JPH0224830A - Sheet for magnetic recording and production thereof - Google Patents

Abstract

PURPOSE:To allow the production of the above sheet at one time by co-extrusion and to allow the easy participation of general light printers by constituting a base to be used for magnetic cards, cash cards, etc., of a biaxially oriented polyester sheet having a two-layered laminated structure and finely dispersing and incorporating >=10wt.% ferromagnetic material powder into one of these layers. CONSTITUTION:The melt of polyethylene terephthalate having 0.46 intrinsic viscosity is introduced to a twin-screw extruder and CO-gammaFe2O3 having 450Oe MC, 0.9mum average grain size and 23m<2>/g specific surface area is dispersed and mixed therewith to form a master granular material [I] having 16.3wt.% concn. Titanium oxide having 0.3mum average grain size is incorporated at 24wt.% into the polyethylene terephthalate having 0.37 intrinsic viscosity by the similar method to form a white master polymer [II]. Ordinary polyethylene terephthalate polymer having 0.67 intrinsic viscosity is thereafter intimately mixed with the granular material [I] and is so diluted that the concn. of the magnetic powder attains 10.7wt.% concn. Titanium oxide is mixed similarly with the polymer [II] to 17wt.% concn. and these materials are superposed on each other.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording sheet and a method for manufacturing the same, and more particularly to a highly durable magnetic card capable of recording electromagnetic signals, such as a prepaid card, a credit card card, etc. to.

This invention relates to a magnetic recording sheet having a two-layer laminated structure useful for cash cards and securities, and a method for manufacturing the same.

[Prior Art] In recent years, the growth of cards has been remarkable, and magnetic cards are the main type of cards.

This type of card is generally put into practical use in the form of reading the card punch and embossed characters, as well as the signals stored in the formed magnetic layer (RI & Qi stripe transfer, full magnetic coating) and the PIN number. 0 For example, credit cards generally have a magnetic stripe on the back of a PVC board with an embossed pattern, while telephone cards and the like have multiple layers of magnetic films on a white polyester film. They are manufactured using a method in which the magnetic film is coated on the plastic material and then printed on the opposite side to finish the product.Although there are differences in the method of coating on the plastic material and stamping transfer, the common part of both is that the magnetic film is formed. The point is that the necessary signals can be read by magnetically recording them.

[Problems to be Solved by the Invention] These magnetic card products require a complete division of labor between the side that provides the card base and the processing specialist that applies aesthetic printing to the base and forms the magnetic layer. It is a fact that this is usually done in the form of a ``transportation fee'', which increases distribution expenses and causes an increase in costs. In addition, in the case of credit cards with magnetic stripes, there was a further division of labor between specialized magnetic stripe tape manufacturers and processing companies that accepted the tape and specialized in stamping transfer, leading to the creation of a wide range of jobs unique to Japan. However, this inevitably results in an increase in the price per card.

[Means for Solving the Problems] As a result of intensive studies to improve the current problem of cystyl, which increases costs after going through multiple stages of distribution, the inventors of the present invention have discovered that they can manufacture plastic sheets for cards. At the time, a means for imparting magnetic recording properties to the sheet was developed, and the present invention was achieved.

That is, the present invention provides: 1. A biaxially oriented polyester sheet having a two-layer laminated structure, one layer of which contains finely dispersed ferromagnetic powder in an amount of 10% by weight or more; 2. Ferromagnetic powder-containing polyester obtained by melt-kneading a master polymer in which ferromagnetic powder is dispersed in a polyester with a low melt viscosity and a polyester with a high melt viscosity to dilute the concentration of the ferromagnetic powder to 10% by weight or more. This and a polyester with high melt viscosity that does not contain ferromagnetic powder are used to form a film by coextrusion to obtain an unstretched sheet with a two-layer laminated structure, and then the unstretched sheet is biaxially stretched. This is a method for manufacturing a magnetic recording sheet characterized by the following.

Double-layered recording sheets are well known for use in computer tapes, audio tapes, video tapes, floppy disks, video floppies, etc., but are not limited to cards. It is thought that the idea of forming a magnetic film at the same time has been warmed up among the respective companies, but in the actual implementation stage, technical means to ensure uniform recording density have not followed suit. It is in a state where it is not blooming. The biggest obstacle lies in the formation of a magnetic film layer to obtain a certain recording density. - In general, coextrusion film production of polyolefins such as polyethylene and polypropylene is well known and widely used, but in the case of polyester films, the melt extrusion temperature is extremely high, so two-layer films are formed by combining them with other different polymers. Structural laminates are extremely difficult to co-extrude because their flow properties vary widely. Therefore, in the case of a polyester film, for example, it may be a laminate of the same kind of films with different colors, or it may be a laminate with a dual surf ace structure in which one side is rough and the other side is ultra-flat. In particular, the functionality of two-layer and three-layer films, where one layer has the ability to selectively absorb light rays, is limited to a relatively high level of functionality.

In particular, when coextrusion film formation is performed by incorporating a large amount of ferromagnetic powder into one layer, such as in the case of magnetic cards, it is extremely difficult to easily and stably form a magnetic layer film. These ideas tend to have been virtually abandoned and not fully developed.

The present invention solves this problem by adopting the above-mentioned configuration, and is capable of producing a sheet having magnetic recording properties all at once using a polyester coextrusion method, and producing a magnetic layer film smoothly and uniformly. The key to this is to use a polyester with a low intrinsic viscosity, especially polyethylene terephthalate, or a copolymer polyester with a low melt viscosity, as the polymer for one layer of the two-layer structure, that is, to form the magnetic layer, and to uniformly cross-wire the ferromagnetic powder into this. The purpose is to perform dispersion.

In addition to securing a high concentration master polymer (master chip), it is important to maintain the melt viscosity behavior of the support material, which is polyester without magnetic powder, especially polyethylene terephthalate, so as not to deviate widely from that in film production of the laminate. This is important for stabilizing quality.

In order to improve the reliability of recording even in devices with low recording densities such as magnetic cards, it is preferable that the ferromagnetic powder has a performance of at least Hc of 4000 e or more. Ferromagnetic powder is affected to a large extent by the heat it receives when it is cross-dispersed in a kneader, such as a twin-screw extruder, and by the heat it receives during crystallization heat treatment after biaxial stretching. γ-Fe03. Particularly desirable are Co-doped γ-Fe2O, magnesium ferrite, zinc ferrite, barium ferrite, and the like.

Although it is not impossible to use γ-hematite, which is generally used in magnetic tapes, it is more preferable to use Co for the reasons mentioned above.
-γFe2O, and to enable more stable recording, these ferromagnetic powders should be present in the film at least to
The ferromagnetic powder used in the present invention has a particle size that is too small. If it is too bulky, it will be difficult to disperse, so 2orI
It is preferable to have a particle size of about f/l to 45rrr/, and the particle size is not particularly limited, but considering the dispersion and miscibility in a normal kneader, for example, a twin-screw extruder, it is preferable that the magnetic layer surface is extremely rough. In other words, it is preferably about 0.3μ to 4.5μ.

Next, as for the vehicle for dispersing these ferromagnetic powders, a molten dough 1 of polyester or copolyester having a low melt viscosity, such as polyethylene terephthalate having an intrinsic viscosity of 0.45 to 0.54, is introduced into a twin-screw router. Magnetic powder is supplied from a separate port and mixed, and thoroughly kneaded with a screw to form master chips. If the intrinsic viscosity is too low, kneading will be sufficient, but the magnetic layer will become brittle during coextrusion film formation, making it difficult to form an integral film.On the other hand, if the intrinsic viscosity is too high, kneading will be difficult. , specific volume (rd
For ferromagnetic powders with a large ferromagnetic powder/g), the mixing ratio is limited to a few percent at most. A preferred dispersion method is polyethylene terephthalate polymerization with an intrinsic viscosity of 0.45.
When the temperature reaches ~0.54, the molten polymer is introduced from the polymerization kettle into a twin-screw extruder.1. By sufficiently kneading the magnetic powder in the extruder, a blend (master polymer) with excellent dispersibility can be obtained. In addition, for magnetic powder with a large specific surface area, for example, a low viscosity copolyester obtained by combining isophthalic acid, sebacic acid, neobentyl glycol, hexanediol, etc. is used as a vehicle.
An effective method is to create a high-concentration doped master chip. Examples of copolymerized polyesters that can be used more practically include terephthalic acid 60 to 801o1%, sebacin #14
0~20r#01%, ethylene glycol 40~60
llot%, neopentyl glycol 60-40 n+
o1% range, more preferably terephthal 1171 mo1%, sebacic acid 2911 mo1
%, ethylene glycol 53 no. 1%, and neopentyl glycol 47,101%. The melt viscosity at that time is 16 at 260"C.
0 to 220 voids, preferably 40 to 100 voids at 280'C. In order to improve the dispersion of the magnetic powder, it goes without saying that dispersants, activators, etc. may be added to the lubricant 1, and additives that suppress thermal decomposition of the binder may be used as long as they do not interfere with the magnetic performance. Furthermore, the addition of antistatic agents to the magnetic layer to maintain good handling during winding, unwinding, printing, and punching also significantly changes the melt viscosity behavior of polyethylene terephthalate on the non-magnetic layer side. This is a preferable direction if there is no difference.

The concentration of the ferromagnetic powder in the master polymer is preferably 151% by weight or more. This master polymer is mixed and diluted with a polyester having a high melt viscosity to form a magnetic layer-forming polyester. The polyester for diluting the master polymer is preferably the same as the polyester forming the base layer; for example, polyethylene terephthalate having an intrinsic viscosity of 0.60 to 0.67 is preferably used.

In order to stabilize the magnetic recording performance, it is important to uniformly disperse the magnetic powder, so the copolymerized polyester from the previous example was mixed with toluene-ethyl acetate-methyl ethyl getone (mixing weight ratio = 2:1). :1) at a concentration of 20 to 3 wt%, and add 20 to 3 wt% of magnetic powder in this solution dope.
After mixing to a concentration of 0 wt%, the mixture is sufficiently finely dispersed with a sand glider, the mixed solution is cast onto a polyester film to form a dry film, and the film is then supplied as a film to a gelast converter (Hcondux, West Germany). If the granules are then mixed in a melt-kneader, for example, a coaxial twin-screw Lugoux, and made into chips, a more preferable form of the magnetic layer-forming polymer or master polymer can be obtained. Note that the copolymerized polyester and polyethylene terephthalate used here are the same type of polyester, so even if the polyethylene terephthalate film serving as the base is mixed in the granulation stage, they are sufficiently compatible when mixed in the melt M kneader.

If this method is used, it is extremely economical because there is no need to separate the substrate and the magnetic powder-containing film.

In the present invention, the polyester on the non-magnetic layer side can be a polyester used for forming a normal biaxially oriented film, and preferably includes polyethylene terephthalate having an intrinsic viscosity of 0.60 to 0.67. This polyester guarantees the required mechanical properties of the sheet.

It may be transparent or colored as long as the intrinsic viscosity is maintained, but when used for cards, tickets, securities, stamps, etc., it is necessary to print for aesthetic purposes, so titanium white, sulfuric acid, etc. Adding pigments such as barium, zinc oxide, magnesium oxide, and calcium carbonate to give the paper its color will expand its range of uses.
Such combinations are highly preferred.

Methods for producing polyester films by coextrusion are known, for example, British Patent No. 1,096,064, Japanese Patent Publication No. 10177/1982, Japanese Patent Publication No. 7633/1983, Japanese Patent Publication No. 48/41020, Japanese Patent Publication No. 48-41020, Japanese Patent Publication No. 48-41020, 46-14551, etc., can be directly applied or the principle used.

Further, the biaxial stretching treatment can also be carried out using two conventionally known manufacturing methods for magnetic recording medium base films. The thickness of the magnetic layer to be formed varies depending on its magnetic recording properties, but is usually 1 to 12μ, more preferably 2 to 7μ.If the magnetic layer becomes too thick than the non-magnetic layer, bending may occur. Therefore, the ratio of the non-magnetic layer to the magnetic layer is 1 for the former and 0.008 to 0.028 for the latter, which is a preferable range in which no defects occur.

According to the present invention, a sheet having the magnetic recording properties necessary for cards and the like can be manufactured all at once by a polyester coextrusion method, thereby shortening the manufacturing process and reducing costs. Furthermore, it has created various economic effects by encouraging opportunities for many general light printing companies to enter the industry, not just card manufacturers that have specialized in specific magnetic layer and aesthetic printing up until now. sell.

[Example] In order to make the aspect of the present invention clearer, the present invention will be explained in more detail by showing examples below.

Example 1 Intrinsic viscosity (orthochlorophenol, 35°C) 0°4
The melt of polyethylene terephthalate No. 6 was introduced into a coaxially rotating biaxial Lugu, and the melt was heated to a temperature of 4,500 Hc.
e, average particle size is 0.9μ, specific surface area is 23rrf/l
of CorFezo3 was added and mixed to a concentration of 1.
6.3% by weight master granules! tv(I> was obtained.

In a similar manner, a white master polymer (II) was obtained in which 24% by weight of titanium oxide having an average particle size of 0.3 μm was contained in polyethylene terephthalate having an intrinsic viscosity of 0.37.

A master polymer (I) for photocombining magnetic powder and a regular polyethylene terephthalate polymer with an intrinsic viscosity of 0.67 are mixed in a V-type blender until the concentration of magnetic powder is 1.
It was diluted to 0.7% by weight.

The white polymer (n) containing titanium oxide was also triblended with the above-mentioned normal polymer with an intrinsic viscosity of 0.67, which did not contain anything, and the final concentration of titanium oxide was 17% by weight.
It was diluted to give Each was heated at 170°C in a nitrogen stream.
Drying was performed for 4.2 hours.

Next, the walls are flattened and the extruded molten polymers are immediately joined together to form the front and back surfaces, and a connecting part is used as the connecting part. The titanium oxide-containing polyethylene terephthalate and the magnetic powder-containing polyethylene terephthalate prepared above were introduced into the machine, and the former was extruded at 290 to 300°C and the latter at 302 to 307°C, and the two-layer Mel 1~ was placed on a casting drum. The orientation of the magnetic particles was given before grounding. After sufficiently cooling this melt in a casting drum, it was stretched 2.95 times in the longitudinal direction and 3.07 times in the transverse direction according to a conventional method, and further crystallized at 190°C, resulting in a total thickness of 252μ. A biaxially stretched sheet was obtained.

In addition, by adjusting the polymer supply amount and die clearance, the magnetic powder-containing layer was set to have a thickness of 6.7μ, and this layer was
Conditions were set so that it contacted the casting drum surface.

The two-layer structure sheet thus obtained was white on one side and brown on the other, and was now 8.5m x 5.3mm.
A rectangular card of size W was punched out and bent over 90° over 50 times, but the magnetic layer side was not damaged at all and the card was highly durable.

In order to evaluate the characteristics of this magnetic layer side, the magnetic powder-containing layer was made to be 6.7 μm in the same manner as above except that the amount of polymer supplied was adjusted to the clearance of the die.

A two-layer structure film consisting of a magnetic powder-free layer of 6 μm was obtained. This two-layer structure film was cut into ribbons with a diameter of 6.35 mm, and was run at a speed of 9.5 am/Sec using a magnetic recording and reproducing device equipped with an audio fixed head, and the signals 1 and 7 were transmitted. Do not record or play.

The output level is measured using an audio level meter (reader electronic ■:
Measured using LrR-5602>. When the output of the audio open tape is set to OdB, the output level of this two-layer cadaver film was -4.4 dB.

Example 2 Terephthalic acid 711101%, sebacic acid 29 no1
%.

Consisting of 531lat% ethylene glycol and 47no1% neopentyl glycol, glass transition temperature 10
℃, a linear saturated copolymerized polyester with a melting temperature of 74 voids at 280℃ and CO-γF of OOQ where c is 6
e2O3 has a specific surface area of 29rrl'/ir and a particle size of 1.
A granular master polymer having a magnetic powder concentration of 32% by weight was obtained by mixing and fusing the mixture with 0μ magnetic powder using a twin-screw router.

On the other hand, barium sulfate having a particle size of 0.55 μm was kneaded into polyethylene terephthalate having an intrinsic viscosity of 0.66 using a similar twin-screw router to obtain a granular master polymer having a concentration of 28% by weight. The former is made of polyethylene terephthalate (normal polymer) with an intrinsic viscosity of 0.67 and diluted with triblend to a concentration of 16.1% by weight, while the contact material is made of polyethylene terephthalate (normal polymer) with an intrinsic viscosity of 0.67, and the above-mentioned normal polymer is diluted with a triblend so that the concentration of barium sulfate is 12% by weight. Raw materials (I) and (II) were prepared by diluting with a polymer. For raw material (I), the melting temperature was 293°C.
I) was coextruded under the same conditions as in Example 1 except that a melting temperature of 394°C was used to obtain a biaxially stretched card sheet having a magnetic layer of 8.4μ and a total thickness of 254μ. After printing on a base surface with a white pearlescent tone, cut out a card with dimensions of 8.5cm (vertical) and 5.3cm (width).
Although the bending process was repeated more than 50 times, the magnetic layer side was not damaged at all.

In order to evaluate the characteristics of this magnetic layer side, a two-type elliptical body consisting of a magnetic powder-containing layer of 8.4 μm and a non-magnetic powder-containing layer of 8.4 μm was prepared in the same manner as above except for adjusting the polymer supply amount and die clearance. Got the film. This two-layer cadaver film was cut into a ribbon shape with a width of 6.35 on, and using the same magnetic recording/reproducing device and level meter as in Example 1, lKH2
As a result of measuring the output level, an output of -3.3 dB was obtained compared to the output of audio open tape.

Comparative Example 1 A film was formed using the same method as in Example 2 except that the magnetic powder concentration of raw material I was lowered to 2.7% by weight, but the magnetic recording ability was low and reliability was lacking. .

It has the advantage of being able to be manufactured using Moreover, the sheet will encourage not only conventional magnetic card manufacturers but also many general light printers to enter this field.

Comparative Example 2 In Example 2, the specific surface area was 55<r+f/g), HC
Co-7Fe203 with a particle size of 650 Oe and a particle size of 0.47μ
so that the concentration is 11% by weight, the intrinsic viscosity is 0.62
Attempts were made to directly mix polyethylene terephthalate with a twin-screw luder, but this master polymer had poor dispersion and often lacked tensile compliance during coextrusion, resulting in brittle films with surface defects, making it impossible to achieve an acceptable composition. It could not be a body.

[Effects of the Invention] According to the present invention, it is possible to provide a magnetic recording sheet having a highly durable magnetic layer and a method for producing the same at once using a polyester coextrusion method. Teijin Co., Ltd. Patent applicant for low cost magnetic cards useful for Irish cards and securities
Company procedure amendment document P. 22, 1986

Claims (1)

[Scope of Claims] 1. A magnetic recording sheet, which is a biaxially oriented polyester sheet having a two-layer laminated structure, in which one layer contains finely dispersed ferromagnetic powder in an amount of 10% by weight or more. 2. Ferromagnetic powder obtained by melt-kneading a master polymer in which ferromagnetic powder is dispersed in a polyester with a low melt viscosity and a polyester with a high melt viscosity to dilute the concentration of the ferromagnetic powder to 10% by weight or more. A polyester containing polyester is obtained, and this and a polyester with a high melt viscosity that does not contain ferromagnetic powder are used to form a film by a coextrusion method to form an unstretched sheet with a two-layer laminated structure, and then the unstretched sheet is biaxially stretched. A method for manufacturing a magnetic recording sheet, characterized by: 3. Polyester with low melt viscosity has an intrinsic viscosity of 0.45
polyethylene terephthalate with a high melt viscosity of 0.54, and polyester with a high melt viscosity has an intrinsic viscosity of 0.60 to 0.6.
3. The method according to claim 2, wherein the polyethylene terephthalate is polyethylene terephthalate of No. 7. 4. The manufacturing method according to claim 2, wherein the ferromagnetic powder has a coercive force Hc of 240 Oe or more.