KR100269665B1 - Polyester film and process for producing it - Google Patents

Abstract

A polyester film whose surface layer contains polyester A as a main component is disclosed. On the film surface, projections resulting from the crystallization of the polyester are formed. The polyester film of the present invention is composed of a biaxially oriented film containing polyester A as a main component, and the number of protrusions on at least one surface is 5 × 10 ³ / mm 2 or more, and is contained in the number of protrusions and the surface layer forming the surface. The value N _{R of the} number of protrusions / number of particles, which is a ratio to the number of particles, becomes 5 or more.

The polyester film manufacturing method of this invention heat-processes at least one surface of the unstretched film which has polyester A as a main component, accelerates crystallization of this heat-treated surface, and biaxially stretches the heat-treated unstretched film, and at least unstretched film The number of projections on one surface of is 5 × 10 ³ / mm2 or more, and the value of the number of projections / number of particles (N _R ), which is the ratio between the number of projections and the number of particles contained in the surface layer forming the surface, is 5 or more. And a process of forming protrusions on the surface of the corresponding biaxially stretched film.

All or most of the protrusions are formed by the crystallization of polyester A irrespective of the particles, thereby preventing the generation of voids and forming fine and uniform protrusions having excellent chipping resistance and scratch resistance.

Description

Polyester film and manufacturing method

The present invention relates to a polyester film and a method for producing the same, and more particularly, to a polyester film having a micro-projection formed on the surface of the film and a method for producing the same. Polyester films are widely used for various purposes. In order to increase the processing speed of the film, for example, to obtain a printing method for packaging film, a magnetic layer application method for a magnetic recording medium, a thermosensitive layer application method for a thermosensitive film, or to obtain a high-quality final product, surface characteristics such as runability and wear resistance There is a demand for a more excellent polyester film. It is known that it is effective to form micro projections on the film surface in order to obtain excellent running property.

From the viewpoint of forming such microprojections on the surface of the film, a polyester film containing spherical silica particles originating in colloidal silica is known (Japanese Patent Laid-Open No. 59-171623). Also known is a polyester film in which a thin layer containing particles is laminated on a basal layer to form surface projections (Japanese Patent Laid-Open No. 2-77431).

Conventional polyester films which form projections by containing particles (eg inert particles) on the film surface as described above, however, have the following problems basically.

The biggest problem in forming protrusions by containing particles is that the particles contained with respect to polyester are foreign matters, so that when the film is stretched, voids (cracks, cavities) are likely to occur around the particles.

Such voids cause various problems, for example, a decrease in transparency and a decrease in dielectric breakdown voltage in the use of capacitors. In addition, chipping is liable to occur because the protrusions formed on the surface of the film are soft in the base film for the magnetic recording medium. In particular, in the use of a magnetic tape, a film having a high elastic modulus and a draw ratio is required for the base film. Therefore, problems such as chipping on the film surface increase the generation of voids.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester film having a desired micro-projection formed on the surface of a film by crystallizing the polyester regardless of the particles contained therein, and a method of manufacturing the same. It is to provide a polyester film which is excellent and can prevent problems caused from voids. In order to achieve this object, the polyester film according to the present invention is composed of a biaxially oriented film containing polyester A as a main component, and the number of protrusions on at least one surface is 5 × 10 ³ / mm 2 or more, and the number of protrusions the surface ratio values of the projection number / number of particles and the particle number contained in the surface layer to form the is characterized in that (N _R) is not less than 5.

In the polyester film production method according to the present invention, at least one surface of an unoriented film containing polyester A as a main component is heat-treated, accelerated crystallization of the heat-treated surface, and biaxially stretched the heat-treated unoriented film to at least unstretched. The number of projections on one surface of the film is 5 × 10 ³ / mm 2 or more, and the value of the number of projections / particles (N _R ), which is the ratio between the number of projections and the number of particles contained in the surface layer forming the surface, is 5 or more. It consists of the process of forming a processus | protrusion on the surface of the biaxially stretched film corresponding to the thing.

In the present invention, the polyester film may be configured as a laminated polyester film. In other words, the laminated polyester film according to the present invention is composed of a B layer containing polyester B as a main component and an A layer of a bilayer oriented polyester film whose main component laminated on one side of at least B layer is polyester A. The number of protrusions formed on the surface of the layer A is 5 × 10 ³ / mm 2 or more, and the value of the number of protrusions / number of particles (N _R ), which is the ratio between the number of protrusions and the number of particles contained in the surface layer forming the surface, is 5. That's it.

Moreover, in the manufacturing method of the laminated polyester film which concerns on this invention, the unstretched laminated | multilayer film is formed by laminating | stacking A layer whose main component is polyester A on at least one surface of B layer whose main component is polyester B, and A of this film By heat-treating the surface of the layer to accelerate the crystallization of the surface and biaxial stretching, the number of protrusions on the surface of the A layer of the unstretched laminated film is 5 × 10 ³ / mm 2 or more, and the number of protrusions and the surface layer forming the surface It is comprised by the process of forming a processus | protrusion on the surface of the biaxially stretched film corresponding to the value ( _NR ) of protrusion number / particle number which is ratio with the number of particles contained is five or more.

In the polyester film and the laminated polyester film according to the present invention, most or all of the protrusions on the surface of the layer A, whose main component is polyester A, are the values of the number of protrusions / number of particles (N _{R being} a ratio with the number of particles contained in the surface layer). ) Is formed as crystallization of polyester A under conditions of 5 or more. In addition, a number of protrusions of a specific number or more, that is, 5 × 10 ³ holes / mm 2 is formed. Since the protrusions are not formed by the particles included in nature but as crystallization of polyester A, almost no void occurs. Therefore, firm and unbreakable protrusions are formed, and various problems caused by voids can be prevented.

Further, since the projections are formed as the crystallization of the polyester A, the desired fine and uniform projections can be easily formed as compared with the conventional method, that is, the method of containing the particles for the formation of the projections.

The following describes the present invention in more detail with examples and examples, but the present invention is not limited thereto. In the polyester film according to the present invention, the ratio N _R between the number of particles contained in the film surface layer and the number of protrusions formed on at least one side of the film is 5 or more.

The projections on the film surface are not formed by essentially containing particles, but rather as crystallization of the polyester A itself. Therefore, the problem of void generation due to the addition of particles is substantially eliminated and a solid protrusion can be formed. If the ratio N _R is less than 5, the protrusion ratio formed by containing the particles increases, and the desired wear resistance cannot be obtained because the ratio of the protrusions easily broken by the generated voids increases.

Therefore, most or all of the surface projections are formed by crystallization of polyester A and the number of projections is adjusted to be 5 × 10 ³ / mm 2. Therefore, a firm micro projection is formed uniformly on the surface of the film. As a result, a polyester film having abrasion resistance on its surface can be obtained.

The number of protrusions is preferably 5 × 10 ³ holes / mm 2 or more. If the number of protrusions is less than 5 × 10 ³ / mm 2, the coefficient of friction between films and between the film and the metal material (for example, metal pins) increases, and the increase of the coefficient of friction causes a decrease in handling and running. As long as N _R satisfies the above conditions, it is not necessary to form all the protrusions as protrusions formed by crystallization of polyester A. Some of the protrusions can be formed by containing particles or internally precipitated particles (particles generated from polyester). In order to obtain excellent abrasion resistance, the crystallization of the polyester, that is, the crystallization caused by the microcrystallization of the polyester, requires 70% or more, preferably 85% or more, of the protrusions present on the surface of the film. Since projections due to microcrystals of polyester do not generate voids, chipping resistance can be greatly improved by adjusting the ratio of projections within the above range. At the same time, if the ratio of the surface roughness parameters Rt, Rp and Rt / Rp of the film is 1.5 or more, the surface is hardly chipped and also functions to surround the chipped particles. Thus, for example, when such a film is used as a magnetic tape, the increase in dropout in which the tape repeatedly runs into the video deck can be suppressed. Further, in the polyester film according to the present invention, the area ratio of the protrusions present on the surface due to the crystallization of the polyester A is 5% or more, preferably 7% or more, more preferably 10% or more. By doing in this way, a protrusion of uniform height is formed, and running performance can be obtained with good chipping resistance. Moreover, it is preferable that ratio Rt / Ra of surface roughness Rt (maximum height) with respect to surface roughness Ra (center line average height) is 15.0 or less, Preferably it is 10.0 or less. If the ratio of Rt / Ra is more than the above-mentioned range, the height of the projections becomes uneven and the chipping resistance of the film surface is also likely to deteriorate.

Formation of protrusion by crystallization of polyester is performed as follows. When a biaxially oriented polyester film containing polyester as a main component is formed, the film is subjected to a heat treatment on at least one surface of the unstretched film and then biaxially stretched. By heat-treating the surface in the unstretched film step, desired protrusions are formed on the surface of the biaxially oriented polyester film. By heat-treating the surface in the unstretched film step, in particular, the crystallization of polyester A is accelerated and many microcrystals are produced. The unstretched film is biaxially stretched and biaxially oriented so that uniform fine protrusions are formed on the film surface due to the microcrystallization caused by the difference in hardness of the crystal portion and the hardness of the amorphous portion, and a film having a desired strength can be obtained.

In the polyester film which concerns on this invention, the kind of polyester A is not specifically limited. However, the crystallization parameter, ΔTcg, of polyester A is less than 70 ° C, preferably less than 65 ° C, and more preferably less than 60 ° C. Furthermore, a solution haze defined as haze measured when polyester A is dissolved in a solvent is preferably less than 10%. If the crystallization parameter (ΔTg) is 70 ° C. or more, it is difficult to obtain surface projections which are the objects of the present invention. In addition, the scratch resistance of the film surface is poor even if the surface projection is formed.

If the solution haze is 10% or more, the amount of particles formed in the polymer and / or the amount of particles added on the outer surface is too high. Therefore, it is difficult to obtain the desired surface properties in the present invention, and the chipping resistance of the surface is also poor. Polyester A is not particularly limited as long as the above conditions are satisfied, but as main components, ethylene terphthalate, ethylene α, β-bis (2-chlorophenoxy) ethane 4,4'-dicarboxylate and ethylene 2,6 It is preferable to contain 1 or more types of naphnateates. In particular, polyester whose main component is ethylene terephthalate is preferable. Within the scope of not impairing the object of the present invention, a copolymer polymer comprising a polyester of the present invention and two or more polyesters may be used.

In order to form a desired surface projection, crystallization of the surface of the film mainly composed of polyester A is accelerated by heat treatment before biaxial stretching.

As for the diameter of the sphericity present in the unstretched film before biaxial stretching of a polyester film, 0.03-0.45 micrometer is more preferable. By such adjustment, the surface of the biaxially stretched film is excellent in both the strength of the protrusion and the scratch resistance.

In the polyester film according to the present invention, a laminated film formed by laminating a biaxially oriented film containing polyester A as a main component on at least one surface of a film containing polyester A as a main component according to the present invention is used. Can be.

The laminated structure is not particularly limited. For example, a structure of layer A / B or layer A / B / A may be used. Another C layer can also be used. For example A / B / C, A / B / C / A, A / C / B / A or A / B / C / B / A can also be used. In addition, the B layer itself may be composed of a laminated film.

In the formation of such a laminated film, in order to form protrusions of uniform height and obtain excellent resistance, the thickness of the A layer is preferably 3 m or less, more preferably 1 m.

The kind of polyester B is not specifically limited, It is preferable that polyester B does not contain particle | grains, but may contain particle | grains. In the polyester film according to the present invention, the haze of the entire film is preferably 15% or less, more preferably 10% or less, and both cases are formed as a single layer film and a laminated film.

If the haze of the entire film is 15% or more, the nonuniformity of the film surface caused by the large haze becomes too large. Therefore, the wear resistance of the surface tends to deteriorate, and the electromagnetic conversion characteristics for the magnetic recording medium deteriorate.

In addition, when the polyester film is formed as a laminated film, most or all of the protrusions are formed on at least one surface of the A layer composed of the biaxially oriented film due to the crystallization of the polyester A.

At least 7%, preferably at least 85%, of the A layer surface projections are formed due to the crystallization of polyester A. The surface roughness parameter (Rt / Rp) of the surface of the layer A is 1.5 or more, and the area ratio of the protrusions is 5% or more, preferably 7% or more, and more preferably 10% or more. Rt / Ra on the surface of the A layer is 15.0 or less, preferably 10.0. Crystallization parameter (DELTA) Tcg of polyester A is 70 degrees C or less, More preferably, it is 65 degrees C or less, More preferably, it is 60 degrees C or less, and solution haze is 10% or less.

The spherical mean diameter of the unstretched film before biaxial stretching is preferably in the range of 0.03 to 0.45 µm, more preferably 0.10 to 0.30 µm.

Next will be described in detail a method for producing a polyester film according to the present invention.

In the manufacturing method by this invention, after heat-processing at least one surface of an unstretched film, this film is biaxially stretched. The term "unstretched film" herein refers to a film which is released from die through a weakly stretched film (up to about twice the draw ratio) on a single axis and immediately before cooling and coagulation treatment. The purpose of the heat treatment is to increase the desired degree of crystallization of the undrawn film surface.

As a method of heat treatment,

① Method to crystallize the film surface by slowly cooling high temperature film immediately after injection.

② Method to crystallize the film surface by cooling and solidifying the film and heating it again.

③ A method of crystallizing the film surface by heat-treating a weakly stretched film with a single axis can be used.

Although the method ② is preferable for forming the target surface in the present invention, desired surface formation can also be obtained under the appropriate conditions ① or ③. The method ② is not particularly limited, but a method of heat treatment under the condition that the film is placed on the roll, or a method of heating the film using an extruder may be used.

As the heat treatment condition, the temperature is preferably 100-250 ° C., and the treatment time is 0.5-150 seconds. In order to more effectively form the desired surface in the film forming process, more preferable conditions include a temperature of 140-250 ° C., a treatment time of 1-50 seconds, more preferably a temperature of 155-240 ° C., and a treatment time of 2-10 seconds.

As the polyester A according to the present invention, polyethylene terphthalate (PET) is preferably used. It is preferable that polyester A does not contain particle | grains, but may contain a small amount of particle | grains as needed. In order to obtain the advantages expected in the present invention, the number of protrusions formed on at least one surface of the film is 5 × 10 ² / mm ² or more, and the number of protrusions and the number of particles contained in the surface layer forming the surface and the ratio (N _R ) It should be at least five.

The containing particles are not particularly limited, but spherical silica particles, crosslinked organic particles, calcium carbonate particles, titanium dioxide particles, alumina particles or internal precipitated particles (particles formed in the polymer) may be used by nature due to colloidal silica.

In the polymerization of polyester A, acetate is preferably used as a metal compound in which antimony trioxide as a catalyst for polymerization is used as a catalyst for esterification for the purpose of enhancing the effect as a nucleating agent and reducing ΔTcg. do. However, not limited to the acetate salt, in order to achieve the object of the present invention, a magnesium compound is preferable. As the phosphorus compound added to the polymerization of PET, phosphate is preferred. However, the manufacturing method of polyester A is not limited to the method mentioned above.

Increasing the amount of catalyst added to increase the effect of nucleating agent is undesirable because too much particles are produced in the polymer and solution haze increases.

Polyester A is fed to a known injection molding machine and a molten polymer is obtained in the form of a sheet from a die having slits. The sheet is cooled and solidified in a casting roll to obtain an unoriented film.

In the case of a laminated polyester film, polyester A and polyester B are fed to different injection molding machines, respectively. That is, the lamination of polyester A and polyester B is performed by two or three injection molding machines, and a composite manifold or two or three layers of feed blocks (for example, a feed block having a rectangular laminated portion) is formed. The retaining die and a molten sheet of two to three layers are obtained from the die, and the sheet is cooled in a casting roll to form an unstretched film.

After the unstretched film is heat-treated by the above method, the film is biaxially oriented. In the case of a laminated polyester film, at least one surface of the unstretched film composed of polyester A is heat treated. That is, when the laminated structure is A / B, the surface of the layer A is heat treated. When the laminated structure is A / B / A, A / B / C / A, A / C / B / A or A / B / C / B / A, the surface of one A layer of both A layer surfaces is heat-treated.

When heat treating both surfaces, different desired characteristics can be obtained by heat treating each surface under different conditions. For example, one surface of layer A is adjusted to satisfy the number of protrusions and N _R , and the other surface of layer A is weakly suppressed from heat treatment to achieve a well described surface.

As the stretching method, a sequential biaxial stretching method and a simultaneous biaxial stretching method are used. Particularly in the sequential biaxial stretching method, the sequential biaxial stretching method in which the longitudinal stretching is first performed axially second and the longitudinal direction is 3.6-6.5 times effective is effective for forming the surface of the present invention. Longitudinal stretching is difficult to determine the specific temperature as the optimum temperature because it is optimal temperature and varies depending on the type of polyester or thermoplastic resin, and in order to obtain the desired surface formation in the present invention, the temperature is set to 70 to 130 ° C. effective. The stretching ratio in the longitudinal direction is preferably in the range of 5000 to 50000% / min.

The axial stretching usually uses an extruder. It is preferable to make axial stretching 3.0-5.0 times. The stretching ratio in the axial direction is preferably in the range of 1000 to 20000% / min, and the temperature of 80 to 160 ° C. The biaxially oriented film thus formed is heat treated. The heat treatment temperature is preferably 150 to 220 ° C, more preferably 170 to 210 ° C, and the heat treatment time is preferably 0.5 to 60 seconds.

The following describes a method for determining the nature of the invention and achieving its effect.

(1) Number of protrusions (surface protrusions) on film surface

Scanning of the flat surface of the film surface as 0 with a two-beam two-detector scanning electron microscope [ESM-3200, manufactured by Erionix Co., Ltd.] and a cross-section measuring device [PMS-1, manufactured by Erionix Co., Ltd.] The height data of the projections is sent to an image analysis device (EBAS-2000, manufactured by Carall Zeiss Co., Ltd.) to reconstruct the projection image on the film surface.

Next, the highest value of each of the projections obtained by binarizing the projections in this surface projection image is the height of the projections, and this is obtained for each projection. This measurement is repeated 500 times with different locations, and the number of protrusions having a height of 20 nm or more is measured and determined as the number of protrusions. The magnification of the scanning electron microscope is set in the range of 1000-8000 times. In some cases, a highly accurate optical interference three-dimensional surface analysis apparatus (manufactured by WYKO, TOPO-3D; The data obtained using the objective lens 40-200 times and the effective use of a high resolution camera] may be replaced with the data obtained using the SEM.

Also, to measure the projection in three dimensions, a method of bending the film at 82.5 °, photographing with an electron microscope of 10000-500000 magnification, and measuring the number of projections per 1 mm 2 from the average value measured at 500 fields may be used. have.

(2) the number of particles contained in the surface layer

In the present invention, the term "surface layer" means a portion located at a depth of 3D from the film surface, where "3D" means a value three times the average diameter (D) of the particles included in the film. The cross section of the film was observed with a transmission electron microscope (TEM), and the number of particles present in the portion of the 3D depth from the surface of the film was measured at a magnification of 3000-100000 at 500 fields, and from this measured data, the average number of particles per mm 2 was obtained. Is determined.

(3) the average diameter of the particles contained in the film

Plasma cryogenic ashing is performed to remove the polymer from the film to expose the particles. The ashing treatment conditions ensure that the particles are not damaged even if the polymer is ashed. The exposed particles are observed with a scanning electron microscope (SEM) and the particle images are processed with an image analyzer. The magnification of the SEM is approximately 2000-10000 times, and the field of view for one measurement is appropriately selected in the range of 10-50 µm on one side. It is measured by changing the measuring place, and it is measured by the following equation that the volume average diameter (d) of the particles in the diameter and volume ratio is 5000 or more.

d = ∑diNvi

(Where di is the diameter of the particle and Nvi is the volume ratio of the particle)

In the case where the particles are organic particles, the particles are greatly damaged by plasma low temperature ashing, so the following method is used. The cross section of the film was observed at 3000-100000 magnification using a transmission electron microscope (TEM). The thickness of the TEM measurement fragment is set to 1000 mm, and the measurement is made by visually changing the field of view to 500 or more fields, and the volume average diameter (d) of the particles is determined from the above equation.

(4) N _R value

The N _R value is defined as the ratio of the number measured in item 1 above to the number of locations measured in item 2 above.

(5) Measurement of substances forming protrusions

The projections formed on the film surface due to polyester microcrystals or other polyester particles are measured by the following method. Etch with an appropriate solvent in the thickness direction of the film to measure the projections just below the film. If an insoluble substance remains as a substance forming the projections, it is measured as the particles added in the apparently added particles or in the polymer (I). In addition, when an insoluble substance does not remain, it is measured as a microcrystal of polyester (II). As the solvent, for example, a mixed solvent such as a phenol / carbon tetrachloride (weight ratio = 6: 4) mixed solvent is suitable. In this method, the frequency of (I) and the frequency of (II) in 1 mm <2> of visual field are measured, and II / (I + II) is measured as protrusion ratio resulting from the crystallization of polyester A. FIG. However, the method for measuring the projections as crystallization of polyester A is not limited to the above, and other suitable methods may be used.

(6) Crystallization parameter: △ Tcg

Measurement was differential scanning calorimeter [DSC, type II; Made by Perkin Elmer Co., Ltd., and measurement conditions of DSC are as follows. A 10 mg sample is placed in the DSC, melted for 5 minutes at 300 ° C. and then rapidly cooled with liquid nitrogen. The cooled sample is heated at a rate of 10 ° C./min to know the glass transition temperature (Tg). The heating is continued, and the cooling crystallization temperature Tcc is determined as the crystallization fume peak temperature in the glass state. The difference (Tcc-Tg) between the cooling crystallization temperature (Tcc) and the glass transition temperature (Tg) is defined as the crystallization parameter (ΔTcg).

(7) solution haze of polymer

2 g of polyester is dissolved in 20 ml of a phenol / carbon tetrachloride (weight ratio: 6/4) mixed solvent, and solution haze is measured based on ASTM-D-1003-52. The optical path length in the measurement is 20 nm.

(8) mean diameter of Chinese New Year

Observe the cross section with a light microscope or electron microscope and repeat the measurement until the total spherical constant becomes 100. The mean value measured from the data is defined as the mean diameter of the sphere.

(9) the overall haze of the film

The overall haze of the film is measured based on ASTM-D-1003 using a haze meter.

(10) Rt / Rp and Rt / Ra values

The surface roughness of the film is measured by a surface roughness meter [ET-10, manufactured by Kosaka Kenkyu Sho Co., Ltd.].

Tip tip radius: 0.5㎛

Hand load: 5mg

Measuring length: 1mm

Cut off value: 0.08㎜

Ra is measured as follows. One portion of the measurement length L is separated from the roughness curve obtained by the surface roughness meter ET-1Q along the center line direction. Ra is determined by the following equation with the center line as the X axis and the axis perpendicular to the X axis as the Y axis.

Ra = (1 / L) ∫ _O ^L | f (x) | dx

Rt is expressed as the distance between the largest peak and the deepest valley at the measurement length (L). Rp is represented by the distance between the center line filling the peak in the measuring instrument L and the valley of the small curve drawn at the highest point of the curve. In the film obtained by the ultrathin method using a transmission electron microscope (H-600, manufactured by Hitachi Seisakusho Co., Ltd.), the cross section and the thickness of the laminated layer A were measured by the boundary line. The magnification for measurement depends on the thickness to be measured. Therefore, the magnification is not particularly limited, but usually 10000-100000 times is appropriate.

(12) void

High vision analyzers are used to measure voids. In the measurement, an image analyzer (PIAS-IV, manufactured by Fias Co., Ltd.) is used as the high-vision personal image analysis system, and "Metaplan" (manufactured by Reitz (Company)) is used as the optical microscope.

(A) preparation

One drop of liquefied paraffin is placed on the slide glass, a square film sample of 10 mm on one side is placed on the slide glass, and then one drop of liquefied paraffin is dropped. Then cover the glass with a film sample placed between the two glasses. Samples were prepared with liquefied paraffin equipment.

(B) Adjustment and measuring conditions

The objective lens of the optical microscope examines the sample at 32 times magnification and inputs the image into the high-vision monitor of the image analyzer. At this time, the magnification for measurement on the monitor is 1560 times. The condition is a black-white image, filtered with a GREEM filter, and the input phase is placed under the condition of binary values to switch brightness. At this time, the brightness indicating the degree of concentration is adjusted to 160, and the brightness of the optical microscope such as the aperture is adjusted to the average brightness measured under the condition that the sample does not become 154 as a blank value.

(c) measurement

The sum of each screen element of the void is measured by placing each void image under binarization conditions, and the sum is divided by the total screen elements of the field of view to obtain the area ratio of the void part, and the area ratio of the void part is measured by the following equation. It is expressed as the void index of. The total screen element per view is about 2,000,000 and the measurement area is 0.014 mm2. The measurement is repeated 10 times with different locations. The measured voids shall be 0.28 µm or more in diameter, measured by an equivalent circel.

Void index = [(sum of screen elements of void part) / (full screen element of measurement field)]

x 100 (%)

As a criterion for determining the degree of occurrence of voids, when the void index is 1% or less, the void is measured as "good", and when 1% or more, it is measured as "bad".

(13) Area ratio of protrusion

As with the measurement of the voids, a high vision analysis system is used.

(A) preparation

Precipitate aluminum on the film sample (the thickness of the precipitation layer: 500-800 mm 3) and transfer the sample to the slide glass.

(B) Adjustment and measuring conditions

The objective lens of the optical microscope inspects the sample at 80 times magnification and inputs the image into the high vision monitor of the image analyzer. At this time, the magnification for measurement on the monitor is 3900 times. The phase is filtered with a green filter under the conditions of black-white phase, and the input phase is placed under the condition of binary value to switch brightness. At this time, the brightness indicating the degree of concentration is set to 175. Prior to setting, the brightness of the optical microscope such as the aperture is adjusted to the average brightness measured under the condition that the sample does not become 154 as an official inspection. Objective side meter as reflecting mirror [reflective type; The mirror used by Nikon Corporation is used.

(C) measurement

The sum of each screen element of the projection is measured by placing each projection on the binarization condition. The sum is divided by the total screen elements of the field of view to obtain the area ratio of the projection, and the area ratio of the projection is measured by the following equation.

The total screen element per view is about 2,000,000 and the measurement area is 0.0064mm2, and the measurement is repeated 10 times by changing places.

The projections to be measured are equivalent circles, and the diameter of the projections should be 0.11 µm or more.

Area ratio of protrusion = [(sum of screen elements of protrusion) / (total surface element of measurement field)] x 100 (%)

(14) chipping resistance

The magnetic coating solution of the following composition was applied to the film surface by gravure roller to form a magnetic alignment layer and dried.

The film was calendered with a small test calendar machine (steel roll / nylon roll: 5-stage) at a pressure of 70 ° C. and 200 kg / cm, and then cured for 48 hours at 70 ° C. The obtained film was slit to a width of 1/2 inch and incorporated into the VTR cassette to produce a VTR cassette tape.

Composition of magnetic paint solution (unit: parts by weight)

Iron oxide containing Co [BET value: 50㎡ / g]: 100 parts

Etilek A [manufactured by Sekishu Chemical Co., Ltd., vinyl chloride / vinyl acetate copolymer]: 10 parts

Niporan 2034 [manufactured by Nippon Polyurethane Co., Ltd., polyurethane elastomer]: 10 parts

Coronate L [manufactured by Nippon Polyurethane Co., Ltd., polyisocyanate]: 5 parts

Lecithin: Part 1

Methyl ethyl ketone: 75 parts

Methyl isobutyl ketone: 75 parts

Toluene: 75 parts

Carbon Black: Part 2

Lauric acid: 1.5 parts

The video tape embedded in the 250m VTR cassette is supplied and rewound 100 times using a home video tape recorder.

Observe the amount of chipping powder that is attached to the pins in the cassette and the pins in the video tape recorder and the amount of chipping powder that is attached while driving the tape surface while driving the surface of the tape. Decide on

No chipping powder attached. : "Great"

· There is a small amount, but it is not a problem when using video tape. : "Good"

Impossible for use of video tape due to large amount of powder: "bad"

(15) scratch resistance

The scratch test is carried out using a continuous load type scratch resistance tester [HEIDON-18, manufactured by Shintokagaku Co., Ltd.]. The depth of scratches generated in this test is measured with a non-contact illuminometer (TOPO-3D, manufactured by WYKO).

Measuring conditions

Scratch Needle: Consist of Sapphire

Tip radius: 100㎛

Load: 0.-100g / 100mm

Travel Speed: 10m / min

Dimension

Scratch depth,

0.5㎛ or less: "excellent"

0.5 µm or more and 1.5 µm or less: "good"

1.5㎛ or more: "bad"

(16) Runability (friction coefficient μk)

The film was slit to 1/2 inch in width and the film was set in a tape running tester [SFT-700, manufactured by Yokohama Systems Genku-Usho Co., Ltd.]. Let's do it.

The initial friction coefficient (μk) is determined by the following equation.

μk = (2 / π) x In (T ₂ / T ₁ )

(T ₁ is the entrance tension, T ₂ is the exit tension, the guide pin diameter is 6mm, the material is sus27 (surface roughness 0.2S), the winding angle is 90 °, the running speed is 3.3 cm / sec.)

A frictional coefficient of less than 0.3 is said to be good. A μk of 0.3 or more is referred to as "bad". A coefficient of friction (μk) of 0.3 is a criterion for determining whether the handleability is good when the film is processed into a magnetic recording medium, a capacitor, or a package.

Examples and Comparative Examples

Next, a preferable Example is demonstrated with a comparative example.

The results are shown in Table 1 and Table 2.

EXAMPLE

Polyethylene terphthalate polymerized by a conventional method (0.10% by weight of magnesium acetate, 0.03% by weight of antimony trioxide, and 0.35% by weight of dimethylphenylphosphonate as a phosphorus compound) was used as polyester A (high viscosity: 0.60, melting point: 258). ℃, ΔTcg: 51 ℃, solution haze: 0.8%).

A polyethylene terphthalate polymerized by a conventional method using 0.06% by weight of magnesium acetate, 0.026% by weight of antimony trioxide and 0.026% by weight of trimethyl phosphate was prepared as Polyester B (high viscosity: 0.62, melting point 259 ° C, ΔTcg: 84 ° C). do.

External particles are not particularly added to polyester A and polyester B.

Example 1-3

Polyester A alone forms a single layer film.

The pellets of polyester A are dried at 180 ° C. for 3 hours, then fed to an injection molding machine and melted at 290 ° C. for injection molding. An injection molded polymer is obtained from a die in the form of a sheet, and the sheet is cast in a casting drum having a surface temperature of 30 ° C., and then cooled and solidified using an electrostatic application method to form an unstretched film.

The surface of this unstretched film that is not in contact with the casting drum is heat treated with a spinning heater. Heat treatment conditions are as follows.

Example 1: 20 seconds at 150 ° C

Example 2: 10 seconds at 180 ° C

Example 3: 3 seconds at 210 ° C

The heat-treated film is stretched 34 times at 90 ° C in the longitudinal direction. Then, the film is stretched at a rate of 2000% and 3.5 times at 95 ° C. in an axial direction using an extruder, and heat treated at 210 ° C. for 5 seconds to produce a biaxially oriented film having a thickness of 15 μm.

Under any heat treatment condition, a film having excellent surface properties of a film obtained within a specific range in the present invention can be obtained.

Example 4

A very small amount of inert particles is added to the polyester A described above. As inert particles, crosslinked polystyrene particles having an average diameter of 0.45 mu m are blended with polyester A in a water slurry state using a vent type twin screw extruder.

The concentration of the inert particles is 0.05% by weight. Using the pellet thus prepared, under the same heat treatment conditions as in Example 2, a biaxially oriented film having a thickness of 15 µm was obtained in the same manner as in Example 2.

Compared with the results of Examples 1-3, N _R is slightly small, and the projection ratio due to the crystallization of polyester A is also slightly reduced, but the data of these properties are within the specific range of the present invention and the film properties are also satisfactory.

[Examples 5 and 6]

Polyester A used in Examples 1-3 and Polyester B were used to form a film having a laminated structure A / B / A.

Pellets of polyester A and polyester B are each fed to two injection molding machines and melted at 290 ° C. Each of these molten polymers is laminated in three layers in a feed block. The lamination thickness of the A layer is controlled in the biaxially oriented film step by using a gear pump having a thickness of 1 μm of the A layer to control the amount of the polymer of the polyester A. A biaxially oriented laminated film having a total thickness of 15 μm was obtained in a similar manner to Example 1. The heat treatment conditions performed in the unstretched film stage are as follows.

Example 5: 10 seconds at 180 ° C

Example 6: 3 seconds at 210 ° C

Example 7

In the same manner as in Example 5, a biaxially oriented laminated film having a total thickness of 15 µm was obtained, and the thickness of one A layer was 3 µm.

Example 8

A biaxially oriented laminated film having a total thickness of 15 μm and a laminated account A / B / A was obtained in the same manner as in Example 5. The thickness of one A layer is 0.6 micrometer.

In this example, a small amount of inert particles (particle content: 0.1% by weight, colloidal silica particles having an average diameter of 0.3 μm were dispersed in ethylene glycol, which was added to polyester B during the polymerization process) Example 1- Polyester A and Polyester B used in 3 are used. Since the particles added to the base layer (B) layer do not have a great influence on the surface properties of the layer A, the film properties obtained are satisfactory.

Example 9

In the same manner as in Example 5, a biaxially oriented laminated film having an overall thickness of 15 µm and a laminated structure of A / B / A was obtained. In this example, polyester B used in Examples 5-7 is used, and the amount of magnesium acetate is 0.20% by weight and the amount of dimethylphenylphosphonate as compared to polyester A used in Examples 1-3. Polyethylene terphthalate polymerized by changing to 0.69% by weight is prepared as polyester A. (△ Tcg: 45 ℃ Solution Haze: 1.2%)

Example 10

In the same manner as in Example 5, a biaxially oriented laminated film having a total thickness of 15 µm and a laminated structure of A / B / A was obtained. In this example, polyester A used in Example 9 was used, and polyethylene terphthalate polymerized by changing the amount of magnesium acetate to 087% by weight of trimethylphosphate was prepared as polyester B. (△ Tcg: 73 ℃)

Although the projections attributable to the crystallization of polyester A are also slightly reduced, the data of these properties are within the specific scope of the present invention and the film properties are also satisfactory.

[Examples 11 and 12]

Polyester A used in Examples 1-3 and Polyester B used in Examples 5-7 are used to form a film having a straight layer A / B.

Pellets of polyester A and polyester B are each fed to two injection molding machines and melted at 290 ° C. Each of these molten polymers is laminated in two layers in the feed block. The lamination thickness of the A layer is controlled in the biaxially oriented film step by using a gear pump having a thickness of 0.5 μm of the A layer to adjust the polymer amount of the polyester A. A biaxially oriented laminated film having a total thickness of 15 μm was obtained in a similar manner to Example 1. Heat treatment of the surface of the layer A made of polyester A and performed in the unstretched film step is as follows.

Example 11: 7 seconds at 190 ° C

Example 12: 3 seconds at 210 ° C

Example 13

In the same manner as in Example 13, a biaxially oriented laminated film having a total thickness of 15 µm and a laminated structure of A / B was obtained. In this example, polyester A used in Example 4 and polyester B used in Example 10 are used. In the step of the biaxially oriented film, the thickness of one A layer is adjusted to 1.0 mu m.

Example 14

In the same manner as in Example 11, a biaxially oriented laminated film having a total thickness of 15 µm and a laminated structure of A / B was obtained. In this example, polyester A used in Example 9 and polyester B used in Example 8 are used. In the step of the biaxially oriented film, the thickness of one A layer is adjusted to 1.0 mu m.

Comparative Example 1-3

Polyester A used in Example 1 was used to obtain a biaxially oriented single layer film having a total thickness of 15 μm in the same manner as in Example 1. However, the heat treatment conditions performed in the unstretched film stage are changed as follows.

Comparative Example 1: 300 seconds at 150 ° C

Note 2: 600 seconds at 100 ° C

Comparative Example 3: Not Heat Treated

Since the obtained surface characteristics deviate from the specific range of this invention, the characteristic of the obtained film is also bad.

[Comparative Example 4]

Using only polyester B used in Example 5, the same procedure as in Example 1 and the same heat treatment conditions were carried out to obtain a biaxially oriented single layer film having a total thickness of 15 μm.

Since ΔTcg is large and crystallization by heat treatment is also insufficient, the obtained film has very poor characteristics.

[Comparative Example 5]

Using a pellet prepared by adding colloidal silica particles to polyester A used in Example 1, a biaxially oriented single layer film having a total thickness of 15 µm was obtained in the same manner as in Example 1 (particle content: 1.0 wt%). Due to the large ratio of the projections due to the particles in the projections, the resulting film has voids and poor chipping resistance.

Comparative Example 6

In this comparative example, the polyester B used in Example 10 was used as polyester A, and the polyester B used in Example 5 was used as polyester B, and the same procedure as in Example 5 and the same heat treatment conditions were carried out. A biaxially oriented laminated film having a thickness of 15 μm and a laminated structure of A / B / A is obtained. Since ΔTcg of the surface layer is large and crystallization by heat treatment is insufficient, the number of protrusions due to crystallization is small and the characteristics of the obtained film are also poor.

Comparative Example 7

Polyethylene terphthalate (polymerization catalyst: 0.09% by weight of calcium acetate, 0.17% by weight of lithium acetate, 0.045% by weight of antimony trioxide and 0.12% by weight of trimethyl phosphate) polymerized by the conventional method is polyester A (melting point: 260 DEG C, ΔTcg: 58). C, solution haze: 23%).

The polyester used in Example 5 is used.

A biaxially oriented laminated film having a total thickness of 15 μm and a laminated structure of A / B / A was obtained by the same method and the same heat treatment conditions as in Comparative Example 6. Because of too many internal precipitated particles generated in the polymer, the surface projections are uneven and the properties of the film obtained are also poor.

TABLE 1

TABLE 2

While some preferred embodiments and examples of the present invention have been described in detail above, those skilled in the art will appreciate that various modifications and changes can be made to the concept of the invention defined by the claims without departing substantially from the novel teachings and advantages of the present invention. It should be understood to be included.

Claims (19)

In a biaxially oriented polyester film containing polyester A as a main component, microcrystalline protrusions are formed on at least one surface by crystallization of polyester A, and the number of protrusions is 5 × 10 ³ / mm 2 or more, and the protrusions A polyester film, characterized in that the value (N _R ) of the number of protrusions / number of particles, which is the ratio between the number and the number of particles contained in the surface layer forming the surface thereof, is 5 or more. The polyester film according to claim 1, wherein at least 70% of the surface protrusions are protrusions caused by microcrystals of polyester A. The polyester film according to claim 1, wherein the surface roughness parameter, the ratio of Rt, Rp, and Rt / Rp are at least 1.5 on at least one surface. The polyester film according to claim 1, wherein the crystallization parameter of the polyester A, ΔTcg, is 70 ° C or less. The polyester film according to claim 1, wherein the solution haze of the polyester is 10% or less. The polyester film according to claim 1, wherein the average diameter of spherical grains existing in the unstretched film before biaxial stretching of said polyester film is 0.03-0.45 mu m. The polyester film according to claim 1, wherein the total haze of the polyester film is less than 15%. The polyester film according to claim 8, wherein the total haze of the polyester film is less than 10%. Heat treatment is performed on at least one surface of the unstretched film containing polyester A as a main component to accelerate the crystallization of the surface, and then a protrusion is formed on the surface of the biaxially stretched film corresponding to the surface of the unstretched film, wherein that projection number that is 5 × 10 ³ number / and ㎟ above, the projection number and the surface of the value of the ratio projections number / particle number of the particle number contained in the surface layer to form an (N _R) at least five non-drawn A method for producing a polyester film comprising biaxially stretching a new film. It consists of the film which laminated | stacked at least one surface of the layer B which consists of a film which has polyester B as a main component, and the biaxially-oriented film which has polyester A as a main component, and crystallizes polyester A on the surface of the said A layer. By means of which microcrystalline projections are formed, the number of projections formed on the surface of the A layer is 5 × 10 ³ / mm 2 or more, and the number of projections is a ratio between the number of projections and the number of particles contained in the surface layer forming the surface. Laminated polyester film, characterized in that the number of particles (N _R ) is 5 or more. The laminated polyester film according to claim 10, wherein the layer A has a thickness of 3 µm or more. 11. The laminated polyester film according to claim 10, wherein the laminated polyester film is a projection due to microcrystals of polyester A of 70% or more of the surface projections. The laminated polyester film according to claim 10, wherein the surface roughness parameters Rt, Rp, Rt / Rp are at least 1.5 on the surface of the layer A. The laminated polyester film according to claim 10, wherein the crystallization parameter ΔTcg of the polyester A is 70 ° C or less. The laminated polyester film according to claim 10, wherein the solution haze of the polyester A is 10% or less. The laminated polyester film according to claim 10, wherein the diameter of the spherical spheres present in said unstretched film before biaxial stretching of said layer A is 0.03-0.45 mu m. The laminated polyester film according to claim 10, wherein the total haze of the laminated polyester film is less than 15%. 18. The laminated polyester film according to claim 17, wherein the total haze of the laminated polyester is less than 10%. A layer containing polyester A as a main component is laminated on at least one surface of layer B containing polyester B as a main component to form an unstretched film, and the surface of layer A of the unstretched film is subjected to heat treatment to crystallize the surface. To form a projection on the surface of the biaxially stretched film corresponding to the surface of the unstretched film, and the number of protrusions is 5 × 10 ³ / mm 2 or more, and the number of protrusions and the surface is formed. And biaxially stretching the unburned film so that the value of the number of projections / number of particles (N _R ), which is a ratio with the number of particles contained in the surface layer, is 5 or more.