JPH06274935A - Laminated polyester film for optical tape - Google Patents

Abstract

PURPOSE:To obtain an optical tape having excellent optical recording characteristics and reproducing characteristics. CONSTITUTION:This laminated film is produced by forming an active ray-curing layer having >H surface hardness on the one surface of a polyester film. The center line average roughness (RaA) of the surface of the active ray-curing layer (surface A) is <=0.005mum, and the center line average surface roughness (RaB) of the opposite side (surface B) is 0.005-0.3mum. The laminated film has <=30% transmittance of light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film used as a base material for an optical tape which records and reproduces information by irradiation with light.

[0002]

2. Description of the Related Art In recent years, various information recording / reproducing systems have been developed as the density of information recording and the number of digital recordings have increased. Among these methods, a method using an optical recording / reproducing system is considered to be particularly effective. For example, optical tapes, such as those in which a metal film of Te-As-Se is provided on a plastic film as a base material have been reported, but the base material has advantages and disadvantages, and good ones can be obtained in practical use. There wasn't.

For example, when an optical tape is manufactured using a conventional flat biaxially stretched polyester film as a base material,
There is a problem that the slipperiness of the film is poor and the workability is poor, defects such as scratches are likely to occur during the manufacturing process, and the optical recording characteristics after forming the optical tape are adversely affected. When information is recorded on the optical tape, for example, laser light emitted from the optical head portion destroys the recording layer by heat, forming hole-shaped recording pits. The record information data thus supplied to the optical head is recorded as a pit on the optical tape. Further, at the time of reproduction, a laser beam at a level lower than that at the time of recording (a level at which the recording layer is not destroyed) is irradiated along the recording track, and pit information is detected by the difference in the reflected light level of the irradiated laser light. Therefore, in order to detect the difference in reflected light level by the pits during playback,
It is necessary that the substrate has high light transmittance or light absorption.

However, the conventional base material of the optical tape has insufficient transparency or absorption of the laser light, and the laser light applied to the recording pit is
Alternatively, a part of the light is reflected on the back surface or the like, and this is detected as reflected light, so that there is a drawback that the S / N in the reproduced signal is deteriorated.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above-mentioned problems, and as a result, found that a specific laminated polyester film has excellent properties as a base material for an optical tape. It came to completion. That is, the gist of the present invention, on one side of the polyester film,
A laminated film provided with an active energy ray-cured layer having a surface hardness of H or more, the center line average roughness (Ra ^A ) of the active energy ray-cured layer surface (A side) being 0.005 μm.
Hereinafter, the center line average roughness (Ra) of the exposed surface (B surface) on the opposite side will be described.
^B ) is in the range of 0.005 to 0.3 μm, and the light transmittance of the laminated film is 30% or less.

The present invention will be described in detail below. The polyester referred to in the present invention, terephthalic acid, isophthalic acid,
An aromatic dicarboxylic acid such as naphthalene-2,6-dicarboxylic acid or an ester thereof, ethylene glycol,
It is a polymer that can be obtained by polycondensation with glycols such as diethylene glycol, tetramethylene glycol, neopentyl glycol and the like.

This polyester can be obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol, or by subjecting an aromatic dicarboxylic acid dialkyl ester and a glycol to a transesterification reaction and then polycondensing, or an aromatic dicarboxylic acid. It can also be obtained by a method such as polycondensing a diglycol ester of an acid. Typical examples of such polymers include polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate. The polymer may be a non-copolymerized homopolymer and is a copolyester such that less than 15 mol% of the dicarboxylic acid component is the non-aromatic dicarboxylic acid component and / or the diol component of the diol. May be.

Further, it may be a polymer blend of the polyester and another polymer. Examples of other polymers that can be blended include polyamide, polyolefin, and other polyesters (including polycarbonate). Further, the polyester may contain additives such as a stabilizer, a colorant, an antioxidant and an antifoaming agent, if necessary.

In the present invention, the F5 value in the longitudinal direction of the polyester film is preferably 8 kg / mm ² or more,
g / mm ² is more preferable, and 10 kg / mm ² or more is particularly preferable. If the F5 value in the longitudinal direction of the polyester film is less than 8 kg / mm ² , workability in producing an optical tape may be poor, or the properties as an optical tape may be poor.

In addition, the longitudinal direction of the polyester film 1
The heat absorption rate after 30 minutes at 00 ° C is preferably 5% or less,
3% or less is more preferable, and 2% or less is particularly preferable.
When the heat shrinkage ratio exceeds 5%, the heat resistance tends to be insufficient, which may adversely affect the characteristics of the optical tape. In the present invention, the active energy ray-curable layer is laminated to flatten the surface of the polyester film on which the recording layer is provided and to prevent scratches and the like.
As a component constituting the active energy ray-curable layer in the present invention, a composition such as an unsaturated polyester resin system, an acrylic system, an addition polymerization system, a thiol / acrylic hybrid system, a cationic polymerization system or a hybrid system of cationic polymerization and radical polymerization is used. The acrylic composition is preferable in terms of curability, flexibility, heat resistance, durability and the like.

The acrylic compound forming the active energy ray-curable layer contains an acrylic oligomer as an active energy ray polymerization component and a reactive diluent, and if necessary, a photopolymerization initiator, a photosensitizer, It may contain a quality agent and the like. Examples of the acrylic oligomer include oligomers in which a reactive acryloyl group or methacryloyl group is bonded to an acrylic resin skeleton, and polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) Acrylate, silicone (meth) acrylate,
Examples thereof include oligomers such as polybutadiene (meth) acrylate. Furthermore, an oligomer in which a reactive acryloyl group or a methacryloyl group is bonded to a rigid skeleton such as isocyanuric acid or cyclic phosphazene can be mentioned.

The reactive diluent has a group that reacts with the acrylic oligomer, plays a role of a solvent in the coating step, and serves as a coating film component. Specific examples of the reactive diluent include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate. ) Acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, (meth) acryloyloxypropyl trimethoxysilane, (meth) Examples thereof include acryloyloxypropyltriethoxysilane.

Examples of the photopolymerization initiator include 2,2-
Ethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, 2-chlorothioxanthone, anthraquinone, phenyl disulfide, 2-Methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone and the like can be mentioned. These are used alone,
You may use it in combination.

Examples of the photosensitizer include tertiary amines such as triethylamine, triethanolamine and 2-dimethylaminoethanol, arylphosphines such as triphenylphosphine, and thioethers such as β-thiodiglycol. To be These may be used alone or in combination. As the modifier, coating property improver, antifoaming agent, thickener, lubricant, organic polymer,
Examples thereof include stabilizers and surfactants, which are appropriately blended as the composition of the active energy ray-cured layer within a range that does not hinder the reaction by active energy rays.

In the present invention, the composition may be applied by an appropriate means and irradiated with active energy rays to crosslink and cure. As the active energy rays, ultraviolet rays, visible rays, electron rays, α rays, β rays, and γ rays can be used, but ultraviolet rays and electron rays are preferable. Irradiation with active energy rays is usually performed from the cured layer side, but in order to enhance adhesion with the film, a reflection plate capable of reflecting active energy rays is provided on the film surface side, or active energy rays are irradiated from the film surface side. It may be irradiated.

As the thickness of the active energy ray-cured layer,
The range of 0.1 to 20 μm is preferable, and 0.5 to 1 is preferable.
It is in the range of 0 μm, and more preferably in the range of 1 to 7 μm. If the thickness of the cured layer is less than 0.1 μm, it may be insufficient to flatten the film surface. When the thickness is more than 20 μm, the curing shrinkage of the cured layer becomes large, and the film may curl to the cured layer side.

The surface hardness of the active energy ray-cured layer is required to have a pencil hardness of H or higher, preferably 2H or higher, in order to prevent damage to the cured layer. In the present invention, in order to improve the adhesion of the active energy ray-cured layer to the polyester film, the film may be subjected to a chemical treatment or an electric discharge treatment, preferably an easy-adhesion layer between the film and the active energy ray-cured layer. Should be provided. Further, an intermediate layer such as an antistatic layer may be provided if necessary.

Examples of the method for providing such an easily adhesive layer or another intermediate layer include a coextrusion method and a coating method. In the present invention, a method of laminating a thin film layer containing fine particles by a coextrusion method may be used so that the center line average roughness (Ra ^B ) of the B surface of the polyester film is in the range of 0.005 to 0.3 μm. A method of applying and forming a coating liquid containing fine particles and a binder resin on the B surface during or after forming the polyester film can also be employed.

The fine particles used for this purpose include siloid, colloidal silica, titanium oxide, calcium carbonate,
Examples thereof include inorganic particles such as kaolin and aluminum oxide, crosslinked polystyrene, crosslinked acryl, crosslinked benzoguanamine, crosslinked melamine, organic particles such as epoxy, and carbon black. The average particle size of these fine particles is 0.0
The amount is preferably in the range of 1 to 3 μm, more preferably 0.05 to 1 μm, and the addition amount can be selected from the range of 0.1 to 10% in terms of the weight fraction of the particle-containing layer forming the B side. Also,
The shape of the particles may be spherical, ellipsoidal or flat.

Further, in addition to the method of imparting runnability to the surface B with only these fine particles, a lubricant such as an anionic surfactant, a cationic surfactant, a fluorinated surfactant and a wax is added to the coating solution. Or a coating solution containing a water-soluble polymer such as cellulose, gelatin, polyacrylic acid, or the like, which is a compound characterized by phase separation in the layer and stretching properties, as a protrusion-forming agent. A method of forming projections by stretching after coating in the film forming process can also be mentioned.

In the present invention, the light transmittance (T; measurement wavelength 830 nm) of the laminated film is 30% or less, preferably 20% or less. Examples of means for satisfying the light transmittance (T) include the following methods. (1) A method of incorporating a light absorbing substance into a polyester film. (2) A method of providing a layer containing a light absorbing substance between the polyester film and the active energy ray-cured layer. (3) A method of incorporating a light absorbing substance in the active energy ray-cured layer. (4) A method of providing a layer containing a light absorbing substance on the surface of the polyester film opposite to the surface on which the active energy ray-cured layer is provided.

These methods may be used alone or in combination, but a method of incorporating a light absorbing substance in the active energy ray-cured layer is particularly preferable. Regarding the method of incorporating the light absorbing substance in the active energy ray-curable layer, the light absorbing substance is usually contained in the composition of the active energy ray-curable layer in an amount of 0.01 to 30% by weight, preferably 0.1 to 10% by weight. weight%
In the range of 1., the composition may be applied by an appropriate means, and irradiated with active energy rays to crosslink and cure.

Examples of the light absorbing substance include anthraquinone compounds, aminium compounds, polymethine compounds, diimonium compounds, cyanine compounds, squarylium compounds, naphthoquinone compounds, quinoneimine compounds, quinonediimine compounds, pyrylium compounds. Examples thereof include compounds, triphenylmethane compounds, croconic methine compounds, tetrahydrocholine compounds, azurenium compounds, phthalocyanine compounds, and dithiol metal complex compounds. These may be used alone or in combination.

The thickness of the film of the present invention is 5 to 3
00 μm is preferable, and 10 to 100 μm is more preferable. In the present invention, the surface of the polyester film on which the recording is provided is preferably flat, and by laminating an active energy ray-cured layer described later, the center line average roughness of the active energy ray-cured layer surface (A side) ( Ra ^A )
To 0.005 μm or less, preferably 0.003 μm
Hereafter, it is flattened to 0.002 μm or less. If Ra ^A exceeds 0.005 μm, the optical recording characteristics of the optical tape are deteriorated, which is not preferable.

In the present invention, the center line average roughness (Ra) of the surface (B surface) of the polyester film on which the recording layer is provided is determined.
^B ) is 0.005 μm to 0.3 μm, preferably 0.007 to 0.05 μm, more preferably 0.00
It is in the range of 8 to 0.02 μm. Such Ra ^B is 0.
When it is less than 005 μm, the slipperiness of the film is inferior, the workability in producing an optical tape is inferior, and the properties as an optical tape are inferior. On the other hand, when Ra ^B exceeds 0.3 μm, a so-called set-off phenomenon in which the roughness of the B side is transferred to the recording layer surface becomes remarkable and the optical recording characteristics of the optical tape deteriorate. A recording layer is provided on the active energy ray-cured layer of the thus-obtained laminated polyester film for optical tape, and an optical tape is produced. In the present invention, the recording layer is not particularly limited, but examples of materials used for the recording layer include Te, Zn, In, Sn, Zr, Al,
Examples thereof include metals such as Ti, Cu, Au and Pt: semimetals such as Bi, As and Sb: semiconductors such as Ge and Si: and combinations thereof.

Compounds such as sulfides, oxides, borides, silicon compounds, carbides and nitrides of these metals, semimetals or semiconductors: and mixtures of these compounds with metals can also be used in the recording layer. it can. The recording layer is formed by a method such as vapor deposition, sputtering, or ion plating of the above materials. The recording layer may be a single layer or multiple layers.

[0027]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples without departing from the gist thereof. The evaluation methods in the examples are as follows. In Examples and Comparative Examples, "part" means "part by weight".

(1) Center Line Average Roughness (Ra) It was determined as follows using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory Ltd. That is, the reference length L (2.55 mm) from the film section curve in the direction of the center line
The part of is drawn out, and the center line of this extracted part is the x-axis,
When the roughness curve y = f (x) is represented with the direction of the longitudinal magnification as the y-axis, the value given by the following formula is represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portions obtained from the 10 section curves obtained from the surface of the sample film. The tip radius of the stylus was 2 μm, the load was 30 mmg, and the cutoff value was 0.0.
It was 8 mm. Ra = (1 / L) ∫ L 0 | f (x) | dx (2) Tensile Test (F ₅ value) Co. Intesco Ltd. tensile tester in Tesco model 200
A sample film having a length of 50 mm and a width of 15 mm was pulled at a speed of 50 mm / min in a room controlled at a temperature of 23 ° C. and a humidity of 50% RH by using Type 1, and the strength at 5% extension was defined as F ₅ value. .

(3) Heat Shrinkage Using a hot air circulation furnace manufactured by Tabai Seisakusho, sample film 10
Free-end heat treatment was performed at 0 ° C. for 30 minutes, and the dimensional change in the machine direction before and after the treatment was expressed in%. (4) Light transmittance The light transmittance T (%) at a wavelength of 830 nm was measured using a spectrophotometer (UV-3100S type) manufactured by Shimadzu Corporation. (5) Surface hardness According to JIS K5400 (1990), pencils of various hardnesses are applied to the hardened layer at an angle of 45 °, scratches are given under a load of 1 kg, and the hardness of the pencil when scratches occur is the hardness of the hardened layer. And

Example 1 In the presence of 100 parts of bis- (β-hydroxyethyl) terephthalate oligomer, 87 parts of terephthalic acid and 42 parts of ethylene glycol were reacted at 260 ° C. under atmospheric pressure to effect esterification, and the esterification ratio was 97. % Polyester oligomer was obtained. Then, ethylene glycol slurry of spherical silica having an average particle size of 0.27 μm was added so as to be 2% by weight with respect to the polyester, and then 0.014 parts of ethyl acid phosphate, 0.022 part of antimony trioxide and acetic acid were added. 0.086 parts of magnesium was added and a polycondensation reaction was performed to obtain a polyester having an intrinsic viscosity of 0.65. After drying the obtained polyester, 290
It was extruded from the die of an extruder at a temperature of ° C and cast on a cooling drum while also using the electrostatic contact method to obtain an amorphous polyester sheet having a thickness of 920 µm. The sheet above 95 ℃
After stretching 3.5 times in the machine direction in the machine direction, a coating solution having the following composition is applied to both surfaces of the polyester sheet, stretched 3.5 times in the machine direction at 110 ° C., heat treated at 230 ° C., and then machined in the machine direction. A relaxation treatment was performed to obtain a biaxially stretched polyester film having a coating layer thickness of 0.06 μm and a base polyester film thickness of 75 μm.

[Coating Liquid Composition] Polyurethane Water Dispersion A
(Dainippon Ink and Chemicals Co., Ltd. Hydran AP-4
0) 75 parts; Polyester aqueous dispersion B (Finetex ES-670 manufactured by Dainippon Ink and Chemicals, Inc.) 20
Part: 5 parts of silica sol having an average particle size of 0.07 μm, the thickness of the film obtained after curing the following composition was 4 μm on one side of the obtained film.
And a high-pressure mercury lamp having an energy of 120 w / cm, and irradiated with an irradiation distance of 150 mm for about 15 seconds to provide an active energy ray-cured layer containing a light absorbing substance.

[Active energy ray curing layer composition] 35 parts of dipentaerythritol hexaacrylate; 35 parts of tetrafunctional urethane acrylate; 25 parts of bisphenol A type epoxy acrylate; 5 parts of 1-hydroxycyclohexyl phenyl ketone; light absorbing substance (polymethine 2 parts of IR-820B manufactured by Nippon Kayaku Co., Ltd.

The centerline average roughness (Ra) of the active energy ray-cured layer surface (A surface) of the obtained laminated polyester film was measured.
^A ) was 0.002 μm, and the center line average roughness (Ra ^B ) of the opposite surface ( ^B ) was 0.01 μm. The surface hardness of the active energy ray-cured layer was 3H. The light transmittance (T) of the laminated polyester film is 1
It was 8%. On the active energy ray-cured layer of the obtained film, a recording layer having a thickness of 540Å made of In300Å and GeS240Å was formed by a sputtering method to prepare an optical tape. The workability in producing the optical tape was good, and the active energy ray-cured layer had no surface defects such as scratches. This optical tape showed excellent optical recording characteristics during recording and reproduction. The laser light applied to the recording layer is absorbed by the laminated polyester film, and the reflected light of the light applied to the recording pits is
The detected signal was hardly detected, the noise component was suppressed in the detected signal, and the reproduction characteristics were particularly excellent.

Example 2 A laminated polyester film was obtained in the same manner as in Example 1 except that the active energy ray-curable layer was changed to the following composition and coated so that the thickness after curing was 3 μm. The center line average roughness (Ra ^A ) of the active energy ray cured layer surface (A surface) of the obtained laminated polyester film was 0.002 μm, and the center line average roughness (Ra ^B ) of the opposite surface (B surface) was It was 0.01 μm. The surface hardness of the active energy ray-cured layer was 2H, and the light transmittance (T) of the laminated polyester film was 10%. 1 electron beam with acceleration voltage 18kV and beam current 36mA
Irradiation was performed at an irradiation dose of 0 mrad to provide an active energy ray and a cured layer to obtain a laminated polyester film. [Active energy ray-curable layer composition] Dipentaerythritol triacrylate 50 parts; Tetrafunctional urethane acrylate 45 parts; 2-Methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone 5 parts; Light absorption Substance (Polymethine compound manufactured by Nippon Kayaku Co., Ltd. I
R-820B) 4 parts

Example 2 In Example 1, the active energy ray-curable layer was changed to the following composition and applied so that the thickness after curing would be 3 μm, and 10 electron beams with an acceleration voltage of 180 kV and a beam current of 36 mA were used.
The active energy ray-cured layer was provided by irradiating with a dose of Mrad to obtain a laminated polyester film. [Active energy ray curable layer composition] 50 parts of dipentaerythritol hexaacrylate; 50 parts of tetrafunctional urethane acrylate; 3 parts of light absorbing substance (IR-820B manufactured by Nippon Kayaku Co., Ltd., which is a polymethine compound)

Comparative Example 1 A laminated polyester film was obtained in the same manner as in Example 1 except that the active energy ray-cured layer was not provided. When I made an optical tape using this film,
This optical tape had a large surface roughness on the recording layer surface and was inferior in optical recording characteristics.

Comparative Example 2 A laminated polyester film was obtained in the same manner as in Example 1, except that the active energy ray-curable layer was changed to the following composition and coated so that the thickness after curing was 4 μm. When I made an optical tape using this film,
A part of the light applied to the recording pit was reflected on the front surface or the back surface of the polyester film, and the reproduction characteristics were inferior. [Active energy ray-curable layer composition] 35 parts of dipentaerythritol hexaacrylate; 35 parts of tetrafunctional urethane acrylate; 25 parts of bisphenol A type epoxy acrylate; 5 parts of 1-hydroxycyclohexyl phenyl ketone

Comparative Example 3 A laminated polyester film was obtained in the same manner as in Example 1 except that the following polyester resin was provided in a thickness of 4 μm instead of providing the active energy ray-cured layer. When an optical tape was prepared using this film, many scratches were formed on the polyester resin layer, and the optical recording characteristics of the prepared optical tape were inferior. [Polyester resin composition] 100 parts of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.); light absorbing substance (polymethine compound IR- manufactured by Nippon Kayaku Co., Ltd.)
820B) The results obtained in two or more parts are collectively shown in Table 1 below.

[0039]

[Table 1] ─────────────────────────────────── Ra ^A Ra ^B T Surface F ₅ Shrinkage optics Record (μm) (μm) (%) Hardness (kg / mm ² ) (%) Characteristic ───────────────────────────── ────── Example 1 0.002 0.01 20 3H 13 1.4 Excellent Example 2 0.003 0.01 15 15 2H 13 1.4 Excellent Example 3 0.002 0.01 16 3H 13 1.4 Excellent Comparative Example 1 0.01 0.01 86 F 13 1.4 Inferior Comparative Example 2 0.002 0.01 86 3H 13 1.4 Inferior Comparative Example 3 0.002 0.01 18 HB 13 1. 4 Inferior ────────────────────────────────────

[0040]

Industrial Applicability According to the laminated polyester film of the present invention, an optical tape excellent in optical recording characteristics, particularly reproduction characteristics can be obtained, and its industrial value is high.

Claims (1)

[Claims] 1. A laminated film comprising an active energy ray-cured layer having a surface hardness of H or more on one surface of a polyester film, the center line average roughness of the active energy ray-cured layer surface (A side). (Ra ^A ) is 0.005 μm
Hereinafter, the center line average roughness (Ra) of the exposed surface (B surface) on the opposite side will be described.
^B ) is in the range of 0.005 to 0.3 μm, and the light transmittance of the laminated film is 30% or less, wherein the laminated polyester film for optical tapes.