JPS6352322A - 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 tertiary amine 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 tertiary amine 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 tertiary amine 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, in which a phenoxy resin having a tertiary amine in the side chain is added to the magnetic layer as a binder. By including it as a magnetic powder, the dispersibility of the magnetic powder and the surface properties of the magnetic layer are improved, and the durability and magnetic properties of the resulting magnetic recording medium are improved.

This is an attempt to improve electromagnetic conversion characteristics, etc.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), have been required to have improved magnetic properties and electromagnetic conversion properties in order to obtain high playback output even when recording at short wavelengths. There is.

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

As the magnetic force is increased, there is a strong tendency to increase the packing density of magnetic powder in the magnetic layer, the so-called packing density.

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 the magnetic powder, and the active hydrogen of the hydroxyl groups reacts with incyanate compounds etc. to form a crosslinked structure. Vinyl chloride-vinyl acetate-vinyl alcohol copolymers are widely used because of their ability to form and increase the mechanical strength of coating films.

[Problem that the invention seeks to solve]

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

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

In addition, methods such as using a surfactant as a dispersant have been considered, but in this case, since the surfactant is a low molecular weight, the presence of this surfactant in the stone layer causes There are problems with mechanical strength and durability, such as powder shedding and blooming due to changes over time.

Therefore, the present invention has been 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 also provides good film strength, thereby making it durable. Magnetic properties that lend themselves to sex! An object of the present invention is to provide a magnetic recording medium with good magnetic conversion characteristics.

c. Means for Solving Problems] The present inventors have conducted intensive research over a long period of time to achieve the above-mentioned objectives, and have found that phenoxy resin having a tertiary amine in its side chain has a high affinity for magnetic powder. The present invention has been completed based on the discovery that the above-mentioned magnetic 3 layers on the side chain
It is characterized by containing a phenoxy resin having a class amine as a binder.

The phenoxy resin used in the present invention has excellent coating strength and is produced from, for example, bisphenol A and epichlorohydrin.

Its basic structure is shown by the following structural formula (1) (in the formula, n represents an integer of 20 to 200). This can be done by utilizing the hydroxyl group in the side chain of the phenoxy resin and modifying it with a compound having a group capable of reacting with active hydrogen and a tertiary amine in the molecule.

The compound having a group capable of reacting with active hydrogen and a tertiary amine in the molecule is expressed by the following formula (however, in any of the above polar groups, R has 1 carbon number
m represents 2 or 3, respectively. ) and the like.

These compounds are synthesized as follows.

Specific examples of these compounds include the following.

When a compound having a group capable of reacting with active hydrogen and a tertiary amine in its molecule is reacted with a phenoxy resin, the 1-NC○ group remaining in the former and the 10-H group in the phenoxy resin are reacted.
5 to obtain a phenoxy resin into which a tertiary amine, which is a hydrophilic polar group, is introduced.

The specific reaction formula is as follows.

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 then pyridine or picoline is dissolved. , amines such as triethylamine: There is a method of introducing a hydrophilic polar group by a dechlorination reaction between a 10 H group and chlorine in the presence of a dehydrochlorination agent such as an epoxy compound such as ethylene oxide or propylene oxide. The reaction formula is as follows.

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 preferable that it is 01-0.35mmol/g.

If the introduced amount is less than 0.01 m mol/g, the dispersibility of the magnetic powder will be poor, and 0°35 m H
If it is less than 1/g, the solubility in solvents 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 less than 5,000, durability will be poor, and if it is more than 100,000, solubility in solvents will deteriorate.

The phenoxy resin into which the tertiary amine has been introduced may be used in combination with other binders. Such binders include:
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-acetic acid and nyl-malein. Acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer , methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin.

Polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acronitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenolic resin ,Epoxy resin.

Thermosetting polyurethane resin, urea resin, melamine resin,
Examples include alkyd resins, urea-formaldehyde resins, and mixtures thereof. Among them, polyurethane resin, polyester resin, which is said to impart flexibility,
Acrylonitrile butadiene copolymer and the like are preferred.

In the magnetic recording medium of the present invention, the magnetic layer is formed by dispersing, for example, ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent.
It is formed by applying a magnetic paint made by PI to the surface of a non-magnetic support.

Here, the material for the non-magnetic support may be any material that is normally used in this type of magnetic recording medium, such as polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polypropylene, etc. cellulose derivatives such as cellucose triacetate, cellulose diacetate, and cellulose acetate butyrate; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; plastics such as polycarbonate, polyimide, polyamide, and polyamideimide;
Examples include paper, metals such as aluminum and copper, light alloys such as aluminum alloys and 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, magnetite (γ-Pet's -X=1.
50), magnetite (FeJa, X = 1-
33) and their solid solutions (FeOx, 1.33<X<
1.50). Furthermore, these ferromagnetic iron oxides have
Cobalt may be added for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

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, C.

-Ni, Fe-Co-B, Fe-Co-Cr-B.

Mn-B1. Mn-A1. Fe-Co-V, etc. can be used, and A! , 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 henzene, toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, methylene chloride and ethylene chloride.

Carbon tetrachloride, chloroform, ethylene chlorohydrin,
Examples include chlorinated hydrocarbons such as dichlorobenzene.

[Effect]

As mentioned above, by using a phenoxy resin containing a tertiary amine as a scratching group in the molecule as a binder, the affinity for magnetic powder is greatly improved, and it is possible to use ultrafine magnetic powder or a magnetic powder with a small amount of magnetization. Even large magnetic powders are well dispersed.

〔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 tertiary amine 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 with 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 equivalent to an average degree of polymerization of 50, it was mixed with a compound represented by the following formula to 0.07 m IIIot/
Polymer D was obtained by modifying the polymer at a ratio of 1.

Synthesis Example 5 Using a phenoxy resin with an average degree of polymerization of 60, it was mixed with a compound represented by the following formula to produce 0.07 m 1lol/g
Polymer E was obtained by modifying the polymer at a ratio of .

Next, a magnetic recording medium was produced using the polymer (phenoxy resin having tertiary amine) 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 Grinding agent (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
50 parts by weight of the above composition in a ball mill
After mixing in the dark at 8 o'clock and filtering with a filter, a curing agent was added and mixed for an additional 30 minutes, and this was coated on a 16 μm thick polyethylene terephthalate film so that mW of dry ffH1E was 6 μm.9 Then, a magnetic field was applied. After performing the orientation treatment, it was dried and rolled up. After calendering the tape, it was cut into a single 2-inch width to form a sample tape.

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 tape was prepared in the same manner as in Example 1 using Polymer A contained in the coating solution in Example 1 as an unmodified phenokine resin with an average polymerization ratio of 50 that does not modify polar groups. was created.

Comparative Example 2 A sample tape 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 phenokine resin with an average degree of polymerization of 60 that does not modify polar groups. was created.

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

The above surface gloss was measured using a gloss meter (GLO5S METE).
R) under the conditions of an incident angle of 75° and a reflection angle of 75°. Further, powder falling was evaluated by visually observing the amount of falling powder on the head drum, guide, etc. after running the shuttle 100 times for 60 minutes, and using a point deduction method (-5 to 0). The still characteristics are
Record a 4.2 M) lz video signal on a sample tape,
The time taken for the reproduction output to attenuate to 50% was taken as the time. The results are shown in the table below.

On the surface, it not only has excellent surface gloss and fade resistance, but also
It can be seen that the still characteristics have been significantly improved.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since phenoxy resin containing tertiary amine as a polar group in the molecule is used as a binder for the magnetic layer, it has a high affinity for magnetic powders, even if it is an ultrafine hexafunctional powder or a magnetic material with a large magnetization l. Even if it is a powder, it has 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 Oka stamp material Sakae (Issuance of procedural amendment) November 4, 1986

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 comprises a phenoxy resin having a tertiary amine in the side chain. A magnetic recording medium comprising a binder as a binder.