JPH08192503A - Polyester film - Google Patents

Abstract

PURPOSE: To obtain a polyester film free from a surface defect and having a smooth surface by laminating a composite layer consisting of non-liquid crystal polyester and liquid crystal polyacrylate on at least the single surface of a composite layer having the same compsn. CONSTITUTION: A polyester film is formed by laminating a composite layer (B) consisting of non-liquid crystal polyester and liquid crystal polyacrylate on at least the single surface of a composite layer (A) consisting of non-liquid crystal polyester and liquid crystal polyacrylate. Liquid crystal polyacrylate is polyester having a melligen group and having melt moldability and liquid crystal forming properties. As a representative example of nonliquid crystal polyester, there are polyethylene terephthalate, polybutylene terephthalate, etc. The content of liquid crystal polyacrylate in the composite layer (B) is less than that of liquid crystal polyacrylate in the composite layer (A) and set to 0-10wt.%, pref., 0-1wt.% to develop smoothness free from a surface defect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film having a smooth surface and no defects and high rigidity, and further to a polyester film having high weather resistance and cleavage resistance. Specifically, it relates to a base film for magnetic recording and a base film used for agriculture and outdoors.

[0002]

2. Description of the Related Art In order to increase the rigidity, a stretching operation is repeated many times, so that a relative speed difference is likely to occur between the film surface and a stretching roll, resulting in scratches on the film surface. Surface defects such as scratches and feathers were often generated.

[0003]

That is, it is an object of the present invention to provide a polyester film having a high rigidity and a smooth surface which does not have surface defects such as scratches, scratches, feathers and craters on the film surface. .

[0004]

That is, a composite layer (B) composed of a non-liquid crystalline polyester and a liquid crystalline polyarylate is formed on at least one surface of a composite layer (A) composed of a non-liquid crystalline polyester and a liquid crystalline polyarylate. It is a polyester film characterized by being laminated.

The liquid crystal polyarylate referred to in the present invention is
A melt-moldable polyester having a melogen group in the main chain and having a liquid crystal forming property. Particularly preferred are the following units. As the structural unit derived from diol,

Embedded image (X and Y are each independently hydrogen, halogen, carbon number 4
The following alkyl groups are represented. )

Embedded image (X represents hydrogen, halogen, or an alkyl group having 4 or less carbon atoms.)

Embedded image

[Chemical 4] Further, as the structural unit derived from dicarboxylic acid,

Embedded image (X represents hydrogen, halogen, or an alkyl group having 4 or less carbon atoms.)

[Chemical 6]

[Chemical 7] Further, as the structural unit derived from hydroxycarboxylic acid,

Embedded image (X represents hydrogen, halogen, or an alkyl group having 4 or less carbon atoms.)

[Chemical 9] Further, it is also effective to introduce the following structural units in the liquid crystalline polyacrylate of the present invention in order to adjust the melt viscosity and melting point. That is,

[Chemical 10]

[Chemical 11] It is also effective to introduce a structural unit represented by the following general formula. That is,

[Chemical 12] (Where X represents O, CH ₂ , C (CH ₃ ) ₂ , SO ₂ ) or other structural units that are relatively freely rotatable between aromatic rings, or

[Chemical 13] Examples thereof include structural units derived from aliphatic diols and aliphatic dicarboxylic acids represented by (where m and n are integers from 2 to 10).

And, as the particularly preferred liquid crystalline polyacrylate, those having the following structural formulas are listed. That is

Embedded image

[Chemical 15]

Embedded image

[Chemical 17]

Embedded image

[Chemical 19]

Embedded image

[Chemical 21]

[Chemical formula 22]

[Chemical formula 23] Here, Σni = 100. Of course, each ni is preferably 4 or more. Further, a part of these polymers may be substituted in various substitution chambers such as halogen. The liquid crystal polyacrylate has a melt viscosity of 100.
It is preferably about 1000 poise. In the case of the present invention, P
Most preferred are the copolymers of -hydroxybenzoic acid (PHB) and ethylene terephthalate, PHB / 6-hydroxy-2-naphthoic acid and PHB / 4,4'dihydroxybiphenyl / terephthalic acid / isophthalic acid.

Typical examples of non-liquid crystalline polyesters include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polycyclohexane methylene terephthalate and copolymers thereof.
Of course, a polyester having an ether component in the main chain, for example, a copolymer of diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol, etc. may be used.

The intrinsic viscosity of the amorphous liquid polyester in the composite layer (A) is 0.7 or more, preferably 0.85 or more, more preferably 1.0 in terms of high rigidity, weather resistance and cleavage resistance.
It should be above. The intrinsic viscosity of the non-liquid crystalline polyester in the composite layer (B) may be the same as that in the composite layer (A), but is lower than that of the composite layer (A) and is 0.5 to 0.5.
It is preferably about 1.0. However, since it is a laminated film, it is very difficult to obtain the intrinsic viscosity of each layer. Therefore, the intrinsic viscosity of the non-liquid crystalline polyester measured as the entire laminated film is 0.7 or more, preferably 1.0 or more. Is good. Further, the melt viscosity of the non-liquid crystalline polyester is preferably 5 times, preferably 10 times, more preferably 20 times or more that of the liquid crystalline polyacrylate to be composited. The melting point Tm of the non-liquid crystalline polyester is preferably equal to or higher than that of the liquid crystalline polyacrylate. In the case of the present invention, as the non-liquid crystalline polyester in the composite layer (A), polyethylene terephthalate or polyethylene naphthalate having an intrinsic viscosity of 0.7 or more, preferably 0.85 or more, more preferably 1.0 or more is used. Particularly preferred.

In the composite of the present invention, the liquid crystalline polyarylate is composited with the non-liquid crystalline polyester, but the composite form is not particularly limited, but the liquid crystalline polyacrylate is finely dispersed in the non-liquid crystalline polyester. There is a skin
There are various forms such as core type, sea-island type, multi-layer type and fiber type, but in the case of the present invention, it is particularly preferable that the liquid crystalline polyacrylate is finely dispersed in a fibrous state. Diameter is 3μm or less, preferably 1μ
m or less, and more preferably 0.5 μm or less is not only excellent in preventing decrease in melt viscosity and preventing thermal decomposition, but also good in increasing rigidity, improving weather resistance, and improving cleavage resistance. . The aspect ratio of the fibers at this time is 10 or more, preferably 50 or more. The amount of the liquid crystalline polyacrylate added to the composite layer (A) is 0.1 to 40% by weight, preferably 0.3 to 15% by weight, and more preferably 0.5 to 10% by weight. This is because if the addition amount is less than 0.1% by weight, it is not possible to obtain a film having high rigidity, weather resistance, and cleavage resistance, which has the effect of the present invention and has a high intrinsic viscosity without surface defects. When it exceeds 40% by weight, not only the surface defects of the polyester film of the present invention become apparent, but also high elasticity, toughness, dimensional stability and the like balanced in the film plane cannot be obtained, and an appropriate breaking elongation is also obtained. This is because the degree cannot be obtained.

The liquid crystalline polyacrylate in the composite layer (B) is less than the liquid crystalline polyacrylate in the composite layer (A) in an amount of 0 to 10% by weight, preferably 0 to 1% by weight, which is the surface. This is to obtain smoothness without defects.

The film of the present invention may contain only liquid crystalline polyacrylate and non-liquid crystalline polyester,
In addition, a compatibilizer such as epoxy or oxazoline, a plasticizer, a weatherproofing agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a coloring agent, and a conductive agent may be added and contained.

The film of the present invention may be the above-mentioned laminated film alone, but may be laminated with another polymer layer such as another polyester, polyolefin, polyamide, polyvinylidene chloride, acrylic polymer metal thin film or the like.

The film of the present invention may be an unstretched / unoriented film, but a known uniaxially or biaxially oriented / heat treated oriented film is preferred in terms of high elasticity, toughness and heat resistance.

As the laminated polyester film of the present invention, the composite layer (B) / composite layer (A) / composite layer (B), composite layer (B) / composite layer (A), composite layer ( There are laminated forms such as A) / composite layer (B) / composite layer (A), which can be arbitrarily used depending on the application and purpose. For example, composite layer (B) / composite layer (A)
In the case of a three-layer laminated film consisting of / composite layer (B), a film having excellent surface smoothness and high rigidity and high strength without surface defects can be obtained, which is particularly suitable as a base film for magnetic recording. Can be. At this time, as a measure of the surface smoothness, the center line average roughness Ra is 200 nm or less, preferably 100 nm or less, more preferably 20 nm or less. As a measure of high rigidity, the sum of Young's modulus in the longitudinal direction and the width direction of the film is 1200 kg / mm ² or more, preferably 1500 kg / mm ² or more, and more preferably 1800 kg / mm ² or more.

Further, composite layer (A) / composite layer (B) /
In the case of a three-layer laminated film composed of the composite layer (A), a film excellent in weather resistance, cleavage resistance, slipperiness, drawability, etc. is obtained, and is suitable for agriculture, electrical insulation, graphics, etc. Can be a film.

The thickness of the composite layer (A) layer and the composite layer (B) layer can be arbitrarily set according to the use and purpose, but the thickness of the central layer is 50% or more of the laminated film thickness. In many cases, a thicker layer, preferably 80% or more, provides the characteristics suitable for the purpose. The total thickness of the laminated film of the present invention is 0.3
It can be arbitrarily set from μm to 3 mm. For example, in the case of magnetic recording use, 3 to 200 μm, and in the case of electrical insulation use,
50-500μm, 25-350μ for agricultural use
m, OA / FA applications, it can be set to 0.3 to 250 μm.

Next, the method for producing the laminated film of the present invention will be described. The composite A and the composite B in which the liquid crystalline polyarylate was added to the non-liquid crystalline polyester polymer were supplied to separate known extruders, melted, and then laminated in two or three layers in an adapter or a die. Then, it is discharged from the die and adhered and solidified on the cooling body to obtain a laminated film. If necessary, stretching or heat treatment may be performed to orient and crystallize the molecules. Further, it is obvious that surface activation treatment such as corona discharge may be performed.

[0018]

[Measurement Method of Physical Property Values] The measurement method of physical property values used in the present invention will be described.

(1) Intrinsic viscosity [η] The polymer or film is melted using o-chlorophenol as a solvent. Since the liquid crystalline polyarylate is often unmeltable, it was obtained by converting it into the weight of the non-liquid crystalline polyester after removing it by a centrifugal separation method.

[0020]

[Equation 1] Specific viscosity η _sp = relative viscosity η _r −1 The unit is dl / g.

(2) Surface Roughness Ra The center line average surface roughness Ra measured at a cutoff of 0.25 mm was determined according to JIS B0601 (1976).

[0022]

[Equation 2] (3) Young's modulus Measured at 25 ° C. according to JIS K7127. It represents the slope of the strength / elongation curve, and the unit is kg / mm ² .

(4) Fiber Diameter of Liquid Crystalline Polyacrylate The film was dipped in liquid nitrogen, the film was sufficiently cooled, the film was split in the air, and its cross section was observed with a scanning electron microscope (SEM). . The unit is expressed in μm.

(5) Melt viscosity [η] The value at a shear rate of 100 (1 / sec) was measured using a melt indexer. The unit is expressed in poise.

(6) Surface defects "Scratches" caused by the film surface when the film surface is observed directly with the naked eye and under crossed Nicols polarization.
It was classified into three types and judged according to the frequency of surface defects such as "scratches" and "feathers". Area to observe is 10
It is equivalent to m ² . ◯: When the above-mentioned surface defects are not observed at all under any observation Δ: When it is invisible to the naked eye, but visible under polarized light ×: When easily visible under the naked eye or polarized light

[0026]

EXAMPLES Examples and comparative examples will be shown below in order to clarify the effects of the present invention.

Examples 1 to 5 and Comparative Example 1 Polyethylene terephthalate raw material having a intrinsic viscosity of 1.4 as a non-liquid crystalline polyester (melting point: 265 ° C., melt viscosity: 10)
000 poise) as a liquid crystalline polyarylate,
Liquid crystal polyester (melting point 260 ° C., liquid crystal starting temperature 240 ° C., melt viscosity 25) composed of P-hydroxybenzoic acid (80 mol%) and ethylene terephthalate (20 mol%)
0 poise) was used. As shown in Table 1, the content of the liquid crystalline polyacrylate was 3% in the polymer of the composite layer (A).
˜45% by weight.

On the other hand, polyethylene terephthalate having an intrinsic viscosity of 0.65 is used as the non-liquid crystalline polyester in the composite layer (B), and the same liquid crystalline polyacrylate as that used in the composite layer (A) is used. Composite layer (B)
The content of the liquid crystalline polyacrylate was adjusted to 0 to 15% by weight.

After the mixture was dried, each mixture was fed to a separate extruder and melted at 285 ° C. to form a composite layer (B) / composite layer (A) / composite layer (B) in three layers. After being laminated in the die, the mixture was discharged from the T-die die, and an electrostatic charge was applied to closely adhere and solidify to the cooling body kept at 25 ° C. The cast sheet was stretched 4 times in the longitudinal direction at 95 ° C., then stretched 4 times in the width direction at 100 ° C., and once cooled to 60 ° C., 2
It was heat-set at 05 ° C. to obtain a biaxially oriented film having a thickness of 5.6 μm. At this time, the thickness of the composite layer (B) was 0.8 μm, and the thickness of the composite layer (A) was 4.0 μm.

By thus laminating the composite layer (B) / composite layer (A) / composite layer (B) in three layers, there is no surface defect, the surface is smooth, the Young's modulus is high, and the rigidity is high. It turns out that the film will be high.

Example 6 Instead of polyethylene terephthalate having an intrinsic viscosity of 1.4 for the composite layer (A) used in Example 1, an intrinsic viscosity of 0.6 was used.
A biaxially oriented film was obtained in the same manner as in Example 1 except that the polyethylene terephthalate of Example 7 was used.

Example 7 When the amount of the liquid crystalline polyacrylate contained in the composite layer (A) in Example 1 was reduced from 3% by weight to 0.05% by weight, the composite layer (A) was extruded. Since the torque became abnormally high and more shear heat was generated, the extrusion temperature was 2
A biaxially oriented film was obtained in the same manner as in Example 1 except that the temperature was raised to 98 ° C.

As a result, the intrinsic viscosity of the laminated film was greatly decreased probably due to thermal decomposition, and only a film having a low rigidity and a rough surface was obtained.

The liquid crystalline polyacrylate in the composite layer (A) of Examples 1 to 3 and Comparative Example 1 was dispersed in a needle shape having a diameter of 0.5 μm. In Examples 6 and 7, the liquid crystalline polyacrylate was used. Are dispersed in a rod shape having a diameter of 5 to 10 μm.

Example 8 Polyethylene-2,6-naphthalate (melting point 274 ° C., melt viscosity 30,000 poise) having an intrinsic viscosity of 1.0 was used as the non-liquid crystalline polyester, and P- which was used in Example 1 as the liquid crystalline polyarylate. A liquid crystalline polyester composed of hydroxybenzoic acid and ethylene terephthalate was used.
The composition of the composite layer (A) was obtained by adding 3% by weight of the liquid crystalline polyacrylate to the polyethylene-2,6-naphthalate.

On the other hand, as the non-liquid crystal polyester of the composite layer (B), only polyethylene terephthalate having an intrinsic viscosity of 0.87 (melting point 265 ° C., melt viscosity 3000 poise) was used.

After feeding each of the above compositions to a separate extruder and melting at 290 ° C., the composition layer (A) / composite layer (B) / composite layer (A) is formed in the die. Three layers were stacked, discharged from a T-die, and adhered and solidified on a cooling body cooled to 25 ° C. while applying an electrostatic charge. The sheet was stretched in the longitudinal direction and the width direction by 4 times at 95 ° C. and then heat-solidified at 235 ° C. to have a thickness of 250 μm (complex layer (A) was 10 μm each, and composite layer (B) was 230 μm).
A biaxially oriented film of m) with an intrinsic viscosity of 0.78 was obtained.

Since the three-layer laminated film comprising the composite layer (A) / composite layer (B) / composite layer (A) is formed in this manner, it has excellent weather resistance and cleavage resistance, and has a smooth surface and no surface. It can be seen that a defective film can be obtained.

[0039]

[Table 1]

[0040]

EFFECT OF THE INVENTION By using a laminated film in which two or more layers of a composite of a non-liquid crystalline polyester and a liquid crystalline polyarylate are laminated like the film of the present invention, the following excellent effects are exhibited. .

(1) An excellent film having a high rigidity and a high strength, a smooth film surface, and no surface defects.

(2) It has excellent heat resistance stability, a small number of terminal carboxyl groups, and little change in physical properties due to heating.

(3) The amount of oligomers in the film is small, and the film surface does not become soiled or turbid due to heating.

(4) Electrical insulation, magnetic recording, OA / F
Excellent film for A, agricultural, graphic, etc.

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Claims (7)

[Claims] 1. A composite layer (B) composed of a non-liquid crystalline polyester and a liquid crystalline polyarylate is laminated on at least one surface of a composite layer (A) composed of a non-liquid crystalline polyester and a liquid crystalline polyarylate. Characteristic polyester film. 2. The polyester film according to claim 1, wherein the liquid crystal polyarylate in the composite layer (A) is 0.1 to 40% by weight. 3. The liquid crystal polyarylate in the composite layer (B) is 0 to 10% by weight and less than that in the composite layer (A). The described polyester film. 4. The intrinsic viscosity of the non-liquid crystalline polyester in a film obtained by laminating the composite layer (B) on at least one surface of the composite layer (A) is 0.7 or more. The polyester film according to any one of claims 1 to 3. 5. The polyester film according to any one of claims 1 to 4, which is a uniaxially or biaxially oriented film. 6. The center line average roughness Ra is 200 nm or less,
The sum of Young's modulus in the longitudinal direction and the width direction is 1200 kg /
It is mm ² or more, Claim 1-Claim 5
The polyester film according to any one of 1. 7. The polyester film as claimed in claim 1, which is used as a base film for magnetic recording.