JP2001062912A - Biaxially oriented polyester film and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film having good coating performance and slitting characteristics. SOLUTION: The biaxially oriented polyester film has a number of localized electric charges of 5 pcs/m2 or less, preferably 1 pc/m2 or less. Roughness of at least one of the sides of the film is 0. 02-1 μm in center line average roughness (Ra). The biaxially oriented polyester film can be wound up in such an atmosphere that the relative humidity is in the range of 30-95%, while the film is being destaticized by a destaticizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film having excellent coating properties and slit properties, and a method for producing the same.

[0002]

2. Description of the Related Art
Biaxially oriented polyester films are used as industrial base films for thermal transfer, thermal stencils, capacitors and the like. In these applications, the film becomes a target product through various processes such as ink application, metal vapor deposition, or laminating. However, the presence of static electricity in the base film causes many problems. For example, a biaxially oriented polyester film for thermal transfer usually has a heat-meltable or sublimable ink layer on one side and a heat-resistant layer on the other side. This causes problems such as generation of coating defects such as unevenness and repelling at the time of coating and drying, deterioration of the running property of the film, and occurrence of winding deviation and wrinkles. In addition, a biaxially oriented polyester film for heat-sensitive stencil usually has an adhesive layer on one side and is bonded to paper, and an easy-slip layer is provided on the other side. This causes problems such as generation of coating defects such as unevenness and repelling at the time of drying and drying, and generation of adhesion failure in bonding with paper. Depending on the application, a biaxially oriented polyester film for a capacitor may be provided with a metal deposition layer or dielectric layer on one or both sides, or rolled up with a metal foil or other film. This causes a problem of worsening the winding and causing wrinkles and wrinkles.

The present invention has been made in view of the above-mentioned conventional problems, and a first object of the present invention is to provide a biaxially oriented polyester film having excellent ink coating properties and slit properties. The second object is to provide a manufacturing method thereof. In addition, "excellent slitting property" means that the cut surface is uniform when slitting (cutting) to a width suitable for the intended use while unwinding the wound film raw material and winding it again. Sometimes it means that the film can be rolled up neatly without slippage.

[0004]

Means for Solving the Problems The present inventor has made intensive studies in view of the above-mentioned problems, and as a result, has found that a film having a certain value with respect to certain physical properties can overcome the problems and is useful as an industrial base film. The inventors have found and completed the present invention.

[0005] In order to achieve the first object, a first aspect is provided.
The biaxially oriented polyester film of the invention described in (1) is characterized in that the charge localized on the surface is 5 / m ² or less. In the invention described in claim 2, in the invention described in claim 1, the electric charge localized on the surface is 1 / m ² or less.

According to a third aspect of the invention, in the first or second aspect of the invention, the polyester film has a center line average roughness (R
In a), it is 0.02 to 1 μm.

In order to achieve the second object, according to the present invention, an amorphous polyester obtained by extruding a molten polyester resin from a die into a sheet, bringing the molten polyester resin into close contact with a casting drum and solidifying by cooling. Is stretched in the machine direction and the transverse direction at a predetermined magnification, and after the stretching, heat treatment is performed at a temperature higher than the temperature at the time of stretching. It is characterized in that it is wound up while being neutralized by using.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The polyester referred to in the present invention is terephthalic acid, 2,6
-An aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof and a polyester obtained using ethylene glycol as a main starting material, but may contain other components. In this case, as the dicarboxylic acid component, terephthalic acid, phthalic acid, isophthalic acid, 2,
One or more of oxycarboxylic acids such as 6-naphthalenedicarboxylic acid and its isomers, adipic acid, sebacic acid and p-oxyethoxybenzoic acid can be used. As the glycol component, one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be used. In any case, in the polyester of the present invention, 80 mol% or more of the repeating structural units are ethylene terephthalate units or ethylene-2,6.
-Refers to polyesters having naphthalate units.

Further, the polyester film of the present invention comprises:
The polyester film is a polyester film oriented in both the vertical and horizontal directions using such a polyester as a starting material. The number of localized charges measured by the method described below is 5 / m ² or less, preferably 1 / m ² or less.
Pieces / m ² or less. This value is 5 pieces / m ²
When it is used as a base film for heat-sensitive transfer or heat-sensitive stencil, coating defects such as unevenness and repelling may occur during application and drying of the ink layer, heat-resistant layer, adhesive layer or slippery layer. This causes a problem that the application is not performed or bonding failure with paper occurs. In addition, when used as a base film for thermal transfer, thermal stencil printing, or condenser, the film becomes partially sticky during transport and winding, which causes a problem of winding deviation and wrinkling. Is generated.

In order to reduce the number of localized charges to 5 / m ² or less, in the winding step of the polyester film,
At room temperature, the relative humidity near the film is preferably 30 to 95%. More preferably, the relative humidity at both ends in the width direction of the film being wound is preferably 50 to 95%.
If the relative humidity is lower than 30%, static electricity is likely to be generated due to friction between the films during winding, which is not preferable. If the relative humidity exceeds 95%, blocking tends to occur between the films being wound, which is problematic. In addition, it is preferable that the charge be removed using an AC or DC charge removal device as needed.

It is preferable that at least one surface has a surface roughness of 0.02 to 1 μm in center line average roughness (Ra). If Ra is less than 0.02 μm, the slipperiness deteriorates, and static electricity is generated due to friction between the films during winding, wrinkles are formed in the films, and troubles in processing occur, which are not preferable. When Ra is more than 1 μm, in the case of heat-sensitive transfer or heat-sensitive stencil, the print lacks sharpness,
This causes a reduction in sensitivity and causes wear of the thermal head, which is a practical problem. In the case of a capacitor, the adhesion between layers is reduced and the capacity is reduced, which is a practical problem.

One of the methods for obtaining a film having such a surface roughness is to use a metal compound dissolved in the reaction system at the time of polyester production, for example, a phosphorus compound or the like in the metal compound dissolved in the system after the transesterification reaction. There is a so-called precipitated particle method in which fine particles are precipitated by acting. However, since this method has a limit in the amount of precipitated particles, another so-called additive particle method is preferably used.

The additive particle method is a method in which inert fine particles are blended into polyester in any of the steps from the polyester production step to the extrusion step before film formation. Examples of the inert particles include kaolin, talc, and the like. Magnesium carbonate, calcium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, lithium fluoride, and Ca, Ba, Z
Examples thereof include one or more metal compounds selected from terephthalates such as n and Mn, carbon black, and the like, but are not limited thereto. The shape of the inert fine particles may be spherical, massive, or flat, and the hardness, specific gravity, color, and the like are not particularly limited. Further, the average particle diameter of the inert fine particles is usually 0.1 to 10 μm, preferably 0.3 μm in equivalent sphere diameter.
３3 μm. The compounding amount of the film is 0.01 to 5% by weight, preferably 0.05 to 5% by weight.
To 3% by weight, more preferably 0.05 to 2% by weight.

Various resins and lubricants may be applied for the same purpose, composite of a roughened film, promotion of crystallization of the film after melt extrusion, sand matting, chemical treatment, coating matting For example, a known method can be appropriately applied.

The thickness of the film of the present invention is not particularly limited, but may be 10 μm for thermal transfer, thermal stencil, capacitor and the like.
The effect of the present invention is particularly remarkable for a thin film of m or less.

Next, the method for producing the polyester film of the present invention will be specifically described, but it is not limited to the following production examples. First, a polyester chip is dried, melted, extruded into a sheet form from a slit die, and cooled and solidified by a casting drum cooled to 30 to 50 ° C. while being adhered by an electrostatic adhesion method to form an unstretched sheet. The sheet is stretched at a high magnification in the machine direction at a high temperature in a high-magnification direction, that is, heated to 80 to 130 ° C. in one or two or more sections.
After stretching to 5 times, 90-130 ° C, 4.0.
The film is horizontally stretched at a magnification of up to 6.0 times and then heat-treated at 100 to 250 ° C to obtain a biaxially oriented polyester film. If necessary, the stretching temperature is 95 to 1 after the above-mentioned transverse stretching.
After re-longitudinal stretching at 20 ° C. and a stretching ratio of 1.01 to 2.5 times, heat treatment is carried out, or after transverse stretching, heat treatment is carried out to obtain a biaxially oriented polyester film. If necessary, the polyester film may be subjected to a corona discharge treatment or a coating treatment in the process. This film is wound up as a product roll at room temperature in an atmosphere having a relative humidity of 30 to 95%.

Next, a transfer ink layer is formed on the biaxially oriented polyester film of the present invention obtained as described above. At that time, a pretreatment such as a corona discharge treatment or an undercoat may be performed as necessary. The transfer ink is not particularly limited, and a known ink can be used. Specifically, a binder component, a coloring component, or the like may be used as a main component, and a softener, a flexible agent, a melting point regulator, a leveling agent, a dispersant, or the like may be added as an additive component as needed.

Specific examples of the main component include paraffin wax, carnauba wax as a binder component,
Well-known waxes such as ester wax and various polymers having a low melting point are useful, and carbon black and various organic and inorganic pigments or dyes are useful as a coloring agent component. Inks include sublimable inks.

As a method of providing the transfer ink layer on one side of the film of the present invention, a known method, for example, a hot melt coating, a solution coating method such as a gravure, reverse or slit die method with a solvent added, and the like are used. Can be used.

In order to prevent sticking of the thermal head, it is desirable to provide a known anti-fusing layer on the side of the film where the transfer ink layer is not provided. (Examples) Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

The evaluation method used in the present invention is as follows. (1) Number of localized charges An ultrasonic atomizer for generating mist by applying ultrasonic waves to water, a nozzle for ejecting mist, and a film stretching device provided with a box for filling the mist without diffusing it are used.

A film cut to a predetermined width and length is stretched over a box of the above apparatus, and mist generated by applying ultrasonic waves to water in an ultrasonic atomizer is applied to the inside of the box below the film. Fill and contact the film. After several minutes, the number of white spots having a major axis of 1 mm or more generated by fog adhering to the charges localized on the film surface is measured by visual observation or image processing. The measured area of the film is 3 m ² or more, and the number of localized charges is calculated from the following equation.

Number of localized charges (pieces / m ² ) = {number of white spots with fog (pieces)} / {measurement area of film (m ² )} (2) Coatability Film tension: 1.82 kg / Mm ² , film speed:
120 m / min. Under a condition of drying temperature: 100 ° C., a heat-resistant layer made of silicone-modified urethane resin having a thickness of 0.3 μm is provided on one side of the film by a bar coating method, and the film is wound into a roll. Subsequently, the film tension: 1.82 kg / m
m ² , film speed: 80 m / min. , Drying temperature: 7
A coating amount consisting of 60 parts of ethylene-vinyl acetate copolymer, 25 parts of carbon black, and 15 parts of hydrogenated rosin on the film surface opposite to the surface on which the heat-resistant layer was provided by the gravure coating method under the condition of 0 to 50 ° C. A 1.6 g / m ² ink layer is provided and wound into a roll.

The coating properties of each coating layer in the above steps are evaluated in the following three steps. …: There is no problem because no coating defect occurs in the process. △ ... coating defects major axis of less than 1mm occurs five / m ² or less in the process.

X: 6 / m ² or more coating defects having a major axis of 1 mm or more are generated in the process. (3) Winding property Winding property in the above step (2) is evaluated in the following three stages.

…: Slit and winding are good and there is no problem. Δ: Meandering slightly, but no winding deviation. X: Roll deviation and wrinkles occur.

(4) Surface roughness (Ra) The center line average roughness Ra (μm) is defined as the surface roughness.
It was determined as follows using a surface roughness measuring instrument (SE-3F) manufactured by Kosaka Laboratory Co., Ltd. That is, the reference length L (2.5 mm) is measured in the direction of the center line from the cross-sectional curve of the film.
When a roughness curve y = f (x) is represented by taking the center line X axis and the vertical magnification direction of the extracted portion as the Y axis, the value given by the following equation is represented by (μm). . The center line average roughness was obtained by calculating ten cross-sectional curves from the surface of the sample film, and expressing the average value of the center line average roughness of the sampled portion obtained from these cross-sectional curves. The tip radius of the stylus was 5 μm, the load was 30 mg, and the cut-off value was 0.08.
mm.

[0028]

(Equation 1) (Example 1) Silicon dioxide having an average particle diameter of 1.3 μm was added to 0.1 μm.
After drying polyethylene terephthalate containing 7% by weight, it is melted at 308 ° C. and extruded from a T-die into a sheet.
Speed 60m / min. The film was adhered to a casting drum set at 43 ° C. rotating by the electrostatic adhesion method and cooled and solidified to obtain an amorphous unstretched sheet. Then, in the vertical direction,
After stretching 2.7 times at 1 ° C and 1.59 times at 80 ° C, the film was stretched 4.62 times at 110 ° C in the transverse direction. 2 more
Heat treatment at 35 ° C, cool to room temperature, relative humidity 55%
The film was wound up using an AC static eliminator under the above atmosphere to obtain a 2.5 μm thick biaxially oriented polyethylene terephthalate film.

A heat-resistant layer and an ink layer were provided on the above-mentioned film, and the film was slit into a ribbon to evaluate workability.
The results obtained are shown in Table 1 together with those of the other Examples and Comparative Examples. (Example 2) Except that the film after the heat treatment was cooled to room temperature and wound up at a relative humidity of 30%, the same method as in Example 1 was used.
A biaxially oriented polyethylene terephthalate film having a thickness of 2.5 μm was obtained.

Next, Example 1 was carried out using the obtained film.
The workability was evaluated in the same manner as described above. Comparative Example 1 A biaxially oriented polyethylene terephthalate film having a thickness of 2.5 μm was obtained in the same manner as in Example 1 except that the film after the heat treatment was cooled to room temperature and wound up without relative charge at 25% and without static elimination. Was.

Next, Example 1 was carried out using the obtained film.
The workability was evaluated in the same manner as described above.

[0032]

[Table 1] As is evident from the results in Table 1, the films of Examples 1 and 2 satisfying the requirements of the present invention have excellent properties, whereas Comparative Example 1 having a large number of localized charges is ink-coated. Inferiority and winding property.

This embodiment has the following effects. (1) When the number of localized charges of the biaxially oriented polyester film is 5 / m ² or less, when the film is used as a base film for thermal transfer, thermal stencil, or a capacitor, during transport and winding, The film becomes hard to partially stick, and the occurrence of winding deviation and wrinkles is suppressed, and the winding property is improved. In addition, when used as a base film for thermal transfer or thermal stencil, coating defects such as unevenness and repelling occur during application and drying of an ink layer, a heat-resistant layer, an adhesive layer or a slippery layer. Can be suppressed.

(2) When the number of localized charges is 1 / m ² or less, winding property and coating property are further improved. (3) The biaxially oriented polyester film has a roughness of at least one side of 0.02-1 μm in center line average roughness (Ra).
m, the sliding property is improved. As a result, generation of static electricity due to friction between the films during winding, wrinkling of the films, and occurrence of trouble during processing are suppressed. Further, when used as a film for thermal transfer or thermal stencil printing, sharpness of printing is ensured, and lowering of sensitivity and wear of the thermal head are reduced.
When used as a film for capacitors,
A decrease in interlayer adhesion and a decrease in capacity are prevented.

(4) The desired biaxially oriented polyester film can be obtained by winding the stretched polyester film at room temperature in an atmosphere with a relative humidity of 30 to 95% while removing the charge using a charge removing device. It can be easily manufactured using polyester film manufacturing equipment.

(5) As a method for obtaining a film having a desired surface roughness, an additive particle method is used, and the average particle size of the inert fine particles to be blended is 0.1 to 10 μm, preferably 0.3 to 3 μm in equivalent sphere diameter. And the amount of the film is 0.01 to 5% by weight, preferably 0.05 to 5% by weight.
By setting the content to 3% by weight, more preferably 0.05 to 2% by weight, a film having a desired surface roughness can be easily obtained.

The inventions (technical ideas) other than those described in the claims which can be grasped from the embodiment will be described below together with their effects. (1) In the invention according to any one of claims 1 to 3, the polyester film has a thickness of 1
0 μm or less. In this case, the effect of improving the ink coating property and the slit property becomes remarkable as compared with a thick film.

(2) In the invention according to claim 4,
As a method for obtaining a film having a desired surface roughness, an additive particle method is used, the average particle diameter of the inert fine particles to be compounded is 0.1 to 10 μm in equivalent old diameter, and the compounding amount for the film is 0.01 to 5% by weight. %. In this case, a film having a desired surface roughness can be easily obtained.

[0039]

As described above in detail, the biaxially oriented polyester film according to the first to third aspects of the present invention is excellent in ink coating properties and slitting properties, and has high industrial value.

The biaxially oriented polyester film of the invention according to claim 2 has a localized charge number of 1 / m ² or less.
Ink coating properties and slit properties are further improved. Claim 3
The biaxially oriented polyester film of the invention described in (1) has improved winding properties.

According to the fourth aspect of the present invention, a biaxially oriented polyester film excellent in ink coating property and winding property can be easily manufactured by using existing polyester film manufacturing equipment.

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Claims (4)

[Claims] 1. A biaxially oriented polyester film, wherein the number of localized charges is 5 / m ² or less. 2. The biaxially oriented polyester film according to claim 1, wherein the number of localized charges is 1 / m ² or less. 3. The polyester film according to claim 1, wherein at least one surface has a center line average roughness (Ra) of 0.02 to 1
3. The biaxially oriented polyester film according to claim 1, wherein the thickness is μm. 4. 4. An amorphous unstretched sheet obtained by extruding a molten polyester resin from a die into a sheet shape, bringing it into close contact with a casting drum, and cooling and solidifying the same is stretched in a longitudinal direction and a transverse direction at a predetermined magnification. A biaxially oriented polyester film characterized in that after stretching, heat treatment is performed at a temperature higher than the temperature at the time of stretching, and then winding is performed at room temperature in an atmosphere having a relative humidity of 30 to 95% while using a charge removing device to remove electricity. Manufacturing method.