JPS6055512A - Magnetic recording body - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic and durability with a magnetic recording body consisting of providing a magnetic layer dispersed with ferromagnetic powder in a binder by adding polyester having a carboxylic group at least at one terminal of the molecular chain to the binder. CONSTITUTION:Polyester of about 200-5,000mol.wt. having a carboxylic group at least at one terminal of the molecular chain is incorporated into a binder. The polyester is obtainable by using excessively dicarboxylic acid in the stage of condensing polyol and dicarboxylic acid. If the mol.wt. of the polyester is smaller than about 200, the adjustment of the mol.wt. is difficult and synthesis is difficult. If said wt. is larger than about 5,000 no improvement is observed in the dispersibility of ferromagnetic powder and is therefore said wt. is undesirable. The mol.wt. of the polyester is more particularly preferably about 400- 1,000. The polyester is used at about 0.1-10wt%, more preferably about 1- 5wt% by the weight of the ferromagnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium having excellent electromagnetic conversion characteristics and running durability.

2. Description of the Related Art Magnetic recording media, particularly audio cassette tapes, have recently been used for music recording, so there is a demand for tapes with well-developed frequency characteristics and excellent original sound reproduction capabilities. Also, with the spread of car stereos, radio-cassette players, etc.
It is also required to have excellent runnability and durability.

On the other hand, extremely high-density recording has become possible on video cassette tapes by shortening the recording wavelength and narrowing the track width.

Therefore, there is a demand for tapes with high output, high S/N ratio, and excellent ability to reproduce original images. Also, the total thickness is 408m
Although the VTR has become thinner and thinner, due to the spread of portable VTRs, the running durability of the VTR is far superior to that of conventional VTRs.
TR tape is requested.

That is, there is a strong demand for audio and video tapes that have better electromagnetic conversion characteristics, runnability, and durability than conventional tapes.

Various additives have been proposed for this purpose, but
At present, it is difficult to obtain anything that completely satisfies the above requirements.

Currently, as additives, especially dispersants for ferromagnetic powder, various surfactants, particularly fatty acid salts, phosphoric esters, alkyl sulfonates, sulfoconolinates, N-acyl sarcones, etc. are mainly used.

However, when using these conventional dispersants, magnetic paint v! Although the dispersibility of ferromagnetic powder improves when manufacturing 4,
The magnetic layer obtained by coating and drying the magnetic paint on a support deteriorates in strength, moisture resistance, etc., and tends to cause runnability problems in high temperature and high humidity conditions. Many of the tires had poor running durability.

In addition, silane coupling agents, which improve the wetting of the ferromagnetic powder and the binder and improve the durability of the magnetic layer,
Various coupling agents such as titanium coupling agents have been studied, but these coupling agents do not react sufficiently with the ferromagnetic powder and may even worsen the dispersibility of the ferromagnetic powder. As a result, electromagnetic conversion characteristics often deteriorate.

Therefore, it has been difficult to fully satisfy the electromagnetic characteristics and durability required for development using conventional additives.

As a result of intensive studies on various additives, the present inventors found that a magnetic recording material with particularly excellent electromagnetic conversion characteristics and durability can be obtained when a polyester having a carboxyl group at at least one end of the molecular chain is added. The present invention was achieved by discovering that this can be done.

The purpose of the present invention is, firstly, to provide a novel magnetic recording medium, secondly, to provide a magnetic recording medium with excellent electromagnetic conversion characteristics, and thirdly, to provide excellent running properties, An object of the present invention is to provide a magnetic recording medium having durability.

The above object of the present invention is to provide a binder having a carboxyl group at least at one end of the molecular chain, with a molecular weight of about λooNz.
This can be achieved by including ooo polyester.

The above polyester is obtained by using an excess of dicarboxylic acid during the condensation of polyol and dicarboxylic acid.

The polyol used in the present invention is a polyol having two or more hydroxyl groups in seven molecules, and preferably has carbon atoms of λ to 1.

Specific examples include ethylene glycol, diethylene glycol, triethylene glycol, probilene glycol, butylene glycol, pentamethylene glycol,
Diols such as hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol, etc. Triols such as glycerin, trimethylolzolonol, etc., polyols such as pentaerythritol There is. Among these, diols are particularly preferred.

The dicarboxylic acid used in the present invention is a carboxylic acid having two carboxyl groups in one molecule, and preferably has 1 to 1 carbon atoms. Also, instead of dicarboxylic acid, tricarbo/
Polycarboxylic acids such as acids can also be used or used in combination.

Specific examples include dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, superric acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, and terephthalic acid. There are tricarboxylic acids such as carballylic acid and benzenetricarballylic acid.

Among these, dicarboxylic acids are particularly preferred.

51 If the molecular weight of the polyester of the present invention is less than about -00, it will be difficult to adjust the molecular weight and synthesis will be difficult, and if it is more than about 500, no improvement will be seen in the dispersibility of the ferromagnetic material, which is not preferable.

It is particularly preferred that the polyester used in the present invention has a molecular weight of about 100 to 100.

The polyester of the present invention is approximately θ,/− with respect to the ferromagnetic powder.
/θ weight percent, preferably about /−j weight percent is used.

Examples of the binder used in combination with the copolymer of the present invention include vinyl chloride-vinyl acetate copolymers, vinylidene chloride copolymers, polyester resins, polyurethane resins, epoxy resins, polyisocyanates, and the like. These binders exhibit excellent dispersion effects when used in combination with the copolymers of the present invention.

The polyester resin used in the conventional co-liquid type polyurethane resin has hydroxyl groups at both ends, and is completely different from the polyester used in the present invention, which has carboxyl groups at the molecular ends.

6 - The magnetic recording material of the present invention is manufactured by applying and drying a binder composition, a magnetic paint containing a ferromagnetic powder, additives, etc. dispersed together with an organic solvent onto a support.

Ferromagnetic powders include r-Fe203, CO-modified iron oxide,
In addition to ferrites such as modified barium ferrite and modified strontium ferrite, alloy fine powders containing iron as a main component are particularly preferred.

The particle size of the ferromagnetic powder is preferably 7 μm or less, particularly 0°jμ or less, and ferromagnetic powders having an acicular shape, a rice grain shape, or a flat plate shape can also be used.

For details on ferromagnetic powders, additives, organic solvents, dispersion, coating methods, etc., see JP-A No. 101-101.
It is described in Ko/10j, No. 114011, etc.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention should not be limited to these Examples.

In the examples, "parts" indicate "parts by weight."

Example 1 r -F a 203 (Hc # 000s, average particle length 0.4!pm) 100 parts vinyl chloride/vinyl acetate/vinyl alcohol copolymer (copolymerization ratio 2=3: j1 degree of polymerization 1700) / J part polyester polyurethane copolymer (molecular weight approximately 50,000, composition is shown in Table 1, addition amount is shown in Table 2) 5 parts myristic acid C part methyl ethyl ketone Iro part cyclohexanone J part The above composition was batch-sanded. After cross-dispersion in a grinder for 3 hours, P was filtered with a filter having an average pore size of 3μ.
Through this process, a magnetic paint was obtained.

The resulting coating solution was applied onto a polyethylene terephthalate film having a thickness of 7 μm to a dry thickness of jμ, and while the coated layer was still wet, it was subjected to a magnetic field orientation treatment using a too Gauss electromagnet and dried. After drying, the magnetic layer was smoothed by sous and e-calendering. Slit this, 3
．． A rim-width audio cassette tape (Philips type compact cassette) was obtained.

The characteristics of the obtained audio tape are shown in Table λ Sample A/
−j'.

Comparative Example 1 An audio cassette tape was obtained in the same manner as in Example 1, except that a polyester having a hydroxyl group at the terminal was used instead of the copolymer in Example 1.

The characteristics of the obtained audio tape are shown in Table 2 Sample AC
-/~C-B.

Example 2 CO-adhered beltlide iron oxide (Coj.

Oatomic%, FeO/, q, Hc4I00e,
Average particle length 0, J μm)/00 parts vinyl chloride/
Vinyl acetate/maleic anhydride copolymer (copolymerization ratio rt", i3:l1 degree of polymerization ta00) 10 parts polyester polyurethane copolymer (molecular weight approximately 50,000, composition shown in Table 1, amount added in Table 2) ) 2-Myristic acid 1 part Butyl stearate 1 part α-alumina 5 parts Conductive carbon 3s After cross-dispersing the above composition in a batch type sand grinder for 3 hours,
Add 7 parts of 7jJ, disperse for 10 minutes, and filter through a filter with an average pore size of 1μ to obtain a magnetic paint.

The obtained coating solution was applied onto a polyethylene terephthalate film having a thickness of 41μ so that the dry thickness was jμ,
While the coating thickness was still wet, a magnetic field orientation treatment was performed using an electromagnet of 2000 Gauss, and the coating was dried. After drying, Sue? - The magnetic layer was smoothed by calendering. This was slit to obtain a 1/2 inch wide videotape (V Ha type).

The properties of the obtained tapes are shown in Samples MA to io in Table 3.

Comparative Example 2 A videotape was obtained in the same manner as in Example 2, except that the polyester in Example 2 was not used and a polyester having a hydroxyl group at the molecular end was used.Characteristics of the resulting videotape Table 3 Sample AC-7
~C-1i.

Example 3 Instead of Co-coated beltride iron oxide in Example λ, Fe-
Ni alloy fine powder (Fe:Nl=Riz:z.

A videotape was obtained in the same manner as in Example 1 except that HC/ j 00 Qe % acicular ratio lθ:/, average particle length 0.3 μm) was used.

The characteristics of the obtained videotape are shown in Table Sample A11~
Shown in No.

Comparative Example 3 A videotape was obtained in the same manner as in Comparative Example 3, except that the Fe--Ni alloy fine powder of Example 30 was used in place of the Co-coated beltlide iron oxide in Comparative Example 3. The characteristics of the obtained videotape are shown in sample AC-/C-/A.

The methods for measuring the properties shown in Tables 2, 3 and 3 are shown below.

(a) Value obtained by dividing the residual magnetic flux density (Br ) by the maximum magnetic flux density (Bm) when measured with a rectangular ratio external magnetic field IKOe Cl0KA/m).

Measuring device: VaMj type (b) manufactured by Toei Kogyo Glossiness Measured in the longitudinal direction of the tape at the glossiness of the surface of the magnetic layer with an incident angle ψj01 and a reflection angle 4LAj'.

Measuring device: Suga Test Instruments KK GKljD type (c) MOL tape 16 Maximum output level of 3/sHz when C-/ is set to OdB (distortion rate of 3chi).

Measuring device: Nakanchi KK SR type (d) 80L Saturation output level of 10KHz when tape AC-/ is set to OdB.

(e) Audio performance using 100 commercially available cassette decks.
O'1AfLH and (jliO'C, IO'4RH-TJ
A row test was conducted to evaluate the quality of the roll.

A...No disordered winding◇ B.../-5 decks caused winding disturbances.

C...z, the deck of the io unit caused a disturbance in the winding.

D... 11 or more decks caused winding disorder.

(f) Dirt After evaluating the running performance, the degree of dirt on the deck head was evaluated.

A: There is no dirt at all, but even if there is, it is difficult to confirm.

B: There is some dirt, but it is not a problem.

C: There is quite a lot of dirt.

(ω Tape squeal During the running performance test, the presence or absence of tape squeal was evaluated.

A: No tape squeal at all.

B.../-Volume 2 Temporarily occurred.

C: Occurs temporarily in volumes 3 to j.

D: Temporary squealing occurs in 5 or more turns, and constant squealing occurs in 1-λ turns or more.

(h) Video output 4' MHz output when C-+ in Table 3 and C-// in Table 3 are set to OdB.

Measurement mga lower'14iKKIliN V-it
o o type.

(i) 8/N ratio 87N ratio of 10K-IMHz with viewpoint correction (measuring device: NY-ggoo type manufactured by Koshita Denki KK).

(j) Still life The time (in minutes) required for playback in still mode until significant defects appear on the screen.

Measuring machine: 4 under desk KKl! NY-At, oo type.

佽) Video running performance 1.2s 0C, to excellent R, H and g using 10 commercially available video cassette decks (VHa type).

A running test was conducted with 'C, rOLfLH, and jitter and skew were evaluated.

A: Neither sick nor skew.

B: Jitter or skew sometimes occurs, but there is almost no problem.

C...Jitter or skew is very low/
There is a problem with lr-.

(e) Increase in dropout The increase in dropout was measured at the same time as the video runnability measurement.

A...Increase of less than 20 cells/min B...Increase of less than 20 cells/minute C...Increase of less than 30 cells/minute D...Increase of 30 cells/minute or more According to Table 2, according to the present invention Audio cassette tape sample A/~At using polyester having a carboxyl group at the end of the molecule is tape sample 16C-/using no polyester according to the present invention, and tape sample AC-co~ using a polyester oligomer having a hydroxyl group at the end of the molecule. It was found that the squareness ratio and glossiness were larger than that of C-z, and the dispersibility of the ferromagnetic fine powder was excellent. In addition, it was found that the audio running performance and dirt resistance were excellent, and the running durability was excellent. Furthermore, from the results of Sample 40-4, it was found that as the molecular weight increases, the desired effect of the present invention becomes smaller.

According to Table 3, videotape sample 7f & 7~A// using the polyester having a carboxyl group at the end of the molecule according to the present invention is not used, tape C-7, and tape A using the polyester having a hydroxyl group at the end of the molecule
It was found that the gloss was higher than that of C-1-C-//, and the dispersion of ferromagnetic fine powder was excellent. In addition, the video output 8/N ratio is high, and the driving performance such as still life D and 0 increases,
It was also found to have excellent durability.

The same can be said for Table 1 and Table 3.

From the above results, it was found that the copolymer according to the present invention has excellent dispersibility of ferromagnetic powder, so it has excellent electromagnetic conversion characteristics, as well as excellent runnability and durability.

Patent applicant: Fuji Photo Film Co., Ltd. 20- 81-

Claims (1)

[Claims] In a magnetic recording body comprising a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support, the magnetic layer is made of polyester having a molecular weight of about 200 to 5000 and having a carboxyl group at least at one end of the molecular chain. A magnetic recording medium characterized by containing.