JPH06290444A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the magnetic recording medium for a master tape having an excellent high-speed characteristic in a high-speed dubbing device by specifying the coefft. of dynamic friction of a back coating layer so as to be within a specific range. CONSTITUTION:This magnetic recording medium is provided with a magnetic layer on one surface on a nonmagnetic base and the back coating layer on the other surface. The coefft. of dynamic friction of the back coating layer when the dynamic friction speed of the back coating layer of such magnetic recording medium is in a 1 to 20m/min range, is set as to be in the 0.10 to 0.25 range. The coefft. of dynamic friction of the back coating layer mentioned above is attained by increasing the projecting height of the surface of the back coating layer and increasing the number of projections. The components of the coating material for the back coating layer are composed of fine particulate carbon black having 5 to 50mum grain size, one or >=2 kinds of org. and inorg. particles having >=90mum average particle size, a binder, additives, and org. solvent and a hardener.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium,
More specifically, the present invention relates to a magnetic recording medium used as a master tape for high-speed dubbing, which has excellent high-speed running stability and high-speed running durability.

[0002]

2. Description of the Related Art At the same time that VTRs are widely used for home use,
Magnetic tape on which software such as movies is recorded, especially VHS
The tape market is expanding. Up to now, the creation (dubbing) of soft tapes such as VHS tapes is called real time, that is, multiple slave decks are arranged and the same signal sent from the master deck is recorded.
A method of simultaneously making a plurality of tapes with the same software was adopted. Dubbing in large numbers with this real-time method requires a huge number of decks (tens of thousands in many cases), and it takes a lot of time to maintain those devices in order to produce excellent quality soft tapes. I had to take the trouble. Under such circumstances, a high-speed dubbing apparatus for video called a contact printing method using the AC bias magnetic field transfer principle and the thermomagnetic transfer principle has been introduced to the market for several years. The former is sold by Sony (Sony Magnescale Co., Ltd.) under the trademark Sprinter, and the latter is TMD (Therm
al Magnetic Dupu liquor)
It is sold by Otari Co., Ltd. under the trademark. These high-speed dubbing devices for video are capable of dubbing hundreds of times faster than real-time decks.
The dubbing method is attracting attention. With the introduction of these high-speed dubbing devices for video into the market, the time and effort required for equipment maintenance have been dramatically reduced.
Both the sprinter and TMD use a master tape (metal tape) on which mirror surface recording is applied, and the magnetic surface of the master tape and the magnetic surface of the slave tape (using iron oxide, barium ferrite, chromium oxide tape) are brought into contact with each other. The method of dubbing is used. Therefore, the quality of the copy tape is easier to keep uniform as compared with the conventional real time, but the quality of the master tape is directly reflected on the copy tape. In addition, in these high-speed dubbing devices, the end and end of the master tape are connected to each other and run at a high speed of around 300 m / min. It enables highly efficient dubbing of book copy tapes. The master tape must be suitable for running in a high-speed dubbing device in order to repeatedly run such a master tape in a device at high speed and accurately transfer information on the master tape to a slave tape. A master tape with poor running suitability vibrates in the width direction in the running system of a high-speed dubbing device. In this way, the copy tape dubbed by the high-speed dubbing device suffers from deterioration in quality such as "deterioration of tracking quality" that makes the reproduced image unstable, deformation of the master tape, and "increase of copy tape dropout" due to edge damage Not only does it occur, but it also causes "reduction of the durability of the master tape", which is not preferable as a master tape for high-speed dubbing.

Generally, a master tape for high-speed dubbing is
A support formed in the form of a film or sheet such as polyethylene terephthalate, a magnetic layer formed by coating magnetic powder with a binder resin on one side of the support, and a binder such as carbon on the other side. It is composed of a back coat layer formed by coating with a resin, and in some cases, a conductive layer coated with a conductive carbon black or the like together with a binder is provided between the support and the magnetic layer for the purpose of strengthening antistatic properties. Sometimes.

Among them, as the back coat layer of the master tape, a back coat layer having a reduced dynamic friction is used for the purpose of improving running characteristics in the high-speed dubbing apparatus. Conventionally, as a method of lowering the dynamic friction coefficient of the back coat layer, it has been proposed to impart appropriate roughness to the surface of the back coat layer, and organic particles, inorganic particles, carbon black and thermal particles having an average particle diameter of about 150 μm or more are used. Black is blended (Japanese Patent Publication No. 53-20203, Japanese Patent Publication No. 54-21248, and Japanese Patent Laid-Open No. 59-2).
No. 23937, No. 60-38725, No. 60-107729, No. 61-9992.
No. 7, JP-A-61-153822, etc.). Particularly, by forming protrusions of 0.05 to 0.8 μm on the surface of the back coat layer, the running characteristics in the dubbing apparatus are significantly improved. However,

Even with such improvements, the high speed running characteristics of the master tape during dubbing have not been completely improved. Especially when the high-speed dubbing device is used in a low humidity environment of around 40% relative humidity, or when the dubbing speed is increased to increase the production capacity, the capstan, guide roller or print wheel of the high-speed dubbing device is Vibration of the master tape in the width direction occurs, and the accuracy of superposition when information is transferred to the slave tape is not maintained, resulting in "degradation of copy tape quality" and "durability of master tape". Often observed.

The vibration of the master tape in the tape width direction during the dubbing is caused by the contact of the guide roll, the capstan, the print wheel and the back coat layer for the stable running of the master tape with the air from the interface between them. This is because the discharge cannot be performed properly and a non-contact state occurs. This is similar to the hydroplaning phenomenon in which a tire with no groove has a tire with no grip when running at high speed on a wet road surface.

[0007]

The problem to be solved by the present invention is to provide a magnetic recording medium for a master tape, which is excellent in high-speed running characteristics in a high-speed dubbing apparatus.

[0008] Further, by this, without deteriorating the quality of copy tape tracking, dropout, etc.,
It is to provide a magnetic recording medium for a master tape having excellent durability.

[0009]

The inventors of the present invention have conducted extensive studies in view of the above situation, and as a result, in order to obtain a magnetic recording medium for a master tape having excellent high-speed running characteristics in a high-speed dubbing apparatus, a back coat is required. In addition to lowering the dynamic friction coefficient of the layer, if the surface of the back coat layer is formed so that the dynamic friction coefficient is in the range of 0.10 to 0.25 with respect to the dynamic friction velocity of 1 to 20 m / min. They found good things and completed the present invention.

In order to solve the above problems, the present invention provides a magnetic recording medium having a magnetic layer on one side of a non-magnetic support and a back coat layer on the other side of the non-magnetic support. The magnetic recording medium is characterized in that the coefficient of kinetic friction of the back coat layer is in the range of 0.10 to 0.25 when is in the range of 1 to 20 m / min.

As the back coat layer of the master tape used in the high speed dubbing apparatus, air can be discharged well at the interface with the capstan, the guide roll, or the print wheel in contact with the back coat layer in order to make the master tape run stably. It was necessary to maintain a stable contact state, and the following conclusions were obtained through various studies. That is, the insufficient discharge of air from the interface between the back coat surface and the guide rolls is significantly reduced from around 0.15 to 0.10 or less in the region where the dynamic friction coefficient of the back coat layer is 10 m / min or more. It was caused by this. Air can be discharged from the interface, and in order to make the contact state between the back coat layer and the capstan, the guide roll, or the print wheel constant, the dynamic friction coefficient of the back coat layer is 1 to 20 m / min. Is 0.1
It was found that it should be constant within the range of 0 to 0.25.
Further, the dynamic friction coefficient of the back coat layer of the present invention, which is suitable for a high-speed dubbing master tape, can be achieved by increasing the height of protrusions on the surface of the back coat layer and increasing the number of protrusions.

There are no particular restrictions on the components of the coating material for the back coat layer having surface protrusions, and any of the conventionally used components can be used. Fine carbon black particles having a particle size of 5 to 50 μm and an average particle size of 90 μm or more can be used. It is composed of one or more kinds of organic and inorganic particles, a binder, an additive, an organic solvent and a curing agent.

Carbon black having a particle size of 5 to 50 μm is blended for the purpose of preventing static charge of the back coat layer. Examples of commercially available carbon black that can be used for such a purpose include “Black Pearls L” and “Black Pearls 80” manufactured by Cabot Corporation.
0 ”, Degussa's“ Printex ”
"L", "Conductex SC" manufactured by Colombian Carbon Co., "Raven 125"
0 ”,“ Raven 1255 ”and the like.

The organic particles and the inorganic particles having an average particle diameter of 90 μm or more are added in order to form projections which can obtain a dynamic friction coefficient necessary for improving the running property of the master tape for a high speed dubbing apparatus according to the present invention. It Examples of the inorganic particles include carbon black, magnesium oxide, zinc oxide, magnesium carbonate, calcium carbonate, calcium sulfate, barium sulfate, alumina, silicon oxide, titanium oxide and the like. Specific examples of the inorganic particles that can be used for such a purpose include carbon black such as “Sebacarb (Sebacarb
vacarb) -MTCI "," Asahi Thermal "made by Asahi Carbon Co., Ltd.," Thermax "made by Cancarb Inc.
“MT” and the like, and examples of other inorganic particles include “Taipek” manufactured by Ishihara Sangyo Co., Ltd. and “Varifine” manufactured by Sakai Chemical Co., Ltd. Further, it is preferable that the organic particles have excellent mechanical strength, are insoluble in a solvent and are infusible at around room temperature. Specific examples include "Boncoat PP-2000" manufactured by Dainippon Ink and Chemicals, Inc., "Eposter S", "Eposter S6", and "Eposter S1" manufactured by Nippon Shokubai Co., Ltd.
2 "," Lubron L-2 "manufactured by Daikin Industries, Ltd., and the like.

As the binder, a thermoplastic resin, a thermosetting resin or a reactive resin is used. Specific examples thereof include various synthetic rubbers such as vinyl chloride vinyl acetate copolymer, polyester resin, epoxy resin, phenoxy resin, acrylic ester copolymer, polyamide resin, styrene butadiene copolymer, polyurethane resin and cellulose derivative. Resins of the system or mixtures thereof can be used. There is no problem even if the molecule of these binder resins contains a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, an alkali group such as a secondary, tertiary, or quaternary ammonium group. Even if the former acid group contains a metal ion such as sodium to form a salt, it further contains an organic ion such as a secondary, tertiary or quaternary ammonium in the resin to form a salt. However, there is no problem.

As the organic solvent, tetrahydrofuran,
Methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, butyl acetate, toluene and the like can be used.

Regarding additives, curing agents, and other compounds, depending on the necessity, for example, additives may be lubricants, dispersants, stabilizers, etc. Diisocyanate may be added.

In order to prepare the coating material for the back coat layer, the above-mentioned composition excluding the curing agent is dispersed and mixed in an appropriate formulation all at once, and the curing agent is added immediately before coating.

There are no particular restrictions on the components of the magnetic paint, and any of those conventionally used can be used, and it is composed of magnetic particles, a binder, an additive, an organic solvent and a curing agent.

Magnetic particles include iron oxide (γ-Fe
₂ O ₃ ), cobalt-adhered iron oxide (Co-Fe ₂ O ₃ ), chromium oxide (Cr ₂ O), etc. are not suitable as materials for master tape due to their low coercive force, and are Alloys, that is, Fe, Co, Ni simple substance and Fe-
Metal components such as Co, Fe-Ni and Fe-Ni-Co are preferably used. These magnetic powders have Al and S on the surface.
Some elements include a plurality of elements such as i, Cr, Zn, Cu and Zr. As the ferromagnetic metal or alloy, fine particles which are sufficiently surface-oxidized in order to stably exist in air are used.

As the binder, a thermoplastic resin, a thermosetting resin or a reactive resin is used. Specific examples thereof include various synthetic rubbers such as vinyl chloride vinyl acetate copolymer, polyester resin, epoxy resin, phenoxy resin, acrylic ester copolymer, polyamide resin, styrene butadiene copolymer, polyurethane resin and cellulose derivative. Resins of the system or mixtures thereof can be used. There is no problem even if the molecule of these binder resins contains a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, an alkali group such as a secondary, tertiary, or quaternary ammonium group. Even if the former acid group forms a salt containing a metal ion such as sodium, it also forms a salt containing a partial ion with the secondary, tertiary and quaternary ammonium in the resin. However, there is no problem.

As additives, various fatty acids, fatty acid esters, carbon black, magnesium oxide, zinc oxide, magnesium carbonate, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, and other lubricants, and alumina, silicon carbide, and chromium oxide. Abrasives such as (Cr ₂ O ₃ ) and diamond can be used.

As the organic solvent, tetrahydrofuran,
Methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, butyl acetate, toluene and the like can be used.

Regarding additives, curing agents, and other compounds, depending on the need, for example, additives may be lubricants, dispersants, stabilizers, etc. You may add diisocyanate etc.

To prepare the coating material for the magnetic layer, the above-mentioned composition excluding the curing agent is dispersed and mixed together in an appropriate formulation, and the curing agent is added immediately before coating.

There are no particular restrictions on the components of the paint for the conductive layer, and any of the conventionally used ones can be used.
It is composed of particulate carbon black having a particle size of 5 to 50 μm, a binder, an additive, an organic solvent and a curing agent.

Carbon black having a particle size of 5 to 50 μm is added for the purpose of reducing the electric resistance to 10 ⁶ Ω / sq or less and enhancing antistatic property. Commercially available carbon blacks that can be used for such purposes include "Black Pearls L" and "Black Pearls 80" manufactured by Cabot Corporation.
0 "," Printex L "manufactured by Degussa," Conductex SC "manufactured by Colombian Carbon," Raven 1250 "," Raven 1255 "and the like.

As the binder, a thermoplastic resin, a thermosetting resin or a reactive resin is used. Specific examples thereof include various synthetic rubbers such as vinyl chloride vinyl acetate copolymer, polyester resin, epoxy resin, phenoxy resin, acrylic ester copolymer, polyamide resin, styrene butadiene copolymer, polyurethane resin and cellulose derivative. Resins of the system or mixtures thereof can be used. There is no problem even if the molecule of these binder resins contains a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, an alkali group such as a secondary, tertiary, or quaternary ammonium group. Even if the former acid group forms a salt containing a metal ion such as sodium, it further forms a salt containing an organic ion such as secondary, tertiary or quaternary ammonium in the resin. There is no problem.

As the organic solvent, for example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, butyl acetate, toluene and the like can be used.

Regarding additives, curing agents, and other compounds, depending on the need, for example, additives may be lubricants, dispersants, stabilizers, etc. Diisocyanate may be added.

In order to prepare the coating material for the conductive layer, the above-mentioned composition excluding the curing agent is dispersed and mixed together in an appropriate formulation, and the curing agent is added immediately before coating.

[0032]

Embodiments of the present invention will be described below.

(Example 1) (Formation of conductive layer) A conductive coating composition containing conductive carbon black was mixed and dispersed in a ball mill, and then "Coronate L" (polyisocyanate compound manufactured by Nippon Polyurethane Company). 30 parts was added and mixed well to prepare a conductive paint. This conductive paint was applied to one side of a polyester film having a thickness of 23.4 μm and the thickness after drying was 0.5 μm.
And was dried. This is 50 ℃
Then, the crosslinking reaction of the curing agent was promoted for 24 hours to obtain a conductive layer.

“Conductex SC” (carbon black with a particle size of 5 to 50 μm manufactured by Colombian Carbon Co., Ltd.) 100 parts “MR-110” (vinyl chloride-acrylic acid ester copolymer manufactured by Zeon Corporation) ) 50 parts "T-5206" (Polyurethane resin manufactured by Dainippon Ink and Chemicals, Inc.) 20 parts Stearic acid butyl ester 1 part Methyl ethyl ketone 500 parts Toluene 500 parts Cyclohexanone 500 parts

(Formation of magnetic layer) The following magnetic layer composition was mixed and dispersed by a ball mill, and then 6 parts of "Coronate L" (polyisocyanate compound manufactured by Nippon Polyurethane Co.) was added and thoroughly mixed to form a magnetic layer. A coating material was prepared. This magnetic layer coating material is applied onto the above-mentioned conductive coating so that the thickness after drying is 3
It was applied to have a thickness of μm, and the magnetic particles were oriented through a magnetic field. After this was dried, a surface smoothing treatment was performed to accelerate the crosslinking reaction of the curing agent at 60 ° C. for 48 hours. This was used as a magnetic layer.

“Α-Fe magnetic powder” (specific surface area 50 m ² / g, saturation magnetization 120 emu / g, coercive force 120 oersted / m, axial ratio 10) 100 parts “MR-110” 12 parts “T-5206” 8 parts Alumina powder 5 parts "Vulcan XC-72" (carbon black manufactured by Cabot) 2 parts Myristic acid 3 parts Methyl ethyl ketone 105 parts Toluene 105 parts Cyclohexanone 105 parts

(Formation of Backcoat Layer) After mixing and dispersing the following ingredients in a ball mill, 80 parts of "Coronate L" (polyisocyanate compound manufactured by Nippon Polyurethane Co., Ltd.) was added and mixed sufficiently to prepare a coating material for the backcoat layer. Was prepared. This back coat layer coating material was applied onto the substrate on the opposite surface on which the magnetic layer was not formed so that the thickness after drying was 1 μm, and this was dried and then at 24 ° C. at 24 ° C.
The crosslinking reaction of the time curing agent was promoted. This was used as the back coat layer.

“Conductex SC” 100 parts “Sevacarb MTCI” (Thermal black manufactured by Colombian Carbon Co., Ltd.) 100 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 parts Toluene 760 parts Cyclohexanone 760 parts

The above coated material was slit into a width of 1/2 inch to obtain a master tape for high speed dubbing.

Example 2 A master tape for high-speed dubbing was obtained in the same manner as in Example 1 except that the composition of the back coat layer coating composition was changed as follows.

“Conductex SC” 50 parts “Sevacarb MTCI” 150 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 parts Toluene 760 parts Cyclohexanone 760 Department

Example 3 A high speed dubbing master tape was obtained in the same manner as in Example 1 except that the composition of the back coat layer coating composition was changed as follows.

“Conductex SC” 100 parts “Eposter S12” (Nippon Shokubai's organic particles) 100 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 Parts Toluene 760 parts Cyclohexanone 760 parts

Comparative Example 1 A high speed dubbing master tape was obtained in the same manner as in Example 1 except that the composition of the back coat layer coating composition was changed as follows.

“Conductex SC” 200 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 parts Toluene 760 parts Cyclohexanone 760 parts

Comparative Example 2 A high speed dubbing master tape was obtained in the same manner as in Example 1 except that the composition of the back coat layer coating composition was changed as follows.

“Conductex SC” 190 parts “Sevacarb MTCI” 10 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 parts Toluene 760 parts Cyclohexanone 760 Department

(Comparative Example 3) A master tape for high speed dubbing was obtained in the same manner as in Example 1 except that the composition of the back coat layer coating composition was changed as follows.

“Conductex SC” 160 parts “Sevacarb MTCI” 40 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 parts Toluene 760 parts Cyclohexanone 760 Department

(Comparative Example 4) A master tape for high speed dubbing was obtained in the same manner as in Example 1 except that the composition of the back coat layer coating composition was changed as follows.

“Conductex SC” 190 parts “Eposter S12” 10 parts “MR-110” 160 parts “T-5206” 40 parts Stearic acid butyl ester 4 parts Methyl ethyl ketone 760 parts Toluene 760 parts Cyclohexanone 760 parts

The high-speed dubbing master tapes obtained in the above Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 1. Hereinafter, the evaluation method in the present invention will be described.

1. Dynamic friction coefficient A cylinder having a diameter of 60 mm is supported horizontally, and the backcoat layer side of the magnetic tape is applied to this as a contact surface to form an angle of 180 degrees, and a load of 60 g is applied to one end of the magnetic tape.
A tension gauge was installed at the other end. The stress T value received by the tension gauge when the cylinder was rotated at a peripheral speed of 4 m / min in the direction in which the load was applied was calculated, and the dynamic friction coefficient μk (4 m / min) was calculated from the following formula.

[0054]

[Formula 1] μk = 1 / π · ln (T / 60)

The coefficient of kinetic friction μk (15 m / min) was calculated by rotating the peripheral speed of the cylinder at 15 m / min in the above procedure.

2. Dropout (before transfer) After recording a video signal using a mirror master recorder (hereinafter abbreviated as MMT) manufactured by Otari Co., Ltd.,
The dropout generated when regenerated was measured by a Shibasoku dropout counter (measurement conditions: 15 μs, 16
The average value (measured for 10 minutes) per minute measured in dB) is shown.

3. Dropout (after transfer) TMD system (trade name "T-70" manufactured by Otari Co., Ltd.
0MK2 ") and the 10th and 5000th copy tapes obtained by dubbing under the following conditions were subjected to VHS.
Method VTR (Matsushita Electric Co., Ltd., trade name "NV-880"
0 ") was used to measure the dropouts obtained when regenerated with a Shibasoku dropout counter (measurement condition: 15μ).
s, 16 dB) average value per minute (1
(Measured for 0 minutes).

Tape speed during dubbing: 5 m / min Slave tape: VHS tape for TMD (BA
(Made by SF)

4. State of running master tape in high-speed dubbing apparatus When the master tape was transferred 10 times and 5000 times, the state of vibration of the master tape on the capstan and the guide roll in the tape width direction was evaluated.

5. Damage state of master tape after 5000 times transfer The abrasion state of the back coat surface and the damage state of the tape edge of the master tape after 5000 times transfer were evaluated by a high speed dubbing apparatus.

[0061]

[Table 1]

*: In Comparative Example 1, dubbing could not be performed because the vibration in the tape width direction was severe.

The following can be seen from Table 1. When the dynamic friction coefficient of the back coat layer is 0.25 or more regardless of the dynamic friction speed as in Comparative Example 1, violent vibration in the tape width direction occurs in the running system of the master tape high-speed dubbing device, and the copy I could not transfer information to the tape normally,
Not suitable as a master tape for high-speed dubbing equipment.

When the coefficient of kinetic friction at 4 m / min is significantly lower than 0.10 as in Comparative Examples 2, 3 and 4, a copy tape of good quality can be obtained in the initial transfer.
However, since there is vibration in the tape width direction in the running system of the high-speed dubbing device, the master tape is gradually damaged, and the quality of the copy tape is deteriorated at the 5000th transfer.

As in Examples 1, 2 and 3, 4 m / min, 15
When the coefficient of dynamic friction both in m / min is in the range of 0.10 to 0.25, there is no vibration in the tape width direction in the running system of the high-speed dubbing device, and the master tape is less damaged even after 5000 times of transfer. As a result, the quality of the 5000th copy tape is less changed than that of the initial transfer tape.

It will be understood that by having the back coat layer of the present invention, an excellent master tape for a high speed dubbing device can be obtained.

[0067]

The introduction of the back coat layer according to the present invention makes it possible to obtain a master tape for high speed dubbing which is excellent in running characteristics and durability in a high speed dubbing apparatus. In addition, it is possible to obtain an excellent copy tape with stable quality.

Claims (1)

[Claims] 1. A magnetic layer is provided on one side of a non-magnetic support,
In a magnetic recording medium having a back coat layer on the other surface, the dynamic friction coefficient of the back coat layer is 0.10 to 10 m / min when the dynamic friction velocity is in the range of 1 to 20 m / min.
A magnetic recording medium characterized by being in the range of 0.25.