JPS59186128A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the transfer of the shape of the back layer of a magnetic tape to the magnetic surface and the reduction of the S/N ratio by forming the back layer using a mixture of carbon black having a specified average particle size or below with CaCO3 or SiO2, a binder and a small amount of an org. lubricant. CONSTITUTION:A back layer of 0.05-2mum thickness is formed on one side of a support having a magnetic layer on the other side for a magnetic tape by coating so as to adjust the maximum surface roughness to <=300mmu. The back layer contains 100-300pts.wt. mixed filler consisting of carbon black having <=80mmu single particle size and CaCO3 and/or SiO2 having <=80mmu single particle size and 0.1-5pts.wt. org. lubricant such as fatty acid ester, fatty acid amide or fatty acid in 100pts.wt. binder such as nitrocellulose, polyester elastomer, polyurethane elastomer or a mixture thereof. A magnetic tape or the like having superior wear resistance, durability and a high S/N ratio is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media, and in particular, by smoothing the surface of the back layer, it is possible to prevent shape transfer from the back layer to the magnetic surface side and reduce the S/N. The object of the present invention is to provide a magnetic recording medium that can reduce the friction coefficient of the back layer and improve running durability without causing any damage.

Conventional Structures and Problems In magnetic recording tapes for video tape recorders or computers, the surface of the magnetic recording layer is finished smooth. As a result, running performance deteriorates, and irregular winding and output fluctuations occur.

In order to prevent this drawback, research has been conducted to provide a bank layer on the surface of the support opposite to the magnetic recording layer.

This situation also applies to metal thin film tapes with high recording density. However, conventionally used vinyl chloride-vinyl acetate copolymers have poor abrasion resistance, which adversely affects running durability. In fact, if you value the runnability of the back layer and keep its surface rough and wind it up into a roll or stack it in sheets, the shape of the back layer will be reflected on the magnetic layer side and the S/N characteristics will deteriorate. There is a problem with doing so.

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide a bank layer that does not deteriorate the S/N characteristics of a magnetic recording medium, and to provide a bank layer that has running durability without increasing the friction coefficient of the back layer with the number of runs. The goal is to provide a magnetic recording medium with a back layer.

Structure of the Invention The magnetic recording medium of the present invention is a magnetic recording medium formed by forming a metal thin film on one main surface of a non-magnetic base material, wherein the average single particle diameter is 80 m/l or less on the other main surface of the support. A mixture of carbon blank and calcium carbonate, −! a backing layer containing a binder in a mixture of fillers, either a carbon blank of 2 cm thick or a mixture of carbon black and silicon dioxide, and a mixture of calcium carbonate and silicon dioxide; 10 parts of filler
0 to 300 parts by weight are blended, and the bank layer has a thickness of 0.
05μ to 2μ, and the surface roughness of the backing layer is 300m11 or less at maximum roughness (Rmax), and contains 0.1 to 5 parts by weight of an organic lubricant per 100 parts by weight of the binder. It is characterized by

Suitable binders for use in the present invention include, for example, nitrocellulose + e')ester elastomer and polyurethane elastomer, and each can be used alone or in a mixture of two or three types.

The average single particle diameter of the back layer filler used to adjust surface roughness and electrical resistance is 80 m.74
The following SiO2+ CaCo3 is a carbon blank, and an appropriate amount of carbon blank is absolutely necessary for adjusting electrical resistance. The amount is 100 binders
The amount is 5 to 40 parts by weight. The other 8102 or CaCo3 may be added alone or as a mixture, but the role of these two fillers is to finely roughen the surface and at the same time make the coating film as a bank layer hard and resistant. Helps improve wear resistance. The amount of all these photonic agents used is 1 to 3 in weight ratio to the binder. If it is less than this, or if it is more than 5 dimensions, the properties of the coating film will deteriorate, the abrasion resistance will be poor, and clogging and output reduction will be significant. Furthermore, with this configuration, the surface roughness of the back surface is improved, and the maximum surface roughness of the back surface can be reduced to 300 mμ or less. The maximum surface roughness of the bank layer is 300m.
When it is less than μ, there is almost no shape transfer to the magnetic layer side of the metal thin film magnetic tape when it is wound into a roll, and S
/N characteristic deterioration can be prevented. If the maximum surface roughness of the bank layer is 300 mμ or more, shape transfer occurs in the metal thin film type magnetic tape, resulting in deterioration of the S characteristic, which is a major feature of this tape.

On the other hand, when the surface properties of the back layer are made finer as described above, the coefficient of friction of the back layer inevitably tends to increase. Therefore, fatty acid ester is added to lower the friction coefficient of the back layer. The amount added is 0.1 to 6 parts by weight per 100 parts by weight of the binder. Addition amount is 0.1
When the amount is less than 5 parts by weight, the friction coefficient of the back layer is not significantly lowered, and when it is more than 5 parts by weight, clogging due to the added fatty acid ester increases.

In this way, the surface roughness is reduced, shape transfer from the bank layer to the magnetic surface is eliminated, and the resulting increase in frictional resistance of the bank layer is solved by changing the amount of fatty acid ester added. Furthermore, it was found that the thickness of the backing layer is also related to running durability and running characteristics. It is desirable that the bank layer be as thin as possible as long as running durability and running characteristics are ensured, and under the conditions of the present invention, the thickness was 0.05 μm to 2 μm, more preferably 0.2 μm to 0.5 μm. When the thickness was less than 0.05μ, uniformity of the bank layer could not be obtained.

DESCRIPTION OF EMBODIMENTS Next, embodiments of the present invention will be described. In addition, "parts" in the following examples shall indicate "parts by weight."

(Example 1) Nitrocellulose 40 parts Polyester elastomer 60 parts Carbon black 30 parts Stearyl stearate 2 parts Charcoal powder
150 parts methyl ethyl ketone
1000 parts toluene
1000 parts cyclohexanone
Bank layer consisting of 1000 parts (Example 2) Nitrocellulose 40 parts Polyurethane elastomer 60 parts Carbon black 30 parts Stearyl myristate 2 parts Charcoal powder
1.00 parts silica dioxide powder
60 parts methyl ethyl ketone
1000 parts toluene
1000 parts cyclohexanone 10
Bank layer consisting of 00 copies.

(Example 3) Nitrocellulose 20 parts Polyurethane elastomer 50 parts Polyester elastomer 30 parts Stearyl stearate 100 parts Carvone plaque
20 parts silica dioxide powder
100 parts methyl ethyl ketone
100 parts toluene 10
00 parts cyclohexanone 1000
Back layer consisting of parts (Example 4) Nitrocellulose 40 parts Polyurethane entomer 60 parts Carbon blank 30 parts Sugaryl stearate 2 parts Charcoal powder
50 parts methyl ethyl ketone
1000 parts toluene
1000 parts cyclohexanone
In both Examples 1.2 and 3.4, the bank layer consisting of 1000 parts had a single particle diameter of 80 m.
Using carbon black, calcium carbonate, and silicon dioxide with a particle diameter of less than μ, each composition is sufficiently cross-dispersed in an attritor to form a paint, which is applied to the back side of a metal thin film type magnetic tape. After drying, the maximum roughness of the bank layer is The bank layer has a length of 300 mμ or less and a thickness of 200 mμ to 600 mμ.

The samples corresponding to Examples 1 to 4 are referred to as sample A, sample B, and sample C9, respectively. For the four types of samples mentioned above, the decrease in output and the state of wear of the bank layer after running 50 times (50 passes) were investigated. Furthermore, the coefficient of friction between the bank layer and the stainless steel pole was examined under conditions of 30° C. and 90° humidity.

The results are shown in the table below.

10 Knee Z As is clear from the above table, the back layer in the magnetic recording medium of the present invention, unlike the conventional back layer, has a very thin thickness of 200 m11 to 500 mμ, and a fine surface roughness of 300 mμ or less. Even if the number of runs increases, the output does not decrease, and the change in the coefficient of friction is extremely small.3 As the test EC shows, the fatty acid ester is more than 5 parts by weight based on the binder. Then, the output decreases significantly. As shown in the sample, if the filler is not in the range of 1 to 3 parts by weight based on the binder, the running resistance of the back layer will not be sufficient and the coefficient of friction will increase significantly.

In addition, the following Examples 5 to 8. In Examples 9 to 12, the same good characteristic results as in Examples 1 to 4 were obtained.

(Example 5) Nitrocellulose 40 parts Polyester elastomer 60 parts Carbon black 30 parts Stearic acid
2 parts charcoal powder
160 parts methyl ethyl keto 7
1000 parts toluene
1000 parts cyclohexanone 10
Bank layer consisting of 00 parts (Example 6) Nitrocellulose 40 parts Polyurethane distomer 60 parts Carbon black 30 parts Myristic acid
2 parts charcoal powder
100 parts silica dioxide powder
60 parts methyl ethyl ketone
1000 parts toluene
1000 parts cyclohexanone 10
Bank layer consisting of 00 parts (Example 7) Nitrocellulose 2o parts Polyurethane elastomer 60 parts Polyester elastomer 30 parts 3 Stearic acid 10 parts Carbon black 2o parts Silica dioxide powder 100 parts Methyl ethyl ketone 1000 parts Toluene
1000 parts cyclohexanone
Back layer consisting of 1000 parts (Example 8) Nitrocellulose 40 parts Polyurethane distomer 60 parts Carbon blank 30 parts Myristic acid
2 parts charcoal powder
50 parts methyl ethyl ketone
10○ parts toluene
1000 parts cyclohexanone 1
Back layer consisting of 000 parts (Example 9) Nitrocellulose 4o parts Polyester elastomer 60 parts 14.
--- Carbon blank 30 parts Stearic acid amide 2 parts Charcoal powder 150 parts Methyl ethyl ketone 1000 parts Toluene
1ooO part cyclohexane
Bank layer consisting of 1000 parts (Example 10) Nitrocellulose 40 parts Polyurethane elastomer 6o parts Carbon black 3o parts Behenic acid amide
2 parts charcoal grain powder
100 parts silica dioxide powder
60 parts methyl ethyl ketone
1000 parts toluene 100
Back layer consisting of 0 parts cyclohexanone 1000 parts (Example 11) Nitrocellulose 20 parts Polyurethane distomer 50 parts Polyester elastomer 30 parts Stearic acid amide 10 parts Carbon blank
20 parts cane dioxide granules
100 parts methyl ethyl ketone 1
Bank layer consisting of 000 parts toluene 1000 parts cyclohexanone 1000 parts (Example 12) Nitrocellulose 4o parts Polyurethane elastomer 60 parts Carbon black 3o parts Behenic acid amide
2 parts charcoal powder
50 parts methyl ethyl ketone
1000 parts toluene
1000 parts cyclohexanone 10
As explained in detail about the back layer invention, the magnetic recording medium of the present invention does not deteriorate the S/N characteristics despite the presence of the back layer, has high running durability, and is industrially suitable. has high utility value.

Name of agent: Patent attorney Toshio Nakao and 1 other person16
3

Claims (4)

[Claims] (1) In a magnetic recording medium formed by forming a metal thin film on one main surface of a non-magnetic base material, a mixture of a carbon blank having an average single particle diameter of 80 mμ or less and calcium carbonate on the other main surface of the support. , or a mixture of carbon black and silicon dioxide, with a backing layer containing a binder in a mixture of fillers, either a carbon blank and a mixture of calcium carbonate and silicon dioxide, said binder 100 100 to 300 parts by weight of a filler is blended with respect to parts by weight, the thickness of the bank layer is 0.05 μ to 2 μ, the surface roughness of the bank layer is 300 m μ or less at maximum roughness, and the binder 0.1 to 5 per 100 parts by weight
A magnetic recording medium comprising parts by weight of an organic lubricant. (2) The magnetic recording medium according to claim 1, wherein the organic lubricant is a fatty acid ester. 2, -- (3) The magnetic recording medium according to claim 1, wherein the organic lubricant is a fatty acid. (4) The magnetic recording medium according to claim 1, wherein the organic lubricant is a fatty acid amide.