JP2001030449A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent polyester film which has no frosting defect on the film surface and is hardly wounded and has good sliding properties while high transparency is ensured. SOLUTION: A film prepd. by laminating a polyester layer contg. aluminum oxide fine aggregate particles and org. particles with a particle diameter distribution ratio R of at most 1.5 and with a thickness of 0.2-5 μm on at least one face of a polyester layer substantially free from particle is provided and it has a film inner haze converted in terms of thickness of 100 μm of at most 1.0%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film which is hardly damaged on the film surface and which is excellent in transparency, slipperiness, handleability, workability and the like. More specifically, the present invention relates to a polyester film suitable for use in plate making printing, X-ray photography, microfilm, electrophotography, metal deposition, and the like.

[0002]

2. Description of the Related Art One of the main uses of a polyester film is a so-called transparent film. Such a film is required to have not only transparency but also smoothness and scratch resistance in order to facilitate handling workability. . As a means for achieving such properties, a method of providing lubricity to the surface layer by a coating method or blending a lubricant is also known, but there are many difficulties in terms of cost, reliability, and the like.

[0003] In addition, there have been proposed limitations on the types and properties of particles and proposals for laminated films. For example, JP-A-3-20
JP-A-6645 proposes that the organic polymer fine particles coated with aluminum oxide be used to satisfy the transparency, slipperiness and abrasion resistance of the film.
Japanese Unexamined Patent Publication No. 7-314626 discloses that by using crosslinked polymer particles having a narrow particle size distribution, transparency and film surface condition are excellent (prevention of so-called marbling defects) and lubricity is satisfied. Japanese Patent Application Laid-Open Publication No. H11-157, pp. 147-64 discloses a film having a laminated structure, which reduces the amount of added particles and achieves both high transparency and smoothness.

However, in recent years, the requirement for transparency of a base film is such that a reduction in transparency due to light scattering on the surface of the base film due to a device of secondary processing such as coating of the surface of the base film causes a decrease in the inside of the base film. The problem is that the transparency is reduced by the scattering and absorption of light. Furthermore, due to cost reduction, the line speed of the film manufacturing process and the processing process for various applications is increasing, the film is easily damaged, and the film is also required to have a high quality level. Therefore, it is strongly desired that clear and clear images can be obtained without transparency and non-uniform so-called marbling defects on the film surface.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a film which is free from marbling defects, is less likely to be damaged, and has high transparency. An object of the present invention is to provide a transparent laminated polyester film having good sliding properties.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies and determined that the combination of particles and the film thickness contained in the surface layer of the laminated polyester film are specified. The inventors have found that the film characteristics are significantly improved, and have completed the present invention.

That is, the gist of the present invention is that at least one surface of a polyester layer (B) substantially containing no particles is
Aluminum oxide fine aggregated particles and the particle size distribution ratio R are 1.5
A film obtained by laminating a polyester layer (A) having a thickness of 0.2 to 5 μm containing the following organic particles, and the internal haze of the film converted to a thickness of 100 μm is 1.0%
A laminated polyester film characterized by the following.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester in the present invention includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalene-2,6-dicarboxylic acid, and ethylene glycol, diethylene glycol, tetramethylene glycol, neopentyl glycol, and 1,4-cyclohexanedicarboxylic acid. It is a polyester containing an ester with a glycol such as methanol as a main component. The polyester is obtained by directly polymerizing an aromatic dicarboxylic acid and a glycol, a method of subjecting an aromatic dicarboxylic acid dialkyl ester and a glycol to a transesterification reaction, followed by polycondensation,
Alternatively, it can be obtained by a method such as polycondensation of a diglycol ester of an aromatic dicarboxylic acid.

Representative examples of the polyester used in the present invention include polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate (PEN).
Etc. are exemplified. Such a polyester may be a homopolymer that is not copolymerized, and 10 mol% or less of the dicarboxylic acid component is a dicarboxylic acid component other than the main component, and / or 10 mol% or less of the diol component is a non-main component. It may be a copolyester that is a diol component.

In the present invention, the polyester containing substantially no particles refers to the polyester as described above, and a method for minimizing formation of particles formed by precipitation of a catalyst during the production of the polyester (for example, JP 8
No. 198960) or synthesized without any particles added for purposes other than the purpose of the polymerization catalyst. This polyester does not contain or contains insoluble particles that absorb or scatter light, so that a film having high transparency can be obtained. The film haze of such a film consisting of only polyester is
It is usually 0.5% or less when converted to a thickness of 100 μm.

In the present invention, it is essential to laminate a specific polyester layer (layer A) on at least one surface of the layer (B) made of polyester substantially containing no particles. Specific organic particles are used in the polyester (A) layer in order to improve the lubricity of the film.
The organic particles used in the present invention to improve the lubricity of the film preferably have a sharp particle size distribution, and the particle size distribution ratio R of the parameter representing the sharpness is preferable.
(Definition will be described later) is usually 1.5 or less, preferably 1.3.
It is as follows. If this value exceeds 1.5, the marbling defect of the film becomes remarkable.

The average particle size of the organic particles is not particularly limited, but is usually 0.5 to 5.0 μm, preferably 0.8 to 3.0 μm, and particularly preferably 1.0 to 2.0 μm.
μm. Particles having an average particle size of less than 0.5 μm require a large amount of addition to impart lubricity to the film,
As a result, the haze inside the film tends to increase. On the other hand, when the average particle size exceeds 5.0 μm, deterioration of the surface state due to formation of coarse projections, that is, generation of so-called marbling defects may be a problem.

The amount of the organic particles added is not particularly limited, but is usually 0.0005 to 0.5% by weight, preferably 0.001 to 0.3% by weight, and particularly preferably 0.00 to 0.3% by weight.
0.01 to 0.1% by weight. The amount of organic particles added is 0.0
If the amount is less than 005% by weight, the effect of improving the slipperiness tends to be insufficient. If the amount exceeds 0.5% by weight, a problem may occur in terms of internal haze and deterioration of the surface state (marbling defect).

The degree of deformation of the organic particles in the film (the definition will be described later) is usually from 1.3 to 5, preferably from 1.5 to 5.
3.5. When the degree of deformation is less than 1.3, the voids in which the particles are almost spherical are increased, and as a result, the haze inside the film tends to increase. On the other hand, the degree of deformation is 5
If it exceeds, the projections formed on the film surface tend to be low, and the slipperiness tends to deteriorate.

Examples of the organic particles used in the present invention include crosslinked polymer particles, silicone rubber particles, and the like. These particles may be used alone or in combination of two or more. Among these, crosslinked polymer organic particles are preferable, and typical examples include polymer particles having an appropriate crosslinked structure, and a monovinyl compound having only one aliphatic unsaturated bond in the molecule ( A copolymer of A) and a compound (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent can be exemplified. In this case, such a copolymer desirably has a group capable of reacting with the polyester on the particle surface, and examples of such a functional group include a hydroxyl group and a carboxyl group.

The compound (A) which is one component of the copolymer includes acrylic acid, methacrylic acid and their methyl or glycidyl esters, maleic anhydride and its alkyl derivatives, vinyl glycidyl ether, vinyl acetate, styrene, alkyl Substituted styrene and the like can be mentioned. Examples of the compound (B) include divinylbenzene, divinylsulfone, and ethylene glycol dimethacrylate. One or more of each of the compounds (A) and (B) is used, but a compound having ethylene or a nitrogen atom may be copolymerized. In polymerization, an emulsion polymerization method is preferably applied. The term “emulsion polymerization method” as used herein refers to a broadly-defined emulsion polymerization that includes concepts such as so-called soap-free polymerization and seed polymerization.

Further, in the polyester (A) layer of the film of the present invention, specific aluminum oxide fine aggregated particles are used in order to prevent the film from being damaged. The primary particle size of the aluminum oxide fine aggregated particles used to prevent scratches on the film in the present invention is preferably in the range of 5 to 300 nm, and the average particle size of the aggregated particles is 0.01 to 0.3 μm.
Is preferable. When the primary particle diameter and the average particle diameter of the aluminum oxide fine aggregated particles are in this range, the effect of preventing the film from being damaged is large.

Examples of such finely aggregated aluminum oxide particles include γ-type and δ-type aluminum oxide produced by flame hydrolysis using anhydrous aluminum chloride as a raw material. The addition amount of the fine aggregated particles is not particularly limited,
Usually 0.05 to 3% by weight, preferably 0.05 to 0.5
% By weight. If the addition amount is less than 0.05% by weight, the effect of preventing damage to the film tends to be low.
If the amount is more than 10% by weight, the transparency of the film may be impaired.

Further, one of the features of the present invention is that the thickness of the polyester (A) layer is in the range of 0.2 to 5 μm. When the thickness of the polyester (A) layer is less than 0.2 μm, the particles easily fall off the film, and the above-mentioned organic particles cannot be used. When the thickness exceeds 5 μm, the haze inside the film increases, which is not preferable. The ratio (d / t) of the average particle size d of the organic particles to the thickness t of the polyester (A) layer is preferably in the range of 0.5 to 3. If the ratio (d / t) is less than 0.5, the projections formed on the film surface become small, and the amount of added particles must be increased in order to obtain the effect of easy lubrication. Tend to increase. Also, the ratio (d / t)
If the number exceeds 3, particles may easily fall off from the film surface, which may cause deterioration of the surface state or damage to the film surface.

The polyester (A) layer of the film of the present invention contains, if necessary, additives such as an antistatic agent, a coloring agent, an antioxidant, an antifoaming agent, a fluorescent whitening agent and a light shielding agent. There may be. The thickness of the laminated polyester film of the present invention is usually in the range of 20 to 300 μm, and the haze value inside the film is 1.0% or less in terms of a thickness of 100 μm. Here, conversion to 100 μm refers to an estimated value of internal haze when a film of 100 μm is obtained by changing only the film thickness of the polyester (B) layer while leaving the polyester (A) layer as it is (the measuring method will be described later). ).

The coefficient of friction between the films of the present invention is generally 0.5 or less, preferably 0.4 or less. In a film having a coefficient of friction of more than 0.5, so-called grooving marks and wrinkles are generated at the time of film winding or slitting at the time of film production, the yield may be reduced and the cost may be increased. Scratches or meandering may occur during processing.

If necessary, one or both surfaces of the polyester film of the present invention may be subjected to a coating treatment for imparting lubricity, releasability, antistatic agent, easy adhesion, and the like. Next, the production method of the film of the present invention will be specifically described, as long as the constitutional requirements of the present invention are satisfied.
It is not particularly limited to the following examples.

After the polyester containing substantially no particulate lubricant and the polyester containing a predetermined amount of particles are melt-extruded from separate extruders, they are formed into a laminar flow in a molten polymer channel tube or an extrusion die. And discharge from an extrusion die to form an unstretched laminated film. The unstretched film thus obtained is subjected to the next stretching step. In the stretching step, the unstretched film is treated with (Tg-1
In the temperature range of 0) ° C to (Tc-10) ° C, the area magnification is usually 1.1 to 50 times, preferably 6 to 30 times.
The film is stretched in the longitudinal direction (longitudinal direction) and / or the width direction (horizontal direction) within the range of twice.

The stretching method may be uniaxial stretching or biaxial stretching depending on the application. When performing biaxial stretching, any of sequential biaxial orientation stretching, simultaneous biaxial orientation stretching, and a combination thereof may be used. In the case of sequential biaxial stretching, generally, a method of stretching in the longitudinal direction and then stretching in the transverse direction is preferably adopted. When the film is stretched in the longitudinal and transverse directions, it may be stretched in one step, but may be stretched in multiple steps or may be provided with a heat treatment step for relaxing the orientation between the multiple steps.

In order to impart adhesiveness, antistatic ability and releasability to the film during or after the stretching step, a coating layer may be formed on one or both sides of the film, or a discharge treatment such as a corona treatment may be performed. Can also be applied.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples and comparative examples, “parts” means “parts by weight”. The measurement methods and the definitions of terms used in the present invention are as follows. (1) Average particle size Observing the particles with a scanning electron microscope, finding the maximum and minimum diameters for each particle, and calculating the arithmetic mean of the particles is the particle size (diameter) of one particle
And The average particle diameter of the particle group indicates the particle diameter (diameter) at a point where the volume fraction of the equivalent particle diameter is 50%. (2) Particle size distribution ratio (R) The particle size distribution was determined in the same manner as in the method for measuring the average particle size. Integration was performed from the large particle side in the equivalent sphere distribution, and the particle size distribution ratio (R) was calculated from the following equation.

[0027]

(Equation 1) (3) Internal haze of the film The internal haze of the film was measured using a spectroscopic turbidimeter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. In addition, it measured in the quartz cell using ethanol as a rough surface compensation solvent. (4) Degree of Particle Deformation A cut surface obtained by cutting a small piece of the film sample in the stretching direction was observed with a scanning electron microscope. With respect to the organic particles present in the polyester A layer, the maximum diameter and the minimum diameter were determined for each particle, and the ratio was calculated. This value was determined for at least 100 particles, and the arithmetic mean thereof was defined as the degree of deformation. (5) Coefficient of friction Two films cut to a width of 15 mm and a length of 150 mm are superimposed on a smooth glass plate, a rubber plate is placed thereon, a load is further placed thereon, and the two films are brought into contact with each other. The pressure was set to 2 g / cm ² and the films were slid at 10 mm / min to measure the frictional force. The measurement was performed at a temperature of 23 ° C. ±
The test was performed in an atmosphere at 1 ° C. and a humidity of 50% ± 5%, and the value at the point of sliding by 2 mm was defined as the friction coefficient. (7) 100 μm converted value of the internal haze of the film 1 of the internal haze of the film whose thickness deviates from 100 μm
The value of 00 μm was determined as follows.

That is, the total thickness of the film was measured by a micrometer, and the thickness of the surface film was measured by the method (6), and the polyester A layer (L1; μ) was measured.
m) and the thickness of the polyester B layer (L2; μm). Further, the internal haze value (H0) is obtained by the above method (3). The polyester A layer is ashed by a low-temperature plasma incinerator, the film is immersed in an aqueous solution containing a small amount of a surfactant, and ultrasonically washed for 1 minute. After drying, the film thickness (Lb; .mu.m) and internal haze (Hb) of only the polyester B layer are determined by the method (3).

100 μm converted value of internal haze (H100)
Is calculated by the following equation.

[0030]

## EQU2 ## H100 = H0 + Hb (100-L1-L2) / Lb (8) Marbling The film was subjected to aluminum deposition with a thickness of 200 angstroms, and the marbling state was visually classified into the following three ranks.

〇: Marbling is not observed at all, and has a very uniform and fine surface structure. Δ: A spot pattern considered to be based on large particles is observed,
There is a somewhat rough feeling. X: There is a clear spot pattern and there is a rough feeling. (9) Anti-abrasive property A sample film slit to 1/2 inch has a diameter of 6 mm.
Tension 50g, wrap angle 13
Rub once at 5 ° at a running speed of 4 m / sec. Aluminum was vapor-deposited on the friction surface of the film so as to have a thickness of about 1000 °, and the amount of scratches was visually judged and divided into the following five stages.

1: Extremely large amount of scratches 2: Large amount of scratches 3: Intermediate amount of scratches between 2, 4 4: Low amount of scratches 5: No scratches Among these, 3 or more This is an area that can be practically used. (10) Presence or Absence of Scratches A 1-meter square sample film was illuminated with a flashlight in a dark room to check for scratches, and it was confirmed under normal room lighting whether or not the scratches were visible.

：: No scratches Δ: 1 to 3 scratches X: 4 or more scratches Example 1 [Preparation of particle-containing raw resin] 0.25 parts of potassium persulfate and dispersion in 120 parts of deionized water After adding the stabilizer, 7 parts of ethylene glycol dimethacrylate, 4 parts of n-butyl acrylate, and 1 part of divinylbenzene were added, and 70 to 75 ° C.
After 6 hours, crosslinked polymer particles were obtained. The particle size distribution ratio (R) of the obtained particles is 1.2, and the average particle size is 1.
It was 0 μm.

Ethylene glycol was added to the resulting water slurry of crosslinked polymer particles, and water was distilled off under reduced pressure under heating to obtain an ethylene glycol slurry of crosslinked polymer particles. Next, using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 part by weight of magnesium acetate tetrahydrate was used as a catalyst, and the reaction starting temperature was 1 point.
The temperature was raised to 50 ° C., and the reaction temperature was gradually raised as methanol was distilled off. After 4 hours, 10 parts by weight of an ethylene glycol slurry containing 3 parts by weight of the above-mentioned crosslinked polymer particles was added to the reaction mixture in which the transesterification was substantially completed, and ethyl acid phosphate was used as a stabilizer and a polymerization catalyst. After adding 04 parts and 0.04 part of antimony trioxide, a polycondensation reaction was performed for 4 hours. That is, the temperature is gradually raised from 230 ° C.
0 ° C. On the other hand, the pressure was gradually reduced from the normal pressure, and finally was 0.3 mmHg. After 4 hours from the start of the reaction, the reaction is stopped at the point when 4 hours have passed, and the polymer is discharged under nitrogen pressure.
A raw material chip containing crosslinked polymer particles was obtained.

Further, fine aggregated particles of γ-type aluminum oxide having an average primary particle diameter of 20 nm and an average particle diameter of 0.1 μm are dispersed in ethylene glycol and added at the time of polymerization in the same manner as described above to obtain a raw material chip containing aluminum oxide. Was. The polyethylene terephthalate containing these added particles was blended with a raw material chip of polyethylene terephthalate containing no added particles obtained by the same method as described above so as to have the added amount in the layer A shown in Table 1 below.

The polyethylene terephthalate containing no added particles obtained by the same method as described above was used as a raw material for the polyester B layer. [Production of Film] After the raw material chips of polyethylene terephthalate were dried at 170 ° C. for 3 hours, the raw material chips of the polyester A layer were supplied to the sub-extruder, and the raw material chips of the polyester B layer were supplied to the main extruder.
After being melted at 300 ° C. and branching the molten polymer of the sub-extruder into two layers of front and back of the film, it is separated by a feed pump and the molten polymer from the main extruder through a gear pump filter, and is taken up by a casting drum through a die. An unstretched film was used. At the time of casting, an electrostatic contact method was adopted.

The thus-obtained two-layer, three-layer laminated unstretched film is fed to a longitudinal stretching roll, and a film temperature of 8
After stretching 2.4 times at 3 ° C. (with IR heater), stretching 1.2 times at 87 ° C. (with IR heater) and setting the birefringence of the film after longitudinal stretching to 0.62, the tenter And stretched 3.9 times in the transverse direction at 130 ° C. to obtain a biaxially oriented film.

Next, the obtained biaxially oriented film was guided to a heat setting zone and heat set while relaxing 3% in the width direction at 235 ° C. for 5 seconds. The thickness of the polyester A layer was controlled by adjusting the discharge amount of a gear pump of the sub-extruder. The total thickness of the obtained transparent laminated film is 100 μm, and the thickness of the polyester (A) layer is 1.5.
μm. The degree of deformation of the crosslinked polymer particles is 2.5
Met.

Example 2 A film was prepared in the same manner as in Example 1 except that the method for preparing the particles was as follows. That is, after adding 0.25 parts of potassium persulfate and a dispersion stabilizer to 120 parts of demineralized water, 7 parts of methyl methacrylate and 3 parts of styrene were added.
And 2 parts of divinylbenzene, and polymerization was carried out at 50 to 75 ° C., and after 8 hours, crosslinked polymer particles were obtained. The particle size distribution ratio (R) of the obtained particles is 1.3, and the average particle size is 1.1 μm.
Met. The degree of deformation of the crosslinked polymer particles in the film was 3.0.

Comparative Example 1 A film was obtained in the same manner as in Example 2 except that fine particles of aluminum oxide were not used. Comparative Example 2 A film was obtained in the same manner as in Example 1 except that pulverized organic particles were used.

Comparative Example 3 A film was obtained in the same manner as in Example 1 except that no organic particles were used. The physical properties and performance of the film thus obtained are summarized in Table 2 below.

[0042]

[Table 1]

[0043]

[Table 2] As is clear from Tables 1 and 2, Examples 1 and 2, which satisfy the requirements of the present invention, have a small internal haze and have no unevenness on the film surface called so-called marbling defects, and are used for plate making printing, X-ray photography, and the like. Can be advantageously used for the base film. In addition, the coefficient of friction is low, during film production, for example, at the time of film winding,
There is almost no occurrence of wrinkles or creaking due to the ease of adhesion between films, and processing and handling are easy. Further, the surface of the film is not easily damaged during the production of the film, and the occurrence of scratches during secondary processing for various applications can be prevented.

[0044]

The polyester film of the present invention contains specific organic particles and aluminum oxide fine agglomerated particles. By forming the film into a laminated structure, it obtains excellent transparency and lubricity, and provides marbling defects and scratches. No scratches were generated, and the occurrence of scratches during the secondary processing could be prevented, and its industrial value was high.

Continued on front page F-term (reference) 4F100 AA19B AA19H AK01B AK01H AK25H AK41A AK41B AK42 BA02 BA03 BA06 BA10B BA13 CA23B DE01B DE01H EJ38 JB20H JK09 JK16 JN01 JN02 YY00 YY00B YY012B04Y022B022 BC

Claims (1)

[Claims] 1. A polyester layer (B) containing substantially no particles and having a thickness of 0.2 to 0.2% containing finely agglomerated particles of aluminum oxide and organic particles having a particle size distribution ratio R of 1.5 or less. A laminated polyester film comprising a laminated polyester layer (A) having a thickness of 5 μm, wherein the internal haze of the film converted to a thickness of 100 μm is 1.0% or less.