JP2001191405A - Biaxially oriented film and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive film for a flexible circuit board having a dimensional stability and flatness in use at a high temperature. SOLUTION: A biaxially oriented film composed of a polyester containing polyethylene-2,6-naphthalene dicarboxylate as a major component shows shrinkage in the lengthwise direction of not less than 0% to not more than 1% and expansion in the widthwise direction of not less than 0% to not more than 0.5% when heated at 200 deg.C for 10 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented film having excellent dimensional stability and flatness when used at a high temperature, and a method for producing the same. The present invention relates to a biaxially oriented film composed of a polyester containing polyethylene-2,6-naphthalenedicarboxylate as a main component and a method for producing the film.

[0002]

2. Description of the Related Art A flexible circuit is an electric circuit arranged on a flexible substrate. The flexible circuit is formed by attaching a metal foil to a film serving as a substrate or performing plating and the like, followed by etching. It is formed. The substrate on which the circuit is formed is further subjected to heat treatment, mounting of circuit components, and the like, and is put to practical use as a component of an electric or electronic device.

Conventionally, as a film for a flexible circuit board, polyimide (hereinafter abbreviated as "PI") has been used because of its good adhesion to a circuit and heat resistance during soldering when mounting circuit components. A) film is commonly used. On the other hand, polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”) film is used as a part of a film for a flexible circuit board because it is inexpensive and has good chemical resistance and insulation properties. .

[0004] In recent years, portable electric and electronic devices such as notebook personal computers and mobile phones have rapidly become widespread, and the miniaturization of these portable devices has been actively pursued. However, there is a demand to provide a function that is equal to or more than the function provided in the conventional model even if the size is reduced, and accordingly, a reduction in the size and density of the circuit is required.

[0005] While such advanced technology is required, competition for price reduction due to the recent spread of portable devices is increasing. However, the PI film conventionally used as a film for a flexible circuit board is not available. The price is high, and as long as it is used, there is a limit in reducing the price of portable devices.

[0006] In addition to the fact that PI films are expensive,
Because of its high hygroscopicity and large dimensional change when absorbing moisture, ignoring the humidity of the film during processing may cause a decrease in adhesion to metal. ing. Furthermore, if the solvent for dissolving the PI resin used in manufacturing the PI film remains in the film, there is a problem in the quality of the circuit board.

On the other hand, PET films are inexpensive and suitable for cost reduction as films for flexible circuit boards, but have the disadvantage of poor heat resistance. For example, in the heat treatment in the process of membrane switch, the dimensional change of the film becomes a problem, and in the soldering in the mounting of circuit parts, the flatness of the film becomes a problem. Is unusable.

[0008] Advances in soldering techniques for mounting circuit components have made it possible to lower the soldering temperature of recent reflow soldering compared to conventional flow soldering, but PET films still have heat resistance. Run out. On the other hand, the current situation is that the PI film has excessive solder heat resistance.

For these reasons, a search has been made for a plastic film to replace the PI film, and a relatively inexpensive polyethylene-2,6-naphthalenedicarboxylate film has attracted attention among plastic films having heat resistance. It became so.

The use of a polyethylene-2,6-naphthalenedicarboxylate film as a film for a flexible circuit board has been proposed, for example, in Japanese Patent Application Laid-Open No. 62-93991. However, the conventionally proposed polyethylene-2,6-naphthalenedicarboxylate film has insufficient performance with respect to the dimensional stability at high temperatures required in connection with the recent increase in circuit density. However, after the soldering in the circuit component mounting process, wrinkles are formed in the film, and the planarity of the circuit is lost and irregularities are generated.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and when used for a flexible circuit board, has excellent dimensional stability at a high temperature, that is, at a circuit component mounting temperature. It is an object of the present invention to provide a relatively inexpensive biaxially oriented film having the same or higher planarity of a circuit after mounting circuit components as compared with a conventional PI film.

[0012]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the dimensional change of a film under a high temperature is defined as a shrinkage behavior in the longitudinal direction of the film within a certain range, Further, it has been found that by setting the stretching behavior in the width direction to a specific range, a film for a flexible circuit board having excellent flatness and dimensional stability can be provided.

That is, the present invention relates to polyethylene-2,6
A biaxially oriented film comprising a polyester containing naphthalene dicarboxylate as a main constituent,
When heat-treated at 00 ° C. for 10 minutes, the film shrinks by 0% or more and 1% or less in the longitudinal direction and 0% or more by 0.1% or more in the width direction.
A biaxially oriented film characterized by being stretched by 5% or less,
And a method for producing the above-mentioned biaxially oriented film by further performing a thermal relaxation treatment on the biaxially stretched and heat-set film.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[Polyester] In the present invention, the polyester constituting the biaxially oriented film is polyethylene-
2,6-Naphthalenedicarboxylate is a main component. Polyethylene-2,6 in the present invention
-Naphthalenedicarboxylate may be a homopolymer thereof, or a copolymer having a copolymer component in a range of 20 mol% or less. The copolymer component in the case of a copolymer is
Acid components other than 2,6-naphthalenedicarboxylic acid and / or
Or a glycol component other than ethylene glycol, wherein the ratio (mol%) of the acid component other than 2,6-naphthalenedicarboxylic acid to the total acid component and the ratio (mol%) of the glycol component other than ethylene glycol to the total glycol component )) (Copolymerization ratio) is 0.5 to 20 mol%
Is preferably within the range.

Since the inherent properties of polyethylene-2,6-naphthalenedicarboxylate having a copolymerization ratio of more than 20 mol% are lost, excellent dimensional stability and flatness in use of the film at a high temperature cannot be ensured. Absent.

Acid components other than 2,6-naphthalenedicarboxylic acid include oxalic acid, adipic acid, phthalic acid, sebacic acid, dodecanedicarboxylic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid,
Dicarboxylic acids such as 4'-diphenyldicarboxylic acid, phenylindanedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid; oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; can do.

Examples of glycol components other than ethylene glycol include propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, cyclohexane methylene glycol, neopentyl glycol, ethylene oxide adduct of bisphenolsulfone, and ethylene oxide adduct of bisphenol A. And dihydric alcohols such as diethylene glycol and polyethylene oxide glycol.

Polyethylene-2,6-naphthalenedicarboxylate is obtained by blocking a terminal hydroxyl group and / or a carboxyl group partially or entirely with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. Alternatively, it may be one obtained by copolymerizing a very small amount of a trifunctional or higher ester-forming compound such as glycerin or pentaerythritol within a range where a substantially linear polymer can be obtained.

[Polymer Additive] In the biaxially oriented film of the present invention, polyethylene-2,6
Polymers other than -naphthalenedicarboxylate can be mixed and used within a range in which the inherent characteristics of polyethylene-2,6-naphthalenedicarboxylate can be maintained.
In addition to the polymer, additives such as a stabilizer, a lubricant, and a flame retardant can be contained.

In order to impart lubricity to the biaxially oriented film of the present invention, it is preferable to contain a small proportion of inert fine particles as a film constituent. Examples of such inert fine particles include inorganic particles such as spherical silica, porous silica, calcium carbonate, alumina, titanium dioxide, kaolin clay, barium sulfate, and zeolite, or organic particles such as silicon resin particles and crosslinked polystyrene particles. Can be. Inorganic particles are preferably synthetic products, rather than natural products, for reasons such as uniform particle size,
Inorganic particles of any crystal morphology, hardness, specific gravity, and color can be used.

The inert fine particles have an average particle size of 0.05 μm.
It is preferably in the range of not less than m and not more than 5.0 μm. The lower limit of the average particle size of the inert fine particles is more preferably 0.1 μm, and the upper limit is more preferably 3.0 μm.

The content of inert fine particles is 0.001.
It is preferable that the amount is not less than 1.0% by weight and not more than 1.0% by weight. The lower limit of the content of the inert fine particles is more preferably 0.03% by weight, and the upper limit is more preferably 0.5% by weight.

The inert fine particles to be added to the film may be a single component selected from those exemplified above, or a multi-component containing two or more than three components.

The timing of adding the inert fine particles is not particularly limited as long as it is a stage before forming the polyethylene-2,6-naphthalenedicarboxylate into a film. For example, the inert fine particles may be added at the polymerization stage. It may be added at the time.

[Manufacturing conditions of biaxially stretched film] The biaxially oriented film of the present invention can be manufactured by further subjecting a biaxially stretched and heat-set film to a thermal relaxation treatment.
For example, a polyethylene-2,6-naphthalenedicarboxylate containing lubricant fine particles is dried, melt-extruded, biaxially stretched, heat-set, and then, if necessary, heat-relaxed. It can be manufactured by relaxation treatment.

The above-mentioned biaxially stretched film is obtained by, for example, rapidly solidifying a molten resin extruded from a T-die on a cooling drum to obtain an unstretched film. After stretching 2.5 to 4.0 times, it is stretched 3 to 6 times in the transverse direction, and Tg + 10
It can be obtained by heat setting at a temperature of 0 ° C. or more and Tg + 140 ° C. or less for 1 to 10 seconds. Stretching can be performed by a commonly used method, for example, a method using a roll or a method using a stenter, and may be simultaneously stretched in the longitudinal direction and the transverse direction, or may be sequentially stretched in the longitudinal direction and the transverse direction. Good. Here, Tg represents the secondary transition temperature of the polyester.

If necessary, for example, a water-dispersible coating is applied to one or both surfaces of the film after longitudinal stretching, for example, after longitudinal stretching, so that the film has an adhesive property or lubricity of 0.01 to 0. .1 μm can be formed.

The conditions for forming the biaxially stretched film are not specified, but it is desirable to select conditions that reduce the anisotropy at both ends of the film, minimize the heat shrinkage as much as possible, and have good flatness. It is difficult to satisfy all of them, but relatively desirable conditions are as follows.

The longitudinal stretching ratio is preferably 2.5 to 4.0 times. The upper limit of the longitudinal stretching ratio is more preferably 3.6 times, and the lower limit is more preferably 3.0 times. When the longitudinal stretching ratio is less than 2.5 times, unevenness in thickness may be deteriorated. Further, when the ratio exceeds 4.0 times, the orientation in the longitudinal direction becomes strong, the residual stress in the longitudinal direction becomes strong, and when the film is softened by heating in the heat treatment step, both ends are grasped by the grasping tool. Therefore, the films do not move with each other, but the central part moves to the upstream side, and the anisotropy at both ends may become strong. Although this phenomenon cannot be prevented by longitudinal and horizontal sequential biaxial stretching, it can be somewhat reduced by making the film relatively horizontal.

The transverse stretching ratio is preferably 3 to 6 times. The upper limit of the transverse stretching ratio is more preferably 5.0 times, and the lower limit is more preferably 3.6 times. When the transverse stretching ratio is less than 3.0 times, thickness unevenness may be deteriorated. On the other hand, if it exceeds 6.0 times, cutting may occur frequently during stretching.

The heat setting temperature is Tg + 100 ° C. or higher and Tg + 1.
40 ° C. or lower is preferred. If the heat setting temperature is lower than Tg + 100 ° C., the dimensional change rate is large, and when heat shrinkage is reduced by post-treatment, wrinkles and the like are generated to deteriorate the planarity, and oligomers are easily precipitated and whitened. When the heat setting temperature exceeds Tg + 140 ° C., the anisotropy of the both ends increases, the film tends to be opaque, and the thickness unevenness increases. It is effective to narrow the guide rail of the gripper in the heat setting process and perform the heat relaxation process to reduce the heat shrinkage rate, particularly in the lateral direction. The width relaxation rate is preferably 0.5 to 5%. If it is less than 0.5%, the effect is small, and if it is 5% or more, the flatness deteriorates. Usually, the gripper releases the film when the film temperature is 100 ° C or lower, but releases the film at 150 to 120 ° C.
Lowering the take-up tension is effective in reducing the heat shrinkage in the vertical direction. If this temperature exceeds 150 ° C., the flatness deteriorates, and if it is lower than 120 ° C., the effect is small. The release from the gripper may be separated by inserting a blade such as a knife or a razor near the gripper.

[Heat Relaxation Treatment] The biaxially oriented film of the present invention can be obtained by further subjecting the film formed with care as described above to a heat relaxation treatment. Although the method of the thermal relaxation treatment is not specified, a suspension type thermal relaxation treatment method is particularly preferable. In the suspension type thermal relaxation treatment method, after the tension on the delivery side of the film to be processed is cut off by a nip roller, the film is suspended downward by its own weight via a roller installed above while preheating to ensure flatness, and the After heating on the way, the film is turned in a substantially horizontal direction by a lower roller, and the film is cooled and the winding tension is cut off by a nip roller while maintaining flatness, and then winding. The tension between the upper and lower rollers can be achieved by installing a tension pickup in the processing section, adjusting the motor of each nip roller on the sending-out and winding-up sides.

The tension at the time of the thermal relaxation treatment is preferably from 1 kPa to 300 kPa. The upper limit of the tension during this heat relaxation treatment is more preferably 250 kPa,
It is particularly preferable that the pressure is 00 kPa. Further, the lower limit of the tension during the heat relaxation treatment is more preferably 10 kPa, and particularly preferably 20 kPa. If the tension at the time of the thermal relaxation treatment is less than the above lower limit, the flatness of the film is deteriorated, and the film is liable to meander during the conveyance of the film. If the upper limit is exceeded, the dimensional change tends to increase, which is not preferable.

The hanging distance during the thermal relaxation treatment is 1 m or more and 10
m or less is preferable. If the hanging distance is less than 1 m, the heating range is short, so that the processing speed is slow and the productivity is poor, which is not preferable. On the other hand, if it exceeds 10 m, the film tends to meander during transportation, and the flatness is also poor, which is not preferable.
In the thermal relaxation treatment, there is no particular limitation as long as there are measures to overcome these. The heating method is not limited, but infrared heating is preferable because it can be heated immediately.

The temperature of the thermal relaxation treatment is Tg or more and Tg + 14.
0 ° C. or lower is preferred. The upper limit of the thermal relaxation treatment temperature is Tg + 1
The temperature is more preferably 20 ° C., and particularly preferably Tg + 110 ° C. Further, the lower limit of the heat relaxation treatment temperature is more preferably Tg + 20 ° C., and Tg + 70 ° C.
Is particularly preferred. If the heat relaxation treatment temperature is lower than Tg, it is difficult to reduce the dimensional change rate and the amount of bending at 200 ° C. On the other hand, when the temperature exceeds Tg + 140 ° C., the flatness tends to be deteriorated, and the oligomer may precipitate and the film may become white. This whitening depends on the pressure history. For example, when the hanging belt is transported over the film portion of the film roll, the portion in contact with the belt is likely to whiten even at Tg + 140 ° C. or lower, so care must be taken. The film temperature is desirably measured using a non-contact infrared thermometer (for example, a Burns radiation thermometer). According to this suspension-type thermal relaxation treatment method, the dimensional change rate can be kept within the range of the present invention even for films near both ends during film formation.

[Intrinsic Viscosity of Film] The polyester constituting the biaxially oriented film of the present invention has an intrinsic viscosity of 0.4.
It is preferably from 7 to 0.90 dl / g. The lower limit of the intrinsic viscosity is more preferably 0.50 dl / g, and the upper limit is more preferably 0.80 dl / g. If the intrinsic viscosity is less than 0.47 dl / g, the film becomes brittle, and when the film is cut into a predetermined size or a hole for fixing for mounting circuit components is formed, burrs are generated on an end face. Occasionally, a crack may be formed from a part of the burr, and the film may break during the processing step, or an abnormality such as an extremely low insulation performance of the substrate film may occur. The intrinsic viscosity of the film is 0.9
If it exceeds 0 dl / g, the intrinsic viscosity of the polyethylene-2,6-naphthalenedicarboxylate polymer needs to be considerably increased, and the ordinary synthesis method requires a long time for polymerization, resulting in poor productivity. In addition, a special polymerization method (such as solid-phase polymerization) requires a dedicated facility, which increases production cost, which is not preferable.

[Refractive Index in Thickness Direction] The biaxially oriented film of the present invention preferably has a refractive index in the thickness direction in the range of 1.495 to 1.530. The lower limit of the refractive index in the thickness direction is preferably 1.498, and the upper limit is preferably 1.520. If the refractive index in the thickness direction is less than 1.495, the bending resistance of the film deteriorates, and the processability such as cutting, punching, and perforation deteriorates. On the other hand, when the refractive index in the thickness direction exceeds 1.530, unevenness in the thickness of the film becomes large, and wrinkles (flutes) easily occur on the film surface.

[Film Thickness] The thickness of the biaxially oriented film of the present invention is preferably in the range of 12 μm to 250 μm. The lower limit of this thickness is more preferably 25 μm, and particularly preferably 38 μm. Further, the upper limit of the thickness is more preferably 200 μm, and particularly preferably 150 μm.

When the thickness is less than 12 μm, the insulating performance of the film is insufficient, and the bending rigidity of the film for a circuit board is insufficient. On the other hand, if the thickness exceeds 250 μm, the film has insufficient flexing resistance, and when an external force is applied, the substrate film will not crack or return in a broken state.

[Surface Roughness] The biaxially oriented film of the present invention preferably has a surface roughness (Ra) of 3 nm or more.
If the surface roughness (Ra) is less than 3 nm, the film has poor slipperiness, and when the film is wound up on a roll, transfer or folding wrinkles are generated due to air pockets, and the flatness is impaired. Become. It is very difficult to wind up without causing such a drawback, and even if it is wound up, the production efficiency deteriorates. Although the upper limit of the surface roughness is not specified, it is preferably 1000 nm or less in view of the design of the film.

[Coefficient of friction] The coefficient of friction of the biaxially oriented film of the present invention is preferably 0.5 or less, particularly preferably 0.1 or less.
4 or less. When the coefficient of friction exceeds 0.5, transportability,
The winding property becomes difficult, which is not preferable.

[Amount of Curvature] When the film is slit into small widths and allowed to stand on a flat surface without wrinkling without applying tension, the film taken from the vicinity of the center in the width direction at the time of film formation is substantially linear. And the film nearer to both ends is more curved.
When the deviation from a straight line per 1 m of length is the amount of curvature,
The amount of curvature of the film is 10 mm or less per 1 m, and 5 m
m or less, particularly preferably 4 mm or less. If the amount of bending exceeds 5 mm, particularly more than 10 mm, the film may meander when performing various processes in the process of manufacturing the flexible circuit board, resulting in a defective product.

[Dimensional Stability] The biaxially oriented film of the present invention has a dimensional stability when heated at 200 ° C. for 10 minutes.
The film must shrink in the longitudinal direction of the film by 0% or more and 1% or less, and extend in the width direction by 0% or more and 0.5% or less.

If the dimensional stability after the heat treatment at a temperature of 200 ° C. for 10 minutes is out of the range described above, the dimensional change of the film at the time of curing after bonding the metal foil or the drying treatment after printing. The dimensional change of the film is large,
It is not preferable because warpage occurs in the circuit board and wrinkles and irregularities are partially generated in the flexible circuit after soldering at the time of mounting the circuit components, resulting in poor flatness.

At this time, the flatness is ensured by contracting in the longitudinal direction of the film and expanding in the width direction.

[0047]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited to these examples.

(1) Average particle size of particles CP-50 type centrifugal particle size analyzer (Centrifug, manufactured by Shimadzu Corporation)
al Particle Analyzer). The particle size corresponding to 50 mass% was read from the integrated curve of the particles of each particle size and the remaining amount calculated based on the obtained Liaoshin sedimentation curve, and this value was defined as the above average particle size ("particle size" Measuring Technology ”Published by Nikkan Kogyo Shimbun, 197
5 years, see pages 242-247).

(2) Average particle size when the inert particles are agglomerated particles When the inert fine particles as the added lubricant are secondary particles resulting from the aggregation of the primary particles, the average particle size is determined by the method described in (1). Since the particle size obtained by diameter measurement may be smaller than the actual average particle size, the following method was employed. The film containing the particles is made into an ultra-thin section with a thickness of 100 nm in the cross-sectional direction,
Transmission electron microscope (for example, TEM-1200E manufactured by JEOL Ltd.)
Using X), particles were observed at a magnification of about 10,000 times, and aggregated particles (secondary particles) were observed. Using this photograph, the diameter equivalent to the circular area of each particle was measured for 1000 particles using an image analyzer or the like, and the number averaged particle diameter was calculated as 2
The secondary particle size was determined. The particle type was identified by SEM-XMA,
It can be performed by using a quantitative analysis of a metal element by ICP or the like. The average primary particle size is determined by setting the magnification of the transmission electron microscope to 1
The measurement was carried out in accordance with the method of measuring the average secondary particle size except for photographing at a magnification of 100,000 to 1,000,000.

(3) Amount of copolymerization component of ethylene-2,6-naphthalenedicarboxylate A film sample was measured with a solvent (CDCl ₃ : CF ₃ COO).
(D = 1: 1), 1H-NMR measurement is performed, and calculation is made based on the integration ratio of each signal obtained.

(4) Thermal Dimensional Change Rate The film is held in an oven set at a temperature of 200 ° C. for 10 minutes without tension, and the dimensional change before and after the heat treatment is calculated as the thermal dimensional change rate by the following equation. . Thermal dimensional change rate = ((L ₀ −L) / L ₀ ) × 100 where L ₀ : distance between gauge points before heat treatment, L: distance between drift points after heat treatment

(5) Film Thickness The thickness of the film was determined by measuring 100 points with an external micrometer and calculating the average value.

(6) Surface Roughness (Center Line Surface Roughness Ra) Both the front and back sides of the film are measured with a surface roughness meter (Surfcom 111A, Tokyo Seimitsu Co., Ltd.), and the average value is calculated to obtain the surface roughness.

(7) Coefficient of friction Using a slippery measuring device (manufactured by Toyo Tester) according to ASTM D1894-63, a dynamic friction coefficient (μd) was measured with a glass plate as a thread plate and a load of 1 kg.

(8) Amount of Curve A film having a length of 20 m is sampled from a film roll, and is brought into close contact with a horizontal floor without distortion. Next, the starting point and the end point of one end in the film width direction are connected by a straight line, and the amount of deviation in the film width direction at the longitudinal middle point (10 m point) with respect to this straight line is determined. I do. This value is converted into a value per 1 m of the film length, and is defined as a bending amount.

(9) Evaluation of Flatness of Flexible Circuit A flexible circuit board prepared on the assumption of reflow soldering at the time of component mounting is heat-treated at 200 ° C. for 10 minutes. After placing the processed flexible circuit board on a flat plate having a thin ink layer on the surface, a sheet of the same size as the substrate is prepared on a separately prepared flat plate and allowed to stand still. The ratio of the area of the ink attached to the sheet to the area of the sheet is calculated by the following equation. This evaluation was performed with n = 20, and the evaluation was made based on the following criteria. Flatness = (Area of ink on paper / area of paper) × 100 (%) ○: Good (90% or more for all 20 samples) △: Usable (60% or more for all 20 samples) ×: Unusable (Some of the 20 samples have less than 60%)

(10) Overall Evaluation The results were comprehensively evaluated for the flatness of the flexible circuit, the amount of bending of the film, and the coefficient of friction. ：: good (all of the above results are good) △: slightly poor (some of the above results have some unsatisfactory parts) ×: bad (one of the above results has a fatal defect)

(11) Secondary transition temperature (Tg) 10 mg of a film sample was obtained by DSC (V
4. After melting at 300 ° C. for 5 minutes using an OB2000 model), the mixture is rapidly cooled to room temperature or lower, and then heated at a rate of 20 ° C./min to measure the secondary transition temperature.

[Examples 1, 4 to 6 and Comparative Example 1] Polyethylene-2,6-naphthalenediene containing 0.2% by weight of silica particles having an average particle diameter of 0.3 μm and having an intrinsic viscosity of 0.60. Melt extrusion of carboxylate from die slit,
It was cooled and solidified on a casting drum to produce an unstretched film.

The unstretched film was successively biaxially stretched in the longitudinal direction (machine axis direction) and the transverse direction (width direction) in the order shown in Table 1, heat-fixed, and wound on a roll. Then I
Using a heating zone by an R heater, relaxation treatment was performed in a state of being suspended at the temperature and tension shown in Table 1, and a biaxially oriented film having a thickness shown in Table 1 was obtained. The Tg of the biaxially oriented film was 121 ° C.

Further, an adhesive is applied to one side of the film, a 1/2 oz copper foil (18 μm thick) is attached, and a predetermined circuit is formed by etching the copper foil.
Drying was performed at 0 ° C. for 10 minutes to obtain a flexible circuit board. Table 1 shows the evaluation results of the physical properties of the biaxially oriented film and the flatness of the flexible circuit board.

Example 2 Copolymerized polyester having an intrinsic viscosity of 0.60 (ethylene 2,6-naphthalenedicarboxylate unit 90 mol%, bis (4- (2-hydroxyethoxy) phenyl) sulfone-2,6-naphthalene) A biaxially oriented film was formed in the same manner as in Example 1 except that a dicarboxylate unit (abbreviated as BPS-EO in Table 1) was used (10 mol%), to prepare a flexible circuit board. Table 1 shows the evaluation results of the physical properties of the biaxially oriented film and the flatness of the flexible circuit board. The biaxially oriented film had a Tg of 123 ° C.

Example 3 Copolymerized polyester having an intrinsic viscosity of 0.60 (ethylene 2,6-naphthalenedicarboxylate unit 85 mol%, ethylene isophthalate unit (abbreviated as IA in Table 1) 15 mol%, ethylene glycol 100 mol) %), A biaxially oriented film was formed in the same manner as in Example 1 to prepare a flexible circuit board. Table 1 shows the evaluation results of the physical properties of the biaxially oriented film and the flatness of the flexible circuit board. The biaxially oriented film had a Tg of 113 ° C.

[Comparative Example 2] A biaxially oriented film was formed in the same manner as in Example 1 except that the relaxation treatment in the suspended state was omitted, to prepare a flexible circuit board. Table 1 shows the evaluation results of the physical properties of the biaxially oriented film and the flatness of the flexible circuit board.

Comparative Example 3 Copolymerized polyester having an intrinsic viscosity of 0.60 (75 mol% of ethylene 2,6-naphthalenedicarboxylate unit, 25 mol% of ethylene isophthalate unit (abbreviated as IA in Table 1), 100 mol of ethylene glycol %), A biaxially oriented film was formed in the same manner as in Example 1 to prepare a flexible circuit board. Table 1 shows the evaluation results of the physical properties of the biaxially oriented film and the flatness of the flexible circuit board. The Tg of the biaxially oriented film was 108 ° C.

Comparative Example 4 A film was formed in the same manner as in Example 1 except that a film was formed under the conditions shown in Table 1 using polyethylene terephthalate having an intrinsic viscosity of 0.60 (main component polymer in Table 1; abbreviated as PET). An axially oriented film was formed to produce a flexible circuit board. Table 1 shows the evaluation results of the physical properties of the biaxially oriented film and the flatness of the flexible circuit board.
The Tg of the biaxially oriented film was 78 ° C.

[0067]

[Table 1]

[0068]

According to the present invention, it is possible to obtain a film for a flexible circuit board which is excellent in dimensional stability and flatness in use at a high temperature and relatively inexpensive.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05K 1/03 670 H05K 1/03 670Z // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7: 00 C08L 67:02 C08L 67:02 (72) Inventor Susumu Taguchi 1357, Nanjo, Anpachi-cho, Anpachi-gun, Gifu Prefecture Teijin Limited Gifu Office F-term (reference) 4F073 AA29 BA23 BB01 GA01 HA05 4F210 AA26 AA26E AB07 AG01 AH36 QC05 QG01 QG18 QW12 4J029 AA03 AB07 AC01 AD01 AD10 AE18 BA02 BA03 BA04 BA05 BB13A BD06A BD07A BF09 BF17 BH02 CA01 CA02 CA06 CB01 CC03 CC

Claims (11)

[Claims] 1. A biaxially oriented film made of a polyester containing polyethylene-2,6-naphthalenedicarboxylate as a main constituent, and when heated at 200 ° C. for 10 minutes, 0% or more in the longitudinal direction of the film. A biaxially oriented film, which shrinks by 1% or less and stretches in a width direction by 0% or more and 0.5% or less. 2. The method for producing a biaxially oriented film according to claim 1, wherein the film that has been biaxially stretched and heat set is further subjected to a thermal relaxation treatment. 3. A heat relaxation treatment is applied in a suspended state,
The method for producing a biaxially oriented film according to claim 2, wherein the transport tension is in the range of 1 kPa to 300 kPa. 4. The method for producing a biaxially oriented film according to claim 3, wherein the temperature during the heat relaxation treatment in the suspended state is not lower than Tg of the polyester and not higher than Tg + 140 ° C. 5. The polyester, wherein the copolymer component is 0.5 to 0.5%.
The biaxially oriented film according to claim 1, which is a polyethylene-2,6-naphthalenedicarboxylate copolymer containing 20 mol%. 6. The polyester has an intrinsic viscosity of 0.47 to 0.47.
The biaxially oriented film according to claim 1, wherein the biaxially oriented film has a refractive index in the thickness direction of the film of 0.90 dl / g and 1.495 to 1.530. 7. A film having a thickness of not less than 12 μm and not more than 250 μm.
2. The biaxially oriented film according to claim 1, which is not more than m. 8. The biaxially oriented film according to claim 1, wherein at least one surface of the film has a surface roughness (Ra) of 3 nm or more. 9. The biaxially oriented film according to claim 1, wherein the coefficient of friction of at least one surface of the film is 0.5 or less. 10. The amount of curvature of the film is 1 m in film length.
2. The biaxially oriented film according to claim 1, wherein the thickness is 5 mm or less. 11. The biaxially oriented film according to claim 1, which is used for a flexible circuit board.