JP2006312263A - Laminated mat-like polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated mat-like polyester film which keeps excellent mold releasability with respect to a press plate and a CL material even if the temperature of a press mold is raised and shows excellent processability not obtained in a conventional polyester film, without damaging its film forming continuity in a CL laminating process (heating press) at the time of production of a printed wiring board. <P>SOLUTION: The laminated mat-like polyester film is a laminated film composed of at least two layers. At least the layer, which constitutes one uppermost surface of the laminated film, contains 3-30 wt.% of inorganic or organic particles with a mean particle size of 3-10 μm and its surface roughness Ra (arithmetic average roughness) is 0.30-1.00 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a matte polyester film.

  In recent years, with the rapid progress of electronic devices, as the degree of integration of ICs (integrated circuits) increases, printed wiring boards have been frequently used for the purpose of meeting the demands for higher accuracy, higher density, and higher reliability. It is well known that Examples of the type of the printed wiring board include a single-sided printed wiring board, a double-sided printed wiring board, a multilayer printed wiring board, and a flexible printed wiring board.

  In the production process of a printed wiring board, a predetermined circuit is provided on the surface of an insulating substrate (for example, polyimide resin), and then a heat-resistant resin film with an adhesive (generally a polyimide film) for the purpose of insulation and circuit protection. A cover lay (hereinafter referred to as CL) is covered, and press molding is performed through a release film. Release film with excellent releasability from printed wiring board material (CL) and press board, conformability to shape, uniform formability, finished appearance, and plating on circuits in subsequent processes in this manufacturing process Is required.

On the other hand, since a polyester film has a high melting point of about 260 ° C., it exhibits excellent heat resistance even in press molding of a printed wiring board. In view of the productivity of printed wiring boards in recent years, polyester films that have been imparted with moderate surface roughness due to their inert heat-resistant particles are partly used as release films. There is a tendency to raise the press molding temperature, and there is a problem that the release property between the release film and the printed wiring board material (CL) becomes insufficient.
JP 2002-252458 A

  This invention is made | formed in view of the said situation, Comprising: The solution subject is excellent with respect to a press board and CL even if it raises press molding temperature in the CL sticking process (heating press) at the time of printed wiring board manufacture. An object of the present invention is to provide a mat-like polyester film that exhibits releasability and exhibits excellent processability that cannot be obtained with conventional polyester films.

  As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is a laminated film composed of two or more layers, and the layer constituting at least one outermost surface contains 3 to 30% by weight of inorganic particles or organic particles having an average particle diameter of 3 to 10 μm. The laminated mat-like polyester film has a surface roughness Ra (arithmetic mean roughness) of 0.30 to 1.00 μm.

Hereinafter, the present invention will be described in more detail.
As the polyester constituting the laminated mat-like polyester film of the present invention, typically, for example, polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6. -Polyethylene-2,6-naphthalate which is naphthalate, poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate, and the like. In addition to these, polyethylene isophthalate, polybutylene terephthalate, and the like can also be mentioned.

  Examples of copolymer components other than the above-described dominant components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, and polytetramethylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, and 5-sodium dicarboxylic acid. Ester-forming derivatives such as diasulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and oxymonocarboxylic acid can be used. Further, as the polyester, in addition to a homopolymer or a copolymer, a small proportion of a blend with another resin can also be used.

  In order for the laminated mat-like polyester film of the present invention to exhibit stable releasability, it is essential to provide a specific range of Ra (arithmetic mean roughness), that is, high surface roughness.

  Below, the method to give a high degree of surface asperity to the laminated mat-like polyester film of the present invention will be described.

  For imparting irregularities to the film surface, a method in which inactive inorganic particles or organic particles are blended and extruded into polyester as a base material and extruded, and the resulting sheet is stretched at least in a uniaxial direction is preferably used.

  The inert particles include mainly known inorganic particles such as silicon oxide (silica), titanium oxide, calcium carbonate, barium sulfate, aluminum oxide, kaolin, clay, carbon black, acrylic resin, polystyrene, and organic silicone resin. And organic particles such as an acrylic-styrene copolymer, and any one or more of them may be blended. Among these, silicon oxide (silica) is preferable from the viewpoints of particle size distribution and film formability. In addition to the silicon oxide particles, it is also one of preferred embodiments that other particles such as titanium oxide are blended.

  The average particle diameter of the inert particles contained in at least one outermost layer of the laminated mat-like polyester film of the present invention is 3 to 10 μm, preferably 3.5 to 9 μm, more preferably 4 to 8 μm. . When the average particle size is less than 3 μm, sufficient unevenness is not formed on the film surface, and the desired Ra, that is, the peelability tends to be not obtained. On the other hand, when the average particle size exceeds 10 μm, the unevenness of the film surface becomes too high, and there is a tendency that problems such as dropout of particles and deterioration of film forming continuity occur.

  When the inert particles are blended in the present invention, the content thereof is 3 to 30% by weight, preferably 4 to 20% by weight, as a ratio during blending of the polyester (film) constituting at least one outermost layer. More preferably, it is 5 to 15% by weight. When the content of the inert particles is less than 3% by weight, sufficient unevenness is not formed on the film surface, and the desired Ra, that is, the peelability tends to be not obtained. On the other hand, when the content exceeds 30% by weight, the unevenness of the film surface becomes too large, and there is a tendency that problems such as dropout of particles and deterioration of film forming continuity occur.

  The intrinsic viscosity (dl / g) of the laminated mat-like polyester film of the present invention is preferably 0.60 or more, more preferably 0.65 or more. When the intrinsic viscosity is less than 0.60, a film having sufficient mechanical strength may not be obtained.

  The arithmetic mean roughness (Ra) of at least one surface of the laminated mat-like polyester film of the present invention needs to be 0.30 to 1.00 μm, preferably 0.40 to 0.90 μm, more preferably It is in the range of 0.50 to 0.80 μm. If Ra is less than 0.30 μm, the desired peelability tends not to be obtained. On the other hand, when Ra exceeds 1.00 μm, the unevenness of the film surface tends to be too large, and problems such as particles falling off and adhering to the hot plate during hot pressing may occur.

  The ten-point average roughness (Rz) of at least one surface of the laminated mat-like polyester film of the present invention is preferably 1.0 to 5.0 μm, more preferably 1.3 to 4.0 μm, still more preferably. Is in the range of 1.6 to 3.0 μm. When Rz is less than 1.0 μm, sufficient unevenness is not formed on the film surface, and the desired peelability tends not to be obtained. On the other hand, when Rz exceeds 5.0 μm, the unevenness of the film surface tends to be too large.

  The total thickness of the laminated mat-like polyester film of the present invention is not particularly limited, but the base film thickness for printed wiring board production (release film in the CL press process) is from the viewpoint of moderate elasticity and avoiding wrinkles Usually, it is 20-100 micrometers, Preferably it is 25-75 micrometers, More preferably, it is the range of 30-50 micrometers.

  The laminated mat-like polyester film of the present invention needs to be composed of two or more layers. That is, since at least one outermost surface needs to maintain a high degree of unevenness (matte tone), it is necessary to contain a considerable amount (3 to 30% by weight) of inorganic particles or organic particles having a specific particle size (3 to 10 μm). A film having such a composition often cannot maintain a strength capable of withstanding biaxial stretching in a single layer configuration. In other words, film forming continuity cannot be maintained. Therefore, at least one particle reducing layer (a layer for contributing to maintaining the film strength) different from the surface layer is essential. As long as the gist of the present invention is not exceeded, the particle reduction layer may be composed of two or more layers.

  The thickness of the particle multi-layer constituting at least one outermost surface is usually 3 μm or more, preferably 5 μm or more, more preferably 7 μm or more. When the thickness of the outermost surface layer is less than 3 μm, sufficient unevenness is not formed on the film surface, and the intended peelability tends not to be obtained.

  The upper limit of the thickness of the particle multi-layer is limited by the total thickness of the film. However, in consideration of the problem of strength reduction and cost increase due to the reduction of the ratio of the particle reduction layer, the total thickness is preferable. 1/3 or less, more preferably 1/4 or less.

  The laminated mat-like polyester film of the present invention may be provided with a surface coating layer in order to improve antistatic properties, slipperiness and peelability. The coated surface is not limited to one side or both sides of the polyester film, and in the case of both sides, either the same coating layer or different coating layers may be used. However, attention should be paid to the influence of the components of the coating layer being transferred to the surface of the printed wiring board during pressing.

  In the method for producing a polyester film of the present invention, a polymer blended in a predetermined manner is generally melted and extruded, and then stretched at least in a uniaxial direction according to a roll stretching method, a tenter method, or the like. In order to appropriately satisfy mechanical strength and thermal dimensional stability, it is preferable to use a biaxial stretching method and a heat treatment method in combination.

  Here, an example in the case of using biaxial stretching will be described in detail. First, the raw materials are blended and supplied to an extruder, and after melt-kneading, the molten polymer is usually guided to a T-die and extruded into a slit shape. In the case of constituting a laminated film, different raw materials are supplied to different extruders, and the polymer is laminated in a slit shape in a T-die and extruded. Next, the molten sheet extruded from the die is rapidly cooled and solidified on the rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the planar uniformity and cooling effect of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and in the present invention, an electrostatic application adhesion method is preferably employed. Next, the obtained sheet is stretched in a biaxial direction to form a film. The surface irregularities of the polyester film of the present invention are generated by such stretching.

  First, the unstretched sheet is stretched under the conditions of a stretching temperature of usually 70 to 150 ° C., preferably 75 to 130 ° C., usually 2.0 to 6.0 times, preferably 2.5 to 5.0 times. Stretch in one direction (longitudinal direction). A roll and tenter type stretching machine can be used for such stretching. Next, at a stretching temperature of usually 75 to 150 ° C., preferably 80 to 140 ° C., orthogonal to the first stage under the conditions of a stretching ratio of usually 2.0 to 6.0 times, preferably 2.5 to 5.0 times. The film is stretched in the direction (transverse direction) to obtain a biaxially oriented film. For such stretching, a tenter type stretching machine can be used.

  A method of performing the above-mentioned unidirectional stretching in two or more stages can also be adopted, but in this case as well, it is preferable that the final stretching ratio falls within the above-described range. The unstretched sheet can be simultaneously biaxially stretched so that the area magnification is 6 to 30 times. Next, heat treatment in the tenter is usually performed at 180 to 240 ° C., preferably 200 to 235 ° C., for 1 second to 5 minutes. In this heat treatment step, relaxation of 0.1 to 20% in the transverse direction and / or the longitudinal direction is performed in the zone of the highest temperature of the heat treatment and / or the cooling zone immediately before the heat treatment outlet, in order to impart thermal dimensional stability. Is preferable.

  The laminated mat-like polyester film of the present invention can be used as a release film at the time of CL (cover lay) press molding in the production process of a printed wiring board, taking advantage of its characteristics. Further, it can be widely applied to other general-purpose applications (for example, for building materials and for hot stamping).

  ADVANTAGE OF THE INVENTION According to this invention, while maintaining film forming continuity, the mat-like polyester film which has a high degree of surface asperity can be provided. The film exhibits good releasability in a printed wiring board manufacturing process (coverlay press molding), has an effect of improving production efficiency, and has an extremely high industrial value.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples, unless the summary is exceeded. In addition, the various physical property in this invention, its measuring method, and a definition are as follows. In Examples and Comparative Examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

(1) Average particle size of additive (μm)
The particle size was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation. The average particle diameter was determined by using a value of 50% of integration (volume basis) in the equivalent spherical distribution of particles obtained by measurement.

(2) Intrinsic viscosity of polyester (dl / g)
A mixed solvent of phenol / tetrachloroethane: 50/50 (weight ratio) was added to 1 g of polyester at a ratio of 100 ml, and the mixture was measured at 30 ° C.

(3) Arithmetic average roughness Ra, Ten-point average roughness Rz (μm)
The measurement was performed using a surf coder SE3500 manufactured by Kosaka Laboratory. The measurement was performed 12 times on one side (cast surface) of the sample under the following conditions, and an average value of 10 points excluding the maximum and minimum points was taken.
・ Tip tip diameter: 5 μm ・ Measurement force: 30 mgf ・ Measurement length: 2.5 mm ・ Cutoff value: 0.08 mm

(4) Process suitability test by hot press (Matte) Film / printed substrate (surface cover lay) / (Matte) film laminated in order with press hot plate (170 ° C., 30 kg / cm ² , 60 minutes) Then, after pressure-cooling until it became 50 degreeC, the following items were evaluated.
"Coverlay (polyimide film) releasability"
◯: Release from the coverlay was easy.
Δ: Release from the coverlay was possible, but heavier than ○.
X: It was difficult to release from the coverlay, and a problem was found in workability.
"Press board (SUS) releasability"
○: Adhesion with the press plate was not recognized, and it was good.
X: Adhesion to the press plate occurred and there was a problem in workability.

Example 1
Containing 9.0% of amorphous silica particles having an average particle size of 4.5 μm, polyethylene terephthalate chip (raw material A) having an intrinsic viscosity of 0.71 and 600 ppm of amorphous silica particles having an average particle size of 2.5 μm, Polyethylene terephthalate chips (raw material B) having an intrinsic viscosity of 0.71 (raw material B) are directly put into separate twin-screw extruders with vents and melted and kneaded at 270 ° C. After being laminated so as to be / A, it was extruded into a slit shape and cooled on a cooling drum at 30 ° C. to obtain an unstretched sheet.

Next, the unstretched sheet was stretched 3.5 times at 83 ° C. in the longitudinal direction, and further stretched 3.3 times at 105 ° C. in the transverse direction. After the temperature was raised stepwise, heat treatment was performed at 230 ° C. for 5 seconds. Next, under an atmosphere of 180 ° C., a relaxation treatment of 3% (to narrow the tenter rail width) was performed in the width direction.
Finally, a biaxially oriented film having a film thickness of 45 μm (thickness ratio: 9/27/9 μm) was obtained.

(Example 2)
In Example 1, the raw material A was changed to polyethylene terephthalate chips (raw material A ′) having an intrinsic viscosity of 0.71 containing 6.0% of amorphous silica particles having an average particle diameter of 4.5 μm. Finally, a biaxially oriented film having a film thickness of 45 μm (thickness ratio is the same as in Example 1) was obtained.

(Example 3)
In Example 1, the raw material A was changed to polyethylene terephthalate chips (raw material A ″) having an intrinsic viscosity of 0.71 containing 3.0% of amorphous silica particles having an average particle diameter of 4.5 μm. Finally, a biaxially oriented film having a film thickness of 45 μm (thickness ratio is the same as in Example 1) was obtained.

(Comparative Example 1)
In Example 1, the same procedure as in Example 1 was repeated except that the raw material A was changed to a polyethylene terephthalate chip having the intrinsic viscosity of 0.71 (same as the raw material B) containing 600 ppm of amorphous silica particles having an average particle diameter of 2.5 μm. A biaxially oriented film having a film thickness of 45 μm (thickness ratio is the same as in Example 1) was obtained.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the raw material A was changed to a polyethylene terephthalate chip (raw material A ′ ″) having an intrinsic viscosity of 0.71 containing 2.0% of amorphous silica particles having an average particle diameter of 4.5 μm. Finally, a biaxially oriented film having a film thickness of 45 μm (thickness ratio is the same as in Example 1) was obtained.

(Comparative Example 3)
In Example 1, the raw material B was replaced with a polyethylene terephthalate chip (same as the raw material A) having an intrinsic viscosity of 0.71 containing 9.0% of amorphous silica particles having an average particle diameter of 4.5 μm. Finally, an attempt was made to collect a biaxially oriented film having a film thickness of 45 μm (thickness ratio is the same as in Example 1). However, the film continued to break, and the film could not be collected under predetermined conditions.
The characteristics of the obtained film are summarized in Table 1 below.

The film of the present invention can be suitably used, for example, as a release film for producing a printed wiring board.

Claims (1)

It is a laminated film composed of two or more layers, and at least one of the layers constituting the outermost surface contains 3 to 30% by weight of inorganic particles or organic particles having an average particle diameter of 3 to 10 μm, and its surface roughness Ra (arithmetic) A laminated mat-like polyester film having an average roughness) of 0.30 to 1.00 μm.