JP2010168422A - Biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film exhibiting excellent mold releasability by compounding an organic resin. <P>SOLUTION: The biaxially oriented polyester film is comprised of 99.9-95.0 mass% of a thermoplastic polyester resin and 0.1-5.0 mass% of polymethylpentene and/or a maleimide copolymer, and has a void ratio of at most 2.8% and a center line average roughness (SRa) of the film surface of 0.10-0.50 μm. Preferably, the biaxially oriented polyester film has a tensile elongation of at least 80%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biaxially stretched polyester film having a roughened film surface comprising a polymethylpentene and / or maleimide copolymer, and is preferably used in a laminate process of a printed wiring board such as an electronic device. It is related with the biaxially stretched polyester film which is excellent in.

  Biaxially stretched films such as polyethylene terephthalate are used in a wide range of fields because of their excellent physical properties such as transparency, mechanical strength, and dimensional stability, and chemical properties such as chemical resistance. . It is also used as a carrier film for a printed wiring board lamination process having a multilayer conductor circuit by roughening the surface of the film and imparting releasability.

  A printed wiring board having a multilayer conductor circuit is formed by, for example, laminating a conductor circuit formed with a number of via holes and a prepreg impregnated with an epoxy resin into a glass cloth in order to insulate, bond and protect the conductor. The In the production process of a printed wiring board, a method of integrating a heating vacuum press and a high-pressure heating press through a series of steps is common, but at this time, the printed wiring board is usually conveyed via a release film.

  In the manufacturing process of the printed wiring board, the printed wiring board laminate is transported so as to be sandwiched from above and below using the release film, and after the heating vacuum press and the high pressure heating press process, the release film is It is peeled off from the printed wiring board laminate and wound up. In the manufacturing process, the releasable film is used as a carrier film during process transfer for preventing adhesion to the press plate.

  In particular, during the hot pressing process, softened epoxy resin or the like may pass through the via hole formed in the conductor circuit and come into contact with the release film. At this time, the printed wiring board laminate and the release film are poorly peeled. In such a case, the operability is remarkably deteriorated and the yield is lowered. Therefore, the mold release film used in the printed circuit board lamination step is required to have a mold release property with respect to the printed circuit board material and the press plate and a uniform moldability.

  In order to satisfy these requirements, a roughened polyester film has been proposed as a releasable film. As a roughening method for polyester film, inorganic or organic inert particles are blended into polyester and biaxially stretched to roughen the film surface, or sandblasting or embossing using a coating agent. There is a method of roughening by surface etching such as chemical treatment.

  As a surface roughening method using organic particles, a polyester film in which fine particles such as acrylic resin, melamine resin, polystyrene, organic silicone resin, and acrylic-styrene copolymer are blended is disclosed (Patent Document 1). However, even when these organic particles are blended, sufficient protrusions cannot be obtained, and it has been difficult to achieve the centerline average roughness (SRa) of the film surface necessary as a carrier film for a printed wiring board manufacturing process. .

  Moreover, the microbubble containing polyester film which mix | blended polymethylpentene is proposed (patent document 2). However, this film has a large amount of fine bubbles formed inside, resulting in insufficient film strength and elongation, and the film is severely cut during the manufacturing process of the printed wiring board, and the operability is remarkably inferior. It was.

JP 2007-039515 A Japanese Patent Publication No.7-17779

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the polyester film which has the outstanding mold release property by the mixing | blending of organic resin.

  As a result of intensive studies to solve such problems, the present inventors have roughened the surface of the film by blending a specific resin with the thermoplastic polyester resin, and the center of the film surface suitable for mold release. It has been found that the line average roughness (SRa) can be controlled, and the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) It is composed of 99.9 to 95.0% by mass of a thermoplastic polyester resin and 0.1 to 5.0% by mass of polymethylpentene and / or maleimide copolymer, and the void ratio is 2.8% or less. A biaxially stretched polyester film having a film surface centerline average roughness (SRa) of 0.10 to 0.50 μm.
(2) The biaxially stretched polyester film according to (1), wherein the tensile elongation is 80% or more.
(3) The biaxially stretched polyester film according to (1) or (2), wherein the air escape time is 1.5 seconds or less.
(4) The biaxially stretched polyester film according to any one of (1) to (3) obtained by simultaneous biaxial stretching.
(5) A carrier film for a printed wiring board manufacturing process comprising the biaxially stretched polyester film according to any one of (1) to (4).

  The biaxially stretched polyester film of the present invention can obtain centerline average roughness of the film surface excellent in releasability by blending a predetermined amount of polymethylpentene and / or maleimide copolymer. it can.

  The biaxially stretched polyester film of the present invention is superior to those obtained by sequential stretching without using an increase in the void ratio that causes a decrease in tensile elongation when using simultaneous biaxial stretching. Since the centerline average roughness of a surface can be achieved, it is preferable.

  Thus, the cost reduction and productivity of the printed wiring board manufacturing process can be maintained at a high level, and its industrial value is very high.

In this invention, it is sectional drawing of the apparatus for measuring an air escape time.

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

  In the present invention, the thermoplastic polyester resin constituting the biaxially stretched polyester film is not particularly limited, and polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene-2, 6- Examples thereof include naphthalate, poly-1,4-cyclohexylenedimethylene terephthalate, poly-p-ethyleneoxybenzoate, polylactic acid, and the like. Among these, polyethylene terephthalate is preferably used because it is inexpensive and has excellent stretchability. Polyethylene terephthalate is usually obtained by melt polymerization after obtaining an oligomer by transesterification from dimethyl terephthalate and ethylene glycol or direct esterification from terephthalic acid and ethylene glycol. Or obtained by further solid-phase polymerization.

  The thermoplastic polyester resin can be further copolymerized with other components. 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 and lactic acid. . Further, as glycol components, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanediol Examples include methanol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, and the like.

  The intrinsic viscosity of the thermoplastic polyester resin is not particularly limited, but in order to have sufficient mechanical properties, it is preferable to use a thermoplastic polyester resin of 0.5 dl / g or more as a raw material. In particular, a melt flow rate (hereinafter abbreviated as MFR) measured at a temperature of 280 ° C. and a load of 10 kg in accordance with the JIS K7210 B method is preferably 50 to 500 g / 10 min, more preferably 200 to 200- 400 g / 10 min.

  The biaxially stretched polyester film of the present invention comprises 0.1 to 5.0% by mass of polymethylpentene and / or maleimide copolymer with respect to 99.9 to 95.0% by mass of the thermoplastic polyester resin. Become. Only one of polymethylpentene (hereinafter abbreviated as PMP) and maleimide copolymer may be used, or both may be used in combination. When using together, the sum total of both resin should just be the range of 0.1-5.0 mass%. Both polymethylpentene and maleimide copolymers are incompatible resins with thermoplastic polyester resins, and when melt-mixed within the above range, they tend to disperse into islands in thermoplastic polyester resins. . When such a morphological resin is stretched to form a film, fine protrusions are formed on the surface.

  The blending ratio of the thermoplastic polyester resin and the PMP and / or maleimide copolymer in the biaxially stretched polyester film is in the range of 99.5 / 0.5 to 95.0 / 5.0 (% by mass /% by mass). Is more preferably 99.0 / 1.0 to 95.0 / 5.0 (mass% / mass%).

  PMP used in the biaxially stretched polyester film of the present invention is a polymer having units derived from 4-methylpentene-1 at 80 mol% or more, preferably 90 mol% or more, and as other components Is exemplified by units derived from ethylene units, propylene units, butene-1 units, 3-methylbutene-1, and the like.

  The MFR of PMP used as a raw material is preferably in the range of 200 to 1100 g / 10 minutes, and more preferably in the range of 300 to 1000 g / 10 minutes, with a temperature of 280 ° C. and a load of 10 kg in accordance with JIS K7210 B method. is there. When the MFR is less than 1 g / 10 minutes, the cutting frequency of the film in the step of stretching the unstretched sheet increases, which is not preferable. Moreover, when MFR exceeds 1100 g / 10min, it exists in the tendency for the centerline average roughness (SRa) of the polyester film surface obtained to become low.

  Examples of commercially available PMP that can be used in the present invention include TPX MX004, RT18, RT31 manufactured by Mitsui Chemicals.

  The maleimide copolymer used in the present invention includes a maleimide monomer, an aromatic vinyl monomer, an unsaturated dicarboxylic acid anhydride monomer, and other copolymerizable monomers as required. It is comprised from.

  Examples of maleimide monomers include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-hexylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-tolylmaleimide, N- ( Halogenated phenyl) maleimide, N- (alkylphenyl) maleimide, N- (nitrophenyl) maleimide, N- (hydroxylphenyl) maleimide, N-naphthylmaleimide, α-chloro-N-phenylmaleimide, α-methyl-N- Examples thereof include phenylmaleimide.

  Examples of the aromatic vinyl monomer include styrene, α-methyl styrene, vinyl toluene, t-butyl styrene, halogenated styrene and the like.

  Examples of the unsaturated dicarboxylic acid anhydride monomer include maleic anhydride, methylmaleic anhydride, 1,2-dimethylmaleic anhydride, ethylmaleic anhydride, phenylmaleic anhydride and the like.

  Examples of other copolymerizable monomers include acrylic monomers, and specific examples of acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth). Examples include acrylate, hexyl (meth) acrylate, octadecyl (meth) acrylate, decyl (meth) acrylate, cyclohexyl (meth) acrylate, hydroxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, and glycidyl (meth) acrylate. Here, methyl (meth) acrylate means methyl acrylate or methyl methacrylate.

  The MFR of the maleimide copolymer used as a raw material is preferably in the range of 1 to 100 g / 10 minutes, more preferably 5 to 50 g / 10 in terms of a value at a temperature of 280 ° C. and a load of 10 kg in accordance with JIS K7210 B method. The range of minutes. When the MFR is less than 1 g / 10 minutes, the cutting frequency of the film in the step of stretching the unstretched sheet increases, which is not preferable. Moreover, when MFR exceeds 100 g / 10min, it exists in the tendency for the centerline average roughness (SRa) of the polyester film surface obtained to become low.

  Examples of commercially available maleimide copolymers that can be used in the present invention include Denka IP MS-NA, MS-CP, and MS-NC manufactured by Denki Kagaku Kogyo.

  The thickness of the biaxially stretched polyester film of the present invention is preferably 10 μm or more in order to give rigidity to the film and suppress cutting during winding, and when used as a carrier film in a printed wiring board manufacturing process The thickness is preferably 15 to 50 μm. More preferably, it is 20-40 micrometers.

  The tensile elongation of the biaxially stretched polyester film of the present invention is preferably 80% or more from the viewpoint that film breakage during the manufacturing process of the printed wiring board can be suppressed.

  The void ratio of the biaxially stretched polyester film of the present invention needs to be 2.8% or less. When the void ratio exceeds 2.8%, the strength and elongation of the film are insufficient, and film breakage due to insufficient elongation is likely to occur during the manufacturing process of the printed wiring board.

  In the biaxially stretched polyester film of the present invention, the film surface centerline average roughness (SRa) needs to be 0.10 to 0.50 μm. If the SRa is less than 0.10 μm, the desired releasability cannot be obtained. On the other hand, when SRa exceeds 0.50 μm, the void ratio tends to increase following SRa, and film breakage is likely to occur during the manufacturing process of the printed wiring board.

  Hereinafter, the manufacturing method of the biaxially stretched polyester film of this invention is demonstrated.

  The biaxially stretched polyester film of the present invention is a substantially amorphous polyester obtained by melt-kneading a thermoplastic polyester resin blended with PMP and / or a maleimide copolymer with an extruder or the like and then extruding it from a die into a slit shape. A sheet is obtained, and this polyester sheet is obtained by biaxial stretching in the longitudinal and transverse directions and then heat treatment.

  The method of blending the PMP and / or maleimide copolymer with the polyester is not particularly limited. For example, the polyester chip and a desired amount of PMP and / or maleimide copolymer chip are uniformly mixed in advance to an extruder. What is necessary is just to put into the raw material supply hopper. Further, the method of quantitatively supplying the polyester chip and the PMP and / or maleimide copolymer chip to the raw material inlet of the extruder is preferably employed because it is particularly simple and has little blending unevenness.

  The blending ratio of the thermoplastic polyester resin to the polymethylpentene and / or maleimide copolymer in the biaxially stretched polyester film is 99.9 / 0.1 to 95.0 / 5.0 (mass% / mass%). It is. When the blending amount of the polymethylpentene and / or maleimide copolymer exceeds 5.0% by mass, the void ratio exceeds 2.8%, so that the tensile strength becomes less than 80%, and the printed wiring board is manufactured. The film will be cut during the process. When the blending amount is less than 0.1% by mass, the center line average roughness (SRa) of the film surface is 0.1 μm or less, and a sufficient air escape rate cannot be obtained. The releasability as a carrier film is impaired.

  The conditions for melt-kneading the polyester resin blended with PMP and / or maleimide copolymer are appropriately set depending on the resin to be used, but are preferably set to a temperature of 250 to 320 ° C.

  The molten resin extruded in a slit shape from the die is cooled to a substantially amorphous polyester sheet. The cooling temperature at this time is preferably 70 ° C. or lower.

  The temperature at which the polyester sheet blended with PMP and / or maleimide copolymer is biaxially stretched is in the range of the glass transition temperature to the crystallization temperature of the thermoplastic polyester resin. The range of temperature +30) ° C. is preferred. At a temperature lower than the glass transition temperature of the thermoplastic polyester resin, the thermoplastic polyester resin becomes difficult to melt, so that the stretchability of the film is deteriorated. (Glass transition temperature +30) When biaxially stretched at a temperature higher than 0 ° C., PMP and / or maleimide copolymer is likely to be deformed together with the thermoplastic polyester resin, and in the thermoplastic polyester resin which is a sea component, PMP and The maleimide copolymer is less likely to be an island component, and as a result, projections are not easily formed.

  As the draw ratio, the area ratio is preferably 3 times or more. More preferably, the area magnification is 6 to 20 times, and still more preferably, the area is 6.5 to 13 times. When the area magnification is less than 3 times, the center line average roughness (SRa) of the film surface of 0.10 μm or more may not be obtained, and when the area magnification exceeds 20 times, film breakage tends to occur frequently. is there.

  In the sequential biaxial stretching, the longitudinal stretching ratio is preferably 2.0 times or more, and the transverse stretching is preferably 1.5 or more. In the simultaneous biaxial stretching, the area magnification is usually 3 times or more, preferably the area magnification. The range is 6 to 20 times, more preferably 6.5 to 13 times. When the area magnification is less than 3, it is difficult to obtain a film having a short air escape time.

  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, and a tenter-type transverse stretching machine after stretching in the longitudinal direction with a roll-type stretching machine. In the case of sequential biaxial stretching, the center line average roughness of the film surface can be used as compared with the simultaneous biaxially stretched film stretched to the same area ratio. Since (SRa) becomes small, the simultaneous biaxial stretching method is suitable.

  Examples of the conditions for heat-treating the stretched film include heat treatment for several seconds at 150 ° C. to (polyester melting point−5 ° C.) or less with a relaxation rate of 0 to 10% in the longitudinal and lateral directions in the tenter. It is done. The film is then cooled to room temperature.

  In the biaxially stretched polyester film of the present invention, in order to set the void ratio to 2.8% or less, the mixing ratio of the thermoplastic polyester resin and the PMP and / or maleimide copolymer constituting the film is within a predetermined range. In addition, it is important to control the stretching stress when stretching the polyester film in which these are mixed. Since the stretching stress is affected by factors such as (1) stretching method, (2) stretching temperature, and (3) stretching ratio, the stretching stress can be controlled by appropriately combining these within the range of the manufacturing conditions described above. When the stretching stress is increased, the void ratio increases, and when the stretching stress is decreased, the void ratio tends to decrease. Hereinafter, the influence of each factor (1) to (3) on the stretching stress and the void ratio will be described.

  Regarding the selection of the stretching method, the void formation of the polyester film tends to be promoted as the stretching stress increases. However, the sequential biaxial stretching performs the transverse stretching after the longitudinal stretching, and therefore the oriented crystallization of the film during the longitudinal stretching. Advances, and a large stretching stress is required during transverse stretching. For this reason, in general, the sequential biaxial stretching method has a higher stretching stress than the simultaneous biaxial stretching method in which the longitudinal and lateral stretching are performed simultaneously. In the polyester film of the present invention, when the sequential biaxial stretching method is adopted, the void ratio of the polyester film may exceed the range specified in the present invention, whereas in the simultaneous biaxial stretching method, the void ratio is increased. Easy to control within specified range. Therefore, in the present invention, as the stretching method, the simultaneous biaxial stretching method is more advantageous than the sequential biaxial stretching method.

  If the stretching temperature is low, the stretching stress tends to be high, and if the stretching temperature is low, the stretching stress tends to be low. Therefore, the higher the stretching temperature, the higher the void ratio.

  If the draw ratio is high, the draw stress tends to be high, and if the draw ratio is low, the draw stress tends to be high. Accordingly, the higher the draw ratio, the higher the void ratio.

  The center line average roughness (SRa) of the film surface is adjusted by controlling the appearance of protrusions generated on the surface of the biaxially stretched film. Specifically, a PMP and / or maleimide copolymer is dispersed in a sea-island structure in a thermoplastic polyester resin to form an unstretched sheet, and then the unstretched sheet is biaxially stretched to form a film surface. Then, protrusions derived from the PMP and / or maleimide copolymer that are islands are formed. Such control of the surface state can be achieved by adjusting the stretching conditions in addition to using the PFR and / or maleimide copolymer content in the above range and using the MFR of the resin used as a raw material in the above range. It is controlled by doing.

  As a stretching method, when simultaneous biaxial stretching and sequential biaxial stretching are compared, the simultaneous biaxial stretching method tends to increase SRa. Moreover, as a draw ratio, SRa tends to be larger at a low draw ratio. By combining these stretching conditions within the numerical range described above, it can be adjusted within the range of SRa of the present invention.

  In the biaxially stretched polyester film of the present invention, various additives may be blended as long as the effects of the present invention are not impaired. Examples of the additive include an antioxidant, an antistatic agent, an ultraviolet absorber, a pigment, a dye, a lubricant, a matting agent, a fluorescent brightening agent, a surfactant, and a silicone-based surfactant.

  Since the biaxially stretched polyester film of the present invention is excellent in releasability, it is suitable as a carrier film in the production process of a printed wiring board. As an index of releasability, it is preferable that the air escape time measured by the method described later is 1.5 seconds or less. When the air escape time exceeds 1.5 seconds, the polyester film is not easily peeled off due to resistance when the polyester film is peeled from the printed wiring board through the press process of the printed wiring board. Furthermore, when the polyester film is peeled off from the printed wiring board and wound, wrinkles are generated due to insufficient rigidity of the polyester film, and the film may be cut under the winding tension, which is not preferable. In addition, when the winding tension is weakened, wrinkles may be propagated to the high-pressure heating press section, which affects the product quality and increases the defect rate. The air escape time is measured using the measuring apparatus shown in FIG. That is, a circular glass plate 2 having a diameter of 60 mm is attached to the central portion of the table 1 (350 mm × 500 mm), and air grooves 8 and air holes 9 are formed along the outer periphery of the attached glass plate 2. Then, the air hole 9 and the vacuum pump 5 are connected by a hose 3 with a cock 4, and a sample film 6 sized to cover the glass plate 2 is fixed to the top of the table 1 with a commercially available vinyl tape 7. Then, the vacuum pump 5 is driven. When the degree of vacuum of the pump becomes 10 Pa or less by the vacuum pump, the cock 4 is opened, the interference fringes appear on the outer periphery of the glass plate 2, spread over the entire glass plate 2, and finally the time until the movement stops ( Second) and measure it as the air removal time.

  The biaxially stretched polyester film of the present invention is suitably used as a carrier film excellent in releasability in a build-up method in which a laminate composed of a large number of conductor layers and insulating layers of a printed wiring board is laminated. The build-up method of laminating a large number of conductor layers and insulating layers on a printed wiring board is a method of laminating a conductor made of copper foil and a prepreg impregnated with epoxy resin on glass, and a resin such as epoxy and polyimide And a method of laminating the attached copper foil by heating and pressing, and a method of laminating by heating and pressing the copper-plated prepreg on the insulating resin body coated with a resin liquid such as epoxy and polyimide. Can be applied to any method of carrier film.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

1. Measuring method

(1) Thickness of each layer The cross section of the film was observed with a scanning electron microscope (SEM), and the thickness of each layer was measured from the photographed photograph.

(2) Apparent density Shimadzu Corporation dry automatic densimeter 1330-03 type | mold was used, and the apparent density of raw material resin or a film was measured. The measured mass of the sample was 0.6 to 0.8 g.

(3) Void ratio (%)
Based on the apparent density value, the following formula was used.
Void ratio (%) = ([theoretical film density] − [apparent density of film]) / [theoretical film density]) × 100
However, the theoretical film density = ([addition resin blending ratio (mass%)] × [addition resin apparent density]) + ([polyester resin blending ratio (mass%)] × [polyester resin apparent density]).

(4) Centerline average roughness (SRa)
Using a surface roughness measuring instrument SE-3AK manufactured by Kosaka Laboratory Ltd., the measurement was performed according to the method of JISB-0601-1976. The stylus diameter was 2 μmR, the stylus pressure was 10 mg, and the height magnification was 50000 times.

(5) Air escape time Using the measuring device shown in FIG. 1, a circular glass plate 2 is attached to the center of the table 1, and air grooves 8 and air holes 9 are formed along the outer periphery of the attached glass plate 2. Let Then, the air hole 9 and the vacuum pump 5 are connected by a hose 3 with a cock 4, and a sample film 6 sized to cover the glass plate 2 is fixed to the top of the table 1 with a commercially available vinyl tape 7. Then, the vacuum pump 5 is driven, the cock 4 is opened, and the time (second) until the movement stops after the interference fringes appear on the outer periphery of the glass plate 2 is spread over the whole glass plate 2 is measured. , And let this be the air escape time.

(6) Tensile elongation Using a DSS-500 type autograph manufactured by Shimadzu Corporation, the tensile elongation was measured according to ASTM D882 and measured by average values in the vertical and horizontal directions.

(7) Printed circuit board model test 1
Copper foil / prepreg / copper foil / prepreg made of copper foil (400 mm × 400 mm) formed with 5 via holes having a diameter of about 0.1 mm / cm ² and a prepreg (400 mm × 400 mm) impregnated with epoxy resin in a glass cloth. / A laminated board having a copper foil structure is prepared, and a polyester film is sandwiched and fixed between the upper and lower parts, and further sandwiched between aluminum sheets and introduced into a hydraulic press. Next, a press treatment is performed for 10 minutes at a pressure of 2.5 MPa with a hydraulic press at 105 ° C., and the pressure is removed from the hydraulic press. Further, after cooling, after removing the aluminum plate, the polyester film is peeled off. When the peel strength is less than 0.1 N / cm, ○, when 0.1 or more and less than 0.3 N / cm, Δ, 0.3 N Those having a density of not less than / cm were evaluated as x. When the peel strength is 0.3 N / cm or more, the polyester film is not easily peeled off due to resistance when peeled off from the laminate.

(8) Printed circuit board model test 2
After the press treatment for 10 minutes in the printed wiring board model test 1, the hydraulic press is released while pulling the polyester film at 10 N / cm. At this time, if the film was not cut, it was rated as ◯, and if the film was cut, it was marked as x.

2. Raw material In addition, the following apparent density value is based on the said measuring method (2), and is a value measured about the resin pellet except polyethylene terephthalate.

(1) Polyethylene terephthalate (hereinafter abbreviated as PET):
Intrinsic viscosity 0.62, MFR 300 g / 10 min (value measured at a temperature of 280 ° C. and a load of 10 kg in accordance with B method of JIS K7210, the same applies hereinafter), an apparent density of 1.431 g / cm ³ . The apparent density is a value in the stretched film obtained in Comparative Example 1.

(2) PMP:
Mitsui Chemicals polymethylpentene TPX MX004, MFR 1050 g / 10 min, apparent density 0.845 g / cm ³

(3) Maleimide copolymer:
Denka IP MS-NA manufactured by Denki Kagaku Kogyo Co., Ltd., MFR 17 g / 10 min, apparent density 1.172 g / cm ³

(4) Polypropylene:
Made by Mitsui Chemicals, no blend F0-50F, apparent density 0.902 g / cm ³

(5) Low density polyethylene:
Novatec LF443 manufactured by Nippon Polyethylene Co., Ltd., apparent density 0.919 g / cm ³

(6) High density polyethylene:
Novatec HF560 manufactured by Nippon Polyethylene Co., Ltd., apparent density 0.929 g / cm ³

(7) Polystyrene:
Manufactured by Mitsui Chemicals Co., Ltd., Taupo Rex 570-57U, an apparent density of 1.056g / cm ³

Example 1
2.0 parts by mass of PMP and 98.0 parts by mass of PET were supplied to an extruder (screw diameter: 220 mm) and melt extruded at 280 ° C. The mixed molten resin was extruded from a T-die in a sheet form, brought into close contact with a cooling drum having a surface temperature of 25 ° C., and cooled to obtain a 250 μm unstretched sheet. The obtained unstretched sheet was sequentially stretched at a stretching temperature of 92 ° C., a stretching ratio of 3.6 times in the longitudinal direction and a transverse direction of 3.4 times, and then subjected to a heat treatment at a temperature of 240 ° C. for 5 seconds. The transverse relaxation rate was adjusted to 5% while maintaining the temperature at 240 ° C., and the film was cooled and wound at 80 ° C. to obtain a biaxially stretched film having a thickness of 25 μm.

Example 2
A biaxially stretched film having a thickness of 25 μm was obtained by the same formulation as in Example 1 except that the PET / PMP ratio supplied to the extruder was 97.0 parts by mass / 3.0 parts by mass.

Example 3
PMP 3.0 mass part and PET 97.0 mass part were supplied to the extruder (screw diameter 220mm), and it melt-extruded at 280 degreeC. The molten resin was extruded in a sheet form from a T-die, and adhered and cooled on a cooling drum having a surface temperature of 25 ° C. by an electrostatic application casting method to obtain a 250 μm unstretched sheet. The obtained unstretched sheet was simultaneously biaxially stretched with a tenter type simultaneous biaxial stretching machine at a stretching temperature of 92 ° C., an area magnification of 3 times in the longitudinal direction and 3.3 times in the transverse direction, and then a temperature of 240 A heat treatment was performed at 5 ° C. for 5 seconds, and the transverse relaxation rate was adjusted to 5% while maintaining the temperature at 240 ° C., followed by cooling at 80 ° C. and winding to obtain a biaxially stretched film having a thickness of 25 μm.

Example 4
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the PET / PMP ratio supplied to the extruder was 95.0 parts by mass / 5.0 parts by mass.

Example 5
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that 3.0 parts by mass of maleimide copolymer and 97.0 parts by mass of PET were supplied to the extruder.

Example 6
A biaxially stretched film having a thickness of 25 μm was obtained by the same formulation as in Example 3 except that the ratio of the PET / maleimide copolymer supplied to the extruder was 97.0 parts by mass / 3.0 parts by mass.

Example 7
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the ratio of the PET / maleimide copolymer supplied to the extruder was 95.0 parts by mass / 5.0 parts by mass.

Example 8
An unstretched sheet having a thickness of 180 μm was obtained in the same manner as in Example 3 with the ratio of the PET / maleimide copolymer supplied to the extruder being 95.0 parts by mass / 5.0 parts by mass. Using this sheet, it was stretched according to the same formulation as in Example 3 to obtain a biaxially stretched film having a thickness of 18 μm.

Example 9
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that 2.0 parts by mass of PMP, 3.0 parts by mass of maleimide copolymer, and 95.0 parts by mass of PET were supplied to the extruder.

  The results of Examples 1-9 are shown in Table 1.

  As is clear from Table 1, in Examples 1 to 9, biaxially stretched polyester films having excellent releasability were obtained. These could be used as carrier films for printed wiring board manufacturing processes.

Comparative Example 1
By supplying only PET to the extruder, a biaxially stretched film having a thickness of 25 μm was obtained according to the same formulation as in Example 3. Since neither PMP nor maleimide copolymer was blended, the center line average roughness (SRa) of the film surface was 0.05 μm, and the air escape time was long. Therefore, in the manufacturing process of the printed wiring board, the film releasability is inferior, it is difficult to remove the film from the printed wiring board, and the film is also cut.

Comparative Example 2
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the PET / PMP ratio supplied to the extruder was 92.0 parts by mass / 8.0 parts by mass. The amount of PMP specified in the present invention was exceeded. The elongation was 70%. The film was cut during the manufacturing process of the printed wiring board.

Comparative Example 3
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the resin supplied to the extruder was 92.0 parts by mass of PET and the maleimide copolymer ratio was 8.0 masses. The blending amount of the maleimide copolymer specified in the present invention was exceeded, and the void ratio was 3.1%, significantly exceeding the specified value. Further, the tensile elongation was less than 80%. The film was cut during the manufacturing process of the printed wiring board.

Comparative Example 4
A biaxially stretched film having a thickness of 25 μm was obtained by the same formulation as in Example 3 except that the resin supplied to the extruder was 95.0 parts by mass of PET and 5.0 parts by mass of polypropylene. The center line average roughness (SRa) of the film surface is 0.05 μm, and the air escape time is long. In the manufacturing process of the printed wiring board, the release property of the film was inferior. It was difficult to remove the film from the printed wiring board, and the film was also cut.

Comparative Example 5
A biaxially stretched film having a thickness of 25 μm was obtained by the same formulation as in Example 3 except that the resin supplied to the extruder was 95.0 parts by mass of PET and 5.0 parts by mass of low-density polyethylene. The center line average roughness (SRa) of the film surface is 0.04 μm, and the air escape time is long. In the manufacturing process of the printed wiring board, the release property of the film was inferior. It was difficult to remove the film from the printed wiring board, and the film was also cut.

Comparative Example 6
A biaxially stretched film having a thickness of 25 μm was obtained by the same formulation as in Example 3 except that the resin supplied to the extruder was 95.0 parts by mass of PET and 5.0 parts by mass of high-density polyethylene. However, the center line average roughness (SRa) of the film surface is 0.08 μm, and the air escape time is long. In the manufacturing process of the printed wiring board, the release property of the film was inferior. It was difficult to remove the film from the printed wiring board, and the film was also cut.

Comparative Example 7
A biaxially stretched film having a thickness of 25 μm was obtained by the same formulation as in Example 3 except that the resin supplied to the extruder was 95.0 parts by mass of PET and 5.0 parts by mass of polystyrene. The center line average roughness (SRa) of the film surface is 0.08 μm, and the air escape time is long. In the manufacturing process of the printed wiring board, the release property of the film was inferior, it was difficult to remove the film from the printed wiring board, and the film was also cut.

Comparative Example 8
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the PET / PMP ratio supplied to the extruder was 95.0 / 5.0 (parts by mass). The void ratio was 3.1%, significantly exceeding the specified value. Further, the tensile elongation was less than 80%. Film breakage occurred during the manufacturing process of the printed wiring board.

Comparative Example 9
A biaxially stretched film having a thickness of 25 μm was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was 95.0 parts by mass of PET and 5.0 parts by mass of maleimide copolymer. The properties of the film are shown in Table 1. The void ratio was 3.5%, significantly exceeding the specified value. Further, the tensile elongation was less than 80%. Film breakage occurred during the manufacturing process of the printed wiring board.

  The results of Comparative Examples 1-9 are shown in Table 1. In each of the comparative examples, various problems as described above occurred and could not be used as a carrier film for a printed wiring board manufacturing process.

1 unit (350mm x 500mm)
2 Glass flat plate (60mmΦ)
3 Suction hose 4 Cock 5 Vacuum pump 6 Sample film 7 Vinyl tape 8 Air groove 9 Air hole

Claims (5)

It is composed of 99.9-95.0% by weight of thermoplastic polyester resin and 0.1-5.0% by weight of polymethylpentene and / or maleimide copolymer, and has a void ratio of 2.8% or less, film surface The biaxially stretched polyester film whose centerline average roughness (SRa) is 0.10 to 0.50 μm. The biaxially stretched polyester film according to claim 1, wherein the tensile elongation is 80% or more. The biaxially stretched polyester film according to claim 1 or 2, wherein the air escape time is 1.5 seconds or less. The biaxially stretched polyester film according to any one of claims 1 to 3, obtained by simultaneous biaxial stretching. The carrier film for printed wiring board manufacturing processes which consists of a biaxially stretched polyester film in any one of Claims 1-4.