JPS61142531A - 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, running durability, etc. by incorporating the aliphat. ester of glycerol and specific compd. into a magnetic layer. CONSTITUTION:The aliphat. ester of glycerol and the compd. expressed by the formula I are incorporated into the magnetic layer. The compd. expressed by the formula contributes to the improvement in the durability (more particularly still durability), heat resistance, etc. of the magnetic layer while maintaining substantially the dispersibility by the compd. itself as no substitutuents are incorporated at all into the phenyl group existing in the molecule of said compd. The high output and high S/N are thus obtd. The phenyl group in the molecule exhibits lipophilicity and rigidity and exhibits a hydrophobic property. On the other hand the residual ethylene glycol group {CH2CH2O} in the molecule exhibits hydrophilicity and therefore the adequate hydrophilicity-lipophilicity balance is obtd. by adjusting the ratio of both groups.

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 phosphate esters as additives 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 of compounds in which ethylene oxide is added to aliphatic alcohols or alkylphenols, which are used as dispersants. This is often expressed by the following equation (1).

R-0-←CH2CHz OH-P-OH...(1
)I (However, X is a hydroxyl group or R-0-+CHz CH20\-
In the group represented by R, R is an alkyl group, an alkenyl group, or an alkylphenyl group. ) Magnetic recording media using the phosphoric acid ester represented by (1) 2 are described in, for example, Japanese Patent Publications No. 59-21087, Japanese Patent Application Laid-open No. 15803-1983, and Japanese Patent Publication No. 44970-1987. .

On the other hand, Japanese Patent Publication No. Sho 41-18062 discloses that a fatty acid ester of a trihydric alcohol is contained together with an isocyanate compound in a binder resin.

According to Japanese Patent Application Laid-open No. 56-127932, it has been considered to use the above-mentioned phosphoric acid ester and glycerin fatty acid ester in combination, but it has been found that there are the following problems. In other words, in recent years, the demand for high-density recording has increased,
It was found that the problem could not be improved as the magnetic powder became finer. Especially for video formats such as VH3 and Beta formats, higher density 81 fl video, high definition video, electronic still recording, high density sheet recording, etc., even if conventional phosphate ester is added to the magnetic layer, the magnetic layer is insufficient. Only recording and playback characteristics can be obtained. Moreover, even if the phosphoric acid ester of the above formula (1) and the fatty acid ester of glycerin are used together, the S/N
The improvement in the ratio is still not sufficient, and the additive components seep onto the surface of the magnetic layer, resulting in poor running of the medium.

C.1 Objective of the Invention An object of the present invention is to provide a magnetic recording medium that can obtain high output and high S/N ratio, and has excellent heat resistance, durability, running stability, etc.

20 Structure and Effects of the Invention The magnetic recording medium according to the present invention is a magnetic recording medium in which the magnetic layer contains a fatty acid ester of glycerin and a compound represented by the following general formula.

General formula: The group represented by n and m are real numbers of 1 to 30.

In the process of arriving at the present invention, the inventors obtained the following new knowledge. Conventional phosphoric acid esters, especially those mentioned above (I)
Among the phosphoric acid esters of the formula, aromatic ones are used exclusively as dispersants to improve the dispersibility of magnetic powder, and the phenyl group in the molecule is substituted with an alkyl group to form an alkylphenyl group. Therefore, there was a strong preconception that the phenyl group would have poor dispersibility unless it had a substituent such as an alkyl group. is determined only by the physical properties of the phosphate ester itself,
When actually added to the magnetic layer, no consideration has been given to the compatibility with the various components of the magnetic layer or the behavior of the phosphate ester molecules in the magnetic paint. in this regard,
The above-mentioned conventional phosphoric acid esters have poor compatibility with other components in the magnetic layer because the substituted alkyl group of the alkylphenyl group present in the molecule causes steric hindrance or undergoes a certain movement. It is thought that the durability of the magnetic layer is reduced.

On the other hand, the compound of the present invention having the above general formula (hereinafter referred to as the "compound of the present invention") has no substituents introduced into the phenyl group present in the molecule, so the above-mentioned phenomenon occurs. It is possible to improve the durability (especially still durability), heat resistance, etc. of the magnetic layer while sufficiently maintaining its own dispersibility, and to obtain high output and high S/N ratio. In this case, the phenyl group in the molecule has lipophilicity and rigidity (r
igid) and exhibits hydrophobicity, while the ethylene glycol residue (-+CHzCHzO←) within the molecule exhibits hydrophilicity. By adjusting the ratio of these side groups, an appropriate HL B (Hydrophilic-Li
pophilic Balance (hydrophilic-lipophilic balance) can be obtained.

In the compound of the present invention, in the above general formula, n and m should be real numbers of 1 to 30 in order to maintain the dispersibility of the magnetic powder in the magnetic layer, and n and m should be real numbers of 2 to 20. If so, the dispersibility will be even better. Further, when A is , 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 applied 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, n, m in the above general formula
By selecting HLB of the compound from 8 to 1
It is desirable to set it to 4. That is, if the HLB is smaller than 8, the lipophilic property becomes strong, and if the HLB is larger 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 surface properties of the layer are improved, 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.

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

Exemplary compound ■ And/or this monophosphate ester example compound ■ Exemplary compound ■ Exemplary compound ■ H and/or this silicate ester example compound ■ Exemplary compound ■ And/or this silicate ester example compound ■ And/or this silicate ester Exemplary Compound (1) and/or its silicic acid ester Furthermore, in the present invention, it is extremely important that the above-mentioned compound of the present invention is used in combination with the fatty acid ester of glycerin. That is, compared to using glycerin fatty acid ester alone, when the compound of the present invention is used in combination, still image durability is improved, heat resistance is improved, running is stabilized, and S/N ratio is improved. It turns out that it can be improved. In this case, in the present invention, by using the compound of the present invention together with the fatty acid ester of glycerin, the amount of other fatty acid esters and fatty acids used can be reduced, and therefore the seepage of these additives can be prevented. It will be possible.

In addition, if an ester of an aliphatic monocarboxylic acid and a monohydric alcohol other than glycerin ester or an aliphatic carboxylic acid is used in combination with the ester of the present invention within a range that does not cause seepage, more stable running performance (jitter and skew) can be achieved. improvement)
can be obtained.

In the present invention, the amount of glycerin fatty acid ester added is preferably 0.005 to 2 parts by weight, and more preferably 0.01 to 1 part by weight, per 100 parts by weight of the magnetic powder. If the amount of ester is outside this range and the amount of ester decreases, the effect of improving running performance will be poor, and if the amount increases, the ester will easily seep out and the output will decrease.

The fatty acid ester of glycerin used in the present invention is preferably one obtained from glycerin and a fatty acid (saturated or unsaturated) consisting of a carboxylic acid having 6 to 30 carbon atoms, preferably 8 to 22 carbon atoms. The fatty acids used here include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, lilunic acid, linoleic acid, oleic acid, behenic acid, and the like.

Specific examples of glycerin fatty acid esters used in the present invention are shown below.

Exemplified compound ta+ Olive oil (natural product: mainly composed of esters of glycerin and various fatty acids) Exemplified compound (b) (X', X'':H or -COClsH:+:+)
Exemplified compound (C) (X', X': H or -COCl3H27) Exemplified compound (d) (X', I6: H or -COCl7H*s) Exemplified compound +e) (I7, I8: H or -COCl3H27 ) Exemplary compound (f) CH2-0-X” (I9, H2-0-X" (x + 3, Possible polyols include organic dibasic acids such as phthalic acid, adipic acid, azelaic acid, trimerized lyluic acid, and maleic acid, and glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol, or trimethylol. Polyester synthesized by reaction with polyhydric alcohols such as propane, hexanetriol, glycerin, trimethylolethane, and pentaerythritol, or any two or more polyols selected from these glycols and polyhydric alcohols. polyol; or
Lactone polyester polyols synthesized from lactams such as S-caprolactam, a-methyl-1-caprolactam, S-methyl-3-caprolactam, and r-butyrolactam; or synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. Examples include polyether polyols.

These polyols are reacted with isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc., resulting in urethanized polyester polyurethanes, polyether polyurethanes, and polycarbonates carbonated with phosgene or diphenyl carbonate. 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 represented by the following general formula.

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 l and m in is 95-50 mol% for the former unit and 5-50 mol% for the latter unit. Further, X represents a monomer residue copolymerizable with vinyl chloride, and represents at least one member selected from the group consisting of vinyl acetate, vinyl alcohol, maleic anhydride, and the like. The degree of polymerization expressed as (A+m) is preferably from 100 to 600; when the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and when it exceeds 600, dispersibility deteriorates. The vinyl chloride copolymer described above may be partially hydrolyzed.

As the vinyl chloride copolymer, preferably vinyl chloride-
Examples include copolymers containing vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymers"). 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 rVAGHJ, rV Y HHJ, and rVMCHJ manufactured by Union Carbide.
, "S-Resoku A" and "S-Lec A-" manufactured by Building Block Chemical ■
5'', ``Sresoku Cl', ``Slec M'', Denki Kagaku Kogyo's type [Denkabinir 1000 G J, ``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. As the cellulose ether, 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 60% 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 is 15 to 75% by weight.

In addition to the binder resins mentioned above, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used as binder resins for the layers constituting the magnetic recording medium of the present invention.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of io, ooo to 200,000, and a polymerization degree of about 200 to 2,000, such as acrylic acid ester-acrylonitrile copolymer, acrylic acid Ester-vinylidene chloride copolymers, acrylic ester-styrene copolymers, etc. are 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. Moreover, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, epoxy resin, urea resin,
These include melamine resin, alkyd resin, etc.

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. This carbon blank is preferably electrically conductive, but a light-shielding material may also be added. As such conductive carbon black, for example, Conductex 975 (specific surface area 250rd/
g-, particle size 24m#), Conductex 900 (specific surface area 125m/g, particle size 27mμ), Cabot Vulcan XC-72 (specific surface area 254n?/g, particle size 30mμ), Raben 1040
．． 420, Mitsubishi Kasei type #44, etc. As a light-shielding carbon black, for example, Raven 2000 manufactured by Columbia Carbon Co., Ltd. (specific surface area 190 m / g
, particle size 18m μ), 2100S1170.1000
#100, #75, #40, #35 manufactured by ゜Mitsubishi Kasei ■
#30 etc. can be used. It is desirable that carbon black has an oil absorption of 90 mf (DBP)/100 g or more because it tends to form a stracture 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 BCC 20 is provided on the surface opposite to the magnetic layer 2. Although this BC layer may be provided, it is not necessary to provide it. The magnetic powder used for the magnetic layer 2, especially the ferromagnetic powder, is fFe
zO3, CO containing y-Fezes, Fe30a, C
Iron oxide magnetic powder such as Fe5os containing o; F e , N
ss Co, Fe-Ni-Co alloy, Fe-Mn-Z
n alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-C
Examples include various ferromagnetic powders such as metal magnetic powders mainly composed of Fe, Ni, Go, etc., such as r alloy, Fe-Go-Ni-P alloy, and Go-Ni alloy. Among these, CO-containing iron oxide and metal magnetic powder are preferable. Further, when the BET value of the magnetic powder is 25rd/g or more, and furthermore 30rrr/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,
Graffite, molybdenum disulfide, tungsten disulfide, fatty acid ester consisting of a monobasic fatty acid having 12 to 20 carbon atoms (e.g. stearic acid) and a monohydric alcohol having 13 to 26 carbon atoms, etc.) Abrasives (e.g. Fused alumina), antistatic agents (eg graphite), etc. may be added.

Non-magnetic powders containing BCC20 include carbon black, silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide, zinc oxide,
α-FezO: +, talc, kaolin, calcium sulfate, boron nitrogen, zinc fluoride, molybdenum dioxide, calcium carbonate, etc., preferably carbon black (especially conductive carbon black) and/or titanium oxide. Can be mentioned.

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, or may not be provided with an undercoat layer (not shown). Same below). The support may also be subjected to corona discharge treatment. Also,
BCC50 may also contain a compound according to the present invention.

In addition, as the material of the support body 1, plastics such as polyethylene terephthalate and polypropylene, Als
Metals such as Zn, glass, BN, Si carbide, ceramics such as porcelain, and earthenware 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 in order to strengthen the magnetic layer. Examples of such crosslinking agents include the polyfunctional polyisocyanates mentioned above,
Triphenylmethane triisocyanate, tris-(p
-isocyanate phenyl) thiophosphite, polymethylene polyphenylisocyanate, etc., methylene diisocyanate type and tolylene diisocyanate type are preferable. Note that when the magnetic layer is cured by electron beam irradiation or the like, the addition of the isocyanate compound may be omitted, but it may be added.

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 urethane resin used for the magnetic layer 2 described above is used (preferably in combination with a phenoxy resin and/or a vinyl chloride copolymer). The surface roughness of the 00 layer 4 is preferably Ra≦0.01 μm and Rmax≦0.13 μm, especially in relation to color S/N. In this case, the surface roughness of the support l is Ra≦0
．． 01#m, Rmax≦0.13 μm, and it is desirable to use a smooth support l.

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 an M filter, 5 parts of polyfunctional isocyanate was added, coated on a support to a thickness of 5 μm, supercalendered, and 1 part was slit into 2-inch widths and recorded on videotape (each example, comparative number). ). 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.

■ ■ *2)
The following measurements were made on the videotapes according to each row above.

Chroma S/N: Color video noise meter
Measured using 925D/IJ.

Rumi S/N: Same as above.

RF output at 4MHz using a VTR deck for measuring RF output.
The output was measured, and after 100 playbacks, it showed a value that was lower than the initial output.

(Unit: dB) Skew value: A color par signal recorded on a magnetic tape is run on a videotape at a high temperature and humidity of 30°C and a relative humidity of 80%, and when the number of runs reaches 100, the monitor The image distortion at the switching point on the screen is measured and expressed in ps.

Still image lifespan: Shows the time in minutes for a still image to degrade 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 2.

Margin below, continued on next page.

Table 2 However, for Actual 1 and Actual 2, the chroma S/N, Lumi S/N, and RF output were determined using the value of ratio -1 as OdB. Fruit-3 is
Chroma S/N, Lumi S/N, with the value of ratio -2 as OdB,
The RF output was determined.

A "bad" winding state means that there are many irregularities on the end surface of the tape wound state, and a "good" winding state means that there are very few irregularities.

The above results show that the tape performance is significantly improved by adding each ester of the present invention to the magnetic layer based on the present invention.

[Brief explanation of drawings]

The drawings illustrate embodiments of the invention, and FIGS. 1, 2, and 3 are enlarged cross-sectional views of a portion of a magnetic recording medium from each side. In addition, in the symbols used in the drawings, 2...
Magnetic layer 3: back coat layer (BC layer) 4: overcoat layer (00 layer). Agent Patent Attorney Hiroshi Aisaka Figure 1 Figure 2 Figure 3 (Voluntary) Procedures Neighborhood Publications February 28, 1985 1. Indication of the case 1988 Patent Application No. 264202 2. Name of the invention Magnetism Recording medium 3, relationship with the case of the person making the amendment Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name
(127) Roku Konishi Photo Industry Co., Ltd. 4゜Agent address: FINE Building 66, 2-4-11 Shibasaki-cho, Tachikawa-shi, Tokyo Number of inventions increased by 7 amendments, column for detailed explanation of inventions in the specification subject to amendment (1), "13" on page 22, line 15 of the specification is corrected to "3". One or more -

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer contains a fatty acid ester of glycerin and a compound represented by the following general formula. 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 n, , m is a real number from 1 to 30.)