JPH02170824A - Polyester film - Google Patents

Abstract

PURPOSE:To provide the subject film induced from a specific phenylindanedicarboxylic acid, having a specific photoelastic coefficient and excellent thermal properties, mechanical properties and optical properties and useful as an optical recording medium, etc. CONSTITUTION:The objective film has a photoelastic coefficient of <=1.2X10<-3>(mm<2>Xkgf) and is produced by reacting (A) a dibasic carboxylic acid and/or its ester-forming derivative containing >=5mol% of a phenylindanedicarboxylic acid of formula (R1-R3 are H, F, Br or <=4C alkyl) and/or its derivative with (B) a dihydroxy compound and/or its ester-forming derivative. The component A is preferably 1,1,3-trimethyl-3-phenylindane-4',5- dicarboxylic acid or its derivative.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to polyester films.

In particular, the present invention relates to a polyester film with excellent thermal, mechanical, and optical properties.

In this application, unless otherwise specified, the term "film" includes a thick material generally called a sheet.

[Prior Art] Conventionally, polymethyl methacrylate films and polycarbonate films have been used as support layers for optical recording media. However, although polymethyl methacrylate film has excellent optical properties, it has problems in that it is susceptible to dimensional changes due to humidity and has poor processability. Therefore, in order to suppress water absorption, hydrophobic monomers are copolymerized (for example, in JP-A-58-1
27754, JP-A-58-11515), mechanical strength and heat resistance are lowered, which is undesirable.

Polycarbonate films, on the other hand, are less susceptible to the effects of humidity and are easier to mold, but have the problem of being more susceptible to optical distortion. Therefore, it is generally necessary to lower the molecular weight, or to use methods such as copolymerization or blending (for example, JP-A-6O-215
051) and one using a specific bisphenol derivative (JP-A-63-35619), but good low birefringence is not necessarily obtained.

Therefore, it has been proposed that a polyester film should be used as the support layer (for example, in JP-A-57-1999).
208645). Polyester film is moisture resistant,
It is a film that is not inferior to polycarbonate film, has excellent moldability, and has transparency.

[Problems to be Solved by the Invention] However, even the optical recording medium using the polyester film as a support layer has the drawbacks of insufficient heat resistance and large optical distortion caused by mechanical deformation. are doing.

That is, when an optical recording medium is used, an external force such as bending, expansion/contraction, or compression is applied to the medium, thereby causing mechanical deformation of the medium. Furthermore, similar deformation occurs due to centrifugal force when a recording medium such as an optical disk is rotating at high speed. These deformations create optical distortions, or birefringence. This phenomenon is called photoelasticity. Since polarized laser light is normally used to read recorded signals, the photoelastic effect is a major factor in causing errors in reading recorded signals.

In addition, if the heat resistance deteriorates, the heat received during processing of the optical recording medium or when writing or reading recorded signals may cause
The medium is deformed and the photoelastic effect increases, leading to insufficient writing of recording signals and read errors.

[Means for Solving the Problems] The present invention has the following configuration in order to eliminate such drawbacks. That is, a polyester derived by reacting a difunctional carboxylic acid and/or its ester-forming derivative containing 5 mol% or more of phenylindanedicarboxylic acid and/or its derivative with a dihydroxy compound and/or its ester-forming derivative. It is a film, and is characterized by having a photoelastic coefficient of 1°2×10 −3 (mrrr/gf) or less.

The phenylindane dicarboxylic acid referred to in the present invention is represented by the following structural formula. (However, in the formula, R1 to R3 are hydrogen,
It is a group selected from fluorine, bromine, or an alkyl group having 4 or less carbon atoms. ) Particularly preferred among them are 1.
1. 3-trimethyl-3-phenylindan-4-5
-dicarboxylic acid, but of course, it may be one in which a less polar substituent such as an alkyl group is introduced at any position of the six-membered ring or indane ring. When the position of the carboxyl group is asymmetric as in this compound, the main chain of the copolymerized polyester tends to have a bent structure, improving quality and optical properties.

Moreover, since it has a rigid ring structure, the glass transition temperature of the copolymerized polyester increases and the heat resistance improves.

The amount of phenylindane dicarboxylic acid added is 5 mol% or more, preferably 15 mol% to 80 mol%, more preferably 30 mol% to 60 mol%. If the amount added is less than 5 mol %, no effect of the addition is observed. In addition,
If the amount added is too large, the film tends to become brittle and the processability of the film tends to decrease.

Examples of acid components other than phenylindane dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, naphthalene dicarboxylic acid, diphenoxyethane dicarboxylic acid, cyclohexane dicarboxylic acid, succinic acid, adipic acid, Cepatic acid, stilbene dicarboxylic acid,
diphenyldicarboxylic acid, diphenylthioetherdicarboxylic acid, diphenylketonedicarboxylic acid, and further p~
Examples include oxycarboxylic acids such as oxybenzoic acid, and among these, terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, naphthalene dicarboxylic acid, and diphenyldicarboxylic acid are particularly preferred in the case of the present invention.

In addition, as dihydroxy compound components, ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimetatool, 2,2-bis(
4-hydroxydiphenyl)propane, 2,2-bis(
4-hydroxyethoxyphenyl)propane, bis(4
-hydroxyphenyl) sulfone, polyethylene glycol, polytetramethylene glycol, diethylene glycol, neopentyl glycol, hydroquinone, cyclohexanediol, among which, in the case of the present invention, cyclohexane dimetatool, ethylene glycol, tetra Methylene glycol is preferred.

Furthermore, even if a polyfunctional compound having three or more functional groups such as trimellitic acid, trimesic acid, pyromellitic acid, glycerin, and pentaerythritol is copolymerized within a substantially linear range, , a polymer having a molecular weight of about 300 to 70,000, such as polyacrylate, polyacrylamide, polyacrylonitrile, polystyrene, polysiloxane, polymethyl methacrylate, polybutyl acrylate, and derivatives thereof, is graft-copolymerized to the side chain of the main chain of the polyester. You can leave it there.

Particularly preferred compounds of the present invention include 1. 1. 3-4-limethyl-3-phenylindan-4'', 5-dicarboxylic acid, diphenyl-2,2-dicarboxylic acid (diphenic acid), terephthalic acid, isophthalic acid, or naphthalene dicarboxylic acid, cyclohexane dimetatool as a dihydroxy compound, It is a polyester consisting of ethylene glycol and tetramethylene glycol.

The photoelastic coefficient of this polyester film is 1°2xio
-' (mrrf/kgf) or less, preferably,
0. 7 X 10-3 (0-3 (/kg f )
or less, more preferably 0.4×10
k gf) or less. Photoelastic coefficient is 1.2X10-3
(mrrf/kgf), optical distortion caused by mechanical deformation due to external force such as bending, expansion/contraction, or compression applied to the filter, that is, birefringence, increases, resulting in large distortions that cause reading errors in recorded signals. It becomes a factor.

The photoelastic coefficient of this polyester film is 1゜2
In order to achieve a value of 10"" (mrrr/kg f) or less, it is preferable to add a side chain to the polyester main chain, for example. By adding side chains, the difference between the polarizability in the direction of the molecular chain axis of the polyester and the polarizability in the direction perpendicular to it becomes smaller, and the inherent birefringence of the polymer decreases, making optical distortion less likely to occur. As a method for attaching side chains, for example, there is a method of using a high molecular weight monomer called a macromonomer, which has a dihydroxyl group or dicarboxyl group as a polymerizable functional group at the end. Its structure is as follows, where R includes styrene, styrene acrylonitrile, methyl methacrylate, butyl acrylate, etc. The molecular weight of the macromonomer is 300-6
000 is preferred. Side chains can be easily created by copolymerizing these macromonomers with other dicarboxylic acids and dihydroxy compounds.

In addition, the photoelastic coefficient is 1. 2 X 10-3 (0-3
(/kgf) or less, it is necessary to suppress the decrease in the polymer molecular weight and the orientation of the polymer during film formation. That is, the mechanical strength of the film decreases due to a decrease in molecular weight, and birefringence easily occurs when external force is applied. Furthermore, if there is directionality due to the orientation of the polymer, the photoelasticity will change depending on the direction of external force.

Therefore, the extrusion temperature of the polymer is preferably 10° C. to 50° C. higher than the melting point of the polymer, but it is more preferably as high as possible within a temperature range in which oxidative decomposition and thermal decomposition do not proceed rapidly. Furthermore, the film forming speed is
0.5m/min to 15m/min, preferably 1.5m
/min to 8m/min.

The birefringence of the film thus obtained is 1.8 x 10-4
or less, preferably 0.7X10-' or less, more preferably 0.3X10-' or less. As a result, the directionality of photoelasticity can be suppressed, and the photoelastic coefficient can be reduced to 1.2X10-3 (m rrr/kg f
) can be as follows.

Moreover, the maximum settling Rt of the polyester film is 0.1
μm or less, preferably 0.03 μm or less, and the average interval Sm of peaks is 20 μm or more, preferably 100 μm or less.
Must be larger than μm. If the above conditions are not met, the light will be scattered or interfered, resulting in a decrease in the intensity of the resulting light, which will cause errors when reading records.

Further, the glass transition temperature Tg of the polyester film is 80°C or higher, preferably 85°C or higher,
More preferably, the temperature is 90°C or higher.

If Tg is less than 80°C, the heat resistance will deteriorate, and the medium will be deformed by the heat received during processing of the optical recording medium or when writing and reading recorded signals, resulting in insufficient writing of recorded signals. or a read error occurs. In addition, the rigidity decreases, the mechanical strength decreases, and it becomes easier to overcome deformation.

The ultimate birefringence value Δno of the present polyester is 0.10 or less, preferably 0.07 or less, and more preferably 0.05 or less. This is because when Δno exceeds 0.10, optical anisotropy due to slight orientation of molecular chains tends to increase.

Further, the relative viscosity η of the present polyester is 14-70, preferably 20-60. η.

When the value decreases below 18, the mechanical strength of the film decreases,
It becomes easily distorted under load, and furthermore, if it is lower than 14, it becomes difficult to form a film. Moreover, when η exceeds 70, molecular chains are easily oriented during film forming, making it easy to cause birefringence.

Further, the thickness of the polyester film of the present invention is not particularly limited, but in the case of a stretched sheet, it is 6 to 360 μm.
In the case of a non-stretched sheet, a sheet having a thickness of about 250 to 2000 μm is preferably used.

Next, a method for manufacturing the polyester film of the present invention will be described. However, the method is not necessarily limited to this method.

A dicarboxylic acid or its ester derivative and a dihydroxy compound are mixed and reacted in a conventional manner to form a compound having an ester bond in the main chain, preferably a relative viscosity η of 14 to 14.
A polyester composition of 70 is obtained.

Once transesterification is necessary, a transesterification catalyst is used in addition to the polymerization catalyst. Of course, for practical purposes, coloring inhibitors, antioxidants, heat stabilizers, crystal nucleating agents, slipping agents, antiblocking agents, viscosity modifiers, antifoaming agents, clarifying agents, and the like may be added.

The thus obtained polyester containing 5 mol % or more of phenylindane dicarboxylic acid is melt-extruded and formed into a film at the extrusion temperature and film forming speed as described above, whereby the photoelastic coefficient is 1.2X 100-3. (%/kg
f) The following polyester film is obtained.

Further, the cast film may be stretched or oriented or heat treated as necessary.

Cast films may be used as is, but especially when used as optical recording media, the smoothness of the film surface,
In other words, the surface is required to have smoothness with a maximum roughness Rt of 1° Onm or less and an average peak spacing Sm of 20 μm or more. Therefore, it is preferable to cool the extruded molten film by pressing it with a cast drum and an attached cooling roll, or with a cast drum and an endless metal belt. In this case, the surface of the cast drum, attached cooling roll, or metal endless belt must be smooth, that is, the maximum roughness of the cooling body surface must be 0°IS or less, and it must be sufficiently smooth. By cooling both sides of the film, crystallization is prevented, and a film with excellent transparency and smoothness can be obtained.

As another method, the non-drum surface of a film cast on a smooth drum of 0.1 S or less may be pressed with an attached roll heated to a glass transition temperature or higher, and then rapidly cooled with a cooling roll.

Furthermore, the extruded molten polymer is held as a bank between two rolls with a smooth surface of 0°1 S or less,
It may be extruded from between rolls and calendered.

In addition, the extruded molten polymer is cast onto a smooth metal endless belt of 0°1S or less,
The endless belt may be heated and crimped with another smooth metallic endless belt, and then rapidly cooled.

The maximum roughness Rt of the surface obtained in this way was 1100
n or less, and the average peak spacing Sm is 20 μm or more. In order to prevent scratches on the film surface, during polymer extrusion or immediately after casting, olefins such as polypropylene, ethylene propylene copolymer polymethylpentene polymer, ethylene vinyl acetate polymer, etc. It may be laminated with a polymer or coated with a scratch-resistant layer.

When using the polyester film as an optical recording medium, optical discs, optical cards, and optical tapes can be considered. For example, in the case of an optical disc, an inorganic or organic optical recording medium is deposited on one side of the polyester film by vacuum deposition, sputtering, or the like. Optical recording media can be formed by spin-coding, and in optical cards, for example, a mixture of gelatin and silver particles is coated and treated on a polyethylene film with a vinyl chloride base attached to one side, and optical recording is performed. An optical recording medium can be formed by laminating the polyester film as a protective layer on top of the recording layer.

[Method for measuring physical properties] (1) Glass transition temperature Tg A 10-inch polyester film was set in a scanning calorimeter, and the temperature was raised at a rate of 20°C/min under a nitrogen stream until the baseline began to become eccentric. Use the average value of the temperature and the temperature that returns to the new baseline. Depending on the sample, if the baseline is not eccentric and an endothermic peak occurs, use the peak temperature.

(2) Relative viscosity η.

After cooling the polyester with dry ice, it is crushed in a crusher.
Grind to 0.00 mesh or less. 8 g of the mixture was put into 100 cc of hot O-chlorophenol at 150°C and dissolved in 1 to 2 minutes. The viscosity η of this polymer solution and the viscosity η of 0-chlorophenol. and are measured at 25°C, and the ratio is taken as the relative viscosity.

η" = η/η0 (3) Photoelastic coefficient For the photoelastic coefficient, the change in birefringence Δn when a load of 1 kgf is applied to a sample with a width of 10 mm is calculated, and Δn/S is taken as the photoelastic coefficient. Here, S is the stress applied to the sample.At this time, it is assumed that the thickness change during elastic minute deformation can be ignored.

The in-plane birefringence of the film was measured using the sodium D line (589
The sample film surface is placed perpendicular to the optical axis on a polarizing microscope equipped with crossed Nicols as a light source, and the optical path difference r caused by the birefringence of the sample is determined from the compensation value of the compensator, and r/d is It was assumed to be birefringence. Here d is the thickness of the sample film.

(4) Recording and reading error rate One side of this film is deposited with aluminum, and the non-deposited surface is irradiated with a laser beam perpendicularly. Laser light has an emission wavelength of 7
A linearly polarized semiconductor laser with a wavelength of 80 to 820 nm,
After passing through the beam slitter prism, the light passes through a quarter-wave plate, becomes circularly polarized light, and enters the polyester film perpendicularly. The reflected light passes through the quarter-wave plate again, becomes linearly polarized light, and enters the beam slitter prism again. In the beam slitter prism, only the linearly polarized light of the incident light passes through, and the re-incident light whose plane of polarization differs by 90 degrees from the incident light is reflected, reaches the optical signal detector, and its intensity is measured.

The intensity detected when a flat film is irradiated with laser light is I. Assuming that the intensity detected when a laser beam is irradiated onto a film that has been stapled and curved to a radius of curvature of 100 mm is 1, the reading error rate of recording is expressed as o - I .

(5) Ultimate birefringence value Δn.

The ultimate birefringence value is the anisotropy of the refractive index based on the maximum theoretically possible uniaxial orientation of the polymer. In the case of the present invention, as a simple method, a monofilament having a diameter of 250 μm is drawn at each stretching temperature, and the maximum value of the extrapolated stretching ratio of the birefringence value up to the point of breakage is adopted.

(6) Maximum roughness Rt, average spacing between peaks Smm Measured using a high-precision thin film step measuring instrument ET-10 manufactured by Kokai Research Institute. Rt is expressed as the distance between the largest peak and the deepest valley of the roughness curve, and Sm is expressed as the average interval between a pair of peaks and valleys that intersect with the center line of the roughness curve. The measurement conditions were as follows, and the average value of 20 measurements was taken as the value.

Contact needle tip radius: 0.5μm ◇Stylus load: 5■ ◇Measurement length: 1mm ◇Cutoff value: 0.08mm For details on parameter definitions, see, for example, the Nara 2nd Department "Measurement of Surface Roughness"・Evaluation Method” (General Technology Center, 1
983).

[Example] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Terephthalic acid (85 mol%) as dicarboxylic acid,
1,1,3-trimethyl-3-phenylindan-4'
, 5-dicarboxylic acid (15 mol%, manufactured by AMOCOO), a polyester consisting of ethylene glycol as a dihydroxy compound was heated at 290°C in an extruder by a conventional method.
cast from T-dyro gold onto a mirror drum,
A non-oriented film with a thickness of 400 μm was obtained.

Example 2 Terephthalic acid (50 mol%) as dicarboxylic acid,
1,1,3-trimethyl-3-phenylindan-4'
, 5-dicarboxylic acid (50 mol %) and a polyester consisting of ethylene glycol as a dihydroxy compound was cast in the same manner as in Example 1 to a thickness of 400 mol %.
A micrometer non-oriented film was obtained.

Comparative Example 1 As the dicarboxylic acid, terephthalic acid (97 mol%), 1
, 1.3-trimethyl-3-phenylindan-4',
Using 5-dicarboxylic acid (3 mol%), a polyester consisting of ethylene glycol as a dihydroxy compound was cast in the same manner as in Example 1 to a thickness of 400 μm.
A non-oriented film was obtained.

Comparative Example 2 An additive with an average particle size of 3 was added to the polymer used in Example 1.
A non-oriented film with a thickness of 400 μm was obtained in the same manner as in Example 1, except that 0.15 wt % of 0 nm SiO 2 was added.

Comparative Example 3 A polyester consisting of terephthalic acid as the dicarboxylic acid and ethylene glycol as the dihydroxy compound was cast in the same manner as in Example 1 to a thickness of 400 mm.
A micrometer non-oriented film was obtained.

Comparative Example 4 A polyester consisting of terephthalic acid (80 mol%) and isophthalic acid (20 mol%) as the dicarboxylic acid and cyclohexane dimetatool as the dihydroxy compound was cast in the same manner as in Example 1, and the thickness was 400
A micrometer non-oriented film was obtained.

When the properties of the films obtained in Example 1, Example 2, and Comparative Examples 1 to 4 were evaluated, the results were as shown in the table.

[Effects of the Invention] When an optical recording medium is used, mechanical deformation occurs in the medium by applying an external force such as bending, expansion/contraction, or compression to the medium. These deformations create optical distortions, or birefringence. By suppressing this photoelasticity, reading errors in recorded signals can be prevented.

Furthermore, it is stable against external environments such as heat, solvents, external forces, moisture, and light that are applied during manufacturing, storage, recording, and reproduction of optical recording media, making it a highly reliable optical recording medium.

Patent applicant Higashi Shikikai Co., Ltd.

Claims (4)

[Claims] (1) Phenylindane dicarboxylic acid represented by the following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, in the formula, R_1 to R_3 are groups selected from hydrogen, fluorine, bromine, or an alkyl group having 4 or less carbon atoms. ) and/or a difunctional carboxylic acid and/or its ester-forming derivative containing 5 mol% or more of its derivative, and a dihydroxy compound and/or its ester-forming derivative are reacted to form a polyester film, Photoelastic coefficient is 1.2×10^-^3 (mm^2/kgf)
A polyester film characterized by: (2) Phenylindane dicarboxylic acid and its derivatives are 1,1,3-trimethyl-3-phenylindan-4
2. The polyester film according to claim 1, which is made of '-,5-dicarboxylic acid and its derivatives. (3) The polyester film according to claim 1 or 2, which has a maximum surface roughness Rt of 100 nm or less and an average peak spacing Sm of 20 μm or more. (4) The polyester film according to claim 1 or 2, which has a glass transition temperature Tg of 80° C. or higher.