JPH11138629A - Co-biaxially stretched polyester film and manufacturing thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film which is free from its stretching break and can be stretched at an area stretching magnification over a wide range of temperature, and further, shows high strength, wear resistance, dimensional stability and superb antistretching properties as well as a method for manufacturing the film. SOLUTION: This method for manufacturing a biaxially stretched polyester film includes a first-stage stretching step to concurrently biaxially stretch an unstretched cast film in the longitudinal and the crosswise direction at an area stretching magnification of 2-7 times within the temperature range of (glass transition temperature Tg+25) deg.C-(Tg+45) deg.C and a second-stage stretching step to concurrently biaxially stretch the cast film in the longitudinal and the crosswise direction at an area stretching magnification of 4-20 times within the temperature range of (Tg-15) deg.C-(Tg+10) deg.C following the first-stage stretching step. In addition, at least, either of the ratio R1 (IMD/ IND) of peak intensity (IMD, IND) in the longitudinal and the thickness direction or the ratio R2 (ITD/IND) of peak intensity (ITD/IND) in the crosswise and the thickness direction as measured by the laser Raman scattering method is 6 or more as the characteristics of this biaxially stretched polyester film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simultaneous biaxially stretched polyester film and a method for producing the same, and more particularly to a simultaneous biaxially stretched polyester film which has high strength in the longitudinal and transverse directions and is suitable for various industrial material films. .

[0002]

2. Description of the Related Art Plastic films enable continuous production of large-area films that cannot be obtained from other materials, and are characterized by their strength, durability, transparency, flexibility, and imparting surface characteristics. Utilizing it, it is used in fields that are in large demand, such as for agriculture, packaging, and building materials. Among them, biaxially stretched polyester films are used in various fields because of their excellent mechanical properties, thermal properties, electrical properties, and chemical resistance, and are particularly useful as base films for magnetic tape. Is unrivaled by other films. In recent years, the base film has been required to be thinner in order to reduce the weight and size of the equipment and to record for a long period of time, and accordingly, higher strength is desired.

In recent years, the tendency of thinning has been very strong in thermal transfer ribbons, capacitors, and heat-sensitive stencil printing papers in recent years, and similarly, higher strength is desired.

As a technique for increasing the strength of a biaxially stretched polyester film, a so-called re-longitudinal stretching method in which a film stretched in two longitudinal and transverse directions is stretched again in the longitudinal direction to increase the strength in the longitudinal direction is generally used. (For example, Japanese Patent Publication No. 42-9270)
JP, JP-B-43-3040, JP-A-46-1
119, JP-A-46-1120). Also,
In order to further impart strength in the horizontal direction, a re-longitudinal re-horizontal stretching method has been proposed in which the film is stretched again in the transverse direction and then stretched in the transverse direction again (for example, JP-A-50-133276, JP-A-55-22915).

[0005]

As a technique for obtaining a biaxially stretched polyester film having a high strength in the machine and transverse directions, there is the above-mentioned conventional re-mechanical re-horizontal stretching method. After increasing the strength in the vertical direction, and then re-horizontal stretching to increase the strength in the horizontal direction, there is a disadvantage that the orientation in the vertical direction decreases, and it is difficult to increase the strength in the vertical and horizontal directions at the same time. The frequency of film tearing increases.

An object of the present invention is to provide a simultaneously biaxially stretched polyester film having a large orientation in the vertical and horizontal directions and a high strength, and a method for producing the same.

[0007]

In order to solve the above-mentioned problems, a method for producing a simultaneously biaxially stretched polyester film of the present invention comprises the steps of: forming an unstretched cast film from (glass transition temperature of polyester Tg + 25) ° C. to (Tg + 45) A first stretching step of simultaneous biaxial stretching in the longitudinal and transverse directions at an area stretching magnification of 2 to 7 times in a temperature range of ° C, and subsequently (Tg-1
5) Area stretching ratio of 4 in the temperature range of ° C to (Tg + 10) ° C.
The method is characterized in that it has a second stretching step of simultaneously biaxially stretching in the vertical and horizontal directions at up to 20 times.

Further, the method for producing a simultaneously biaxially stretched polyester film according to the present invention is characterized in that the unstretched cast film is formed by (polyester glass transition temperature Tg + 25) ° C.
The first-stage stretching step of simultaneous biaxial stretching in the longitudinal and transverse directions at an area stretching ratio of 2 to 7 in the temperature range of (Tg + 45) ° C., and subsequently in the temperature range of (Tg−15) ° C. to (Tg + 10) ° C. And a second stretching step of simultaneously biaxially stretching in the longitudinal and transverse directions at an area stretching ratio of 4 to 16 times, and further in a temperature range of (melting temperature of polyester Tm-130) ° C to (Tm-10) ° C. The method comprises a third-stage stretching step of simultaneous biaxial stretching in the longitudinal and transverse directions at an area stretching ratio of 1.5 to 5 times.

Further, simultaneous biaxial oriented polyester film according to the present invention, after the simultaneous biaxial stretching, the peak intensity in the longitudinal direction of the peak intensity (I _MD) and thickness direction at 1615 cm ^-1 measured by laser Raman scattering method Ratio R to (I _ND )
The ratio R ₂ (= I _TD / ₁ ) between ₁ (= I _MD / I _ND ), the peak intensity in the lateral direction (I _TD ), and the peak intensity in the thickness direction (I _ND )
I _ND ) is at least one of 6 or more.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail together with preferred embodiments. The ratio R ₁ (= I _MD / I _ND ) between the peak intensity (I _MD ) in the longitudinal direction and the peak intensity (I _ND ) in the thickness direction at 1615 cm ⁻¹ measured by the laser Raman scattering method in the present invention, and the ratio in the horizontal direction. the ratio R of the peak intensity between (I _TD) and thickness direction of the peak intensity (I _ND)
2 (= I _TD / I _ND ) is an index indicating the strength of vertical or horizontal orientation, and is 1615 cm ⁻¹ used in the present invention.
Raman band of C = C stretching vibration of benzene ring (νC =
In the band belonging to C), the intensity of this band varies depending on the packing state of the benzene ring, and particularly in the case of a biaxially stretched film, it cannot be determined only by the orientation.

In the present invention, in order to obtain a film having a high orientation and a high strength, the strength ratios R ₁ , R
It is necessary that at least one of ₂ is 6 or more. Preferably it is 7 or more. In particular, for magnetic materials, it is more preferable that the lateral strength ratio R ₂ is 6 or more.

A commercially available biaxially stretched polyester film usually has a Young's modulus (E _MD ) in the machine direction and a Young's modulus (E _TD ) in the transverse direction of 4 to 4.5 GPa. For base films for
In order to achieve the objectives of high definition for ribbons and heat-sensitive stencil printing paper, and to improve insulation properties for capacitors, the Young's modulus in the vertical direction (E _MD ) and the Young's modulus in the horizontal direction (E _TD ) have been achieved. ) Is preferably at least 6 GPa. More preferably, it is more preferably 7 GPa or more. In this case, the Young's modulus in the direction in which the Young's modulus is less than 6 GPa is preferably 5 GPa or more.

The polyester in the present invention is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid. Dicarboxylic acids are represented by terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, etc.,
The diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. In particular,
For example, polymethylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-
1,4-cyclohexylene dimethylene terephthalate,
Polyethylene-2,6-naphthalate or the like can be used. Of course, these polyesters may be homopolymers or copolymers. Examples of copolymerization components include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, sebacic acid, and phthalic acid. And dicarboxylic acid components such as isophthalic acid and 2,6-naphthalenedicarboxylic acid. In the case of the present invention, at least one selected from polyethylene terephthalate, polypropylene terephthalate, polyethylene isophthalate, polyethylene naphthalate (polyethylene-2,6-naphthalate) and a copolymer thereof has mechanical strength and heat resistance. It is preferable from the viewpoints of properties, chemical resistance, durability and the like.

The polyester may contain inorganic particles, organic particles, and other various additives such as an antioxidant, an antistatic agent, and a crystal nucleating agent.

Specific examples of the inorganic particles include silicon oxide,
Oxides such as aluminum oxide, magnesium oxide, and titanium oxide; complex oxides such as kaolin, talc, and montmorillonite; carbonates such as calcium carbonate and barium carbonate; sulfates such as calcium sulfate and barium sulfate; barium titanate; Titanate such as potassium, phosphate such as tertiary calcium phosphate, dibasic calcium phosphate, and monocalcium phosphate can be used, but not limited thereto. These may be used in combination of two or more depending on the purpose.

Specific examples of the organic particles include polystyrene or crosslinked polystyrene particles, vinyl particles such as styrene / acrylic / acrylic crosslinked particles, styrene / methacrylic / methacrylic crosslinked particles, benzoguanamine / formaldehyde, silicone, and polytetrafluoroethylene. Although particles such as fluoroethylene can be used, the particles are not limited thereto, and any particles may be used as long as at least a part of the particles constituting the particles is organic polymer fine particles insoluble in polyester. The organic particles preferably have a spherical particle shape and a uniform particle size distribution from the viewpoint of smoothness and uniformity of formation of projections on the film surface.

The particle size, blending amount, shape and the like of these particles can be selected according to the application and purpose.
The average particle diameter is preferably 0.05 μm or more and 3 μm or less, and the blending amount is preferably 0.01% by weight or more and 10% by weight or less.

The film of the present invention may be a laminated film having two or more layers. The use of a laminated film having two or more layers is particularly suitable for a base film of a magnetic recording medium, as a method of designing the surface roughness of a film surface to be a magnetic recording surface and a surface roughness different from each other depending on the application. It is.

The film of the present invention is a simultaneously biaxially stretched polyester film, and the desired orientation of the film is imparted by the method of the present invention for simultaneous biaxially stretching.

The total thickness of the film in the present invention can be appropriately determined according to the application and purpose. Normally, the thickness is preferably 1 μm or more and 20 μm or less for magnetic materials, and especially 2 μm for coating magnetic recording media for digital video.
m or more and 8 μm or less, and 3 μm or more and 9 μm or less for vapor deposition type magnetic recording media for digital video.

Further, among industrial materials, the thickness is preferably 1 μm to 6 μm for thermal transfer ribbons, 0.5 μm to 15 μm for capacitors, and 0.5 μm to 5 μm for heat-sensitive stencil paper.

The film having an intensity ratio R by the laser Raman scattering method of the present invention of at least one of the longitudinal direction and the transverse direction of 6 or more is used for magnetic media, heat transfer ribbon, capacitor, heat-sensitive stencil printing paper, etc. Can be preferably used.

In the case of a magnetic medium application, the intensity ratio R by the laser Raman scattering method is 6 or more in at least one of the vertical direction and the horizontal direction, and particularly, the intensity ratio R _{2 in the} horizontal direction is 6 or more.
As described above, it is more preferable to be 7 or more.
Also preferably, the Young's modulus in the transverse direction of the film (E _TD )
Is 6 GPa or more, more preferably 7 GPa or more.
In this case, the longitudinal direction of the Young's modulus (E _MD) is more 5GPa is preferred.

In particular, for digital video applications among magnetic materials, the intensity ratio R in the laser Raman scattering method is used.
Of at least one of the vertical direction and the horizontal direction is not less than 6, and in order to achieve a high level of electromagnetic conversion characteristics, the surface roughness (Ra) of at least one side is as large as 0.1 nm to 5 nm. Preferably, the surface is smooth.

In order to achieve this object, it is preferable to form a laminated film of at least two layers, and to achieve this object with at least one surface layer.

In the case of a thermal transfer ribbon, at least the strength ratio R _{2 in the} longitudinal direction among the above-mentioned strength ratios R is more preferably 6 or more.
When the heat shrinkage rate per minute is 2% or less, further 1% or less,
High-definition printing can be performed without wrinkles at the time of printing, without causing printing unevenness and overtransfer of ink.

In the case of a capacitor application, at least the strength ratio R _{1 in the} longitudinal direction among the above-mentioned strength ratios R is 6 or more, and the breaking elongation in the longitudinal direction of the film is 100% or less,
More preferably, when it is 80% or less, it is effective for improving the dielectric breakdown voltage and stabilizing the dielectric characteristics.

In the case of heat-sensitive stencil paper, at least one of the strength ratio R in the longitudinal direction and the transverse direction is 6 or more, and the melting point of the film is 230 ° C. or less.
When the heat of crystal fusion (ΔHu) is 50 J / g or less, the piercing property at low energy is excellent, the piercing diameter can be changed according to the energy level, and color printing on multiple plates is performed. Excellent printability in some cases.

The simultaneous biaxially stretched film referred to in the present invention is:
This is a film in which the orientation is imparted by simultaneous biaxial stretching. According to the production method of the present invention, the unstretched cast film is formed by (polyester glass transition temperature Tg + 25) ° C.
The first stretching step of simultaneous biaxial stretching in the vertical and horizontal directions at an area stretching ratio of 2 to 7 times in the temperature range of (Tg + 45) ° C., followed by the temperature of (Tg−15) ° C. to (Tg + 10) ° C. It has a second-stage stretching step of simultaneous biaxial stretching in the vertical and horizontal directions at an area stretching ratio of 4 to 20 times within the range, and performs simultaneous biaxial stretching in multiple stages at multiple temperatures.

The longitudinal and transverse stretching ratios of the simultaneous biaxial stretching at each stage may be the same or different. Preferably, when the both ends of the cast film are guided to a simultaneous stretching tenter for gripping with a gripper (clip), and after preheating the film, the first and second stages are simultaneously stretched,
It is preferable that the vertical and horizontal stretching ratios are the same, or the difference between the vertical and horizontal stretching ratios is 1 or less.

The unstretched cast film is heated at (Tg + 25) ° C. to (Tg + 45) ° C.
A first stretching step of simultaneous biaxial stretching in the longitudinal and transverse directions to an area stretching ratio of 2 to 7 times in a temperature range of
-15) A second stretching step of simultaneously biaxially stretching in the machine and transverse directions at an area stretching ratio of 4 to 16 times in a temperature range of -15 ° C to (Tg + 10) ° C, and further (a melting temperature Tm of the polyester).
According to a production method having a third-stage stretching step of simultaneously biaxially stretching in the vertical and horizontal directions at an area stretching ratio of 1.5 to 5 times in a temperature range of −130) ° C. to (Tm−10) ° C. The film can be further strengthened. At this time, it is more preferable that the third-stage stretching step be performed simultaneously and biaxially in multiple stages at multiple temperatures. In this case, the longitudinal and transverse stretching ratios in the third-stage simultaneous biaxial stretching are appropriately selected according to the required strength characteristics of the final biaxially stretched film within the scope of the present invention. .

After simultaneous biaxial stretching, heat setting is performed in the temperature range of (polyester melting temperature Tm−60) ° C. to (Tm−10) ° C., and relaxation treatment in the longitudinal and horizontal directions is performed during the cooling process from the heat setting temperature. Is preferred in terms of thermal dimensional stability.
Here, the area stretch ratio is a product of the longitudinal stretch ratio and the transverse stretch ratio.

In the simultaneous biaxial stretching of the present invention, the temperature of the gripper (clip) at the end of the film is preferably in the temperature range of (glass transition temperature of polyester Tg + 15) ° C. to (Tg + 50) ° C. In the shape of the surface that comes into contact with the tool, it has a gripping part having a ratio (L _MD / L _TD ) of the length in the longitudinal direction (L _MD ) to the length in the width direction (L _TD ) in the range of 3 to 15. Simultaneous biaxial stretching using a clip is preferred from the viewpoint of increasing the stretching ratio of the film at the clip holding portion.

Here, the temperature of the gripper (clip) means that the gripper passes through the tenter while being heated by the hot air in the stretching and heat fixing zone, is discharged from the tenter, returns to the outer periphery of the oven, and is guided to the tenter inlet. At this time, it refers to the temperature of the gripper (clip) before gripping the edge of the film. The temperature of the gripper is controlled by controlling the amount of cold air for cooling and the length of the cooling unit in the step of returning to the outer periphery.
This temperature is set to a film forming condition and becomes a steady temperature in a continuous operation for 3 to 5 hours.

Further, the shape of the surface where the film end and the gripping tool come into contact with each other is such that the carbon paper is sandwiched between the papers,
Alternatively, it refers to a shape obtained when a pressure-sensitive film that develops color under pressure is sandwiched between grippers and subjected to pressure printing. In the present invention, the longitudinal length of the shape (L _MD) is, 15 to 30 m
m is preferred.

In the simultaneous biaxial stretching of the present invention, the temperature of the first stage is set to (the glass transition temperature Tg + 2 of the polyester).
5) The temperature range of ° C to (Tg + 45) ° C, and the second stage temperature is performed in the temperature range of (Tg-15) ° C to (Tg + 10) ° C, thereby improving the stretchability of the end portion of the film. In addition, there is an effect of increasing the strength of the central portion of the film after the simultaneous biaxial stretching of the second stage, and the simultaneous biaxial stretchability of the third and subsequent stages is improved, and the strength of the film after the simultaneous biaxial stretching is further increased. Can be enhanced.

In the present invention, the unstretched cast film refers to a sufficiently dried raw material pellet supplied to an extruder, extruded into a sheet on a rotating metal casting drum by means of a die such as a T-shape, and cooled and solidified. It refers to a crushed pellet or a pellet obtained by supplying undried pellets to a vented extruder.

Next, specific examples of the method for producing the biaxially stretched polyester film of the present invention will be described, but the present invention is not limited to such examples.

As a polyester, polyethylene terephthalate pellets were sufficiently dried under vacuum to
It is supplied to an extruder heated to a temperature of about 300 ° C. and extruded from a T-type die into a sheet. This melted sheet is
It is brought into close contact with a drum cooled to a surface temperature of 10 to 40 ° C. by electrostatic force and solidified by cooling to obtain a substantially amorphous unstretched cast film. This cast film is gripped by clips running on both ends of the film, guided to a simultaneous biaxial stretching tenter, heated to 100 to 120 ° C. in a preheating zone, and stretched vertically and horizontally at a magnification of 1.5 to 2.5 times. , The first-stage simultaneous biaxial stretching is performed in an area stretching ratio of 2 to 7 times. At this time, it is preferable that the temperature of the clip that grips the end of the film be in a temperature range of 90 to 130 ° C. Subsequently, the temperature was lowered to a temperature of 60 to 85 ° C., the vertical and horizontal stretching ratios were in the range of 2 to 5 times, and the area stretching ratio was 4
The second-stage simultaneous biaxial stretching is performed in a range of up to 20 times. Alternatively, the area stretching ratio of the second-stage simultaneous biaxial stretching is 4 to 1
The stretching is performed in a range of 6 times, and subsequently, in a temperature range of 125 to 245 ° C., preferably 130 to 210 ° C., a longitudinal and transverse stretching ratio is in a range of 1.0 to 2.5 times, and an area stretching ratio is 1.
The third-stage simultaneous biaxial stretching is performed in a range of 5 to 5 times. Third
It is preferable that the simultaneous biaxial stretching of the stage is performed in multiple stages at two or more stages of temperature. For example, 125-160 ° C
It is preferable from the viewpoint of strength development that the stretching ratio is divided in the temperature range of 161 to 245 ° C. and the simultaneous biaxial stretching is performed.

In order to impart flatness and dimensional stability to the film thus biaxially stretched, the film is heat-set at a temperature in the range of 195 to 245 ° C. The relaxation treatment is carried out in the vertical and horizontal directions in a temperature range of ° C., preferably in the range of 1 to 6%. After the treatment, the film was cooled to room temperature, wound up, and measured by a target laser Raman scattering method.
The ratio R ₁ (= I _MD / I _ND ) between the peak intensity in the vertical direction ( _IMD ) and the peak intensity in the thickness direction (I _ND ) at 5 cm ^−1, the peak intensity in the horizontal direction (I _TD ) and the thickness in the thickness direction A simultaneously biaxially stretched polyester film having a ratio R ₂ (= I _TD / I _ND ) to the peak intensity (I _ND ) of 6 or more is obtained.

In the present invention, before or after simultaneous biaxial stretching of the film, in order to impart surface properties of the film, for example, to impart easy adhesion, easy slipping, releasing property, and antistatic property. In the step, the surface of the polyester film can be coated with a coating material.

[Measurement and Evaluation Methods for Physical Properties] (1) Glass transition temperature Tg, melting temperature Tm, heat of crystal melting ΔHu As a differential scanning calorimeter, “Robot DSC-RDC220” manufactured by Seiko Instruments Inc. is used. As a data analysis device, the company's “Disk Session” SSC / 52
Using T.00, about 5 mg of a sample is collected, and Tg and Tm are determined from a heat curve obtained when the sample is heated from room temperature to 300 ° C. at a rate of temperature increase of 20 ° C./min. Further, the heat of crystal fusion ΔHu is determined from the area of the melting endothermic curve accompanying the melting.

(2) Orientation of Film by Laser Raman Scattering The measurement conditions of laser Raman spectroscopy are as follows. Apparatus: Ramanor U-1000 manufactured by Jobin Yvon Micro Raman: Measurement arrangement 180 ° scattering Sample stand Solid light source: Ar ⁺ laser, NEC GLG3300, wavelength 515 nm Spectrometer: Configuration 1 m Czerny-Turner type double monochromator diffraction grating 1800 g / mm, 110 × 110 mm Dispersion 9.23 cm ⁻¹ / mm Backlight removal rate 10 ⁻¹⁴ (20 cm ⁻¹ ) Detector: PM RCA31034, 943-02 manufactured by Hamamatsu Electronics The film used for measurement is embedded in polymethyl methacrylate. Thereafter, wet polishing was performed to make the cross section parallel to the lateral direction. The measurement part was the center part, the position was slightly shifted, and the measurement was performed ten times to obtain an average value. The measurement takes the intensity (I _MD ) of the 1615 cm ⁻¹ band in the polarization measurement parallel to the longitudinal direction and the intensity (I _ND ) of the 1615 cm ⁻¹ band in the polarization measurement parallel to the thickness direction, and sets the ratio R representing the orientation to R _1. = I _MD / _IND . 1615c in polarization measurement parallel to the horizontal direction
m ^-1 band intensity (I _TD) and the intensity of the 1615 cm ^-1 band in parallel polarization measurements in the thickness direction (I _ND) take,
The ratio R representing the orientation was R ₂ = _ITD / _IND .

(3) High-speed scraping property A film obtained by slitting a film into a tape having a width of 1/2 inch is run on guide pins (surface roughness: 100 nm in Ra) using a tape running tester ( Travel speed 25
0 m / min, running frequency 1 pass, winding angle: 60 °, running tension: 90 g). At this time, the guide pins after running the film were visually observed, and those with no white powder adhesion were excellent (○), those with some white powder adhesion good (△), and many white powders Those that were attached were judged to be defective (x). Although excellent is desirable, even good is practically usable.

(4) Young's modulus Using an automatic film strength and elongation measuring device “Tensilon AMF / RTA-100” manufactured by Orientec Co., Ltd., a sample film was prepared at a width of 10 mm, a test length of 100 mm, and a pulling speed of 200 mm / min. I pulled. The Young's modulus was determined from the slope of the rising tangent of the obtained tension-strain curve. Measurement is 2
The test was performed in an atmosphere of 5 ° C. and 65% RH.

(5) Breakage frequency Vacuum-dried polyethylene terephthalate is brought into close contact with the casting drum by electrostatic force from a T-type die and solidified by cooling to obtain a cast film, and a longitudinal stretching device comprising a plurality of rolls, or Observation of stretching by a tenter and tearing of the film due to stretching by a heat setting device was made and judged according to the following criteria. ◎: When there is no tear from the edge ○: When the tear from the edge occurs very rarely Δ: When the tear from the edge occurs occasionally ×: When the tear from the edge occurs frequently

(6) Electromagnetic conversion characteristics (C / N) A magnetic paint and a non-magnetic paint having the following compositions are applied on the surface of the film of the present invention by an extrusion coater. The thickness of the non-magnetic lower layer was appropriately changed), magnetically oriented, and dried. Next, after forming a back coat layer having the following composition on the opposite surface, a small test calender (steel / steel roll, 5 steps) was used to obtain a temperature of 85 ° C. and a linear pressure of 200 kg /.
After calendering at 60 ° C., cure at 60 ° C. for 48 hours. The raw tape was slit into a width of 8 mm to prepare a pancake. Next, a 200 m length of this pancake was incorporated into a cassette to form a cassette tape. This tape has a commercially available Hi8 VTR (S
7MHz using ONY EV-BS3000)
A +1 MHz C / N (carrier to noise ratio) measurement was performed.

(Composition of magnetic paint) ・ Ferromagnetic metal powder: 100 parts by weight ・ Na sulfonate-modified vinyl chloride copolymer: 10 parts by weight ・ Na sulfonate-modified polyurethane: 10 parts by weight ・ Polyisocyanate: 5 parts by weight ・Stearic acid: 1.5 parts by weight-Oleic acid: 1 part by weight-Carbon black: 1 part by weight-Alumina: 10 parts by weight-Methyl ethyl ketone: 75 parts by weight-Cyclohexanone: 75 parts by weight-Toluene: 75 parts by weight (nonmagnetic lower layer) Composition of paint) ・ Titanium oxide: 100 parts by weight ・ Carbon black: 10 parts by weight ・ Na sulfonate-modified vinyl chloride copolymer: 10 parts by weight ・ Na sulfonate-modified polyurethane: 10 parts by weight ・ Methyl ethyl ketone: 30 parts by weight ・ Methyl Isobutyl ketone: 30 parts by weight ・ Toluene: 30 layers Part (composition of back coat) ・ Carbon black (average particle diameter 20 nm): 95 parts by weight ・ Carbon black (average particle diameter 280 nm): 10 parts by weight ・ α-alumina: 0.1 part by weight ・ Zinc oxide: 0.3 part by weight Parts-Na sulfonate-modified polyurethane: 20 parts by weight-Na sulfonate-modified vinyl chloride copolymer: 30 parts by weight-Cyclohexanone: 200 parts by weight-Methyl ethyl ketone: 300 parts by weight-Toluene: 100 parts by weight

(7) Evaluation of print unevenness and gradation property A cyan, magenta, and yellow ink layer is applied to the obtained film to form a printer ribbon, and standard printing of a color pattern is performed using a variable dot thermal transfer color printer. Then, the gradation was visually evaluated. In addition, it was also visually determined whether or not the ribbon had wrinkles due to the uniformity of the printed portion.

(8) Evaluation of Characteristics for Capacitor Dielectric properties A test piece was prepared by depositing aluminum on both sides of a film in a circular shape having a diameter of 18 mm so as to have a thickness of 600 to 1000 angstroms.
Leave for 48 hours or more in an atmosphere of 0 ± 5 ° C. and 65 ± 5% relative humidity. A frequency of 1 kHz was measured using a dielectric property measuring device DEA-2970 manufactured by TA Instruments.
z, the temperature dependence of the dielectric loss tangent was measured at a heating rate of 2 ° C./min, and those having a dielectric loss tangent at 105 ° C. of 1.3% or less were accepted.

B. Dielectric breakdown voltage According to the method described in JIS-C-2319, except that
Using a film without metal deposition as a test piece, evaluation is made as follows. A rubber plate having a rubber shore hardness of about 60 degrees and a thickness of about 2 mm is laid on a metal plate of an appropriate size, and 10 aluminum foils of about 6 μm thickness are laid on the rubber plate as a lower electrode. The upper electrode is a brass cylinder having a weight of about 50 g, a round bottom of about 1 mm, a diameter of about 8 mm, a smooth bottom surface and no damage. The test piece is previously left in an atmosphere at a temperature of 20 ± 5 ° C. and a relative humidity of 65 ± 5% for 48 hours or more. A test piece is sandwiched between the upper electrode and the lower electrode, and a DC voltage is applied between both electrodes by a DC power supply in an atmosphere at a temperature of 20 ± 5 ° C. and a relative humidity of 65 ± 5%. At 0 V until the dielectric breakdown occurs. A test is performed on 50 samples, and an average value obtained by dividing the dielectric breakdown voltage by the thickness of the test piece is determined. A value of 400 V / μm or more is regarded as a pass.

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, more specific embodiments of the present invention will be described. Examples 1 and 2 and Comparative Examples 1 and 2 A pellet of polyethylene terephthalate (containing 0.1% by weight of spherical crosslinked polystyrene particles having an intrinsic viscosity of 0.65, a glass transition temperature of 75 ° C, a melting point of 255 ° C, and an average diameter of 0.3 µm) was prepared. After vacuum drying at 180 ° C. for 3 hours, the mixture was supplied to an extruder heated to 280 ° C., melt-extruded, and discharged from a T-die into a sheet. Further, this sheet was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and cooled and solidified to obtain an unstretched cast film. Both ends of the unstretched film are gripped with clips, guided to a simultaneous biaxial stretching tenter equipped with a drive device for driving the clips by a linear motor, preheated at a temperature of 110 ° C., and stretched as shown in Table 1. Then, the first-stage simultaneous biaxial stretching was performed, and then the second-stage simultaneous biaxial stretching was performed at a temperature of 80 ° C. and at the stretching ratio shown in Table 1, and then heated at a temperature of 210 ° C. After fixing, the film was subjected to a relaxation treatment in a cooling zone at 120 ° C. at a relaxation rate of 1.5% in the longitudinal direction and 2% in the lateral direction, and the film was gradually cooled to room temperature and wound up. The film thickness is adjusted to 9
It was adjusted to μm. The clip temperature at this time was 100 ° C. In the comparative example, the simultaneous biaxial stretching was performed at the stretching temperature shown in Table 1,
The procedure was performed in the same manner as in Example 1 except that the magnification was changed. When observing the clip grip trace of the film end, in Examples 1 and 2, a stretched trace of the film was seen, but in Comparative Examples 1 and 2, an unstretched portion of the grip trace was seen in the film, and from the film end. The film is broken. Table 1 shows the film production conditions (stretching temperature, magnification), and Table 2 shows the peak intensity ratio R, Young's modulus, and tear frequency of the obtained film obtained by the laser Raman scattering method.

[0053]

[Table 1]

[0054]

[Table 2]

Examples 3 and 4, Comparative Examples 3 and 4 Polyethylene terephthalate (containing 0.1% by weight of spherical crosslinked polystyrene particles having an intrinsic viscosity of 0.65, a glass transition temperature of 75 ° C., a melting point of 255 ° C. and an average diameter of 0.3 μm) After vacuum drying the pellets at 180 ° C. for 3 hours, the pellets were supplied to an extruder heated to 280 ° C., melt-extruded, and discharged from a T-die into a sheet. Further, this sheet was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and cooled and solidified to obtain an unstretched cast film. Both ends of the unstretched film are gripped by clips and guided to a simultaneous biaxial stretching tenter equipped with a drive device for driving the clips by a linear motor system, preheated at a temperature of 110 ° C., and stretched as shown in Table 3. , The first-stage simultaneous biaxial stretching was performed, and subsequently, the second-stage simultaneous biaxial stretching was performed at a temperature of 80 ° C. and a stretching ratio shown in Table 3. Subsequently, the third-stage simultaneous biaxial stretching was performed at a temperature of 160 ° C. and a stretching ratio shown in Table 3. After heat-setting at a temperature of 210 ° C., a vertical cooling in a cooling zone of 120 ° C.
% And a relaxation rate of 3% in the transverse direction, and the film was gradually cooled to room temperature and wound up. The film thickness was adjusted to 9 μm by adjusting the extrusion amount. The clip temperature at this time is 10
5 ° C. As a comparative example, the procedure was the same as in the example, except that the simultaneous biaxial stretching was performed at the stretching temperature and magnification shown in Table 3. When observing the gripping trace of the clip at the end of the film, Example 3,
In No. 4, the grip portion of the film is stretched to almost the stretching ratio in the vertical direction, and in Comparative Example 3, a portion of the grip portion of the film having a low stretch ratio is seen, and the film is torn from the edge of the film. In Comparative Example 4, the film was torn from the edge of the film, and could not be stretched. Table 3 shows the film production conditions (stretching temperature, magnification), and the peak intensity ratio R, Young's modulus, and the like of the obtained film obtained by the laser Raman scattering method.
Table 4 shows the breaking frequency.

Comparative Example 5 Pellets of polyethylene terephthalate (containing 0.1% by weight of spherical crosslinked polystyrene particles having an intrinsic viscosity of 0.65, a glass transition temperature of 75 ° C., a melting point of 255 ° C. and an average diameter of 0.3 μm) were mixed at 180 ° C. for 3 hours. After vacuum drying, it was supplied to an extruder heated to 280 ° C., melt-extruded, and discharged from a T-die into a sheet. Further, this sheet was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and cooled and solidified to obtain an unstretched cast film. The unstretched cast film is guided to a group of heated metal rolls, heated to a temperature of 90 ° C., stretched in the longitudinal direction at a stretch ratio of 3.1 times, and the longitudinally stretched film is guided to a tenter. , And heated to a temperature of 95 ° C. and stretched in the transverse direction at a stretch ratio of 3.3 times. The biaxially stretched film was guided to a group of heated metal rolls, heated to a temperature of 160 ° C., and stretched in the longitudinal direction again at a stretch ratio of 1.3 times. Guide this stretched film to a tenter, grip the film end with a clip,
The film was heated at a temperature of 200 ° C., stretched in a transverse direction at a magnification of 1.2 times, then heat-set at a temperature of 210 ° C., gradually cooled to room temperature, and wound. The film thickness is 9μm by adjusting the extrusion amount
I adjusted to. Table 4 shows the peak intensity ratio R, Young's modulus, and breaking frequency of the obtained film obtained by the laser Raman scattering method.

[0057]

[Table 3]

[0058]

[Table 4]

Example 5 Using two extruders A and B, polyethylene terephthalate I (having an intrinsic viscosity of 0.6) was heated to 280 ° C.
5. Glass transition temperature 75 ° C, melting point 255 ° C, average diameter 0.
Pellets of 2 μm spherical crosslinked polystyrene (blended with 0.2% by weight) were supplied after vacuum drying at 180 ° C. for 3 hours, and extruder B also heated to 280 ° C. was supplied with polyethylene terephthalate II (having an intrinsic viscosity of 0.65, A glass transition temperature of 75 ° C., a melting point of 255 ° C., and a pellet of 0.1% by weight of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm and 0.025% by weight of spherical crosslinked polystyrene particles having an average diameter of 0.45 μm) were mixed at 180 ° C. Supply after vacuum drying for hours, merge in T-die (lamination ratio I / II = 10/1), surface temperature 3
A simultaneous biaxially stretched film was produced in the same manner as in Example 4, except that the film was cooled and solidified by being brought into close contact with static electricity on a cast drum at 0 ° C. to obtain a laminated unstretched cast film, and the film thickness was adjusted to 5.5 μm. Obtained. Peak intensity ratio R, Young's modulus, obtained by laser Raman scattering method of the obtained film,
Table 5 shows the breaking frequency, the abrasion resistance of the polyethylene terephthalate II surface, and the electromagnetic conversion characteristics of the film obtained by coating the magnetic layer on the polyethylene terephthalate I surface. The film of the present invention was very suitable for a magnetic recording medium.

[0060]

[Table 5]

Example 6 A pellet of polyethylene terephthalate (intrinsic viscosity: 0.65, glass transition temperature: 75 ° C., melting point: 255 ° C., 0.2% by weight of aggregated silica particles having an average diameter of 0.3 μm) was mixed with 180 pellets.
After vacuum drying at 3 ° C. for 3 hours, the mixture was supplied to an extruder heated to 280 ° C., and discharged from a T-die into a sheet. Further, this sheet was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and cooled and solidified to obtain an unstretched cast film. Both ends of the unstretched film are gripped with clips, guided to a simultaneous biaxial stretching tenter, preheated at a temperature of 110 ° C., stretched twice in the machine direction and twice in the transverse direction, and stretched in an area of 4 times. The first stage is simultaneously biaxially stretched twice,
At a temperature of 0 ° C., the stretching ratio is set to 3 times in the machine direction and 3 times in the transverse direction, and the second-stage simultaneous biaxial stretching is performed at an area stretching ratio of 9 times. Is 1.3 times in the longitudinal direction and 1.2 times in the lateral direction, and the area stretching ratio is 1.5.
After the simultaneous biaxial stretching of the third stage by 6 times, heat setting is performed at a temperature of 230 ° C, and then a relaxation treatment is performed at a cooling zone of 150 ° C with a relaxation rate of 2% in the vertical direction and 3% in the horizontal direction. The film was gradually cooled to room temperature and wound up. The film thickness was adjusted to 4.5 μm by adjusting the extrusion amount. The clip temperature at this time was 105 ° C. The peak intensity ratio R, Young's modulus, heat shrinkage in the longitudinal direction (100 ° C. × 30 minutes,%), and color printing characteristics of the obtained film, which were obtained by the laser Raman scattering method, were evaluated. As shown in Table 6, it was very good for a thermal transfer ribbon.

[0062]

[Table 6]

Example 7 A pellet of polyethylene terephthalate (having an intrinsic viscosity of 0.65, a glass transition temperature of 75 ° C., a melting point of 255 ° C., and containing 0.1% by weight of calcium phosphate particles having an average diameter of 0.2 μm) was mixed with 1 pellet.
After vacuum drying at 80 ° C. for 3 hours, the mixture was supplied to an extruder heated to 280 ° C., and discharged from a T-die into a sheet. Further, this sheet was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and cooled and solidified to obtain an unstretched cast film. This unstretched film is treated with a film
m, and a simultaneous biaxially stretched film was obtained in the same manner as in Example 6, except that the heat setting temperature was 220 ° C. Table 7 shows the peak intensity ratio R, Young's modulus, elongation at break in the width and length directions, and capacitor characteristics of the obtained film obtained by the laser Raman scattering method. As can be seen from Table 7, it was very good for use in capacitors.

[0064]

[Table 7]

Example 8 Polyethylene terephthalate-polyethylene isophthalate copolymer (intrinsic viscosity 0.70, glass transition point 75
° C, melting point 225 ° C, copolymerization ratio 80/20, average diameter 0.3
pellets containing 0.2% by weight of agglomerated silica of 0.2 μm)
After pre-crystallization by vacuum drying at 0 ° C for 3 hours, 180 ° C
For 3 hours, and then supplied to an extruder heated to 270 ° C. and discharged from a T-die into a sheet. Further, this sheet was brought into close contact with a cooling drum having a surface temperature of 25 ° C. by electrostatic force and cooled and solidified to obtain an unstretched cast film. Both ends of this unstretched film are gripped with clips, guided to a simultaneous biaxial stretching tenter, and preheated at a temperature of 105 ° C., and the stretching ratio is twice in the machine direction and twice in the transverse direction.
The first stage is simultaneously biaxially stretched to an area stretching ratio of 4 times, and subsequently at a temperature of 75 ° C., the stretching ratio is 3 times in the longitudinal direction and 3 times in the horizontal direction.
After the simultaneous biaxial stretching of the second step at an area stretching ratio of 9 times, the stretching ratio was further increased at a temperature of 150 ° C. by 1.3 times in the longitudinal direction and 1.3 times in the horizontal direction. Stretch ratio 1.6
After the simultaneous biaxial stretching in the third stage at 9 times, the film was cooled to a temperature of 120 ° C., and the film was gradually cooled to room temperature and wound up. The film thickness was adjusted to 1.5 μm by adjusting the extrusion amount. The heat of crystal fusion ΔHu of the obtained film was 25 J / g.
The peak intensity ratio R and the Young's modulus according to the laser Raman scattering method are shown in Table 8. The weight of this film was 12 g / m ^2.
Base paper for heat-sensitive stencil bonded with Japanese paper. When a test pattern was printed by lithography (manufactured by Riso Kagaku Kogyo Co., Ltd.) using this base paper, excellent gradation and printing performance were obtained.

[0066]

[Table 8]

[0067]

According to the simultaneous biaxially stretched polyester film of the present invention and the method for producing the same, it is possible to stretch the film in a wide range of the area stretching ratio without causing the film to be stretched and torn. By increasing the strength ratio R of at least one of the longitudinal direction and the transverse direction at 1615 cm ^-1 measured by the laser Raman scattering method to 6 or more, high strength, abrasion resistance, dimensional stability, and elongation resistance are obtained. A film having excellent properties can be obtained and can be used in a wide range of applications, and particularly in magnetic recording media, good characteristics can be obtained.

Claims (15)

[Claims] 1. An unstretched cast film is prepared by a method of (glass transition temperature of polyester Tg + 25) ° C. to (Tg + 45)
A first stretching step of simultaneously biaxially stretching in the longitudinal and transverse directions at an area stretching ratio of 2 to 7 times in a temperature range of ° C, followed by (T
g-15) Simultaneous biaxial stretching characterized by having a second stretching step of simultaneous biaxial stretching in the longitudinal and transverse directions at an area stretching ratio of 4 to 20 in the temperature range of (Tg + 10) ° C. Manufacturing method of polyester film. 2. The method for producing a simultaneously biaxially stretched polyester film according to claim 1, wherein the stretching in each step is performed when the difference between the longitudinal stretching ratio and the transverse stretching ratio is 1 or less. 3. An unstretched cast film is prepared by heating (polyester glass transition temperature Tg + 25) ° C. to (Tg + 45)
A first stretching step of simultaneously biaxially stretching in the longitudinal and transverse directions at an area stretching ratio of 2 to 7 times in a temperature range of ° C, followed by (T
g-15) A second-stage stretching step of simultaneously biaxially stretching in the longitudinal and transverse directions at an area stretching ratio of 4 to 16 times in a temperature range of from 15 ° C. to (Tg + 10) ° C., and further (a melting temperature Tm-130 of the polyester). ) A simultaneous biaxial process comprising a third step of simultaneously performing biaxial stretching in the longitudinal and transverse directions at an area stretching ratio of 1.5 to 5 times in a temperature range of from ° C to (Tm-10) ° C. A method for producing a stretched polyester film. 4. The method for producing a simultaneously biaxially stretched polyester film according to claim 3, wherein the third stage stretching is performed in a temperature range of two or more stages. 5. After the simultaneous biaxial stretching, heat fixing is performed in a temperature range of (melting temperature of polyester Tm-60) ° C. to (Tm-10) ° C .; The method for producing a simultaneous biaxially stretched polyester film according to any one of claims 1 to 4, wherein a relaxation treatment is performed. 6. The temperature of the gripper at the film end is (glass transition temperature of polyester Tg + 15) ° C. to (Tg + 5).
0) It is in a temperature range of ° C.
The method for producing a simultaneous biaxially stretched polyester film according to any one of the above. 7. A surface of the film end and the gripper comes into contact shape, the ratio of the longitudinal length (L _MD) and the width direction length _{(L TD) (L MD /} L TD) is 3 The method for producing a simultaneously biaxially stretched polyester film according to any one of claims 1 to 6, wherein the polyester film is in a range of from 15 to 15. 8. The simultaneous biaxially stretched polyester film according to any one of claims 1 to 7, wherein the driving system of the gripper of the tenter that performs simultaneous biaxial stretching is a linear motor system. Production method. 9. 161 measured by a laser Raman scattering method
Ratio R ₁ (= I _MD / I _ND ) between the peak intensity in the vertical direction ( _IMD ) and the peak intensity in the thickness direction (I _ND ) at 5 cm ⁻¹ .
And at least one of the ratio R ₂ (= _ITD / _IND ) of the peak intensity in the lateral direction ( _ITD ) to the peak intensity in the thickness direction ( _IND ) is 6 or more. Biaxially stretched polyester film. 10. At least one of the vertical Young's modulus (E _MD ) and the horizontal Young's modulus (E _TD ) is 6 GPa.
The simultaneous biaxially stretched polyester film according to claim 9, wherein: 11. The simultaneous biaxial as claimed in claim 9, wherein the polyester is at least one selected from polyethylene terephthalate, polypropylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and a copolymer thereof. Stretched polyester film. 12. lateral Young's modulus (E _TD) is 6GPa
The simultaneous biaxially stretched polyester film according to any one of claims 9 to 11, which is for a magnetic recording medium. 13. The simultaneous biaxial stretching according to claim 9, wherein the thermal shrinkage in the longitudinal direction at 100 ° C. for 30 minutes is 2% or less, and is used for a thermal transfer ribbon. Polyester film. 14. The film has an elongation at break of 10 in the longitudinal direction.
The simultaneous biaxially stretched polyester film according to any one of claims 9 to 11, wherein the polyester film content is 0% or less and used for a capacitor. 15. The film has a heat of crystal fusion ΔHu of 50 J.
/ G or less, and for heat-sensitive stencil printing base paper, the biaxially stretched polyester film according to any one of claims 9 to 11.