JPS60182014A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a binder compsn. for a magnetic layer which is good in compatibility with a polyester resin having good adhesiveness and is good in dispersibility and to obtain a tape having an excellent characteristic by contg. a specific polyester resin and specific urethane resin as a binder resin. CONSTITUTION:A binder resin contains at least a polyester resin having a -SO3M group (M is hydrogen or univalent alkali metal atom) at the side chain and urethane resin having a siloxane bond (silicone modified urethane). The polyester resin having the -SO3M group at the side chain is obtd. by copolymerizing sulfoisophthalic acid or sulfoterephthalic acid or metallic salt such as sodium or potassium thereof with a polyester resin. The silicone modified urethane is obtd. by substituting part of the polyol used for producing an ordinary urethane resin with a polyol or prepolymer having a siloxane bond or using isocyanate having a siloxane bond.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, magnetic disks, etc. More specifically, the present invention relates to improvements in binder resins used in magnetic recording media.

(2) Prior Art Magnetic recording media (hereinafter referred to as tapes) are generally produced by applying a magnetic paint containing magnetic powder and binder resin as main ingredients to a support and drying the coating.

The importance of magnetic powder, which plays a role in the magnetic recording mechanism in the tape, cannot be overstated, but it is important to maintain the magnetic powder in a convenient manner for carrying out the mechanism, and to maintain other auxiliary materials that complement the functions of the tape. The binder used to bind the tape is also very important and requires various electromagnetic, physical, and chemical properties.

For example, adhesion to the support, wetting properties for magnetic powder and non-magnetic powder such as abrasives, carbon bras, glue, etc. based on interfacial tension, dispersibility as a protective matrix, and overall tape function. The surface friction coefficient (sliding property) of the binder itself, adhesion, abrasion resistance, rigidity, elasticity, flexibility (flexibility), refractive fatigue resistance, solubility, compatibility between binder materials, solvent resistance, Although there are mutually contradictory properties such as heat resistance, weather resistance, and resistance to various low-molecular weight additives contained therein, it is necessary to promote each of them and not cancel them out.

In recent years, with the development of magnetic recording materials, magnetic tapes for video, computer, audio, etc. are required to have high tape performance. In video magnetic tapes and the like where the relative speed of the tape is high, a particularly wear-resistant binder is used to bind magnetic powders to form a magnetic layer. For example, polyurethane is said to have strong adhesion to other materials, to withstand repeated stress or bending, to be mechanically strong, and to have good abrasion resistance and weather resistance. Therefore, it is possible to use polyurethane as a binder for the magnetic layer, but it is known that polyurethane has a high coefficient of friction and poor surface lubricity, which increases the frictional force during tape running and causes poor running. There is. To prevent this,
Attempts have been made to mix other resins with polyurethane, add low molecular weight lubricating agents, etc. However, the compatibility between polyurethane and other resins is not so good, and the addition of low-molecular compounds tends to cause blooming, staining and clogging of the magnetic head, resulting in poor lightning and borium conversion characteristics.

Furthermore, since the film strength of the magnetic layer using polyurethane as a binder is insufficient, powder falling from the magnetic layer increases, causing an increase in dropouts.

For example, JP-A-56-137522 discloses a binder system that combines polyester and polyurethane, but the ester component improves heat resistance, but deteriorates moisture resistance and reduces solvent solubility. Therefore, the urethane concentration cannot be increased too much, resulting in a decrease in film strength.

For this reason, when a lubricant is used in combination, the amount of lubricant must be increased in order to control the lubricity of the entire binder and maintain film strength, but it is necessary to use a large amount of low-molecular-weight lubricant. This is inappropriate because blooming will occur.

Furthermore, by introducing a sulfonic acid metal base into the polyester resin, JP-A-56-74824, JP-A-56-7
4827, etc., improve surface smoothness (gloss) and adhesion to a support, JP-A-56-13519, JP-A-56-13519.
-74826, 56-74828, 56-74
No. 829, etc. discloses improvement of filling properties related to dispersibility and interfacial tension, and the sulfonic acid metal base-introduced polyester resin, polyurethane resin, nitrocellulose,
Vinyl chloride - 1t4t? Many proposals have been made for binder compositions based on combinations of hinyl resins and the like.

However, binders with these compositions cannot be said to have sufficient compatibility, dispersibility, or filling properties between the binder particles, resulting in problems with the stability of magnetic coatings and the gloss and surface roughness of finished tapes. However, the squareness ratio is poor, and the electromagnetic conversion performance is not sufficient.

As described above, no binder composition that has sufficient properties such as durability, heat resistance, moisture resistance, and mechanical strength has been proposed so far, and therefore the magnetic layer has poor durability and poor running properties. The reality is that fatal defects such as changes over time cannot be avoided.

(3) Purpose of the Invention The first object of the present invention is to provide a magnetic layer binder composition that has good adhesive properties, good compatibility with a polyester resin, and good dispersibility. The second purpose is
An object of the present invention is to provide a tape with excellent properties using a binder with good compatibility and dispersibility.

(4) Structure of the Invention The object of the present invention is to combine a polyester resin with a ferromagnetic powder and a binder (M is hydrogen or a monovalent metal atom) in its side chain, and a urethane resin (hereinafter referred to as This is achieved by using a magnetic recording medium that is characterized by using gold ore (silicon-modified urethane).

The polyester resin having 18O,M groups in the side chain according to the present invention (hereinafter referred to as sulfone-modified polyester) is obtained by adding sulfoisophthalic acid, sulfoterephthalic acid, or a metal salt thereof such as sodium or potassium to the polyester resin. Obtained by copolymerization. For example, the acid component (
For example, dimethyl terephthalate), a glycol component (for example, ethylene glycol), a dicarboxylic acid component containing a -803M group (for example, 5-sodium sulfoisophthalate), and other necessary components are added for a predetermined period of time to carry out an ester reaction, and then It is produced by adding and reacting sebacic acid, adipic acid, etc., and then polycondensing it under reduced pressure.

This sulpone-modified polyester has good wetting properties for magnetic powder, and therefore has good dispersibility and can be packed with magnetic powder at a high density, thereby increasing the dispersion and filling h1 of the magnetic powder.

Sulpone-modified polyester can generally be easily obtained by the synthesis method described above, but a detailed synthesis example can be found in JP-A-56-7482.
It is disclosed in No. 4, etc. and can be referred to.

Commercially available products include Bylon 530, Bylon GX, -W, and ET1095 manufactured by Toyobo.

Silicon-modified urethane is produced by replacing part of the polyol used in the production of normal urethane resin with a polyol or prepolymer having siloxane bonds.
or in the form of urethane resins or urethane prepolymers which contain free isocyanates or hydroxyl groups, or which do not contain these reactive end groups, for example in the form of urethane elastomers, obtained by using incyanates with siloxane bonds. It may be.

Preferred polyols in the present invention are polydialkylsiloxanesicarbisole, and the isocyanate is a low molecular weight isocyanate or polyisocyanate having two incyanate groups in the molecule, such as tolylene diisocyanate and hexamethylene diisocyanate. , isoborone diisocyanate, and diarylmethane diisocyanate.

The alkyl group of the polydialkylsiloxane sicarbinol is preferably a lower alkyl group, particularly a methyl group. Furthermore, an aryl group (particularly a phenyl group) may be used instead of an alkyl group.

The methods for producing urethane resins, urethane prepolymers, urethane elastomers, curing crosslinking, crosslinking methods, etc. are well known in the art, so detailed explanations thereof will be omitted.

A typical synthesis example of silicon-modified urethane is shown below.

Synthesis Example = 1 After exchanging +r' with nitrogen gas in a reactor equipped with a stirrer and a reflux condenser, 300 parts of methyl ethyl ketone (MEK) was charged, and polydimethylsiloxane dicarbinol (average molecular weight 1.000''160!, diphenylmethane- 4
, 175.4 parts of 4/-diisocyanate and 0.03 parts of diptyltin dilaurate were added, and the mixture was reacted at 80°C for 2 hours. To the above solution, 64.6 parts of neopentyl glycol, ME
After adding 100 parts of K and reacting at 80°C for 2 hours, 5 parts of isopropanol and 300 parts of M E K were added.
The reaction was carried out at ℃. The obtained polyurethane resin solution had a solid content of 34.6% and a viscosity of 5.900 centivoice (2
5°C), and the resin film obtained from this solution is
The stress at yield was 450 kg/CII, the elongation at yield was 5%, and the Young's modulus was 14.000 k-. (Measurement: il
5 mm rectangular sample (distance between gauge lines 50 〕I/'m),
Synthesis example: 2 After replacing the reactor with a stirrer and reflux condenser with nitrogen gas,
300 parts of M E * were charged, and further ω parts of polydimethylsiloxanesicarbinol (average molecular weight 1,800),
Diphenylmethane-4,4'-diisocyanate 167
．． 9 parts, add 0.3 parts of diptyltin dilaurate, 80
The reaction was carried out at ℃ for 2 hours. 63.1 parts of neopentyl glycol and 1 part of MEKJOO were added to the above solution, and after reacting at 80°C for 2 hours, 9 parts of triethanolamino and 1 part of MEKJOO were added.
300 parts of K was added, and the mixture was reacted at 80°C for 1 hour. The obtained polyurethane resin solution had a solid content of 31.4% and a viscosity of 2.500 centivoice (2!56C), and a resin film obtained from this solution had a yield stress of 500%.
kg/crl, elongation at yield 5%, Young's modulus 15,000
kg/d. (Measurement: 1415 drunken rectangular test f
1 (between gauge lines 50 ram, ), tensile speed 5 ram/min)
A commercially available product is PS-1046 manufactured by Mitsui Nisso Urethane.
etc.

The mixing ratio of sulfone-modified polyester and silicon-modified urethane is 5/95 to 9515, preferably 10 by weight.
/90 to 80/20, and the mixing ratio of the total Nl amount of the sulfone-modified polyester and silicon-modified urethane to other bindu is preferably 3/7 to 9/1 in terms of weight/fl ratio.

In the present invention, in addition to the sulfone-modified polyester and silicon-modified urethane, a cellulose-based resin and a vinyl chloride-based copolymer are also included as binders for the magnetic layer.
The dispersibility of the magnetic powder in the magnetic layer is improved and its mechanical strength is increased.

Usable cellulose resins include cellulose ethers such as methylcellulose, cellulose inorganic acid esters such as nitrocellulose, and cellulose organic acid esters such as acetylcellulose.

Among these cellulose resins, nitrocellulose is preferred.

The vinyl chloride copolymer is preferably a vinyl chloride-vinyl acetate copolymer.

Among vinyl chloride-vinyl acetate copolymers, partially hydrolyzed copolymers are preferred. The above-mentioned vinyl chloride copolymer and cellulose resin may be used in any blending ratio, but the weight ratio of vinyl chloride resin to cellulose resin is 9.
0/1 (preferably 1 to 5/95 80
/20 to 10/90 is more desirable.

If the amount of cellulose resin increases outside of this range (the ratio of the above mold is less than 5/95), the calendering processability tends to be poor, the surface properties become poor, and dropouts tend to occur. . In addition, when the amount of vinyl chloride copolymer increases (
If the above weight ratio exceeds 90/10), poor dispersion tends to occur, for example, the squareness ratio tends to deteriorate.

In addition, regarding the entire binder composition, the ratio of the total amount of the above-mentioned sulfone-modified polyester and silicone-modified urethane to the other resins (combined amount of cellulose resin and vinyl chloride copolymer) is calculated by weight. Ratio: 90/10~3
(It is desirable that it is 1/70, feather /15 ~ +50 /
40 has been found to be even more desirable. Outside this range, if the combined amount of sulfone-modified polyester and silicone-modified urethane is large, poor dispersion tends to occur and the still properties tend to deteriorate, and if the amount of other resins increases, surface properties tend to become poor and the still properties deteriorate. Especially 70
When the weight ratio exceeds %, the physical properties of the coating film become less favorable overall.

Further, as a binder for this magnetic layer, the above-mentioned binder according to the present invention, a mixture of this binder, a thermoplastic resin, a thermosetting resin, a reactive resin, an electron beam curable resin, and a thermoplastic resin may be used. good. The thermoplastic resin has a softening temperature of 150°C or less and an average molecular weight of 10.0.
00-200.000, degree of polymerization is about 200-2.00
For example, acrylic acid ester-acrylonitrile copolymer, methacrylic acid ester-styrene copolymer, polyhinyl fluoride, polyamide resin, polyester resin, amino resin, various synthetic rubber-based thermoplastic resins, and these. A mixture of etc. 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 reaches the limit 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. Specific examples include phenol resins, urea resins, alkyd resins, acrylic reaction resins, polyamine resins, and mixtures thereof.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
Examples include urethane acrylic type, polyester acrylic type, polyether acrylic type, and where □ is a polyfunctional monomer, ether acrylic type, urethane acrylic type, and the like.

Magnetic powders, especially ferromagnetic powders used in the magnetic layer according to the present invention include γ-Fe2O3, Co-containing r-4''e
2o3,i;”e,o4. Co-containing iron oxide magnetic powder such as Fe504 p Fes Ni % C0% Fe -N
i-Co alloy, pe-Mn-Zn alloy, pe-I
N+-Zn alloy, Fe-Co-Ni-Cr alloy,
Fe-Co-N1-P alloy, Co-N1 alloy, etc.Fe
Examples include various ferromagnetic powders such as metal magnetic powders containing , Ni, Co, etc. as main components.

The mixing ratio of the ferromagnetic powder and binder according to the present invention is 5 to 4 parts by weight of the binder per 100 parts by weight of the ferromagnetic powder.
00 parts by weight, preferably in the range of 10 to 200 parts by weight. If there is too much binder, the density of the tape will decrease; if it is too little, the strength of the magnetic layer will be poor, resulting in undesirable conditions such as decreased durability and powder falling off.

Furthermore, in order to improve the durability of the tape of the present invention, in addition to incyanate as a crosslinking agent, triphenolmethane triisocyanate, tris-(p-incyanate phenyl), and secondary bosphite are added to the magnetic layer. , polymethylene polyphenyl isocyanate.

The paint used to form the above-mentioned magnetic layer paint may contain additives such as dispersants, lubricants, abrasives, and antistatic agents, if necessary.

Dispersants used include lecithin, phosphoric acid esters, amine compounds, argyl sulfates, fatty acid amides, higher alcohols, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid esters, known surfactants, and salts thereof. , or a salt of a polymer dispersant with a negative group (e.g. -〇〇〇〇, -I'03H')? You can also use These dispersants may be used alone or in combination of two or more. These dispersants are used in an amount of 1 to 2 to the binder IooffW part.
It is added in an amount of 0 parts by weight. These dispersants may be used to pre-treat the magnetic powder in advance. In addition, as lubricants, silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, myristic acid, etc.

Fatty acid esters (so-called waxes) consisting of a monobasic fatty acid having 12 to 16 carbon atoms and a monohydric alcohol having 21 to n carbon atoms in total can also be used. These lubricants are added in an amount of 0.2 to 20 parts by weight based on 100 parts by weight of the binder. Abrasive materials that may be used include commonly used materials such as fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main ingredients: corundum and magnetite). These abrasives have an average particle diameter of 0.5 to 5 μm, particularly preferably 0.1 to 2 μm.
μ. These abrasives have a binder of 100 weight frI.
It is added in an amount of 1 to 20 parts by weight in addition to part C.

Examples of antistatic agents that may be used include carbon black, conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony arsenide compounds; natural surfactants such as saponin. Nonionic surfactants such as algylene ogizide, glycerin, and glycidol; Cationic surfactants such as higher alkylamines, quaternary ammonium salts, pyridine, other complex corals, phosphoniums, and sulfoniums; Carvone Anionic surfactants containing acidic groups such as acids, sulfonic acids, phosphoric acids, sulfuric ester groups, and phosphoric ester groups; Examples include amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of aminoalfur. .

Generally, when static electricity accumulates while using a tape, discharge occurs between it and the magnetic head, which tends to generate noise.
In addition, dust and the like may be attracted and cause mud or drop-out. Also a kite for the video. A method is known in which the running of the tape is adjusted by detecting the difference in light transmittance between the τL+, m-state LNh'-tape portions. It is required that the surface electrical resistance of the magnetic layer be 10+) Ωσ or less, and that the light transmittance of the tape portion where the magnetic layer is located be 005% or less. For this purpose, carbon black particles are usually added to the magnetic layer.

The carbon black used includes carbon black with a high stracture index value that imparts conductivity, and carbon black with a relatively low stracture index value that imparts light-shielding properties to the magnetic layer. is desirable.

Solvents for magnetic paint or solvents used when applying magnetic paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; fit-ffi methyl, and acetic acid. Esters such as ethyl, butyl acetate, ethyl lactate, ethylene glycol 1,000/acetate;
s; y z nI-r-Miru S] Ethers such as non-glycol ethyl ether, dioxane, and tetrahydrofuran; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride, ethylene chloride, and tetrachloride Carbon, chloroporum, halogenated softened hydrogen such as dichlorobenzene, etc. can be used.

Further, as the bare side of the support 1 according to the present invention, polyesters such as polyethylene terephthalate and polyethylene-2゜6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and polycarbonate are used. Plastics such as, gold such as All, Zn, etc.
Seven laminates of glass, silicon nitride, silicon carbide, porcelain, ceramics, etc.
etc. are used. The thickness of these supports is film,
In the case of a sheet, the thickness is approximately 3 to 100 μm, preferably 5 μm.
~50 tLm, and in the case of disk or card type,
The diameter is about 30 μm to 1107 II, and when it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used.

Further, in the present invention, an undercoat layer may be provided between the magnetic layer and the support, or no undercoat layer may be provided.

The tape of the present invention also has a back coat layer (BC kite:)
may be provided. The non-magnetic powder contained in the BC layer includes carbon black, oxide, silicon oxide, titanium oxide,
Aluminum oxide, chromium oxide, silicon carbide, calcium carbide, zinc oxide, α-pe2o3, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, Z molybdenum oxide, calcium carbonate, etc., preferably carbon black or oxide Examples include those made of titanium. If these non-magnetic powders are included in the BC layer, B
The surface properties of the Ci can be improved by appropriately roughening (matting it), and in the case of carbon bra, conductivity can be imparted to the BC layer to obtain an antistatic effect.1. 3. Power -
It is advantageous to use 4-men/thick in combination with other non-magnetic powders, since both the effects of improving surface properties (stabilizing runnability) and improving conductivity can be obtained. However, the surface roughness of the BC layer is determined by the average roughness or height of the center line of the surface roughness curve of the surface irregularities (Ra)
E 0.01-01 μm 1 preferably 0.025 μm or less, and the maximum roughness (Rmax) is 020-080
It is preferable to set it to μm. Regarding la, it is desirable to set Ra to -40,025 μm in order to improve the chroma S/N. If the value of Ra or )jmax is too small, running stability and the winding appearance during tape winding will be insufficient, and if it is too large, transfer will occur from the BC layer to the magnetic layer (during tape winding), making the surface even rougher. I'll sleep.

In addition, the particle size of the filler (including non-magnetic powder) in the BC layer is
In order to obtain the above surface roughness, it is less than 0.05 μm, preferably 0.
It is preferable that the thickness be 2 μm or less. In addition, the film thickness after coating and drying of the BC layer is O, J ~ 3.0 μm, preferably 1 μm or less,
Further, it is preferably 0.6 μm or less. The amount of non-magnetic powder added to the BC layer is generally 100 to 400 mfm'%, preferably 20
0-300 wheels 2.

Furthermore, if the same binder as that for the magnetic layer is used as the binder for the BC layer, it is advantageous in terms of reducing the amount of heat and heat.

In the present invention, the magnetic paint type or 13
Other coating methods for forming the magnetic layer or BC layer by applying the C layer solution include air doctor coating, blade coating, air knife foot, squeeze -+-), ti coating, reverse roll coating, transfer roll coating, and gravure coating. Coat, kiss coat, cast coat, spray coat, etc. can be used, and other methods are also possible. The magnetic layer coated on the support by such a method is optionally treated to orient the ferromagnetic powder in the layer, and then the formed magnetic layer is dried. Further, the tape of the present invention is manufactured by subjecting the tape to surface smoothing if necessary and cutting it into a desired shape.

(5) Examples Next, the present invention will be explained using specific examples.

Example-1 First, a magnetic paint having the following formulation was prepared.

(parts by weight) CO containing r-Fe2o, 100 Sulfone modified polyester (Pylon 530. Manufactured by Toyobo) 10 Silicon modified urethane (PS-1046).

Mitsui Nippon W7 Urethane fM') 7 Nitrocellulose (manufactured by Cellline Daicel) 7 A1203'-3 Carbon bran resin 5 Valmitic acid 05 Stearic acid 05 Cyclohexanone 50 Methyl ethyl ketone 50 Toluene 50 This composition was thoroughly stirred and mixed in a ball mill. , and further polyfunctional isocyanate (Coronate L manufactured by Nippon Polyurethane Co., Ltd.
) was added thereto, and then filtered through a filter with an average pore size of 1 μm. The obtained magnetic paint was applied to the surface of a polyethylene terephthalate base having a thickness of 14 ttm to a dry thickness of 4 μm.

Thereafter, the magnetic layer was surface-treated using a super calender roll to obtain a wide magnetic film having a magnetic layer of a predetermined thickness. This film was cut into 1/2 inch width to prepare sample 1 of a video magnetic tape.

Example-2 In the magnetic paint formulation of Example-1, vylon 530
Sample 2 was obtained in exactly the same manner except that Vylon 280 was used.

Comparative Example Sample 3 (comparison) was obtained in exactly the same manner as in FllJ1 except that the silicon-modified urethane was replaced with polyurethane Niboran 2304 (manufactured by Nippon Polyurethane).Comparative samples 2 and 3 were found to be compatible with each other. , gloss, smoothness, squareness ratio, lumi S/N, and chroma S/N were measured, and the results are listed in Table 1.

Table 1 (17,L, the characteristics of these i were expressed according to the following criteria.

(1) Each binder was added to a compatible solvent, stirred and left to stand, and the state of the liquid was observed, and those with a homogeneous phase were marked as ○.

(2) Gloss meter (Mura) GL-26 manufactured by Nishiki Institute
, D). The glossiness of the 60-degree reflection on the standard sample (black tile) surface was defined as 100%, and that on the sample tape surface was expressed as a relative value (base). The higher this value is, the better the glossiness is, indicating that the magnetic powder particles are more uniformly dispersed.

(3) Flat? The smoothness of the surface was measured using a stylus type surface roughness meter and a microscopic probe, and a very smooth surface was rated O.

(4) Measure the square ratio residual magnetic ratio 13r and the saturation magnetic ratio 13m, Br/B
It is expressed as +n.

(5) Lumi and Chroma S/N The value of the comparative example tape was used as the standard (0), and the values were expressed as relative values (dB) to that value.

As is clear from Table 1, the Nokuingu system of the present invention has better compatibility between binders and improved dispersibility than conventional binder systems, resulting in better surface properties and electromagnetic conversion performance. A good magnetic tape was obtained.

Agent Patent Attorney No 1) Suna Chika

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer containing ferromagnetic powder and a binder resin is coated on a support, the binder resin is a polyester resin having 1803M groups (M is hydrogen or ←fluoroalkali metal atom) in the side chain. A magnetic recording medium comprising: a urethane resin having a polypropylene bond in its molecule;