JP5322893B2 - Support polyester film for interlayer insulation material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film which is adaptable to low roughness and defect prevention of the surface of an interlayer insulating layer and which is suitable as a support for the interlayer insulating material. <P>SOLUTION: The polyester film for supporting the interlayer insulating material is a co-extruded biaxially oriented laminate polyester film comprising at least 3 layers. One of the outermost layer has 0.4-5 &mu;m thickness, the outermost layer contains the aggregate of aluminum oxide having 5-40 nm average particle diameter of a primary particle in an amount of 0.1-0.8 weight, the average particle diameter of the aggregate being 50-400 nm. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a support film of an interlayer insulating material, and more particularly to a support film of an interlayer insulating material used for a circuit board. For example, a circuit board configuration such as a printed wiring board, a multilayer wiring board, a semiconductor device, and a liquid crystal display device The present invention provides a support polyester film for an interlayer insulating material suitable as a support film for an interlayer insulating material used for forming an interlayer insulating layer as a member. Here, the support polyester film for an interlayer insulating material is a support film used to apply and dry an interlayer insulating material solution in a film shape in advance, and the obtained film-shaped interlayer insulating material is vacuum-pressed or vacuum-rolled. Using a laminator, it is peeled off after being bonded onto the circuit board.

  A printed wiring board is a board on which a copper circuit is formed in order to mount and connect electronic components such as ICs, such as consumer printed wiring boards used in household appliances such as televisions, computers, measuring instruments, etc. Examples include industrial printed wiring boards used for industrial purposes. Although there is no clear distinction, the printed wiring board base material is mainly used for consumer use, such as those made from paper-based phenolic resin laminates. The used glass cloth base laminate is used as a base for an industrial printed wiring board.

  As the number of terminals such as ICs installed on a printed wiring board increases, multilayering is achieved as a means for accommodating necessary wiring in a limited area, and multilayer printed wiring boards are also mass-produced.

  Print out by repeating the process of forming a wiring pattern on a rigid board, forming an insulating layer on it, forming a wiring pattern on it, and then forming an insulating layer. The build-up method for forming wiring boards is used as a method suitable for products that require miniaturization, such as mobile phones, and for applications that require high-speed operation, such as computers. As the performance increases, the build-up layer is further multi-layered, and the miniaturization and density of wiring are further advanced.

  The insulating layer used in the multilayer printed wiring board is made of glass cloth impregnated with epoxy or polyimide resin, or ceramic material. The signal propagation speed of the wiring layer or the printed wiring board Therefore, it is necessary to select a material that satisfies such electrical characteristics. Specifically, a material having a dielectric constant as low as possible is selected. Various proposals have been made. In addition, since the insulating layer is formed on the film support with a uniform thickness, it is preferable to meet the demands for miniaturization and high performance, and a material that can be applied is used. Yes.

  The insulation layer is formed by applying a thermosetting resin as an insulation layer to a film-like support as an interlayer insulation material to cope with downsizing and high performance, and curing the support film with the film. A method has been proposed in which the layers are rolled. With regard to the insulating layer in the film state, it is a film having an insulating layer for buildup that is designed to be suitable for laser processing and to improve the plating adhesion of the resin surface after the roughening treatment, by optimal selection of resin and filler, etc. Various proposals have been made regarding the insulating layer, such as to meet recent demands.

  However, the film, which is a support for forming a film-like insulating layer, has a specific effect in spite of having a great influence on the surface properties of the insulating layer and the productivity when forming the insulating layer. No proposal has been made.

  In particular, in order to achieve finer and higher density wiring, lowering the surface roughness of the interlayer insulating layer and preventing defects are important characteristics, and the characteristics of the film used for the support are greatly related. Nevertheless, no proposal has been made regarding the support film.

Miniaturization of wiring requires a very narrow wiring width and space of several hundred microns to several microns, but if the roughness of the surface of the interlayer insulating layer is large, the risk of the following problems increases.
1. Since it is difficult for the plating solution to enter the recess, the supply of reactive species is reduced, and electroless cylinder plating does not occur, so-called non-plating occurs.
2. In the electrolytic copper plating process, voids are formed in the recesses, and the treatment liquid remains, causing corrosion.
3. In the etching for forming the circuit, the etching proceeds from the concave portion under the circuit, the pattern is thinned, and the copper plating is not etched and the remaining circuit is short-circuited.
4). Long-term flash etching is required to remove plating residue (smear) that has entered the recess, and if the flash etching is performed for a long time, the fine wiring is damaged or disconnected.

  Since the film surface serving as the support is rolled up in the form of a roll, protrusions due to the added particles are formed, and these protrusions are transferred to the surface of the interlayer insulating layer to form dents. Therefore, to reduce the roughness of the surface of the interlayer insulating layer, it is necessary to reduce the roughness of the support film. However, if the roughness of the support film is extremely advanced, scratches may occur on the support film surface during the processing steps from the support film molding process to the application of the interlayer insulation material. The scratch on the surface of the support film on the layer side becomes a defect of the interlayer insulating layer and the wiring circuit.

JP 2005-154727 A JP 2005-39247 A JP 2008-251971 A

  The present invention has been made in view of the circumstances as described above, and the problem to be solved by the present invention is a polyester film suitable as a support for an interlayer insulating material that can cope with low roughness of the interlayer insulating layer surface and prevention of defects. Is to provide.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that a polyester film having a specific configuration can easily solve the above problems, and have completed the present invention.

That is, the gist of the present invention is a coextruded biaxially oriented laminated polyester film comprising at least three layers and having a film thickness of 15 to 50 μm, and the thickness of one outermost layer is 0.4 to 5 μm. The outer layer contains 0.1 to 0.8 % by weight of aluminum oxide aggregates having an average primary particle size of 5 to 40 nm, and the average particle size of the aggregates is 50 to 400 nm. It exists in the support polyester film for interlayer insulation materials.

  According to the present invention, a film suitable as an interlayer insulating material support can be provided, and the industrial value of the present invention is high.

Hereinafter, the present invention will be described in more detail.
The film of the present invention is a biaxially oriented polyester film, and is a laminated film of three layers or four layers or more obtained by a so-called coextrusion method using three or more melt extruders.

  The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyester includes polyethylene terephthalate (PET) and the like. On the other hand, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned. In any case, the polyester referred to in the present invention refers to a polyester that is polyethylene terephthalate or the like that is usually 60 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, which is an ethylene terephthalate unit.

  One of the characteristics of the present invention is the particle size and form of aluminum oxide particles to be blended in one outermost layer of the polyester film. That is, in the present invention, aggregate particles obtained by appropriately agglomerating fine primary particles are used. In order to obtain a high-strength film, it is necessary to orient strongly at the time of film formation, but in this case, dropout of particles from the film surface and generation of wear powder are often significant. However, in the case of agglomerated particles, the stretching stress at the time of film formation is moderately dispersed, or the particles are unlikely to fall off, and the comparatively rough protrusions are given to the film surface. Give different and favorable friction and wear properties.

  The average particle diameter of the aggregate is in the range of 50 to 400 nm, preferably in the range of 70 to 300 nm. When this value is less than 50 nm, when the film comes into contact with the roll of a processing machine, the wear resistance of the film becomes inferior. On the other hand, when this value exceeds 400 nm, the cutting blade tends to be chipped when the film is cut, and the slit property becomes poor.

  In this invention, the average particle diameter of the primary particle which comprises this aggregate is 5-40 nm. When this value is less than 5 nm, the agglomerates often have extremely strong bonds, and the bonds are hardly broken even by stretching stress, making it difficult to obtain the effects specific to the present invention. On the other hand, when this value exceeds 40 nm, the aggregate particles are separated and dropped off, which causes a scratch.

  The aluminum oxide used in the present invention can be obtained, for example, by heating and baking boehmite, vialite, or gibbsite to about 880 to 1150 ° C. in air or in vacuum. By selecting the conditions at the time of production, for example, the type, crystallinity, particle size, purity of the starting material, or the atmosphere, temperature and speed during heating, a material having a primary particle size of 5 to 40 nm required in the present invention can be obtained. Although they can, they often form aggregates in excess of 1 μm. Aggregates having an appropriate particle size used in the present invention can be easily obtained, for example, by pulverizing such coarse aggregates.

  For the pulverization treatment, for example, a rod mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a pan mill, a roller mill, an impact mill, a stirring mill, a fluid energy mill, or the like can be used. In addition, if necessary, ultrasonic dispersion treatment may be performed, but if the degree is strong, care is required because the particles are dispersed to the primary particles or a state close thereto. In the present invention, treatments such as classification and filtration may be used in combination.

  In the present invention, it is preferable that the outermost layer surface containing the specific particles has a specific surface roughness. Therefore, for example, in addition to the specific particles, it is preferable to contain particles having an average particle diameter of 0.1 to 0.6 μm, and more preferably 0.2 to 0.5 μm. If the average particle size is less than 0.1 μm, the surface roughness of the film tends to be low, and the slipperiness of the film tends to be poor. As a result, scratches may occur on the film surface. Moreover, after forming a support film, a product may not be obtained in a roll state. When the average particle diameter exceeds 0.6 μm, the dent on the surface of the interlayer insulating layer becomes large, which may adversely affect wiring miniaturization and circuit density.

  The content of the combined particles in the polyester film layer is preferably 100 to 2000 ppm, more preferably 200 to 1500 ppm, and particularly preferably 500 to 1000 ppm. If the particle content is less than 100 ppm, the slipperiness of the film may be deteriorated. Moreover, when content exceeds 2000 ppm, the surface roughness of a film becomes large too much and planarity may be impaired.

  Examples of particles used in combination include silicon oxide, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, lithium phosphate, magnesium phosphate, lithium fluoride, aluminum oxide, titanium oxide, kaolin, talc, carbon black, nitriding Examples thereof include silicon, boron nitride, and crosslinked polymer fine powders as described in JP-B-59-5216, and are not limited to these as long as the gist of the present invention is not impaired.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  In the present invention, in the intermediate layer of the polyester film, the amount of particles having an average particle size of 0.4 μm or more is preferably 100 ppm or less, more preferably 50 ppm or less, particularly preferably 0 ppm. If it exceeds 100 ppm, undulation may occur on the surface of the polyester film, which may adversely affect wiring miniaturization and circuit density.

  The center line average roughness SRaA on the surface of the film layer containing the specific particles is preferably in the range of 0.5 to 15 nm, more preferably 0.5 to 10 nm. When the center line average roughness SRaA is less than 0.5 nm, the slipperiness of the film and the air leakage between the films are poor, and the film surface tends to be damaged, and the product is obtained in a roll state after film formation. May not be possible. Further, when the center line average roughness SRaA exceeds 15 nm, there may be a negative effect on the miniaturization of the wiring and the high density of the circuit.

  The polyester film itself of the present invention is peeled off after the interlayer insulating layer is bonded to the core substrate as an adhesive sheet, and the role is finished, but the interlayer insulation bonded to the core substrate after the polyester film is peeled off Affects the surface of the layer.

  The surface of the polyester film on which the thermosetting resin is applied and the interlayer insulating layer is formed has a center line average roughness Ra of 30 nm or less, more preferably 20 nm or less, and a ten-point average roughness Rz of 200 nm or less. 100 nm or less is preferable. When the central average roughness Ra exceeds 30 nm or the ten-point average roughness Rz exceeds 200 nm, the surface roughness of the interlayer insulating layer increases, which may adversely affect circuit density. .

  The thickness of the polyester film of the present invention is not particularly limited as long as it can be formed as a film, but is usually 15 to 50 μm, preferably 20 to 40 μm. If the film thickness is less than 15 μm, wrinkles may occur when an insulating material is applied. When the film thickness exceeds 50 μm, the amount of polyester used per unit area of the interlayer insulating layer is increased, so that the cost is high.

  The curable resin used for the interlayer insulating layer used in the present invention can be used without particular limitation as long as it can form a layer on a support and has sufficient insulating properties. System, polyimide resin system, polyimide amide resin system, polycyanate resin system, polyester resin system, thermosetting polyphenylene ether resin system, and the like. Further, two or more of these may be used in combination, or a multilayer structure may be used.

  A method for forming an interlayer insulating layer on a support is a known method in which the resin composition varnish in which the above-described thermosetting resin or the like is dissolved in a solvent is applied, and then the solvent is dried by heating to simultaneously cure the resin. Can be created by the method.

  In the present invention, a cured resin layer serving as an interlayer insulating layer is provided as a laminated film on a support made of a polyester film, and the laminated film is formed into a roll shape. When making it into a roll shape, it does not matter whether it can be stored as it is, in a state where a protective film for protecting the surface of the cured resin is bonded, or in a roll state. However, by protecting with a protective film, it is possible to prevent the adhesion and scratches of dust etc. to the surface of the resin composition layer. It is preferable to add a step of bonding.

  The protective film is not particularly limited as long as it has a function of protecting the surface of the interlayer insulating layer, and a plastic film such as polyethylene, polypropylene, or polyester is used.

  The thickness of the interlayer insulating layer formed of a polyester film is preferably equal to or greater than the thickness of the conductor layer. Since the thickness of the conductor layer of the circuit board is usually in the range of 5 to 70 μm, the thickness of the resin composition layer is preferably 10 to 100 μm.

  The film having an interlayer insulating layer obtained in the present invention is laminated on the core substrate by peeling off the protective film of the interlayer insulating layer as an adhesive film when patterning the conductive layer to form a circuit. Structure of core base material / interlayer insulating layer / polyester film support, or structure of polyester film support / interlayer insulation / core base material / interlayer insulating layer / polyester film support in which both sides of the core base material are sandwiched between interlayer insulating layers The core substrate and the interlayer insulating layer are adhered to each other by heating, and the support made of the polyester film is peeled off.

  As a method of adhering the interlayer insulating layer to the core substrate, a method of laminating on the circuit board under reduced pressure by a vacuum laminating method is suitably used. The laminating method may be a batch method or a continuous method using a roll. Further, the adhesive film and the circuit board may be heated (preheated) as necessary before lamination.

The lamination conditions are preferably a pressure bonding temperature (laminating temperature) of 70 to 140 ° C. and a pressure bonding pressure of preferably 1 to 11 kgf / cm 2 (9.8 × 10 ^{4 to} 107.9 × 10 ⁴ N / m ² ), Lamination is preferably performed under a reduced pressure of 20 mmHg (26.7 hPa) or less. The vacuum lamination can be performed using a commercially available vacuum laminator.

  The circuit board in the present invention mainly includes a conductor layer (circuit) patterned on one or both sides of a substrate such as a glass epoxy, metal substrate, polyester substrate, polyimide substrate, BT resin substrate, thermosetting polyphenylene ether substrate, or the like. The one formed. Also included in the circuit board of the present invention is a multilayer printed wiring board in which conductor layers and insulating layers are alternately formed and a conductor layer (circuit) is patterned on one or both sides. In addition, it is preferable from the viewpoint of the adhesiveness of the insulating layer to the circuit board that the surface of the conductor circuit layer has been previously roughened by blackening or the like.

  Thus, after laminating the adhesive film on the circuit board, when the support film is peeled off, the insulating film can be formed on the circuit board by peeling and thermosetting. The conditions of heat curing are selected in the range of 20 to 180 minutes at 150 to 220 ° C, more preferably 30 to 120 minutes at 160 to 200 ° C. If the support film is not peeled off after the insulating layer is formed, it is peeled off here.

  Next, holes are formed in the insulating layer formed on the circuit board to form via holes and through holes. Drilling can be performed by a known method such as drilling, laser, or plasma, or a combination of these methods if necessary. However, drilling by a laser such as a carbon dioxide laser or YAG laser is the most common method. .

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all.

  First, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, the extending | stretching temperature orthogonal to the 1st step | paragraph extending | stretching direction is 70-170 degreeC normally, and a draw ratio is 3.0-7 times normally, Preferably it is 3.5-6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  The simultaneous biaxial stretching method can also be adopted for the production of the polyester film in the present invention. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows: The area magnification is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

  Furthermore, a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step can be applied. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, producing a film suitable as a polyester film. it can.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In this invention, it does not necessarily limit about the curing conditions at the time of forming a coating layer on a polyester film, For example, when providing a coating layer by the coating extending | stretching method (in-line coating), it is 170-280 degreeC normally. The heat treatment may be performed for 3 to 40 seconds, preferably 200 to 280 ° C. for 3 to 40 seconds.

  Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed irrespective of the coating extending | stretching method (in-line coating) or offline coating.

  The polyester film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measuring method used in the present invention is as follows.

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. It was dissolved and measured at 30 ° C.

(2) Measurement of average particle diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Surface roughness (SRa)
The center line average roughness Ra (μm) is defined as the surface roughness. It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, the center line of the extracted portion is the x axis, and the direction of the vertical magnification is the y axis. When represented by (x), the value given by the following equation is represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portion obtained from 10 cross section curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

Ra = (1 / L) ∫ 0 L | f (x) | dx

  The polyester used in the examples and comparative examples was prepared as follows.

<Manufacture of polyester>
Production Example 1 (Polyethylene terephthalate A)
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, the temperature is raised by heating, methanol is distilled off, transesterification is performed, and 4 hours are required from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, after adding 0.04 part of ethylene glycol slurry ethyl acid phosphate and 0.03 part of antimony trioxide, the temperature reached 280 ° C. and the pressure reached 15 mmHg in 100 minutes. It was 0.3 mmHg. After 4 hours, the system was returned to normal pressure to obtain polyethylene terephthalate A having an intrinsic viscosity of 0.61.

Production Example 2 (Polyethylene terephthalate B)
Agglomerates having an average particle diameter of 150 nm were obtained by dispersing the aggregates of θ-type aluminum oxide having a primary particle diameter of 30 nm obtained by heating and baking boehmite in ethylene glycol and gradually dispersing them with a sand grinder. . Next, 100 parts of dimethyl terephthalate, 65 parts of ethylene glycol and 0.09 part of magnesium acetate were placed in a reactor, and the ester exchange reaction was performed while heating and raising the temperature and distilling off methanol. Approximately 4 hours after the start of the reaction, the temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 3.0% by weight of an aluminum oxide aggregate having an average particle size of 70 nm was added, and 0.4 parts of ethylene glycol slurry ethyl phosphate and 0.03 part of antimony trioxide were added, followed by polymerization according to a conventional method. Polyethylene terephthalate B having an intrinsic viscosity of 0.63 was obtained.

Production Example 3 (Polyethylene terephthalate C)
Instead of adding aggregates having an average particle diameter of 150 nm by dispersing aggregates of θ-type aluminum oxide having a primary particle diameter of 30 nm in ethylene glycol and gradually dispersing with a sand grinder in Production Example 2, θ having an average particle diameter of 20 nm is added. A polyethylene terephthalate C is obtained in the same manner as in Production Example 2 except that 2.5 parts of an aggregate having an average particle size of 70 nm is added by dispersing the aggregate of type aluminum oxide in ethylene glycol and gradually dispersing with a sand grinder. It was.

Production Example 4 (Polyethylene terephthalate D)
Instead of adding aggregates having an average particle size of 150 nm by dispersing aggregates of θ-type aluminum oxide having a primary particle size of 30 nm in ethylene glycol and gradually dispersing with a sand grinder in Production Example 2, θ having a primary particle size of 30 nm is added. A polyethylene terephthalate D was obtained in the same manner as in Production Example 2 except that 3.0 g of an aggregate having an average particle size of 300 nm was added by dispersing the aggregate of type aluminum oxide in ethylene glycol and gradually dispersing with a sand grinder. It was.

Production Example 5 (Polyethylene terephthalate E)
In Production Example 2, agglomerates of θ-type aluminum oxide having a primary particle size of 30 nm are dispersed in ethylene glycol and gradually dispersed by a sand grinder, so that an average particle having no tendency to aggregate is added instead of adding an aggregate having an average particle size of 150 nm Polyethylene terephthalate E was obtained in the same manner as in Production Example 2, except that 1.0 part of α-type aluminum oxide having a diameter of 320 nm was added.

Production Example 6 (polyethylene terephthalate F)
Instead of adding aggregates having an average particle size of 150 nm by dispersing aggregates of θ-type aluminum oxide having a primary particle size of 30 nm in ethylene glycol and gradually dispersing with a sand grinder in Production Example 2, θ having a primary particle size of 30 nm is added. Polyethylene terephthalate F in the same manner as in Production Example 2 except that 1.0 g of aggregate having an average particle size of 1.0 μm is added by dispersing aggregates of type aluminum oxide in ethylene glycol and gradually dispersing with a sand grinder. Got.

Production Example 7 (polyethylene terephthalate G)
Instead of adding aggregates having an average particle diameter of 150 nm by dispersing aggregates of θ-type aluminum oxide having a primary particle diameter of 30 nm in ethylene glycol and gradually dispersing with a sand grinder in Production Example 2, the average particle diameter is 0.4 μm. Polyethylene terephthalate G was obtained in the same manner as in Production Example 2 except that 0.2 parts of the above crosslinked polymer particles were added.

Production Example 8 (polyethylene terephthalate H)
In the same manner as in Production Example 7, except that 0.5 parts of synthetic calcium carbonate particles having an average particle diameter of 0.6 μm are added instead of adding 0.2 parts of crosslinked polymer particles having an average particle diameter of 0.4 μm in Production Example 7. Thus, polyethylene terephthalate H was obtained.

Production Example 9 (polyethylene terephthalate I)
In the same manner as in Production Example 7, except that 0.5 part of aggregated silica particles having an average particle diameter of 3.2 μm is added instead of adding 0.2 part of crosslinked polymer particles having an average particle diameter of 0.4 μm in Production Example 7. Polyethylene terephthalate I was obtained.

Production Example 8 (polyethylene terephthalate J)
In the same manner as in Production Example 7 except that 0.3 part of spherical silica particles having an average particle diameter of 0.4 μm is added instead of adding 0.2 part of crosslinked polymer particles having an average particle diameter of 0.4 μm in Production Example 7. Polyethylene terephthalate J was obtained.

Production Example 9 (polyethylene terephthalate K)
In the same manner as in Production Example 7, except that 0.5 parts of spherical silica particles having an average particle diameter of 0.6 μm were added instead of adding 0.2 parts of crosslinked polymer particles having an average particle diameter of 0.4 μm in Production Example 7. Polyethylene terephthalate K was obtained.

Production Example 10 (Polyethylene terephthalate L )
In the same manner as in Production Example 7, except that 0.5 parts of synthetic calcium carbonate particles having an average particle diameter of 0.8 μm are added instead of adding 0.2 parts of crosslinked polymer particles having an average particle diameter of 0.4 μm in Production Example 7. Thus, polyethylene terephthalate L was obtained.

(Manufacture of polyester film)
The above polyesters A to L were mixed at the compounding ratios shown in Table 1 and mixed into A layer, B layer, and C layer as raw materials, each fed to two twin-screw extruders and melted at 285 ° C. In contrast, the ratio of the extrusion amount of each layer was adjusted so as to be the thickness of the A layer, the B layer, and the C layer, and the three types and three layers were co-extruded on a casting drum cooled to 20 ° C. and cooled and solidified. Thus, a non-oriented sheet was obtained. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., then subjected to a preheating step in the tenter and subjected to transverse stretching of 4.6 times at 120 ° C., followed by heat treatment at 225 ° C. for 10 seconds, 10% relaxation was added in the width direction at 180 ° C. to obtain polyester films having thicknesses shown in Tables 1 to 3 below. The characteristics of the polyester film obtained by the above method are shown in Table 1 below.

<< Epoxy resin composition >>
20 parts of liquid bisphenol A type epoxy resin (“Epicoat 828EL” manufactured by Japan Epoxy Resin Co., Ltd.), 20 parts of brominated bisphenol A type epoxy resin (YDB-500 manufactured by Toto Kasei Co., Ltd.), cresol novolac type epoxy resin (epoxy) Equivalent 215, softening point 78 ° C., Dainippon Ink Chemical Co., Ltd. Epicron N-673) 20 parts, terminal epoxidized polybutadiene rubber (Nagase Kasei Kogyo Co., Ltd. Denarex R-45EPT) 15 parts are stirred in MEK. The solution was dissolved while heating, and brominated phenoxy resin varnish (non-volatile content 40% by weight, bromine content 25% by weight, solvent composition, xylene: methoxypropanol: methyl ethyl ketone = 5: 2: 8, YPB- manufactured by Toto Kasei Co., Ltd. 40-PXM40) 50 parts, 2,4-diamino as epoxy curing agent 6- (2-Methyl-1-imidazoliethyl) -1,3,5-triazine / isocyanuric acid adduct 4 parts, 2 parts of finely pulverized silica, 4 parts of antimony trioxide and 5 parts of calcium carbonate A composition varnish was prepared.

<< Resin composition varnish application to polyester film: Formation of interlayer insulation layer >>
The resin composition varnish produced by the above method is applied to the surface of the A layer of the polyester film obtained in Examples 1 to 4 and Comparative Examples 1 to 4 with a die coater so that the resin thickness after drying becomes 70 μm. It apply | coated and dried at 80-120 degreeC (average 100 degreeC), and the interlayer insulation layer which made the polyester film the support body was produced.

  In Comparative Example 4, the polyester film was wrinkled during drying after the resin composition varnish was applied, and a product was not obtained.

<< Surface property A of interlayer insulating layer >>
The surface corresponding to the polyester film of the obtained interlayer insulating layer was observed by SEM, and the presence or absence of transfer of scratches affecting the wiring was evaluated as follows. The results are shown in Table 4.

○: Transfer of scratches that adversely affect the wiring is not seen. △: Transfer marks of scratches that can be used without problems in practical use are observed. ×: There are clear scratches of traces that can adversely affect circuit wiring. Transfer marks can be seen Among the above criteria, those above Δ are levels that can be used without any problem in actual use.

<< Surface property B of interlayer insulating layer >>
The surface corresponding to the polyester film of the obtained interlayer insulating layer was observed with an SEM, and the presence or absence of a dent affecting the wiring was evaluated as follows. The results are shown in Table 5.

◎: No large dent that adversely affects the wiring is observed ○: The dent is slightly inferior, and some large dents are seen △: The size of the dent that can be used without any practical problem is seen ×: There is a large dent There are dents that adversely affect circuit wiring. Among the above criteria, those above Δ are levels that can be used without problems in actual use.

《Cost advantage》
The obtained characteristics and the cost evaluation related to the production such as yield are evaluated as follows, and the results are shown in Table 2 below.

◯: Advantage in terms of cost Δ: Slightly inferior in cost ×: Inferior in cost Among the above criteria, those above Δ are at a level that can be used without problems in actual use.

  In Comparative Example 4, the polyester film was wrinkled during drying after the resin composition varnish was applied, and a product was not obtained.

  The polyester film of the present invention can be suitably used as a support for forming a film-like interlayer insulating material used for, for example, a multilayer printed wiring board produced by a build-up build-up method.

Claims (1)

It is a coextruded biaxially oriented laminated polyester film consisting of at least three layers and having a film thickness of 15 to 50 μm , one outermost layer having a thickness of 0.4 to 5 μm, and the average of primary particles in the outermost layer A support polyester film for an interlayer insulating material, comprising 0.1 to 0.8 % by weight of an aluminum oxide aggregate having a particle size of 5 to 40 nm, and having an average particle size of 50 to 400 nm .