JPH11219512A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a satisfactory traveling stability and a satisfactory output weveform by providing a coating layer at least including a magnetic layer on the surface of one side of a base film and a back coating layer on the opposite surface and making the sum of the coating layer of the magnetic layer side and the back coating layer that is, the total thickness of all coatings equal to or thinner than that of the base film. SOLUTION: A magnetic layer as an uppermost layer including ferromagnetic powder and a binder is provided on a base film. Moreover, an intermediate layer at least including magnetic powder and/or non-magnetic powder and a binder may be provided between the base film and the magnetic layer. Furthermore, a back coating layer is provided on the back of the film. Then, when the thickness of all coating layers existing on the surface on which the magnetic layer of the base film of the magnetic layer side is provided, is defined as DM, the thickness of the back coating layer is defined as DB, the thickness of the base film is defined DF, this magnetic medium is made to satisfy the relation of (DM+DB)×1.1>=DF. When the magnetic madium does not satisfy this relation, a satisfactory traveling stability and a satisfactory output waveform are not obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium, and more particularly to a thin magnetic recording medium having good running stability and output waveform.

[0002]

2. Description of the Related Art In order to increase the recording capacity per volume, the total thickness of a magnetic tape tends to be reduced. As a method of reducing the thickness of the magnetic tape, there are a method of reducing the thickness of the coating film layer and a method of reducing the thickness of the base film. When thinning the base film,
It is necessary to use a film having high rigidity in order to prevent the rigidity of the tape from being reduced, but there is a problem that the cost is high. In addition, there is a limit even when such a base film is used, and there is a problem in running properties and the like. Further, if the thickness of the base film is too thin as compared with the magnetic layer, for example, in the case of thinning the total thickness of the magnetic tape to 6 μm or less, there is a problem that cupping easily occurs, and good contact with the recording / reproducing head is required. This may hinder the output waveform.

Accordingly, an object of the present invention is to provide a thin magnetic recording medium having good running stability and output waveform.

[0004]

The present inventors have studied and found that, in a thin magnetic tape, the sum of the coating layer and the back coat layer on the magnetic layer side, that is, the total coating thickness is equal to or less than the thickness of the base film. It has been found that the above object can be achieved when the above-mentioned condition is satisfied.

The present invention has been made on the basis of the above findings. In a magnetic recording medium having at least a coating layer containing a magnetic layer on one surface of a base film and a back coat layer on the other surface, the following formula (1) ) Is provided. (D _M + D _B ) × 1.1 ≧ D _F (1) (where D _M is the thickness of the coating layer on the magnetic layer side, D _B is the thickness of the back coat layer, and D _F is the thickness of the base film)

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The magnetic recording medium of the present invention is provided with a magnetic layer as an uppermost layer containing at least a ferromagnetic powder and a binder on a non-magnetic support (base film). Further, an intermediate layer containing at least a magnetic powder and / or a nonmagnetic powder and a binder may be provided between the nonmagnetic support and the magnetic layer. further,
A back coat layer is provided on the back surface of the non-magnetic support. Further, in the magnetic recording medium of the present invention, in addition to the above-described non-magnetic support, intermediate layer, magnetic layer and back coat layer,
Further, a primer layer provided between the non-magnetic support and the intermediate layer or the back coat layer, and another magnetic layer provided for recording a servo signal or the like corresponding to a hard system using a long wavelength signal, etc. May be provided.

The magnetic recording medium of the present invention needs to satisfy the following expression (1). (D _M + D _B ) × 1.1 ≧ D _F (1) (where D _M is the thickness of the coating layer on the magnetic layer side, D _B is the thickness of the back coat layer, and D _F is the thickness of the base film) If the formula (1) is not satisfied, good running stability and output waveform cannot be obtained.

[0008] The coating layer on the magnetic layer side referred to here means all coating layers existing on the surface of the support on which the magnetic layer is provided, and not only the magnetic layer but also the intermediate layer and the other layers described above. It includes other layers such as a magnetic layer. Further, the back coat layer may be a single layer or a multilayer.

The magnetic recording medium of the present invention preferably satisfies the following expression (4). D _M + D _B ≧ D _F (4) (However, D _M , D _B , and D _F are the same as the above equation (1))

Further, the magnetic recording medium of the present invention preferably has a total thickness of 6 μm or less. If the thickness exceeds 6 μm, the recording capacity per volume cannot be increased. When the thickness is 6 μm or less, the effect of the present invention becomes remarkable by satisfying the above expression (1).

It is desirable that the magnetic recording medium of the present invention satisfies the following expression (2). 1 ≦ D = (D _M × D _B / D _T × W) × 10 ⁵ ≦ 10 (2) (where D _M and D _B are the same as the above formula (1), D _T is the total thickness of the medium, W is the width of the medium. When the above expression (2) is satisfied, the running stability and the like become better.

The magnetic recording medium of the present invention preferably satisfies the following expression (3), and more preferably, the thickness of the back coat layer is 1 μm or more. D _M ≦ D _B × 2 (3) (where D _M and D _B are the same as the above formula (1)) By making the back coat layer a certain thickness or more,
When the total thickness of the magnetic tape is reduced (for example, 6 μm or less)
Furthermore, cupping on the back coat layer side of the magnetic recording medium can be prevented.

Next, the respective layers constituting the magnetic recording medium of the present invention will be described by taking a multilayer magnetic recording medium as an example. First, the magnetic layer will be described. The magnetic layer is usually the uppermost layer of the magnetic recording medium, that is, a layer existing on the surface of the magnetic recording medium,
It can be formed using a magnetic paint containing ferromagnetic powder, a binder and a solvent as main components.

As the above ferromagnetic powder, for example, γ-Fe
₂ O ₃ , Co-coated γ-Fe ₂ O ₃ , Co-coated FeOx
(4/3 ≦ x <1.5) and the like, a ferromagnetic metal powder mainly composed of iron, a ferromagnetic hexagonal ferrite powder and the like. Specifically, Japanese Patent Application Laid-Open No. 9-3524
No. 6, JP-A No. 6-column 3-4 are used. Examples of the ferromagnetic metal powder include a ferromagnetic metal powder in which a metal content is 50% by weight or more and 60% or more of the metal content is iron. Further, it may be a magnetic layer provided by vapor deposition or sputtering using a vacuum technique, a coated magnetic layer, or a composite thereof.

The ferromagnetic iron oxide-based powder and the ferromagnetic metal powder mainly composed of iron preferably have a needle-like or spindle-like shape. The major axis length is preferably 0.05 to 0.20 μm, more preferably 0.05 to 0.20 μm.
0.15 μm, particularly preferably 0.05 to 0.10 μm
It is. The preferred needle ratio is 3 to 20, and the preferred X
The linear particle size is 130 to 250 °, and the preferable BET specific surface area is 30 to 70 m ² / g.

The coercive force (Hc) of the ferromagnetic powder is 120
To 210 kA / m, and particularly preferably 125 to
200 kA / m is preferred. Within the above range, the RF output in all wavelength regions can be obtained without excess and deficiency, and the overwrite characteristics are also good.

The ferromagnetic iron oxide powder and the ferromagnetic metal powder have a saturation magnetization (σs) of 100 to 180 Am ^2.
/ Kg, preferably 110 to 160 Am
It is preferably ² / kg. The saturation magnetization of the ferromagnetic hexagonal ferrite powder is 30 to 70 Am ² / kg.
And particularly preferably 45 to 70 Am ² / kg. Within the above range, a sufficient reproduction output can be obtained.

In particular, the ferromagnetic powder has a coercive force of 1
25 to 200 kA / m and saturation magnetization of 120 to 170
Am ² / kg, major axis length 0.2 μm or less, specific surface area 45 m
It is preferable to use an acicular ferromagnetic metal powder mainly composed of iron and having a concentration of ² / g or more.

Further, the ferromagnetic powder contained in the magnetic paint used for forming the magnetic layer may contain a rare earth element or a transition metal element as required.

The magnetic paint used for forming the magnetic layer may contain a non-magnetic powder. As such a nonmagnetic powder, the same nonmagnetic powder as that used for the intermediate layer described later is used. The intermediate layer may be a continuous thin film formed by sputtering or vapor deposition using a vacuum technique, or may be a composite of a coating film and a continuous thin film. In addition,
In this case, the continuous thin film is converted as a coating film thickness.

The magnetic paint used for forming the magnetic layer may contain carbon black. Examples of such carbon black include thermal black, channel black, lamp black, furnace black, acetylene black and the like, and details thereof are described in “Carbon Black Handbook” (edited by Carbon Black Association).

Examples of the binder used in the magnetic paint for forming the magnetic layer include a thermoplastic resin, a thermosetting resin, and a reactive resin, and can be used alone or in combination. Specific examples of the binder include vinyl chloride copolymers, polyurethanes, polyesters, nitrocellulose, epoxy resins and the like. In addition, JP-A-57-162128, page 2, upper right column, No. 19 From the line to the lower right column of the second page, the resin, etc. described in the 19th line and the like can be mentioned. Further, the binder may contain a polar group for improving dispersibility and the like. Particularly, a vinyl chloride copolymer and a polyurethane containing a polar group such as a sulfonic acid group are preferably used. The mixing ratio of the binder is 5 to 2 with respect to 100 parts by weight of the ferromagnetic powder.
It is preferably 00 parts by weight, more preferably 5 to 70 parts by weight.

Solvents contained in the magnetic paint used for the magnetic layer include ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents and chlorinated hydrocarbon solvents. Specifically, the solvents described on page 3, lower right column, line 17 to page 4, lower left column, line 10 of JP-A-57-162128 can be used. The mixing ratio of the solvent is preferably 80 to 500 parts by weight, more preferably 100 to 350 parts by weight, based on 100 parts by weight of the ferromagnetic powder.

The magnetic coating material used for forming the magnetic layer includes a usual magnetic material such as a dispersing agent, a lubricant, an abrasive, an antistatic agent, a rust inhibitor, a fungicide, a fungicide and a curing agent. Additives used for the recording medium can be added as needed. Specific examples of the above additives include the above-mentioned JP-A-57-1.
No. 62128, page 2, lower left column, line 6 to page 2, lower right column, line 10 and page 3, lower left column, line 6 to page 3, upper right column, line 18
Various additives described in the column and the like can be mentioned.

The thickness of the magnetic layer is 0.05 to 2.0 μm
Is preferable, and particularly preferably 0.05 to 0.3 μm. When the thickness of the magnetic layer is within the above range, the balance between durability and output stability is excellent, which is preferable.

In order to prepare a magnetic paint, for example, the above ferromagnetic powder and the above binder are put into a Nauta mixer or the like together with a part of a solvent and premixed to obtain a mixture. The obtained mixture is continuously added. After kneading with a pressure kneader or the like, diluting with a part of the solvent, dispersing using a sand mill or the like, mixing additives such as a lubricant, filtering, and further curing agent such as polyisocyanate and residual And the like.

Next, the intermediate layer provided between the nonmagnetic support and the magnetic layer will be described. The intermediate layer is a layer containing at least a magnetic powder and / or a nonmagnetic powder and a binder, and may be a magnetic layer or a nonmagnetic layer. The intermediate layer is a magnetic powder and / or a non-magnetic powder,
It is formed using a paint containing a binder and a solvent as main components (hereinafter also referred to as an intermediate paint). The purpose of providing the intermediate layer is to improve magnetostatic characteristics and surface smoothness.

As the above non-magnetic powder, Japanese Patent Application Laid-Open No. 9-35
No. 246, column 9, line 44 to column 10, line 7 can be used.

As the magnetic powder, a ferromagnetic powder is preferably used. As the ferromagnetic powder, both a soft magnetic powder and a hard magnetic powder are preferably used. The same hard magnetic powder as the ferromagnetic powder used for forming the magnetic layer is used.

The above magnetic powder or non-magnetic powder may contain a rare earth element or a transition element as required. In order to improve the dispersibility and the like of the magnetic powder or non-magnetic powder, the powder may be subjected to the same surface treatment as the ferromagnetic powder contained in the magnetic paint used for forming the magnetic layer.

It is desirable that the intermediate paint contains carbon black. As such carbon black, those similar to the carbon black used for the magnetic layer are used.

As the binder contained in the intermediate paint, the same binder as that used in the magnetic layer is used. The mixing ratio of the binder is 10
5 to 200 parts by weight, preferably 5 to 200 parts by weight,
70 parts by weight are more preferred.

As the solvent contained in the intermediate paint used for forming the intermediate layer, the same solvent as that contained in the magnetic paint used for forming the magnetic layer is used. The mixing ratio of the solvent is preferably 80 to 500 parts by weight, and more preferably 100 to 500 parts by weight based on 100 parts by weight of the nonmagnetic powder.
More preferred is 350 parts by weight.

[0034] In addition, the above intermediate paint, if necessary,
Additives that are added to the magnetic paint used to form the magnetic layer can be added.

The thickness of the intermediate layer is preferably from 0.1 to 2.5 μm, particularly preferably from 0.2 to 2.0 μm. Within the above range, sufficient bending rigidity can be obtained in the magnetic recording medium.

In order to prepare the intermediate coating, for example, the magnetic powder and / or the nonmagnetic powder and the binder are put into a Nauta mixer or the like together with a part of the solvent, and premixed to obtain a mixture. The resulting mixture was kneaded with a continuous pressure kneader or the like, then diluted with a part of the solvent, dispersed using a sand mill or the like, and then mixed with additives such as a lubricant.
A method of filtering and further mixing a curing agent and the remaining solvent can be used.

As the non-magnetic support (base film) used in the magnetic recording medium of the present invention, a generally known one can be used without any particular limitation. Specifically, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide (PA) and the like are preferably used, and details thereof are described in JP-A-9-35246, column 2, lines 30 to 42. I have. The thickness of the non-magnetic support (base film) is desirably 1 μm or more as described above.

The back coat layer provided on the back surface of the non-magnetic support in the magnetic recording medium of the present invention can be formed using a known back coat paint without any particular limitation.

The magnetic recording medium of the present invention can be applied as a magnetic tape such as an audio tape, an 8 mm video tape, a data storage tape for a computer, or a magnetic recording medium such as a floppy disk.

Next, an outline of a method for manufacturing the multilayer magnetic recording medium of the present invention having an intermediate layer will be described. First, an intermediate paint for forming the intermediate layer and a magnetic paint for forming the magnetic layer are prepared. Next, an intermediate paint and a magnetic paint are applied simultaneously on the non-magnetic support by a wet-on-wet method so that the dry thicknesses of the intermediate layer and the magnetic layer are within the above ranges, respectively. A coating film for the magnetic layer is formed. That is, the magnetic layer is preferably applied and formed when the intermediate layer is wet. The coating speed at this time is 50-100.
It is desirable to set it to 0 m / min.

Next, the obtained coating film is subjected to a magnetic field orientation treatment, and then dried and wound up. Thereafter, after performing a calendering treatment, a back coat layer is further formed as necessary. The back coat layer may be a known combination of carbon and a binder, or may be a metal or an oxide thereof using sputtering, vapor deposition, or the like. Further, the composite may be used. In some cases, the back coat layer may be formed before performing the calendering treatment, and thereafter, the magnetic layer and the back coat layer may be calendered together. Then
If necessary, for example, when obtaining a magnetic tape, 4
Aging treatment is performed at 0 to 70 ° C. for 3 to 72 hours, and slit to a desired width.

The above simultaneous multi-layer coating method is described in JP-A-5-73.
No. 883, column 42, line 31 to column 43, line 31, etc., which is a method of applying a magnetic paint for forming a magnetic layer before the intermediate paint for forming the intermediate layer dries. Since the interface between the intermediate layer and the magnetic layer is smooth and the surface properties of the magnetic layer are good, the dropout is small, high density recording is possible, and the coating film (intermediate layer and magnetic layer) is durable. A magnetic recording medium having excellent properties can be obtained.

The magnetic field orientation treatment is performed before the intermediate paint and the magnetic paint are dried. For example, when the magnetic recording medium of the present invention is a magnetic tape, the magnetic paint is oriented in a direction parallel to the magnetic paint application surface. About 40 kA / m or more, preferably about 80 to
It can be performed by a method of applying a magnetic field of 800 kA / m, a method of passing an intermediate paint and a magnetic paint through a solenoid of 80 to 800 kA / m in a wet state, or the like.

The drying treatment can be performed, for example, by supplying a heated gas. At this time, the degree of drying of the coating film can be controlled by controlling the temperature of the gas and the amount of the supplied gas. As the drying conditions, for example, the temperature of hot air is set to 3
It is preferable that the temperature is 0 to 120 ° C., the wind speed is 5 to 35 m / sec, and the drying time is 1 to 60 seconds.

The calendering treatment can be performed by a super calendering method in which two rolls such as a metal roll and a cotton roll or a synthetic resin roll, a metal roll and a metal roll are passed.

In the production of the magnetic recording medium of the present invention, a finishing step such as a polishing or cleaning step for the surface of the magnetic layer can be performed, if necessary. Further, the application of the intermediate paint and the magnetic paint can also be carried out by a generally known sequential multilayer coating method.

[0047]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples and the like.

Example 1 <Preparation of Magnetic Recording Medium> The following components (except for the curing agent) were kneaded in a kneader, then dispersed in a stirrer, and finely dispersed in a sand mill. After filtration through a 1 μm filter, a curing agent was finally added to prepare a magnetic paint, an intermediate paint and a back coat paint having the following compositions.

(Magnetic paint)-100 parts by weight of an acicular ferromagnetic metal powder mainly composed of iron [Fe: Co: Al: Y: Ba = 70: 25: 2: 2: 1] [major axis length: 0. 7 μm, axial ratio: 5, coercive force: 160 kA / m (2010 Oe), saturation magnetization: 142 Am ² / kg, specific surface area: 56 m ² / g, X-ray particle size: 0.01 4 μm] Alumina (abrasive, average 8 parts by weight ・ Carbon black 0.5 parts by weight (average primary particle diameter: 0.018 μm) ・ Vinyl chloride copolymer (binder) 10 parts by weight (average degree of polymerization: 280, epoxy (Group content: 1.2%, sulfonic acid group content: 8 × 10 ⁻⁵ mol / g) Polyurethane (binder): 7 parts by weight (number average molecular weight: 25000, sulfonic acid group content: 1.2 ×) 10 ^-4 mol / g, and a glass transition point: 45 ° C.) · scan Aric acid (lubricant) 1.5 parts by weight-2-ethylhexyl oleate (lubricant) 2 parts by weight-Polyisocyanate (curing agent) 5 parts by weight [Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd., solid 75%]-120 parts by weight of methyl ethyl ketone-80 parts by weight of toluene-40 parts by weight of cyclohexanone

(Intermediate paint) 100 parts by weight of acicular α-Fe ₂ O ₃ [average particle size (major axis length): 0.12 μm, axial ratio: 10, specific surface area: 48 m ² / g] Abrasive, primary particle size: 0.15 μm) 3 parts by weight ・ vinyl chloride copolymer (binder) 12 parts by weight (average degree of polymerization: 280, epoxy group content: 1.2%, sulfonic acid group content) 8 × 10 ⁻⁵ equivalents / g) 8 parts by weight of polyurethane (binder) (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalents / g, glass transition point: 45 ° C.) 1 part by weight of stearic acid (lubricant) 4 parts by weight of 2-ethylhexyl oleate (lubricant) 4 parts by weight of polyisocyanate (curing agent) [Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd., solid content 75%] ・ Methyl ethyl ketone 90 weight Toluene 60 parts Cyclohexanone 30 parts by weight

(Backcoat paint) 40 parts by weight of carbon black (antistatic agent, average primary particle diameter 0.018 μm) 50 parts by weight of polyurethane (binder) [trade name: Nipporan 2301, manufactured by Nippon Polyurethane Industry Co., Ltd.] 4% by weight of polyisocyanate (hardening agent) [Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd., solid content of 75%] Nitrocellulose 20 parts by weight Stearic acid 1 part by weight 140 parts by weight of methyl ethyl ketone 140 parts by weight of toluene 140 parts by weight of cyclohexanone

The obtained magnetic paint and intermediate paint were applied to a thickness of 2.
On a 7 μm polyamide support, the thickness of the intermediate layer is 1.8 μm.
m, and a multi-layer coating was performed simultaneously with a die coater so that the thickness of the magnetic layer became 0.2 μm. Next, while the magnetic layer was changed from the wet state to the dry state, a magnetic field orientation treatment was performed using a 0.5 T solenoid. Further, the coating film was dried by blowing hot air at 80 ° C. at a speed of 10 m / min in a drying furnace. After drying, calendering was performed, and the back coat paint was dried on the opposite side of the support to a thickness of 1.0%.
It was applied to a thickness of μm and dried at 90 ° C. to form a back coat layer. Finally, a magnetic tape was manufactured by slitting it to a width of 8 mm.

The total thickness of the magnetic tape was 5.7 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape is 3.3: 2.7, and the ratio of D _M to D _B × 2 is 2:
It was 2. The value of D was 4.4. The total thickness of the magnetic tape was measured using a step gauge, and the thickness of each layer was determined by taking a photograph of a cross section of the magnetic tape using a transmission electron microscope.

Example 2 The thickness of the magnetic layer was 1.3 μm,
A magnetic recording medium (magnetic tape) was obtained in the same manner as in Example 1 except that the thickness of the back coat layer was changed to 1.8 μm.

The total thickness of this magnetic tape was 7.6 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape is 5.4: 2.7, and the ratio of D _M to D _B × 2 is 3.
1: 3.6. The value of D was 5.6.

Example 3 The thickness of the back coat layer was set to 0.
A magnetic recording medium (magnetic tape) was obtained in the same manner as in Example 1 except that the thickness was 5 μm.

The total thickness of this magnetic tape was 5.2 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape was 2.75: 2.7, and the ratio of D _M to D _B × 2 was 2: 1. The value of D was 2.4.

Example 4 A base film having a thickness of 3
A polyethylene terephthalate support having a thickness of 1 μm, a back coat layer having a thickness of 1 μm, a magnetic layer having a thickness of 2 μm, no intermediate layer, and a tape width of イ ン チ inch (1 inch) were used.
A magnetic recording medium (magnetic tape) was obtained in the same manner as in Example 1 except that the thickness was changed to 2.7 mm).

The total thickness of the magnetic tape was 6.0 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape was 3.3: 3, and the ratio of D _M to D _B × 2 was 2: 2. The value of D was 2.6.

Example 5 A polyethylene naphthalate support having a thickness of 2.5 μm was used as a base film.
The thickness of the back coat layer was 1.5 μm, the thickness of the magnetic layer was 1.5 μm, no intermediate layer was provided, and the tape width was 3.
A magnetic recording medium (magnetic tape) was obtained in the same manner as in Example 1 except that the length was 81 mm.

The total thickness of the magnetic tape was 5.5 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape is 3.3: 2.5, and the ratio of D _M to D _B × 2 is 1.
5: 3. The value of D was 11.

Comparative Example 1 A 4.3 μm thick polyamide support was used as a base film. The thickness of the magnetic layer was 0.2 μm, the thickness of the intermediate layer was 0.9 μm, and the thickness of the back coat layer was 0.4 μm. A magnetic recording medium (magnetic tape) was obtained in the same manner as in Example 1 except for the above.

The total thickness of this magnetic tape was 5.8 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape was 1.65: 4.3, and the ratio of D _M to D _B × 2 was 1.1: 0.8. . The value of D is 0.95
Met.

Comparative Example 2 A magnetic recording medium (magnetic tape) was obtained in the same manner as in Comparative Example 1 except that the tape width was 3.81 mm. The value of D of this magnetic tape is 1.99.
Met.

[Comparative Example 3] The tape width was reduced to 1/2 inch (1
A magnetic recording medium (magnetic tape) was obtained in the same manner as in Comparative Example 1 except that the thickness was changed to 2.7 mm. The value of D of the magnetic tape was 0.60.

Reference Example 1 A base film having a thickness of 1
A magnetic recording medium (magnetic tape) was obtained in the same manner as in Example 1, except that a 0 μm polyethylene terephthalate support was used.

The total thickness of this magnetic tape was 13 μm. The ratio of (D _M + D _B ) × 1.1 to D _F of this magnetic tape is 3.3: 10, and the ratio of D _M to D _B × 2 is 2: 2.
Met. The value of D was 1.9.

Examples 1 to 5, Comparative Examples 1 to 3 and Reference Example 1
Examples 1 to 3, Comparative Example 1 and Reference Example 1 were Hi8VTR, and Examples 4 and 3
Is a VTR of ED-β, and Example 5 and Comparative Example 2 were respectively modified DDS drives, and the running stability and output waveform were measured according to the following methods. Table 1 shows the results. The Hi8VTR has a tape width of 8 mm and a V of ED-β.
TR has a tape width of 1/2 inch, and DDS drive has a tape width of 3.81 mm.

[Evaluation method] (Running stability) Commercially available Hi8 VTR, VTR of ED-β
And the DDS drive was modified, a jitter meter was connected, and the jitter was determined. The value of this jitter was used as a measure of running performance.

(Output Waveform) Commercially available Hi8VTR, ED-
The reproduction output at 7 MHz was measured using an oscilloscope by using an evaluator modified from a VTR and a DDS drive of β. Depending on the lack of this playback output envelope,
The output waveform was used as a guide.

[0071]

[Table 1]

As shown in Table 1, in comparison of Examples 1 to 3, Comparative Example 1 and Reference Example 1 using the Hi8 VTR,
Examples 1 to 3 are superior to Comparative Example 1 in both running stability and output waveform. Also, V of ED-β
Similar results were obtained in both Example 4 using TR and Comparative Example 3 and Example 5 using DDS drive and Comparative Example 2.

[0073]

As described above, the magnetic recording medium of the present invention is thin and has good running stability and good output waveform.

Claims (4)

[Claims] 1. A magnetic recording medium comprising a base film having a coating layer including at least a magnetic layer on one surface and a back coat layer on the opposite surface, wherein the following formula (1) is satisfied. . (D _M + D _B ) × 1.1 ≧ D _F (1) (where D _M is the thickness of the coating layer on the magnetic layer side, D _B is the thickness of the back coat layer, and D _F is the thickness of the base film) 2. The magnetic recording medium according to claim 1, wherein the total thickness is 6 μm or less. 3. The magnetic recording medium according to claim 1, wherein the following formula (2) is satisfied. 1 ≦ D = (D _M × D _B / D _T × W) × 10 ⁵ ≦ 10 (2) (where D _M and D _B are the same as the above formula (1), D _T is the total thickness of the medium, W is the width of the medium) 4. The magnetic recording medium according to claim 1, wherein the following formula (3) is satisfied. D _M ≦ D _B × 2 (3) (where D _M and D _B are the same as the above formula (1))