JPS6295727A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium having excellent durability, traveling stability, magnetic characteristic, and electromagnetic transducing characteristic by incorporating a specified polyester resin into the magnetic layer on a nonmagnetic carrier as a binder to improve the dispersibility of magnetic powder and the surface property of the magnetic layer. CONSTITUTION:The magnetic recording medium is obtained by forming the magnetic layer consisting essentially of ferromagnetic powder and the binder on the nonmagnetic carrier. In this case, the polyester resin having a siloxane coupling in the molecular chain and having a quaternary ammonium salt in the molecular side chain as a polar group is incorporated into the magnetic layer as the binder. The amts. of the polar group and siloxane to be introduced into the polyester resin are preferably regulated respectively to 0.1-0.5 and 0.1-0.7mmol/g. The number average mol.wt. of the polyester resin is preferably controlled to 1X10<4>-6X10<4>. The polyester resin can be combined with other thermoplastic resins, thermosetting resins, or reactive resins and used.

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. [Summary of the Invention] The present invention relates to a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support. By using a polyester resin that has a siloxane bond in the molecular chain and a quaternary ammonium salt as a polar group in the molecular side chain as the binder constituting the magnetic powder, the dispersibility of the magnetic powder and the surface properties of the magnetic layer can be improved. The objective is to improve the durability, running stability, magnetic properties, electromagnetic conversion properties, etc. of the resulting magnetic recording medium.

[Conventional technology]

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

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 binders such as nitrocellulose, polyester resin, polyurethane resin, vinyl chloride-vinyl acetate copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer. Can be mentioned.

However, with the increase in the specific surface area due to the finer particles of magnetic powder and the increase in cohesive force due to higher magnetic force, the above-mentioned binders cannot provide satisfactory dispersibility and surface properties, and the backing of the magnetic powder becomes difficult. Increasing the density has also become difficult.

Therefore, the durability, magnetic properties, and electromagnetic conversion properties 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 terms of mechanical strength and durability, such as falling off 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. 58-41565),
), -803M, -0803M, -COOM, -
P(OM)2 (where M is a hydrogen atom or an alkali metal)
Binder resin containing as a hydrophilic polar group (JP-A-59
-79427) etc. are known.

However, although the above-mentioned binders show some effect in improving dispersibility compared to conventional binders that do not have polar groups introduced, they do not work well with ultra-fine magnetic powders or magnetic powders with high magnetization. The performance for this cannot be said to be sufficient.

Furthermore, when the various binder resins mentioned above are used as binders for the magnetic layer, the resins themselves lack lubricity and have problems in running stability.

[Problem that the invention seeks to solve]

As described above, there is no known binder that exhibits sufficient dispersibility even for ultrafine magnetic powder. It was difficult to secure the characteristics and electromagnetic conversion characteristics.

Furthermore, since the binder resin itself lacks lubricity, there is a problem in running stability of the magnetic recording medium.

Therefore, the present invention was proposed in order to eliminate the above-mentioned drawbacks in the technical field, and it has been proposed to significantly improve the dispersibility of magnetic powder and the surface properties of the magnetic layer, and to provide excellent durability and running stability. [Means for Solving the Problems] As a result of intensive research, the present inventors have determined that the above-mentioned objectives cannot be achieved. It was discovered that a polyester resin that has a siloxane bond in its chain and a quaternary ammonium salt as a polar group in its molecular side chain shows a high affinity for magnetic powder, exhibits lubricity, and has excellent running stability. The present invention has been completed 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, in which the magnetic layer is included in molecular chains. It is characterized by containing as a binder a polyester resin having a siloxane bond and having a quaternary ammonium salt as a polar group in the molecular side chain.

The polyester resin containing a quaternary ammonium salt according to the present invention is obtained by polycondensing a carboxylic acid component, a polyhydric alcohol component, and a dicarboxylic acid component containing a quaternary ammonium salt. , aromatic dicarboxylic acids such as terephthalic acid, orthophthalic acid, orthophthalic acid, l,5-naphthalic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, p-oxybenzoic acid, Examples include aromatic oxycarboxylic acids such as p-(2-human Ooxyethoxy)benzoic acid, tricarboxylic acids and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid. Particularly preferred carboxylic acids include terephthalic acid, isophthalic acid,
Examples include adipic acid and sebacic acid.

The above-mentioned polyhydric alcohol components include ethylene glycol, propylene gellicol, 113-pClpanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2, 2. Aliphatic diols such as 4-1-dimethyl-1,3-bentanediol or substituted derivatives thereof, 1,4
- cycloaliphatic diols such as cyclohexane dimetatool;
Polyalkylene glycols such as diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A (7) ethylene oxide adduct or propylene oxide adduct, hydrogenated bisphenol A ethylene oxide adduct or propylene oxide Additives etc. can be listed. Furthermore, trimethylolethane, trimethylolpropane, glycerin,
Although triols or tetraols such as pentaerythritol can also be used, these polyhydric alcohols are preferably used in combination with diols.

Examples of the dicarboxylic acid component containing the quaternary ammonium salt include those shown below.

(However, R1, Rz, and R3 each represent an alkyl group having 1 to 6 carbon atoms, and X represents C1, Br, or engineering.) Furthermore, a siloxane bond is introduced into the molecular chain (main chain) of the polyester resin. However, as an introduction method, there is a method in which a compound having a siloxane bond is mixed into the starting material of the polyester resin. Specifically, a diol having a siloxane bond may be used as the compound having a siloxane bond, and may be mixed into a portion of the polyhydric alcohol component.

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 can be from 300 to 10,000.

The amount of polar groups introduced into the polyester resin according to the present invention is 0.
．． 01-1. Qmmol/gT! It is relatively strong, and more preferably in the range of 0.1 to 0.5 mmol/g. The amount of introduced polar group is 0.01 mmo+/'
! If it is less than i+, a sufficient effect on the dispersibility of the ferromagnetic powder will not be recognized. In addition, the amount of introduced polar groups is 1.0 m
If it exceeds mol/g, intermolecular or intramolecular aggregation tends to occur, which not only adversely affects dispersibility, but also causes selectivity to the solvent, which may make it impossible to use ordinary general-purpose solvents.

Further, the siloxane group concentration of the polyester resin according to the present invention is preferably 0.03 mmol/g to 3 mmol/g, 0.1 mmol/g to Q, 7 mmol
More preferably, it is l/, 9. If the siloxane group concentration is less than 0.03 mmol/g, lubricity cannot be imparted, and if the siloxane group concentration is less than 3 mmol/g,
If it exceeds ol/g, not only the solubility with the solvent and the compatibility with other binders will deteriorate, but also the physical properties such as the breaking strength and Young's modulus of the magnetic coating will deteriorate.

Further, the number average molecular weight of the polyester resin according to the present invention is 1
0000~100000. More preferably 1oooo~6
Preferably, it is in the range of 0000. If the number average molecular weight is less than 10,000, 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. There is.

The polyester resins according to the invention can be used in combination with other thermoplastics, thermosets or reactive resins.

The thermoplastic resin has a softening temperature of 150°C or less,
The average molecular weight is 10,000 to 200,000 and the degree of polymerization is approximately 2.
00 to 2000, such as vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic ester-acrylonitrile copolymers, thermoplastic polyurethane elastomers, Examples include synthetic rubber thermoplastic resins such as polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives, polyester resin, and polybutadiene. 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, Nido-O cellulose-melamine resins, mixtures of high molecular weight polyester resins and incyanate prepolymers, mixtures of methacrylate copolymers and diincyanate prepolymers, polyester polyols and polyincyanate prepolymers. Mixture of Nato, Urea Formaldehyde Resin, Low Molecular Weight Glycol/
Examples include mixtures of high molecular weight diols/triphenylmethane triisocyanate, 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, hexagonal barium ferrite particles, iron nitride, and the like.

As the above-mentioned ferromagnetic iron oxide particles, when expressed by the general formula FeOx, the value of X is in the range of 1.33≦X≦1.50, that is, maghemite (γ-FezO3°
0), Magne') (To(Fe5r4.
3) and their solid solutions (FeOx, 1.33 (
It is 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 includes CrO2, or Ru and Sn for the purpose of improving the coercive force thereof.

A material containing at least one of Te, sb, Fe, Ti, V, Mn, etc. can be used.

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

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

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

Mn-Bi, Mn-Aj, Fe-Go
-V, etc. can be used, and the purpose of improving various properties of these is AJ, Si, Ti, Cr, Mn,
Metal components such as Cu and Zn may also 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 (R, COOH) such as lyrinic acid and stearolic acid.

R is an alkyl or alkenyl group having 11 to 17 carbon atoms), an alkali metal of the aforementioned fatty acid (Ll);

(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-mentioned lubricants include dialkylpolysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 4 carbon atoms), 5 pieces,
Alkoxy has 1 to 4 carbon atoms), phenyl polysiloxane, fluoro alkyl polysiloxane (alkyl has 1 to 5 carbon atoms) (7) silicone oil, conductive fine powder such as graphite, molybdenum disulfide, disulfide Inorganic fine powder such as tungsten, polyethylene, polypropylene, polyethylene vinyl chloride copolymer, plastic fine powder 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, 20 carbon atoms), monobasic fatty acids 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 used are commonly used materials such as fused alumina, silicon carbide, chromium oxide (Crz03), corundum, artificial corundum, diamond, artificial diamond, Zaku0 stone, and enolly (main components: corundum and magnetite). be done. 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 added in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

Examples of the antistatic agent include conductive fine powder such as carbon black and carbon blank graft polymer, natural surfactants such as saponin, nonionic surfactants such as alkylene oxide type, glycerin type, and glycidol type, higher alkyl amines, Cationic surfactants such as quaternary ammonium salts, pyridine and other heterocycles, phosphoniums, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups; Ampholytic active agents such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, etc. 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, and the surfactant is added in an amount of 0.1 to 10 parts by weight.These surfactants may be added alone or in a mixture. Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids. Phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, but in particular dicyclohexylamine nitrite, cyclohexylamine chromate, diimpa pyramine nitride, jetanolamine 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, and this is coated on a non-magnetic support.The solvent for the magnetic paint is a ketone such as acetone, methyl ethyl ketone, methyl imbutyl ketone, or cyclohexanone. system, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate,
Ester types such as acetic acid glycol monoethyl ether, glycol ether types such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene, hexane,
Examples include aliphatic hydrocarbons such as heptane, chlorine hydrocarbons such as ethylene chloride, ethylene 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. Cellulose derivatives such as Nate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyimide,
In addition to plastics such as polyamide-imide, non-magnetic metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, ceramics such as glass, pottery and porcelain, paper, baryta, polyethylene, polypropylene, etc. , carbon number 2 such as ethylene-butene copolymer
Papers such as those coated or laminated with ~10 α-polyolefins can also be used. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, card, or drum.

[For production]

The action of the quaternary ammonium salt in the polyester resin greatly improves the 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 bonds have a lubricating effect, which provides good running properties.

Furthermore, polyester resins are soluble in general-purpose solvent systems, are easy to handle, and exhibit excellent coating film properties.

〔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 polyester resin containing a quaternary ammonium salt and a siloxane bond in the molecule was synthesized according to the synthesis method described above. Table 1 shows the properties of the synthesized resin.

Example I CO Deposition 1 - FezQ3. 100 parts by weight Vinyl chloride-vinyl acetate copolymer 10 (U, C, C
J, VAGH) Polyester resin (Resin A) 15/' Dispersant (Lecithin) 0.5'' Lubricant (
Silicone oil) 1 Abrasive (CrzO
3) 2 ``Methyl ethyl ketone 100 ``Methyl isobutyl ketone 50 〃Toluene
50 The above composition was mixed in a ball mill for 48 hours, filtered through a 3 μm filter, 2.5 parts by weight of a hardening agent (Desmodur L manufactured by Bayer AG) was added, and mixed for an additional 30 minutes. It was coated onto a polyethylene terephthalate film so that the thickness after drying would be 6 μm, subjected to magnetic field orientation treatment, dried, and rolled up. 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 except that polyester resin (Resin B) was used in place of the polyester 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 polyester resin (Resin C) was used in place of the polyester resin (Resin A) in the composition of Example 1.

Example 4 In the composition of Example 1, polyester resin (resin D) was used instead of polyester resin (resin A), and Example 1
A sample tape was prepared in the same manner as above.

Example 5 A sample tape was prepared in the same manner as in Example 1 except that polyester resin (Resin E) was used in place of the polyester 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 polyester resin (Resin F) was used in place of the polyester 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 polyester resin (Resin G) was used instead of polyester 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 polyester resin (Resin H) instead of the polyester resin (Resin A) in the composition of Example 1. A sample tape was prepared in the same manner as in Example 1, using a polyester resin (resin technology) instead of the polyester resin (resin A) in the composition.

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 kinetic friction is calculated at a low tape speed (o, 4mi/5
It was measured as the friction coefficient (load: 50 g) between the magnetic layer surface and IS stainless steel in ec). The surface gloss was determined by measuring the reflectance at an incident angle of 75° and a reflection angle of 75° using a gloss meter. 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 winding the sample tape onto a reel at a temperature of 40°C.
Immediately after being left under conditions of humidity 8096 for 24 hours, the degree of peeling of the sample tape was visually evaluated and scored on a 10-point scale, with the better the adhesive properties, the lower the score. Still characteristics were measured by recording a 4°2 MHz video signal on a sample tape and measuring the time until the playback output attenuated to 5096 pixels.

As is clear from the results in Table 2, by using a polyester resin containing a siloxane bond and a quaternary ammonium salt as a binder for the magnetic layer, the coefficient of dynamic friction, surface gloss, and amount of powder falling are improved. , adhesive properties and still properties are significantly improved. Therefore, the thermal properties, running properties, blocking resistance, durability, dispersibility of magnetic powder, etc. of the magnetic recording medium are significantly improved.

〔Effect of the invention〕

As is clear from the above explanation, since it is used as a binder for the magnetic layer in the present invention, it has a high affinity for magnetic powder, and even if ultrafine magnetic powder or magnetic powder with a large amount of magnetization is used. 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 imparted by containing a siloxane bond reduces the coefficient of friction, and in terms of runnability, it is soluble in general-purpose solvents and easy to handle, which is advantageous in terms of productivity and workability.

Claims (1)

[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 siloxane bonds in its molecular chains, and A magnetic recording medium comprising a polyester resin having a quaternary ammonium salt as a polar group in a side chain as a binder.