JP3195472B2 - Magnetic recording device and magnetic recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording apparatus and a magnetic recording method capable of recording magnetic recording information while efficiently heating a magnetic recording layer of a magnetic recording medium.

[0002]

2. Description of the Related Art A magnetic recording medium in which a magnetic recording layer is formed in an entire area on one side or both sides of a substrate or in a stripe shape is provided.
For example, prepaid cards, commuter passes, tickets, admission tickets,
Vouchers, securities such as car tickets, betting tickets, gift certificates, stock certificates, certificates, passbooks, magnetic tags, cards such as ID cards, cash cards, credit cards, membership cards, magnetic tapes,
Widely used as magnetic transfer tapes, magnetic labels, etc. Conventionally, in such a magnetic recording medium, information is written at a high recording density on a magnetic recording layer so that the recorded information cannot be easily read from the outside.

However, due to the characteristics of the magnetic recording layer, the recorded information can be freely rewritten and erased, so that forgery and falsification are possible. In recent years, it has been highlighted as a major social problem. In particular, since it is now easy to obtain a magnetic stripe, it is possible to manufacture a similar card, and if the magnetic recording layer is exposed on the surface of the magnetic recording medium as in the current specification. Also, there is a problem that magnetic recording information can be easily transferred to another magnetic recording layer by magnetic transfer technology.

To solve such a problem, a magnetic recording medium has been developed in which a magnetic material used for a magnetic recording layer has a high coercive force. By heating the magnetic recording layer to reduce the coercive force of the magnetic material, this magnetic recording medium enables recording and reproduction with an easily available ordinary magnetic head.
It is difficult to reproduce and cannot be forged or altered.

[0005]

However, since the above-mentioned magnetic recording medium generally uses a resin sheet as a base, the magnetic recording layer is heated by a conventional magnetic recording apparatus when a card is issued or the like. When magnetic recording information is recorded, there is a problem that the substrate is deteriorated or deformed by heat. On the other hand, when the issued magnetic recording medium is heated for the purpose of forgery or alteration, it can be said that deterioration and deformation of the substrate are preferable from the viewpoint of preventing forgery. Therefore, there is a demand for a magnetic recording apparatus and a magnetic recording method capable of recording magnetically recorded information while heating the magnetic recording layer of the magnetic recording medium without causing deterioration or deformation of the base due to heat at the time of issuance or the like. , Not yet realized.

The present invention has been made in view of such circumstances, and selectively heats a magnetic recording layer of a magnetic recording medium to minimize the influence of heat on a substrate. It is an object of the present invention to provide a magnetic recording device and a magnetic recording method capable of recording magnetic recording information.

[0007]

In order to achieve the above object, a magnetic recording apparatus of the present invention records magnetic recording information on the magnetic recording layer of a magnetic recording medium having a magnetic recording layer on a substrate. In the magnetic recording device, the magnetic recording layer has a multilayer structure, and at least two layers forming the multilayer structure include:
The magnetic material contained in one layer has a higher coercive force and a lower Curie point than the magnetic material contained in the other layer, and has a lower Curie point than the magnetic material having a lower Curie point. The magnetic recording medium of the present invention is provided with a heating means capable of selectively heating the magnetic recording layer of the magnetic recording medium in a temperature range equal to or higher than half the temperature. Further, according to the magnetic recording device of the present invention, in a magnetic recording device for recording magnetic recording information on the magnetic recording layer of a magnetic recording medium having a magnetic recording layer on a base, one of the magnetic recording layers is higher than the other. A temperature range that is a mixture of two or more magnetic materials having a magnetic force and a low Curie point, and is lower than the Curie point of the magnetic material having a low Curie point and equal to or higher than half the temperature of the Curie point. And a heating means for selectively heating the magnetic recording layer of the magnetic recording medium.

Further, the magnetic recording method of the present invention has a multilayer structure in which the magnetic material contained in at least one of the two layers has a higher coercive force and a lower Curie point than the magnetic material contained in the other layer. The magnetic recording layer of a magnetic recording medium having a magnetic recording layer having a low Curie point lower than the Curie point of a magnetic material having a low Curie point.
The configuration is such that magnetic recording information is recorded on the magnetic recording layer while being selectively heated in a temperature range equal to or higher than / 2. Further, the magnetic recording method of the present invention is characterized in that the magnetic recording medium comprises a magnetic recording layer containing a mixture of two or more magnetic materials having a higher coercive force and a lower Curie point than the other. The recording layer is set to be lower than the Curie point of a magnetic material having a low Curie point by 1/1/2 of the Curie point.
The magnetic recording information is recorded on the magnetic recording layer while being selectively heated in a temperature range of 2 or more.

[0009]

The heating means constituting the magnetic recording apparatus selectively heats the magnetic recording layer provided on the base of the magnetic recording medium, so that the magnetic recording medium is hardly affected by the heat. Magnetic recording information is recorded by the magnetic recording device.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining the configuration of a magnetic recording apparatus according to the present invention. In FIG. 1, a magnetic recording device 1
Are a magnetic recording medium supply unit 2, a heating unit 3, a magnetic recording unit 4,
It comprises a cooling unit 5 and a magnetic recording medium discharge unit 6.

The magnetic recording medium supply section 2 and the magnetic recording medium discharge section 6 are not particularly limited, and may be the same as those provided in a conventional magnetic recording apparatus. Incidentally, the magnetic recording apparatus of the present invention has such a magnetic recording medium supply unit 2,
It may not include one or both of the magnetic recording medium ejection units 6.

The heating unit 3 constituting the magnetic recording apparatus 1 of the present invention is characterized in that it can selectively heat the magnetic recording layer of the magnetic recording medium supplied to the heating unit 3. The magnetic recording method of the present invention is characterized in that magnetic recording information is recorded on the magnetic recording layer while selectively heating the magnetic recording layer.

The heating section 3 can be a heating means such as a light heating method, a direct resistance heating method, an indirect resistance heating method, an induction heating method, a dielectric heating method, or the like. next,
Each heating means and a method of heating the magnetic recording layer by the heating means will be described.

First, the light heating type heating unit 3 will be described.
FIG. 2 is a diagram for explaining the heating unit 3 of the light heating system. The heating unit 3 includes a light source 11 and a control unit 12 for condensing light emitted from the light source 11 into a predetermined shape. ,
The light that has passed through the control unit 12 is applied to the magnetic recording layer B of the magnetic recording medium A.

As the light source 11, an infrared radiation source or a laser beam radiation source can be used.

The infrared radiation source includes a temperature radiation type and a cold radiation type. Examples of temperature radiation type infrared radiation sources include infrared light bulbs (100 to 1000 W), tubular infrared light bulbs (500 to 2000 W), nichrome wire and tantalum wire resistance heaters, glowers (silicon carbide heating), and Nernst glowers (ceramic heating). , A far-infrared sheathed heater, a far-infrared planar radiating element, a far-infrared lamp, a quartz tube heater, a carbon arc lamp and the like. In addition, as a cold radiation type infrared radiation source, a mercury lamp (100 to
2000W), Xenon lamp (100W-100k)
W), halogen lamps (including light in the visible region), sodium lamps, metal halide lamps, and the like.

More specifically, the following infrared radiation sources can be mentioned. (1) 600 W infrared light bulb: The magnetic recording layer surface temperature can be raised to 50 to 100 ° C. by diffused light, and can be raised to 100 to 300 ° C. by condensing light. (2) 10 kW far-infrared lamp: The surface temperature of the magnetic recording layer can be raised to 100 ° C. by diffused light.
Can be heated up to 00 ° C. (3) 20 kW planar far-infrared heater: The surface temperature of the magnetic recording layer can be increased to 200 ° C. by parallel irradiation (irradiation for 5 seconds, distance 10 mm), and the irradiation surface having the same shape as the desired heating area of the magnetic recording layer can be obtained. Possible and uniform heating possible. In addition, heat diffusion to the periphery is small.

The laser beam can be emitted using a gas laser device, a solid laser device, a liquid laser device, a semiconductor laser device, or the like. As gas lasers, He-Ne laser, He-Cd laser,
Argon laser (0.488 μm continuous oscillation, 0.1 ~
A rare gas ion laser such as 20 W), a carbon dioxide laser (10.6 μm continuous oscillation, 1 W to 10 kW), a metal vapor laser, and the like can be used. As a solid laser, a ruby laser (0.6943 μm pulse oscillation,
10-1000J), Nd glass laser (1.06μ)
m-pulse oscillation, 10-1000 J), pulse-excited solid laser such as Nd: YAG laser, or ruby laser, Nd glass laser, Nd: YAG laser (1.06 μm continuous oscillation, 1-200 W), Nd: YA
A continuous excitation solid-state laser such as a 10 ₃ laser can be used. In addition, examples of the liquid laser include a dye laser, a Raman laser, a chelate laser, and an Nd ³⁺ liquid laser, and examples of the semiconductor laser include a GaAs diode laser. Among the above lasers, a high-power laser such as an argon laser, a carbon dioxide laser, a ruby laser, a Nd glass laser, and a Nd: YAG laser is preferably used. Such a high-power laser is suitable for the case where an irradiation spot, which will be described later, is expanded without being focused, or the case where a heating region is repeatedly scanned at a high speed.

More specifically, the following laser beam radiation sources can be mentioned. (1) 1 kW carbon dioxide laser: 7 mm diameter on the magnetic recording layer
The temperature can be raised to 200 ° C by irradiating the beam in a spot shape of mm and scanning the 85 mm long heating area 10 times in 1 second. (2) 1 kW carbon dioxide laser: 7 mm in diameter on a heating target having a hologram layer on a magnetic recording layer as described later
The magnetic recording layer can be heated to 200 ° C. while the temperature of the hologram layer is kept at 150 ° C. by irradiating a beam in the form of a spot and scanning the 85 mm long heated area 10 times in 1 second.

In the heating of the magnetic recording layer by the light heating method using the infrared radiation source or the laser beam radiation source as described above, the irradiation shape can be appropriately selected. For example, by irradiating light onto the magnetic recording layer as a small-area irradiation surface in the form of a slit, or a circular or elliptical spot in the form of a slit, or by scanning the irradiation surface, or by transporting a magnetic recording medium, The magnetic recording layer can be selectively heated while minimizing the heating of the substrate. In particular,
The circular or elliptical spot-shaped small area irradiation surface can make the irradiation amount different between the center of the spot and both sides, lowering the temperature at both ends than the temperature at the center of the magnetic recording layer, The influence of heating on the substrate can be reduced. By repeatedly scanning the irradiation surface at high speed, uniform heating in the recording direction of the magnetic recording layer becomes possible. Further, the irradiation surface having the same shape as the desired heating region of the magnetic recording layer can be used to perform surface irradiation on the magnetic recording layer. By such planar irradiation, a desired region of the magnetic recording layer can be uniformly heated.

The heating of the magnetic recording layer by the above-described light heating method is non-contact heating, so that there is no heating failure due to contact unevenness, and no damage or dust is attached to the surface of the magnetic recording medium. It does not affect the conveyance of the magnetic recording medium. In addition, since the shape of the irradiation surface can be freely set, the influence of the magnetic recording medium on the base can be suppressed by minimizing the heating area. Furthermore, by guiding light from the irradiation source by optical fiber,
For example, it is possible to irradiate an arbitrary place immediately before the magnetic head, such as a gap portion of another heating means. Further, even if a transparent layer such as a transparent hologram layer and a protective layer is formed on the magnetic recording layer as described later, the irradiated light passes through the transparent layer and reaches the magnetic recording layer, and The recording layer can be directly heated. In order to efficiently absorb the irradiated light in the magnetic recording layer, the magnetic recording layer preferably contains a light absorber. For example, by mixing about 1.0 to 10.0% by weight of carbon black in the magnetic recording layer, the temperature rise can be reduced by 5% under the same irradiation condition.
Up to 20%. Further, by making the irradiation surface shape the same as the heating area, it is suitable for heating the magnetic recording medium in a stationary state, and is also suitable for preheating in combination with another heating method described later. . In a combination with another heating method, for example, heating by a light heating method is performed between heat rolls, so that the heating distribution can be made more uniform. Also, unlike the light heating method, the other heating method cannot be disposed so close to the magnetic recording head, and thus the light heating method can be used as an auxiliary to the other heating methods.

Further, the heating of the magnetic recording layer of the light heating type by the infrared irradiation is low in cost, easy to maintain, can set a wide irradiation area, and can perform planar irradiation on the magnetic recording layer. it can. In addition, the heating of the magnetic recording layer of the light heating method by laser irradiation is performed by the irradiation amount,
Since the accuracy of the irradiation position is high, the heating area and the temperature of the magnetic recording layer can be controlled with high accuracy, and the ON / OFF control of the laser beam can be easily performed using the light modulation element. In addition, when an optical fiber is used, since the energy loss is small, a heating unit (laser beam radiation source) is provided separately from the magnetic recording device, and the laser beam is introduced from the heating unit into the magnetic recording device via the optical fiber. The size of the magnetic recording device itself can be reduced. Further, heat diffusion around the heating section is small.

Next, the heating section 3 of the direct resistance heating type will be described. In the direct resistance heating method, the magnetic recording layer itself generates heat by passing a current directly to the magnetic recording layer. For this reason, the magnetic recording layer is preferably formed as an Fe-Ni-Cr-based magnetic thin film layer in consideration of heat generation. Further, the magnetic recording layer is preferably a magnetic recording layer mainly composed of metal magnetic powder, to which a conductive pigment such as carbon black is added to reduce the overall electric resistance. In order to pass a current directly to the magnetic recording layer, current is supplied by bringing electrodes into contact with both ends of the magnetic recording layer in the recording direction. For this purpose, the heating unit 3 is configured to be movable together with the magnetic recording medium. Is preferred. Further, in consideration of the heat generation efficiency, it is preferable that the magnetic thin film layer is further formed into a linear (strip-like) thin film.

More specifically, an Fe—Ni—Cr alloy thin film (1 μm thick, 1 μm thick) as a high Curie point magnetic recording layer
0 mm width x 86 mm length) has a resistance value of about 10 in the longitudinal direction.
Ω, and a voltage of 10 V
The current of 10 ³ J is generated by flowing the current of 1 second,
According to this method, an Fe—Ni—Cr alloy thin film is
It is possible to heat to 0-300 ° C.

Next, the heating section 3 of the indirect resistance heating system will be described. As one of the indirect resistance heating methods, a heating layer is provided adjacent to the magnetic recording layer, and an electric current is applied to the heating layer to generate heat, thereby indirectly heating the magnetic recording layer.
As the heating layer, a nichrome thin film layer, an iron chromium thin film layer, or the like can be used. Such a heating layer is formed above the magnetic recording layer, or formed below the magnetic recording layer and formed on the magnetic recording layer. It can be exposed at both ends in the recording direction.

As another example of the indirect resistance heating method,
There is a type in which the magnetic recording layer is indirectly heated by a contact method using a general heating means such as a heat roller or a hot plate. The heat roller preferably has a peripheral surface covered with a soft member such as a silicon rubber roll so as not to damage the surface of the diffraction grating layer or the hologram layer as described later. The width of the roller is to reduce the effect of heat on the base,
It is preferable that the width is slightly smaller than the width of the magnetic recording layer. Also,
Arranging a plurality of rollers having a smaller diameter than a single roller having a larger diameter has a higher heating efficiency and can increase a transport speed. For example, 5 to 10 pairs of heating rollers having a width of 10 mm and a diameter of 20 mm are arranged in series, and the heating rollers can be heated while conveying the magnetic recording medium. The surface temperature of such a heat roller is appropriately set in the range of 50 to 300 ° C., and the speed of the heat roller is 10 to 200 mm /
sec.

On the other hand, when a hot plate is used, the hot plate may be a metal plate with a built-in heater, but preferably has a surface provided with silicon rubber. In the heating by the hot plate, the surface temperature of the hot plate is set in the range of 100 to 300 ° C., and the pressure can be about 1 to 10 kg / cm ² .
It is preferable to provide a feedback mechanism for appropriately controlling the set value of the heating condition of the heat roller based on the surface temperature of the heat roller, the hot plate, the surface temperature of the magnetic recording layer or the reproduction output level of the magnetic recording layer.

Next, the induction heating type heating unit 3 will be described. In the induction heating method, an alternating magnetic field is applied to a magnetic recording medium to generate heat in the magnetic recording layer itself or a layer adjacent to the magnetic recording layer, thereby heating the magnetic recording layer. Since it is a conductor that generates heat when an alternating magnetic field is applied, the magnetic recording layer itself may be a conductive layer, or a thin film or foil of copper, aluminum, steel, or the like may be located adjacent to the magnetic recording layer. It is necessary to provide an electrically conductive heating layer. The thickness of the above-mentioned heating layer is preferably about 1000 ° to 1 μm, and the alternating magnetic field frequency is preferably about 1 to 100 kHz. With such an induction heating method, non-contact heating is possible and rapid heating is also possible. Further, by applying an alternating magnetic field in a direction perpendicular to the magnetic recording direction, the heating can be performed while suppressing the influence on the magnetic recording.

When an alternating magnetic field is applied to the magnetic recording layer, as shown in FIG. 3, an alternating current is applied to the heating coil 15 to generate an alternating magnetic field, and the entire magnetic recording medium A is positioned in the alternating magnetic field. It can be done by doing. FIG.
As shown in (1), an alternating magnetic field may be applied only to the magnetic recording layer region by a magnetic recording head 16 in which an ordinary magnetic recording head 17 and an alternating magnetic field applying magnet 18 are combined. In this case, the recording magnetic field by the normal magnetic recording head 17 and the alternating magnetic field by the alternating magnetic field applying magnet 18 need to be configured to be perpendicular to each other. By using such a magnetic recording head 16, simultaneous recording with heating can be performed.

Next, the heating section 3 of the dielectric heating system will be described. In the dielectric heating method, an alternating electric field is applied to a magnetic recording medium to generate heat in a dielectric layer adjacent to the magnetic recording layer and heat the magnetic recording layer. The frequency band of the alternating electric field is preferably about 0.1 MHz to 3000 MHz, and the calorific value is proportional to the dielectric constant of the dielectric layer together with the electric field strength and frequency. Therefore, the dielectric layer is preferably made of a material having a large dielectric constant. . As a material having a large dielectric constant, specifically, in consideration of the fact that the dielectric layer is heated to 100 to 300 ° C., a resin having a high melting point and a high decomposition point such as polyimide, polyimide amide, and polyether sulfone is used. preferable.
The dielectric layer has a thickness of about 10 to 1000 μm, and may be formed above or below the magnetic recording layer.

More specifically, a polyimide layer having a thickness of 100 μm is provided under the magnetic recording layer, and an alternating electric field of 80 MHz is applied at a power density of 50 W / cm ² to generate heat in the polyimide layer. The layer can be heated to 150 ° C.

The heating unit 3 can be configured by combining any of the above-described light heating method, direct resistance heating method, indirect resistance heating method, induction heating method, and dielectric heating method with other heating methods. .

The heating section 3 which can be constituted by the various heating means as described above is separate from the magnetic recording section 4, but the heating section 3 constituting the magnetic recording apparatus 1 of the present invention is And the magnetic recording unit 4. That is, the magnetic recording head itself can be used as the heating means. Heating of the magnetic recording layer by the magnetic recording head is performed by heating the magnetic recording head to 50 to 150 ° C. by any of the above-described light heating method, direct resistance heating method, indirect resistance heating method, induction heating method, and dielectric heating method. Heating to a degree can be performed. However, since the magnetic recording head degrades its characteristics due to heating exceeding 150 ° C.,
The heating of the magnetic recording layer up to the range of 00 ° C. is preferably performed in combination with the other heating methods described above.

The magnetic recording section 4 constituting the magnetic recording apparatus 1 of the present invention is not particularly limited, and can be constituted by using a magnetic recording head used in a conventional magnetic recording apparatus. However, when heating the magnetic recording layer by the magnetic recording head itself as described above, it is necessary to use a magnetic recording head having a structure as shown in FIG.

The cooling unit 5 constituting the magnetic recording apparatus 1 of the present invention is for cooling the heating unit 3 or the magnetic recording medium heated in the heating unit 3 and the magnetic recording unit 4. The cooling unit 5 includes, for example, a cooling roller and a cooling plate, and the magnetic recording medium is cooled by bringing the magnetic recording medium into contact with the cooling roller or the cooling plate cooled by the refrigerant. In addition, the cooling unit 5 may be of an air-cooling type by blowing air. In this case, cooling air may be used, or the above-described cooling roller or the like may be used in combination.
Such a cooling unit 5 is not an essential component of the magnetic recording apparatus of the present invention, and can be omitted if forced cooling of the magnetic recording medium is not required.

In the magnetic recording apparatus 1 of the present invention, if necessary, cooling means for cooling the peripheral portion of the heating section 3 to prevent the influence of heat on other portions of the magnetic recording apparatus 1 may be provided. it can. As such a cooling means, a cooling plate whose temperature is controlled by a method such as water cooling or air cooling is used.
Can be cited.
Alternatively, the heating unit 3 may be directly cooled by blowing air.

Next, an example of a magnetic recording medium applicable to the above-described magnetic recording apparatus and magnetic recording method of the present invention will be described. FIG. 5 is a schematic sectional view showing an example of a magnetic recording medium applicable to the present invention. In FIG. 5, a magnetic recording medium 21 includes a base 22 and a magnetic recording layer 23 provided on the base 22. The magnetic recording layer 23 is
A first magnetic recording layer 23a located on the side of the base 22, and a second magnetic recording layer 23 provided on the first magnetic recording layer 23a.
b. The magnetic materials included in the first magnetic recording layer 23a and the second magnetic recording layer 23b have different Curie points and coercive forces.

The base 22 is made of nylon, cellulose diacetate, cellulose triacetate, vinyl chloride, vinyl chloride, polystyrene, polyethylene, polypropylene, in consideration of heat resistance, strength, rigidity, concealing property, light opacity and the like required for the base. It can be composed of a resin alone such as polyester, polyimide, polycarbonate, and the like, a metal such as copper and aluminum, a material selected appropriately from materials such as paper, impregnated paper, and the like, alone or in combination. The thickness of such a base 22 can be about 0.005 mm to 5 mm.

The magnetic material contained in the first magnetic recording layer 23a constituting the magnetic recording layer 23, and the second magnetic recording layer 23
One of the magnetic materials contained by b has a higher coercive force and a lower Curie point Tc than the other. Here, whether the magnetic recording layer having a high coercive force and a low Curie point is used as the first magnetic recording layer 23a or the second magnetic recording layer 23b can be selected in consideration of the following effects.

When the first magnetic recording layer 23a is a magnetic recording layer having a high coercive force and a low Curie point Tc and the second magnetic recording layer 23b is a magnetic recording layer having a low coercive force and a high Curie point, the upper layer The second magnetic recording layer 23b conceals the underlying first magnetic recording layer 23a. Therefore, it is difficult for a forger to notice the presence of the first magnetic recording layer 23a made of a magnetic material having a high coercive force and a low Curie point. In addition, since the second magnetic recording layer 23b made of a magnetic material having a low coercive force is provided on the upper layer, troubles due to magnetic transfer hardly occur. Further, by setting the average particle diameter of the magnetic material constituting the second magnetic recording layer 23b to 0.1 μm or less, the transmittance of infrared rays in the second magnetic recording layer 23b is improved, and the light heating by infrared rays as described above is performed. When the method is used, there is an effect that only the first magnetic recording layer 23a can be selectively heated even though the first magnetic recording layer 23a is hidden.

On the other hand, the first magnetic recording layer 23a has a low coercive force,
When the magnetic recording layer has a high Curie point Tc and the second magnetic recording layer 23b is a magnetic recording layer having a high coercive force and a low Curie point, the second magnetic recording layer 23b is an upper layer. Second magnetic recording layer 23b
Is easily heated directly. Further, during magnetic recording while heating, the heat rise distribution is higher in the second magnetic recording layer 2.
3b, which concentrates on the magnetic recording layer having a high coercive force and a low Curie point, and requires less heat diffusion to the magnetic recording layer having a low coercive force and a high Curie point which is the lower first magnetic recording layer 23a. The Curie point of the first magnetic recording layer 23a can be relatively low, and damage due to heat can be reduced. Furthermore, at the time of magnetic recording, the layer far from the magnetic head is a magnetic recording layer having a low coercive force, so that the magnetic field strength (write current value) can be reduced. Furthermore, since the upper layer is a magnetic recording layer having a high coercive force, there is an effect that it is difficult for a forger to notice the lower first magnetic recording layer 23a.

The magnetic recording layer 23 having such a configuration is heated at a temperature lower than the Curie point Tc of the magnetic recording layer having a low Curie point Tc, so that the first magnetic recording layer 2 is heated.
3a and the second magnetic recording layer 23b have substantially the same or close saturation write current values, and thereby a specific write current set value (for example, 1.5% of the saturation current value) of a low coercivity magnetic material.
The saturation current value of a magnetic material having a high coercive force is smaller than that of a magnetic material having a high coercive force.

For example, the first magnetic recording layer 23a is a magnetic recording layer having a high coercive force and a low Curie point Tc,
When the magnetic recording layer 23b is a magnetic recording layer having a low coercive force and a high Curie point, the first magnetic recording layer 23 which is a high coercive force magnetic recording layer is heated at a temperature lower than the Curie point Tc.
By reducing the coercive force a, the saturation write current value can be made substantially the same as or close to the saturation write current value of the second magnetic recording layer 23b. As a result, a specific write current setting value (for example, 1.5 times the saturation current value) of the magnetic material having a low coercive force
(2.0 times), the saturation current value of the magnetic material having a high coercive force can be made smaller. At this time, if the heating temperature is too low, the first magnetic recording layer 23 which is a high coercive force magnetic recording layer
a does not become the same level as the saturation write current value of the second magnetic recording layer 23b, or the saturation current of the high coercivity magnetic recording layer Since writing cannot be performed, it is preferable to set the lower limit of the heating condition to a temperature of about 1/2 of the low Curie point Tc. In addition, both magnetic recording layers 23a, 23
When the Curie point of b is close, the second layer having a low coercive force magnetic recording layer
The coercive force of the magnetic recording layer 23b also decreases. For this reason, it is preferable to set the difference between the Curie points of the two magnetic recording layers 23a and 23b to 100 ° C. or higher to prevent the coercive force of the low-coercivity magnetic recording layer from decreasing. Further, in order to prevent magnetic recording on the first magnetic recording layer 23a and the second magnetic recording layer 23b from being influenced by each other, both magnetic recording layers 23a
It is preferable to set the difference between the coercive forces of a and 23b at least twice.

Examples of the magnetic material constituting the magnetic recording layer having a high coercive force and a low Curie point Tc include, for example, CrO ₂ , AO.n ｛(Fe _1-XY Cr _X Zn _Y ) having a low Curie point.
₂ O ₃ ｝, AO · n ｛(Fe _1-x Cr _x ) ₂ O ₃ ｝, A
On ・ (Fe _1-x Al _x ) ₂ O ₃ ｝, AOnＯ (F
e _1-X Ga _X ) ₂ O ₃ ｝, AOnn ｛(Fe _1-XYZ G
a _X Cr _Y Al _Z ) ₂ O ₃ ｝, AOn ・ (Fe _{1 -XY}
Sr ferrite, Ba ferrite, Nd—Fe represented by Cr _X Ga _Y ) ₂ O ₃ } (where A is one or two of Sr or Ba, n = 5 to 6)
-B-Mn, Nd-Fe-B-Mn-Al, Nd-Fe
-B-Mn-Cr, Nd-Fe-B-Mn-Al-Cr
And magnetic fine particles such as Nd-Fe-B-based alloys. Then, a magnetic recording layer is formed by applying a dispersion obtained by dispersing the above magnetic fine particles in an appropriate resin or ink vehicle according to a known coating method such as a gravure method, a roll method, or a knife edge method. Can be.

As a magnetic material constituting a magnetic recording layer having a low coercive force and a high Curie point, for example, γ-Fe ₂
O ₃ , Co-coated γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Fe, F
e-Cr, Fe-Co, Co-Cr, Co-Ni, Ba
Magnetic fine particles such as ferrite, Sr ferrite, and CrO ₂ are exemplified. When the magnetic recording medium 21 is heated by the heating unit 3 by a direct resistance heating method, the magnetic material is preferably an Fe-Ni-Cr-based material.

The magnetic recording layer is formed by applying a dispersion obtained by dispersing the above magnetic fine particles in an appropriate resin or ink vehicle according to a known coating method such as a gravure method, a roll method, or a knife edge method. Can be formed. Further, Fe, Fe-Cr, Fe-Co, C
Using a metal or alloy such as o-Cr, or an oxide thereof, it can also be formed by a vacuum evaporation method, a sputtering method, a plating method, or the like.

The average particle size of the above magnetic material is set to 0.1
When the thickness is not more than μm, the transmittance of the magnetic recording layer with respect to infrared rays is improved. When the heating unit 3 is a light heating method using infrared rays, the irradiated infrared rays pass through the magnetic recording layer that does not require heating. It becomes possible to heat a predetermined magnetic recording layer.

The resin or ink vehicle in which the magnetic fine particles are dispersed include butyral resin, vinyl chloride / vinyl acetate copolymer resin, urethane resin, polyester resin, cellulose resin, acrylic resin, styrene /
A maleic acid copolymer resin or the like is used, and a rubber-based resin such as a nitrile rubber or a urethane elastomer is added as necessary. Further, in consideration of heat resistance, a resin having a high glass transition temperature (Tg) such as polyamide, polyimide, polyethersulfone or the like, or Tg by a curing reaction.
Can be used. If necessary, a pigment such as a surfactant, a silane coupling agent, a plasticizer, a wax, a silicone oil, and a garbon is added to the dispersion of the magnetic fine particles dispersed in the resin or the ink vehicle as described above. You may.

The thickness of the first magnetic recording layer 23a and the second magnetic recording layer 23b formed using the above-described magnetic material, resin or ink vehicle is 1 to 100 μm when formed by a coating method. , Preferably 5 to 20
It is about μm. Further, when it is formed by a vacuum deposition method, a sputtering method, a plating method, or the like, the thickness is about 100 to 1 μm, preferably about 500 to 2000 °.

A heating layer for indirect resistance heating, a heating layer for induction heating, and a dielectric heating layer above the magnetic recording layer 23 or between the substrate 22 and the magnetic recording layer 23 as described above. A dielectric layer or the like can be formed.

In the above example, the magnetic recording layer 23 has a two-layer structure of the first magnetic recording layer 23a and the second magnetic recording layer 23b, but may have a laminated structure of three or more layers. The magnetic recording layer 23 may be made of three or more magnetic materials having different coercive forces and Curie points. As the magnetic recording layer having a three-layer structure, for example, by setting (high coercive force / low Curie point) / (low coercive force / high Curie point) / (high coercive force / low Curie point), the high coercive force layer and the low coercive force The writing waveforms of the layers can be made more identical. Further, by writing further magnetic data into the intermediate coercive force layer with three steps of coercive force, or setting the heating temperature at two steps with three steps of Curie point, a more advanced recording / reproducing system can be realized. can do.

Further, the magnetic recording layer 23 may be formed of a single layer instead of a laminated structure, and may contain a mixture of two or more magnetic materials having different coercive forces and Curie points. In this case, the same effect as in the case of the multilayer structure can be obtained.
Further, since the number of constituent layers is small, there is an advantage that the distance between the lowermost portion of the magnetic recording layer and the magnetic head can be reduced.

In the above-described magnetic recording medium, the magnetic recording layer may be formed on one entire surface of the base, or as shown in FIG. The magnetic recording layer 23 may be formed.

FIG. 7 is a schematic sectional view showing another example of a magnetic recording medium that can be used in the present invention. 7, the magnetic recording medium 31 includes a base 32, a magnetic recording layer 33, a diffraction grating and / or a hologram layer 34 provided on the base 32. The above magnetic recording layer 3
3 is a first magnetic recording layer 33a located on the base 32 side;
It has a two-layer structure with the second magnetic recording layer 33b provided on the first magnetic recording layer 33a. The magnetic materials included in the first magnetic recording layer 33a and the second magnetic recording layer 33b have different Curie points and coercive forces.

The base 32 and the magnetic recording layer 33 can have the same configuration as the base 22 and the magnetic recording layer 23 of the magnetic recording medium 21 described above, and the description is omitted here.

The diffraction grating and / or hologram layer 34 used for the magnetic recording medium 31 is generally made of a resin, and may have a single structure or a multilayer structure. In the case of a multi-layer structure, for example, a resin provided for forming a diffraction grating or a hologram on a base film, or a resin itself for forming a diffraction grating or a hologram may have a laminated structure. Further, the whole area may be a diffraction grating layer or a hologram layer, and the diffraction grating layer and the hologram layer may be mixed.

The hologram layer may be either a plane hologram or a volume hologram. In the case of a plane hologram, a relief hologram is preferable in terms of mass productivity, durability and cost. It is preferable from the viewpoint of mass productivity.

Other laser reproduction holograms such as a Fresnel hologram, a Fraunhofer hologram, a lensless Fourier transform hologram, and an image hologram,
And a white light reproducing hologram such as a rainbow hologram, and further, a color hologram, a computer hologram, a hologram display, a multiplex hologram, a holographic stereogram, a holographic diffraction grating, etc., utilizing those principles can be used.

The diffraction grating layer can be constituted by the holographic diffraction grating utilizing a hologram recording means. However, by mechanically creating a diffraction grating using an electron beam lithography apparatus or the like, the diffraction grating layer can be calculated. A diffraction grating from which arbitrary diffracted light can be obtained can be created. As a photosensitive material for forming a diffraction grating or a hologram for recording interference fringes, silver salt, gelatin dichromate, thermoplastic, diazo photosensitive material, photoresist, ferroelectric material, photochromic material, and thermochromic material. Chromics materials, chalcogen glass and the like can be used.

In the present invention, as a material for forming the diffraction grating layer and the hologram layer, thermoplastic resins such as polyvinyl chloride, methyl methacrylate, acrylic resin, polystyrene, polycarbonate, etc., unsaturated polyester, melamine, epoxy, polyester ( Meth) acrylates,
Cured thermosetting resin such as urethane (meth) acrylate, epoxy (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, triazine acrylate, or the above heat A mixture of a plastic resin and a thermosetting resin can be used.

Further, as a material for forming the diffraction grating layer or the hologram layer, a thermoformable substance having a radically polymerizable unsaturated group can be used, and the following two types are available. (1) Those having a radical polymerizable unsaturated group in a polymer having a glass transition point of 0 to 250 ° C. More specifically, a polymer obtained by polymerizing or copolymerizing a compound represented by the following (1) to (4) with a radically polymerizable unsaturated group introduced by the following methods (a) to (d) may be mentioned. it can.

Monomers having a hydroxyl group: N-methylolacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2
-Hydroxybutyl methacrylate, 2-hydroxy-
3-phenoxypropyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate and the like.

Monomers having a carboxyl group: acrylic acid, methacrylic acid, acryloyloxyethyl monosuccinate and the like.

A monomer having an epoxy group: glycidyl methacrylate and the like.

Monomer having an aziridinyl group: 2-
Aziridinylethyl methacrylate, allyl 2-aziridinylpropionate and the like.

Monomers having an amide group: acrylamide, methacrylamide, diacetone acrylamide, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like.

A monomer having a sulfone group: 2-acrylamido-2-methylpropanesulfonic acid and the like.

A monomer having an isocyanate group:
An adduct of a diisocyanate such as a 1 mol to 1 mol adduct of 2,4-toluene diisocyanate and 2-hydroxyethyl acrylate, and a radical polymerizable monomer having an active hydrogen.

In order to adjust the glass transition point of the above-mentioned copolymer and to adjust the physical properties of the cured film, the above-mentioned compound and the following monomers copolymerizable with this compound are used. It can also be polymerized. As copolymerizable monomers, methyl methacrylate, methyl acrylate,
Ethyl methacrylate, ethyl acrylate, propyl methacrylate, propyl acrylate, butyl methacrylate, butyl acrylate, isobutyl methacrylate, isobutyl acrylate, t-butyl methacrylate, t-butyl acrylate, isoamyl methacrylate, isoamyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, 2-ethylhexyl methacrylate And 2-ethylhexyl acrylate.

Next, the polymer obtained as described above is reacted by the following methods (a) to (d) to introduce a radical polymerizable unsaturated group, thereby obtaining a resin for forming a diffraction grating or a hologram. A forming resin can be obtained.

(A) In the case of a polymer or copolymer of a monomer having a hydroxyl group, a monomer having a carboxyl group such as acrylic acid or methacrylic acid is subjected to a condensation reaction.

(B) In the case of a polymer or copolymer of a monomer having a carboxyl group or a sulfone group, the above-mentioned monomer having a hydroxyl group is subjected to a condensation reaction.

(C) In the case of a polymer or copolymer of a monomer having an epoxy group, an isocyanate group or an aziridinyl group, the above-mentioned monomer having a hydroxyl group or monomer having a carboxyl group is subjected to an addition reaction. Let it.

(D) In the case of a polymer or copolymer of a monomer having a hydroxyl group or a carboxyl group, a monomer having an epoxy group or a monomer having an aziridinyl group, a diisocyanate compound and a hydroxyl group-containing acrylic acid One to one mole of the adduct of the ester monomer is subjected to an addition reaction.

To carry out the above reaction, it is preferable to add a trace amount of a polymerization inhibitor such as hydroquinone and to carry out the reaction while sending dry air.

(2) A compound having a melting point of 0 to 250 ° C. and having a radically polymerizable unsaturated group. Specific examples include stearyl acrylate, stearyl methacrylate, triacryl isocyanurate, cyclohexanediol diacrylate, cyclohexanediol dimethacrylate, spiroglycol diacrylate, spiroglycol dimethacrylate, and the like.

The resin for forming a diffraction grating or the resin for forming a hologram in the present invention includes the above (1)
(2) can be used as a mixture, and a radically polymerizable unsaturated monomer can be added thereto. This radically polymerizable unsaturated monomer is used to increase the crosslink density and improve heat resistance upon irradiation with ionizing radiation. In addition to the above-mentioned monomers, ethylene glycol diacrylate, ethylene glycol dimethacrylate , Polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, pentaerythritol tetraacrylate, Pentaerythritol tetramethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipenta Risuri hexaacrylate, dipentaerythritol hexa methacrylate,
Ethylene glycol diglycidyl ether diacrylate, ethylene glycol diglycidyl ether dimethacrylate, polyethylene glycol diglycidyl ether diacrylate, polyethylene glycol diglycidyl ether dimethacrylate, propylene glycol diglycidyl ether diacrylate, propylene glycol diglycidyl ether dimethacrylate, polypropylene glycol Diglycidyl ether diacrylate, polypropylene glycol diglycidyl ether dimethacrylate, sorbitol tetraglycidyl ether tetraacrylate, sorbitol tetraglycidyl ether tetramethacrylate, and the like can be used. Such a monomer is preferably used in an amount of 0.1 to 100 parts by weight based on 100 parts by weight of the solid content of the copolymer mixture. The above-mentioned compounds can be sufficiently cured by an electron beam, but when cured by irradiation with ultraviolet light, benzoin ethers such as benzoquinone, benzoin, benzoin methyl ether, and halogenated acetophenones are used as sensitizers. And those that generate radicals upon irradiation with ultraviolet rays, such as viatyls.

In order to efficiently heat the magnetic recording layer in the present invention, it is preferable that the diffraction grating layer 34 or the hologram layer 34 has high thermal conductivity.
Here, the thermal conductivity κ of the resin constituting the diffraction grating layer 34 or the hologram layer 34 is 0.1 to 0.3 (J
oule / m · sec · k). Therefore, an additive having a thermal conductivity κ of 10 (Joule / m · sec · k) or more, for example, a plasticizer such as ethylene glycol, glycerin, dioctyl phthalate (κ is several hundred (Joule / m · sec.))
・ K)), oxidizing agents such as TiO ₂ , BeO, SiO ₂ (κ
It is preferable that the diffraction grating layer 34 or the hologram layer 34 contains several tens to several hundreds (Joule / m · sec · k).

The diffraction grating layer 34 or the hologram layer 34
Can be formed by a conventionally known method. For example, when the hologram is a relief hologram, a hologram master on which interference fringes are recorded in the form of irregularities is used as a press mold, and a hologram-forming resin sheet is placed on the hologram master, and the hologram master is heated by a means such as a heating roll. Is heated and pressed, and the hologram layer 34 having a relief forming surface can be obtained by a method of replicating the concave and convex pattern of the hologram master on the surface of the hologram forming resin sheet. When the hologram is a volume hologram, a photopolymer or the like is formed on the base material by coating, and is superimposed on a hologram base plate that has been prepared in advance, and is irradiated with a slit-shaped laser beam to be wound and copied. it can.
Thereafter, processing such as heat development may be performed. In any case, a large number of duplicate plates can be prepared, a random pattern can be prepared, and various measures can be taken so that each recording medium can hold an individual reproduced image as much as possible.

The magnetic recording medium 31 may include a thin film layer between the above-described diffraction grating layer 34 or hologram layer 34 and the magnetic recording layer 33. The thin film layer may be any one that more effectively expresses the diffraction or hologram effect, and a general reflective metal thin film is usually used. In the case where the hologram is a transparent hologram, any material may be used as long as it does not obscure a colored layer or a pattern on the magnetic recording layer 33 as described later. For example, a transparent material having a different refractive index from the diffraction grating layer 34 or the hologram layer 34 is used. , Thickness 2
A reflective metal thin film layer having a thickness of not more than 00 °.

In the former case, the refractive index of the transparent material may be larger or smaller than that of the diffraction grating layer 34 or the hologram layer 34, but the difference in the refractive index is 0.1 or more, preferably 0.5 or more. The value of the refractive index is preferably 1.0 or more. As described above, by providing the transparent thin film layers having different refractive indices, a diffraction or hologram effect can be exhibited, and an effect of not hiding the coloring or the pattern of the lower layer can be obtained.

The latter case is a reflective metal thin film, but has a thickness of 200 ° or less, so that the transmittance of the light wave is large, so that it exhibits not only the diffraction or hologram effect but also the display portion non-hiding effect. I do. That is, when a light wave passes through a reflective metal thin film, its amplitude sharply decreases by exp (-2πK) per wavelength, so that when the film thickness exceeds 200 °, the transmittance becomes considerably small. Therefore, by setting the film thickness to 200 ° or less, the transmittance becomes sufficient and the diffraction or hologram effect can be exhibited. Further, by setting the film thickness to 200 ° or less, discomfort in appearance due to high-brightness silver white, which has been conventionally observed, is also eliminated.

The following materials (1) to (6) can be used as materials for forming the thin film layer as described above. (1) Transparent continuous thin film having a larger refractive index than the diffraction grating layer or the hologram layer There are two types of transparent thin films, one that is transparent in the visible region and one that is transparent in the infrared or ultraviolet region. Is Table 2
Are shown below. In the table, n indicates a refractive index (hereinafter, referred to as “n”).
(The same applies to (2) to (6)).

[0085]

[Table 1]

[0086]

[Table 2] (2) Transparent ferroelectric substance having a larger refractive index than the diffraction grating layer or the hologram layer Table 3 shows examples of the above transparent ferroelectric substance.

[0087]

[Table 3] (3) Transparent continuous thin film having a refractive index smaller than that of the diffraction grating layer or the hologram layer Table 4 shows examples of the transparent continuous thin film.

[0088]

[Table 4] (4) Reflective metal thin film having a thickness of 200 ° or less The reflective metal thin film has a complex refractive index, and the complex refractive index n * is represented by n * = n−iK. Here, n indicates a refractive index, and K indicates an absorption coefficient.

Table 5 shows the materials of the reflective metal thin film that can be used in the present invention, and also shows the values of n and K described above.

[0090]

[Table 5] In addition to the materials listed in Table 5 above, Sn, In, T
e, Ti, Fe, Co, Zn, Ge, Pb, Cd, B
Metals such as i, Se, Ga, and Rb can be used. Further, oxides and nitrides of the above metals can also be used,
Further, the metal, its oxide, nitride, and the like can be used alone or in combination of two or more. (5) A resin having a different refractive index from that of the diffraction grating layer or the hologram layer The resin may have a larger or smaller refractive index than the diffraction grating layer or the hologram layer. Table 6 shows these examples.
Shown in

[0091]

[Table 6] In addition to the resins listed in Table 6 above, general synthetic resins can be used, but a resin having a large difference in refractive index from the diffraction grating layer or the hologram layer is particularly preferable. (6) Laminated body obtained by appropriately combining the materials shown in the above (1) to (5) The combination of the above materials (1) to (5) is arbitrary, and the vertical positional relationship of each layer in the layer configuration Can also be arbitrarily selected.

Of the above thin film layers (1) to (6),
(4) The thickness of the thin film layer is preferably 200 ° or less,
The thickness of the thin film layer of (1) to (3) and (5) and (6) may be any range as long as the thin film layer can maintain transparency, and can be appropriately set depending on the material used. About 10 to 10000, preferably 100 to 5000
About Å.

The method of forming a thin film layer using the materials shown in the above (1) to (4) includes a vacuum deposition method, a sputtering method, a reactive sputtering method, an ion plating method, and an electroplating method. And other general thin film forming means can be used. When a thin film layer is formed using a material as described in the above (5), a general coating method or the like can be used. Further, when a thin film layer is formed using a material as shown in the above (6), the above means, methods and the like can be used in an appropriate combination.

When a material as shown in the above (5) is used, the material need not be a thin film as long as it is a transparent material.
A resin layer having a thickness of 0.5 μm or more, preferably 1.0 to 3.0 μm may be formed. In particular, by using a transparent type, it is possible to determine at a glance that the magnetic recording layer and the picture layer are laminated. Further, at the time of optical heating, the light directly reaches the magnetic recording layer, which is more effective.

The magnetic recording medium 31 includes the diffraction grating layer 3
4 or a protective layer on the hologram layer 34. The protective layer is formed on the diffraction grating layer 34 or the hologram layer 34 by laminating a synthetic resin film,
It can be carried out by an extrusion coating method or by applying a synthetic resin paint. The resin constituting the protective layer may be the same as the synthetic resin used for forming the above-described colored layer, in consideration of durability, heat resistance, adhesion to other layers, and the like, An ultraviolet / electron beam curable resin having high physical properties is more preferable.

As the ionizing radiation-curable resin for forming the protective layer, a mixed resin composition comprising a prepolymer, oligomer, and / or monomer having a weight unsaturated bond or an epoxy group in the molecule is used. . Specific examples of the above prepolymers and oligomers include unsaturated polyesters such as condensates of unsaturated dicarboxylic acids and polyhydric alcohols, and methacrylates such as polyester methacrylate, polyether methacrylate, polyol methacrylate, and melamine methacrylate. And acrylates such as polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polyol acrylate and melamine acrylate. Further, specific examples of the monomer include styrene,
Styrene monomers such as α-methylstyrene, acrylates such as methyl acrylate, 2-ethylhexyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, butyl acrylate, methoxybutyl acrylate, phenyl acrylate and the like , Methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, methoxyethyl methacrylate, ethoxymethyl methacrylate, phenyl methacrylate, 2- (N, N-diethylamino) ethyl acrylate, methacrylic acid -2- (N, N-dimethylamino) ethyl, 2- (N, N-dibenzylamino) acrylate
Substituted amino alcohol esters of unsaturated acids such as ethyl, 2- (N, N-dimethylamino) methyl methacrylate, 2- (N, N-diethylamino) propyl acrylate, and unsaturated acids such as acrylamide and methacrylamide Carboxylic acid amide, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, diacrylate compounds such as triethylene glycol diacrylate, dipropylene glycol diacrylate, Polyfunctional compounds such as ethylene glycol acrylate, propylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane trithioglycolate , Trimethylolpropane thio propylate, a polythiol compound having two or more thiol groups in the molecule such as pentaerythritol thioglycolate and the like are used. When the protective layer is formed of the ionizing radiation-curable resin as described above, in consideration of the coating suitability of the coating agent with the ionizing radiation-curable resin, usually, 5 to 5 of the above prepolymer or oligomer is used.
A mixed composition of 95% by weight and 95-5% by weight of the monomer and / or polythiol compound is utilized. Further, in the coating agent of the ionizing radiation curable resin, when the coating agent is cured by irradiation of ultraviolet rays, for example, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethyl meuram Monosulfide,
Of course, a photopolymerization initiator such as thioxanthone and a photosensitizer such as n-butylamine, triethylamine and tri-n-butylphosphine may be added, if necessary.

The coating method of the coating agent when forming the protective layer includes roll coating, curtain flow coating, wire bar coating, reverse coating, gravure coating, gravure reverse coating, air knife coating, kiss coating, blade coating, smooth coating, A known method such as comma coating can be used.

The curing in the formation of the protective layer with the ionizing radiation-curable resin may be performed by irradiating ultraviolet rays from a light source such as an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a black light lamp, a metal halide lamp, or a cockloft. 100 to 10 by various electron beam accelerators such as Walton type, Handigraph type, Resonant transformer type, Insulated core transformer type, Linear type, Dynamitron type, High frequency type
Electron beam irradiation with an energy of 00 keV, preferably 100 to 300 keV is used.

In order to improve durability and heat resistance, a powder such as Teflon powder, preferably having a softening point of 100 ° C. or higher and having a high transparency and a particle size of several μm, is used for the protective layer.
Further, fine powder of about submicron may be contained. Further, silicone, polyethylene wax or the like may be added to the protective layer to give the surface releasability.

The protective layer and the diffraction grating layer 34
Alternatively, a curable acrylic resin, a cellulose resin, a vinyl resin, or the like is provided between the hologram layer 34 and the hologram layer 34 in order to increase the adhesion between the two layers and increase the durability of the diffraction grating layer 34 or the hologram layer 34. An overprint layer may be provided. Further, between the above-mentioned thin film layer and the magnetic recording layer 33, vinyl chloride /
An anchor layer made of a vinyl acetate copolymer, an acrylic resin, a urethane resin or the like may be provided.

Further, the magnetic recording medium 31 may have an adhesive layer between each layer as needed. In this case, the adhesive layer is made of a vinyl chloride / vinyl acetate copolymer, an ethylene / vinyl acetate copolymer, a vinyl chloride / propionic acid copolymer,
After adding a plasticizer, a stabilizer, a curing agent, etc. to a binder such as a rubber-based resin, a cyanoacrylate resin, a cellulose-based resin, an ionomer resin, and a polyolefin-based copolymer, if necessary, a solvent or a diluent is sufficient. It can be formed by applying using a kneaded adhesive layer paint. The coating for the adhesive layer can be applied by a coating method such as a gravure method, a roll method, and a knife edge method. In particular, when an adhesive layer is provided on the magnetic recording layer, it is preferable that a thermoplastic resin be emulsified and applied and dried to form a heat-sealable adhesive layer in order to prevent re-dissolution of the magnetic recording layer.

[0102]

As described in detail above, according to the present invention, among magnetic recording media having a magnetic recording layer on a substrate, the magnetic material having a low Curie point is lower than the Curie point of the magnetic material having a low Curie point and is 1/1/2 of the Curie point. Since the magnetic recording layer is selectively heated in the temperature range of 2 or more, magnetic recording is performed while minimizing the influence of heat on the base even for a magnetic recording medium whose base is easily deteriorated and deformed by heat. The magnetic recording information can be recorded on the layer, and the issuance of the magnetic recording medium can be expedited, and a substrate that easily deteriorates and deforms due to heat can be used for the magnetic recording medium. When the magnetic recording medium is heated for the purpose of forgery or falsification, the base is deformed and becomes unusable, and forgery or falsification is difficult. In addition, the magnetic recording layer made of a high coercive force, low Curie point magnetic material and the magnetic recording layer made of a low coercive force, high Curie point magnetic material can have substantially the same or near saturation write current value. The same magnetic data can be recorded on the magnetic recording layer. Further, the magnetic recording layer has a multilayer structure, and the lower magnetic recording layer (substrate side) is made of a high coercive force, low Curie point magnetic material, and the upper magnetic recording layer is made of a low coercive force, high Curie point magnetic material. If
Forgers are less likely to notice the presence of the lower layer, and are less likely to cause troubles due to magnetic transfer, making forgery and alteration more difficult. The lower (substrate side) magnetic recording layer has a low coercive force and a high Curie point. When the upper magnetic recording layer is made of a high coercive force, low Curie point magnetic material,
Heating makes it easier to heat the upper layer directly, heat is concentrated on the upper layer and the heat diffusion to the lower layer is reduced, so the Curie point of the lower layer can be relatively low, damage by heat can be reduced, and the magnetic field strength ( The write current value can be reduced, and furthermore, the effect is obtained that it is difficult for the forger to notice the existence of the lower layer, and forgery and alteration are difficult.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a configuration of a magnetic recording device according to the present invention.

FIG. 2 is a view for explaining a heating unit of an optical heating system.

FIG. 3 is a diagram for explaining heating of a magnetic recording layer by a dielectric heating method.

FIG. 4 is a diagram for explaining another example of heating the magnetic recording layer by a dielectric heating method.

FIG. 5 is a schematic sectional view showing an example of a magnetic recording medium that can be used in the present invention.

FIG. 6 is a schematic sectional view showing another example of a magnetic recording medium that can be used in the present invention.

FIG. 7 is a schematic sectional view showing another example of a magnetic recording medium that can be used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 magnetic recording device 2 magnetic recording medium supply unit 3 heating unit 4 magnetic recording unit 5 cooling unit 6 magnetic recording medium discharge unit 11 light source 12 control unit 15 heating coil 16 magnetic recording head 17 Normal magnetic recording head 18: magnet for applying an alternating magnetic field 21, 31: magnetic recording medium 22, 32 ... base 23, 33 ... magnetic recording layer 23a, 33a ... first magnetic recording layer 23b, 33b ... second magnetic recording layer 34 ... Diffraction grating and / or hologram layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-48249 (JP, A) JP-A-4-34744 (JP, A) JP-A-60-166468 (JP, A) 55312 (JP, A) JP-A-50-71309 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/02 G11B 5/62 G11B 11/10

Claims (27)

(57) [Claims] 1. A magnetic recording apparatus for recording magnetic recording information on a magnetic recording layer of a magnetic recording medium having a magnetic recording layer on a substrate, wherein the magnetic recording layer has a multilayer structure, and at least the magnetic recording layer has a multilayer structure. The two layers are such that the magnetic material contained in one layer has a higher coercive force and a lower Curie point than the magnetic material contained in the other layer, and is lower than the Curie point of the magnetic material having a lower Curie point. A magnetic recording apparatus comprising: a heating unit that can selectively heat the magnetic recording layer of the magnetic recording medium in a temperature range equal to or higher than half the Curie point. 2. A magnetic recording device for recording magnetic recording information on a magnetic recording layer of a magnetic recording medium having a magnetic recording layer on a substrate, wherein one of the magnetic recording layers has a higher coercive force and a lower Curie point than the other. And a mixture of two or more magnetic materials having the following formulas:
2. A magnetic recording apparatus, comprising: a heating unit capable of selectively heating the magnetic recording layer of the magnetic recording medium in a temperature range equal to or higher than the temperature of 2. 3. A magnetic material having a Curie point difference of 100 ° C. or more and a coercive force difference of 2 times or more among the two or more magnetic materials contained in the magnetic recording layer. The magnetic recording apparatus according to claim 1, wherein the magnetic recording apparatus is used. 4. The magnetic recording apparatus according to claim 1, wherein the heating unit is a heating unit of a light heating type that irradiates an infrared ray or a laser beam to the magnetic recording layer. . 5. The magnetic recording apparatus according to claim 4, wherein a surface irradiated with a small area by infrared rays or a laser beam is scanned on the magnetic recording layer. 6. The heating device according to claim 1, wherein the heating unit is a direct resistance heating type heating unit that causes the magnetic recording layer itself to generate heat by passing an electric current directly to the magnetic recording layer. The magnetic recording device according to any one of the above. 7. The heating means is an indirect resistance heating type heating means for heating the magnetic recording layer by causing a current to flow through a heating body in contact with the magnetic recording layer to cause the heating body to generate heat. 4. The magnetic recording apparatus according to claim 1, wherein: 8. The heating element is a heating layer laminated on the magnetic recording medium so as to be adjacent to the magnetic recording layer, or a heating element that can be separated from and attached to the magnetic recording medium. The magnetic recording apparatus according to claim 7, wherein: 9. An induction heating method of heating the magnetic recording layer by heating the magnetic recording layer or a layer adjacent to the magnetic recording layer by applying an alternating magnetic field to the magnetic recording layer. 4. The magnetic recording apparatus according to claim 1, wherein the magnetic recording apparatus is a heating unit. 10. The dielectric heating type heating means for heating the magnetic recording layer by applying heat to the dielectric layer adjacent to the magnetic recording layer by applying an alternating electric field to the magnetic recording layer. The magnetic recording apparatus according to claim 1, wherein 11. The apparatus according to claim 1, wherein said heating means is integrated with a magnetic recording head.
The magnetic recording device according to any one of the above. 12. The heating means according to claim 1, wherein said heating means is a combination of a light heating method and any one of a direct resistance heating method, an indirect resistance heating method, an induction heating method and a dielectric heating method. The magnetic recording device according to claim 1. 13. The magnetic recording apparatus according to claim 1, wherein the heating means is provided on both sides of the magnetic recording medium. 14. The magnetic device according to claim 1, further comprising a cooling unit for cooling the magnetic recording medium downstream of the heating unit in a direction in which the magnetic recording medium is conveyed. Recording device. 15. The magnetic recording apparatus according to claim 1, further comprising a cooling unit for cooling a peripheral portion of the heating unit. 16. A magnetic recording layer having a multilayer structure in which a magnetic material contained in at least one of the two layers has a higher coercive force and a lower Curie point than the magnetic material contained in the other layer has a magnetic recording layer formed on a substrate. The magnetic recording layer of the magnetic recording medium provided is selectively heated in a temperature range lower than the Curie point of a magnetic material having a low Curie point and at least a half of the Curie point. A magnetic recording method, wherein magnetic recording information is recorded on a magnetic recording medium. 17. The method according to claim 17, wherein the magnetic recording layer of the magnetic recording medium having a magnetic recording layer containing a mixture of two or more magnetic materials having a higher coercive force and a lower Curie point than the other on a substrate is formed. In the magnetic material having a Curie point, magnetic recording information is recorded on the magnetic recording layer while being selectively heated in a temperature range lower than the Curie point and equal to or higher than half the Curie point. Magnetic recording method. 18. A magnetic material having a Curie point difference of 100 ° C. or more and a coercive force difference of 2 times or more among the two or more magnetic materials contained in the magnetic recording layer. 18. The magnetic recording method according to claim 16, wherein the magnetic recording method is performed. 19. The magnetic recording method according to claim 16, wherein the magnetic recording layer is heated by irradiating an infrared ray or a laser beam to the magnetic recording layer. 20. The magnetic recording method according to claim 19, wherein a small-area irradiation surface by infrared rays or a laser beam is scanned on the magnetic recording layer. 21. The magnetic recording layer according to claim 16, wherein a current is directly passed through the magnetic recording layer to generate heat in the magnetic recording layer itself, thereby heating the magnetic recording layer.
9. The magnetic recording method according to any one of items 8. 22. The magnetic recording layer according to claim 16, wherein an electric current is applied to a heating element in contact with the magnetic recording layer to cause the heating element to generate heat, thereby heating the magnetic recording layer.
The magnetic recording method according to any one of the above. 23. The heating element, wherein the heating element is a heating layer laminated on the magnetic recording medium so as to be adjacent to the magnetic recording layer, or a heating element that can be separated from and attached to the magnetic recording medium. 23. The magnetic recording method according to claim 22, wherein: 24. The magnetic recording layer is heated by applying an alternating magnetic field to the magnetic recording medium to generate heat in the magnetic recording layer or a layer adjacent to the magnetic recording layer. 19. The magnetic recording method according to claim 18. 25. The magnetic recording medium according to claim 16, wherein an alternating electric field is applied to the magnetic recording medium to generate heat in a dielectric layer adjacent to the magnetic recording layer, thereby heating the magnetic recording layer. The magnetic recording method according to any one of the above. 26. Irradiating the magnetic recording layer with an infrared ray or a laser beam, applying a current directly to the magnetic recording layer to generate heat in the magnetic recording layer itself, and applying a current to a heater in contact with the magnetic recording layer. Flowing the heating element to generate heat, applying an alternating magnetic field to the magnetic recording medium to generate heat in the magnetic recording layer or a layer adjacent to the magnetic recording layer, and applying an alternating electric field to the magnetic recording medium. 19. The magnetic recording layer according to claim 16, wherein the magnetic recording layer is selectively heated by a combination with any one of causing a dielectric layer adjacent to the magnetic recording layer to generate heat. Magnetic recording method. 27. The magnetic recording method according to claim 16, wherein the magnetic recording layer is heated from both sides of the magnetic recording medium.