JP5409378B2 - Releasable polyester film - Google Patents

Description

  The present invention relates to a releasable polyester film, and more particularly to a releasable polyester film suitable as a carrier film used in a lamination process in a production process of a printed wiring board.

  A printed wiring board having a multi-layered conductor circuit is, for example, a multi-layer laminate of a conductive circuit in which a large number of via holes are formed and a prepreg in which a glass cloth is impregnated with an epoxy resin or the like for insulation, adhesion and conductor protection. Is formed.

  In the manufacturing process of the printed wiring board having such a laminated structure, a method of integrating the laminated body through a series of processes including a heating vacuum pressing process and a high pressure heating pressing process is generally used. At this time, the laminate and the substrate obtained from the laminate are conveyed through a carrier film having releasability. The releasable carrier film is used so as to sandwich a multilayer laminate for constituting a printed wiring board from above and below, and is obtained by integration of the laminate after the heating vacuum pressing step and the high pressure heating pressing step. The printed wiring board is peeled off and wound up.

  The carrier film prevents the laminate and the press plate of the press apparatus from coming into close contact with each other in the pressing process during the production of the printed wiring board. However, since the epoxy resin etc. softened in the heating press process in the laminated body comes into contact with the carrier film through the via hole formed in the conductor circuit, the release property of the carrier film with respect to the laminated body constituting the printed wiring board is When it is inferior, the operability is remarkably deteriorated and the yield is lowered. For this reason, the carrier film used in the lamination process of the printed wiring board is required to have releasability from the material of the printed wiring board and the press plate of the press device, and contributes to the uniform formability of the laminated body. Desired. Therefore, a polyester film having high heat resistance and high dimensional stability is generally used for the carrier film. However, at present, a high degree of releasability is still required.

  From such a viewpoint, JP2002-252458A contains amorphous silica having a large particle size, whereby the center line roughness of the film surface is 0.1 to 1.0 μm and the thermal shrinkage rate is 3% or less. Some polyester films have been proposed. However, if amorphous silica having a large particle size of 4.5 μm or more is blended as in the examples described in JP2002-252458A, the surface roughness is increased, but thus an inorganic particle having a particle size exceeding 4.5 μm. When the particles are contained in the film, the inorganic particles are secondarily aggregated during the production of the film to easily form coarse particles. For this reason, the pressure increase speed of the filter of the melt extruder that melts and extrudes the resin for the production of the film is remarkably increased, and the operability is remarkably deteriorated. If a coarse filter having an absolute filtration diameter of more than 30 μm is used, the concern about the pressurization speed is eliminated, but secondary agglomerates are mixed in the film, which causes a problem in film appearance.

  JP 2005-111798A includes a polyester film in which a release layer formed of a silicone resin or the like is provided on a film having a center line roughness of 0.1 to 1.0 μm in order to improve the release property of the carrier film. Has been proposed. However, in this case, another process for forming the release layer is required after the polyester film manufacturing process. For this reason, not only is the cost high, but the release film that has been peeled off and wound up from the printed wiring board through the press process of the printed wiring board is a mold release made of silicone resin in addition to the polyester film. Since it has a layer, it cannot be used for recycling. In addition, residual solvents are likely to be generated in processing steps such as silicone resin, which causes environmental problems.

  In JP2006-312263A, as a carrier film having a laminated structure and improved peelability, the average diameter of one of the outermost layers is 3 to 10 μm, the amount of the particles is 3 to 30% by weight, A polyester film having a surface roughness of 0.30 to 1.00 μm in terms of arithmetic average roughness has been proposed. However, if a large amount of particles having a particle size of 3 μm or more is blended in a large amount of 3 to 30% by weight, the surface roughness of the film is increased, but the blended particles are secondarily aggregated during film production to form coarse particles. Even if the primary particles are not agglomerated, the pressure increase rate of the filter of the melt extruder is remarkably increased, and the operability is remarkably deteriorated. Similar to the above example, in that case, if a coarse filter having an absolute filtration diameter exceeding 60 μm is used, the concern about the pressure increase speed is eliminated, but secondary aggregates and primary particles are mixed in the film. Problems with film appearance occur.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the polyester film excellent in the release property used suitably as a carrier film in the manufacturing process of a printed wiring board. As a manufacturing process of the printed wiring board here, for example, in order to insulate and protect the conductor circuit, this conductor circuit and an insulating base material made of a prepreg impregnated with glass cloth with epoxy or the like are laminated in multiple layers, After laminating the carrier film on the surface of the laminate thus obtained, a step of applying a heating vacuum press and a high pressure heating press to integrate the laminate in a continuous process can be exemplified.

  As a result of intensive studies to solve such problems, the present inventors have found that a biaxially stretched laminated polyester film having a specific configuration exhibits a high degree of releasability, and have completed the present invention.

  That is, the gist of the present invention consists of three layers of polyester resin layer A / polyester resin layer B / polyester resin layer A, biaxially stretched, and polyester resin layer A constituting the surface layer has an average particle size of 3. 0 to 4.3 μm of inert particles are contained in an amount of 1.5 to 2.8% by mass, and the polyester resin layer B constituting the intermediate layer contains no inert particles or 0.5% by mass or less, and It exists in the releasable polyester film characterized by satisfying following formula (1)-formula (3).

D _A ≧ T _A (1)
2.8 ≧ T _A ≧ 0.5 (2)
100 ≧ T ≧ 20 (3)
However, T _A is the thickness (μm) of the polyester resin layer A, D _A is the average particle size (μm) of the inert particles contained in the polyester resin layer A, and T is the total thickness (μm) of the polyester film. .

  Since the releasable polyester film of the present invention is biaxially stretched, it can be excellent in mechanical properties and dimensional stability. The average particle size of the inert particles contained in the polyester resin layer A constituting the surface layer is in the range of 3.0 to 4.3 μm, and the content thereof is in the range of 1.5 to 2.8% by mass. Thus, the required peelability can be imparted to the resin layer A. Since the polyester resin layer B constituting the intermediate layer does not contain inert particles or contains 0.5% by mass or less as a support having a high ratio to the layer thickness of the entire film, it is included in the entire film layer. The amount of inert particles occupied can be minimized. For this reason, there are no operational troubles such as occurrence of cutting at the time of stretching and abrasion of the cutter blade when trimming the film edge, and it is possible to obtain good mechanical properties such that the film is difficult to tear. When the average particle diameter of the inert particles contained in the polyester resin layer A is equal to or greater than the thickness of the polyester resin layer A, the required peelability can be imparted to the resin layer A. When the total thickness of the polyester film is 20 μm or more and 100 μm or less, the polyester film can be pulled with a strong force with a carrier in various automation systems after imparting a required strength to the polyester film.

  Therefore, according to the releasable polyester film of the present invention, when used as a carrier film for a printed wiring board laminate, it maintains a high degree of releasability with the printed wiring board laminate, and is a heating vacuum press, a high pressure It can be easily released from the laminate after hot pressing. Therefore, the releasable polyester film of the present invention can maintain the productivity of the printed wiring board manufacturing process at a high level, and its industrial value is very high.

It is sectional drawing of the apparatus for measuring the air bleeding time of a film.

  Hereinafter, the present invention will be described in detail.

  The polyester resin constituting the polyester resin layer A and the polyester resin layer B of the releasable polyester film of the present invention is not particularly limited as long as it is a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate. . Polyethylene terephthalate is inexpensive and can be suitably used because of its excellent stretchability. Polyethylene terephthalate is usually a method of transesterification from dimethyl terephthalate and ethylene glycol, or a method of melt polymerization or further solid phase polymerization after obtaining an oligomer by direct esterification from terephthalic acid and ethylene glycol. Is obtained.

  Other components may be copolymerized with the polyester resin. Other copolymer components include dicarboxylic acid components such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecane Examples thereof include dicarboxylic acids such as acid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid and cyclohexanedicarboxylic acid; 4-hydroxybenzoic acid; ε-caprolactone; lactic acid. In addition, as other copolymer components, glycol components include diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, triethylene. Examples include glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, and the like.

  The intrinsic viscosity of the polyester resin constituting the releasable polyester film of the present invention is not particularly limited, but is preferably 0.5 dl / g or more so that the film has sufficient mechanical properties.

  The releasable polyester film of the present invention comprises three layers of polyester resin layer A / polyester resin layer B / polyester resin layer A. The resin layer A constituting the surface layer is a layer in which appropriate inert particles are blended in order to develop releasability. Layer B as an intermediate layer is a layer in which inert particles are blended at a relatively low concentration, and functions as a support layer.

  The polyester resin layer A contains inert particles having an average particle size of 3.0 to 4.3 μm, and the content thereof is 1.5 to 2.8% by mass. When the average particle size is less than 3.0 μm, the air escape time described later becomes long, and good peelability cannot be obtained. In the case of coarse particles having an average particle size exceeding 4.3 μm, in the melt extrusion process during the production of the polyester film, a filter of a melt extruder (when producing a polyester film, the absolute filtration diameter is usually 15 to 40 μm. ) Significantly increases the pressure increase speed, thus increasing the frequency of filter replacement. In the case of coarse particles, secondary aggregates and primary particles of inert particles are visually confirmed in the film, and the product quality tends to be inferior. Furthermore, inactive particles may be lost during the printed wiring board pressing process, and the printed wiring board may be damaged, resulting in a fatal defect. In particular, in the hot press process, the softened insulating base material passes through the via hole formed in the conductor circuit, and when the adhesive is used, the adhesive protrudes. It becomes easy to be missing from. When the content of the inert particles is less than 1.5% by mass, the air escape time described later becomes long, and good peelability cannot be obtained. On the other hand, when the content exceeds 2.8% by mass, the pressure increase rate of the filter of the melt extruder is significantly increased in the melt extrusion process during the production of the polyester film, so that the frequency of filter replacement increases and the film In addition to an increase in the frequency of cutting during stretching, there is a problem that the operability is remarkably deteriorated, such that the wear of the cutter blade when trimming the film edge portion is accelerated. Furthermore, inactive particles are lost in the pressing process of the printed wiring board.

  In the releasable polyester film of the present invention, since it is necessary to blend a large amount of inert particles having a relatively large particle size, the pressure increase rate of the filter becomes a big problem in the melt extrusion process. Especially, since the polyester resin layer B functions as a support layer and occupies most of the total thickness, a large volume of melt extrusion is required. Therefore, the polyester resin layer B is a layer having a small amount of inert particles. Specifically, the polyester resin layer B needs to contain no inert particles or contain 0.5% by mass or less. When the content of the inert particles exceeds 0.5% by mass, the filter pressurization speed increases, which causes a problem in production. Furthermore, inactive particles are lost in the pressing process of the printed wiring board.

  As a method of containing the inert particles in the polyester resin layer B, a method of using a masterbatch containing a predetermined amount of inert particles by polymerization or compound alone, or the masterbatch containing inert particles. And a method of diluting with a non-polyester resin to contain a predetermined amount of inert particles. Moreover, as will be described later, the film end portion cut after stretching the polyester film can be mixed with the virgin raw material and reused. If it does in this way, it is suitable from a viewpoint of industrial waste reduction.

  The average particle diameter of the inert particles contained in the polyester resin layer B is not particularly limited, but 1 to 5 μm is preferable.

  Since the releasable polyester film of the present invention is suitably used as a carrier film in various automation systems, high mechanical properties such as tensile properties are required. For this reason, it is necessary to perform biaxial stretching.

  The releasable polyester film of this invention needs to satisfy | fill the relationship of following formula (1)-Formula (3).

D _A ≧ T _A (1)
2.8 ≧ T _A ≧ 0.5 (2)
100 ≧ T ≧ 20 (3)
However, T _A is the thickness (μm) of the polyester resin layer A, D _A is the average particle size (μm) of the inert particles contained in the polyester resin layer A, and T is the total thickness (μm) of the polyester film. .

In the case of D _A <T _A , the air escape time described later becomes long, and good peelability cannot be obtained.

The thickness _{T A} of the polyester resin layer A is required to be 0.5～2.8Myuemu, more preferably 1.0 to 2.5 [mu] m. If the thickness is less than 0.5 μm, the thickness of the resin layer is too thin, and the inert particles contained in the polyester resin layer A on the surface layer are missing during the pressing process of the printed wiring board, resulting in damage to the printed wiring board. There is a very high risk of generating flaws. As described above, especially in the hot press process, the softened insulating base material passes through the via hole formed in the conductor circuit, or when the adhesive is used, the adhesive may protrude, and accordingly Particles are likely to be missing from the carrier film. When it exceeds 2.8 μm, the amount of the polyester resin layer A blended with inert particles is increased, which is not preferable because the filter pressurization speed of the melt extruder is increased.

  As described above, the total thickness (T) of the polyester film needs to be 20 to 100 μm, and preferably 25 to 50 μm. If it is less than 20 μm, the required strength cannot be obtained. In this case, for example, when the polyester film is peeled off from the printed wiring board through the printed wiring board pressing step, the polyester film is wrinkled due to insufficient rigidity of the polyester film, and the winding tension is lost. There is a high risk of the film breaking. In order to cope with this, when the winding tension is weakened and the winding is performed, wrinkles may propagate to the high-pressure heating press section, and as a result, the product quality is affected and the defect rate is increased. On the contrary, when the total thickness (T) of the polyester film exceeds 100 μm, not only the excessive quality and cost increase, but also the air escape time becomes long.

  Examples of the inert particles blended in the releasable polyester film of the present invention include the following. That is, inorganic particles such as silicon oxide, titanium oxide, calcium carbonate, barium sulfate, aluminum oxide, zeolite, kaolin, clay, talc, mica, acrylic resin, polystyrene resin, phenol resin, melamine resin, benzoguanamine resin, polymethacrylic acid Examples thereof include organic particles such as methyl resin and organic silicone resin. Among these, silicon oxide (silica) is preferable because it is excellent in particle size distribution and film forming property and is inexpensive. Further, two or more kinds of inert particles may be used in combination.

  Assuming that the releasable polyester film of the present invention is used as a carrier film in the production process of a printed wiring board, it is preferable that the air escape time by a measurement method described later is 1.5 seconds or less. That the air escape time is 1.5 seconds or less means that the peelability is good. On the contrary, that the air escape time exceeds 1.5 seconds means that the peelability is poor. In other words, when peeling the polyester film from the printed wiring board through the press process of the printed wiring board, it means that the polyester film is not easily peeled due to resistance, and further, when the polyester film is peeled off from the printed wiring board and wound up It means that wrinkles are generated and the film tends to break under the winding tension. In addition, if the air escape time exceeds 1.5 seconds, even when the winding tension is weakened, wrinkles may propagate to the high-pressure heating press part, and the defect rate tends to increase due to the product quality. Becomes higher.

  The releasable polyester film of the present invention may be provided with irregularities on the surface thereof by subjecting the surface to a known sand mat treatment or embossing. Alternatively, a coating process may be performed on the film surface by a known method using a silicone resin, an epoxy resin, or the like.

  Next, an example of a method for producing the releasable polyester film of the present invention will be described.

  Two types of polyester resin blended with a predetermined amount of inert particles are supplied to separate extruders, melted at a temperature of the melting point of each polyester resin to (melting point + 40 ° C.), and a web made of stainless steel fibers is baked. Three layers of polyester resin layer A / polyester resin layer B / polyester resin layer A are joined together in a multi-manifold die or a feed block through respective compression-molded filters having an absolute filtration diameter of 20 to 30 μm. Extruded into a laminated sheet. Then, the laminated sheet-like body thus extruded is brought into close contact with a cooling drum whose temperature is adjusted to 30 ° C. or lower by a known method such as an electrostatic application casting method or an air knife method so that the temperature becomes a glass transition temperature or lower. Rapid solidification is performed to obtain a laminated unstretched sheet having a desired thickness. Subsequently, the peelable polyester film excellent in mechanical properties and dimensional stability can be obtained by biaxially stretching the obtained laminated unstretched sheet in the longitudinal direction and the transverse direction.

  As a biaxial stretching method, a simultaneous biaxial stretching method in which stretching is performed simultaneously in the machine direction and the transverse direction with a tenter type simultaneous biaxial machine, or in a transverse direction with a tenter type transverse stretching machine after stretching in the longitudinal direction with a roll type stretching machine. A sequential biaxial stretching method for stretching can be used. However, in the case of the sequential biaxial stretching method, even if the film is stretched to the same area ratio as that of the simultaneous biaxial stretching method, the air escape time is remarkably increased, so the simultaneous biaxial stretching method is preferable.

  The draw ratio of the polyester film is preferably 3 times or more, more preferably 4 to 25 times, and still more preferably 6 to 20 times. When the area magnification is less than 3, it is difficult to obtain a film having a low air escape time.

  The stretching temperature is preferably in the range of the glass transition temperature of the polyester resin to (glass transition temperature + 60 ° C.). The stretched film was heat-treated in a tenter at a temperature of 150 ° C. to (polyester melting point−5 ° C.) for several seconds in a tenter with a longitudinal and lateral relaxation rate of 0 to 10%, and then cooled to room temperature. Wind up at a speed of 200 m / min. Thereby, a film having a desired thickness can be obtained.

  The heat treatment after stretching described above is a process necessary for reducing the thermal shrinkage rate of the film. As a heat treatment method, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, or the like can be used. Among them, a method of blowing hot air is preferable because it can be heated uniformly and accurately.

  In the production of the biaxially stretched film, the film end held by the clip in the tenter is cut after the stretching process, but this cut part is not disposed of, and the resin layer A and / or the resin layer B is cut. Therefore, the polyester resin may be put into an extruder that has been melted and reused.

  The releasable polyester film of the present invention can be used as a carrier film having excellent releasability in a build-up method in which a laminate composed of a large number of conductor layers and insulating layers for constituting a printed wiring board is integrated. It is. As a build-up method for laminating and integrating a large number of conductor layers and insulating layers of a printed wiring board, a method of laminating a conductor made of copper foil and a prepreg impregnated with epoxy resin or the like on a glass cloth is laminated , A method of laminating a copper foil with a resin such as epoxy or polyimide by heating and pressurizing, and laminating by heating and pressurizing a copper-prepared prepreg on an insulating resin body coated with a resin liquid such as epoxy or polyimide. And the like. The releasable polyester film of the present invention can be used as a carrier film for any method.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to these examples. In the following Examples and Comparative Examples, the physical property values of the polyester film were measured as follows.

(1) Each layer thickness The film cross section was observed with the electron microscope (SEM), and the thickness of each layer was measured.

(2) Particle size of inorganic particles and organic particles The particle size was measured with a laser diffraction / scattering particle size measuring device SALD-2000 manufactured by Shimadzu Corporation.

(3) Air escape time (film peelability)
Measurements were made using the apparatus shown in FIG. That is, a circular glass plate 2 was attached to the center portion of the table 1. The air groove 8 and the air hole 9 were formed in the table 1 along the outer periphery of the glass plate 2 in a state where they were communicated with each other. The air hole 9 was connected to the vacuum pump 5 by the hose 3 with the cock 4. A sample film 6 having a size covering the surface of the glass plate 2 was fixed to the upper surface of the table 1 with an adhesive tape 7.

  In the measurement, the vacuum pump 5 was driven, the cock 4 was opened, and the system was evacuated. At that time, after the sample film 6 is in close contact with the surface of the glass plate 2 and interference fringes appear on the outer periphery thereof, the time (seconds) until the movement spreads to the whole glass plate 2 and finally stops moving. It was measured and used as the air escape time.

(4) Filter pressurization speed In the melt extruder used, the longitudinally short shaft screw (L / D = 15) with a screw diameter of 14 mm equipped with a gear pump is made of stainless steel fiber on a breaker plate with a filtration diameter of 10 mmφ. A filter (Naslon manufactured by Nippon Seisen Co., Ltd.) having an absolute filtration diameter of 20 μm obtained by sintering and molding the web was fixed. Then, the polyester was melt-extruded at an extrusion rate of 1.0 kg / hr at 280 ° C., and the pressurization rate (MPa / hr) was determined by measuring the extrusion pressure after 1 hour.

  When the pressure increase rate exceeds 3.0 MPa / hr, the filter pressure increase rate is too high, which causes a problem in continuous production.

(5) Printed circuit board model test 1
Copper foil / prepreg / copper foil using a copper foil (400 mm × 400 mm) in which 5 via holes having a diameter of about 0.1 mm / cm ^{2 were} formed and a prepreg (400 mm × 400 mm) impregnated with epoxy resin in a glass cloth A laminate having a structure of / prepreg / copper foil was prepared. The laminate was sandwiched between a pair of polyester films (450 mm × 450 mm) from both sides and fixed, and further sandwiched between aluminum plates (420 mm × 420 mm) and introduced into a hydraulic press. Next, the temperature of the hydraulic device was set to 105 ° C., and a press treatment was performed for 10 minutes at a pressure of 2.5 MPa. Then, after removing the sample from the hydraulic press machine and cooling, the aluminum plate was removed and the polyester film was peeled off.

  At this time, those having a peel strength of less than 0.1 N / cm can be easily peeled, and thus evaluated as ◯. A peel strength of 0.1 to 0.3 N / cm was evaluated as Δ. Those having a peel strength exceeding 0.3 N / cm were evaluated as x because the polyester film was not easily peeled off due to resistance when peeled off from the laminate.

(6) Printed circuit board model test 2
Using the sample different from the printed wiring board model test 1 of (5) above, the same 10-minute press process as that of the printed wiring board model test 1 of (5) was performed. Thereafter, the hydraulic press was released while pulling the end of the polyester film at 10 N / cm. At that time, if the film could be released without breaking, it was evaluated as “good”, and if the film was broken, it was evaluated as “x”.

(7) Missing Particles The surface of the laminate obtained in the printed wiring board model test 1 was observed with a microscope, and the number of inorganic particles adhering to the laminate surface per 1 cm × 1 cm was measured at 10 points. The case where the number of points on which the adhesion of inorganic particles (that is, the lack of inorganic particles from the film) was confirmed was 1 or less was marked with ○, and the case where 2 or more points were confirmed was marked with ×.

(8) Film production situation Continuous production of a biaxially stretched laminated polyester film was conducted for one week, and problems at that time were extracted.

  The manufacturing method of the polyester resin used by the Example and the comparative example is demonstrated.

(Manufacture of polyester resin 1)
100 parts by mass of terephthalic acid and 52 parts by mass of ethylene glycol were charged into an esterification reaction tank, and an esterification reaction was performed at 260 ° C. under a pressure of 0.3 MPaG. Subsequently, the obtained polyester low polymer was supplied to a polycondensation reaction tank and subjected to a polycondensation reaction at 280 ° C. for 120 minutes to obtain a polyester resin 1 having an intrinsic viscosity of 0.62. The filter pressurization speed of the obtained polyester resin 1 was 0 MPa / hr, and no pressure was increased.

(Production of polyester resin 2-1)
100 parts by mass of terephthalic acid and 52 parts by mass of ethylene glycol were charged into an esterification reaction tank, and an esterification reaction was performed at 260 ° C. under a pressure of 0.3 MPaG. Subsequently, the obtained polyester low polymer was supplied to a polycondensation reaction tank. Then, an ethylene glycol dispersion (concentration of 5.5% by mass) of silica (Silicia 550 manufactured by Fuji Silysia) having an average particle diameter of 3.9 μm filtered through a filter having an opening of 30 μm was used, and the silica content in the produced polyester was 2 It added to the polyester low polymer of a polycondensation reaction tank so that it might become 0.0 mass%. Thereafter, a polycondensation reaction was carried out at 280 ° C. for 120 minutes to obtain a polyester resin 2 having an intrinsic viscosity of 0.60. The filter pressurization speed of the obtained polyester resin 2 was 1.5 MPa / hr.

(Production of polyester resin 2-2)
A polyester resin 2-2 having an intrinsic viscosity of 0.60 containing 2.5% by mass of silica having an average particle diameter of 3.9 μm was obtained by the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 2-2 was 1.8 MPa / hr.

(Production of polyester resin 2-3)
A polyester resin 2-3 having an intrinsic viscosity of 0.60 containing 1.7% by mass of silica having an average particle diameter of 3.9 μm was obtained by the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 2-3 was 1.2 MPa / hr.

(Production of polyester resin 2-4)
A polyester resin 2-4 having an intrinsic viscosity of 0.60 containing 3.0% by mass of silica having an average particle diameter of 3.9 μm was obtained by the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 2-4 was 3.2 MPa / hr.

(Production of polyester resin 2-5)
A polyester resin 2-5 having an intrinsic viscosity of 0.60 containing 0.8% by mass of silica having an average particle size of 3.9 μm was obtained by the same formulation as in the production of the polyester resin 2-1. The pressurization rate of the obtained polyester resin 2-5 was 0.6 MPa / hr.

(Production of polyester resin 2-6)
A polyester resin 2-6 having an intrinsic viscosity of 0.60 containing 0.3% by mass of silica having an average particle diameter of 3.9 μm was obtained by the same formulation as that for the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 2-6 was 0.2 MPa / hr.

(Production of polyester resin 2-7)
A polyester resin 2-7 having an intrinsic viscosity of 0.60 containing 0.7% by mass of silica having an average particle diameter of 3.9 μm was obtained by the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 2-7 was 0.5 MPa / hr.

(Production of polyester resin 3)
Silica having an average particle size of 3.1 μm (Silicia 420 manufactured by Fuji Silysia) was used. Other than that, the polyester resin 3 having an intrinsic viscosity of 0.60 containing 2.0% by mass of silica was obtained by the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 3 was 1.1 MPa / hr.

(Production of polyester resin 4)
Silica having an average particle size of 6.2 μm (Silicia 440 manufactured by Fuji Silysia) was used. Other than that, the polyester resin 4 having an intrinsic viscosity of 0.60 containing 2.0% by mass of silica was obtained by the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 4 was 3.8 MPa / hr.

(Production of polyester resin 5)
Silica having an average particle size of 5.0 μm (Silicia 740 manufactured by Fuji Silysia) was used. Otherwise, a polyester resin 5 containing 2.0% by mass of silica and having an intrinsic viscosity of 0.60 was obtained by the same formulation as in the production of the polyester resin 2-1. The obtained polyester resin 5 had a pressure increase rate of 3.4 MPa / hr.

(Production of polyester resin 6)
Silica (Silicia 310P manufactured by Fuji Silysia) having an average particle size of 2.7 μm was used. Otherwise, a polyester resin 6 having an intrinsic viscosity of 0.60 containing 2.0% by mass of silica was obtained according to the same formulation as in the production of the polyester resin 2-1. The pressure increase rate of the obtained polyester resin 6 was 1.0 MPa / hr.

(Manufacture of polyester resin 7)
Instead of silica, zeolite having an average particle size of 4.0 μm (JC-40 manufactured by Mizusawa Chemical Co., Ltd.) was used. Otherwise, a polyester resin 7 containing 2.0% by mass of zeolite and having an intrinsic viscosity of 0.60 was obtained in the same manner as for polyester 2-1. The resulting polyester resin 7 had a pressure increase rate of 1.2 MPa.

(Manufacture of polyester resin 8)
Silica having an average particle size of 4.7 μm (Mizusukacil P-754C manufactured by Mizusawa Chemical Co., Ltd.) was used. Otherwise, a polyester resin 8 having an intrinsic viscosity of 0.60 containing 2.0% by mass of silica having an average particle size of 4.7 μm was obtained by the same formulation as that of the polyester 2-1. The pressure increase rate of the obtained polyester resin 8 was 3.3 MPa.

  Hereinafter, examples and comparative examples will be described in detail.

Example 1
The above-mentioned polyester resin 2-1 having been dried with dehumidified air at 150 ° C. (dew point: −41 ° C.) and having a moisture content of 20 ppm was put into an extruder A (screw diameter 150 mm), and a filter with an absolute filtration diameter of 20 μm was used. And was extruded at 280 ° C. On the other hand, the above-described polyester resin 1 having a moisture content of 20 ppm by drying with dehumidified air at 150 ° C. (dew point: −41 ° C.) for 5 hours is put into an extruder B (screw diameter: 220 mm) and is the same as the extruder A. It melt-extruded at 280 degreeC through the filter with an absolute filtration diameter of 20 micrometers. Two types of melted resin are superposed in a multi-manifold die, polyester resin 2-1 is resin layer A, polyester resin 1 is resin layer B, and A / B / A three-layer structure is formed from a T die to a sheet shape. Were extruded at a total extrusion rate of 900 kg / hr. Then, this was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by an electrostatic application casting method and cooled to obtain an unstretched sheet of A / B / A = 20/210/20 (μm).

  The obtained unstretched sheet was subjected to simultaneous biaxial stretching using a tenter type simultaneous biaxial stretching machine at a stretching temperature of 92 ° C. under the conditions of 3 times in the longitudinal direction and 3.3 times in the transverse direction. Thereafter, a heat treatment was performed at a temperature of 240 ° C. for 5 seconds, and the lateral relaxation rate was set to 5% while maintaining the temperature at 240 ° C., followed by cooling at 80 ° C. Then, in order to remove the grip trace portions gripped by the clips at both ends in the width direction of the film, the film was cut by an MBW50K (blade thickness 0.25 mm) cutter manufactured by Olfa (cutting portion is 15% by mass of the whole film), and then It wound up with the winder and obtained the 3 layer film of thickness 25.0 micrometers. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm).

  The properties of the obtained film are shown in Table 1.

Example 2
Polyester resin 3 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 3
The thickness of the unstretched sheet was A / B / A = 27/190/27 (μm). Otherwise, a three-layer film having a thickness of 24.4 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.7 / 19.0 / 2.7 (μm). The properties of the film are shown in Table 1.

Example 4
Polyester resin 2-2 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 5
Polyester resin 2-3 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 6
The thickness of the unstretched sheet was A / B / A = 20/360/20 (μm). Otherwise, a three-layer film having a thickness of 40.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 36.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 7
Polyester resin 7 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 8
Polyester resin 3 was used for resin layer A, and the thickness of the unstretched sheet was A / B / A = 27/210/27 (μm). Other than that was obtained by the same prescription as Example 1, and obtained the 36.4-micrometer-thick three-layer film. The obtained film was A / B / A = 2.7 / 21.0 / 2.7 (μm). The properties of the film are shown in Table 1.

Example 9
The thickness of the unstretched sheet was A / B / A = 7/230/7 (μm). Otherwise, a three-layer film having a thickness of 24.4 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 0.7 / 23.0 / 0.7 (μm). The properties of the film are shown in Table 1.

Example 10
The thickness of the unstretched sheet was A / B / A = 20/170/20 (μm). Otherwise, a three-layer film having a thickness of 21.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 17.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 11
The thickness of the unstretched sheet was A / B / A = 20/900/20 (μm). Otherwise, a trilayer film having a thickness of 94.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 90.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 12
Polyester resin 2-6 was used for resin layer B. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 13
Recycled pellets (flame content 0.38% by mass, silica particles) having a diameter of about 10 mm and a length of about 20 to 50 mm of flakes obtained by pulverizing both ends in the width direction of the film cut and removed in Example 1 Diameter 3.9 μm) was created. This was put into the extruder B, and it adjusted so that a reproduction | regeneration pellet might be 115 kg / hr among extrusion amount 145 kg / hr. Otherwise, a three-layer film having a thickness of 25.0 μm in which the silica concentration in the resin layer B was 0.3% by mass was obtained in the same manner as in Example 1.

  The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Example 14
An unstretched sheet of A / B / A = 20/210/20 (μm) obtained by the same formulation as in Example 1 was longitudinally stretched 3.0 times with a roll stretching machine at 95 ° C., and then 120 The film was transversely stretched 3.3 times with a tenter-type transverse stretching machine at ℃. After that, heat treatment was performed at a temperature of 240 ° C. for 5 seconds, and the lateral relaxation rate was set to 5% while maintaining the temperature at 240 ° C., and then cooled and wound at 80 ° C. to form a three-layer film having a thickness of 25.0 μm. Obtained. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1.

Comparative Example 1
Polyester resin 4 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1.

  As a result, although a film was obtained, the average particle size of silica was too large, and therefore the pressure increase speed of the filter of Extruder A was too high, which was a production problem. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. In the manufacturing process of the printed wiring board, lack of silica particles was observed.

Comparative Example 2
Polyester resin 5 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1.

  As a result, although a film was obtained, the average particle size of silica was too large, and therefore the pressure increase speed of the filter of Extruder A was too high, which was a production problem. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. In the manufacturing process of the printed wiring board, lack of silica particles was observed.

Comparative Example 3
Polyester resin 8 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1.

  As a result, although a film was obtained, the average particle size of silica was too large, and therefore the pressure increase speed of the filter of Extruder A was too high, which was a production problem. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. In the manufacturing process of the printed wiring board, lack of silica particles was observed.

Comparative Example 4
Polyester resin 6 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. Since the average particle size of the particles contained in the resin layer A was too small, the air escape rate was slow, and therefore, it was not easily peeled off when the film was peeled off from the laminate in the printed wiring board manufacturing process.

Comparative Example 5
The thickness of the unstretched sheet was A / B / A = 3/240/3 (μm). Except for this, a three-layer film having a thickness of 24.6 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 0.3 / 24.0 / 0.3 (micrometer). The properties of the film are shown in Table 1. Since the resin layer A was thin, lack of silica particles was observed in the printed wiring board manufacturing process.

Comparative Example 6
The thickness of the unstretched sheet was A / B / A = 50/150/50 (μm). Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1.

  As a result, a film was obtained, but the filter pressurization speed of the extruder A became too high, which was a problem in production. The obtained film was A / B / A = 5.0 / 15.0 / 5.0 (micrometer). The properties of the film are shown in Table 1. Since the thickness of the resin layer A was larger than the average particle size of the particles contained in the resin layer A, the air escape time was long. For this reason, in the manufacturing process of a printed wiring board, when peeling a film from a laminated board, it did not peel easily.

Comparative Example 7
The thickness of the unstretched sheet was A / B / A = 30/200/30 (μm). Otherwise, a three-layer film having a thickness of 26.0 μm was obtained according to the same formulation as in Example 1.

  As a result, a film was obtained, but the filter pressurization speed of the extruder A became too high, which was a problem in production. The obtained film was A / B / A = 3.0 / 20.0 / 3.0 (μm). The properties of the film are shown in Table 1.

Comparative Example 8
The thickness of the unstretched sheet was A / B / A = 20/120/20 (μm). Otherwise, a three-layer film having a thickness of 16.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 12.0 / 2.0 (μm). The properties of the film are shown in Table 1. Since the total thickness of the film was too thin, the film was broken when the film was pulled after the production of the printed wiring board. For this reason, in the continuous process at the time of manufacture of a printed wiring board, when a releasable film was wound up, there was a concern about film breakage or generation of wrinkles, and the practicality was poor.

Comparative Example 9
Polyester resin 2-4 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. However, since the content of silica in the resin layer A was too large, a film was obtained, but the filter pressurization speed of the extruder A was too high. This was a production problem. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. In the printed wiring board manufacturing process, missing silica particles were observed.

Comparative Example 10
Polyester resin 2-5 was used for resin layer A. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. Since the content of silica in the resin layer A was too small, the air escape time was long, and thus it was difficult to easily peel the film from the laminate in the printed wiring board manufacturing process.

Comparative Example 11
Polyester resin 6 was used for resin layer A, and the thickness of the unstretched sheet was A / B / A = 28/210/28 (μm). Otherwise, a 26.6 μm thick three-layer film was obtained according to the same formulation as in Example 1. The obtained film was A / B / A = 2.8 / 21.0 / 2.8 (μm). The properties of the film are shown in Table 1. Since the thickness of the resin layer A was larger than the average particle size of the particles contained in the resin layer A, the air escape time was long. For this reason, in the manufacturing process of a printed wiring board, when peeling a film from a laminated board, it did not peel easily.

Comparative Example 12
The thickness of the unstretched sheet was A / B / A = 20/1000/20 (μm). Otherwise, a three-layer film having a thickness of 104.0 μm was obtained by the same formulation as in Example 1. The obtained film was A / B / A = 2.0 / 100.0 / 2.0 (μm). The properties of the film are shown in Table 1. Since the resin layer B was thick, the air escape time was long. For this reason, in the manufacturing process of a printed wiring board, when peeling a film from a laminated board, it did not peel easily.

Comparative Example 13
Polyester resin 2-8 was used for resin layer B. Otherwise, a three-layer film having a thickness of 25.0 μm was obtained in the same manner as in Example 1. However, since the content of silica in the resin layer B was too large, a film was obtained, but the filter pressurization speed of the extruder B was too high. This was a production problem. The obtained film was A / B / A = 2.0 / 21.0 / 2.0 (μm). The properties of the film are shown in Table 1. Since there was too much content of the silica in the resin layer B, the missing of the silica particle was recognized in the manufacturing process of a printed wiring board.

  As is clear from Table 1, the films of Examples 1 to 14 were excellent releasable polyester films.

  On the other hand, each comparative example has the following problems.

  In Comparative Examples 1 to 3, since the average particle diameter of silica in the resin layer A exceeded the range specified in the present invention, the absence of silica particles was observed in the production process of the printed wiring board.

  In Comparative Example 4, since the average particle diameter of silica in the resin layer A was less than the range specified in the present invention, the air escape time was long. Therefore, in the manufacturing process of the printed wiring board, the release property of the film is inferior. For this reason, it is difficult to remove the film from the printed wiring board, and the film is broken.

  In Comparative Example 5, since the thickness of the resin layer A was thin and out of the range of the formula (2), the absence of silica particles was observed in the manufacturing process of the printed wiring board.

  In Comparative Examples 6 and 7, the thickness of the resin layer A was large and deviated from the range of the formula (2). For this reason, the filter pressurization speed of the extruder A of the resin layer A containing the inert particles is increased, which is a production problem.

  In Comparative Example 8, since the total thickness of the film was thin and was out of the range of the formula (3), the film was broken in the manufacturing process of the printed wiring board.

  In Comparative Example 9, since the silica content in the resin layer A exceeded the range specified in the present invention, the filter pressurization speed of the extruder A for the resin layer A in which the inert particles were blended was increased. It was a problem. In addition, the absence of silica particles was observed in the manufacturing process of the printed wiring board.

  In Comparative Example 10, since the silica content in the resin layer A was less than the range specified in the present invention, the air escape time was long. Therefore, in the manufacturing process of the printed wiring board, the release property of the film is inferior. For this reason, it is difficult to peel off the film from the printed wiring board, and the film is broken.

  In Comparative Examples 6 and 11, the thickness of the resin layer A was larger than the average particle diameter of the particles contained in the resin layer A, and was out of the range of (1). For this reason, the air escape time was long, and when the film was peeled from the laminated board in the manufacturing process of the printed wiring board, it was not easily peeled off.

  In Comparative Example 12, since the total thickness of the film was thick and was out of the range of the formula (3), the air escape time was long. Therefore, the mold release property of the film is inferior in the manufacturing process of the printed wiring board, and therefore it is difficult to peel the film from the printed wiring board.

  In Comparative Example 13, since the silica content in the resin layer B exceeded the range specified in the present invention, the filter pressurization speed of the extruder B of the resin layer B in which the inert particles were blended was increased. there were. In addition, the absence of silica particles was observed in the manufacturing process of the printed wiring board.

Claims (4)

Polyester resin layer A / polyester resin layer B / polyester resin layer A are composed of three layers, biaxially stretched, and the polyester resin layer A constituting the surface layer has an average particle size of 3.0 to 4.3 μm. 1.5 to 2.8% by mass of the particles, the polyester resin layer B constituting the intermediate layer does not contain inert particles or 0.5% by mass or less, and the following formulas (1) to ( 3. A releasable polyester film characterized by satisfying 3).
D _A ≧ T _A (1)
2.8 ≧ T _A ≧ 0.5 (2)
100 ≧ T ≧ 20 (3)
However, T _A is the thickness (μm) of the polyester resin layer A, D _A is the average particle size (μm) of the inert particles contained in the polyester resin layer A, and T is the total thickness (μm) of the polyester film. .   The releasable polyester film according to claim 1, which has been subjected to simultaneous biaxial stretching.   The releasable polyester film according to claim 1 or 2, wherein the air escape time is 1.5 seconds or less.   A carrier film for a production process of a printed wiring board, comprising the releasable polyester film according to any one of claims 1 to 3.

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