JPS618724A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium having moderate softness and excellent still characteristic and durability by providing a prescribed layer contg. >=1 kind among 2 kinds of specified phosphoric esters and a urethane resin having a yield point in a specified range. CONSTITUTION:One or more kinds of phosphoric ester expressed by formula I or formula II [R is 8-30C alkyl or acrylalkyl, and (n) is 1-20] and a urethane resin, as the resin having a yield point in the stress range 50-600kg/cm<2>, contg. preferably a cyclic hydrocarbonic group in the main chain of polyetherdiol, polyesterdiol, and diisocyanate and having a glass transition point in the range -30-+100 deg.C are mixed along with magnetic powder to obtain a magnetic layer 2. A backcoat layer 3 contg. said compd. and nonmagnetic powder of SiO2, Al2O3, etc. and an overcoat layer 4 contg. said urethan resin are further provuded to obtain the magnetic recording medium. Consequently, the medium with good dispersibility of magnetic powder, etc. and having excellent traveling stability, mechanical strength, etc. is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

2. Prior Art Generally, magnetic recording media are manufactured by applying a magnetic paint containing magnetic powder, binder resin, etc. onto a support and drying it.

In such magnetic recording media, urethane resin is generally used as a binder resin for magnetic layers and the like. Conventionally known urethane resins are synthesized from polymeric diols, diisocyanates, chain extenders, and crosslinking agents (used as necessary).

Examples of polymeric diols include polyester diols obtained from adipic acid, butanediol, etc., polyether diols, and polycarbonate diols, and diphenylmethane diisocyanate and the like can be used as diisocyanates.

Further, the chain extender may be ethylene glycol, butanediol, etc., and the crosslinking agent may be polyols, polyamines, etc.

However, although such general urethane resin has excellent flexibility, it lacks hardness, so the mechanical strength of the magnetic recording medium is poor in sliding contact with guide bottles, magnetic heads, etc. Moreover, there are problems in terms of runnability and powder shedding.

On the other hand, in magnetic recording media, it has been known for a long time to add lecithin (which contains natural phosphoric acid ester as a main component and contains several kinds of higher fatty acids) to magnetic paints as a dispersant.

However, when lecithin is added, satisfactory results cannot be obtained with a medium using finely divided magnetic powder, and there is a drawback that the calender roll is easily soiled during the calendering process.

With the development of recent magnetic recording media, when urethane resin or lecithin, which is merely soft, is included in the magnetic layer, it is necessary to improve the durability of the medium during running, the stability of still images, and the quality of fine magnetic powder. Dispersibility etc. are insufficient.

3. Purpose of the Invention The purpose of the present invention is to provide a magnetic layer etc. with appropriate flexibility, sufficient mechanical strength and durability, excellent runnability, dispersibility of magnetic powder, surface properties of the magnetic layer, and static stability. An object of the present invention is to provide a magnetic recording medium with improved image durability.

4. Structure of the invention and its effects, that is, the magnetic recording medium according to the invention comprises at least a urethane resin having a yield point and each phosphoric ester represented by the following general formula (A-1) or (A-2). It is characterized in that one kind is contained in a predetermined layer (particularly a magnetic layer or a BC layer) on a support.

General formula (A-1): R-0-(CH2CH20)n-P-OHOH General formula (A-2): (However, in each of the above general formulas, R is an alkyl group having 8 to 30 carbon atoms or (alkylaryl group, n is a real number from 1 to 20) According to the present invention, compared to the characteristics of conventional urethane resins shown by curve a in FIG. Since we use urethane resin that has a yield point YPi of YP and above exhibit the property of elongating with stress without breaking, and have appropriate flexibility and binding strength as a binder resin. As a result, the mechanical strength of the magnetic recording medium is improved, damage such as wear during sliding contact, powder falling, etc. are significantly reduced, and running properties are also significantly improved. In particular, magnetic tape for VTF-use has no edge bending, and the control track near the edge can be maintained to maintain its function for a long time. The above yield point YP is important for the performance of urethane resin, and is preferably 100 to 560 KP/d, preferably 100 to 560 KP/d.
/cr! stress range (approximately 290 K in the example in Figure 1)
It is desirable that a yield point exists at r /ct/i ).

If the range in which the yield point exists is set to a stress of 50 Kr/i or more, the resin can be prevented from becoming too soft, and if it is set to 6004 Kr/i or less, the resin can be prevented from becoming hard and brittle.

In order to exhibit the above-mentioned excellent performance, the urethane resin having a yield point preferably has a cyclic hydrocarbon residue in the molecule. This cyclic hydrocarbon group residue is preferably a saturated cyclic hydrocarbon residue.

These include divalent or monovalent cyclopentyl groups, cyclohexyl groups, etc., or derivatives thereof (for example, alkyl groups such as methyl groups, and halogen substitutes such as chlorine atoms). These saturated cyclic hydrocarbon residues are desirable from the viewpoint of imparting appropriate hardness to the urethane resin and from the viewpoint of raw material handling efficiency. Further, the bonding position of this cyclic hydrocarbon residue is preferably in the main chain of the urethane resin molecule, but it may be bonded to the side chain thereof. Also,
By changing the amount of components having cyclic hydrocarbon residues in the urethane resin, an arbitrary glass transition point (Tg
) e can be obtained, and the Tg is -30'C to 100C, preferably 06C to 90C. Setting the Tg to -(9)3 or more prevents the film from becoming too hard (Tg<-(capital)°C), thereby preventing a decrease in film strength. It can prevent it from becoming brittle.

Further, according to the present invention, the general formula (A-1) or (A
-2) By using phosphoric acid ester, magnetic powder etc. can be well dispersed while maintaining the stability of the magnetic paint over time, and the surface properties of the magnetic layer etc. can be completely improved. It is possible to solve the problem.

In the general formula of the phosphoric acid ester used in the present invention, R should have 8 to 30 carbon atoms, but having 8 or more carbon atoms improves compatibility with the binder and This is because it is desirable in terms of preventing movement within the atmosphere, and it is desirable that the thickness be less than 100% in order to prevent poor dispersion of magnetic paints and the like and to maintain appropriate hydrophilicity of phosphoric acid residues. The number of carbon atoms is preferably 10 to 24. In particular, as for R, in alkylaryl, it is desirable that n be 1 or more and 1 or less, since the lipophilic group and the hydrophilic group are appropriately separated.

Further, the above phosphoric acid ester has an HLB of 10 to 14 (H
hydrophilic -Lipophilic B
a1ance (hydrophilicity-lipophilic balance) is desirable. That is, if the HLB is smaller than 10, the lipophilic property becomes strong, and if the HLB is larger than 14, the hydrophilic property becomes strong, and in either case, it is undesirable as a dispersant for magnetic paint etc. in terms of poor dispersion and stability over time of dispersion. There is. Note that the above-mentioned phosphoric acid ester may contain a trace amount of triester.

Specifically, the above-mentioned phosphoric acid esters include exemplified compounds.
■ Exemplary compound ■ OH Exemplary compound ■ OH Exemplary compound ■ OH Exemplary compound ■ Exemplary compound ■ Exemplary compound ■ CaHIy-o-(CT(2CH20), -P-OH and/or its silicate ester ■ OH Exemplary compound ■ OH Exemplary compound Compound (1) OH Exemplary Compounds O Examples of compounds include O.

The amount of the phosphoric acid ester added to the layer should be within an appropriate range; in the case of a magnetic layer, it is preferably 1 to 10 parts by weight, more preferably 2 to 7 parts by weight, based on 100 parts by weight of magnetic powder. good.

By adding more than 1 part by weight, sufficient dispersion can be achieved and the surface properties of the layer can be improved, and by adding less than 10 parts by weight, the viscosity of the coating material can be increased to make it easier to control the film thickness. The urethane resin used in the present invention can be synthesized by reacting a polyol and a polyisocyanate.

At this time, in order to introduce all of the above cyclic hydrocarbon residues, the following (
Methods 1) to (4) can be adopted.

(1) A method in which a polyhydric alcohol containing a cyclic hydrocarbon residue in advance is used as a raw material for a polyol (for example, a polymeric diol).

(2) A method in which a dicarboxylic acid having a cyclic hydrocarbon residue in advance is used as an organic dibasic acid (dicarboxylic acid) serving as a raw material for the polyol.

(3) A method in which the polyhydric alcohol and dicarboxylic acid of (1) and (2) above are used as raw materials for polyol.

(4) A method of using a polyhydric alcohol containing a cyclic hydrocarbon residue in advance as a chain extender, in combination with any of the above (1) to (3), or alone.

For example, as a synthesis method for obtaining the above urethane resin, 1,
4-di-hydroxymethylcyclohexa(CH,), -
A method of methylene-bis-phenylisocyanation of a polyester polyol obtained from COOH) is mentioned. In this case, the chain extender can be the above-mentioned 1,4-di-hydroxymethylcyclohexane or other diols (for example butane-1,4-diol).

As the above-mentioned polyhydric alcohol which may have a cyclic hydrocarbon residue in advance, those having a cyclohexyl group in the molecular chain of an ethylene glycol structure can be used as described above, but in addition to such a structure, propylene glycol, Glycols such as phthylene gelicol and diethylene glycol, or polyhydric alcohols such as trimethylolpropane, hexanetriol, glycerin, lt/yjimehama/71iX;/,yhexanetriol, trimethylolethane, and pentaerythritol, or these glycols. or those having a cyclic hydrocarbon residue in their structure can be used. Further, usable dibasic acids include phthalic acid, dimerized sulfuric acid, maleic acid, etc., or those having a cyclic hydrocarbon residue in their molecules.

In place of the above polyol, S-caprolactam, α-
Lactone polyester polyols synthesized from lactams such as methyl-1-caprolactam, S-methyl-5-caprolactam, and γ-butyrolactam; or polyether polyols synthesized from ethylene oxide, butylene oxide, etc. may also be used. .

These polyols are reacted with isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and metaxylylene diisocyanate, thereby synthesizing urethanized polyester polyurethanes and polyether polyurethanes.

These urethane resins according to the present invention usually mainly include:
Produced by the reaction of polyisocyanate and polyol,
It may be in the form of a urethane resin or urethane prepolymer containing free isocyanate groups and/or hydroxyl groups, or it may be in the form of a urethane resin or urethane prepolymer containing free isocyanate groups and/or hydroxyl groups, or it may be in the form of a urethane resin or urethane prepolymer that does not contain these reactive end groups (for example, a urethane distomer type).

Further, usable chain extenders may be the polyhydric alcohols exemplified above (which may or may not have a cyclic hydrocarbon residue in the molecule).

In addition, if a phenoxy resin and/or vinyl chloride copolymer is also included as a binder resin in addition to the above-mentioned urethane resin, the dispersibility of the magnetic powder will be improved when applied to the magnetic layer, and its mechanical strength will be increased. do. 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 base layer or base layer is improved.

It is expressed by the following general formula.

For example, PKHClPKHH manufactured by Union Carbide
, PKHT, etc.

In addition, as for the vinyl chloride copolymer that can be used, the molar ratio derived from 2 and m is 95 to 50 molti for the former unit, and 5 to 50 molti for the latter unit. be. Further, X represents all monomer residues 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 (λ10m) 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, the dispersibility deteriorates. The vinyl chloride copolymer described above may be partially hydrolyzed.

As the vinyl chloride copolymer, preferably vinyl chloride-
A copolymer containing vinyl acetate is hereinafter referred to as a "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 [VAGHJ, l'-V, YHHJ, 1-VMCH
J, "Eslec A" and "Slec A-" manufactured by Tanemizu Kagaku ■
5], "S-LEC C", "S-LEC M", "Denkabinir 1000 GJ", "Denkabinir 100OWJ" manufactured by Denki Kagaku Kogyo ■, 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. Cellulose inorganic acid esters, nitrocellulose, cellulose sulfate, cellulose phosphate, etc. can be used. Further, cellulose organic acid esters, acetyl cellulose, propionyl cellulose, phthyryl cellulose, etc. can be used. Among these cellulose resins, nitrocellulose has the best resistance.

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, when the content exceeds ω% 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 10,000 to ZO 0,000, and a polymerization degree of about 2.
For example, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, 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 layer containing the urethane resin. It is desirable that this carbon black has electrical conductivity, but carbon black with light-shielding properties may also be added. Examples of such conductive carbon black include Conductex x, manufactured by Columbia Carbon Co., Ltd.
) 975 (Specific surface area 250m"7g, particle size 24m
μ), Conductex 900 (specific surface area 125 d/g
, particle size 27 mμ), Cabot's Vulkay (Cab
ot Vul can) XC-72 (specific surface area 25
4m/g1 particle size 30mμ), Raven 1040.420
, Mitsubishi Kasei ■ Nosu 44, etc. As the light-shielding carbon black, for example, Raben 2000 manufactured by Columbia Carbon Co., Ltd. (specific surface area 190 m''7g, particle size 18 mμ
), 2100.1170.1000, # made by Mitsubishi Kasei ■
100, #75, N40, #A, N (9), etc. can be used. Carbon black preferably has a particle size of 30 mμ to 21 mμ, preferably 21 to 29 mμ, but if its oil absorption is 90 mfl (DBP) / 100 g or more, it tends to form a stracture structure and has higher conductivity. It is desirable in that it shows

For example, as shown in FIG. 2, a layer containing the above-mentioned urethane resin having a cyclic hydrocarbon residue as a binder resin,
This is the magnetic layer 2 of the support 1. In addition, as a powder, r-F
e, 0. , Co-containing - Fe208, Fe3O4, Co
Contains Fe50. Iron oxide magnetic powder such as; Fe, Ni1Co,
Fe-Ni-Co alloy, Fe-Mn-Zn alloy, Fe
-Ni-Zn alloy, Fe-Co-N'i-Cr alloy,
Fe-Co-Ni-P alloy, Co-Ni alloy, etc.Fe,
Examples include various ferromagnetic powders such as metal magnetic powders containing Ni, Co, etc. as main components.

The magnetic layer 2 also contains a lubricant (e.g. silicone oil,
graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of a monobasic fatty acid with 12 to 20 carbon atoms (e.g. stearic acid) and a monohydric alcohol with 13 to 100 carbon atoms), abrasives ( For example, fused alumina), antistatic agents (for example, 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,
α-Fe, Os, talc, kaolin, calcium sulfate,
Boron nitride, zinc fluoride, molybdenum dioxide, calcium carbonate, etc., preferably carbon black (
In particular, those made of conductive carbon blank) and/or titanium oxide may 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. 2 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). Further, the BC layer 3 may also contain the urethane resin according to the present invention.

Further, as the material of the support 1, plastics such as polyethylene terephthalate and polypropylene, metals such as i, Zn, glass, BN, .Si carbide, ceramics such as porcelain and 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, in addition to the polyfunctional polyisocyanates mentioned above, triphenylmethane triisocyanate, tris-(p-isocyanate phenyl) thiophosphite, polymethylene polyphenylisocyanate, etc.; Diisocyanate type is preferable.

FIG. 3 shows another magnetic recording medium.
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 R,a≦0.01 μm, Rmax≦0.13 μm, especially in relation to color S/N.
It is better to set it to m. In this case, it is desirable to use a smooth support 1 with a surface roughness of Ra≦0.01 μm1Rmax≦0.13 pm.

FIG. 4 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.

5. Examples 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.

The components shown in Table 1 were placed in a ball mill and dispersed. After filtering the magnetic paint through a 1 μm filter, 5 parts of polyfunctional incyanate was added, and the mixture was coated onto a support to a thickness of 5 μm using a reverse roll coater. The mixture was supercalendered, and each portion was slit into a 2-inch width to make a videotape (corresponding to the number of each Example and Comparative Example). 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.
(See margin below, next page) Table 1 The following measurements were performed on the videotapes from each side described above.

Chroma 8/N: Color video noise meter [8hibasoku92
Measured by 5D/IJ.

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

(Unit: dB) Jitter value: Using VTR jitter meter 1'-MK-612Aj manufactured by Megguchi Electronics Co., Ltd., at (9) °C, 80
Each jitter was measured after running 0 times and 100 times under high temperature and high humidity conditions of %R and H.

Glossiness: Measured with a variable angle photometer at an angle of 60°, and expressed with the value of Comparative Example 1 as 100 inches (the larger the value, the better the surface smoothness).

Table 2 shows the performance of each example of deotape.

Table-2 However, chroma 8/N of ratio-1, 几F with actual-1 as OdB
I asked for the output.

Chroma S/N of ratio -2 with actual -2 as OdB.

The R and F outputs were determined.

Jitter is each value.

The above results show that the tape performance is significantly improved by adding phosphoric acid ester 1111')/'tJFlf'fr: to the magnetic layer according to the present invention.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an enlarged sectional view of a portion showing the relationship between the stress elongation ratio of urethane resin. In addition, in the symbols used in the drawings, 2...
Magnetic layer 3: back coat layer (BC layer) 4: overcoat layer (OC layer).

Claims (1)

[Claims] 1. Urethane resin having a yield point and the following general formula (A-
A magnetic recording medium characterized in that at least one of the phosphoric esters represented by 1) or (A-2) is contained in a predetermined layer on a support. General formula (A-1): ▲There are mathematical formulas, chemical formulas, tables, etc.▼ General formula (A-2): ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in each of the above general formulas, R is a carbon atom (8 to 30 alkyl groups or alkylaryl groups, n is a real number of 1 to 20.)