JPS6288135A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder and the surface characteristic of a magnetic layer and to obtain a magnetic recording medium having excellent durability and runnability and good magnetic characteristic and electromagnetic conversion characteristic by incorporating a specific polyurethane resin as a binder into the magnetic layer essentially consisting of ferromagnetic powder and binder. CONSTITUTION:The polyurethane resin having electron ray sensitive double bonds in the molecule, having at least one kind among a -SO3M group, -OSO3M group, -COOM group, -P(=0, side chain) (OM')2 group, and having a siloxane bond in the molecular chain is used as the binder for the magnetic layer which consists essentially of the ferromagnetic powder and binder and is formed on a nonmagnetic base. M is hydrogen or alkali metal, M' is hydrogen alkali metal or hydrocarbon group. The amt. of the electron ray sensitive double bonds to be incorporated into the polyurethane resin is preferably 0.1-1.0mmol/g and the number average mol.wt. of the resin is preferably 2,000-60,000.

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. -303M group, -0805M group in the heavy bond and molecular side chain,
-000M group, -P (0NF) 2 groups (M is hydrogen or alkali metal, M' is hydrogen, alkali metal or hydrocarbon group), and has a siloxane bond in the molecular chain. By using a polyurethane resin with Durability of recording media,
The aim is to improve running stability, magnetic properties, electromagnetic conversion properties, etc.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), have been required to have improved magnetic properties and electromagnetic conversion properties in order to obtain high playback output even when recording at short wavelengths. There is.

As a measure to this end, efforts have been made to make the magnetic powder particles finer and to increase its magnetic force, and there is a strong tendency to increase the packing density of the magnetic powder in the magnetic layer, the so-called backing density.

On the other hand, conventionally used binders for magnetic recording media include nitrocellulose, polyester resin, polyurethane resin, vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate self-vinyl alcohol copolymer, etc. can be mentioned.

However, due to the increase in specific surface area due to the fine particles of magnetic powder and the increase in cohesive force due to high coercive force, the above-mentioned binders cannot provide satisfactory dispersibility and surface properties.
It has also become difficult to increase the backing density of magnetic powders. Therefore, durability, magnetic properties,
The electromagnetic conversion characteristics were also insufficient. Alternatively, methods such as using a surfactant as a dispersant have been considered, but in this case, since the surfactant is a low molecular weight, the presence of this surfactant in the magnetic layer causes the powder to become powdery. Problems have arisen in mechanical strength and durability, such as shedding and blooming due to changes over time.

Under these circumstances, there is a need for a binder that can further improve such properties, and attempts have been made to introduce hydrophilic polar groups into the side chains of various binder resins. Examples of the binder include polyester resin containing a sulfonic acid metal base (Japanese Patent Publication No. 57-3134), polyurethane resin containing a sulfonic acid metal base (Japanese Patent Publication No. 58-4156),
5), -803M group, -0803M group, -C00M group,
- Binder resin containing two P(OM) groups (where M is a hydrogen atom or an alkali metal) as a hydrophilic polar group (JP-A-5
9-79427) etc. are known.

[Problem that the invention seeks to solve]

However, when the above-mentioned various binder resins are used as the binder for the magnetic layer, there is a problem in running stability because the resin itself lacks lubricity.

Furthermore, when the above-mentioned binder is used, a curing agent is required to harden the binder, and the curing process requires a long heat treatment process, and there are problems such as shape deterioration due to changes such as volumetric shrinkage of the resin. It becomes. Furthermore, with the above-mentioned binders, the pot life after adding the curing agent becomes a problem.
There are restrictions on the handling of magnetic paint.

Therefore, the present invention was proposed to solve the above-mentioned drawbacks in the technical field, and it significantly improves the dispersibility of magnetic powder and the surface properties of the magnetic layer while maintaining the advantages of electron beam sensitive double bonds. The object of the present invention is to provide a magnetic recording medium which has improved durability and running stability, and has good magnetic properties and electromagnetic conversion properties.

[Means for solving problems]

As a result of intensive studies, the present inventors have found that the electron beam-sensitive double bond in the molecule and the -8
03M group, -0803M group, -C00M group, -P (O
M') A polyurethane resin having at least one type of two groups (where M is hydrogen or an alkali metal, and M' is a hydrogen, alkali metal, or hydrocarbon group) and has a siloxane bond in its molecular chain is sensitive to electron beams. The present invention was completed by discovering that while maintaining the advantages of double bonds, it has a high affinity for magnetic powder, exhibits lubricity, and has excellent running stability. In a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a body, the magnetic layer has an electron beam sensitive double bond in the molecule and a -3o3M group, -0803M group in the side chain of the molecule. basis,
-C00M group, -P (OM') 2 groups (M is hydrogen or alkali metal, M' is hydrogen, alkali metal, or hydrocarbon group), and has a siloxane bond in the molecular chain. It is characterized by containing a polyurethane resin having the following as a binder.

The polyurethane resin according to the present invention is obtained by reacting a polyhydroxy compound with a polyisocyanate, and the polyhydroxy compound has a molecular weight of about 500 to about 5000.
It is preferable to use long-chain diols having a molecular weight of about 50 to about 500, and it is preferable to use organic diisocyanates as the polyisocyanate.

The above-mentioned long-chain diols are roughly classified into polyether diols, polyether ester glycols, and the like. Specific examples of polyester diols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; 1,3
-To propylene glycol 1.4--Polyester diol obtained by reacting with ethylene glycol, 1,6-hexane glycol, diethylene glycol/neopentyl glycol, or an ethylene oxide adduct of hisphenol A, or a mixture thereof. Examples include lactone-based polyester diols obtained by ring-opening polymerization of lactones such as or ε-caprolactone. Examples of the polyether diol include polyethylene glycol, polypropylene ether glycol, polytetramethylene ether glycols, 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 polyurethane resin will be too high, resulting in poor flexibility of the resin and poor solubility in solvents, making it difficult to use as a binder for magnetic recording media. I don't like it very much. Furthermore, when the molecular weight of the long-chain diol is too large, the long-chain diol content in the resin becomes too large and the urethane group concentration becomes relatively low, resulting in a decrease in the abrasion resistance and heat resistance of the resin.

Examples of the short chain diols include ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,
Aliphatic glycols such as 6-hexane glycol and neohentyl glycol, or ethylene oxide adducts or propylene oxide adducts of bisphenol A;
There are aromatic diols such as ethylene oxide adducts of hydroquinone, and these can be used alone or in mixtures in various ratios depending on the desired properties of the polyurethane resin.

Furthermore, glycerin, glycerin ethylene oxide adduct, 2-methylpropane-1,2,3-triol,
4-1: Bis(2-hydroxyethyl)]-]2-hydroxypenkune 3-methylpenkune-1,3,5-1-
Diol, 1,2.6-hexane glycol, 1-bis(2-hydroxyethyl)amine-2-propatol,
It is also possible to use a triol such as a propylene oxide adduct of jetanolamine.

Examples of the organic diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2.6-1-lylene diisocyanate, diphenylmethane diisocyanate, 3.3
'-Dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, 1°5-naphthalene diisocyanate, 2
, 4-naphthalene diisocyanate, etc., 1,3-diisocyanatomethylcyclohexane, 1,4-diisocyanatomethylcyclohexane, 4,4'-diisocyanatodicyclohexyl methane, inphorone diisocyanate Examples include fatty group diisocyanates such as.

In addition, the reaction method adopted in the production of the polyurethane resin according to the present invention includes melt polymerization in which the reaction is carried out in a molten state, and the above-mentioned raw materials are added to an inert solvent such as a single or mixed solvent of ethyl acetate, methyl ethyl ketone, acetone, toluene, etc. There is solution polymerization, which is carried out by dissolving the
Solution polymerization is preferred for the production of polyurethane resins, which are often dissolved in solvents and used as binders for magnetic recording media.In particular, when preparing a prepolymer, melt polymerization is performed, and the above-mentioned non-containing substances are removed before chain extension reaction. It is more preferable to perform solution polymerization by adding an active solvent.

In the reaction, an organometallic compound such as an organotin compound such as stannous octylate or dibutyltin dilaurate, or a tertiary amine such as N-methylmorpholine 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 in an amount within about 5 times the solid content.

Hydrophilic polar groups and electron beam-sensitive double bonds are introduced into the polyurethane resin, and methods for introducing these hydrophilic polar groups and double bonds include the following methods.

(1) A method in which a hydrophilic polar group-containing compound and a compound having an electron beam-sensitive double bond are mixed as starting materials for a polyurethane resin.

(2) A method in which a compound having an electron beam-sensitive double bond is mixed as a starting material for a polyurethane resin, and the terminal OH groups of the resulting polyurethane resin are modified with a hydrophilic polar group-containing compound.

(3) A method in which a hydrophilic (distortion group-containing compound) is mixed as a starting material for a polyurethane resin, and the terminal OH groups of the resulting polyurethane resin are modified with a compound having an electron beam-sensitive double bond.

Examples of the hydrophilic polar group-containing compound used in the method (1) above include hydrophilic polar group-containing diols and hydrophilic polar group-containing organic diisocyanates, and compounds having an electron beam-sensitive double bond include Examples include diols having an electron beam sensitive double bond and organic diisocyanates having an electron beam sensitive double bond. If these compounds are mixed as starting materials for polyurethane resin, they will form part of the polymer molecular chain of polyurethane resin obtained by polymerizing with other materials, resulting in hydrophilic polar groups and electron beam sensitive double bonds. is introduced as a side chain.

The hydrophilic polar group-containing diol has the general formula (wherein R1 is an alkylene group having 2 to 6 carbon atoms or a substituted product thereof, R2 is an alkylene group having 1 to 6 carbon atoms or a substituted product thereof, R3 and R4 are (represents an alkyl group having 1 to 6 carbon atoms).

Alternatively, it may be a diol having a -803M group (where M represents a hydrogen atom or an alkali metal).

This diol having a -803M group includes a carboxylic acid component not having a -803M group, a glycol component and a 18O
It can be obtained by reacting an aM group-containing aphonic acid component.

As for the above-mentioned carboxylic acid component not having the -803M group,
Terephthalic acid, isophthalic acid, orthophthalic acid, 1,5
- Aromatic dicarboxylic acids such as naphthalic acid, p-oxybenzoic acid, aromatic oxycarboxylic acids such as p-(human coxhetoxy)benzoic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedigalboxylic acid, etc. aliphatic dicarboxylic acids, tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

The above-mentioned glycol components include ethylene glycol, fluoropylene gellicol, 1,3-propanediol, 1,
4-butanediol, 1,5-bentanediol, 1,
6-hexanediol, neohair f-lulicol,
Diethylene glycol, dipropylene glycol, 2
+ 2+ 4 F 1,3-bentanediol, 1,4-cyclohexane dimetatool, ethylene oxide and propylene oxide adducts of bisphenol A, ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A, polyethylene Examples include glycol, polypropylene glycol, polytetramethylene glycol, and the like.

Further, tri- and tetraols such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol may be used in combination.

The dicarboxylic acid component having the -503M group is as follows:
5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid,
Examples include 2-potassium sulfoterephthalic acid.

In addition, the above hydrophilic polar group-containing organic diisocyanate is
It can be obtained by reacting a trifunctional or more functional polyisocyanate compound with a compound having a hydrophilic polar group.

As the above-mentioned polyisocyanate compounds, trifunctional products such as Desmodur Shikaku (manufactured by Bayer AG) and Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) are known.
Generally, a polyfunctional polyisocyanate compound is obtained by addition-reacting a polyol and a polyisocyanate.

Examples of polyols include propylene glyconopec, lycerol, trimethylolpropane, pentaerythritol, sorbitol, and the like.

Examples of polyisocyanates include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, inphorone diisocyanate, xylene diisocyanate, and lysine diisocyanate. Can be mentioned.

A method for introducing the hydrophilic polar group into this trifunctional or higher functional polyisocyanate compound will be schematically shown below.

■ Method of introducing -503M group By reacting a compound having -503M group in one molecule and an active hydrogen capable of reacting with -NGO group with a trifunctional or higher functional polyisocyanate compound,
Has two or more -NGO groups in one molecule and -803M
A compound having a group is obtained.

Compounds that have -SO3M groups in one molecule and active hydrogen that reacts with -NGO groups include the following: These compounds include trifunctional or higher functional polyisocyanate compounds and, for example, The addition reaction is carried out as shown in the reaction formula.

(In the reaction formula, R-NGO represents a trifunctional or higher functional polyisocyanate compound.) ■ Method for introducing -〇〇〇M group When one molecule has 1〇〇〇〇M group and -NGO group By reacting a compound having active hydrogen capable of reacting with a trifunctional or more functional polyisocyanate compound,
A compound having two or more -NGO groups and 1000M groups in the molecule is obtained.

Examples of the compound having 1000M groups in one molecule and active hydrogen capable of reacting with the -NCO group include the following.

These compounds undergo an addition reaction with a trifunctional or higher functional polyisocyanate compound, for example, as shown in the following reaction formula.

(In the reaction formula, R-NCO represents a trifunctional or higher functional polyisocyanate compound.) ■ Method for introducing -0803M group The reaction product of a trifunctional or higher functional polyisocyanate compound and H2SO4 is mixed with NaOH, KOH, etc. By neutralization, a compound having two or more --NCO groups in the molecule and having a 10803M group can be obtained, for example, as shown in the following reaction formula.

R-NCO+H2So4 → Ru → Old Co-08O3HR
-NHCO-O20:+H+NaOH-+R-NHCO
-O8O3Na+H20 (In the above reaction formula, R-N
CO represents a trifunctional or higher functional polyisocyanate compound. ) ■ Method 3 of introducing -P (OM' ) 2 group
By neutralizing the reaction product of a functional or higher polyisocyanate compound and H3PO3 with NaOH, KOH, etc., it can be obtained, for example, as shown in the following reaction formula.

R-NCO+H3P03→R-NHCO-P (OH)
2R-NHCO-P(OH) z+2NaOH-+
R-NHCO-P(ONa) 2+2H20 (In the above reaction formula, R-NCO represents a trifunctional or more functional polyisocyanate compound.) In addition, in order to obtain the organic diisocyanate having the above double bond, active hydrogen A compound having an electron beam sensitive double bond may be reacted with an organic triisocyanate. Examples of the above-mentioned compounds having active hydrogen and electron beam sensitive double bonds include acrylic acid, methacrylic acid, and their 2-hydroxyethyl esters, 2-hydroxypropyl esters, 2-hydroxybutyl esters, 2-hydroxyoctyl esters, 2- Hydroxydodecyl ester, 2-hydroxy-3-chloropropyl ester, 2-hydroxy-3-acryloxypropyl ester, 2-hydroxy-3-methacryloxypropyl ester, 2-hydroxy-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-allyloxy ester, etc., or trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, pentaerythritol triacrylate, pentaerythritol methacrylate, Examples include hydroxy polyacrylates such as dipentaerythritol pentaacrylate and dipentaerythritol pentamethacrylate. On the other hand, the above-mentioned organic triisocyanate represents a substituent having the formula %. ) or a compound represented by the formula 0CN-(CH2)L-CH-NCO l C=O 0-R4-NGO (wherein R4 represents a divalent hydrocarbon group having 2 or 3 carbon atoms, and t is Represents an integer of 4 or more.) Compounds represented by the following can be used. Examples of the latter include 2-isocyanatoethyl 2,6-dicyanatohexanoate and 2,6-dicyanatohexanoate.
Examples include 3-incyanatopropyl, 2-isocyanato-2-methylethyl 2,6-dicyanatohexanoate, and these are all produced by phosgenating an ester of lysine and an amino alcohol. Can be easily manufactured.

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

(c) Rs (However, in the formula, R5 represents a hydrogen atom or a methyl group, and n represents an integer of 1 to 8.) Among these, 2-(1-
Preference is given to using aziridinyl)ethyl methacrylate, allyl-2-aziridinylpropionate, glycidyl methacrylate, and the like. In addition, the above-mentioned triols include (a) glycerin ■ HOCH2-C-CH20H CH (b) ethylene oxide adduct of glycerin ■ HOCH2CH20CH2-C-CH20CH2CH2
0HCH or HOCH2CH20CH2-C-CH20CH2CH2
0CH2CH20HCH (C) 2-methylpropane-1,2,3-triol H
3 HOCH2-C-CH20H CH (d) 4.4-bis(2-hydroxyethyl)-2
=Hydroxypenkune CH2CH20H CH20H20H (e) 3-Methylpentane-1,3,5-triol H
3 HOCH2CH2-C-CH2CH20HCH (f) 1.2.6-hexanetriol HOCH2
CHCH2CH2CH2CH20HCH (g) 1-bis(2-hydroxyethyl)amino-
2 -Propacul HOCH2CH2NCHZ CH20HCH2 C -CH3 CH (H) Jetanolamine propylene oxide additives HOCH2CH2NCH2CH20H "CH3 (Li -Impro Pattern Jetanol Amin ethylene oxide additives HOCH2 HOCH2 CH20ch2ch2nch2ch20ch
Examples include 2CH20HOH2C-CH3OH.

Next, the method (2) above will be explained. In the method shown in (2), a compound having an electron beam-sensitive double bond is first mixed in as a starting material for a polyurethane resin as in method (1), and the chain is extended to a predetermined molecular weight by a polymerization reaction. , to obtain a polyurethane resin in which the double bond is introduced into the side chain. As the compound having an electron beam sensitive double bond used here, the organic diisocyanate having an electron beam sensitive double bond and the diol having an electron beam sensitive double bond described in method (1) above are used. be able to.

Next, for example, Ct
CHzCHz so sM, CtCH2CH20S0
3M.

C7CHzCOOM, C1,CHzP(OM')z
(However, M represents a hydrogen atom or an alkali metal, and M' represents a hydrogen atom, an alkali metal, or a hydrocarbon group.) Dehydrochlorination reaction between OH groups and chlorine in the presence of dehydrochlorination agents such as amines such as pyridine, picoline, and triethylamine, and epoxy compounds such as ethylene oxide and propylene oxide, in a solvent such as dimethylformamide and dimethyl sulfoxide. A hydrophilic polar group is introduced. The reaction formula is as follows.

(A-1) R' -OH+C4CH2CH2So 3M→R' -
0CH2CH2So aM+Hct""-(A-2) R'-OH+CtCH2CHzO803M→R' -
OCH2CH20S03 M+HC4(A-3) R' -OH+CtcH2C00M →R'-OCH2COOM+HC7 (A-4) R' -OH+CIcH2P (OM' ) 2→R'
-0CR2P (OM') 2 +HCt (However,
R' represents a polyurethane resin into which an electron beam sensitive double bond is introduced. ) Alternatively, although some by-products are generated, the following method can also be introduced. That is, HOCH2CH2So 3M.

HOCH2CH2OSo3M, HOCH2C00
M, HOCH2P (OM') 2 and a diisocyanate compound, for example, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, are reacted in equimolar amounts to form a diisocyanate. A reaction product is obtained by the reaction between one NCO group and the OH group in the molecule. Next, - of polyurethane resin
By reacting the OH group with the remaining NCO group, a polyurethane resin having a hydrophilic polar group and an electron beam-sensitive double bond introduced therein can be obtained.

(B-1) OCN-Politics-NCO+HOCH2CH2S03M→0C
N-tun NHCOOCH2CH2SO3MR-OR+OC
N-R-NHCOOCH2CH2So3M→R-OCO
NH-R-NHCOOCH2CH2So3M (B-2) OCN-R-NCO+HOCH2CH20S03M→O
CN-R-NHCOOCH2CM2O803MR-OR
+OCN-R-NHCOOCH2CH20S03M→R
-OCONH-R-NHCOOCH2CH2O803M
(B-3) OCN-R-NCO+HOCH2COOM→OCN-R
-NHCOOCH2COOMR-OH+OCN-R-N
HCOOCH2COOM-→R-OCONH-R-NH
COOCH2COOM(B-4) OCN-R-NCO+HOCH2P(OM)2-0CN
-d-NHC0OCH2P (OM) 2R-OH+○
cN-i'-■C00CH2P (OM) 2 (However, R represents a polyurethane resin into which an electron beam sensitive double bond has been introduced, and R represents a divalent hydrocarbon group.) On the other hand, in (3) above, The method is opposite to method (2) above, in which the terminal OH group of a polyurethane resin into which a hydrophilic polar group has been introduced as a side chain is modified with a compound having an electron beam-sensitive double bond. .

That is, in the method shown in (3) above, first, a hydrophilic polar group-containing compound is mixed as a starting material for a polyurethane resin, and this compound is polymerized with other raw materials to extend the chain to a predetermined molecular weight. A polyurethane resin in which a hydrophilic polar group is introduced into a side chain is obtained. As the hydrophilic polar group-containing compound used here, the hydrophilic polar group-containing organic diisocyanate described above in the method (1) can be used.

Next, the OH group present at the end of the polyurethane resin into which this hydrophilic polar group has been introduced is modified to introduce an electron beam sensitive double bond. Either by directly reacting a compound having an electron beam-sensitive double bond with a functional group capable of reacting with the active hydrogen of A reaction product is obtained by reacting one NCO group of the diisocyanate compound with the above active hydrogen, and then the terminal OH group of the above polyurethane resin is reacted with the remaining NGO group of the above reaction product. Bye.

Compounds that can act directly on the terminal OH groups of the polyurethane resin include the epoxy group or aziridinyl group used to obtain the diol having a double bond as described in method (1) above, and the electron beam sensitive diol. Examples include compounds having a double bond. If these compounds are allowed to act directly on the terminal OH groups of the polyurethane resin, electron beam sensitive double bonds will be introduced. The reaction formula is as follows.

(C-1) (C-2) I ll OH0 (In the formula, R represents a polyurethane resin into which a hydrophilic polar group has been introduced, R5 is a hydrogen atom, a methyl group, and n is 1
Represents an integer from ~8. ) On the other hand, the compounds having active hydrogen and electron beam sensitive double bonds used when introducing electron beam sensitive double bonds through the above isocyanate compound include acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. Hydroxymethyl ester, 2-hydroxyethyl ester, 3-hydroxypropyl ester,
Examples include hydroxyalkyl esters such as 4-hydroxybutyl ester and 8-hydroxyoctyl ester, acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide.

The diisocyanate compounds include aliphatic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, m-phenyl diisocyanate, p- -phenylene diisocyanate, 2,4-tolylene diisocyanate-1, 2゜6-tolylene diisocyanate, 1,3-
xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,5-naphthalene diisocyanate,
Aromatic diisocyanates such as 4,4-diphenylmethane diisocyanane diisocyanate, 3,3-dimethylbiphenylene diisocyanate, ditolylene diisocyanate, dianisidine diisocyanate, and the like can be mentioned. These reaction formulas are shown below.

(D-1) &R'-oa+ocN-i'-NHc-oc-Lcaz
0 0 R5 (D-2) (D-3) ORs (In the formula, R is a polyurethane resin into which a hydrophilic polar group has been introduced, R and Rx are divalent hydrocarbon groups, and R5 is a hydrogen atom or a methyl group. Furthermore, siloxane bonds are introduced into the molecular chain (main chain) of the polyurethane resin, and one method for introducing them is to mix a compound having a siloxane bond into the starting material of the polyurethane resin. Can be mentioned. Specifically, a diol having a siloxane bond may be used as the compound having the siloxane bond, and the diol having the siloxane bond may be mixed into a portion of the polyhydroxy compound.

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

(However, R represents a divalent hydrocarbon group.) The molecular weight of the above compound is 300 to 1ooo.

can be used.

It is also possible to use a polyhydroxy compound in which a siloxane bond is introduced in advance.

For example, when synthesizing polyhydroxy compounds such as polyester diols and polyether ester diols, the diols having the aforementioned siloxane bonds may be used.

The amount of polar groups introduced into the polyurethane resin according to the present invention is 0.
．． It is preferably in the range of 01 to 1.0 mmol 1/i/, and more preferably in the range of 0.1 to 0.5 mmol/y. The amount of introduced polar group is 0.01 mmn1
If it is less than /Si', sufficient effect on the dispersibility of the ferromagnetic powder will not be recognized. In addition, the amount of the polar group introduced is 1.0
mmol/? If it exceeds this, intermolecular or intramolecular aggregation tends to occur, which not only adversely affects dispersibility, but also
There is also the possibility that selectivity with respect to the solvent may occur, and ordinary general-purpose solvents may no longer be usable.

Furthermore, the siloxane group concentration of the polyurethane resin according to the present invention is 0.03 mmo 1/S' to 3 mmo
1/S'tearnoca is preferred, 0.1 mmo 1/
More preferably, f is 0.7 mmo. If the siloxane group concentration is less than 0.03 mmo 179, lubricity cannot be imparted, and if the siloxane group concentration exceeds 3 mmo 115', the solubility with solvents and compatibility with other binders may deteriorate. Not only does this deteriorate, but also physical properties such as the breaking strength and Young's modulus of the magnetic coating film deteriorate.

Further, the amount of electron beam sensitive double bonds introduced into the polyurethane resin according to the present invention is preferably in the range of 0.1 to 1.0 mmo 1/f. The amount of introduced double bonds is 0.
If it is less than 1 mmol/y, not only will the curing reaction not proceed quickly, but the strength etc. of the resulting coating film will decrease. Furthermore, if the amount of double bonds introduced exceeds 1.0 mmol/y, the crosslinking density 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 results in disadvantages such as:

Furthermore, the number average molecular weight of the polyurethane resin according to the present invention is from 2,000 to 60,000, more preferably from 5,000 to 40.
Preferably, it is in the range of 000. Number average molecular weight is 2
If the number average molecular weight is less than 000, the coating film forming ability of the resin will be insufficient, and if the number average molecular weight exceeds 60,000, there is a risk that problems will occur in paint manufacturing processes such as mixing, transport, and coating.

The polyurethane resins according to the invention can be used in combination with other thermoplastics, thermosets or reactive resins. The above-mentioned thermoplastic resin has a softening temperature of 150°C or less and an average molecular weight of 10,000 to 20,000.
0 and the degree of polymerization is about 200 to 2000, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer. , thermoplastic polyurethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, polybutadiene, and other synthetic rubber-based thermoplastic resins. It will be done. 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 isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high molecular weight diols/triphenylmethane Mixtures of triisocyanates, polyamine resins, mixtures thereof, and the like can be mentioned. 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, hexagonal barium ferrite particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed by the general formula FeOx, that is, magnetite (r-F13203°X=1.
50), magnetite (Fe30<, X=1.33) and solid solutions thereof (FeOx, 1.33<X<1.50
). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

The above-mentioned ferromagnetic chromium dioxide may include CrOz or Ru for the purpose of improving coercive force thereof.

It is possible to use a material to which at least one of Sn, Te, Sb, Fe, Ti, V, Mn, etc. is added.

As the ferromagnetic alloy powder, Fe, Co, N
i.

Fe-Co, Fe-Ni, Fe-Co-Ni, Co-N
i, Fe-Co-B, Fe-Co-Cr-B
, Mn-B1. Mn-, At, Fe-Co-V, etc. can be used, and for the purpose of improving various properties, At,
Metal components such as Si, Ti, Cr, Mn, 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 dispersant (pigment wetting agent) includes caprylic acid,
12 carbon atoms such as linoleic acid, lylunic acid, stearolic acid, etc.
~18 fatty acids (RC0OH.

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.) or alkaline earth metals (Mg, Ca, etc.)
, Ba), a fluorine-containing compound of the above-mentioned fatty acid Nisder, an amide of the above-mentioned fatty acid, a polyalkylene oxide alkyl phosphate ester, a trialkyl rIJ olefin oxy quaternary ammonium salt (alkyl has 1 to 5 carbon atoms) (Olefins such as ethylene and propylene) are used. In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. These dispersants are 100 parts binder:
It is added in an amount of 0.05 to 20 parts by weight.

The above lubricants include dialkylporinloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 4 carbon atoms), 5, 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, Inorganic fine powder such as songsten sulfide, polyethylene, polypropylene,
Polyethylene vinyl chloride copolymers, fine plastic powders such as polytetrafluoroethylene, α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (compounds in which an n-olefin double bond is bonded to the terminal carbon, carbon Numerical value 20), fatty acid esters consisting of a monobasic fatty acid having 12 to 20 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms, 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.

As the abrasive, commonly used materials such as fused alumina, silicon carbide, chromium oxide (Cr20s), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite) are used. Ru. These abrasives have a Mohs hardness of 5 or more and an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are used in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.
It is added in a range of parts by weight.

The above-mentioned antistatic agents include conductive fine powders such as carbon black, resin, and carbon black graph topomer, natural surfactants such as saponin, alkylene oxide type,
Nonionic surfactants such as glycerin and glycyl-based surfactants, higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, cationic surfactants such as phosphoniums, carboxylic acids, sulfonic acids, phosphorus acid,
Anionic surfactants containing acidic groups such as sulfate ester groups and phosphate ester groups, amino acids, aminosulfonic acids,
Ampholytic activators such as sulfuric acid or phosphoric acid esters of amine alcohols are used. The above conductive fine powder is added in an amount of 0.2 to 20 parts by weight, and the surfactant is added in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the binder. 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.

As the above-mentioned rust preventive agent, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, but in particular, dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite, gel tanolamine phosphate,
Volatile rust inhibitors (inorganic or organic acid salts of amines, amides or imides) such as cyclohexylammonium carbonate, hexamethylene diamine carbonate, propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, and morpholine stearate. When used, the rust prevention effect improves. These rust inhibitors are 0.01 parts by weight per 100 parts by weight of ferromagnetic fine powder.
It is used in a range of 20 parts by weight.

In addition, the constituent materials of the magnetic layer are dissolved in an organic solvent to prepare a magnetic paint, which is applied onto a non-magnetic support.Solvents for the magnetic paint include acetone, meketyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketones, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, acetic acid glycol monoethyl ether, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, aromas such as benzene, toluene, xylene, etc. group hydrocarbons, aliphatic hydrocarbons such as hexane and heptane, methylene chloride, ethylene chloride, carbon tetrachloride,
Examples include chlorine hydrocarbons such as 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,
In addition to cellulose derivatives such as cellulose acetate phthalate and cellulose acetate prozeonate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, and plastics such as polycarbonate, polyimide, and polyamideimide, aluminum, copper, Non-magnetic metals such as tin, zinc or non-magnetic alloys containing these, ceramics such as glass, pottery and porcelain, paper, baryta or α having 2 to 10 carbon atoms such as polyethylene, polypropylene and ethylene-butene copolymers. -Paper such as paper coated or laminated with polyolefins can also be used. The form of the non-magnetic support is film, tape, sheet,
Any disk, card, drum, etc. may be used.

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 amount of electron beam irradiation is preferably in the range of about 1 to 10 Mrad, more preferably about 2 to 7 Mrad. Also, the irradiation energy (acceleration voltage) is approximately 100 KeV
It is better to set it to the above. Note that the above calender treatment may be performed after electron beam irradiation.

[Effect]

Due to the action of the hydrophilic polar groups in the polyurethane resin, the affinity for magnetic powder is greatly improved.

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 bonds have a lubricating effect, which provides good running properties.

On the other hand, due to the electron beam sensitive double bonds introduced into the polyurethane resin, the magnetic layer can be easily cured by electron beam irradiation.

〔Example〕

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

Resin Synthesis Example A polyurethane resin containing a siloxane bond, a hydrophilic polar group, and an electron beam sensitive double bond in the molecule was synthesized according to the synthesis method described above. Table 1 shows the properties of the synthesized resin.

(Left below) Example I Co adhesion r -Fe2C) + 100 parts by weight Acrylic modified hinyl chloride-acetic acid 12.5 // Vinyl-vinyl alcohol copolymer (number average molecular weight: 43o.

Modification amount: 2m01%) Polyurethane resin 12.5//(Resin A) Dispersant (lecithin) 1 Lubricant (silicone oil) 1 Abrasive (C203)
2 〃Methyl ethyl ketone
100 〃Methyl isobutyl ketone
50 Toluene 50 7F
The above composition was mixed in a ball mill for 48 hours and filtered through a 3 μm filter, then coated on a 16 μm thick polyethylene terephthalate film to a dry thickness of 6 μm, subjected to magnetic field orientation treatment, and then subjected to an electron beam of 5 Mrad.
It was irradiated and cured. After calendering this, it was cut into a Z inch width to create a sample tape.

Example 2 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin B) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Example 3 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin C) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Example 4 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin D) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Example 5 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin E) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Example 6 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin F) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Comparative Example 1 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin G) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Comparative Example 2 A sample tape was prepared in the same manner as in Example 1, using a polyurethane resin (Resin H) instead of the polyurethane resin (Resin A) in the composition of Example 1.

Comparative Example 3 A sample tape was prepared in the same manner as in Example 1 except that polyurethane resin (Resin Co., Ltd.) was used in place of the polyurethane resin (Resin A) in the composition of Example 1.

Comparative Example 4 A sample tape was prepared in the same manner as in Example 1, using a polyurethane resin (Resin J) instead of the polyurethane resin (Resin A) in the composition of Example 1.

Table 2 shows the measurement results of the coefficient of dynamic friction, surface gloss, amount of falling powder, adhesive properties, and still properties of the above sample tapes.

Note that the coefficient of dynamic friction is determined by the low tape speed (0,,1ηr,
1n,/Se C) friction coefficient between the magnetic layer surface and IS stainless steel (load 50y):! : Measured. The surface gloss was determined using a glossy needle with an incident angle of 75° and a reflection angle of 7.
The reflectance at 5° was measured. The amount of powder falling off was evaluated by visually observing the amount of powder falling on the head drum, kite, 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 winding the sample tape onto a reel and leaving it for 24 hours at a temperature of 40°C and humidity of 80%, and 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 customization, a 1.2 MHz video signal was recorded on a sample tape, and the time until the playback output attenuated to 50% was measured.

〇-As is clear from the results in Table 2 of Table 2 of Kumquats (Otsu), by using a polyurethane resin containing a siloxane bond and a hydrophilic polar group as a binder for the magnetic layer, the dynamic friction coefficient, surface gloss and The amount of powder falling off is improved, and the adhesive properties and still properties are significantly improved.

Therefore, the thermal characteristics, running stability, and 1
11T pronokinkability, durability, dispersion of magnetic powder, etc. are improved to Daifuku.

[Effects of the Invention As is clear from the above explanation, in the present invention,
Polyurethane resin, which has siloxane bonds and hydrophilic polar groups in the molecule, is used as the binder for the magnetic layer, so it has a high affinity for magnetic powder, even if it is ultra-fine magnetic powder or has a large amount of magnetization. Even if it is a magnetic powder, it will have good dispersibility. 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.

Claims (1)

[Scope of Claims] A magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the magnetic layer has electron beam sensitive double bonds and molecules in the molecules. -SO_3M group, -OSO_3M group, -COOM group in the side chain,
▲There are mathematical formulas, chemical formulas, tables, etc.▼It has at least one type of group (where M is hydrogen or an alkali metal, and M' is a hydrogen, alkali metal, or hydrocarbon group) and has a siloxane bond in its molecular chain. A magnetic recording medium characterized by containing a polyurethane resin as a binder.