JPS62167613A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve orientation and provide higher output by incorporating a phosphate having an alkyl phenyl group into a magnetic layer. CONSTITUTION:The phosphate having the alkyl phenyl group is incorporated into the magnetic layer. The magnetic powder to be used is CrO2 and has 15-35, more preferably 20-30 BET specific surface area and 5-15, more preferably 7-12 acicular ratio. The phosphate is a mono-, di- or triphosphate having the alkyl phenyl group and is more particularly preferably the monophosphate. The carbon atoms of the alkyl phenyl group are 7-36, more preferably 10-30. The amt. of the phosphate to be added into the magnetic layer is 1-10wt%, more preferably 2-5wt% per weight % of the CrO2 magnetic powder. The nonmagnetic substrate is exemplified by a PE terephthalate, PP, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with excellent electromagnetic properties.

[Prior art]

Magnetic recording media are generally formed by coating a magnetic paint, mainly consisting of magnetic powder and a binder, on a substrate such as plastic, but the reaction with the curing agent does not proceed during the preparation of the magnetic paint and during application. Therefore, it is necessary to process it promptly.

If the reaction with the curing agent proceeds before coating, the properties of the magnetic recording medium manufactured thereby, such as orientation,
Surface properties etc. deteriorate.

In order to deal with these problems, for example,
No. 30124 proposes using iron oxide as the magnetic powder, and then containing a phosphoric acid ester having an alkylphenyl group in which ethylene oxide or propylene oxide is added in an amount of 5 moles or less and having an alkylphenyl group. .

[Problems to be solved by the invention]

As a result of extensive studies, the present inventors have found that in a magnetic recording medium that uses CrO2 powder, which has a harder dispersibility than iron oxide powder, as the magnetic powder, a phosphoric acid ester having an alkylphenyl group is incorporated into the magnetic layer. To'f! It was discovered that specific and excellent effects can be obtained, leading to the present invention.

That is, the seventh object of the present invention is to provide a magnetic recording medium with excellent orientation and high output.

The second object is to provide a magnetic recording medium with good surface gloss and, as a result, excellent electromagnetic conversion characteristics.

[Means for solving problems]

The solution to the above problem is to mainly apply Cr 0 on a non-magnetic support.
2. A magnetic recording medium provided with a magnetic layer made of fine powder and a binder, characterized in that the magnetic layer contains a phosphoric acid ester having an alkylphenyl group.

The magnetic powder used in the present invention is CrO2, and BET
Specific surface area/j~3! , preferably 20 to 30, and the acicular ratio j~/! , preferably 7 to/2.

The phosphoric esters used in the present invention are mono-, di-, or tri-phosphoric esters having an alkylphenyl group, and among these, monophosphoric esters are particularly preferred. The number of carbon atoms in the alkylphenyl group is not particularly limited, but 7
-36, and preferably 10-30.

Furthermore, it is preferable that ethylene oxide or propylene oxide is further added to the phosphoric acid ester. The number of moles added is not particularly limited, but is preferably 4 to 10 moles, and more preferably %tA-coO. Among these, Tamol is particularly preferred.

The amount of phosphoric acid ester added to the magnetic j is 10% by weight, preferably λ to j, based on the CrO2 magnetic powder.

By adding the above phosphate ester into the magnetic layer,
Compared to the case of adding lecithin, which has been conventionally used in a Cr 02 -containing magnetic layer, the fractional properties of the coating liquid are significantly improved, and a magnetic recording medium with excellent orientation and electromagnetic variation characteristics can be obtained.

Examples of the nonmagnetic support used in the present invention include those commonly used in magnetic tapes, such as synthetic resin films such as polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, and polyimide. The thickness is generally 3 to jOμm, preferably j to 30μm.

A pack layer may be provided on the surface of the non-magnetic support opposite to the magnetic layer.

As the binder used for forming the magnetic layer of the present invention, commonly used thermoplastic resins, thermosetting resins, reactive resins, and the like can be used.

These resins can be used alone or in combination.

Thermoplastic resins generally have an average molecular weight of 10,000 to 2.
00,000, and the degree of engagement is about λθO to λ000. Examples of such thermoplastic resins include vinyl chloride/vinyl acetate copolymer resins, vinyl chloride/vinylidene chloride copolymers, acrylic resins, cellulose derivatives, various synthetic rubber-based thermoplastic resins, urethane distomers,
Examples include polyhinyl fluoride, polyamide resin, polyvinyl butyrate, styrene/butadiene copolymer, and polystyrene resin, and these can be used alone or in combination.

As a thermosetting resin or a reactive resin, it is generally a resin with an average molecular weight of λO 0,000 or less in the state of a coating solution, and after coating, the molecular weight becomes almost infinite due to a condensation reaction or a (gluing) reaction. However, if these resins have low heat curing values, it is preferable that the resin softens due to 7i0pA during the curing process and does not dissolve TFC. Examples include phenol/formalin novolac resin, phenol/formalin resol resin, phenol/furfural resin, xylene/formaldehyde resin, urea resin, melamine m fat, drying oil-modified alkyd resin, 7-1-
/- resin modified alkyd resin, maleic acid resin modified alkyd resin, unsaturated polyester resin, combination of epoxy resin and curing agent, terminal incyanate polyether moisture curable resin, polyisocyanate prepolymer, polyisocyanate prepolymer and active hydrogen For example, combinations of resins having the following can be mentioned, and these can be used alone or in combination.

The amount of binder used is based on ioo parts by weight of ferromagnetic powder.
generally in the range 10-100 parts by weight, preferably /j,
jOi'' is the range of the corner.

When producing magnetic 1- of the magnetic recording medium of the present invention, C
r 02 ferromagnetic powder and binder, and if necessary other granular fillers are kneaded together with a solvent to form a magnetic paint;
It is formed by coating on a support, applying magnetic field orientation, etc., and then drying.

As the solvent used during kneading, a solvent commonly used for preparing magnetic paints can be used.

For the kneading method, a method commonly used as a method for mixing wires in magnetic paints can be used. The order of addition of each ingredient can be set as appropriate.

Various techniques are known as techniques for preparing magnetic paints, and any of these known techniques can be used in manufacturing the magnetic recording medium of the present invention.

When preparing the magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. may also be used.

Next, the present invention will be explained using Example 1. “Part” in Examples
indicates parts by weight.

Example / CrO2 powder (5Brt;
Average particle size: 30 mμ) 2 parts polyisocyanate (manufactured by Nippon Polyurethane@; Coronate L1 3 parts ME
K, z o o part magnetic paint having the above composition; 14! ! L, the magnetic layer thickness after drying is 3
It was coated on a polyethylene terephthalate nonmagnetic support having a thickness of 0 μm.

The non-magnetic support coated with the magnetic paint is subjected to a magnetic field orientation treatment while the magnetic paint is still wet, and after drying, it is calendered and slit into l/λ inch widths to create a computer memory tape. Next.

The magnetic properties of this tape are determined by measuring B-Hdili (B: magnetic flux density, H: external magnetic field), and from this value Br (residual magnetic flux density) and degree of orientation (Br/Bm, B
Find the maximum magnetic flux density (m; maximum magnetic flux density).

Surface gloss level is incident angle 4c! 0. The total reflectance at a reflection angle of 0 was measured using a standard optical selectivity meter (digital standard monochromatic difference photometer AUD-GH-GVjl manufactured by Suga Test Instruments).

A magnetic tape was obtained in the same manner as in Example 1, except that Example 1 was replaced with a monoester of phosphoric acid.

Comparative Example/A magnetic tape was obtained in the same manner as in Example 1 except that phosphoric acid ester was not used.

Comparative Example A magnetic tape was prepared in the same manner as in Example 1 except for using the phosphoric acid ester of Example 1 as a wrench/(Centrolex R manufactured by Morton Chemical H) except for the K replacement hole.

Comparative Example 3 Instead of CrO2 in Example, C, Mr-Fe20s (S
By; 72 j m2 /f, ti-like ratio F l eil
lL7t [A friend who made magnetic tape in the same way.

The results are shown in Table 1.

Table/ [Effects of the Invention] The magnetic recording medium of the present invention has excellent orientation, output performance, and surface gloss.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer mainly composed of CrO_2 ferromagnetic fine powder and a binder provided on a non-magnetic support, characterized in that the magnetic layer contains a phosphate ester having an alkylphenyl group. magnetic recording medium.