester release film, a ceramic slurry obtained by dispersing ceramic powder and a binder in a liquid phase medium is applied to produce a thin-film ceramic sheet, and then the ceramic sheet is produced. The release film is removed during the capacitor process. However, when the surface roughness of the release film is high, physical properties such as the slippage of the release film itself and the winding to a roll can be satisfied, but the protruding form of the particles protruding from the surface of the release film may be transferred to the ceramic. Problems on the sheet. In addition, when a release film is produced, when the film is transferred at a high speed while being in contact with a transfer roller, particles are detached and become chips and adhere to the roller in contact therewith to cause contamination and cause defects in the film. The chips or detached particles adhere to the transfer roller, cause defects on the film surface, and become foreign matter in the subsequent process.

Conversely, when the surface roughness of the film is too low, the coating stability, film mobility, and slippage at the time of coating the ceramic slurry decrease, and when the release film is wound on a roll after it is produced, it occurs. Rolling off phenomenon, etc., and in the process of coating the surface of the release film with a silicon release layer, scratches and the like will occur on the surface of the film.

Therefore, there is a need to develop a film-like release film which, when manufacturing a release film, reduces the surface roughness as much as possible, has excellent slip properties, and is excellent in rollability to a roll, and which generates less chips even when transferred at a high speed, and also When cutting the film, less dust is generated. prior art literature

Patent Literature Patent Document 1: Korean Patent Publication No. 2003-0055118 (2003.07.02)

technical problem

The present invention aims to provide a release film for surface protection of electronic materials such as multilayer ceramic capacitors (MLCC), polarizer protection, and OCA.

Specifically, the present invention aims to provide a polyester release film, which is a film with a thickness of 50 μm or less, so as to be used as a release film for a film-like multilayer ceramic capacitor (MLCC), and which is good for rollability and smoothness of rolls. Excellent mobility.

In addition, it is an object to provide a polyester release film in which pinholes are less generated when a ceramic slurry is applied to manufacture a thin-film ceramic sheet.

In addition, it is an object to provide a polyester release film in which, even if it is transferred at a high speed during film formation, less chips are generated and less dust is generated when the film is cut. Technical solutions

As a result of studies to solve the above-mentioned problems, the inventors have found that the above-mentioned objects can be achieved by producing a film containing particles having a bimodal shape satisfying specific physical properties, thereby completing the present invention.

An example of the present invention provides a polyester release film, which is a biaxially oriented polyester film formed by laminating one or more layers, the polyester release film includes particles on at least one surface, and the particles have particles A and B , when the fineness distribution of particles in the polyester layer containing particles is measured and plotted in such a way that the horizontal axis represents the particle diameter and the vertical axis represents the number of particles, the average particle diameters of the particles A and B satisfy the relational expression 1 and the range of the relational expression 2, the weight ratio of the particles A and the particles B satisfies the relational expression 3. 0.1μm ≤ Average particle size of particle A ≤ 0.5μm Relational formula 1 0.6μm ≤ Average particle size of particle B ≤ 1.2μm Relational formula 2 2 ≤ weight of particle A / weight of particle B Relation 3

In an example of the present invention, the relational expression 3 may be 2 ≤ weight of particle A / weight of particle B ≤ 10.

In an example of the present invention, the average particle diameters of the particles A and B may satisfy the relational expression 4. Average particle size of particle B - Average particle size of particle A ≤ 0.5μm Relation 4

In an example of the present invention, the total thickness of the release film may be 10 to 50 μm.

In one example of the present invention, the content of the particles may be 0.01 to 0.3% by weight relative to the total weight of the film.

In one example of the present invention, the particles may be one or a mixture of two or more selected from inorganic particles and organic particles.

In an example of the present invention, the inorganic particles can be selected from calcium carbonate, titanium oxide, silica, kaolin and barium sulfate, and the organic particles can be selected from silicone resin, cross-linked divinylbenzene polymethacrylic acid One or more mixtures of esters, cross-linked polymethacrylates, cross-linked polystyrene resins, benzo-substituted melamine-formaldehyde resins, benzo-substituted melamine-melamine-formaldehyde resins and melamine-formaldehyde resins.

In an example of the present invention, the inorganic particles may be silica or calcium carbonate.

In an example of the present invention, the inorganic particles may be silicon dioxide (particle A) with an average particle size of 0.1-0.5 μm and calcium carbonate (particle B) with an average particle size of 0.6-1.0 μm, and the carbonic acid The difference between the average particle size of calcium (particle B) and the average particle size of silica (particle A) may be 0.5 μm or less. beneficial effect

The polyester release film of the present invention is a film, and is excellent in rollability and slipperiness to a roll, and pinholes are less generated when a ceramic slurry is applied to produce a thin-film ceramic sheet.

In addition, it is possible to provide a polyester release film in which, even when transferred at a high speed during film formation, less chips are generated and less dust is generated when the film is cut.

Hereinafter, the present invention will be described in more detail. The following specific example or embodiment is only a reference for describing the present invention in detail, and the present invention is not limited thereto, and the present invention can be implemented in various forms.

Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by those skilled in the art. The terms used for description in the present invention are only used to effectively describe specific examples, and are not intended to limit the present invention.

Also, use of the singular in the specification and the appended claims includes the plural unless the context clearly dictates otherwise.

In addition, when a part "includes" a certain element, unless stated to the contrary, it means that other elements are not excluded, but other elements may be further included.

Hereinafter, each configuration of the present invention will be described in more detail.

In one example of the present invention, the polyester resin can be used as a masterbatch chip for producing polyester films.

The inventors of the present invention have found that when two kinds of inorganic particles having different particle diameters are mixed and used and these particles are used in combination in a specific range of size and content, it is possible to provide a film which has a flat surface and includes features for improving post-processing. The present invention has been completed with an effective protrusion of the windability of the film and the generation of less dust at the time of cutting.

In one example of the present invention, the polyester resin is not particularly limited, and commonly used polyester resins can be used. For example, it can be obtained by polycondensation of an acid component mainly composed of dicarboxylic acid and a diol component mainly composed of alkylene glycol. The above-mentioned dicarboxylic acid is not limited, and terephthalic acid, its alkyl ester, phenyl ester, etc. can be used, and a part of isophthalic acid, oxyethoxy benzoic acid, adipic acid can be used instead. , sebacic acid and difunctional carboxylic acids such as sodium isophthalic acid-5-sulfonate or their ester-forming derivatives. In addition, there is no restriction on the diol component, but ethylene glycol is mainly used, and 1,2-propanediol, neopentyl glycol, 1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanediol can be mixed and used. For example, hexanedimethanol, 1,4-dioxyethoxybenzene, bisphenol, polyoxyethylene glycol, etc., a monofunctional compound or a trifunctional compound may be partially used in combination.

In addition to this, additives commonly used when polymerizing polyester resins, that is, additives selected from the group consisting of pinning agents, antistatic agents, ultraviolet stabilizers, water repellants, slip agents, and heat stabilizers may be included. One or two or more components, but not limited thereto.

The polyester resin can be prepared by TPA (Terephthalic acid, terephthalic acid) polymerization method or DMT (dimethyl terephthalate, dimethyl terephthalate) polymerization method, etc., which are conventional polymerization methods in the art, but not limited thereto .

In one example of the present invention, the polyester resin may be polyethylene terephthalate. That is, the polyester resin may be polyethylene terephthalate prepared using Terephthalic acid as a dicarboxylic acid and using Ethylene glycol as a diol.

In addition, the polyester film of the present invention preferably contains two specific inorganic particles to reduce surface roughness and prevent coating on the release layer due to transfer of surface roughness when used as a base film for a release film Pinholes or uneven thickness occur in the layer, and at the same time, the handling (Handling) properties such as roll mobility and winding properties are improved, thereby greatly improving productivity.

More specifically, particles satisfying Relational Expressions 1 to 3 at the same time may be contained.

Specifically, the particles have particles A and B, and when the fineness distribution of the particles in the polyester layer containing the particles is measured and plotted in such a manner that the horizontal axis represents the particle diameter and the vertical axis represents the number of particles, the particle The average particle diameters of the particles A and B satisfy the ranges of the relational expressions 1 and 2, and the weight ratio of the particles A and the particles B satisfy the relational expressions 3. 0.1μm ≤ Average particle size of particle A ≤ 0.5μm Relational formula 1 0.6μm ≤ average particle size of particle B ≤ 1.2μm Relational formula 2 2 ≤ weight of particle A / weight of particle B Relation 3

That is, the relational expressions 1 and 2 indicate that the particle diameters have one or more average particle diameters in the ranges of 0.1 to 0.5 μm and 0.6 to 1.2 μm, respectively, and the relational expression 3 may have the above-mentioned range of 0.1 to 0.5 μm. The content ratio (weight ratio, weight of particle A/weight of particle B) of particles A having an average particle diameter of 0.6 to 1.2 μm and particle B having an average particle diameter in the range of 0.6 to 1.2 μm is 2 or more, 3 or more, more specifically 2 to 10, 2 to 11, 3 to 10, 3 to 11, 3 to 11.5.

As long as the above-mentioned relational expressions 1 to 3 are satisfied at the same time, a polyester release film can be provided as intended, which is a film, which is excellent in rollability and slipperiness to a roll during film formation, and is smooth Because of its excellent properties, pinholes are less generated when a ceramic slurry is applied to produce a thin-film ceramic sheet.

That is, it is possible to provide a film that simultaneously satisfies smoothness, slipperiness, and windability which are in a trade-off relationship with each other. Specifically, it is possible to provide a film which has a flat surface and includes effective protrusions for improving post-processing and film rollability, and which can reduce pinholes and short circuits in multilayer ceramic capacitors due to transfer surface roughness (MLCC Short) defective rate.

In addition, it is possible to provide a polyester release film in which, even when transferred at a high speed during film formation, less chips are generated and less dust is generated when the film is cut.

In addition, the average particle diameters of the particles A and B may satisfy the relational expression 4. Average particle size of particle B - Average particle size of particle A ≤ 0.5μm Relation 4

As shown in the relational expression 4, the difference between the above-mentioned average particle diameter of 0.1 to 0.5 μm and the average particle diameter in the range of 0.6 to 1.2 μm is 0.5 μm or less, more specifically, 0.1 to 0.5 μm. Within the above range, the surface smoothness is more excellent, the generation of pinholes can be further reduced when used in ceramic capacitors, and the content of chips can be reduced when the film is cut to reduce the generation of foreign matter.

In one example of the present invention, the particles may be one or a mixture of two or more selected from inorganic particles and organic particles.

The inorganic particles are selected from calcium carbonate, titanium oxide, silicon dioxide, kaolin, barium sulfate, etc., and the organic particles can be selected from silicone resin, cross-linked divinyl benzene polymethacrylate, cross-linked polymethyl methacrylate, etc. One or more mixtures of acrylates, cross-linked polystyrene resins, benzo-substituted melamine-formaldehyde resins, benzo-substituted melamine-melamine-formaldehyde resins, and melamine-formaldehyde resins, etc., but not limited thereto.

Preferably, the particles can be mixed with particles A having an average particle diameter of 0.1-0.5 μm and particles B having an average particle diameter of 0.6-1.2 μm. In addition, the difference between the average particle diameter of the particles B and the average particle diameter of the particles A may be 0.5 μm or less, and more specifically, may be 0.1 to 0.5 μm.

More preferably, the particles may be silica particles (particles A) with an average particle size of 0.1-0.5 μm and calcium carbonate (particles B) with an average particle size of 0.6-1.2 μm. In addition, the difference between the average particle size of the calcium carbonate (particles B) and the average particle size of the silica particles (particles A) may be 0.5 μm or less, more specifically, 0.1 to 0.5 μm.

In one example of the present invention, the content of the particles may be 0.01 to 0.3 wt %, preferably 0.05 to 0.25 wt %, and more preferably 0.1 to 0.2 wt % relative to the total weight of the film. Within the above range, it is possible to provide a film which is excellent in particle dispersibility, prevents particle aggregation, and reduces generation of chips.

In one example of the present invention, when the particles are added in the form of a particle slurry dispersed in a diol component when synthesizing a polyester resin, the dispersibility is excellent and reaggregation between particles can be prevented, so it is effective, but Not limited to this. That is, it may be added from the end of the esterification reaction or the transesterification reaction to before the start of the polycondensation reaction, but is not limited thereto.

The polyester release film of one example of the present invention is a biaxially oriented polyester film in which one or more layers are laminated, and contains particles satisfying the above-mentioned relational expressions 1 to 3 on at least one surface.

Specifically, for example, it may be a biaxially oriented polyester film in which two or three layers are laminated, and in which at least one surface contains particles satisfying the relational expressions 1 to 3.

More preferably, it may be a biaxially oriented polyester film in which three or more layers are laminated, and at least one surface layer may contain particles satisfying the above-mentioned relational expressions 1 to 3. It is formed by laminating three or more layers, and within the range that does not affect the roughness of the surface layer, in the inner layer part, the recovered raw material of the edge portion generated in the film forming process or the recycled raw material of other film forming process is mixed in the inner layer part. , reuse, thereby reducing prices while reusing resources.

The biaxial stretching means that a pattern of biaxial orientation is exhibited by X-ray diffraction. The stretching may be successive biaxial stretching, which may be achieved by performing a process of stretching in the length direction (longitudinal direction) and then stretching in the width direction (transverse direction). By performing biaxial stretching in this way, the strength and crystallinity in the lengthwise and widthwise directions can be made uniform, and cutting can be efficiently performed in all directions.

The polyester release film of an example of the present invention satisfies the above-mentioned relational expressions 1 to 3, and therefore, it is possible to provide a film based on JIS B-0601 using a surface roughness measuring instrument (Tokyo seimitsu, Surfcom 590A- 3DF-12) The surface roughness peak count Pc measured is 2.0 pieces/mm ² or less, and more specifically, 0.1 to 2 pieces/mm ² or less. Within the above-mentioned range, the surface roughness can be reduced while the windability and mobility can be satisfied, and therefore, a film with improved productivity can be provided, which is preferable, but not limited to this.

The polyester release film of an example of the present invention may have a centerline average surface roughness Ra measured by a contact three-dimensional surface roughness meter with a cutoff value of 0.08 mm of 20 nm or less, more preferably 15 nm or less. Specifically, the centerline average surface roughness Ra may be 1 to 20 nm, and more specifically, 4 to 15 nm. Within the above range, a film can be provided which has a low surface roughness and thus is excellent in smoothness, and which hardly generates pinholes when used as a release film for MLCC, which is preferable, but not limited thereto.

The total thickness of the release film may be 10-50 μm, more specifically, 20-40 μm. Within the above range, it can be sufficiently used as a base film for a release film, but is not limited thereto. Since the polyester film used as the base film of the release film for MLCC shows the tendency for the thickness to be continuously reduced in use, it is suitable to be used in the above-mentioned range. In addition, when three or more layers are stacked, the core layer and the skin layers formed on both sides thereof may be formed, and the thickness ratio of the core layer to the skin layer may be 50%:50% to 90%:10%, more preferably 60%:10% 40% to 80%: 20%. Within the above range, it is possible to provide a film which is excellent in mobility, excellent in slippage, improved in windability to a roll, and less generation of chips, which is preferable.

In one example of the present invention, the polyester film may be a biaxially stretched film. Specifically, the polyester film may be biaxially stretched by stretching 3 to 5 times in the machine direction and 4 to 6 times in the width direction. Within the above stretching ratio, the thermal dimensional stability of the polymer structure can be further improved, thereby reducing thermal shrinkage, which is preferable, but not limited to this.

In an example of the present invention, the polyester film may be heat-treated at 200˜250° C. and relaxed by 1% to 10% after biaxial stretching. Specifically, it may be relaxed while being heat-treated, more specifically, it may be relaxed by 1% to 10% in the width direction, and more specifically, it may be relaxed by 2% to 4%. Within the above range, the film can be kept in a state of tension in the width direction to improve the density of the polymer structure and reduce thermal deformation, which is preferable, but not limited to this.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following Examples and Comparative Examples are merely examples for illustrating the present invention in more detail, and the present invention is not limited to the following Examples and Comparative Examples.

Hereinafter, physical properties were evaluated in the following manner.

[The average particle size]

The measurement was performed using a fineness distribution measuring instrument (LS13 320 from Beckman Corporation).

[Surface Roughness (Ra)]

Based on JIS B-0601, after slicing the left/center/right three positions of the polyester film, a three-dimensional surface roughness measuring instrument (Tokyo seimitsu, Surfcom 590A-3DF-12) was used at a measuring speed of The measurement was performed under the conditions of 0.03 mm/sec, a stylus radius of 2 μm, a load of 0.7 mm/N, a measurement area of 1.0 mm ² , and a cutoff value of 0.08 mm.

Taking the x-axis as the center line and the y-axis as the vertical direction, the roughness curve is represented by y=f(x). At this time, the calculation is performed by the following formula.

Among them, L: reference length (Cut-Off).

[winding yield]

The polyester films produced in Examples and Comparative Examples were evaluated as follows by calculating the ratio of the production amount to the input amount at the time of production. Winding yield (%) = (product production / input) × 100 ◎: When the yield is 65% or more ○: When the yield is 55% or more and less than 65% △: When the yield is less than 55%

[degree of chip generation]

The produced film was cut into a width of 500 mm at a speed of 300 m/min, and the presence or absence of particles caused by PET chips of the cut 500 mm film roll was confirmed ^on the surface of the film roll, and the setting was as follows: When the number of particles is 0, it is grade 1, 1 to 3 are grade 2, 4 to 6 are grade 3, 7 to 9 are grade 4, 10 to 12 are grade 5, and more than 13 are grade 5. Level 6, of which, Level 1 and Level 2 are qualified, and the rest are unqualified.

[Production yield]

A master roll of the polyester film produced in the Examples and Comparative Examples was used as a base film, and after the silicon release layer was formed, a ceramic slurry was applied to manufacture a ceramic green sheet having a thickness of 1.5-3.0 μm. At this time, the following evaluation was performed based on whether or not pinholes were generated. The production yield is the ratio of the area of the final produced ceramic green sheet to the area of the parent roll of one roll of polyester film supplied. Production yield (%) = (area of ceramic green sheet / area of parent roll of one roll of polyester film) × 100 Excellent: No pinholes for a parent roll of polyester film Good: For a master roll of polyester film, pinholes occurred in a part, and the production yield was 70% or more Ordinary: For the parent roll of one roll of polyester film, pinholes are generated in a part, and the production yield is more than 30% Defect: For a master roll of polyester film, most of the pinholes are generated, and the production yield is less than 30%

[Example 1]

1) Preparation of polyester chips (1)

With respect to 100 parts by weight of dimethyl terephthalate, 50 parts by weight of ethylene glycol, 400 ppm of magnesium acetate, 200 ppm of calcium acetate, and 150 ppm of antimony trioxide were put into the esterification reactor, and after that, from A transesterification reaction was carried out at room temperature to 230 °C for 4 hours to prepare the prepolymer bis-β-hydroxyethyl terephthalate (BHET), in which magnesium acetate and calcium acetate were used as electrostatic pinning agents, Antimony trioxide was used as a polymerization catalyst. The by-product methanol produced in the reaction flows out of the reactor and is separated by a distillation column, and the additionally produced ethylene glycol after the esterification reaction is completed is also separated by a distillation column. At this time, after adding 200 ppm of trimethyl phosphate as a thermal stabilizer, the pressure was reduced to 0.3 torr while the temperature was slowly raised to 285°C. The polycondensation reaction was carried out under high vacuum for 4 hours to produce polyethylene terephthalate (PET) resin chips with an intrinsic viscosity of 0.630 dL/g.

2) Preparation of polyester chips (2)

To the polyester chip (1), 1% by weight of silica (particle A) having an average particle diameter of 0.3 μm was added and melt-extruded using a biaxial kneader to prepare a polyester chip (2).

3) Preparation of polyester chips (3)

To the polyester chip (1), 1% by weight of calcium carbonate (particle B) having an average particle diameter of 0.7 μm was added and melt-extruded using a biaxial kneader to prepare a polyester chip (3).

4) Film making

The core layer uses a polyethylene terephthalate (PET) chip (1) that does not contain inorganic particles, and the surface layer uses the polyethylene terephthalate (PET) chip mixed with the content shown in Table 1 (1), polyester chips (2), and polyester chips (3).

Coextruded as a skin/core/skin three-layer film laminated and cast on chill rolls to make unstretched sheets. At this time, the above-mentioned core layer occupies 80% by weight of the total weight of the film, and the skin layer occupies 20% by weight of the total weight of the film.

After melt extrusion by an extruder, rapid cooling and solidification were performed with a casting drum having a surface temperature of 20° C. to manufacture a sheet. The resulting sheet was stretched 3.5 times in the machine direction and 4.0 times in the transverse direction at 95°C, and heat-treated at 230°C, and finally produced a film with a particle content of 0.2 wt % and a thickness of 31 μm biaxially oriented film. The thickness of the core layer was 24.8 μm, and the thickness of the surface layers was 3.1 μm, respectively. The physical properties of the produced films were measured and shown in Table 2.

[Examples 2 to 6]

As shown in Table 1, a film was formed in the same manner as in Example 1 except that the content ratio of the particles was adjusted. The physical properties of the produced films were measured and shown in Table 2.

[Comparative Example 1]

As shown in Table 1, a film was formed in the same manner as in Example 1 except that the content ratio of the particles was adjusted. The physical properties of the produced films were measured and shown in Table 2.

[Comparative Example 2]

A film was formed in the same manner as in Example 1, except that the polyester chip (4) was used instead of the polyester chip (3) in Example 1. The physical properties of the produced films were measured and shown in Table 2.

The polyester chip (4) was melt-extruded by adding 1% by weight of cross-linked polystyrene particles (particles B) having an average particle diameter of 1.0 μm to the polyester chip (1) and using a biaxial kneader to prepare polyester chips (4). Table 1 Content ratio in the surface layer (% by weight) Weight of Particle A / Weight of Particle B Average particle size of particle B - Average particle size of particle A (μm) Film thickness (μm) slice (1) slice (2) slice (3) Example 1 80 15 5 3 0.4 31 Example 2 88 10 2 5 0.4 31 Example 3 83 15 2 7.5 0.4 31 Example 4 80 18 2 9 0.4 31 Example 5 45 50 5 10 0.4 31 Example 6 85 10 5 2 0.4 31 Comparative Example 1 87 12 1 12 0.4 31 Comparative Example 2 80 15 5 (slices (4)) 3 0.7 31 Table 2 Winding yield (%) degree of chip generation production yield Surface roughness Ra (nm) Example 1 ◎ Level 1 good 10 Example 2 ◎ Level 1 good 11 Example 3 ◎ Level 1 good 12 Example 4 ◎ Level 1 good 13 Example 5 ◎ Level 1 good 14 Example 6 ◎ Level 1 good 18 Comparative Example 1 △ Level 3 ordinary 20 Comparative Example 2 △ level 4 bad twenty four

As shown in Table 2, even if two kinds of particles were used, when the particle size ratio between the particles and the bimodal fineness distribution were outside the scope of the present invention, the production yield was poor. In addition, it was confirmed that the chips increased, the winding yield decreased, and the surface roughness increased.

In conclusion, the present invention has been described through specific matters and limited embodiments, but this is only for helping a more comprehensive understanding of the present invention, the present invention is not limited to the above-mentioned embodiments, and those skilled in the art can Records undergo various modifications and variations.

Therefore, the idea of the present invention is not limited to the described embodiments, and the appended claims and their equivalents and equivalent modifications all belong to the scope of the idea of the present invention.

Claims (9)

A polyester release film, which is a biaxially stretched polyester film formed by laminating more than one layer, characterized in that: The polyester release film contains particles on at least one surface, and the particles have particles A and B. When measuring the fineness distribution of the particles in the polyester layer containing the particles, the horizontal axis represents the particle diameter and the vertical axis. When plotting in the manner of representing the number of particles, the average particle diameters of the particles A and B satisfy the relational formula 1 and the relational formula 2, and the weight ratio of the particles A and the particles B meets the relational formula 3, 0.1μm ≤ Average particle size of particle A ≤ 0.5μm Relational formula 1 0.6μm ≤ average particle size of particle B ≤ 1.2μm Relational formula 2 2 ≤ the weight of particle A / the weight of particle B Relation 3. The polyester release film according to claim 1, wherein, The relational formula 3 is, 2 ≤ weight of particle A / weight of particle B ≤ 10. The polyester release film according to claim 1, wherein, The average particle diameters of the particles A and B satisfy the relational formula 4, The average particle size of particles B - the average particle size of particles A ≤ 0.5μm Relation 4. The polyester release film according to claim 1, wherein, The total thickness of the release film is 10-50 μm. The polyester release film according to claim 1, wherein, The content of the particles is 0.01 to 0.3% by weight relative to the total weight of the film. The polyester release film according to claim 1, wherein, The particles are a mixture of one or two or more selected from inorganic particles and organic particles. The polyester release film according to claim 6, wherein, The inorganic particles are selected from calcium carbonate, titanium oxide, silicon dioxide, kaolin and barium sulfate, and the organic particles are selected from silicone resin, cross-linked divinyl benzene polymethacrylate, cross-linked polymethacrylate , one or more mixtures of cross-linked polystyrene resins, benzo-substituted melamine-formaldehyde resins, benzo-substituted melamine-melamine-formaldehyde resins and melamine-formaldehyde resins. The polyester release film according to claim 7, wherein, The inorganic particles are silica or calcium carbonate. The polyester release film according to claim 8, wherein, The inorganic particles are silicon dioxide (particle A) with an average particle size of 0.1-0.5 μm and calcium carbonate (particle B) with an average particle size of 0.6-1.0 μm, The difference between the average particle size of the calcium carbonate (particles B) and the average particle size of the silica (particles A) is 0.5 μm or less.