JPS6352323A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a binder which exhibits high affinity to magnetic powder and to improve the dispersibility of even the finely pulverized magnetic powder or the magnetic powder having a large quantity of magnetization by using a phenoxy resin contg. a sulfonic acid group or metallic salt group of sulfonic acid as a polar group in the molecule as the binder for a magnetic layer. CONSTITUTION:The magnetic layer of a magnetic recording medium formed with the magnetic layer essentially consisting of the ferromagnetic powder and binder on a nonmagnetic base contains the phenoxy resin having the sulfonic acid group or metallic salt group of sulfonic acid at the side chain as the binder. The amt. of the polar group to be introduced into the phenoxy resin, into the side chain of which is introduced the hydrophilic polar group, is preferably 0.01-0.35mmol/g. The mol.wt. of the phenoxy resin is preferably in a 5,000-100,000 range at the time of preparing a magnetic coating compd. The phenoxy resin into which the sulfonic acid group or metallic salt group of sulfonic acid is introduced may be used in combination with other binders.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a binder contained in a magnetic layer formed on a non-magnetic support. This is related to the improvement of.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the magnetic layer has a sulfonic acid group or a sulfonic acid metal base in a side chain. By incorporating phenoxy resin as a binder, we aim to improve the dispersibility of the magnetic powder and the surface properties of the magnetic layer, improving the durability and magnetic properties of the resulting magnetic recording medium.

This is an attempt to improve electromagnetic conversion characteristics.

[Conventional technology]

In recent years, there has been a demand for improved magnetic properties and electromagnetic conversion properties in magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), in order to obtain high playback output even when recording at short wavelengths. ing.

As a way to achieve this goal, we developed finer particles of magnetic powder.

In addition to increasing the magnetic force, the packing density of magnetic powder in the magnetic layer, so-called puffing density, is increased (the amount of spray is increased).

On the other hand, conventionally used binders for magnetic recording media include vinyl chloride-vinyl acetate copolymer, vinyl chloride-propionic acid copolymer, and vinyl chloride-vinyl acetate copolymer.
Examples include vinyl chloride-based binders such as vinyl alcohol copolymers, among which the hydroxyl groups of vinyl alcohol contribute to the dispersibility of magnetic powder, and the active hydrogen of the hydroxyl groups reacts with isocyanate compounds to form a crosslinked structure. form=i
Vinyl chloride-vinyl acetate-vinyl alcohol copolymers are widely used because of their increased mechanical strength.

[Problem that the invention seeks to solve]

However, due to the increase in the specific surface area due to the finer particles of the magnetic powder and the increase in cohesive force due to the high magnetizing force, the above-mentioned binders cannot provide satisfactory dispersibility and surface properties, and the puffiness of the magnetic powder has increased. It has also become difficult to increase king density.

Therefore, the durability, magnetic frame properties, and electromagnetic conversion characteristics were also insufficient.

In addition, methods have been considered, such as using a surfactant as a dispersant, but in this case, since the surfactant is a low molecular weight, the presence of this surfactant in the magnetic layer causes yi Problems have arisen in terms of mechanical strength and durability, such as swelling and blooming due to changes over time.

Therefore, the present invention was proposed in order to eliminate the above-mentioned drawbacks in the technical field, and provides a binder that has excellent dispersibility of magnetic powder and good coating strength, thereby improving durability. The object of the present invention is to provide a magnetic recording medium with excellent magnetic properties and electromagnetic conversion properties.

[Means for solving problems]

As a result of long-term intensive research to achieve the above-mentioned objective, the present inventors have discovered that phenoxy resin having a sulfonic acid group or a sulfonic acid metal group in its side chain exhibits high affinity for magnetic powder. Heading The present invention has been completed in a magnetic recording medium in which a magnetic layer mainly consisting of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the magnetic layer has side chains. It is characterized by containing a phenoxy resin having a sulfonic acid group or a sulfonic acid metal base as a binder.

The phenoxy resin used in the present invention has excellent axillary strength and is manufactured from, for example, bisphenol A and epichlorohydrin. Its basic structure is shown by the following structural formula (1).

(However, in the formula, n represents an integer of 20 to 200.) In order to introduce a sulfonic acid group or a sulfonic acid metal base as a hydrophilic polar group into the above-mentioned phenoxy resin, the hydroxyl group of the side chain of the above-mentioned phenoxy resin is used. The compound may be modified with a compound having a group capable of reacting with active hydrogen and a sulfonic acid group or a sulfonic acid metal base in the molecule.

A compound having a group capable of reacting with active hydrogen and a sulfonic acid group or a sulfonic acid metal base in its molecule may be represented by the following formula (wherein, in the above polar group, X represents an alkali metal such as Na, etc.). ) and the like.

These compounds are synthesized as follows.

CN Specific examples of compounds include the following.

CN When a compound having a group capable of reacting with active hydrogen and a sulfonic acid group or a sulfonic acid metal base in its molecule is reacted with a phenoxy resin, the remaining N GO
The group reacts with the 10H group in the phenoxy resin to obtain a phenoxy resin into which a sulfonic acid group or a sulfonic acid metal group, which is a hydrophilic polar group, is introduced.

The specific reaction formula is as follows.

C.O. C.0 It can also be synthesized by the following method.

That is, a compound containing a hydrophilic polar group and chlorine in the molecule and a phenoxy resin having a polyfunctional OH group are dissolved in a solvent such as dimethylformamide or dimethyl sulfoxide in which both components are soluble, and lysine, - In the presence of amines such as picoline and triethylamine: dehydrochlorination agents such as epochino compounds such as ethylene oxide and propylene oxide. There is a method of introducing a hydrophilic polar group by a dechlorination reaction between an H group and chlorine. The reaction formula is as follows.

” CICJ4SO4Na In the phenoxy resin synthesized as described above in which a hydrophilic polar group is introduced into the side chain, the amount of polar group introduced is 0.
It is preferably 01 to 0.35 mmol/g. If the introduced amount is less than 0.01 m mol/g, the dispersibility of the magnetic powder will be poor, and the
If it is less than +aol/g, the solubility in the solvent will deteriorate and the moisture resistance of the coating film will deteriorate.

Furthermore, the molecular weight of the phenoxy resin is preferably within the range of 5,000 to 100,000 when preparing a magnetic coating material. If the molecular weight is 5,000 or less, durability will be poor, and if it is 100,000 or more, solubility in solvents will deteriorate.

The above phenoxy camellia butter into which a sulfonic acid group or a sulfonic acid metal base has been introduced may be used with other binders, l! : May be used in combination. As such a binder, those conventionally used as binders for magnetic recording media can be used, including vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride -Vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer.

Acrylic acid ester-acrylonitrile copolymer.

Acrylic acid ester-vinylidene chloride copolymer.

Methacrylic acid ester-vinylidene chloride copolymer.

Methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose Derivatives, styrene-butadiene copolymers, polyester resins, phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins.

Examples include urea-formaldehyde resins and mixtures thereof. Among these, polyurethane resins, polyester resins, acrylonitrile butadiene copolymers, etc., which are said to impart flexibility, are preferred.

In the magnetic recording medium of the present invention, the magnetic layer is formed by coating the surface of the nonmagnetic support with a magnetic paint prepared by dispersing ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent. Ru.

Here, the nonmagnetic support material (e) may be any material that is normally used in this type of magnetic recording medium, such as polyesters such as polyethylene terephthalate, polyethylene, polypropylene, etc. polyolefins, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, polyamide, and polyamideimide, paper, aluminum, and copper. metals, aluminum alloys, etc.
Examples include light alloys such as titanium alloys, ceramics, and single crystal silicon. Examples of the forms of this non-magnetic support include film and tape.

It may be a sheet, disk, card, drum, etc.

Moreover, any ordinary ferromagnetic powder can be used as the ferromagnetic powder used in the magnetic layer. Therefore, ferromagnetic powders that can be used include ferromagnetic iron oxide particles,
Examples include ferromagnetic chromium dioxide, ferromagnetic alloy powder, macrogonal barium ferrite fine particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed by the general formula FeOx, that is, Maghemai) (r-FeJ3°X=], 5
0), magnetite (Fe*Oa, X = 1
．． 33) and their solid solutions (FeOx, 1.33<X
<1.50). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.
There are different types.

The above-mentioned ferromagnetic chromium dioxide may include CrO, or Ru and Sn for the purpose of improving coercive force thereof.

A material containing at least one of Te, Sb, Fe, Ti, V, Mn, etc. can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fe-Ni, Fe-Co-Ni, C0-N
i, Fe-Co-B, Fe-Co-Cr-B.

Mn-B1. Mn-A1. Fe-Co-V, etc. can be used, and A1. Si
, Ti, Cr, Mn, Cu, Zn, and other metal components may be added.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
Rust inhibitors and the like may also be added.

The constituent materials of the magnetic layer described above are prepared as a magnetic paint by dissolving it in an organic solvent and coated on a non-magnetic support.The solvent for the magnetic paint may be acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketones, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, acetic acid glycol monoethyl ether, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.
Aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, methylene chloride and ethylene chloride.

Tetracarbonized carbon L chloroform, ethylene chlorohydrin,
Examples include chlorinated hydrocarbons such as dichlorobenzene.

[Effect]

As mentioned above, by using a phenoxy resin containing a sulfonic acid group or a sulfonic acid metal base as a polar group in the molecule as a binder, the affinity for magnetic powder is greatly improved, resulting in ultrafine magnetic powder. Even magnetic powders with a large amount of magnetization can be dispersed well.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

First, a phenoxy resin containing a sulfonic acid group or a sulfonic acid metal base was synthesized.

Synthesis Example 1 Using a phenoxy resin having an average degree of polymerization of 50, it was modified with a compound represented by the following formula at a rate of 0.03 mmol/g to obtain Polymer A.

Synthesis Example 2 A phenoxy resin having an average degree of polymerization of 50 was used and modified with a compound represented by the following formula at a rate of 0.07 mmol/g to obtain Polymer B.

Synthesis Example 3 Using a phenoxy resin having an average degree of polymerization of 50, it was modified with a compound represented by the following formula at a rate of 0.14 mmol/g to obtain Polymer C.

Synthesis Example 4 Using a phenoxy resin having an average degree of polymerization of 50, it was modified with a compound represented by the following formula at a rate of 0.07 mmol/H to obtain Polymer D.

Synthesis Example 5 Using a phenoxy resin having an average degree of polymerization of 60, it was modified with a compound represented by the following formula at a rate of 0.07 mmol/g to obtain Polymer E.

Next, a magnetic recording medium was produced using the polymer (phenoxy resin having a sulfonic acid group or a sulfonic acid metal base) obtained in the above synthesis example.

Example 1 Polymer A 12 parts by weight Lubricant (dimethyl silicone oil) 1 part by weight Lubricant (hexyl laurate) 1 part by weight Dispersant (lecithin) 1 part by weight Abrasive (Crz
Oi) 3 parts by weight Antistatic agent (carbon) 2 parts by weight Methyl ethyl ketone
100 parts by weight methyl isobutyl ketone
50 parts by weight toluene
5 hats 1 part The above composition was mixed in a ball mill for 48 hours, and filtered if! After passing, add a hardening agent,
After further mixing for 30 minutes, this was applied onto a polyethylene terephthalate film of 16 μm so that the film thickness after drying was 6 μm. Next, after performing a magnetic field orientation treatment, it was dried and wound up. After calendaring this, 1
The sample tape was cut to a width of /2 inches.

Example 2 A sample tape was prepared in the same manner as in Example 1 except that Polymer B was used instead of Polymer A in Example 1.

Example 3 A sample tape was produced in the same manner as in Example 1 except that Polymer C was used instead of Polymer A in Example 1.

Example 4 A sample tape was produced in the same manner as in Example 1 except that Polymer D was used instead of Polymer A in Example 1.

Example 5 A sample tape was produced in the same manner as in Example 1 except that Polymer E was used instead of Polymer A in Example 1.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that Polymer A contained in the coating solution in Example 1 was made of only an unmodified phenoxy resin with an average degree of polymerization of 50 that does not modify polar groups. A tape was made.

Comparative Example 2 Bottle added during the night of application and melting in Example 1
A sample tape was prepared in the same manner as in Example 1 except that A was made of an unmodified phenoxy resin with an average degree of polymerization of 60 that does not modify polar groups.

Surface gloss, powder removal, and still characteristics were measured for each sample tape obtained.

Note that the above surface gloss refers to the gloss needle (GLOSS METE).
R) under the conditions of incident angle 75@9 reflection angle 75''.In addition, powder falling was measured by visually observing the amount of powder falling on the head drum, guide, etc. after running the shuttle 100 times for 60 minutes. The still characteristics were evaluated using the deduction method (-5 to 0).
Record a 4.2 MHz video signal on a sample tape,
The time taken for the reproduction output to decay to 50% was taken as the time. The results are shown in the table below.

(The following is a blank space) This table also shows that each sample tape according to the present invention not only has excellent surface gloss and powder removal, but also has significantly improved still characteristics.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since the phenoxy resin containing a sulfonic acid group or a sulfonic acid metal base as a polar group in the molecule is used as a binder for the magnetic layer, it has a high affinity for magnetic powder, and even if it is made into ultrafine particles or has a high magnetization level. Even if the magnetic powder has a large amount, it will have good dispersibility. Therefore, the durability and surface properties of the obtained magnetic recording medium are improved, and the electromagnetic conversion characteristics are also extremely excellent.

Patent applicant: Sony Corporation Agent Patent Attorney Akira Koba Same stamp material Sakae

Claims (1)

[Claims] A magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the magnetic layer has a sulfonic acid group or a sulfonic acid metal base in the side chain. A magnetic recording medium comprising a phenoxy resin having the following as a binder.