JPS6311326A - Film for optical recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a base film for an optical recording medium which does not produce deformation owing to curling and lowering of flatness, when an optical recording layer, a protecting layer and a reflecting layer are prepared by means of vapor-deposition or sputtering, and is fit for applications, by consisting of a specific biaxially oriented polyethylene terephthalate film. CONSTITUTION:An optical recording film consists of a biaxially oriented polyethylene terephthalate film whose heat shrinkage is 0-1% at 200 deg.C in its longitudinal direction and heat elongation is 0-2% at 200 deg.C in its axial direction. Polyethylene terephthalate is a homopolymer, a copolymer or a blend thereof whose molecular constitution comprises 80mol% or more polyethylene terephthalate and m.p. and intrinsic viscosity are 250 deg.C or more and 0.4-1.0 respectively. As the thickness of the film, 7-200mum is preferable. Heat setting under a condition of being unstretched in the axial direction is carried out at 180-210 deg.C. Out of this range, it is difficult to obtain a film having good thermal characteristics.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical recording medium, and more particularly, to a film for an optical recording medium used for optical cards, optical floppies, optical tapes, etc., and a method for manufacturing the same. It is.

[Prior Art] In recent years, optical recording systems using laser light have been developed, and substrate films such as polycarbonate resin, polymethyl methacrylic acid resin, and the like have been put into practical use. These resins are mainly used in the form of disks, which are hard disks that complicate focusing of the drive, thick disk bases, thick storage cassettes, and tapes. However, there is a need for a soft type optical recording medium that can be read and written. As soft type magnetic recording media, those using known polyethylene terephthalate film,
For example, as described in JP-A-59-195322, a laminate of a polyethylene terephthalate film and a polypyrene film is known.

[Problems to be solved by the invention] However, soft-type optical recording media using these base films have thicker protective layers than magnetic recording media, so when the protective layer is attached, the base film may be damaged. It has the disadvantages of curling, curling, and poor flatness.

In view of the drawbacks of the prior art, the present invention aims to provide an optical recording medium that can withstand use and that does not cause deformation due to curling or deterioration of flatness even when an optical recording layer, a protective layer, or an anti-q dimension @ is vapor-deposited or sputtered. The purpose is to provide a base film.

[Means for Solving the Problems] The present invention provides a film that is heated to 200°C (longitudinal direction (MD)).
) has a heat shrinkage rate of 0 to 1%, and a heat elongation rate in the width direction (King D) of the film at 200°C is 0 to 2%2.
The present invention relates to a film for optical recording media characterized by being made of an axially oriented polyethylene terephthalate film, and a method for producing the same.

The optical recording medium used in the present invention is one that reacts reversibly or irreversibly with a recording layer that reacts with the light applied to the film by a light source such as a laser beam, and the change in state can be read again with light. means.

To the polyethylene terephthalate 1 according to the present invention,
It is a polymer, copolymer, or mixture in which 80 mol% or more of the molecular structure consists of units of ethylene terephthalate, and the melting point of the polymer is -1x, preferably 250°C or higher.
A temperature of 55°C or higher is desirable.

Further, the preferable intrinsic viscosity of the polymer is 0.4 to 1°0, more preferably 0.55 to 0.8. In addition,
The polymer may contain stabilizers such as phosphoric acid, phosphorous acid and their esters, known lubricants such as titanium oxide, particulate silica, lithium carbonate, and the like.

The 2111-oriented polyethylene terephthalate film of the present invention is obtained by melt-extruding polyethylene terephthalate (i) to (g) and biaxially stretching and orientating it.

The film thickness of the biaxially oriented polyethylene terephthalate film of the present invention is preferably 7 to 200 μm, more preferably 10 to 80 μm.

If it is smaller than this range, it will not have sufficient stiffness and will not be suitable as a support film for optical recording media. Moreover, if it is larger than this range, the advantages of a soft type optical recording medium cannot be utilized.

Furthermore, the film adhesion tarpsion value of the biaxially oriented polyethylene terephthalate 1 of the present invention is not particularly limited, but is preferably lower.゛The film for optical recording medium of the present invention is
The heat shrinkage rate at 200°C is 1%, preferably 0.01 to 0.7%, and the heat elongation rate in the width direction of the film (direction perpendicular to the longitudinal direction, TD> is 0
-2%, preferably 1-1.5%.

If it is outside this range, the curl may be large or the plane surface ゛[)1 may deteriorate, making it difficult to put it to practical use.

Moreover, the tension heat setting of the 2411 stretched film of the present invention is as follows:
For example, this can be done by passing the film through an oven using a so-called tenter method in which both ends of the film are held between clips. Heat fixation without tension in the width direction can be carried out by gripping both ends of the film and passing it through a heated tube or heated engine under tension in the direction of travel. Heat setting without tension in the width direction is performed at 180 to 210°C. Outside this range, it is difficult to obtain a film having the above-mentioned thermal properties.

Note that at this time, the direction of movement may be relaxed within a range of several percent.

Next, a method for producing a film for optical recording medium of the present invention will be explained, but the present invention is not limited thereto. First, polyethylene terephthalate chips are fed into an extruder, melted and extruded at 280° C., discharged from a T-type nozzle, rapidly cooled and solidified, and then a substantially non-oriented, unstretched sheet is produced. This sheet is heated for 2 to 6 minutes at a temperature of 80 to 100℃.
Stretched in the longitudinal direction, preferably 2.5 to 4.5 times, and then stretched 2 to 4 times, preferably 2.5 to 4.5 times, at a temperature of 90 to 120°C.
3.5 times sequential biaxial stretching. Alternatively, the film is biaxially stretched at 80 to 100° C. in both longitudinal and transverse directions by 2 to 4 times, preferably 2.5 to 3.5 times. The film thus obtained was
~240°C, more preferably in the range of 190-215°C, heat set for 2-8 seconds under tension in the width direction, then heat-set in the range of 180-210'C for 10-50 seconds without tension in the width direction. Heat fixation is performed for seconds, preferably 20 to 10 seconds to obtain a biaxially oriented polyethylene terephthalate film. Further, the heat setting may be performed by tensioning and heat setting in the width direction, cutting the edges and winding the film once, and then heat setting without tension in the width direction.

An optical recording layer such as gadolinium, terbinium, iron, ]pal 1 is added to the film for optical recording medium thus obtained.
A known material such as a rewritable magneto-optical material such as ~, a mixture of bismuth, antimony, and selenium, a photoreactive layer made of an element from the group of cesium and tellurium, or a photoreactive layer made of an organic compound is deposited or Sputter.

Further, silicon oxide, silicon dioxide, or the like is deposited or sputtered as a protective layer on the optical recording layer to complete an optical recording medium.

The vapor deposition or sputtering conditions were a pressure of 10-2. ．．
1Q-6 orr and a speed of 50 to 6000 A/min are preferable. Moreover, the thickness of the protective layer is preferably 600 to 3000 people.

[Measurement method and evaluation method] The measurement method of the characteristic value and the evaluation method of the effect of the present invention are as follows.

(1) Heat shrinkage rate and heat elongation rate A sample with a trial length of 50 mm and a trial width of 5 mm is set in an oven, the original shape Lo (μm) is determined, and the constant speed (5°
Dimensional change (Δ]-) (μm)
is electrically read and recorded using a differential transformer. 200
Determine the dimensional change at °C, and calculate the thermal shrinkage rate and thermal elongation rate using the following formula.

S=(Δl/l o ) xloo (%) When the sample shrinks, it is expressed as a thermal shrinkage rate by a minus (-), and when it expands, it is expressed as a thermal elongation rate by a plus (+).

(2) Curl height After depositing or sputtering a recording layer and a protective layer on the base film, the film is pounded onto a disk having a diameter of 9 Qmm to form a disk. Place the disc on a glass flat plate and check the height of the end of the disc from the glass flat plate. Regarding the curl height, those that are qualitatively practical are represented by ○, those that require further improvement are represented by Δ, and those that cannot be used are represented by ×.

(3) Flatness Place the disk made in (2) on a flat glass plate]
, flatness is determined from waving, etc.

[Example] Example 1 The present invention will be explained based on examples.

Chips of polyethylene terephthalate 1 to 1 with a melting point of 265° C. and an intrinsic viscosity of 0.65 were fed to an extruder, melted and extruded at 280° C., discharged from a T-shaped nozzle, and rapidly solidified.
A substantially non-oriented unstretched sheet 1 was prepared. This sheet is stretched 3.0 times in the machine direction at 90°C, and then stretched 3.0 times in the transverse direction at 95°C. Tighten the width direction, 2
Heat set at 00℃ for 5 seconds, then 200℃ without tension in the width direction.
Heat set at ℃ for 25 seconds.

A biaxially oriented polyethylene terephthalate film was produced. The film thickness was 75 μm. Further, the heat shrinkage rate and heat elongation rate are shown in Table 1.

The thus obtained film was coated with Chirubini' as a recording layer.
Kumu, iron,] bapar 5 x 10-3 tons orr pressure, 2
It steamed 2000 people at a rate of 00 people/minute. Optical recording bodies were produced in this way, and the curl height and flatness were judged (Table 1).

Comparative Example 1 Using the same raw materials as in Example 1, the film was similarly stretched 3 times in the longitudinal direction and 3 times in the transverse direction. Next, tighten the width direction and heat to 200℃.
Heat fixation was performed for 5 seconds.

The film thickness was 75 μm.

A recording layer and a protective layer were sputtered and vapor deposited under the same conditions as in Example 1 to produce an optical recording medium.

Comparative Example 2 Using the same raw materials as in Example 1, the film was similarly stretched 3 times in the longitudinal direction and 3 times in the transverse direction. Next, tighten the width direction and heat to 200℃.
Heat setting was performed for 5 seconds at 170° C. for 160 minutes without tension. The film thickness was 75 μm.

A recording layer and a protective layer were sputtered and vapor-deposited using the same strip A'1 as in Example 1 to produce an optical recording medium.

Table 1 shows the results of the thermal expansion and contraction ratio of the film for optical recording material and the curl height of the optical recording material, and the curl height of the films other than Example 1 was poor and could not be put to practical use.

Table 1 "Effects of the Invention J The present invention limits the heat shrinkage rate and heat elongation rate at 200°C of the film for optical recording medium to a specific range, so that the curling that occurs during vapor deposition or sputtering of the recording layer, protective layer, etc. , deterioration of flatness can be prevented.

Claims (2)

[Claims] (1) Biaxially oriented polyethylene terephthalate having a heat shrinkage rate of 0 to 1% in the longitudinal direction (MD) of the film at 200°C and a heat elongation rate of 0 to 2% in the transverse direction (TD) of the film at 200°C. A film for optical recording medium, characterized in that it consists of a film. (2) Biaxially stretched polyethylene terephthalate film is heated to 180 to 21
A method for producing a film for optical recording material, which comprises reheat-setting at a temperature of 0°C.