JPS623422A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium having the excellent traveling property, antistatic property and smoothness of the medium surface by allowing a lubricating agent to be present in a black-painted layer or on the surface of the layer having prescribed surface resistivity and surface roughness. CONSTITUTION:A magnetic layer is formed on the surface of a substrate and the black-painted layer is formed on the rear surface to form a magnetic recording medium. The surface resistivity of the black-painted layer having an hydroxyl group and consisting essentially of silicon oxide is regulated to <=10<12>OMEGA, the surface roughness of the layer is controlled to <=0.2mum Rmas value prescribed by JIS-B0601 and the film thickness is adjusted to <=0.5mum. A lubricating agent expressed by CF3(CF2)nCH2SiR<1>R<2>R<3> is allowed to exist in the black-painted layer or on the surface of the layer. In the formula, (n) is >=0 integer, R<1> shows one kind among (CH2)lCH3, Cl, Br and O(CH2)mCH3 and (l) and (m) express >=0 integer. R<2> and R<3> stand for one kind among Cl, Br and O(CH2)mCH3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium that has excellent running properties, antistatic properties, and smoothness on the back surface of the medium.

[Technical background of the invention and its problems] In recent years, as various electronic and electrical devices have become lighter, thinner, and smaller, magnetic recording devices and magnetic recording media have also become smaller and more sophisticated. There is a need for magnetic recording media capable of density recording.

In promoting high-density recording of magnetic recording media,
In addition to improving the magnetic properties, it is also necessary to improve the running properties, antistatic properties, and smoothness of the back surface of the media.

For example, in high-density recording tapes such as 8■ video tapes, if the running properties are even slightly inferior, the reproduced image will be significantly blurred, which is a problem that occurs because it is a high-density recording tape. have. That is, in a normal tape, even if the running performance is slightly deteriorated, it does not affect the reproduced image so much, but in the case of a high-density recording tape, the degree of influence becomes large.

In addition, if anti-static properties are insufficient, dust will easily adhere to the medium, and therefore, when the medium approaches the magnetic head, these will become trapped between the medium and the magnetic head, resulting in In particular, as the recording density increases, the distance between the medium and the magnetic head becomes narrower, so even a small amount of dust can easily damage the medium. In addition, with high-density recording media, even a small scratch on the media can cause a draw.
This can easily lead to a dropout.

If the prevention of scratches is still insufficient, the running performance will deteriorate, resulting in uneven tape winding and tape bending.Also, if the back surface of the media is not smooth enough, use a tape running guide. If it is damaged or loose, the cassette's idle roller will be scraped off by the back side of the media, resulting in shavings that will cause dropouts, and the guide roller will be scraped, causing problems such as irregular tape running. Furthermore, since the back surface of the medium and the surface of the magnetic layer are in contact with each other in the cassette, if the smoothness of the back surface of the medium is significantly poor, the unevenness on the back surface of the medium will be transferred to the surface of the magnetic layer. This has the problem of increasing noise.

[Purpose of occurrence] The present invention solves the above problems and improves running performance.

The purpose is to provide magnetic recording media with excellent antistatic properties and smoothness on the back surface of the media.

[Summary of the Invention] As a result of intensive research to achieve the above object, the present inventors provided a backing layer on the back surface of the medium, and set the surface resistivity 1 surface roughness of the backing layer to within the range described below. The present inventors have discovered the fact that if the lubricant is present in the backing layer, the running properties, antistatic properties, and smoothness of the back surface of the medium can be improved, and the present invention has been completed.

That is, the magnetic recording medium of the present invention has a substrate.

A magnetic recording medium comprising a magnetic layer formed on the surface of the substrate and a backing layer formed on the back surface of the substrate, wherein the backing layer has a surface resistivity of 10 12 Ω or less, and the backing layer The surface roughness of R specified by JIS 80801
It is characterized in that it has a maf value of 0.2- or less, and a lubricant is present in the backing layer or on the surface of the W coating layer.

First, in the present invention, examples of the substrate on which the magnetic layer and the backing layer are formed include various films and disks made of polyester, polyethylene terephthalate, polyimide, polyamide, aromatic polyester, polyamideimide, polyphenylene sulfide, etc. It will be done.

Next, the magnetic layer formed on the surface of the substrate described in -1- is
This can be achieved by applying a magnetic paint consisting of the following components onto the surface of the substrate. In other words, a magnetic paint is usually composed of magnetic powder, a resin, and various additives (for example, a dispersant, a coating agent, a lubricant, etc.).

Examples of magnetic powder include Go-coated ferrite,
Examples include hexagonal magnetic powder (for example, orthogonal barium ferrite powder), iron, nickel, cobalt, etc. powder or alloy powder.

Examples of the binder resin include urethane resin and vinyl chloride-vinyl acetate copolymer.

Examples include acrylic ester resins, polyvinyl butyral resins, and polyester resins.

Next, the backing layer formed on the back surface of the substrate, that is, the surface opposite to the magnetic layer, will be described. The main feature of the present invention is this backing layer.

That is, (1)! The surface resistivity of the B coating layer is 102Ω or less.

(2) The surface roughness of the backing layer is R, a! defined by JIS B0601. It is characterized in that the backing layer satisfies the following three requirements: (3) a lubricant is present in the backing layer or on the surface of the backing layer; .

First, the surface resistivity is 10L2Ω or less, preferably 1OI
If the 0 surface resistivity, which is less than 0Ω, exceeds IQ'Ω, a sufficient antistatic effect cannot be obtained, leading to adhesion of dust and the like to the medium.

In order to reduce the surface resistivity to 10L2Ω or less, it is sufficient to make this backing layer a conductive layer. To form such a conductive layer, (a) a conductive substance such as conductive carbon, (b) Method 1 of forming a thin film of metal such as aluminum, chromium, nickel, etc. on the back surface of the substrate by, for example, deposition. (C) A method of forming an inorganic layer containing hydroxyl groups on the back surface of the substrate.

These backing layers may have either a dense or porous structure, and if the backing layer is porous, the lubricant described below can be retained in the pores. This is useful, and when a flexible substrate is used as the substrate, there are advantages such as being able to easily follow the deformation of the substrate.

In the method (C) above, examples of the inorganic substance having a hydroxyl group include orthomethylsilicate.

5i02 having silanol groups on the surface or inside obtained by hydrolysis and condensation of alkyl silicate such as orthoethylsilicate and orthopropylsilicate
; Ti having hydroxyl groups on the surface or inside obtained by similar hydrolysis and condensation reactions of metal alkoxide compounds;
Examples include O2, ZrO2, GeO2°A4203.5n02.

The thickness of the inorganic material having a hydroxyl group is preferably set to 0.5 or less, preferably 0.3 or less. If the thickness of the inorganic material layer exceeds Q, 5 g, cracks may appear in the inorganic layer, This is undesirable because the layer tends to peel off from the substrate.

Next, the second requirement is that the surface roughness is 0.2μ or less, preferably 0.1-.The surface roughness in the present invention is as follows:
Maximum height R as specified by JAS B 0801
ffi&ri. If the surface roughness is greater than 0.2p, there is a risk that the unevenness of the backing layer will be transferred to the magnetic layer, causing an increase in noise or scraping the tape running guide.

To adjust the surface roughness 1. For example, use (a) above.

When applying a method such as (C), the particle size of the powder used,
The viscosity of the paint can be expressed as yJ.

Next, the third requirement is that the lubricant be present in or on the surface of the backing layer. i! In order to have l-lubricant present in the backing layer, that is, in the conductive layers such as (a), (b), and (c) described above, a l-lubricant dispersed in the above-mentioned conductive paint is added to the back surface of the substrate. It may be coated with IH3. In this case, it is preferable that the backing layer has a porous structure as described above.

In addition, in order to make the lubricant exist on the surface of the y1 coating layer,
A lubricant may be further applied on the formed backing layer.

The lubricant is not particularly limited as long as it has a lubricating effect, and may be the same as the lubricant contained in the magnetic layer.

Such lubricants include fatty acids, fatty acid esters,
silicone), fluorine m, paraffin.

Examples include fluorosilicone compounds, fatty acid amides, aliphatic ethers, and aliphatic alcohols.

In particular, when the backing layer is composed of a layer of an inorganic substance having a hydroxyl group represented by -F (c), as a lubricant, the general formula: C
F3(C:F2)rlCH2SiR'R2R3 (in the formula.

n represents an integer greater than or equal to 0, R1 is (C:R2)IC)
13. C.I.

Represents either Br, 0(CH2), (:H (
However, love.

m represents an integer greater than or equal to 0); Each of R2 and R3 represents either CQ, Br, or 0(C:R2)IllCH3 (however, the heel has the same meaning as in the above figure). It is effective to use fluorosilicone compounds. This is thought to be because the lubricant is fixed in the inorganic layer as a result of chemical bonding between the fluorosilicone compound and the hydroxyl group in the inorganic layer, and the effect of the lubricant is maintained for a long time.

[Examples of the Invention] Example 1 A magnetic paint having the composition shown in Table 1 was applied to one side of a polyester film having a thickness of IO- to form a magnetic layer.

Table 1 Next, on the opposite side of the magnetic layer, a 2% concentration improvator solution of an ethyl silicate condensate was applied to form a conductive backing layer.

Then, apply a hexane-methyl ethyl ketone (1:1) solution of stearic acid at a concentration of 0.5z to the surface of the backing layer!
1 and a lubricant was present on the surface of the backing layer.

The obtained film was cut to a width of 3.8 mm and wound into an audio C cassette, and the cassette was set on a tape deck and various tests were conducted.

In other words, in order to evaluate the running performance, before the running performance test and after 50
The coefficient of friction after the pass was measured. Further, tape noise and surface resistivity 1 surface roughness were measured and the results are shown in Table 3. In addition, in order to examine the transferability of unevenness on the back side of the medium,
Table 3 shows the measurement results of tape noise of 0 or more.

Comparative Example 1 The same magnetic layer as in Example 1 was formed on the same substrate as in Example 1. Then, on the opposite side of the magnetic layer, a conductive paint having the composition shown in Table 2 was applied and dried and cured.

Table 2 The obtained film was cut in the same manner as in Example 1.

A cassette tape was similarly produced and tested in the same manner.

Example 2 A magnetic layer was formed in the same manner as in Example 1, except that barium ferrite powder (average particle size: 0.07 g, He 7500e) was used as the magnetic powder. and.

A backing layer similar to that in Example 1 was formed on the opposite side of the magnetic layer. CF3 (CF2) with a concentration of 0.2% is applied to the surface of this backing layer.
)s(C)12)2Si(OCH3)3 in hexane-methyl ethyl ketone (l:1) solution was applied.

Using the obtained film, a cassette tape was produced in the same manner as in Example 1, and the same measurements were performed.

Comparative example 2 A magnetic layer was formed on the substrate in the same manner as in Example 2.

Then, on the opposite side of this magnetic layer, a paint having the same composition as shown in Table 2 was applied, except that the binder resin was 50 parts by weight of urethane resin and 50 parts by weight of vinyl chloride-vinyl acetate hybrid resin. formed a layer.

Using the obtained film, a cassette tape was produced in the same manner as in Example 1, and measurements were performed in the same manner.

Comparative Example 3 A cassette tape was produced in the same manner as in Example 1 using a film in which only a magnetic layer was formed on the substrate, but no conductive backing layer was formed on the opposite side. However, measurements were carried out in the same manner.

Comparative example 4 Except that no lubricant was present in the backing layer.

A cassette tape was produced in the same manner as Comparative Example 1, and measurements were performed in the same manner.

Example 3 An audio tape having a conductive backing layer was produced in the same manner as in Example 1, except that the ethyl silicate condensate was replaced with a butyl titanate condensate. The results of similar measurements of the properties of this tape are shown in Table 3 and were good.

[Effect of the invention] As is clear from the embodiments of the invention, the &i
Air recording media have good running properties, excellent antistatic properties, and excellent smoothness on the back surface of the media, so they do not damage the media or tape guide, etc., and have low tape noise, especially for high-density recording media. It is useful as a magnetic recording medium for recording.

Claims (1)

[Claims] 1. In a magnetic recording medium comprising a substrate, a magnetic layer formed on the surface of the substrate, and a backing layer formed on the back surface of the substrate, the surface resistivity of the backing layer is is less than 10^1^2Ω,
And the surface roughness of the backing layer is 0.2 μm or less in R_m_a_x value specified in JIS B0601, and a lubricant is present in or on the surface of the backing layer. magnetic recording medium. 2. The magnetic recording medium according to claim 1, wherein the backing layer is made of an inorganic material having a hydroxyl group. 3. The magnetic recording medium according to claim 2, wherein the inorganic substance having a hydroxyl group mainly consists of silicon oxide. 4. The magnetic recording medium according to claim 2, wherein the backing layer has a thickness of 0.5 μm or less. 5. The magnetic recording medium according to claim 2, wherein the lubricant is a lubricant that chemically bonds with the inorganic substance having glacial acid groups. 6. The lubricant has the general formula: CF_3(CF_2)_nC
H_2SiR^1R^2R^3 (in the formula, n is 0
Represents an integer greater than or equal to: R^1 is (CH_2)_lCH_
3, Cl, Br, O(CH_2)_mCH_3 (however, l and m represent integers of 0 or more)
;R^2 and R^3 are Cl, Br, O(CH_
2) _mCH_3 (however, m has the same meaning as m above). ) The magnetic recording medium according to claim 5, which is a fluorosilicone compound represented by: