JPS6262422A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability and surface characteristic of a magnetic recording medium and to extremely improve the electromagnetic conversion characteristic thereof by using a thermoplastic polyurethane/urea resin having electron ray sensitive double bonds and siloxane bond in the molecule as a bonder for a magnetic layer. CONSTITUTION:The magnetic layer contains the thermoplastic polyurethane/urea resin having the electron ray sensitive double bonds in the molecule and the siloxane bond in the molecular chain as the binder. The totaled concn. of the urethane group and urea group of the thermoplastic polyurethane/urea resin is preferably 1.8-3.0mmol/g. The electron ray sensitive double bonds to be introduced to the thermoplastic polyurethane/urea resin are exemplified by the double bonds of acryl and methacryl and these double bonds can easily cleave to form the crosslinked constitution when irradiated with electron rays. The siloxane group concn. of the thermoplastic polyurethane/urea resin is preferably 0.03-3mmol/g.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks, and more specifically, the present invention relates to magnetic recording media such as magnetic tapes and magnetic disks, and more specifically, the present invention relates to magnetic recording media such as magnetic tapes and magnetic disks. This invention relates to improvements in binders.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, in which the binder constituting the magnetic layer has an electron beam sensitive double layer in the molecule. By using a thermoplastic polyurethane-urea resin that has a bond and a siloxane bond in its molecular chain, we aim to improve the coagulability of the solid content of the paint, increase the pot life, and simplify the manufacturing process. The aim is to improve thermal customization, blocking resistance, durability, running stability, magnetic customization, electromagnetic conversion characteristics, etc.

[Conventional technology]

Conventionally, vinyl chloride-vinyl acetate copolymers, cellulose derivatives, polyester resins, etc. are widely used as binders for magnetic recording media. Thermoplastic polyurethane resins are used to adjust physical properties.

On the other hand, there is a demand for high-density recording in magnetic recording media, and as a result, efforts are being made to make the ferromagnetic powder filled in the magnetic layer of the magnetic recording medium finer and to make the surface of the magnetic layer smoother.

However, as described above, when the surface smoothness of the magnetic layer is improved, the contact area increases, which not only adversely affects the running performance and durability of the magnetic recording medium, but also significantly deteriorates the blocking resistance. In particular, conventionally used binders have a low softening point and poor heat resistance, so if, for example, a tape-shaped magnetic recording medium is wound onto a reel and stored at high temperatures or for a long period of time, non-magnetic The problem arises that the magnetic layer sticks to the support, causing peeling of the magnetic layer and the like, making it impossible to fully demonstrate its performance as a magnetic recording medium. Furthermore, the increase in specific surface area associated with the finer particles of ferromagnetic powder significantly deteriorates the dispersibility of this ferromagnetic powder in binders, which not only impairs filling properties and surface gloss, but also affects important properties of magnetic recording media. It is difficult to obtain sufficient performance in terms of electromagnetic conversion characteristics and running durability against dust and scratches.

Therefore, in order to improve the heat resistance of the thermoplastic polyurethane resin and improve the blocking resistance of the magnetic recording medium (3) increase the proportion of low molecular weight diol, which is a component of the thermoplastic polyurethane resin, and increase the concentration of urethane groups in the molecule. It has been considered to use a thermoplastic polyurethane resin with an increased carbon content as a binder for the magnetic layer of a magnetic recording medium.

In general, increasing the urethane group concentration can modify the thermal properties of thermoplastic polyurethane resins. That is, as the concentration of urethane groups in the molecule increases, a thermoplastic polyurethane resin having a high softening point and a low glass transition point can be obtained. However, as the urethane group concentration of thermoplastic polyurethane resin increases, it becomes insoluble in general-purpose solvent systems used for manufacturing ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, and aliphatic hydrocarbon-based magnetic recording media. It has the disadvantage that it is only slightly soluble in highly toxic solvents such as dimethylformamide and tetrahydrofuran. Furthermore, when the above-mentioned solvents such as dibutylformamide and tetrahydrofuran are used as a solvent for a magnetic paint for forming a magnetic layer, the surface of the non-magnetic support coated with the magnetic paint, etc.
These solvents attack the parts of the material that come in contact with them, causing some wrinkles and
There is also a risk that unevenness may be generated or, in some cases, may be dissolved. Therefore, there are limits to the improvement that can be made by increasing the urethane group concentration of thermoplastic polyurethane resins.

In order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. 60-7601
No. 7 proposed a magnetic recording medium containing a thermoplastic polyurethane-urea resin obtained by reacting a long-chain dionope, a short-chain diol, an organic diamine, and an organic diisocyanate as a binder for the magnetic layer.

By using the above thermoplastic polyurethane-urea resin as a binder, the thermal properties, blocking resistance, durability, etc. of the magnetic layer can be significantly improved, and the above thermoplastic polyurethane-urea resin can be used as a general-purpose solvent. Since it is soluble, the cost in the manufacturing process is also large.

However, when the above-mentioned thermoplastic polyurethane-urea resin is used as a binder, a curing agent is required to harden the binder, and the curing process requires a long heat treatment. Problems include the process required and deterioration of shape due to changes such as volumetric shrinkage of the resin. Furthermore, with the above resins, the pot life after addition of the curing agent becomes a problem, which places restrictions on the handling of magnetic paints.

Furthermore, when the above-mentioned thermoplastic polyurethane-urea resin is used as a binder for the magnetic layer, there is a problem in running stability because the resin itself lacks lubricity.

[Problem that the invention seeks to solve]

The present invention has been proposed to solve the above problems, and while securing the advantages of electron beam sensitive double bonds,
The object of the present invention is to provide a magnetic recording medium that has excellent thermal properties, anti-blocking properties, durability, running stability, and good magnetic properties and electromagnetic conversion properties.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned object, the present inventors have discovered that a thermoplastic polyurethane-urea resin having an electron beam-sensitive double bond in its molecule and a siloxane bond in its molecular chain can be used for magnetic recording. The present invention was completed by discovering that it is useful for improving the blocking resistance of the magnetic layer of the medium and improving the running stability, etc., and that it is easily dissolved in general-purpose solvent systems and is easy to handle. In a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a support, the magnetic layer has an electron beam-sensitive double bond in the molecule and siloxane in the molecular chain. It is characterized by containing a thermoplastic polyurethane-urea resin having a bond as a binder.

The thermoplastic polyurethane-urea resin used in the present invention is characterized by having a urethane bond and a urea bond (urea bond) in its molecule, and furthermore, an electron beam sensitive double bond and a siloxane bond are introduced. It is characterized by

In addition, the urethane bond and urea bond described above play an important role in improving the thermal properties of the binder resin, and can increase the softening point temperature, which is a measure of heat resistance, and lower the glass transition point temperature, allowing a wide range of Stable physical properties of the magnetic layer are maintained over a temperature range, which is extremely effective in improving blocking resistance.

That is, by introducing a urea group, the thermal properties of the resin can be significantly improved, similar to the urethane group.

More importantly, the introduction of this urea group makes it possible to obtain a resin that is soluble when used in combination with the aforementioned ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, and aliphatic hydrocarbon-based solvents. It is. In addition, since the concentration of urethane groups and urea groups in the thermoplastic polyurethane-urea resin molecules can be higher than that of general thermoplastic polyurethane resins, the interaction between molecules becomes stronger, and the physical properties of the resulting magnetic layer are improved. It also improves durability. That is, by using the thermoplastic polyurethane-urea resin as a binder for a magnetic recording medium, a magnetic recording medium with excellent blocking resistance and durability can be provided.

The total concentration of urethane groups and urea groups in the thermoplastic polyurethane-urea resin is 1.8 mmo I
/g to 3.0 mmo I /9 is preferred.

If the concentration is less than 1.8 mmol 7 g, the softening point of the resin will be lowered and the blocking resistance will not be improved, and if the concentration exceeds 3.9 mmol I 7 g, it will become insoluble in general-purpose solvents and will not dissolve in dimethylformamide etc. It will only dissolve. Further, the ratio of urea group concentration/urethane group concentration is preferably 0.3 to 1.6. If the ratio of urea group concentration/urethane group concentration is less than 0.8, it will become insoluble in general-purpose solvents, and if the ratio of urea group/urethane group concentration exceeds 1.6, the glass transition point of the resin will become high. .

In addition, the electron beam-sensitive double bonds introduced into the thermoplastic polyurethane-urea resin include acrylic and methacrylic double bonds, but these double bonds are easily cleaved by electron beam irradiation. Since a crosslinked structure can be formed, the curing time of this resin can be greatly shortened, and the abrasion resistance and durability of the magnetic layer can be improved.

The amount of electron beam sensitive double bond introduced into the thermoplastic polyurethane-urea resin is O.1 mmol/g to 1°Q m
It is preferable that the amount is in the range of mol 7g. If the amount of the double bond introduced is less than 7 g of Q, l mmo I, the curing reaction will not proceed quickly, and the strength etc. of the resulting coating film will decrease. Furthermore, if the amount of double bonds introduced exceeds 1.0 mmo I 7g, the crosslinking concentration will become too high, resulting in a coating structure with poor durability, or the reactivity will become too high, making it difficult to handle. This can lead to disadvantages such as becoming stiff.

Furthermore, the siloxane bond introduced into the molecular chain of the thermoplastic polyurethane-urea resin imparts lubricity to the resin itself, making it possible to provide a magnetic recording medium with excellent running stability.

The siloxane group concentration of the thermoplastic polyurethane-urea resin is 0.03 mmol 7g to 8 mmol 1
/g is preferable, Q, 1 mmol/g ~ Q
, 7 mmol/9 is more preferable. If the siloxane group concentration is less than 0.08 mmol/g, it will not be possible to impart lubricity, and if the siloxane group concentration exceeds 3 mmol/g, the solubility with the melt and other properties will be impaired. Not only does the compatibility with the binder resin deteriorate, but also the physical properties of the magnetic coating, such as breaking strength and Young's modulus, deteriorate.

By the way, the thermoplastic polyurethane used in the present invention
The number average molecular weight of the urea resin is preferably in the range of 2,000 to 60,000, more preferably 5,000 to 40,000. If the number average molecular weight is less than 2,000, the coating film forming ability of the resin will be insufficient, and if the number average molecular weight exceeds 60,000, problems may occur in paint manufacturing processes such as mixing, transport, and coating. occurs.

Furthermore, it is desirable that the softening point temperature of the thermoplastic polyurethane-urea resin is 80°C or higher, more preferably 100°C or higher. If the softening point temperature is lower than this, the properties will approach those of conventional thermoplastic polyurethane resins, making it impossible to improve blocking resistance and physical properties.

Further, it is desirable that the glass transition temperature of the thermoplastic polyurethane-urea resin is 0°C or lower, more preferably -10°C or lower. If the glass transition point temperature is higher than this, the transition region of physical properties approaches room temperature, which is not preferable.

Next, a method for producing the thermoplastic polyurethane-urea resin used in the magnetic recording medium of the present invention will be described.

Thermoplastic polyurethane-urea resins contain long chain diols,
It is obtained by polyaddition reaction of short chain diols, organic diamines and organic diisocyanates.

In this polyaddition reaction, a mixture of a long-chain diol and a short-chain diol is reacted with an organic diisocyanate in advance to prepare a prepolymer with an isocyanate group terminal, and then an organic diamine is added to extend the chain and introduce a urea group. It is carried out by the prepolymer method.

The long-chain diol used in the production of the thermoplastic polyurethane-urea resin has a molecular weight of about 500 to about 5,000, and is roughly classified into, for example, polyester diol, polyether diol, polyether ester glycol, and the like. Specific examples of polyester diols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and acelaic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, or their lower alcohol nysterates, ethylene glycol, 1, 8-propylene glycol, 1,4-butylene glycol, 1,6-hexane glycol, diethylene glycol, neopentine glycol, or an ethylene oxide adduct of hisphenol A, or a mixture thereof. and lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-cabrolactono. Examples of the polyether diol include polyalkylene ether glycols such as polyethylene glycol, polypropylene ether glycol, and polytetranotylene ether glycol, and copolymerized polyether glycols thereof.

Examples of polyether ester glycols include polyester glycols obtained by reacting the above polyalkylene ether glycol as a polyol component with an aliphatic or aromatic dicarboxylic acid. If the molecular weight of this long-chain diol is too small, the urethane group concentration of the resulting thermoplastic polyurethane-urea resin will become too large, resulting in poor flexibility of the resin and poor solubility in solvents, resulting in poor magnetic recording media. It is less preferred for use as a binder. Additionally, if the molecular weight of the long-chain diol is too large, the content of the long-chain diol in the resin will be too large and the urethane group concentration will be relatively very low, resulting in a decrease in the abrasion resistance and heat resistance of the resin. do.

On the other hand, the short chain diol used in the production of the thermoplastic polyurethane-urea resin has a molecular weight of about 50 to about 500.
Examples include ethylene oxide adducts or propylene oxide adducts to aliphatic glycols or bisphenols such as ethylene glycol, propylene glycol, 1,4-butylene glycol, 6-hexane glycol, and neopentyl glycol, and hydroquinone. There are aromatic diols such as ethylene oxide adducts, etc., and these can be used alone or mixed in various ratios depending on the desired properties of the polyurethane-urea resin.

In addition, examples of the organic diamine include aliphatic diamines such as tetramethylene diamine and hexamethylene diamine;
m-phenylenediamine, p-phenylenediamine, 2
, 4-tolylene diamine, 2,6-tolylene diamine,
m-xylylene diamine, p-xylylene diamine, diphenylmetabiphenylene diamine, 4,4-diaminodiphenyl ether, ■, 5-naphthalenediamine, 2
Aromatic diamines such as ゜4-naphthalenediamine, 1.
Examples include alicyclic diamines such as 3-diaminomethylcyclohexane, 1,4-diaminomethylcyclohexane, 4,4-diaminodicyclohexylmethane, and inphorondiamine.

Further, as the organic diisocyanate, aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2
．． 4-1-lylene diisocyanate, 2.6-tolylene diisocyanate, diphenylmethane diisocyanate, 3,3-simethoxy 4,4-biphenylene diinocyanate, 4,4-diisocyanate diphenyl ether, ■ , Aromatic diisocyanates such as 5-naphthalenediisocyanate, 2,4-naphthalenediisocyanate, ■, 3-diisocyanatomethylcyclohexane, 1,4-diisocyanatomethylcyclohexane, 4,4-diyne Examples include alicyclic diisocyanates such as cyanate dicyclohexylmethane and inphorone diisocyanate.

Incidentally, in the above reaction, the molar ratio of the short chain diol to the long chain diol is preferably 8 or less. If this molar ratio is too large, the urethane group concentration will be too high, and the produced polyurethane-urea resin will not be soluble in the above-mentioned general-purpose solvents used in preparing magnetic paints, making it less suitable. When using a straight chain diol such as ethylene glycol, 1,4-butylene glycol, 1.6-hexane glycol as the short chain diol, the above molar ratio is desirably 1 or less, preferably 0.5 or less, and neopentyl glycol If branched short chain diols such as ethylene oxide or propylene oxide adducts to bisphenol are used, the solubility of the resin is good, so the above-mentioned molar ratio can be increased compared to the case of straight chain diols. However, even in this case, if the above-mentioned molar ratio is too large, exceeding 3, the solubility will deteriorate and this is not desirable. Furthermore, depending on the molecular weight of the long-chain diol or short-chain diol, it is also possible to use either one of them alone.

In producing the thermoplastic polyurethane-urea resin used in the present invention, long-chain diols having a molecular weight of about 500 to about 5,000 are selected from among the above-mentioned examples, particularly polyester diols, especially polybutylene adipate, polyhexamethylene adipate, and polycabrofluoride. Preferably, lactone diols are used. Further, as the short chain diol having a molecular weight of about 50 to about 500, among the above-mentioned examples, it is particularly preferable to use a branched short chain diol, especially neopentyl glycol. Further, as the organic diamine, it is particularly preferable to use inphorone diamine among the examples mentioned above. In addition, among the above-mentioned examples, organic diisocyanates include
It is preferable to use 4-diphenylmethane diisocyanate and inphorone diincyanate.

In addition, the polyaddition reaction method employed in the production of the thermoplastic polyurethane-urea resin used in the present invention includes melt polymerization in which the reaction is carried out in a molten state, and the use of single or mixed solvents such as ethyl acetate, methyl ethyl ketone, acetone, and toluene. Solution polymerization is carried out by dissolving the above-mentioned raw materials in an inert solvent, but solution polymerization is preferable for producing resins that are often dissolved in solvents, such as binders for magnetic recording media. It is more preferable to carry out melt polymerization when preparing the prepolymer, and then to carry out solution polymerization by adding the above-mentioned inert solvent before performing the chain extension reaction.

During the reaction, an organometallic compound such as an organotin compound such as stannous octylate or dibutyltin dilaurate, or a tertiary amine such as N-methylmolorin or triethylamine may be added as a catalyst. Also, to increase the stability of the product, antioxidants, ultraviolet absorbers,
A hydrolysis inhibitor or the like may be added.

By the way, it is necessary to introduce an electron beam-sensitive double bond such as an acrylic group or a methacrylic group into the above-mentioned thermoplastic polyurethane-urea resin, and the method for this introduction is as follows: (1) Starting raw material of the thermoplastic polyurethane-urea resin Method using an organic diamine, organic diisocyanate or diol having an electron beam-sensitive double bond as a terminal O of thermoplastic polyurethane-urea resin (2)
Examples include a method of modifying the H group to introduce an electron beam sensitive double bond.

That is, according to the method (1) above, the organic diamine, organic diisocyanate, or diol having the electron beam sensitive double bond is polymerized with other raw materials to form one part of the polymer molecular chain of the thermoplastic polyurethane-urea resin. constitutes the department,
Electron beam sensitive double bonds are introduced into the resulting thermoplastic polyurethane-urea resin.

For example, in order to obtain an organic diamine having a double bond as described above, a functional group that reacts with active hydrogen a of an amine group and a compound having a double bond 1 that is easily cleaved by electron beam irradiation and an organic triamine or What is necessary is to react with an organic diamine. For example, if glycidyl acrylate or glycidyl methacrylate and organic diamine are reacted in equimolar amounts, the formula (wherein R1 represents a hydrogen atom or a methyl group, and R2 represents a
represents a valent hydrocarbon group. ) An organic diamine having an electron beam-sensitive double bond as shown in the following is obtained.

Moreover, in order to obtain the above-mentioned organic diincyanate having a double bond, active hydrogen and compound a having an electron beam sensitive double bond may be reacted with an organic triisocyanate. Examples of the compounds having active hydrogen and electron beam sensitive double bonds include acrylic acid, knockrylic acid, and their 2-hydroxyethyl esters, 2-hydroxypropyl esters, 2-hydroxybutyl esters, 2-hydroxyoctyl esters, and 2-hydroxypropyl esters. Hydroxydodecyl ester, 2-
Hydroxy-8-chloropropyl varnish f /l/, 2-
Hydroxy-3-acryloxypropyl ester, 2
-hydroxy-3-methacryloxypropyl ester, 2-human 0xy-3-acetoxypropyl ester,
2-hydroxy-3-chloroacetoxypropyl ester, 2-hydroxy-3-dichloroacetoxypropyl ester, 2-hydroxy-3-trichloroacetoxypropyl ester, 2-hydroxy-3-crotonyloxypropyl ester, 2-hydroxy-3-dichloroacetoxypropyl ester -, allyloxy ester, etc., or hydroxy polyacrylates such as trimethylol propane diacrylate, trimenalol f〇 pane dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol pentamethacrylate. On the other hand, the above-mentioned organic triisocyanate represents a substituent of the formula. ), compounds represented by the formula % (wherein R4 represents a divalent hydrocarbon group having 2 or 3 carbon atoms, and e represents an integer of 4 or more) can be used. It is. Examples of the latter include 2-inocyanatoethyl 2,6-dicyanatohexanoate, and 2,6-dicyanatohexanoate.
Examples include 8-incyanatopropyl, 2-incyanato-2-methylethyl 2,6-dicyanatohexanoate, and these can be easily prepared by phosgenating an ester of lysine and an amino alcohol. can be manufactured.

Furthermore, in order to obtain the above-mentioned diol having a double bond, a triol may be reacted with a compound having an electron beam-sensitive double bond and a functional group that reacts with an OH group such as an epoxy group or an aziridinyl group. Examples of the compound having the above-mentioned epoxy group or allidinyl group and an electron beam sensitive double bond include the following compounds (a+ to (C1).

(al (cl La (However, in the formula, R5 represents a hydrogen atom or a methyl group, and n represents an integer of 1 to 8.) Among these, 241-aziridinyl) ether methacrylate, allyl-2-aziridinyl propionyl It is preferable to use ester, glycidyl methacrylate, etc. Also, as the above-mentioned triol.

(5) Glycerin HOCH2-C-CH20H H (Bl Ethylene oxide adduct of glycerin HO
CH2CH20CH2-C-CH20CH2CH20H
OH or “HOCHz CH20CHz -C-CH20CH2C
H20CH2CI-(20H■ OH (C)2-methylpropane-1,2,8-t-diol Ha HOCH2-C-CHz OH ! OH ■)4,4-bis(2-hydroxyethyl)-2-hydroxyben Kun CH2CH20H CHz CHz OH (矧 3-methylbentane-1,3,5-1-liol CH3 HOCH2CH2-C-CH2CH20HCH Old 1..2.6-hexandriol HOCH2CH
CHz CH2CH2CH20HH (Gl 1-bis(2-human O-oxyether)amino-
2-Propanol HOCH2CH2NCH2CH,z OHHz HC-CH8 CH σ] Ethylene oxide adduct of ethanolamine HOCH2CH2NCH2CH20H HC-CH2-CH-OH Ha (Il N-propanol ethylene oxide adduct of ethanolamine HOCH2CH20C H2CH2NCH2CH20CH
Examples include 2CH20HH2 HC-CH3 CH and the like.

On the other hand, method (2) above involves introducing an electron beam sensitive double bond by modifying the OH groups present at both ends of a polyurethane-urea resin whose chain has been extended to a predetermined molecular weight.

In order to modify the above OH group, a functional group capable of reacting with the active hydrogen of the OH group is directly reacted with a compound having an electron beam sensitive double bond, or a compound having an active hydrogen and an electron beam sensitive double bond is used to modify the OH group. and a diisocyanate compound in equimolar amounts to react with one NCO of the diisocyanate compound.
A reaction product is obtained by the reaction of the group with the active hydrogen, and then the terminal OH group of the thermoplastic polyurethane-urea resin is allowed to react with the remaining NCO group of the reaction product.

Examples of compounds that can directly act on the terminal OH groups of the polyurethane-urea resin include the epoxy group or aziridinyl group used to obtain the above-mentioned diol having a double bond, and the electron beam sensitive double bond. Examples include compounds that have When these compounds are allowed to act directly on the terminal OH groups of the polyurethane-urea resin, electron beam sensitive double bonds are introduced. The reaction formula is as follows.

-R-0-CH2CH2N-(CH2) n-COCH
2CH=CH2■
(However, in the formula, R represents a thermoplastic polyurethane-urea resin, R5 represents a hydrogen atom or a methyl group, and n represents an integer of 1 to 8.) Examples of compounds having active hydrogen and electron beam sensitive double bonds used when introducing a double bond include acrylic acid, methacrylic acid, hydroxymethyl ester of acrylic acid or methacrylic acid, 2-hydroxyethyl ester,
-Hydroxyalkyl esters such as hydroxyethyl ester, 4-hydroxybutyl ester, 8-hydroxyethyl ester, acrylamide, methacrylamide, N-methylolacrylamide.

Examples include N-methylol acrylamide. The diisocyanate compounds include aliphatic diisocyanates such as hexamethylene diisocyanate, inphorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, m-phenylene diisocyanate, p- Phenylene diisocyanate, 2.4-1-lylene diisocyanate, 2.6-lylene diisocyanate, 1.3-xylylene diisocyanate, 4-xylylene diisocyanate, 1,5-naphthalene diisocyanate Nat, 4,
4-diphenylmethane diisocyamethane diisocyanate, 3,8-dimethylbiphenylene diinocyanate,
Examples include aromatic diincyanates such as ditolylene diisocyanate and cyanisidine diynanate.

These reaction formulas are shown below.

i -0CN-R-NHC・-0-C-C=CI-12OR ■ R OR CR 111□ I R-OH-)-OCN-R-NHC-0-R-QCC=
CH2o o )(:”■
R R R 00R (However, in the formula, R represents a hydrogen atom or a methyl group, respectively.) Furthermore, a siloxane bond is introduced into the main chain of the thermoplastic polyurethane-urea resin. As a starting material for thermoplastic polyurethane resin,
An example is a method of mixing a compound having a siloxane bond. Specifically, a diol having a siloxane bond or a diamine having a siloxane bond is used as the compound having a siloxane bond, and a portion of the long chain diol is mixed with the diol having the siloxane bond, or a portion of the organic diamine is mixed with the siloxane bond. A diamine having a bond may be mixed.

Examples of the diol having a siloxane bond include compounds represented by the following general formula.

(However, R represents a divalent hydrocarbon group.) Further, examples of the diamine having a siloxane bond include compounds represented by the following general formula.

The molecular weight of the above compound can be 800 to 10,000.

Furthermore, a long-chain diol in which a siloxane bond is introduced in advance can also be used. For example, when synthesizing long chain diols such as polyester diols and polyether ester glycols, the diols having the aforementioned siloxane bonds may be used.

The thermoplastic polyurethane-urea resin synthesized as described above can be used in combination with other thermoplastic resins, thermosetting resins, or reactive resins. In this case, the blending ratio of the thermoplastic polyurethane-urea resin to the total binder of the magnetic layer is preferably 10% by weight or more. If the blending ratio of the thermoplastic polyurethane-urea resin to the total binder ζ is less than 10% by weight, hardly any improvement in the blocking resistance of the magnetic recording medium can be expected.

More preferably, it is 40% by weight or more. The above-mentioned 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 20.
For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, thermoplastic polyurethane elastomer, polyfluoride Synthetic rubber-based thermoplastic resins such as vinyl, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives, polyester resin, and polybutadiene can be mentioned. Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, melamine resins, alkyd resins, silicone resins, acrylic reactive resins, epoxy-polyamide resins, nitrocellulose-melamine resins, and polymer resins. Mixtures of molecular weight polyester resins and inocyanate prepolymers, mixtures of meccrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high molecular weight diols/triphenyls Examples include mixtures of mecun triisocyanates, polyamine resins, and mixtures thereof. Among these, it is desirable to use in combination those with good dispersibility in ferromagnetic powder.

A magnetic layer is formed by dispersing ferromagnetic powder in the above-mentioned binder, dissolving it in an organic solvent, and coating it on a nonmagnetic support.

Examples of the ferromagnetic powder used in the present invention include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, macrogonal barium ferrite particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles have a value of X in the range of 1.38≦X≦1.50 when expressed by the general formula FeOx, that is, makhemite (γ-PezOa).

X = 1.50), magnetite (Fe3O4, X = 1
．． 33) and (mn et al.'s solid solution (FeOx, 1.
83 (X(1,50)).Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force.Cobalt-containing iron oxides are roughly divided into doped type and coated type. There are two types.

The above-mentioned ferromagnetic chromium dioxide includes Cr0z, or Ru and Sn for the purpose of improving coercive force.

Te, sb, Fe, Ti, V, Mn
It is possible to use a product containing at least one of the following.

As the ferromagnetic alloy powder, Fe, Co, Ni
.

Fe-Co, Fe-Ni, Fe-Co-Ni,
C.

-Ni, Pe-Co-B, Fe-Co-Cr-B
.

Mn-Bi, Mn-kl, Fe-C
o -V, etc. can be used, and in order to improve various properties of these, kl, Si, Ti, Cr, M
Metal components such as n, Cu, and Zn may be added.

Furthermore, in addition to the binder and ferromagnetic fine powder, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and a rust preventive may be added to the magnetic layer.

The above dispersants (pigment wetting agents) include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid,
Fatty acids with 12 to 18 carbon atoms (C0OH) such as lylunic acid and stearolic acid.

R is an alkyl or alkenyl group having 11 to 17 carbon atoms), an alkali metal of the above-mentioned fatty acid (Li.

(Na, etc.) or alkaline earth metals (Mg, Ca, etc.).

Metal soaps consisting of Ba), fluorine-containing compounds of the above fatty acid esters, amides of the above fatty acids, polyalkylene oxide alkyl phosphate esters, trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, The olefins used include ethylene, propylene, etc. In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. These dispersants are added in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.

The above lubricants include dialkylpolysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms) ,
Alkoxy has 1 to 4 carbon atoms), silicone oil such as phenyl polysiloxane, fluoroalkyl polysiloxane (alkyl has 1 to 5 carbon atoms), conductive fine powder such as graphite, molybdenum disulfide, tungsten disulfide, etc. is fine powder, polyethylene, polypropylene, polyethylene vinyl chloride copolymer, plastic fine powder such as polytetrafluoroethylene, α-olefin polymer, unsaturated aliphatic hydrocarbon that is liquid at room temperature (n-olefin double bond is the terminal A compound with approximately 2 carbon atoms bonded to the carbon of
0), monobase Note fatty acid with 12 to 20 carbon atoms and 3 carbon atoms
Fatty acid esters consisting of ~12 monohydric alcohols, fluorocarbons, etc. can be used. These lubricants are added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

The abrasives are commonly used materials such as fused alumina, silicon carbide, and chromium oxide (CrzO3).

Corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main ingredients: corundum and magnetite), etc. are used. These abrasives have a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are used in an amount of 0.5 parts by weight per 100 parts by weight of the binder.
It is added in a range of 20 parts by weight.

The above antistatic agents include conductive fine powders such as carphone blank and carbon blank graft polymer, natural surfactants such as saponin, nonionic surfactants such as alkylene oxide type, glycerin type, and cricidol type, and higher alkyl amines. , quaternary ammonium salts, pyridine and other heterocycles, cationic surfactants such as phosphoniums, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester group, phosphate ester group, etc. , amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amine alcohols, and other amphoteric activators are used. The above conductive fine powder is binder 1
The surfactant is added in an amount of 0.2 to 20 parts by weight per 0.00 parts by weight, and a 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, magnetic customization improvement, lubricity improvement, and coating aids.

As the rust preventive agent, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, synchromate, calcium chromate, strontium chromate, etc. can be used, but in particular, dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite, gel tanolamine phosphate,
Volatile rust inhibitors such as cyclohexylammonium carbonate, hexamethylene diamine carbonate, propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, morpholine stearate (inorganic acid salts of amines, amines or imides) or organic acid salts) improves the rust prevention effect. These rust inhibitors are used in amounts of 0.0 parts by weight per 100 parts by weight of ferromagnetic powder.
It is used in an amount of 1 to 20 parts by weight.

In addition, the constituent materials of the Takechu layer are dissolved in an organic solvent to prepare a magnetic paint, and this is coated on a non-magnetic support.
Ketones such as methyl isobutyl ketone and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl acetate;
Glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, methylene chloride,
Examples include chlorine hydrocarbons such as methylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene. Materials for the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, etc. In addition to cellulose derivatives, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, non-magnetic alloys such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these are used depending on the application. Magnetic metals, ceramics such as glass, pottery, and porcelain; papers such as paper coated with or laminated with baryta or α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, and ethylene-butene copolymers; can also be used. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, card, or drum.

A magnetic paint having the above-mentioned structure is coated on a non-magnetic support according to a conventional method and dried, and then the coated film is calendered and irradiated with an electron beam.

The irradiation amount of the electron beam is preferably in the range of about 1 = 10 Mraa, and about 2 to ? More preferably, it is Mrad. Also, the irradiation energy (acceleration voltage) is approximately 100
It is preferable to set it to KeV or higher. Note that the above calender treatment may be performed after electron beam irradiation.

[For production]

The urethane groups, urea groups, and even siloxane bonds in the thermoplastic polyurethane-urea resin greatly improve its affinity for magnetic powder. Therefore, by using this as a binder, even ultrafine magnetic powder or magnetic powder with a large amount of magnetization can be dispersed well.

At the same time, the siloxane bond has a lubricating effect, which provides good running properties.

On the other hand, due to the electron beam sensitive double bonds introduced into the thermoplastic polyurethane-urea resin, the magnetic layer can be easily cured by electron beam irradiation. 11 yH,,4q
It is soluble in the solvent system for IJ, 2,7-U2A, 1.6□, and 1, and is easy to handle.

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Resin Synthesis Example A thermoplastic polyurethane-urea resin containing a siloxane bond and an electronic surface sensitive double bond in the molecule was synthesized according to the synthesis method described above. Table 1 shows the properties of the synthesized resin.

Table 1 Thousands of equal parts Urethane Urea group Siloxa Electron aW molecular weight Group concentration Concentration N concentration Double bond concentration (mmoLi) (mmol/, 9) (rrmo+/
7 (trmol/, 9) (mlTIQ resin A
18000 1.5 0.8 0.2
0.2 Resin B 18000 1.5 0.8
0.4 0.2 Resin Cl8000 1.5
0.8 0.6 0.2 Resin D l8
000 1.5 1.0 0.4 0.
2 resin E25000]-,51,00,40,2
14tJfJ'8F lR11nfl 1. FI
n (10,4).

Example I C.

7-Fezoa 100 parts by weight Vinyl chloride-vinyl acetate copolymer 12.5 (U
, C, C, VAGH) Thermoplastic polyurethane-urea resin 12.5 (Resin A) Dispersant (lecithin) 1 Lubricant (
Silicone oil) 1 Abrasive (CrzO
a) 2 〃Methyl ethyl ketone 100 〃Methyl isobutyl ketone 50〃Toluene
50〃The above composition was mixed in a ball mill for 48 hours.3
After filtration with a μ filter, it was coated on a 16μ thick polyethylene terephthalate film so that the thickness after drying was 6μ, and after magnetic field orientation treatment, electronic ii! i
It was cured by irradiation of 15 Mrad. After calendering this, it was cut into a % inch width to create a sample tape.

Example 2 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin B) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of example 1. Created.

Example 8 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin C) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of Example 1. Created.

Example 4 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin D) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of Example 1. Created.

Example 5 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin E) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of Example 1. Created.

Comparative Example 1 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin F) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of Example 1. Created.

Comparative Example 2 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin G) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of example 1. Created.

Comparative Example 3 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (resin H) instead of the thermoplastic polyurethane-urea resin (resin A) in the composition of Example 1. Created.

Table 2 shows the measurement results of the coefficient of dynamic friction, amount of powder falling off, adhesive properties, and stealth properties of the above sample tape.

In addition, the coefficient of dynamic friction is determined at a low tape speed (0.4 M/min).
It was measured as the friction coefficient between the magnetic layer surface and Is stainless steel (load: 50 g). The amount of falling powder was evaluated by visually observing the amount of falling powder on the head drum, guide, etc. after running the shuttle 100 times for 60 minutes, and scoring the highest as 0 points and the lowest as 15 points. Adhesive properties were determined by wrapping the sample tape around a reel and leaving it for 24 hours at a temperature of 40°C and a humidity of 8096°C, and then visually evaluating the degree of peeling of the sample tape.
It was scored on a 10-point scale, and the better the adhesive properties, the lower the score. For still characteristics, a 4.2 MHz video signal is recorded on a sample tape, and the playback output is 50%.
The time taken for the decay to decay was measured.

As is clear from the results in Table 2, by using a thermoplastic polyurethane-urea resin containing a siloxane bond as a binder for the magnetic layer, the running properties, anti-blocking properties, and durability of the magnetic recording medium can be improved. The dispersibility of the magnetic powder is greatly improved.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since the binder for the magnetic layer is a thermoplastic polyurethane-urea resin that has an electron beam-sensitive double bond and a siloxane bond in the molecule, it exhibits high affinity for magnetic powder.
Even if the magnetic powder is finely divided or the magnetic powder has a large amount of magnetization, the dispersibility will be good. Therefore, the durability and surface properties of the obtained magnetic recording medium are improved, and the electromagnetic conversion characteristics are also extremely excellent.

In addition, the lubricity provided by the inclusion of siloxane bonds reduces the coefficient of friction and improves running properties.

Furthermore, since the binder has an electron beam-sensitive double bond in its molecule, the magnetic coating film can be easily cured by electron beam irradiation, which greatly simplifies the manufacturing process.
There are also great process benefits, such as improved pot life and coagulation properties of the paint.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, the magnetic layer has an electron beam-sensitive double bond in the molecule and a double bond in the molecular chain. 1. A magnetic recording medium comprising, as a binder, a thermoplastic polyurethane-urea resin having a siloxane bond.