JPS63253527A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance running durability even at and under a high temp. and high humidity and to enhance an electromagnetic conversion characteristic, skew characteristic and S/N by incorporating a vinyl chloride resin having a negative group and specific urethane resin into a magnetic layer. CONSTITUTION:The vinyl chloride resin having the negative group and the urethane resin having rupture strength ranging 550-800kg/cm<2> and >=100kg/cm<2> stress at 100% elongation are incorporated into the magnetic layer. Dispersion of the magnetic powder is improved and the surface smoothness of the magnetic layer is improved by incorporating the vinyl chloride resin having such negative group into the magnetic layer; in addition, the mechanical properties are improved and the staining of calender rolls, etc. is suppressed. High-density packing of the magnetic powder is permitted and the electromagnetic conversion characteristic of a high level is obtd. Edge breaking deformation, increased powder dislodging, etc., of a tape are prevented and the good running stability and running durability are maintained even under the high temp. and high humidity conditions by incorporating the above-mentioned urethane resin simultaneously into the magnetic layer.

Description

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

BACKGROUND OF THE INVENTION In recent years, magnetic recording media have been increasingly developed for other applications and products, and are now required to have electromagnetic conversion characteristics, physical properties, and other performance characteristics that are far superior to those of the past.

For this reason, various studies and improvements have been made regarding binders in magnetic materials.

Conventionally, cellulose derivatives, vinyl chloride-vinyl acetate copolymers, polyurethane resins, acrylic resins and their copolymers, vinylidene chloride and their copolymers, epoxy resins, phenoxy resins, and polyesters have been used as binders for magnetic recording media. etc. are used alone or in combination of several types of components.

Among these, a typical example is a combination of polyurethane resin and vinyl chloride/vinyl acetate copolymer.

Conventionally known urethane resins used in such magnetic layers and the like 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, resulting in poor mechanical strength of magnetic recording media against sliding contact with guide pins, magnetic heads, etc. Moreover, there are problems in terms of runnability and powder shedding. For example, when a polyester type urethane resin, polyvinylidene chloride, or vinyl chloride-vinyl acetate copolymer is used, there are problems particularly in heat resistance and still image stability. In addition, since such urethane resins tend to have adhesive properties, they tend to cause unstable running called stick-slip in the case of video tapes, for example, and as shown in Figure 8, the average surface roughness of the magnetic layer increases. Ra-ma g) is especially 0
．． If it is less than 0.014 μm, jitter will increase and running instability will become significant. Therefore, the surface of the magnetic layer is sometimes roughened to improve running stability, but this is inconvenient because it actually causes a decrease in output.

In recent years, as the density and S/N of magnetic materials, especially video and computer recording media, have increased, the particles of magnetic powder used have become smaller, and for example, VH3 or beta type magnetism has become smaller when expressed in terms of surface area per unit weight. The standard grade of tape uses magnetic powder with a BET surface strength of 19~28rrr1g class, and the super high grade class uses 30~
b Magnetic powder is used. In addition, it is said that S/S is proportional to the square root of the number of magnetic particles in the recording material related to professional grade recording, so when applying the same weight of magnetic powder, the smaller the particle size of the magnetic material is used, the more the S/ This is advantageous for improving N. However, since the surface area of particles increases in inverse proportion to the square of the particle diameter, dispersion of particles becomes rapidly difficult as the particle diameter decreases, and dispersion stability also deteriorates. The finer the particles and the higher the magnetic force of magnetic powder, the stronger the cohesive force of individual particles becomes.As a result, the dispersibility and surface smoothness necessary to obtain high playback output and good S/N ratio for short wavelength recording become stronger. Sexuality becomes unsatisfactory. In addition, since such recording media come into intense sliding contact with the magnetic head during recording and reproduction, repeated use causes the magnetic coating to wear out and the magnetic powder contained in the coating to easily fall off, resulting in undesirable effects such as clogging of the magnetic head. bring forth.

Normally, when dispersing magnetic powder, it should be sufficient to use a dispersant sufficient to coat the surface of the magnetic powder particles, but in reality, sufficient dispersibility and stability cannot be obtained with this. Significant excess of dispersant is added. The dispersant that is not adsorbed to the magnetic powder mixes with the binder resin as a binder in the coating film and plasticizes the magnetic layer, and also prevents the hardening of the binder resin, thus reducing the mechanical strength of the magnetic layer, especially Young's modulus. significantly decreases Recently, with the trend toward longer recording times on tape, thin base films have been used,
There is a tendency to reduce the total thickness of the tape, but since the stiffness of the tape is proportional to the cube of the tape thickness, the stiffness becomes significantly weaker as the tape becomes thinner. This leads to poor touch and therefore deterioration of the S/N ratio.

In order to maintain the mechanical properties associated with thinning, especially the stiffness of the tape, a super-stretched base film is used and the Young's modulus of the magnetic layer is increased. For this reason, a reduction in the Young's modulus of the magnetic layer due to excessive dispersants and other low-molecular additives significantly deteriorates the mechanical properties of the thin tape.

For this reason, it is possible to improve the dispersibility of the magnetic powder in the binder by adjusting the viscosity distribution of the magnetic powder, use a surfactant as a dispersant, or use hydrophilic groups in the binder, such as hydroxyl groups, to improve the dispersibility of the magnetic powder in the binder. Methods have been proposed in which the properties are modified by introducing a phospho group, a sulfo group, a carboxy group, or the like.

For example, by introducing a sulfonic acid metal salt residue into a polyester resin,
JP-A-74827, etc. disclose improvements in surface smoothness (gloss) and adhesion to supports; JP-A-56-13519; JP-A-56-74826;
No. 74829, etc. discloses improvements in filling properties related to dispersibility and interfacial tension, and binder compositions based on a combination of the gold sulfonate redundant base-introduced polyester resin, polyurethane resin, nitrocellulose, vinyl chloride-vinyl acetate resin, etc. Many proposals have been made.

Furthermore, since vinyl chloride resin has high mechanical strength, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, or vinyl chloride-vinyl acetate-vinyl alcohol- Maleic anhydride copolymers and the like are preferred.

Modification of the vinyl chloride resin with a sulfonic acid metal salt residue is disclosed in JP-A No. 57-44227. First, a vinyl chloride resin containing an OH group and, for example, a chlorine atom and a sulfone in one molecule are disclosed. A dehydrochlorination reaction is carried out with a compound containing acid metal salt residues to obtain a modified vinyl chloride resin into which sulfonic acid metal salt residues have been introduced.

Regarding vinyl chloride copolymers containing free sulfo groups (-3O3H), JP-A-58-10803
There is a place to disclose in issue 2.

However, studies on making the magnetic powder finer, increasing its magnetic force, and improving its dispersibility, filling properties, surface smoothness, etc.
Along with the improvements, other problems have arisen. In other words, increasing the density and increasing the SZN of the magnetic powder in the magnetic layer, on the other hand, leads to a decrease in the mechanical strength of the coating film, and many problems remain regarding the running stability and running durability when formed into a tape. has been done.

For example, if the tape is run repeatedly under normal conditions, the edges of the tape may break, the tape may become seaweed-like, or powder may fall off. Such deterioration and defects in running durability are particularly noticeable under conditions of high temperature and high humidity, and are accompanied by deterioration of skew characteristics, jitter, output, S/N, etc.

The object of the present invention is to have excellent running durability even under high temperature and high humidity conditions, to maintain good electromagnetic conversion characteristics, and to improve the mechanical strength of the magnetic coating film. In addition, the adhesion between the magnetic coating film and the support is good, and the dispersibility of the magnetic powder in the magnetic layer is good, allowing for high-density packing.It also has excellent running stability and has low skew characteristics and jitter. The object of the present invention is to provide a magnetic recording medium with excellent output characteristics, S/N ratio, etc.

The present invention relates to a magnetic recording medium in which a magnetic layer contains a urethane resin having a stress of 100 kg/cn1 or more at 100% elongation.

In the present invention, it is significant that the magnetic layer contains the above-mentioned urethane resin. That is, the first
Compared to the characteristics of conventional soft urethane resins, as exemplified by curve a in the figure, we use urethane resin that has a lower elongation against stress, so the urethane resin is given appropriate hardness, and the elongation against stress is higher than that of the conventional soft urethane resin. Since the range is limited, the binder resin can have appropriate flexibility and binding strength. As a result, the mechanical strength of the magnetic WI (magnetic coating film) and magnetic recording medium is increased, greatly improving running durability, and damage such as wear and powder falling when the magnetic head slides is greatly reduced. , the running performance is significantly improved. In particular, with magnetic tapes for VTRs, it is possible to prevent edge bending and tape deformation, significantly increasing running stability and running durability, and it is also possible to maintain control tracks near the edges and perform their functions well. can. This improves skew characteristics, jitter, output characteristics, and S/N ratio.

Further, since the urethane resin of the present invention has appropriate flexibility due to the above-mentioned limitations, the adhesion between the magnetic coating film and the support (or base layer) is good. Furthermore, the presence of the urethane resin of the present invention reduces stickiness and stiffness, which are disadvantages when using only soft urethane resins.
s) can be prevented from decreasing, tackiness can be suppressed, and the stiffness of the medium can be strengthened, and calendering of the magnetic layer can also be easily performed.

In addition, the urethane resin of the present invention has higher heat resistance than conventional ones, so it maintains good running durability, running stability, and electromagnetic conversion characteristics even when used under high temperature and high humidity conditions, and can withstand harsh usage conditions. A durable and highly practical magnetic recording medium can be provided.

In particular, when playing stills from a videotape, the tape must be stopped and the video head be placed on the same surface of the videotape 60 times.
It is necessary to make sliding contact at a rate of seconds and to maintain this state for more than two hours. Significant reduction in output or increased dropout is not allowed during this still time. It is known that during still recording, the temperature of the tape surface reaches 80 to 100° C. due to continuous rubbing by the video head. That is, according to the present invention, it is possible to effectively cope with such severe usage conditions as described above.

That is, in the present invention, it is important that the mechanical properties of the urethane resin are limited to the above ranges, thereby making it possible to sufficiently achieve each of the above effects.

In addition, in the present invention, since the magnetic layer contains a vinyl chloride resin having a negative group, the mechanical strength of the magnetic layer is high, the dispersibility of magnetic powder is improved, and the surface of the magnetic layer is smooth. This results in better properties and less staining of calender rolls, etc. This enables high-density packing of magnetic powder and provides high-level electromagnetic conversion characteristics. Moreover, even with such high-density packing of magnetic powder, since the magnetic layer contains the urethane resin described above, the edges of the tape may break as described in the prior art section.
It is possible to prevent deformation, increase in powder falling, etc., and maintain good running stability and running durability even under high temperature and high humidity conditions.

The physical properties of the polyurethane resin include a breaking strength of 580
It is more preferable that the stress at 100% elongation is 150 kg/aa or more and 700 kg/c4 or less.
It is more preferable to set it to 300 kg/crA or more and 300 kg/crA or less.

Among the above-mentioned urethane resins, those having a yield point YP as illustrated in the curve shown in FIG. 1 are particularly preferred. Such urethane resin has very low elongation when stress is applied until it reaches its yield point YP, so it is particularly suitable for imparting appropriate hardness to the magnetic layer, and it is
Thereafter, it exhibits the property of elongating as stress increases without causing breakage, and therefore has appropriate flexibility and binding strength as a binder resin. The above yield point YP is also important for the performance of the urethane resin, and is preferably 50
~600 kg/c, more preferably 100-560
kg/ci stress range (approximately 290 kg/ci in the example in Figure 1)
It is desirable that there is a yield point in kg/cj).

If the stress range in which the yield point exists is 50 kg/- or more, the resin will be prevented from becoming too soft, and the stress will be 600 kg/- or more.
If it is less than cd, the resin can be prevented from becoming hard and brittle. Further, the urethane resin having this yield point has good dispersibility and improves the durability of the magnetic layer.

In order to exhibit the above-mentioned excellent performance, the above-mentioned urethane resin having a yield point preferably has a cyclic hydrocarbon residue in the molecule. Preferably, the cyclic hydrocarbon residue is a saturated cyclic hydrocarbon residue, including divalent or 1 fil
Examples include li consisting of a cyclopentyl group, a cyclohexyl group, etc., or derivatives thereof (for example, an alkyl group substituted product such as a methyl group, a halogen substituted product such as a chlorine atom). These saturated cyclic hydrocarbon residues are desirable from the viewpoint of imparting appropriate hardness to the urethane resin and availability of raw materials. 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. In addition, by changing the amount of the constituent components having cyclic hydrocarbon residues in the urethane resin, it is possible to obtain a urethane resin having an arbitrary glass transition point (Tg), and the Tg is between -30°C and 100°C.
°C, preferably 0 °C to 90 °C. If Tg is -30℃ or more, the resin becomes soft (T g <-30℃
), and by setting the temperature to 100° C. or lower, the film can be prevented from becoming unduly hard and brittle.

Furthermore, the average surface roughness (Ra-mag) of a magnetic layer using a urethane resin having the above yield point as a binder resin,
For example, it was confirmed that there is a strong correlation with chroma S/N as shown in Figure 2 (however, the data in Figure 2 is
(expressed as a relative value when the chroma S/N of a medium with Ra-mag of 0.020 μm is expressed as OdB). According to this,
By setting Ra-mag to 0.020 μm or less,
It can be seen that the chroma S/N increases and changes in inverse proportion to the value of Ra-mag. Therefore, R
The a-mag is preferably 0.020 pm or less,
It is more preferable to set it to 0.016 μm or less, especially 0.0
If it is 14 μm or less, it is extremely suitable for high-fidelity, high-grade, high-resolution, master tape, etc. applications that require high quality. Note that if Ra-mag is too small, running characteristics tend to become unstable, such as image shaking, so the lower limit is preferably 0.005 μm.

Note that similar results were obtained when the urethane resin according to the present invention having no yield point was used.

In order to achieve Ra-mag in the above range, the amount of dispersant used when forming the magnetic layer is preferably 0.5 to 6% by weight. If the amount of dispersant is too small outside this range, the surface roughness of the magnetic layer will be reduced due to poor dispersion, as described above.
It is difficult to set the a-ma g to a small value within a predetermined range of 50.020 μm, and if too much dispersant is used, the dispersant tends to bleed out from the magnetic layer.

In this case, in the present invention, it is used as a binder.

Since a vinyl chloride resin with a negative group is used, 1
, the dispersibility of the magnetic powder and the surface smoothness of the magnetic layer are good, which is advantageous for realizing the above-mentioned Ra-mag. Also,
Since the binder itself has a dispersing effect, the amount of dispersant can be reduced, preventing the dispersant from bleeding out and plasticizing the magnetic layer, and improving the mechanical strength of the magnetic coating. It is advantageous on

In addition, the urethane resin used in the present invention (not limited to those having a yield point) has lower adhesiveness than conventional urethane resins, so running is stable in the case of video tape, for example, and the jitter value is lower than that of conventional urethane resins. can be kept smaller than that of For this reason, for example, the Ra-mag of the magnetic layer
0. (Even if the thickness is 4 μm or less, there is an advantage that running performance does not become unstable and high output can be maintained.

Note that the above-mentioned "average surface roughness" is measured as follows. That is, using the measured value at the center line roughness with a cutoff value of 0.25 mm of the roughness curve shown in Section 5 of JIS-BO601, the measuring device was a three-dimensional roughness measuring instrument 5E manufactured by Koita Research Institute. -3FK was used.

In the present invention, the urethane resin contained in the magnetic layer can be synthesized by reacting a polyol and 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, propylene dalicol, butylene glycol, and diethylene glycol, or trimethylpropane, hexanetriol, glycerin, trimethylolpropane, and hexanetriol. , polyester polyols synthesized by reaction with polyhydric alcohols such as glycerin, trimethylolethane, and pentaerythritol, or any two or more polyols selected from these glycols and polyhydric alcohols; or, Lactone polyester polyols synthesized from lactams such as S-caprolactam, α-methyl-1-caprolactam, S-methyl-8-caprolactam, and γ-butyrolactam; or ethylene oxide, propylene oxide,
Examples include polyether polyols synthesized from butylene oxide and the like.

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,
and also in the form of polyurethanes or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups or without these reactive end groups (
For example, it may be 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.

The hardness of the above-mentioned urethane resin can be controlled by variously changing its components and/or manufacturing method, and therefore the urethane resin according to the present invention can be manufactured.

That is, in order to lower the hardness of urethane resin, multiple types of polyester polyol components may be randomly present in the molecule, or an isocyanate whose molecular chain between isocyanate groups is composed of chain-like aliphatic hydrocarbon groups may be used. There are several methods to increase the hardness of urethane resin, such as using the same type of polyol, increasing the amount of isocyanate added, using isocyanate that easily crystallizes, or using isocyanate that has a benzene ring in the molecule. There are methods such as using .

Moreover, the above-mentioned urethane resin having a yield point can be synthesized by reacting a polyol and a polyisocyanate.

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

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

(2) A method of using a dicarboxylic acid having a cyclic hydrocarbon residue in advance as the organic dibasic acid (dicarboxylic acid) which is 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 having 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 (HOOC(C
H2) A polyester polyol obtained from 4-C00H) is diluted with methylene bis. 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 polyhydric alcohol having a cyclic hydrocarbon residue in advance, those having a cyclohexyl group in the molecular chain of the ethylene glycol structure can be used, as described above. Alcohols or glycols thereof, or those having a cyclic hydrocarbon residue in their structure can be used. Examples of dibasic acids include phthalic acid, trimerized lyluic acid, maleic acid, and those having a cyclic hydrocarbon residue in their molecules. Instead of the above polyols, lactone-based polyester polyols synthesized from lactams such as S-caprolactam, α-methyl-1-caprolactam, S-methyl-3-caprolactam, and γ-butyrolactam; or ethylene oxide, butylene oxide, etc. Polyether polyols synthesized from the above may also be used.

These polyols are used as raw materials for urethane resins like the conventional polyols mentioned above, and can also be used in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups, or in the form of urethane prepolymers containing these reactive end groups. It may also be in the form of a urethane elastomer (for example, in the form of a urethane elastomer).

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

It should be noted that in the magnetic layer, the above-mentioned urethane resin having a yield point and a resin having no yield point may be used in combination, and resins having mutually different physical properties may be used together. In addition, a soft urethane resin or a hard urethane resin may be used as appropriate in addition to the urethane resin according to the present invention.

The vinyl chloride resin according to the present invention can be obtained by copolymerizing a copolymerizable monomer having a vinyl chloride heptamine 1 anionic group and, if necessary, other copolymerizable monomers. Since this copolymer is based on vinyl synthesis, it is easy to synthesize, and various copolymer components can be selected, so that the properties of the copolymer can be optimally adjusted.

Examples of the negative group include one or more selected from strong acid residues containing sulfur, acid residues containing phosphorus, carboxyl groups, hydroxyl groups, salts thereof, and the like.

Among the above-mentioned strong acid residues containing sulfur, sulfonic acid residues are easily available and there are many types. Furthermore, examples of acid residues containing phosphorus include phosphoric acid residues. Examples of these salts include alkali metal salts (sodium, potassium, and lithium are particularly preferred) and ammonium salts. Among the above alkali metal salts, potassium salts are particularly preferred in terms of solubility, reactivity, yield, and the like.

The above-mentioned copolymerizable polymer having a sulfonate or the like as a negative group includes CH2=CH3O3M.

CH2=CHCH2So 3M.

CH2=C(CH3)CH2SO3M.

CHz=CHCHzOCOCH(CH2COOR)SO
3M.

CHz=CHCH1OCHzCH(OH)CH2SO3
M.

CHz=C(CH3)C00CzH+SOaM.

CHz = CHCOOC4Hs S O3M.

CHz”CHCONHC(CH3)2CH2SO3M.

can be mentioned.

In addition, as copolymerizable materials containing phosphates, etc., CHZCHZCHZOCHzCH(OH)CHz-O-
PO3MYi, CH2=CHC0NHC(CH3)2CH2-0-PO
2MX i, CHz=CHCHzO(CHzCHzO)mPOzMX
"In the above, M is H, an ammonium group or an alkali metal, R is an alkyl group having 1 to 20 carbon atoms, and Yl is M
Or CHz=CHCHzOCHzCH(OH)CH2-1Y
2baM or CH2=CHC0NHC, (CH3) 2CH2-5
X1 is or 0M5X2 is CH2"CHCH20(CH2CH20)m- or OM
It is. Further, n is a positive number of 1 to 100, and m is a positive number of 1 to 100.

Those having a carboxyl group or a salt thereof are particularly preferred from the viewpoint of improving durability, and as the salt, an alkali metal salt or an ammonium salt is particularly preferred. In this case, those having a salt of a carboxyl group are more preferable from the viewpoint of dispersibility of the magnetic powder.

Each copolymer containing a copolymerizable monomer having each of these groups (hereinafter referred to as monomer unit A) is used in the magnetic layer to form each magnetic recording medium, and the squareness ratio (Bm /Br), the squareness ratio tends to be improved by using a copolymer in which the carboxyl group is a salt.

This is because when -COOH is made into a salt, when it is dispersed in a solvent, it does not dissolve in the solvent, and therefore the copolymer adsorbed to the magnetic powder is difficult to desorb and the copolymer itself becomes more hydrophilic. it is conceivable that.

The copolymer used in the present invention can be produced by copolymerizing the above-mentioned starting materials. For example, a copolymer of maleic anhydride and vinyl chloride is synthesized, and this copolymer is hydrolyzed to open the ring of the maleic anhydride moiety, and the resulting carboxyl group is treated with ammonia, as described above. (All the carboxyl groups in the seven-mer unit A are converted into ammonium salts. However, in this case, some maleic anhydride moieties that are not ring-opened during the above hydrolysis may remain, and in this case, the maleic anhydride moiety is The maleic anhydride moiety may be ring-opened and a part of the carboxyl group of the heptanomer unit I-A is amidated, and other carboxyl groups may be converted into ammonium salts, so to speak, a half-amide state, or the maleic anhydride moiety may be formed by the action of ammonia. may be left as is without ring-opening.The degree of ring-opening of the maleic anhydride moiety (therefore, the degree of ammonium saltation of the carboxyl group in heptamer unit A) may be controlled by the degree of hydrolysis described above. In addition, the solubility of the copolymer in water can be controlled by the ratio of the half-amidation or maleic anhydride moiety described above.The obtained copolymer is analyzed by, for example, QC/Mass,
Identified.

As the negative group contained in the vinyl chloride resin of the present invention,
It is believed that the use of a salt such as a metal salt is more advantageous in obtaining a magnetic layer having the retention stability and coating properties of the magnetic coating material and the excellent properties targeted by the present invention. That is, when a urethane resin is contained in a magnetic layer, a polyfunctional isocyanate curing agent is added to the magnetic layer to carry out a crosslinking (curing) reaction.

Copolymerizable heptamers to be copolymerized as necessary include known polymerizable heptamers, such as various vinyl esters, vinylidene chloride, hnylidene fluoride, acrylonitrile, methacrylonitrile, styrene, acrylic acid,
Methacrylic acid, various acrylic esters, methacrylic esters, itaconic esters, ethylene, propylene, isobutyne, butadiene, isoprene, various vinyl ethers, aryl ethers, aryl esters, acrylamide, methacrylamide, maleic acid, maleic esters, styrene. , α-methylstyrene, p-methylstyrene, and the like.

These copolymers are used not only to improve the solubility of the resin while controlling the compatibility and softening point of the resin of the present invention and other resins when mixed, but also to improve the properties of the coating film and the coating properties. Appropriate selection is made depending on the need for process improvement, etc.

The binder according to the present invention is polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, or bulk polymerization.

In either method, known techniques such as divisional addition or continuous addition of molecular weight regulators, polymerization initiators, and monomers can be applied as necessary.

Examples of polymerization initiators used in the production of resins include lauroyl peroxide, benzoyl peroxide,
3,5.5-trimethylhexanoyl peroxide,
Organic peroxides such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, t-butyl-peroxypivalate, t-butylperoxyneodecanoate; Azo compounds such as 2,2-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleric acid; ammonium persulfate, potassium persulfate, persulfate; Examples include inorganic peroxides such as ammonium phosphate.

Suspension stabilizers include, for example, polyvinyl alcohol,
Partially saponified polyvinyl acetate, cellulose derivatives such as methylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyvinyl and LoliP,
Polyacrylamide, maleic acid-styrene copolymer,
Examples include synthetic polymeric substances such as maleic acid-methyl vinyl ether copolymer and maleic acid-vinyl acetate copolymer, and natural polymeric substances such as starch and gelatin. Examples of the emulsifier include anionic emulsifiers such as sodium alkylbenzenesulfonate and sodium lauryl sulfate, and nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene sorbitan fatty acid partial ester. Further, a molecular weight regulator such as trichlorethylene or thioglycol can also be used if necessary. The polymerization initiator, vinyl chloride and other monomers, suspending agents, emulsifiers, molecular weight regulators, etc. mentioned above may be added to the polymerization system all at once at the start of polymerization, or they may be added in portions during polymerization. You can also.

The amount of the anionic group-containing monomer in the binder used in the present invention is preferably 0.01 to 30 mol%. If the amount of the negative group-containing monomer is too large, the solubility in solvents will be poor (and gelation will likely occur).

In addition, if the amount of negative group-containing polymer is too small, desired properties cannot be obtained.

Here, by selecting the amount of negative group containing and the type of negative group, both the hydrophilic and hydrophobic properties of the copolymer, that is, HL B (Hydrophile Lipoph
ile balance) can be appropriately controlled.

The average degree of polymerization of the vinyl chloride copolymer is 100 to 60.
It is particularly preferable to set it to 0; within this range, the magnetic layer etc. will not become easily sticky and the dispersibility will be maintained well. This vinyl chloride copolymer may be partially hydrolyzed.

Blending ratio of the vinyl chloride copolymer and urethane resin according to the present invention (total of both is 100 parts by weight).

As for the vinyl chloride copolymer according to the present invention,
It is desirable that the amount is 10 parts by weight, more preferably 80 to 20 parts by weight. If the above-mentioned blending ratio exceeds 90 parts by weight, the coating film becomes too brittle and the durability of the coating film is significantly deteriorated, and the adhesion to the support also deteriorates. Further, if the above-mentioned blending ratio is less than 10 parts by weight, the magnetic powder tends to fall off.

In addition, as a binder resin, in addition to the above-mentioned urethane resin and vinyl chloride copolymer having a negative group, a vinyl chloride copolymer (regular one) and/or phenoxy resin may also be used as a binder resin with strong mechanical strength. can.

The phenoxy resin that can be used is a polymer obtained by polymerizing bisphenol 8 and epichlorohydrin, and is represented by the following general formula.

) PKHH, P'KHT, etc.

Furthermore, for a vinyl chloride copolymer that does not have a usable negative group, the molar ratio derived from p and m is 95 to 50 mol% for the former unit, and 5 to 50 mol% for the latter unit. It is 50 mol%. In addition, X represents a monomer residue that can be copolymerized with vinyl chloride, and various known copolymerizable hexamers (various vinyl esters, etc.) mentioned in the explanation of the vinyl chloride-based copolymer having a negative group can be used. Represents one or more selected types. The degree of polymerization expressed as (J+m) is preferably 100 to 600, and the degree of polymerization is 100
If it is less than 600, 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 copolymer containing vinyl chloride-vinyl acetate (hereinafter referred to as "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. As a specific example of the above-mentioned vinyl chloride-vinyl acetate copolymer, (7)r manufactured by Union Carbide Co., Ltd.
VAGHJ, rVYHHJ, rVMCHJ, Water Chemistry (
+Kiku's "S-LEC AJ rS-LEC A-5J,
rSlesoku C”, “SlesokuM”, Denki Kagaku Kogyo@
[Denkabinir 100OGJ, [Denkabinir 10]
0OWJ 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 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 200,000, and a polymerization degree of about 200 to 2,000, such as vinyl chloride.
Vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer , methacrylic acid ester-acrylonitrile copolymer, methacrylic acid ester kidney-oxidized vinylidene copolymer, methacrylic acid ester-styrene copolymer, polyhinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide Resin, polyvinyl butyral, cellulose ta conductor (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, etc.), styrene butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubbers Thermoplastic resins and mixtures thereof are used.

Furthermore, the thermosetting resin or reactive resin has a molecular weight of about 200,000 or less in the state of a coating solution, and the molecular weight becomes infinitely large due to reactions such as condensation and addition. Furthermore,
Among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate copolymer and diisocyanate prepolymer. Examples include mixtures, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates, polyamine resins, and mixtures thereof.

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

The above resins are -3O3M-1-O303M, -COO
It may also be a resin containing a hydrophilic polar group such as M, -PO(OM)z (where M is hydrogen, an ammonium group, or an alkali metal, and M is hydrogen, an ammonium group, an alkali metal, or a hydrocarbon residue). .

Furthermore, durability can be improved by further adding a polyisocyanate curing agent to the magnetic paint. Examples of such polyisocyanate-based curing agents include bifunctional incyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexane diisocyanate;
Trifunctional isocyanates such as 1L), desmodulite (manufactured by Bayer AG), or urethane prepolymers containing isocyanate crystals at both ends, which have been conventionally used as curing agents, can also be used as curing agents. Any polyisocyanate can be used. The polyisocyanate curing agent is used in an amount of 5 to 80 parts by weight based on the total amount of binder.

In addition, usable curing accelerators include acetylacetone complex salt, dibutyltin dilaurate, oleic acid, DAB
Examples include CO (1,4-diazabicyclo-2,2,2-octane), amines (for example, tri(dimedylamino)phenylmethane), iron chloride, and piperazine compounds.

When using a curing accelerator, the amount added is 0.5 of the curing agent.
A content of up to 25% by weight is preferable, but if it is less than 0.5% by weight, the promoting effect is poor, and if it exceeds 25% by weight, bleed-out to the layer surface tends to occur. Also, 1.0 for Pai Ndar
It is preferable to set it to -10ffif%.

FIG. 3 shows an example of a magnetic recording medium, such as a magnetic tape, according to the present invention, in which a magnetic N2 is provided on a support 1, and an 80 layer 3 is provided on the opposite surface. The structure shown in FIG. 4 is the same as the structure shown in FIG. 3, but a subbing layer 4 is provided between the support 1 and the magnetic layer 2.

FIG. 5 shows another magnetic recording medium.
OC stone (overcoat layer) 5 on the magnetic layer 2 of the medium shown in the figure.
is provided. The urethane resin according to the present invention can be used as this OCC50 binder resin. This 00 layer 5 is provided to protect the magnetic layer 2 from damage, etc., and for this purpose, it needs to have sufficient slipperiness.

The surface roughness of the 00 layer 5 is Ra, especially in relation to the color S/N.
≦0.01 μm, Rmax≦0.13. It is better to use crm.

In this case, the surface roughness of the support 1 is Ra≦0.01 μm,
It is desirable that Rmax≦0.13 μm and that a smooth support 1 be used.

FIG. 6 shows a magnetic recording medium configured as a magnetic disk, in which the same magnetic M2 and oc
R5 is provided respectively.

The media shown in FIGS. 5 and 6 may also be provided with a lower rim 4 as shown in FIG. 4.

In the magnetic layer of a magnetic recording medium, the specific surface area is BP and T value is 3.
5 rrr/gr or more (more preferably 38 m/g
If magnetic powder with a particle size of r or higher is used, high-density magnetic recording can be achieved.
A high S/N ratio is possible, and electromagnetic conversion characteristics at a high level can be obtained. Moreover, since the magnetic recording medium of the present invention uses the above-mentioned urethane resin and vinyl chloride resin having a negative group, it maintains a high level of electromagnetic conversion characteristics and has remarkable improvements in running durability. I can play the Chokaka. This point has been discussed above.

If the specific surface area of the magnetic powder is increased more than necessary, poor dispersion will occur, so it is desirable that the upper limit is 100 of/gr. In addition, in the above, "rBET value" means
It refers to the surface area per unit weight, and is a physical quantity different from the average particle size. For example, even if the average particle size is the same,
There are those with a large specific surface area and those with a small specific surface area. To measure the specific surface area, for example, first, magnetic powder is
After heating at around 0'C for 30 to 60 minutes, the powder is degassed to remove substances adsorbed to the powder, and then introduced into a measuring device to adjust the initial pressure of nitrogen to 0.5 kg/n. ? and perform adsorption measurements using nitrogen at liquid nitrogen temperature (-195°C) (Specific surface area measurement method generally referred to as B, E, T method. For details, see J, Ame, Chem, Soc.
, 60309 (193B)). As a device for measuring the specific surface area (BET value), it is possible to use a "powder measuring device (Cantersoap)" jointly manufactured by Yusenbattery and Yuasa Ionics ■. A general explanation of the specific surface area and its measurement method can be found in “Powder Measurement J (J, M, DALLAVALLE, CLYDEO
Co-authored by RR Jr., translated by Benguchi and others; published by Sangyo Toshosha).
0-1171, edited by the Chemical Society of Japan, published by Maruzen, April 30, 1966). (However, it is the same as the specific surface area in this specification.)

The magnetic powder used in the magnetic layer, especially the ferromagnetic powder, is r
-FezO3, CO-containing r-Fe203, Fe3O4,
Iron oxide magnetic powder such as Go-containing Fe3O4: F13. Ni,
00% Fe-N1-Co alloy, Fe-N1-AA! alloy, Fe-A11-Co alloy, Fe-Al-Go-N,
i alloy, Fe-A1-N1-P alloy, Fe-Ni-Cr
Examples include various ferromagnetic powders such as alloys, Co--Ni alloys, metal magnetic powders mainly composed of Fe, Ni, Go, etc.: CrO2.

In the magnetic recording medium of the present invention, additives such as non-magnetic particles, a dispersant, a lubricant, an antistatic agent, etc. may be contained in the magnetic layer or the 80 layer as necessary.

In the present invention, non-magnetic particles that can be used in the magnetic layer or BCN include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, aluminum hydroxide, chromium oxide, silicon carbide, and carbide. Calcium, α-Fe2Q3, calcium sulfate,
Boron nitride, zinc fluoride, molybdenum dioxide, molybdenum disulfide, barite powder, precipitated barium sulfate, precipitated carbonate coal, chalk powder, talc, kaolin, coal stone powder, lithopone, lead white, carbon black, graphite, yellow lead, zinc yellow , cadmium yellow, melamine resin, guanamine resin and the like can be used, but the resin is not limited to these.

The carbon black that can be used for the magnetic layer or BCJ'i is preferably conductive, such as Conductex 975 manufactured by Columbia Carbon.
(specific surface area 250 J/g, particle size 24 mμ), Conductex 900 (specific surface area 125 n?/g, particle size 2
7 mμ), Cabot Vu
lcan)
There are #44 etc. made by the manufacturer. Light-shielding carbon black may also be used, such as Laben 20 manufactured by Columbia Carbon.
00 (Specific surface H1190ITr/g, particle size 18mμ)
, 2100.1170.1000, Mitsubishi Kasei side type #
100, #75, #40, #35, #30, etc. can be used. It is preferable that the carbon blank has a particle size of 20 to 30 mμ, preferably 21 to 29 mμ, but if its oil absorption is 90 m6 (DBP)/100 g or more, it will easily form a stracture structure and have higher conductivity. It is desirable in that it shows

Non-magnetic particles (abrasives) that can be used in the magnetic layer include:
Alumina (preferably α-A 1z O3), silicon carbide, chromium oxide, silicon nitride, titanium oxide, α-iron oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite) Thermal materials may be other than these, and may be inorganic or organic, and may be alloys. The content of this non-magnetic particle is 10
It is preferably 20 parts by weight or less relative to 0 parts by weight,
Furthermore, 2 parts by weight to 10 parts by weight are particularly preferable.

The above non-magnetic particles preferably have a Mohs hardness of 5 or more, more preferably 6 or more.

In addition, the average particle size of these nonmagnetic particles is 0.6 μm or less (
Furthermore, if the thickness is in the range of 0.1 to 0.3 μm, good electromagnetic conversion characteristics can be maintained.

Dispersants that can be used include fatty acids, metal salts of fatty acids made of alkali metals (Li-, Nas K, etc.) or alkaline earth metals; fatty acid amides; lecithin; trialkyl polyolefin oxy quaternary ammonium salts (alkyl The carbon number is 1 to 5, and the olefin is ethylene, propylene, etc.). In addition, higher alcohols having 12 or more carbon atoms, and in addition to these, sulfuric esters, alkyl sulfates, phosphoric esters, ÷CH2CHz
-Own phosphoric acid esters, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid esters, known surfactants and their salts, negative organic groups (e.g. -C
OOH, -PO3H, -303H.

Examples include salts of polymer dispersants having S 02 N H-1 and salts thereof). These dispersants are 1
Only the seeds may be used, or two or more types may be used in combination. When using these dispersants in the magnetic layer, magnetic powder 10
It is preferably added in an amount of 1 to 20 parts by weight per 0 parts by weight, and when used in a back coat layer, it is preferably added in an amount of 2 to 20 parts by weight per 100 parts by weight of the binder resin.

Lubricants that can be used include dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms), GOOR (R=H
or C1-C2o alkyl group), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has carbon atoms 1 to 4), phenylpolysiloxane, fluoroalkylpolysiloxane (alkyl has 1 to 5 carbon atoms)
conductive fine powder such as graphite; inorganic fine powder such as molybdenum disulfide, tungsten disulfide; fine plastic powder such as polyethylene, polypropylene, polyethylene vinyl copolymer, polytetrafluoroethylene; α-olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature (a compound in which an n-olefin double bond is bonded to the terminal carbon, carbon number 20);
Examples include fluorocarbons; higher fatty acids such as lauric acid, myristic acid, stearic acid, and behenic acid; fatty acid esters; and the like. These lubricants may be used alone or in combination of two or more. The amount of these lubricants is 0.2 to 20 parts by weight per 100 parts by weight of the binder resin.
It is best to add it in parts by weight.

As antistatic agents that can be used, conductive fine powders such as carbon black and carbon black graft polymers;
Natural surfactants such as saponins; nonionic surfactants such as alkylene oxides, glycerols, and glycidols; cationic surfactants such as higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, and phosphoniums. ; Anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfuric ester groups, and phosphoric ester groups; Ampholytic surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols etc. are used. The above conductive fine powder is added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the magnetic powder, and the surfactant is added in an amount of 0.1 to 10 parts by weight. These surfactants may be added alone or in combination. Although these are used as antistatic agents, they are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

In addition, the following may be used as additives. Phosphoric acid, sulfamide, guanidine, pyridine, amines, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, especially dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite, jetanolamine phosphate, cyclohexyl ammonium carbonate. , hexamethylene diamine carbonate, propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, morpholine stearate, etc. (inorganic or organic acid salts of amines, amides, or imides) improve the rust prevention effect. These amounts are 0.01 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder.
Used in parts by weight range.

In addition, the constituent materials of the magnetic layer are mixed with an organic solvent to make a magnetic paint, and this is coated on the support. ), alcohols (e.g. methanol, ethanol, propatool, butanol), esters (e.g. methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether), glycol ethers (e.g. ethylene glycol monoethyl ether, ethylene glycol diethyl (ether, dioxane), aromatic hydrocarbons (eg, benzene, toluene, xylene), aliphatic hydrocarbons (eg, hexane, heptane), nitropropane, and the like. The support to which this magnetic coating is applied is polyester (e.g. polyethylene terephthalate, polyethylene-2,6-naphthalate), polyolefin (e.g. polyethylene,
polypropylene), cellulose derivatives (e.g. cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate), polycarbonate, polyvinyl chloride, polyimide, polyamide, polyhydrazides, metals (e.g. aluminum, copper), paper, etc. It is good if it consists of

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.

In addition, in the following examples, all "parts" are "parts by weight".
represents.

After dispersing each component shown in Figure 7, apply 1 coat of this magnetic paint.
After filtration with a μm filter, 5 parts of a polyfunctional isocyanate was added, coated onto a support at a thickness of 5 μm, supercalendered, and one portion was slit into 2-inch widths to make each videotape shown in Figure 7. (corresponding to the numbers of Examples and Comparative Examples). However, the numerical values after the second column in FIG. 7 represent parts by weight, and "actual" after the second column represents an example, and "ratio" represents a comparative example.

Here, polyurethanes A to G and vinyl chloride copolymers A to C shown in FIG. 7 are as follows.

Polyurethane A: Yield point 350 kg/cn! , breaking strength 560 kg/cni, stress at 100% elongation 1
20 kg/c+a.

Polyurethane B: yield point 540 kg/cd, breaking strength 550 kg/cd, stress at 100% elongation 380
kg/cd.

Polyurethane C: breaking strength 660 kg/cnl,
Stress at 100% elongation: 200 kg/cffl.

Polyurethane D: Estan 5701 (manufactured by Gutdrich).

Polyurethane E: breaking strength 530 kg/cnl, 1
Stress at 00% elongation is 90 kg/c.

Polyurethane F: Breaking strength 850 kg/cfl! ,1
Stress at 00% elongation: 410 kg/cnf.

Vinyl chloride copolymer A-C was synthesized as follows.

The following composition was charged into a reaction vessel, replaced with N2, and reacted.

Methyl isobutyl ketone 86 parts by weight Methyl acetate 280 Vinyl chloride
150 Vinyl acetate
50〃CH2=CHCHzOCOCH(So
3K)-CHz COOCe N17 6
Parts by weight Diisopropyl peroxydicarbonate (polymerization initiator) 2 parts by weight The above formulation was heated to 53° C. with stirring, and 9 parts of methyl isobutyl ketone was added to 1 part of the polymerization initiator in the recipe. The remaining vinyl chloride was recovered by cooling to 30° C. for 15 hours, and was further recovered under reduced pressure. In this way, the solid content is 32% and the viscosity is 70c.
480 parts by weight of a copolymer solution of ps (25°C) was obtained. This was designated as copolymer A in FIG.

Copolymers B and C in FIG. 7 were prepared in the same manner as described above using the following copolymerizable polymers containing metal salt residues of phosphoric acid or carboxylic acid.

Monomer of copolymer B: CH2=CHCH20CHz CH(OH)CH2-O
PO3MYi (M is H, ammonium salt or alkali metal, Yl is M
or CH2=CHCH20CH2-CH(OH) CH2-) Monomer of copolymer C: Various characteristics were measured for each of the above magnetic tapes,
The results are shown in Figure 7. The method for measuring these is as follows.

Chroma S/N: Color video noise meter rshibasoku92
Measured by 5D/IJ.

Rumi S/N: Same as above.

RF output R at 4Mtlz using a VTR deck for RF output measurement
F small output was measured, and after 100 reproductions, a value that was lower than the initial output was shown.

(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.

Skew: A color par signal recorded on a magnetic tape is run on a video deck at a high temperature and humidity of 30°C and a relative humidity of 80%, and when the number of runs reaches 100, the switching point is displayed on the monitor screen. Measure the distortion of the image,
This is expressed in μS.

Jitter (μ5ec): Measured with a VTR jitter meter manufactured by Scoboretion Co., Ltd. outside Meguro Electric. The measurement conditions were 25° C. and 90% relative humidity.

However, chroma S/N, lumi S/N, and RF output are -1
~7 and ratios -1 and 2 were taken as relative values when the value of ratio -3 was taken as OdB, and for actual -8 and 9, they were taken as relative values when the value of ratio -4 was taken as OdB.

From the results shown in FIG. 7, it was found that by containing a vinyl chloride resin having a negative group in the magnetic layer and containing the urethane resin according to the present invention, running durability under high temperature and high humidity and electromagnetic conversion were improved. It can be seen that the characteristics, skew characteristics, jitter, output characteristics, and S/N ratio are all improved.

[Brief explanation of drawings]

1 to 7 show examples of the present invention. FIG. 1 is a graph showing the relationship between the stress elongation rate of urethane resin, and FIG. Graphs showing changes in S/N; Figures 3, 4, 5 and 6 are partially enlarged cross-sectional views showing each type of magnetic recording medium; Figure 7 is a graph showing the magnetic paint of each magnetic tape. It is a figure showing a component and a characteristic. FIG. 8 is a graph showing changes in jitter value depending on the average surface roughness of the magnetic layer. In addition, in the symbols shown in the drawings, 1...Nonmagnetic support 2...Magnetic layer 3...Back coat layer 4... . . . Undercoat layer-5 . . . Overcoat layer.

Claims (1)

[Claims] 1. Vinyl chloride resin with negative group and breaking strength of 5
50kg/cm^2 or more and 800kg/cm^2 or less, and the stress at 100% elongation is 100kg/cm
A magnetic recording medium in which a magnetic layer contains a urethane resin having a molecular weight of ^2 or more.