JPS61107533A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a magnetic recording medium with which a high output and high S/N are obtd. and which has excellent heat resistance, durability, still image stability, etc. by incorporating a specific compd. which is solid at a room temp. into a magnetic layer. CONSTITUTION:The compd. which is expressed by the formula 1 and is solid at a room (or ordinary) temp. is incorporated into the magnetic layer. This compd. contributes to the improvement of the surface characteristic of the magnetic layer, etc. by dispersing satisfactorily magnetic powder into a magnetic paint while maintaining the stability of said paint with age; in addition, the compd. improves the heat resistance and durability of the medium as the compd. is solid at the room temp. More specifically, the compd. is solid at the room temp. and contains the arom. ring substd. by a residual aliphat. group and therefore the compd. can prevent the thermal and mechanical characteristic deterioration of the magnetic layer and contributes to the improvement in the durability (still image stability), heat resistance, etc. of the magnetic layer while maintaining satisfactorily the dispersibility. The high output and high S/N are thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it.

In such magnetic recording media, it is known to use gold phosphate ester as an additive to the magnetic layer. For example, Japanese Patent Publication No. 47-26882 discloses the use of a phosphate ester surfactant as one of the additives. Among phosphoric esters, those well known in the field of magnetic recording media include phosphoric esters, which are good compounds made by adding ethylene oxide to aliphatic alcohols or alkylphenols, and are used as dispersants. This is often expressed by the following formula (I). However, all compounds of formula (I) are liquid at room temperature.

RLO→C搗CH, O sound P-OH・・・・・・・・・・・・
...(I) (However, X is a hydroxyl group or R,'-〇-(CH
2CH, O aromatic group, R' is an alkyl group,
6 is an alkenyl group or an alkylphenyl group. )this(
Magnetic recording media using the phosphoric acid ester represented by the formula I) are described, for example, in Japanese Patent Publication No. 59-21087 and Japanese Patent Application Laid-Open No. 53-1989.
-15803 and Japanese Patent Publication No. 57-44970.

The present inventor conducted various studies on such known phosphoric acid esters, and as a result, discovered that they had the following problems. That is, in recent years, as the demand for high-density recording has increased and magnetic powder has become finer, the phosphoric acid ester of formula (I) used in conventional magnetic recording media has been
It was found that the /N ratio could not be improved sufficiently. That is, especially for video systems such as VH8 and Beta systems, higher-density 8-interval video, high-definition video, electronic still recording, high-density sheet recording, etc., adding conventional phosphate esters to the magnetic layer does not work. Only sufficient magnetic recording and reproducing characteristics can be obtained.

This is a fatal drawback that inevitably occurs because the phosphoric acid ester of formula (I) is liquid at room temperature.

C. OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that can provide high output and a high S/N ratio, and has excellent heat resistance, durability, still image stability, etc.

2. Structure of the invention and its effects, that is, the magnetic recording medium according to the present invention is a magnetic recording medium in which a magnetic layer contains a compound that is solid at room temperature (or normal temperature) and is represented by the following general formula.

A group represented by the general formula: + CHt CHt O+f (R is an aliphatic residue having 1 to 3 carbon atoms), n is a real number of 1 to 200. ) According to the present invention, the compound of the above general formula (hereinafter referred to as the "compound of the present invention") maintains the stability of the magnetic coating material over time, while favorably dispersing magnetic powder, etc., and forming a magnetic layer, etc. Not only can the surface properties be completely improved, but since it is solid at room temperature, the heat resistance and durability of the medium are greatly improved. That is, the compound of the present invention is solid (preferably wax-like) at room temperature and contains an aromatic ring substituted with an aliphatic residue, so that it prevents deterioration of the thermal and mechanical properties of the magnetic layer. It is possible to improve the durability (still image stability), heat resistance, etc. of the magnetic layer while maintaining sufficient dispersibility, and to obtain high output and high S/N ratio. The melting point of the compound of the present invention is preferably 20 to 70°C, more preferably 60'C or less, and particularly preferably 25 to 55°C. On the other hand, conventional phosphoric acid esters, especially the above-mentioned phosphoric acid esters of the formula (I), although containing a phenyl ring substituted with an alkyl group or an alkenyl group, are liquid at room temperature and therefore have no magnetic properties. It is thought that the heat resistance and still image stability, especially as a recording medium, deteriorate.

In addition, other known phosphoric acid esters that are liquid at room temperature have similar drawbacks, while those that do not have a phenyl ring, for example, by adding ethylene oxide to C1, H, -OH, phosphoric acid esters Esterified products have insufficient properties such as K and electromagnetic properties from a practical point of view, and their heat resistance and other properties are not suitable for practical use.

Regarding the compound of the present invention, n in the above general formula is 1 to 20.
It should be 0, especially numbers over 20 (e.g. 50
), the effects of the present invention can be fully exhibited.

Further, in order to efficiently disperse the magnetic powder and provide heat resistance and still image stability, it is desirable that n=3 to 150. Further, R should have 1 to 30 carbon atoms, but it is preferable to have a total number of carbon atoms of 1 or more in order to ensure good compatibility with the binder and to prevent movement within the layer. This is because it is preferable to make it less than 100% fine in order to prevent poor dispersion of magnetic paint and the like and to maintain appropriate hydrophilicity of phosphoric acid residues. The above number of carbon atoms is further 2~
24 is desirable. In this case, R is preferably an alkyl group, exhibits lipophilicity together with a phenyl group, and is an ethylene glycol residue (-+ CH, CH, O+)
exhibits hydrophilicity, so by adjusting the ratio of these two groups (especially n and common types), appropriate HL B
(Hydrophi lie -L 1pophil
ic Balance (hydrophilic-lipophilic balance) can be obtained.

Furthermore, in the above general formula, A is R-()0-(-C
When it is H, CH, O+T1, it becomes a diester, but when used, if this diester and a monoester in which A is a hydroxyl group are used together, a medium with preferable characteristics can be obtained. Of course, the monoester and the diester may be used alone.

In addition, -0Na, -OK, etc. may be used as A in the above general formula, but in this case, it is preferable to pre-treat the magnetic powder with the compound of the present invention before adding it to the paint.

Furthermore, in the compound of the present invention, nt-
By selecting HLB of the compound from 8 to 14
It is desirable to do so. That is, HLB is 8J
If the diameter is smaller than 14, the lipophilic property becomes strong, and if it is thicker than 14, the hydrophilic property becomes strong, and in either case, it may be undesirable as a dispersant for magnetic paints etc. in terms of poor dispersion and stability over time of dispersion.

The amount of the compound of the present invention added to the magnetic layer has an appropriate range, and is preferably 1 to 10 parts by weight, more preferably 2 to 7 parts by weight, based on 100 parts by weight of the magnetic powder. By adding 1 part by weight or more, the dispersibility, durability, etc. are sufficient, and the total surface properties of the layer are increased, and by adding 10 parts by weight or less, the viscosity of the paint is sufficient and the film thickness can be controlled. It becomes easier.

Further, when using the compound of the present invention, it is preferable to use a ketone type solvent such as methyl ethyl ketone, methyl isobutyl ketone, or a cyclic ether such as dioxane or tetrahydrofuran, and the compound is used after being dissolved or swollen in these solvents in advance. It is preferable to do so.

Specific examples of the compounds of the present invention are as follows, but are not limited thereto.

Exemplary compound ■ Exemplary compound ■ H Exemplary compound ■ H Exemplary compound ■ H Exemplary compound ■ H Exemplary compound ■ Exemplary compound ■ H Exemplary compound ■ H In the magnetic recording medium of the present invention, at least polyurethane can be used as the coating resin of the magnetic layer. However, it can be synthesized by reacting a polyol with a polyisocyanate. Polyols that can be used include phthalic acid,
Organic dibasic acids such as adipic acid, dimerized sulfuric acid, and maleic acid, and glycols such as ethylene glycol, fluoropylene glycol, phthalene gelicol, and diethylene glycol, or trimethylolethane, hexanetriol, glycerin, etc. Polyester polyol synthesized by reaction with polyhydric alcohols such as trimethylolethane and pentaerythritol, or any two or more polyols selected from these glycols and polyhydric alcohols; or S-caprolactam , lactone-based polyester polyols synthesized from lactams such as S-methyl-1-caprolactam, S-methyl-5-caprolactam, and γ-butyrolactam; or polyether polyols synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. Can be mentioned.

These polyols are reacted with incyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc., and thereby urethanized polyester polyurethane, polyether polyurethane, phosgene, or carbonated with diphenyl carbonate. Polycarbonate polyurethane is synthesized.

These polyurethanes are usually produced primarily by the reaction of polyisocyanates with polyols and are also in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups, or containing reactive end groups of these. (for example, in the form of a urethane elastomer).

Since the methods for producing polyurethane, urethane prepolymers, urethane elastomers, curing and crosslinking methods, etc. are well known, detailed explanation thereof will be omitted.

In addition, in the present invention, if a phenoxy resin and/or a vinyl chloride copolymer is contained in addition to the above-mentioned polyurethane as a binder resin, the dispersibility of the magnetic powder will be improved when applied to the magnetic layer, and its mechanical properties will be improved. Strength increases. However, if only the phenoxy resin and/or the vinyl chloride copolymer is used, the layer becomes too hard, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer is improved.

The phenoxy resin that can be used is a polymer obtained by polymerizing bisphenol A and epichlorohydrin, and is expressed by the following general formula.

(However, n. 2 to 13) For example, PKHClPKHH manufactured by Union Carbide
, PKHT, etc.

Further, as the above-mentioned vinyl chloride copolymers that can be used, there are those represented by the general formula: In this case, the molar ratio derived from a and m in is between 95 and 50 molar for the former unit and between 5 and 50 molar for the latter unit.

Further, X represents at least one member selected from the group consisting of all monomer residues copolymerizable with vinyl chloride, vinyl acetate, vinyl alcohol, maleic anhydride, and the like. (1
The degree of polymerization expressed as +m) is preferably from 100 to
600, and if the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and if it exceeds 600, the dispersibility becomes poor. The vinyl chloride copolymer described above may be partially hydrolyzed. The vinyl chloride copolymer is preferably a vinyl chloride-vinyl acetate copolymer (hereinafter referred to as
It is called "vinyl chloride-vinyl acetate copolymer." ). Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-maleic anhydride copolymers, and vinyl chloride-vinyl acetate copolymers. Among these, partially hydrolyzed copolymers are preferred. Specific examples of the above-mentioned vinyl chloride-vinyl acetate copolymers include O1'-VAGHj and [VYH
HJ, ``VMCHJ,'' S-LEC A manufactured by Kasumi Kagaku ■.
” “S-LEC A-5”, “S-LEC C”, [S-LEC MJ, “DENKABINI 7L/10” manufactured by Denki Kagaku Kogyo ■
00G'', [Denkabinir 100OWJ, etc. can be used.

In addition to the above, cellulose resins can also be used as binder resins, including cellulose ether,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. Cellulose ether! :L, -t”
C. Methyl cellulose, ethyl cellulose, etc. can be used. As the cellulose inorganic acid ester, nitrocellulose, cellulose sulfate, cellulose phosphate, etc. can be used. Further, as the cellulose organic acid ester, acetyl cellulose, propionyl cellulose, butyryl cellulose, etc. can be used. Among these cellulose resins, nitrocellulose is preferred.

In addition, regarding the entire binder composition, the ratio of the above-mentioned urethane resin to other resins (total amount of phenoxy resin, vinyl chloride copolymer, etc.) is 90/1 by weight.
Desirably 0 to 40/60, 85/15 to 45
155 has been found to be even more desirable. If the amount of urethane resin is outside this range, dispersion tends to be poor.
Also, if there is a large amount of other resins, surface properties tend to be poor.
In particular, if it exceeds (a) % by weight, the physical properties of the coating film become less favorable overall. In the case of vinyl chloride-vinyl acetate, it can be mixed with the urethane resin with a considerable degree of freedom, and preferably the urethane resin has a weight ratio of 15 to 75.

As the binder resin for the layer constituting the magnetic recording medium of the present invention, in addition to those mentioned above, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 2.
00 to 2,000, such as acrylic acid emether-acrylic nitrilo copolymer, acrylic acid varnish 2'
-Chlorinated ゞ=su 7''copolymer・7''su'. A '6.7-tele styrene copolymer or the like is used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. in particular,
Examples include phenol resin, epoxy resin, urea resin, melamine resin, and alkyd resin.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
Examples include maleic anhydride type, urethane acrylic type, and polyester acrylic type.

In the magnetic recording medium of the present invention, carbon black may be further added to the magnetic layer. It is desirable that this carbon black has electrical conductivity, but carbon black with light-shielding properties may also be added. As such conductive carbon black, for example, Conductex 975 manufactured by Columbia Carbon Co., Ltd. (specific surface area 250 m
/ g, particle size 24 mμ), Conductex 900
(specific surface area 125 m"/g, particle size 27 mμ), cuff 1", Cabot Vulca
n) XC-72 (specific surface area 254 m”/g,
(particle size: 30 mμ), Raven 1040.420, +44 manufactured by Mitsubishi Kasei ■, etc.

As the carbon black for light transmission, for example, G-Pen 2000clt surface area 190m manufactured by Columbia Carbon Co., Ltd.
/ g s particle size 18 mμ), 2100.1170.1
000, Mitsubishi Kasei ■ +100, ##75, -+40
, #a, #add etc. can be used. It is desirable for carbon black to have an oil absorption of 90 mp (DBP)/100 g or more because it tends to form a striated structure and exhibits higher conductivity.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
A magnetic layer 2 is provided on a support 1. Further, a Be layer 3 is provided on the opposite side of the magnetic layer 2. Although this Be layer may be provided, it is not necessary to provide it. The magnetic powder used for the magnetic layer 2, especially the ferromagnetic powder, includes r-Fe,
O,, Co-containing r-1! ”e20j, Fe3O4, CO
Contains Fe50. Iron oxide magnetic powder such as; Fe, Ni, Co
, Fe-Ni-Co alloy, Fe-Mn-Zn alloy, Fe-Ni-Zn alloy, Fe-Co-Ni
-Cr alloy, Fe-Co-N1-P alloy, Co-Ni
Alloy etc. Fe, Ni%C.

Examples include various ferromagnetic powders such as metal magnetic powders whose main components are Among these, Co-containing iron oxide and metal magnetic powder are preferable. Further, when the BET value of the magnetic powder is 25 m''/g or more, and furthermore 30 d/g or more, the effect of adding the compound of the present invention is significant.

The magnetic layer 2 also contains a lubricant (e.g. silicone oil,
graphite, molybdenum disulfide, tungsten disulfide, fatty acid ester consisting of a monobasic fatty acid having 12 to 2 carbon atoms (e.g. stearic acid) and a monohydric alcohol having 13 to 2 carbon atoms), abrasives (e.g. fused alumina), antistatic agents (e.g. graphite), etc. may be added.

The non-magnetic powder contained in the BC layer 3 includes carbon black, silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide, zinc oxide,
Examples include those made of α-Feρ3, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide, calcium carbonate, etc., and preferably those made of carbon black (especially conductive carbon black) and/or titanium oxide. .

Further, as the non-magnetic powder, organic powder such as benzoguanamine resin, melamine resin, phthalocyanine pigment, etc. may be added.

Further, the magnetic recording medium shown in FIG. 1 may be provided with an undercoat layer (not shown) between the magnetic layer 2 and the support 1, and may also contain a tan resin.

In addition, the material of the support body 1 includes plastics such as polyethylene terephthalate and polypropylene, AjL, Z
Metals such as n, glass, BN, Si carbide, ceramics such as porcelain, earthenware, etc. are used.

In addition, when coating and forming the above-mentioned magnetic layer, etc., it is desirable to add a predetermined amount of polyfunctional isocyanate as a crosslinking agent to the coating material. Examples of such crosslinking agents include the polyfunctional polyisocyanates mentioned above, as well as 7. =ya)l'7'
vItsaE-4,)lJx.

Examples include -(p-isocyanate phenyl) thiophosphite, polymethylene polyphenylisocyanate, and methylene diisocyanate type and tolylene diisocyanate type are preferable.

FIG. 2 shows other magnetic recording media.
A 00 layer 4 is provided on the magnetic layer 2 of the illustrated medium. This 00 layer 4 is provided to protect the magnetic layer 2 from damage, etc., and for this purpose, it needs to have sufficient slipperiness.

Therefore, as the binder resin for the 00 layer 4, the same urethane resin t- (preferably in combination with a phenoxy resin and/or a vinyl chloride copolymer) used in the above-mentioned magnetic layer 2 is used. The surface roughness of the 00 layer 4 is Ra≦0.01 μm, Rmax≦0.13 μm, especially in relation to the color 8/N.
It is better to set it to m. In this case, the surface roughness of the support 1 is R
It is desirable that a≦0.01 μm, Rmax≦0.13 μm, and that a smooth support is used.

FIG. 3 shows a magnetic recording medium configured as a magnetic disk, with magnetic layers 2.00 similar to those described above on both sides of the support 1.
Layers 4 are provided, and the 00 layer 4 may contain a binder resin containing the above-mentioned urethane resin as a main component.

E, Example Hereinafter, the present invention will be explained with reference to specific examples.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

After dispersing the ingredients shown in Table 1, apply 1μ of this magnetic paint.
After filtration with M filter, 5 parts of polyfunctional isocyanate was added, coated on a support to a thickness of 5 μm, supercalendered, 1 part was slit into 2-inch widths, and thio-tape (numbers for each example and comparative example) was added. ). However, the numbers after the second column of Table 1 represent parts by weight, and "actual" after the second column represents examples, and "ratio" represents comparative examples. (Margin below, next page) Table -
1 Mixture of monoester and diester (solid at room temperature (waxy): melting point 34-39°C, n in the above general formula
+50) Phosphoric acid esterification of the added product (liquid at room temperature 2 n+5 in the above general formula) * 3) C,, H,, -
Addition of ethylene oxide to OH is converted into a phosphoric acid ester to form the following product (solid at room temperature (waxy): melting point 42
~50°C) The following measurements were made on the videotapes from each side described above.

Chroma S/N: Color video noise meter “5hibasoku92
Measured by 5 D/I J.

Lumi S/N: R at 4MHz using the same R, F output RF' output measurement VTR deck
The F output was measured and the value after 100 reproductions was shown to be lower than the initial output.

(Unit: dB) Still image lifespan::; Indicates the time in minutes until the still image deteriorates by 2 dB. The larger the value, the higher the durability and wear resistance of the magnetic recording medium.

The performance of each example videotape is shown in Table 21C.

Table-2 However, for actual-1, actual-2, and ratio-3, calculate the chroma S/N and Lumi8/NXRF output using the value of ratio-1 as OdB.

Real-3, ratio-4 is chroma S with the value of ratio-2 as OdB.
/N1 Lumi S/N, R1i' appearance was determined.

The above results show that the tape performance is significantly improved by adding the compound of the present invention to the magnetic layer according to the present invention.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show embodiments of the present invention, and include FIGS. 1 and 2.
FIG. 3 is an enlarged cross-sectional view of a portion of a magnetic recording medium from each side. In addition, in the symbols used in the drawings, 2...
Magnetic layer 3e - Back coat layer (Be layer) 4... Overcoat layer (00 layer). Attorney Hiroshi Saka (self-motivated) Proceedings January 27, 1985 1. Indication of the case 1988 Patent Application No. 229548 2. Name of the invention Magnetic recording medium 3. Amendments made Relationship with the patent case Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name
(127) Konishiroku Photo Industry Co., Ltd. 4, Agent

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer contains a compound represented by the following general formula that is solid at room temperature. General formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ {However, A is a hydroxyl group or a group represented by -OM (M is an alkali metal), or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A group represented by (R is an aliphatic residue having 1 to 30 carbon atoms), and n is a real number of 1 to 200. }