JPH1086304A - Complexed release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film suitable for a green sheet having no burr at the time of punching a through hole in the case of forming a ceramic board, for example, according to a green sheet multilayer laminating process and excellent punchability. SOLUTION: The film comprises at least two layers of polyester laminated by coextruding, and a release layer provided on at least one side surface of the laminated polyester film for simultaneously satisfying following formulae: 0.5<=[η]<=0.60, 0.1<=d50 <=1, and 5<=WA<=20, where [η] is a limiting viscosity of the laminated polyester film, d50 is mean particle size (μm) of particle contained in at least one layer of the polyester film, and WA is adding amount (wt.%) of the particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release film suitable for use as a green sheet, and more particularly, to the production of a ceramic substrate by a multilayer lamination method of a green sheet without the occurrence of burrs or the like when punching through holes. And a release film for green sheets having improved punching properties.

[0002]

2. Description of the Related Art In the field of semiconductor integrated circuit manufacturing,
With the increase in density, fine patterning and multilayering are required. Through-holes are required for multilayering,
Further, in order to increase the density, it is necessary to further narrow the through-holes together with finer patterns.

The through holes are filled with a conductive paint to form a conductive circuit between the laminations. However, when a polyester film is used as a release film, burrs are generated at the time of punching the through holes, so that good through holes cannot be obtained. There is a problem. That is, the generation of burrs hinders the filling of the conductive paint, particularly in the case of a narrow through hole, and causes an increase in the defective rate. Further, there is also a problem that the generated burrs damage the green sheet and change the size of the through hole.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to eliminate the generation of burrs and the like when punching through holes when a ceramic substrate is formed by a green sheet multilayer lamination method. An object of the present invention is to provide a green sheet release film having good punching properties.

[0005]

That is, the gist of the present invention is to provide a film comprising at least two layers of polyester laminated by co-extrusion and simultaneously satisfying the following formulas (1) to (3). The composite release film has a release layer provided on at least one surface of the laminated polyester film.

[0006]

## EQU3 ## Polyester film laminated by co-extrusion consisting of at least two layers 0.53 ≦ [η] ≦ 0.60 (1) 0.1 ≦ d ₅₀ ≦ 1 (2) 5 ≦ WA ≦ 20 (3) (where [η] is the limiting viscosity of the laminated polyester film, d ₅₀ is the average particle diameter (μm) of the particles contained in at least one layer of the laminated polyester film, and WA is (Indicates the amount (% by weight) of the particles)

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The laminated polyester film referred to in the present invention is a film extruded by a so-called co-extrusion method in which all layers are melt-extruded together from an extrusion die. It consists of a film oriented in the axial direction.

In the present invention, the polyester constituting each laminated layer may be a homopolyester or a copolyester. In the case of a homopolyester, such a polyester is obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol,
4-cyclohexanedimethanol and the like. Typical polyesters include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN).

On the other hand, in the case of a copolyester, 30
It is a copolymer containing not more than mol% of a third component. Examples of the dicarboxylic acid component of the copolymerized polyester include isophthalic acid, terephthalic acid phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and one of oxycarboxylic acids (for example, P-oxybenzoic acid). Alternatively, two or more kinds may be mentioned, and as the glycol component, one or more kinds of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like may be mentioned. In the present invention, the intrinsic viscosity of the laminated polyester film constituting the composite release film needs to satisfy the following formula (1).

[0010]

0.53 ≦ [η] ≦ 0.60 (1) (in the above formula, [η] represents the intrinsic viscosity of the laminated polyester film)

In the present invention, when the intrinsic viscosity of the laminated polyester film exceeds 0.60, the effect of improving the punching property of the green sheet is insufficient. On the other hand, when the intrinsic viscosity is less than 0.53, the film is not formed. In a difficult situation, it is not practically preferable. In the present invention, it is necessary that at least one of the layers constituting the laminated polyester film contains particles. The average particle size of the particles and the amount added thereof must satisfy the following expressions (2) and (3) simultaneously.

[0012]

0.1 ≦ d ₅₀ ≦ 1 (2) 5 ≦ WA ≦ 20 (3) (In the above formula, d ₅₀ is the particle content of the particles contained in at least one layer of the laminated polyester film. Average particle size (μm), W
A represents the amount (% by weight) of the particles added)

When the average particle diameter of the contained particles is less than 0.1 μm, the particles are liable to aggregate in the slurry. On the other hand, when the particles having an average particle diameter exceeding 1 μm are added, the surface of the layer to which the particles are added is added. The roughness becomes rough, and the surface roughness of the layer on which the release layer is provided is roughened. As a result, the surface of the resulting green sheet is unlikely to be smooth. If the amount of the particles contained is less than 5% by weight, the resulting composite release film has a high elongation at break, and as a result, burrs are likely to occur when punching through holes. On the other hand, when the added amount of the particles exceeds 20% by weight, the mechanical strength of the film decreases.

The types of particles contained in the laminated polyester film include silica, calcium carbonate, kaolin,
Examples include particles such as titanium oxide. The method for blending the particles with the polyester is not particularly limited, and a known method can be employed. For example, it can be added at any stage of producing the polyester,
Preferably, the polycondensation reaction may be carried out by adding as a slurry dispersed in ethylene glycol or the like at the stage of esterification or after the end of the transesterification reaction and before the start of the polycondensation reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a polyester material using a kneading extruder with a vent, or a method of blending the dried particles with a polyester material using a kneading extruder, etc. Done.

On the other hand, in the composite release film according to the present invention, the amount of particles added to the layer on the side where the release layer is provided is preferably less than 1% by weight. 1% by weight of particles added to this layer
When it exceeds, when the release layer is provided thereon, the surface of the release layer may not be easily smoothed. In the present invention, the center line average roughness (Ra) of the release layer surface preferably satisfies the following expression (4).

[0016]

## EQU6 ## 0.03 ≦ Ra ≦ 0.1 (4)

In particular, when the composite release film of the present invention is used for producing a green sheet, if the center line average roughness Ra of the surface provided with the release layer is less than 0.03 μm, the film formability of the film becomes stable. They tend to lack sex. On the other hand, the above R
If a exceeds 0.1 μm, the resulting green sheet surface may not have sufficient smoothness. In the case where the release layer is provided only on one surface, Ra of the surface on which the release layer is not provided may be more than 0.1 μm. Ra preferably satisfies the above expression (5), and both values do not necessarily have to be the same.

The composite release film of the present invention may have any thickness as long as it can be formed as a film.
To 350 μm, preferably 50 to 188 μm. When the particle content is reduced in consideration of the smoothness of the surface of the release layer, the thickness of the polyester layer on the side on which the release layer is provided is 50% or less, preferably 30% or less, of the total thickness of the film. Preferably, 10% or less is suitable for use. If it exceeds 50%, since the particle content of the layer on the side where the release layer is provided is small, the elongation at break of the obtained composite release film itself becomes large, and burrs are formed when punching through holes. It tends to occur easily.

Next, the method for producing a laminated biaxially oriented polyester film in the present invention will be specifically described.
The film of the present invention is not limited to the following production examples. That is, using the polyester raw material described above, using a plurality of extruders, a multi-layer multi-manifold die or a feed block, laminating each polyester and extruding a multi-layer molten sheet from a die,
A method of obtaining an unstretched sheet by cooling and solidifying with a cooling roll is preferred. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum, and the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

Next, the obtained unstretched film is stretched biaxially to be biaxially oriented. That is, first, the unstretched sheet is stretched in one direction by a roll or a tenter-type stretching machine. The stretching temperature is usually 70 to 120
° C, preferably 80 to 110 ° C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, stretching is performed in a direction orthogonal to the stretching direction of the first stage. The stretching temperature is usually 70 to 120 ° C, preferably 80 to 11 ° C.
The stretching ratio is usually 3.0 to 7 times, and preferably 3.5 to 6 times. And then, 130-2
Heat treatment is performed at a temperature in the range of 50 ° C. under a relaxation of 30% or less to obtain a biaxially stretched film.

A so-called in-line coating for treating the film surface during the stretching step can be applied. Although it is not limited to the following, for example, after the first-stage stretching is completed and before the second-stage stretching, the antistatic property, the slipperiness, the adhesiveness, and the like are improved, and the secondary workability is improved. For the purpose of the above, a coating treatment of an aqueous solution, an aqueous emulsion, an aqueous slurry or the like can be performed.

In the above stretching, the stretching in one direction is 2
It is also possible to use a method of performing the above steps. In that case,
It is preferable that the stretching is performed in such a manner that the stretching ratio in the two directions finally falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area magnification becomes 10 to 40 times. Further, if necessary, the film may be stretched in the longitudinal and / or transverse directions again before or after the heat treatment. Further, various stabilizers, ultraviolet absorbers, lubricants, pigments, antioxidants, plasticizers and the like may be added to the polyester film. In the composite release film of the present invention, the elongation at break (%) in the β-axis and γ-axis directions preferably satisfies the following expression (4).

[0023]

100 ≦ EBβ + EBγ ≦ 200 (5) (wherein EBβ and EBγ are elongation at break (%) in the β-axis and γ-axis directions of the film, respectively, and Ra is the center of the surface of the release layer. (Indicates linear average roughness (μm))

When the total elongation at break in the β-axis and γ-axis directions is less than 100%, the film itself is brittle, and the film tends to be easily broken at the time of punching through holes. On the other hand, if it exceeds 200%, burrs may be generated when punching through holes. In addition, after satisfying the above expression (5), it is preferable from the viewpoint of application that the difference between the absolute values of the elongation at break in the γ-axis direction and the β-axis direction is in the range of 0 to 40%. In the present invention, the resin used for the release layer is mainly composed of a curable silicone resin, and the types thereof are a solvent addition type, a solvent condensation type, a solvent ultraviolet curing type, a solventless addition type, a solventless condensation type, and a solventless ultraviolet curing type. And any curing reaction type such as a solvent-free electron beam curing type.

Specific examples of the silicone curable resin used in the present invention include KS-774 manufactured by Shin-Etsu Chemical Co., Ltd.
KS-775, KS-778, KS-779H, KS-
856, X-62-2422, X-62-2461, K
NS-305, KNS-3000, X-62-125
6. DKQ3-20 manufactured by Dow Corning Asia Co., Ltd.
2, DKQ3-203, DKQ3-204, DKQ3-
205, DKQ3-210, Y made by Toshiba Silicone Co., Ltd.
SR-3022, TPR-6700, TPR-672
0, TPR-6721 and the like.

In the present invention, a conventionally known coating method such as bar coating, reverse roll coating, gravure coating, rod coating, air doctor coating, doctor blade coating, etc. is used as a method for providing a cured silicone resin coating on the laminated polyester film. Can be used.
The thickness of the release layer containing a curable silicone resin as a main component,
0.01 to 5 μm is preferable from the viewpoint of coatability. When the thickness of the release layer is less than 0.01 μm, stability is lacking, and it tends to be difficult to obtain a uniform coating film. On the other hand, when the thickness exceeds 5 μm, a problem may occur in practical use. .

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. In the Examples and Comparative Examples, “parts” means “parts by weight” as a solid component. The evaluation method used in the present invention is as follows.

(1) Method for Measuring Average Particle Diameter (d ₅₀ ) A small piece of film was fixed and molded with an epoxy resin, cut with a microtome, and the cross section in the longitudinal direction of the film was observed with a transmission electron microscope. The maximum diameter of the particles present in the film is determined by a line drawn in parallel with the film surface and is defined as Dmax. The maximum diameter orthogonal to the line is defined as Dmin. Was calculated. Particle diameter (diameter) = (Dmax + Dmin) / 2 The average particle diameter of the particle group is determined for at least 100 of the above particle diameters. The particle size was used.

(2) Measurement method of intrinsic viscosity [η] 1 g of a sample film was treated with phenol / tetrachloroethane =
It was dissolved in 100 ml of a 50/50 (weight ratio) mixed solvent and measured at 30 ° C. (3) Evaluation of ceramic slurry coatability The state immediately after the ceramic slurry was coated on the release film was visually observed and evaluated according to the following criteria. << Judgment Criteria >> 〇: Good coatability △: Occurrence of coating unevenness (level that does not cause a problem in practical use) ×: Occurrence of coating unevenness (level that causes a problem in practical use)

(4) Evaluation of punching property of through hole “2HOLE PUNCH N” manufactured by Lion Corporation
o. Sample No. 35 was punched out from the sample film, and the punched-out portion was observed at a magnification of 200 times with a digital microscope “VH-6200” manufactured by KEYENCE CORPORATION, and evaluated by the following three-step evaluation. << Judgment Criteria >> ：: Burr is not observed 〇: Burr is hardly observed △: Burr is observed (level that does not cause a problem in practical use) ×: Burr is observed (level that causes a problem in practical use)

(5) Determination of γ-axis and β-axis of sample film Nomura Trading Co., Ltd. “SONIC SHEET TESTER”
Using a “SST-250 type”, a sample film was placed on a turntable, and the propagation speed in the plane direction was measured while rotating. From the measurement results, the direction in which the propagation velocity shows the maximum value was defined as the γ-axis, and the direction orthogonal thereto was defined as the β-axis.

(6) Evaluation method for elongation at break Tensile tester ("Intesco Model 2" manufactured by Intesco Corporation)
001 ”), at a temperature of 23 ° C. and a humidity of 50% RH, a chuck distance of 50 mm and a width of 10 mm.
Was pulled at a speed of 500 mm / min, and the tensile elongation at break was determined from the stress-strain curve by the following formula. In the formula, L indicates the distance between the chucks at the time of breaking, and L ₀ indicates the distance between the chucks. Tensile elongation at break (%) = [(L−L ₀ ) / L ₀ ] × 100

(7) Method of Evaluating Surface Roughness (Ra) The surface roughness was determined to have the center line average roughness Ra (μm) of the release surface. Surface roughness tester manufactured by Kosaka Laboratory Co., Ltd. (SE-
3F), and measured according to JIS-B-0601-1982. However, the cutoff value was 80 μm, and the measurement length was 2.5 mm. (8) After pasting the one surface of double-sided adhesive tape (manufactured by Nitto Denko, "No.502") to the silicone layer of the peelable (F _A) Evaluation sample, 50 mm ×
After cutting to 300 mm, the peel force after leaving for 1 hour was measured. The peeling force was measured using a tensile tester ("Intesco Model 2001" manufactured by Intesco Corporation) under the condition of a tensile speed of 300 mm / min.

Production Example 1 (Polyester A) 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off. The temperature was raised to 230 ° C. over 4 hours from the start of the reaction, and the transesterification was substantially completed. Next, 10 parts of silica particles having an average particle size of 1 μm,
After adding 0.04 part of phosphoric acid and 0.04 part of antimony trioxide, the temperature is 280 ° C. and the pressure is 15 mmHg in 100 minutes.
And then gradually reduce the pressure until finally 0.05mm
Hg. Four hours later, utilizing the correlation between the torque of the stirring blade of the polymerization tank and the degree of polymerization, the reaction was stopped when it was determined that the torque of the stirring blade reached the target intrinsic viscosity,
The pressure in the system was returned to normal pressure, and polyester A was obtained. Polyester A had a silica particle content of 10% by weight.

Production Example 2 (Polyester B) Polyester B was prepared in the same manner as in Production Example 1 except that 10 parts of silica particles having an average particle size of 1 μm were not added.
I got Production Example 3 (Polyester C) 70 parts of the polyester B obtained in Production Example 2 and 30 parts of titanium oxide particles having an average particle diameter of 1.0 μm were dry-blended and extruded using a twin-screw kneading extruder to obtain a polyester. C was obtained. The content of titanium oxide particles in Polyester C was 30% by weight.

Production Example 4 (Polyester D) 95 parts of the polyester B obtained in Production Example 2 and 20 parts of calcium carbonate particles having an average particle diameter of 0.1 μm were dry-blended, and the mixture was extruded using a twin-screw kneading extruder. Extrusion gave polyester D. The content of the calcium carbonate particles in the polyester D was 20% by weight.

Production Example 5 (Polyester E) 80 parts of the polyester B obtained in Production Example 2 and 5 parts of calcium carbonate particles having an average particle size of 1 μm were dry-blended and extruded using a twin-screw kneading extruder. Polyester E was obtained. The content of the calcium carbonate particles in the polyester E was 5% by weight.

Production Example 6 (Polyester F) Instead of adding 10 parts of silica particles having an average particle diameter of 1 μm to the polyester A obtained in Production Example 1, 10 parts of titanium oxide particles having an average particle diameter of 0.5 μm are added. A polyester F was obtained in the same manner as in Production Example 1 except for the above. The content of titanium oxide particles in Polyester F was 10% by weight.

Production Example 7 (Polyester G) Instead of adding 10 parts of silica particles having an average particle diameter of 1 μm to the polyester A obtained in Production Example 1, 20 parts of titanium oxide particles having an average particle diameter of 0.05 μm are added. A polyester G was obtained in the same manner as in Production Example 1 except for the above. The content of the titanium oxide particles in the polyester G was 20% by weight.

Production Example 8 (Polyester H) Instead of adding 10 parts of silica particles having an average particle diameter of 1 μm to the polyester A obtained in Production Example 1, 10 parts of titanium oxide particles having an average particle diameter of 1.5 μm are added. A polyester H was obtained in the same manner as in Production Example 1 except for the above. The content of titanium oxide particles in Polyester H was 10% by weight.

Production Example 9 (Polyester I) Instead of adding 10 parts of silica particles having an average particle diameter of 1 μm to the polyester A obtained in Production Example 1, 3 parts of titanium oxide particles having an average particle diameter of 0.5 μm are added. A polyester I was obtained in the same manner as in Production Example 1 except for the above. The content of titanium oxide particles in Polyester I was 3% by weight.

Production Example 10 (Polyester J) Instead of adding 10 parts of silica particles having an average particle diameter of 1 μm to the polyester A obtained in Production Example 1, 15 parts of titanium oxide particles having an average particle diameter of 0.5 μm are added. A polyester J was obtained in the same manner as in Production Example 1 except for the above. The content of the titanium oxide particles of the polyester J is 15% by weight,
The intrinsic viscosity [η] was 0.50.

<Production of Polyester Film> Production Example 11 (Polyester Film F1) After separately blending polyester B and polyester A,
Dry at 180 ° C. for 4 hours in an inert gas atmosphere, melt extrude at 290 ° C. by a separate melt extruder, combine these polymers in a feed block and laminate, and apply the surface temperature using the electrostatic application adhesion method. Was cooled and solidified on a cooling roll set at 40 ° C. to obtain a laminated unstretched sheet. The obtained sheet was stretched 3.8 times in the longitudinal direction at 85 ° C. Next, the film was guided to a tenter and stretched 3.6 times in the transverse direction at 125 ° C., and then heat-set at 230 ° C. to obtain a laminated polyester film of 75 μm. The layer configuration was B / A, and the thickness of each layer was 20/55 (μm).

Production Example 12 (Polyester film F2) A laminated polyester film of 75 μm was obtained in the same manner as in Production Example 11, except that Polyester C was used instead of Polyester A. The layer structure was B / C, and the thickness of each layer was 10/65 (μm). Production Example 13 (Polyester Film F3) A laminated polyester film of 75 μm was obtained in the same manner as in Production Example 11, except that Polyester D was used instead of Polyester A. The stratification was B / D, and the thickness of each layer was 5/70 (μm).

Production Example 14 (Polyester Film F4) A laminated polyester film of 75 μm was obtained in the same manner as in Production Example 11, except that polyester E was used instead of polyester A. The stratification was B / E, and the thickness of each layer was 15/60 (μm). Production Example 15 (Polyester Film F5) A laminated polyester film of 75 μm was obtained in the same manner as in Production Example 11, except that polyester F was used instead of polyester A. The layer configuration was B / F, and the thickness of each layer was 5/70 (μm).

Production Example 16 (Polyester Film F6) A laminated polyester film of 75 μm was obtained in the same manner as in Production Example 11, except that polyester G was used instead of polyester A. The layer configuration was B / G, and the thickness of each layer was 5/70 (μm). Production Example 17 (Polyester film F7) A laminated polyester film of 75 µm was obtained in the same manner as in Production Example 11, except that polyester H was used instead of polyester A. The layer configuration was B / H, and the thickness of each layer was 5/70 (μm).

Production Example 18 (Polyester Film F8) A laminated polyester film of 75 μm was obtained in the same manner as in Production Example 11, except that Polyester I was used instead of Polyester A. The layer configuration was B / I, and the thickness of each layer was 5/70 (μm). Production Example 19 (Polyester Film F9) In Production Example 11, an attempt was made to produce it in the same manner as in Production Example 11 except that polyester J was used instead of polyester A, but a laminated polyester film could not be obtained.

Example 1 A polyester film F3 (75
μm) to obtain a composite release film in which a release agent having the following composition was provided on the layer B. The properties of this film are shown in Table 1 below.

[0049]

[Table 1] << Composition of release agent >> 硬化 Curable silicone resin (Shin-Etsu Chemical: KS-779H) 100 parts Curing agent (Shin-Etsu Chemical: CAT-PL-8) 1 part MEK / Toluene 2000 parts ────────────────── ──────────────────

Example 2 Polyester film F4 obtained in Production Example 10
Except for using (75 μm), a composite release film having a release layer provided on the layer B in the same manner as in Example 1 was obtained. Table 1 shows the film characteristics. Example 3 Polyester film F5 obtained in Production Example 11
Except for using (75 μm), a composite release film having a release layer provided on the layer B in the same manner as in Example 1 was obtained. Table 1 shows the film characteristics.

Comparative Example 1 The polyester film F1 (7
A composite release film having a release layer provided on the layer B was obtained in the same manner as in Example 1 except that 5 μm) was used. Table 1 shows the film characteristics. Comparative Example 2 The polyester film F2 (7
A composite release film having a release layer provided on the layer B was obtained in the same manner as in Example 1 except that 5 μm) was used. Table 1 shows the film characteristics.

Comparative Example 3 Polyester film F6 obtained in Production Example 16
Except for using (75 μm), a composite release film having a release layer provided on the layer B in the same manner as in Example 1 was obtained. Table 1 shows the film characteristics. Comparative Example 4 Polyester film F7 obtained in Production Example 17
Except for using (75 μm), a composite release film having a release layer provided on the layer B in the same manner as in Example 1 was obtained. Table 1 shows the film characteristics.

Comparative Example 5 Polyester film F8 obtained in Production Example 18
Except for using (75 μm), a composite release film having a release layer provided on the layer B in the same manner as in Example 1 was obtained. Table 1 shows the film characteristics.

[0054]

[Table 2]

[0055]

According to the present invention, there is no generation of burrs at the time of punching a through hole in a green sheet manufacturing process, particularly for a ceramic substrate in the field of manufacturing a ceramic sheet.
A composite release film capable of producing a green sheet having good punching properties can be provided, and its industrial properties are high.

Claims (5)

[Claims] 1. A film made of at least two layers of polyester laminated by co-extrusion, and a release layer is provided on at least one side of a laminated polyester film that simultaneously satisfies the following formulas (1) to (3). Composite release film. 0.51 ≦ [η] ≦ 0.60 (1) 0.1 ≦ d ₅₀ ≦ 1 (2) 5 ≦ WA ≦ 20 (3) , [eta] is the average particle diameter of the particles intrinsic viscosity of the laminated polyester film, d ₅₀ is included in at least one layer of the laminated polyester film ([mu] m), WA represents the amount of the particles (wt%)) 2. The composite release film according to claim 1, wherein the composite release film satisfies the following formulas (4) and (5) simultaneously. 0.03 ≦ Ra ≦ 0.1 (4) 100 ≦ EBβ + EBγ ≦ 200 (5) (In the above formula, EBβ and EBγ are fractures in the β-axis and γ-axis directions of the film, respectively. Elongation (%), Ra represents the center line average roughness (μm) of the release layer surface) 3. The polyester according to claim 1, wherein the amount of particles contained in the polyester on the side provided with the release layer is less than 1% by weight.
The composite release film according to the above. 4. The composite release film according to claim 1, wherein the release layer contains a curable silicone resin as a main component. 5. The composite release film for producing a green sheet according to claim 1, wherein: