JPH0354721A - Magnetic tape and its production - Google Patents

Abstract

PURPOSE:To prevent deterioration of output in a long wavelength region by specifying the ratio of residual magnetic flux density to saturation magnetic flux density in the longitudinal direction of a magnetic tape and specifying the relation between the coercive force determined by the saturation magnetization hysteresis curve in the longitudinal direction of the tape and the half width of the differential curve of the above-mentioned hysteresis curve at near the coercive force. CONSTITUTION:After forming a magnetic film on a nonmagnetic supporting body 1, the tape with the coating film not dried is passed through a magnetic field which is generated by a solenoid coil 4 and is oriented parallel to the longitudinal direction of the tape. By this constitution, the obtd. tape has the ratio Br/Bm >=0.80, wherein Br is the residual magnetic flux density and Bm is the saturation magnetic flux density in the longitudinal direction of the magnetic tape, and the ratio dHc/Hc <=0.3, wherein Hc is the coercive force determined by the saturation magnetization hysteresis curve in the longitudinal direction of the tape and dHc is the half width of the differential curve of the hysteresis curve at Hc. The obtd. tape has far better output in a short wavelength region than a conventional tape using needle-like iron oxide powder, and also the obtd. tape has equal output in a long wavelength region to that of conventional one.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magnetic tape used in video equipment and the like requiring high-density recording, and a method of manufacturing the magnetic tape. This paper focuses on compatibility with acicular iron oxide tapes as much as possible, and relates to magnetic tapes and magnetic tape manufacturing methods that have much better characteristics in the short wavelength region than conventional acicular iron oxide tapes. BACKGROUND OF THE INVENTION Magnetic recording has traditionally been developed using longitudinal magnetic recording methods that utilize in-plane magnetization of a magnetic recording medium. Most of the magnetic tapes currently in use use this longitudinal recording method.

Currently, acicular iron oxide and Notal magnetic powder are the mainstream as magnetic materials constituting the media.Also, alumina is used to increase coating strength and polish the magnetic head, and to lower electrical resistance and runnability. A magnetic film is obtained by adding carbon to stabilize the magnetic flux and a lubricant to improve runnability and durability, and then uniformly dispersing these materials in an organic binder.

In terms of output, tapes using metal magnetic powder are
This is more advantageous than tapes using acicular iron oxide, reflecting the magnitude of the saturation magnetization of magnetic powder. However, metal magnetic powder is highly reactive if left as it is, and its characteristics deteriorate as a result of environmental changes. Therefore, a protective layer is provided on the surface of the R-type powder.There is a difference in input/output characteristics between tapes using acicular iron oxide and tapes using metal powder due to the difference in coercive force. Therefore, the question of video equipment using each tape is that there is no compatibility.On the other hand, S-V
HS video cameras have been around for quite some time now, but the magnetic tape they use now uses acicular iron oxide, which has been used in conventional V}iS tapes. However, in order to improve the C/N ratio, high coercivity has been achieved by making the magnetic powder finer and doping the magnetic surface layer with cobalt. In S 1 V H S, the upper {(i 亙 conversion is maintained,
Tapes recorded with conventional V
Can be played on HS deck. Thanks to this upward compatibility, users seem to be migrating to S-VHS without any major confusion. It is considered that the existence of upwardly compatible tapes with better characteristics has greatly contributed to this.

As in the example above, the upward compatibility of next-generation VTRs with current models seems to be a very important factor for users, and we are interested in developing magnetic tape that will enable upward compatibility with VTRs. ．． ＋． We have carried out development while paying t.

In longitudinal recording, the magnetic powder in the coating film is required to be oriented in the running direction of the recording medium in order to reduce the increase in output. By the way, when thinking about creating tapes with even better characteristics while maintaining upward compatibility, it seems that the C/N ratio of tapes using acicular iron oxide currently in use is approaching its limit. ．． Furthermore, although there is no problem with the output of metal tapes, their current characteristics are different due to their high coercive force, making it difficult to be compatible with S-VHS tapes.

There is a need to create a tape that maintains this compatibility, provides a good CN ratio during high-density recording, and has excellent durability and environmental resistance.

On the other hand, a perpendicular magnetic recording system which is excellent in principle has been proposed in order to dramatically increase the recording density. For example, as a literature, Nikkei Electronics by Iwasaki August 7, 1978
There are day numbers p 100-111.

As a means to achieve high-density recording using this rectangular recording method, the use of hexagonal ferrite fine powder was published in Japanese Patent Application Laid-Open No. 6
This method is disclosed in JP-A No. 0-149105 and Japanese Patent Application Laid-open No. 149106-1983. Barium ferrite magnetic powder is said to be able to obtain good output and CN ratio in short wavelength recording by utilizing the principle of perpendicular magnetic recording. For example, the literature includes Toshiba Review by Yokoyama et al. (vol. 40, 13).
No.) There are P1111-1114. Problem to be Solved by the Invention However, when using the barium ferrite magnetic powder shown in the literature, although the output in the short wavelength region is comparable to that of metal powder coated tape, the output deteriorates significantly in the long wavelength region. Met.

Furthermore, even if conventional longitudinal direction processing is performed (see Figure 2,
6 in the figure represents an orientation device using permanent magnets. Regarding other horizontal sections, explanations of the same configurations as in Figure 1 are omitted. )
At present, the squareness ratio obtained from the hysteresis curve is about 0.6, which is not good because the orientation returns. Therefore, compared to conventional tapes using acicular iron oxide, there was a problem in output in the long wavelength region.

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording medium of the present invention uses magnetic powder having a plate-like shape to prepare a magnetic paint, and runs a substrate to apply the paint to the substrate. After coating the magnetic powder on top, the easily magnetized magnetic powder in the paint is oriented in the running direction of the substrate, so that the ratio of the residual magnetic flux density Br in the longitudinal direction of the magnetic tape to the saturated magnetic flux density Bm is 0. .80 or more, and the ratio dHc/ is calculated from the coercive force Hc obtained from the saturation magnetic hysteresis curve in the longitudinal direction of the tape and the half-value width dHc of the differential curve of the saturated magnetic hysteresis curve near the coercive force.
The magnetic tape shall have an H c value of 0.3 or less. In order to solve the above-mentioned problems, the method for manufacturing a magnetic tape of the present invention involves forming a magnetic film on a non-magnetic substrate, and then inserting the magnetic tape into an oriented magnetic field parallel to the longitudinal direction of the magnetic tape generated by a solenoid or coil. By passing the magnetic film in an undried state, the ratio B r / B m between the residual magnetic flux density Br in the longitudinal direction of the tape and the saturation magnetic flux density Bm is 0.80 or more, and the saturated magnetic flux H in the longitudinal direction of the tape is The ratio d H c / calculated from the coercive force Hc obtained from the hysteresis curve and the half-width dHc of the differential curve of the saturated magnetic hysteresis curve near the coercive force.
The present invention is configured to provide a method for manufacturing a magnetic tape having an H c value of 0.3 or less. Function: The magnetic tape of the present invention has the above-described configuration, which increases the residual magnetic flux density in the longitudinal direction on the long wavelength side to cover the output of the SVHS tape, and utilizes the characteristics of magnetic powder that energy loss is small in the short wavelength region. The method for manufacturing a magnetic tape of the present invention, which obtains a magnetic tape that exceeds the output of S-VHS tape and is comparable to the output of metal-coated tape, suppresses the reorientation of the axis of easy magnetization of the magnetic powder by the above-described structure, Even when using plate-shaped magnetic powder, high squareness ratio and low d
A manufacturing method for obtaining an Hc/Hc magnetic tape is provided. EXAMPLE Hereinafter, an example of the magnetic tape and method for manufacturing the magnetic tape of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged longitudinal cross-sectional view of a main part of the method for manufacturing a magnetic tape of the present invention. 1 is a non-magnetic substrate, 2 is a guide pole, 3 is a coating section, 4 is a solenoid coil, and 5 is a drying section. In Fig. 1, solenoid coil 4 is configured so that effective longitudinal orientation without reorientation can be achieved even when plate-shaped magnetic powder is used.The magnetic powder used in the examples will be described below. (Magnetic powder used in Example 1) Magnetic powder is a composite of hexagonal ferrite and Subinel type ferrite, which has a magnetoplumbite type structure and whose axis of easy magnetization is perpendicular to the plate surface of the particle, and is a powder. Among the elements that take care of
The ratio is larger than I2 Average particle diameter Average particle diameter/average thickness Powder coercive force Saturation magnetization Nitrogen adsorption amount 0.06 μm 5 8000e 6 0 e mu / g 40 bo/g (fR used in Example 2 powder) MO nFe203 (M is Ba, Pb, S
"Represented by a magnetoplumbite structure represented by any one element selected from the following, where n is 5 to 6).
Average grain size of 0.07 μm Average diameter/average thickness 5 Coercive force 8200e Saturation magnetization 63 emu/g Nitrogen adsorption star
38n{/g (magnetic powder used in Example 3) BaFe IO. 6CoO. 7Ti0.7019 composition V Average particle size 0.05 μm Average particle size/average thickness 3 Powder coercive force 8000e Saturation magnetization 5 5 e m 11 /
g Nitrogen adsorption 35rI{/g (Example 4
(Magnetic powder used for) Average particle size of magnetic powder containing iron carbide o. 07μm Average particle size/average thickness 5 Powder coercive force 7900e Saturation magnetization 90emu/g Nitrogen adsorption amount
35 Bo/g Using the above magnetic powder, a magnetic paint was produced using a sand mill after hard kneading using Niichi Gu.

The paint combination is shown below.

・Magnetic powder ・・・・・・ 200 parts・
Vinyl chloride polymer: 15 parts, polyurethane: 15 parts, carbon: 6 parts, alumina: 8 parts Lubricant
・・・・・・ 2 parts/solvent toluene
・・・・・・ 180 parts・Nclohexanone
・・・・・・ 180 parts/hardening agent
- Old... 12 parts of the obtained paint was milled and coated using a blade coater with a spacing of 35 μm between the blade and the non-magnetic substrate. A polyethylene terephthalate film with a thickness of 14 μm was used as the nonmagnetic substrate.

Before the coated TK'L film was dry, a longitudinal magnetic field orientation treatment using a solenoid coil was performed. After the paint film dries, the tape is wound up and calendered (80°C.35kg/cm
) was carried out. Thereafter, 20 special hardening treatments were performed to obtain Examples 1 to 4. The magnetic tape of the example was measured using a vibrating sample magnetometer (maximum magnetic field LOKOe). In addition, the electromagnetic conversion characteristics were measured at a relative speed of 5.8 m/sec. Flight L light henode (gamble length 0.25μm, trunk width 48μm
, 18 windings). The measurement frequency is 2 5
0MHz. There are three points: 4.2MHz and 7Mllz.

In Comparative Examples 1 to 4, samples without orientation treatment were prepared using the same magnetic coating T4 as in Examples 1 to 4. after that,
Evaluations similar to those in Examples were performed.

Comparative Example 5 was a commercially available tape for S-VHS made by our company. Table 1 summarizes the measurement results of the magnetic properties and the tape surface.

The difference in magnetic properties in the longitudinal direction is remarkable. Note that 〃 represents the longitudinal direction of the medium, and represents the thickness direction of the medium. The output is the optimum recording Tj. of Comparative Example 5. ? The values are shown at JL, and the relative values are shown with the output of Comparative Example 5 set to O decibels. (
Table 2) As is clear from Table 2, the magnetic recording medium of the present invention has S
- It is determined that the tape is upwardly compatible with VHS tapes.

As described above, by using the magnetic tape and magnetic tape manufacturing method of the present invention, it is possible to obtain a magnetic tape that is much better in short wavelength output than the conventional acicular iron oxide tape and has an equivalent output in long wavelength output. be able to. Effects of the Invention As described above, the method for manufacturing magnetic tape and magnetic tape of the present invention is to form a magnetic film on a non-magnetic substrate, and then generate a magnetic film parallel to the longitudinal direction of the magnetic tape generated by a solenoid or a coil. By passing the magnetic film in an undried state through an alignment magnetic field, the ratio B r / B m between the residual magnetic flux density Br in the longitudinal direction of the tape and the saturation magnetic flux density Bm is 0.80 or more, and The ratio d H c / calculated from the coercive force Hc obtained from the saturation magnetic hysteresis curve and the half-value width dHc of the differential curve of the saturated magnetic hysteresis curve near the coercive force.
A magnetic tape having an H c value of 0.3 or less is obtained.

According to the present invention, it is possible to produce a magnetic tape that is much better at short wavelength output than conventional acicular iron oxide tape and has an equivalent output at long wavelength output, and takes into account compatibility with conventional VTR decks. A new VTR with even higher performance
This is an extremely useful invention industrially.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a magnetic tape manufacturing method according to an embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a main part of a conventional magnetic tape manufacturing method. 1...Nonmagnetic substrate, 2...Guide ball, 3...
Coating section, 4 solenoid coils, 5... drying section,
6...Permanent magnet.

Claims (1)

[Scope of Claims] (1) A magnetic paint is prepared using magnetic powder having a plate-like shape, and after the paint is coated on the base by running the base, the axis of easy magnetization of the magnetic powder in the paint is determined. In a magnetic tape obtained by oriented in the running direction of the substrate, the ratio Br/Bm of the residual magnetic flux density Br in the tape longitudinal direction to the saturated magnetic flux density Bm of the magnetic tape is 0.80 or more, and the saturation in the tape longitudinal direction A magnetism characterized in that the value of the ratio dHc/Hc calculated from the half-value width dHc of the differential curve of the coercive force Hc obtained from the magnetic hysteresis curve and the saturated magnetic hysteresis curve near the coercive force is 0.3 or less. tape. (3) The plate-shaped magnetic powder is a composite of hexagonal ferrite and spinel ferrite, which has a magnetoplumbite structure and whose axis of easy magnetization is perpendicular to the plate surface of the particle. , and in the elements constituting the powder, the ratio of Fe (iron)/Ba (barium) is 1
Claim (1) characterized in that the magnetic powder is larger than 2.
) magnetic tape. (3) The plate-shaped magnetic powder is Mo, nFe20
3 (where M is an element selected from Ba, Pb, and Sr, and n is 5 to 6) A magnetic powder made by coating hexagonal ferrite with a magnetoplumbite structure coated with spinel ferrite. The magnetic tape according to claim 1, characterized in that: (4) Magnetic powder having a plate-like shape is AFe(12-X)MXO19 (where A is one or more elements selected from Ba, Sr, and Pb, and M is In, Zn-Ge, and Zn- Nb, Zn-
The composition according to claim (1), characterized in that it has a composition of one or more elements or a combination of elements of V, Co-Ti, and Co-Ge, and X represents a number from 1 to 2.5, respectively. Magnetic tape. (5) The magnetic tape according to claim (1), wherein the plate-shaped magnetic powder contains iron carbide. (6) After forming a magnetic film on a non-magnetic substrate, the magnetic film is passed in an undried state through an oriented magnetic field parallel to the longitudinal direction of the magnetic tape generated by a solenoid or coil. The ratio Br/Bm between the residual magnetic flux density Br and the saturated magnetic flux density Bm is 0.80 or more, and the coercive force Hc obtained from the saturation magnetic hysteresis curve in the longitudinal direction of the tape and the saturated magnetic hysteresis curve near the coercive force The value of the ratio dHc/Hc calculated from the half-width dHc of the differential curve is 0.3.
A method for manufacturing a magnetic tape as follows.