JPH09282634A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease clogging of a magnetic head after treatment by substantially covering an abrasive with a binder in a magnetic recording medium having a magnetic recording layer containing magnetic particles, a nonmagnetic abrasive and a binder on a base body. SOLUTION: This magnetic recording medium contains at least magnetic particles, a nonmagnetic abrasive and a binder on the base body. In the magnetic recording medium, the abrasive is substantially covered with a binder. As for the magnetic recording medium, it is preferable to prepare a dispersion of the abrasive by kneading the abrasive with the binder under condition of dispersion viscosity between >=10×10<4> cp and <=1×10<7> cp. The kneading and dispersing process is preferably carried out in a pressurizing type kneader.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium in which clogging of a magnetic head is prevented and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium reads and writes information with a magnetic head. In order to quickly and accurately input and output information, the magnetic recording medium and the magnetic head must always be in an optimal environment. . However, due to the contact between the surface of the magnetic recording medium, in which the magnetic particles mainly composed of iron oxide are dispersed in the synthetic polymer binder, and the magnetic head, which is a metal, dust, dust, In some cases, dust or components of the magnetic recording medium adhere and cause clogging, which may hinder information input / output.

[0003] These problems are almost completely eliminated by cleaning the magnetic head.
Even if it is effective against dust, dust, and dust, it is not perfect against the adhesion of components of the magnetic recording medium. Further, the preparation of the cleaning member and the trouble of the cleaning still exist.

In recent years, silver halide color photographic materials (hereinafter simply referred to as photographic materials) have been used for photographing (image exposure).
There has been a proposal to record information such as photographing conditions on a silver halide color photosensitive material for effective use in order to more efficiently perform later development processing and printing on photographic paper with high accuracy.

US Pat. No. 4,947,196 and WO 90/04254 disclose a roll-shaped film and a magnetic head having a magnetic layer containing magnetic particles for magnetic recording on the back surface of a photographic film. An imaging camera having the same is disclosed. According to the above-described improved technology, the identification information of the type and maker of the photosensitive material, information on the conditions at the time of photographing, information on the customer, information on the printing conditions, information on the conditions for additional printing, etc. are recorded on the magnetic layer on the film. By magnetically inputting / outputting the data, it is possible to improve the print quality, increase the efficiency of the printing operation, increase the efficiency of the lab work, and the like.

That is, it can be said that the magnetic recording medium is provided on one side of the support, and the photographic constituent layer is provided on the other side of the support to provide an epoch-making recording medium having both magnetic information and optical image information.

However, the problem of clogging of the magnetic head still exists, and a new clogging factor relating to the photographic constituent layer and its developing process is added. It is difficult to cope with the conventional cleaning means alone, and there is a need for fundamental improvement of the magnetic recording medium itself.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
In order to reduce the clogging of the magnetic head after the treatment, the head cleaning property is imparted to the magnetic head. A second object is to provide a magnetic recording medium with less head contamination. Thirdly, it is to prevent deterioration of magnetic properties and optical properties due to aggregation of abrasive particles. The fourth object is to provide a recording medium having an excellent magnetic coating film strength that can withstand repeated use of the head.

[0009]

The above object of the present invention is achieved by the following constitution.

(1) In a magnetic recording medium having a magnetic recording layer containing at least magnetic particles, a non-magnetic abrasive and a binder on a support, the abrasive is substantially covered with the binder. Characteristic magnetic recording medium.

(2) Dispersion viscosity 1 with abrasive and binder
A method for producing a magnetic recording medium, comprising: kneading and dispersing at a level of from 100,000 cp to 100 million cp to obtain a dispersion of an abrasive.

(3) The method for producing a magnetic recording medium according to (2), wherein the kneading dispersion is a pressure kneader kneading dispersion.

(4) The method for producing a magnetic recording medium according to (2) or (3), wherein the binder is a cellulose ester having a weight average molecular weight of 20,000 to 300,000.

(5) A method for producing a magnetic recording medium, characterized in that a coating liquid for a magnetic recording layer is prepared by dispersing a polishing agent in a low molecular weight binder and then adding a magnetic particle dispersion and a high molecular weight binder. .

Hereinafter, the present invention will be described in detail.

As used in the present invention, the phrase "the abrasive is substantially covered with the binder" means the following.

When the abrasive is substantially coated,
No liquid separation phenomenon occurs at the paint stage.

When the abrasive is uniformly dispersed in a solution containing a solvent and a binder, if the dispersion is left to stand, the color of the abrasive particles will bleed on the surface of the dispersion.
Liquid separation phenomenon occurs. This is because the difference between the specific gravity of the abrasive particles and the specific gravity of the binder solution causes the abrasive particles that should settle or be suspended in the paint to have air bubbles on the surface without being covered with the binder or solvent, or the primary particles. The apparent specific gravity of the particles is reduced due to the presence of air bubbles in the gaps of the aggregates, and when the standing time after dispersion is long, they are separated into the liquid surface,
It is believed that.

After the magnetic recording layer is formed on the support and the surface is rubbed with a metal plate or the like, the filler in the coating film is released and the surface layer is scraped. At this time, when the desorbed filler particles and the binder used for dispersion are detected at a constant ratio, the particle surface is analyzed by various instrumental analytical methods, and the binder component is detected as an organic substance. In this case, it can be considered that the surface of the particles is substantially covered with the binder. On the contrary, when only inorganic abrasive particles are detected, it is considered that the abrasive is not covered with the binder even in the coating film.

It is also possible to optically know the coating state of the abrasive particles with the binder. If the abrasive particles are agglomerated or have poor wettability with the binder, and a thin layer of air is present on the surface of the particles, the transparency of the coating film will deteriorate and light will be scattered. The degree deteriorates.

As the binder for dispersing the abrasive, a thermoplastic resin, a radiation curable resin, a thermosetting resin and other reactive resins can be used alone or in combination.

The same thermoplastic resin as used for the magnetic recording layer can be used as the thermoplastic resin. Further, those which are different from the main binder of the magnetic recording layer but which are mixed with each other can be used in the present invention without any trouble.
Further, even binders that do not mix with each other (have no compatibility) can be widely used as long as they are formed on the support and do not deviate from the object of the present invention.

The thermoplastic resin is preferably a cellulose derivative such as cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose triacetate or nitrocellulose, or a polyurethane resin such as polyester polyurethane, polycarbonate polyurethane or polyether polyurethane. Is preferred.

The above-mentioned thermoplastic resin has a Tg of -40 to 18
It is preferably 0 ° C., preferably 30 to 150 ° C., the weight average molecular weight is 5,000 to 350,000, and more preferably the weight average molecular weight is 10,000.
˜300,000, more preferably 20,000 to 250,000 in weight average molecular weight.

The binders listed above may have a polar group in the molecule. The polar group includes an epoxy group, -COOM, -OH, -N (R) ₂ , -N (R).
_{3 X, -SO 3 M, -OSO} 3 M, -PO 3 M 2, -OPO 3
M (M is a hydrogen atom, an alkali metal or ammonium, X is an acid forming an amine salt, and R is a hydrogen atom or an alkyl group, respectively).

As the above binder, EASTMA
N CHEMICAL CO. CA394-60 made
S, CA398-3, CA398-6, CA398-3
0, CAB381-0.1, CAB381-2, CAB
381-20, CAP482-0.5, CAP482-
20, EAB-171, EAB-272, EAB-38
1, EAB-500, or L-A manufactured by Daicel Corporation
C, V-AC, Y-AC, acetate flocs, roselle flakes manufactured by Teijin Ltd., or Courtau
ld Co. Cellulose derivatives such as LM-204 and LM-45 manufactured by Toyobo Co., Ltd. and Byron NK-7 manufactured by Toyobo Co., Ltd.
Examples thereof include Byron UR8200, Byron UR8700, Byron 200, Byron 400, Byron 600, and polyurethane resins such as N3132 manufactured by Nippon Polyurethane Industry Co., Ltd.

The high molecular weight binder and the low molecular weight binder of the present invention mean a high molecular weight binder having a large weight average molecular weight when binders having different weight average amounts are contained in the coating liquid for the magnetic recording layer. The one having a small weight average molecular weight means a low molecular weight binder.

In the present invention, the thickness of the magnetic layer is 0.0
1 to 20 μm is preferable, 0.05 to 15 μm is more preferable, and 0.1 to 10 μm is further preferable.

The coating liquid for forming the magnetic recording layer contains a lubricant and an antistatic agent in order to impart functions to the magnetic recording layer such as imparting lubricity, preventing electrification, preventing adhesion, and improving friction and abrasion characteristics. Various additives such as agents can be added. Further, in addition to the coating liquid, for example, a plasticizer may be added to give flexibility to the magnetic recording layer, and a dispersant may be added to help the dispersion of the magnetic substance in the coating liquid. Imparting the above lubricity,
Functions such as antistatic, antiadhesion, improvement of friction and abrasion characteristics, and prevention of clogging of the magnetic head may be provided by providing these functional layers separately from the magnetic recording layer.

For example, when the magnetic recording layer of the present invention is provided on the antistatic layer, it is possible to form a uniform thin film due to its good film forming property. Thus, good antistatic property can be obtained. If necessary, a protective layer adjacent to the magnetic recording layer may be provided to improve the scratch resistance. In the case where the magnetic recording layer is provided in a stripe shape, a transparent polymer layer containing no magnetic substance may be provided thereon to eliminate a step due to the magnetic recording layer. In this case, the transparent polymer layer may have the various functions described above. Since the binder system of the present invention is excellent in film forming property and strength, it can be dispersed in combination with not only the magnetic powder but also the above various additives, which is advantageous in production.

After providing the magnetic recording layer, calendering is performed on this layer to improve smoothness, and S of magnetic output is obtained.
It is also possible to improve the / N ratio. In this case, it is preferable to apply the silver halide photographic constituent layer after performing the calendering treatment.

The ferromagnetic fine powder used in the magnetic recording layer of the present invention includes ferromagnetic iron oxide fine powder, Co-doped ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, ferromagnetic metal powder, and ferromagnetic metal. Alloy powder, barium ferrite, etc. can be used.

The ferromagnetic powder used in the present invention can be manufactured by a known method.

The shape may be any of needle-like shape, rice grain-like shape, spherical shape, cubic shape, plate shape and the like, but needle shape and plate shape are preferable in terms of electromagnetic conversion characteristics. The crystallite size and non-surface area are not particularly limited, but the crystallite size is 400 Å or less, and the BET value is 20 m.
^It is preferably at least ² / g, particularly preferably at least 30 m ² / g. The pH and surface treatment of the ferromagnetic powder can be used without particular limitation. The preferred pH range is 5-10. In the case of a ferromagnetic iron oxide fine powder, it can be used without any particular limitation on the ratio of divalent iron / trivalent iron. These magnetic recording layers are disclosed in JP-A-47-32812 and JP-A-47-32812.
-109604.

In the case of the present invention, the preferred amount of magnetic powder used is
The amount is preferably 4 × 10 ⁻⁴ g or more per m ^{2 of} magnetic recording medium.
If it is less than this, the input / output of the magnetic recording is hindered.
The upper limit is not particularly limited as long as the optical density of light having a wavelength of 436 nm is 1.5 or less, but the limit is about 4 g per 1 m ² .

To form an optically transparent magnetic recording layer, the binder is 1 to 2 with respect to 1 part by weight of the magnetic powder.
It is preferable to use 00 parts by weight. More preferably, the amount is 2 to 50 parts by weight based on 1 part by weight of the magnetic substance powder. Also,
The solvent is used in such an amount that the coating can be easily performed.

As a method for providing the magnetic recording layer on the support, an extrusion coater, an air doctor coat, a blade coat, an air knife coat, a squeeze coat, an impregnation coat, a reverse roll coat, a transfer roll coat, a gravure coat, a kiss coat. , Cast coat, spray coat, etc. can be used. In order to perform multiple stripe coating, these coating heads may be formed in multiples. Specific stripe coating methods include, for example, JP-A-48-25503 and 48-255.
No. 04, No. 48-98803, No. 50-13.
No. 8037, No. 52-15533, No. 51-
No. 3208, No. 51-6239, No. 51-6
No. 5606, No. 51-140703, Japanese Patent Publication No. 29-4221, and U.S. Pat. No. 3,062,181.
The description in Japanese Patent No. 3,227,165 can be referred to.

In order to firmly adhere the magnetic recording layer to the support, the support may be provided with an undercoat layer, and the support may be subjected to chemical treatment, mechanical treatment, corona discharge treatment, flame treatment, ultraviolet treatment. Surface treatment such as high frequency treatment, glow discharge treatment, active plasma treatment, laser treatment, concentrated acid treatment, ozone oxidation treatment, etc. may be performed. Furthermore, an undercoat layer may be provided after the surface activation treatment.

The undercoat layer is preferably an aqueous latex type.

The binder that can be used in the magnetic recording layer and the binder that is used in the undercoat layer are thermoplastic resins, radiation curable resins, thermosetting resins, and other reactive resins, which are dissolved or dispersed in an organic solvent or water. These can be used alone or as a mixture.

As the above-mentioned thermoplastic resin, vinyl chloride-
Vinyl acetate copolymer, vinyl chloride resin, vinyl acetate resin, copolymer of vinyl acetate and vinyl alcohol, partially hydrolyzed vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile Vinyl-based polymers or copolymers such as copolymers, ethylene-vinyl alcohol copolymers, chlorinated polyvinyl chloride, ethylene-vinyl chloride copolymers, ethylene-vinyl acetate copolymers, nitrocellulose, cellulose acetate Cellulose derivatives such as pionate and cellulose acetate butyrate resin, maleic acid and / or acrylic acid copolymer, acrylate copolymer, acrylonitrile-styrene copolymer, chlorinated polyethylene, acrylonitrile-chlorinated polyethylene-styrene Copolymer, methyl meta Relate-butadiene-styrene copolymer, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin, amino resin, styrene-butadiene resin And a rubber-based resin such as butadiene-acrylonitrile resin, a silicone-based resin, and a fluorine-based resin.

The thermoplastic resin has a glass transition temperature Tg.
Is preferably -40 ° C to 180 ° C, more preferably -3.
It is from 0 to 150 ° C, and the weight average molecular weight is 5,
Those having a weight average molecular weight of 10,000 to 200,000 are more preferable.
00. The magnetic magnetic layer of the present invention has a Tg of 50.
It is also possible to use a substance having a temperature of 30 ° C. or higher and a substance having a temperature of 30 ° C. or lower in combination.

The glass transition temperature Tg is described in detail in Shin Experimental Chemistry Course 19 (Polymer Chemistry II) Maruzen.

These can also be used as an aqueous emulsion or an aqueous colloidal solution. The particle size of these synthetic resin emulsions may be 5 nm to 10 μm.

The radiation-curable resin is a resin which is cured by radiation such as electron beam and ultraviolet rays, and examples thereof include maleic anhydride type, urethane acryl type, ether acryl type and epoxy acryl type.

Examples of thermosetting resins and other reactive resins include phenolic resins, epoxy resins, polyurethane-based curable resins, urea resins, alkyd resins, and silicone-based curable resins.

The binders listed above may have polar groups in their molecules. As the polar group, an epoxy group, -C
_{OOM, -OH, -NR 2, -NR} 3 X, -SO 3 M, -
OSO ₃ M, —PO ₃ M ₂ , and —OPO ₃ M (M and M ₂ each represent a hydrogen atom, an alkali metal atom, or ammonium;
Represents an acid that forms an amine salt, and R ₂ and R ₃ represent a hydrogen atom and an alkyl group, respectively. ).

Other hydrophilic binders that can be used in the present invention include, for example, Research Disclosure No. No. 17643, page 26, and the same No. 18716,
Examples thereof include water-soluble polymers, cellulose ethers, latex polymers, and water-soluble polyesters described on page 651.

Examples of the water-soluble polymer include gelatin, gelatin derivatives, casein, agar, sodium alginate, starch, polyvinyl alcohol, acrylic acid-based copolymers, maleic anhydride-based copolymers, etc. in addition to the above-mentioned celluloses. Examples of ethers include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and the like.

When using a water-soluble polymer, it is preferable to use a hardener. Hardening agents that can be used include aldehyde compounds, ketone compounds, compounds having reactive halogens, compounds having reactive olefins, N-methylol compounds, aziridine compounds, acid derivatives, and epoxy compounds. , Halogen carboxaldehydes, chromium ban, zirconium sulfate, carboxyl group activated hardener and the like. The hardener is
Usually, it is used in an amount of 0.01 to 60% by weight, preferably 0.05 to 50% by weight, based on the solid content of the resin.

Lubricants that can be used in the magnetic recording layer of the present invention include silicone oils such as polysiloxane, fine plastic powders such as polyethylene and polytetrafluoroethylene, higher fatty acids, higher fatty acid esters, paraffin wax, and fluorocarbons. To be Specifically, these can be used alone or as a mixture.
The amount of these additives is 0.5 to 100 parts by weight of the dried coating film.
It can be used in the range of up to 20 parts by weight. Those that can be dissolved or diffused in water are preferred.

The abrasives usable in the magnetic recording layer of the present invention include non-magnetic inorganic powders having a Mohs hardness of 5 or more, preferably 6 or more. Specifically, aluminum oxide (α-alumina, γ -Alumina, corundum, etc.), chromium oxide (Cr ₂ O ₃ ), iron oxide (α-Fe ₂ O ₃ ), oxides such as silicon dioxide and titanium dioxide, carbides such as silicon carbide and titanium carbide, and fine particles such as diamond. A powder can be mentioned. The average particle size of these is preferably 0.01 to 2.0 μm, and can be added in the range of 0.5 to 300 parts by weight with respect to 100 parts of the magnetic powder.

As the antistatic agent contained in the magnetic recording layer of the present invention, fine particles of metal oxide are preferable. Examples are oxygen-rich oxides such as Nb ₂ O _{5 + X} , Rh
O _2-X, oxygen deficiency oxides such as Ir ₂ O _3-X, or Ni
Non-stoichiometric hydrides such as (OH) _X , HfO ₂ , Th
O ₂ , ZrO ₂ , CeO ₂ , ZnO, TiO ₂ , SnO ₂ ,
Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, Mo
O ₂ , V ₂ O _{5 and the} like, or a composite oxide thereof are preferable, and ZnO, TiO ₂ and SnO ₂ are particularly preferable. As an example including a hetero atom, for example, Al, I
n or the like, Nb, Ta or the like for TiO ₂ ,
Addition of Sb, Nb, a halogen element or the like is effective for SnO ₂ . The addition amount of these hetero atoms is 0.01
mol% to 25 mol% is preferable, but 0.1 m
The range of ol% to 15 mol% is particularly preferred.

The volume resistivity of these electrically conductive metal oxide powders is 10 ⁷ Ωcm or less, and particularly 10 ⁵ Ωcm.
The following is preferred. Further, a sol in which fine particles of the metal oxide are mixed in an aqueous solution may be used.

In addition to these, conductive fine powders such as carbon black and carbon black graft polymers, nonionic surfactants such as alkylene oxides, glycerins and glycidols; higher alkyl amines, quaternary ammonium salts, pyridine and the like. Heterocyclic compound salts,
Cationic surfactants such as phosphoniums or sulfoniums; anionic surfactants containing acidic groups such as carboxylate, phosphorus, sulfate group, phosphate group; amino acid, aminosulfonic acid, sulfuric acid of amino alcohol or And amphoteric surfactants such as phosphate esters.

Since the binder system of the present invention is also excellent in the dispersibility of these antistatic agents, good conductivity can be imparted to the magnetic recording layer.

The surfactant may be contained as a substituent of the polymer.

As the solvent used in the dispersion, kneading and coating of the present invention, a ketone system such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone and tetrahydrofuran in any ratio; methanol, ethanol, propanol, butanol, Alcohol-based compounds such as isobutyl alcohol, isopropyl alcohol, and methylcyclohexanol; ester-based compounds such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol monoethyl ether acetate; ether, glycol dimethyl ether, glycol monoethyl Glycol ether type such as ether and dioxane; Tar type (aromatic hydrocarbon) such as benzene, toluene, xylene, cresol, chlorobenzene and styrene Methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, chlorinated hydrocarbons such as dichlorobenzene,
N, N-dimethylformaldehyde, hexane, water, etc. can be used.

In the present invention, various supports can be used. Examples of the support that can be used include polyester films such as polyethylene terephthalate and polyethylene naphthalate, cellulose triacetate films, cellulose diacetate films, polycarbonate films, polystyrene films, and polyolefin films.

The polyester support is not particularly limited, but aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid and ethylene glycol, 1,3-propanediol, 1,4-butanediol, etc. Examples thereof include condensation polymers with alkylene glycols such as polyethylene terephthalate, polyethylene-2,6-dinaphthalate, polypropylene terephthalate, polybutylene terephthalate, and copolymers thereof.

In particular, from the curl and curl recovery after the development processing, JP-A-1-244446, 1-291248, 1-298350, 2-89045, and 2-93641, JP-A-2-181949, JP-A-2-214852, and JP-A-2-2911.
It is preferable to use a polyester having a high water content as shown in JP-A-35-35.

These polyesters may have polar groups and other substituents.

In the present invention, the support is preferably polyethylene terephthalate or polyethylene naphthalate.

The above polyester is preferably stretched in an area ratio of 4 to 16 times in order to satisfy the mechanical strength and dimensional stability of the film support. Further, it is preferable to carry out a heat treatment (annealing treatment) as described in JP-A-51-16358 after the film formation.

For the support, a matting agent, an antistatic agent, a lubricant,
Surfactants, stabilizers, dispersants, plasticizers, UV absorbers,
Conductive substances, tackifiers, softening agents, fluidity imparting agents, thickeners, antioxidants and the like can be added.

The support is used for the purpose of neutralizing the tint of the minimum density portion, preventing the light piping phenomenon (edge fogging) that occurs when light enters the film coated with the photographic constituent layer from the edge, and preventing halation. Dyes can be included.

The type of dye is not particularly limited, but when a polyester film is used as the support, it is preferable that it has excellent heat resistance in the film forming process, and examples thereof include anthraquinone chemical dyes. As for the color tone, when the purpose is to prevent light piping, gray dyeing is preferable as seen in general photosensitive materials. The dyes may be used alone or in combination of two or more. Mitsubishi Kasei Co., Ltd. Diaresin, Bayer
It is possible to achieve the target by using a dye such as MACROEX manufactured by the company alone or by appropriately mixing them.

Examples of the abrasive include non-magnetic inorganic powders having a Mohs hardness of 5 or more, preferably 6 or more. Specifically, aluminum oxide (α-alumina, γ-alumina,
Corundum, etc., chromium oxide (Cr ₂ O ₃ ), iron oxide (α-Fe ₂ O ₃ ), oxides such as silicon dioxide and titanium dioxide, carbides such as silicon carbide and titanium carbide, and fine powders such as diamond. be able to.

The average particle size of these is 0.001 to 1.2.
μm is preferable, and it is 1 with respect to 100 parts by weight of magnetic powder.
It can be added in the range of up to 800 parts by weight. The surface of the abrasive may be treated with an organic substance or an inorganic substance. Further, abrasives having different particle size distributions or abrasives of different types may be used together.

A photographic constituent layer can be provided on the side of the magnetic recording medium of the present invention opposite to the magnetic recording layer. As the photographic constituent layer, a known technique in the art can be used.

In the present invention, the silver halide emulsion is Research Disclosure No. 308119 (hereinafter R
D308119).

The locations of description are shown below.

[Item] [Page of RD308119] Iodine composition 993 I-A manufacturing method 993 I-A and 994 E crystal wall Normal crystal 993 I-A twin 993 I-A epitaxial 993 I -A term halogen composition uniform 993 IB term non-uniform 993 IB term halogen conversion 994 IC term halogen substitution 994 IC term metal containing 994 ID category monodispersed 995 IF category solvent addition 995 I-F item Latent image forming position Surface 995 I-G item Internal 995 I-G item Applicable photosensitive material negative 995 I-H item Positive (including internal fog particles) 995 I-H item Emulsion mixed 995 I Item J Desalination 995 Item II-A In the present invention, the silver halide emulsion used is one that has been subjected to physical ripening, scientific ripening and spectral sensitization. Additives used in such a process are described in Research Disclosure No. 17643, no. 18716 and no. 308
119 (hereinafter RD17643 and RD1871 respectively)
6 and RD308119).

The locations of description are shown below.

[0075]

[Table 1]

Known photographic additives that can be used in the present invention are also described in the above-mentioned Research Disclosure.

The relevant description is shown below.

[0078]

[Table 2]

Various couplers can be added to the present invention and specific examples thereof are described in the above-mentioned Research Disclosure.

The relevant description locations are shown below.

[0081]

[Table 3]

The additive used in the present invention is RD3081.
It can be added by the dispersion method described in 19XIV.

In the present invention, the above-mentioned RD17643 is used.
Page 28, RD18716 pages 647 to 648, and RD3
The supports described in 08IX XIX can be used.

The photographic constituent layers used in the present invention may be provided with auxiliary layers such as a filter layer and an intermediate layer described in the above-mentioned item RD308119VII-K.

The photographic constituent layers used in the present invention are the above-mentioned R
Various layer configurations such as a normal layer, a reverse layer, and a unit configuration described in D308119VII-K can be employed.

Development processing of the photographic constituent layers used in the present invention is carried out by, for example, T.W. H. James, Theory of the Photographic Process 4th Edition (The
Theory of The Photographic
Process Forth Edition) 2
Pages 91-334 and Journal of the American Chemical Society (Journal of the American Chemical Society)
the American Chemical Soc
iey) Developers known per se described in Vol. 73, page 3, 100 (1951) can be used. Further, the color photographic constituent layer is the same as that of the aforementioned RD1764.
3 pages 28-29, RD18716 page 615 and RD
Development processing can be carried out by the usual method described in 308119 XIX.

[0087]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited thereto.

Example 1 Preparation of Magnetic Recording Medium << Preparation of Support >> 100 parts by weight of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by weight of ethylene glycol were mixed with 0.1 part by weight of calcium acetate hydrate as an ester exchange catalyst. After the addition, a transesterification reaction was carried out according to a conventional method.
To the obtained product, 0.05 parts by weight of antimony trioxide,
0.03 parts by weight of trimethyl phosphate was added.
Then gradually raise the temperature and reduce the pressure to 290 ° C, 0.05 mm
Polymerization was performed under the conditions of Hg to obtain polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.60.

This was vacuum-dried at 150 ° C. for 8 hours, melt-extruded in a layer form from a T-die at 300 ° C., adhered to a cooling drum at 50 ° C. while applying static electricity, cooled and solidified, and an unstretched sheet was obtained. Obtained. This unstretched sheet was stretched 3.3 times in the machine direction at 135 ° C. using a roll-type longitudinal stretching machine.

The obtained uniaxially stretched film was stretched in a first stretching zone at 145 ° C. by 50% of the total transverse stretching ratio using a tenter type transverse stretching machine, and further at a second stretching zone at 155 ° C. at a total transverse stretching ratio of 3. The film was stretched three times. Then 10
Heat treated at 0 ° C for 2 seconds, and further heat-fixed zone 200 ° C
For 5 seconds and a second heat setting zone at 240 ° C. for 15 seconds. Next, the film was gradually cooled to room temperature over 30 seconds while performing a 5% relaxation treatment in the lateral direction to obtain a polyethylene naphthalate film having a thickness of 85 μm.

This is wound around a stainless steel core, and
A heat treatment (annealing treatment) was performed at 10 ° C. for 48 hours to form a support.

12 W / m ² / min on both sides of the support
On one side, the following undercoating coating solution B
-1 is applied so as to have a dry film thickness of 0.4 μm, and a corona discharge treatment of 12 W / m ² / min is applied thereon, so that the undercoating coating solution B-2 described below has a dry film thickness of 0.06 μm. Was applied.

On the other surface subjected to the corona discharge treatment of 12 W / m ² / min, the undercoating coating solution B-3 shown below was applied so as to have a dry film thickness of 0.2 μm, and 12 W / m was applied thereon. ²
/ Min, and a coating liquid B-4 shown below was applied to a dry film thickness of 0.2 μm.

Each of the layers was dried at 90 ° C. for 10 seconds after coating, and after the four layers were coated, heat-treated at 110 ° C. for 2 minutes and then cooled at 50 ° C. for 30 seconds.

<Undercoat Coating Solution B-1> A copolymer latex liquid of 30% by weight of butyl acrylate, 20% by weight of t-butyl acrylate, 25% by weight of styrene and 25% by weight of 2-hydroxyethyl acrylate (solid content: 30% 125 g Compound (UL-1) 0.4 g Hexamethylene-1,6-bis (ethylene urea) 0.05 g Finish with water 1000 ml <Subbing coating solution B-2> Hydroxidation of styrene-maleic anhydride copolymer Sodium aqueous solution (solid content 6%) 50 g Compound (UL-1) 0.6 g Compound (UL-2) 0.09 g Silica particles (average particle size 3 μ) 0.2 g Finish with water 1000 ml <Coating solution B-3> Butyl 30% by weight of acrylate, 20% by weight of t-butyl acrylate, 25% by weight of styrene and 25 of 2-hydroxyacrylate % By weight of copolymer latex liquid (solid content 30%) 50 g Compound (UL-1) 0.3 g Hexamethylene-1,6-bis (ethylene urea) 1.1 g Finish with water 1000 ml

[0096]

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<Coating Solution B-4> 60 mol% of dimethyl terephthalate, 30 mol% of dimethyl isophthalate, 10 mol% of a sodium salt of dimethyl 5-sulfoisophthalate, 50 mol% of ethylene glycol as a glycol component, 50 mol% of diethylene glycol was copolymerized by a conventional method. The copolymer was stirred in hot water at 95 ° C. for 3 hours to obtain a 15% by weight aqueous dispersion A.

Aqueous dispersion of tin oxide-antimony oxide composite fine particles (average particle size 0.2 μ) (solid content 40% by weight) 109 g Aqueous dispersion A 67 g Finish with water 1000 ml << Coating of magnetic recording layer >> Undercoat layer B- of the treated support
4 On the layer coated with the coating liquid, a magnetic recording layer coating liquid having the following composition was coated using a precision extrusion coater as shown in Table 12 to a dry film thickness of 0.8 μm, and dried. At the same time, while the coating film was not dried, the magnetic material was oriented in the coating direction in the orientation magnetic field to increase the output during magnetic recording and reproduction.

A. Preparation of Magnetic Recording Layer Coating Solution 1 Preparation of Abrasive Dispersion 1 Abrasive, binder, and abrasive kneaded material 1 (described in Table 4)
The solvent was put into a pressure kneader kneader and kneaded under pressure for 3 hours to prepare a kneaded abrasive 1. The binder and the solvent of the abrasive dispersion 1 (described in Table 5) were added to the abrasive kneaded material 1, and the mixture was dispersed for 3 hours with a sand grinder to prepare a uniform abrasive dispersion 1.

[0100]

[Table 4]

[0101]

[Table 5]

2. Preparation of Magnetic Powder Dispersion 1 Magnetic powder, binder of magnetic powder dispersion 1 (described in Table 6),
The solvent was charged into a sand grinder and dispersed for 4 hours to prepare a uniform magnetic powder dispersion 1.

[0103]

[Table 6]

3. Preparation of Magnetic Recording Layer Coating Liquid 1 As described in Table 7, a binder is added to the solvent of the magnetic recording layer coating liquid 1 (described in Table 7) and stirred with a dissolver to prepare a binder solution. As shown in Table 7, the magnetic powder dispersion 1 and the abrasive dispersion 1 were added thereto, dispersed with a sand grinder for 1 hour, the curing agent was added, and the mixture was sufficiently stirred and mixed to prepare the magnetic recording layer coating solution 1. Obtained.

[0105]

[Table 7]

B. Preparation of coating solutions 2 to 15 for magnetic recording layer 1-1. Preparation of Abrasive Dispersions 2 to 13 Abrasive Kneaded Product 1 was changed as shown in Table 8 to prepare Abrasive Kneaded Products 2 to 13 in the same manner.
/ A, NV, a binder and a solvent were added to prepare abrasive dispersions 2 to 13.

[0107]

[Table 8]

1-2. Preparation of Abrasive Dispersion 14 Abrasive, binder and solvent of Abrasive Dispersion 14 (described in Table 9) were put into a sand grinder and dispersed for 4 hours to prepare Abrasive Dispersion 14.

[0109]

[Table 9]

[0110] 2. Preparation of Magnetic Powder Dispersion 2 Magnetic powder kneaded product 1 ′ (shown in Table 10), a magnetic powder, a binder, and a solvent were charged into a pressure kneader kneader, and pressure kneaded for 3 hours to obtain magnetic powder kneaded product 1 ′. It was made. A binder and a solvent of the magnetic powder dispersion 2 (shown in Table 11) were added to the magnetic powder kneaded material 1 ', and the mixture was dispersed for 3 hours with a sand grinder to prepare a uniform magnetic powder dispersion 2.

[0111]

[Table 10]

[0112]

[Table 11]

3. Preparation of Magnetic Recording Layer Coating Liquids 2 to 15 Abrasive Dispersion No. And magnetic powder dispersion No. Magnetic recording layer coating liquids 2 to 15 were obtained in exactly the same manner as the magnetic recording layer coating liquid 1 except that and were changed as shown in Table 12.

[0114]

[Table 12]

Note: The abrasive particle dispersion after kneading in which abrasive particles AKP-50 is kneaded as described in JP-A-7-296368 of the EK patent is agglomerated in a methylene chloride solution of cellulose triacetate, and is determined by the present invention. The abrasive particles can be coated only by kneading in the presence of a binder, not at the level, whereby the agglomeration of the abrasive particles can be prevented.

On the side opposite to the magnetic recording layer side of the magnetic recording medium, there is provided an undercoat layer obtained by applying the undercoat coating solutions B-1 and B-2 under the same conditions. Samples 101-115 were obtained by providing a photographic constituent layer of the composition. The addition amount is expressed in grams per 1 m ^2. However, silver halide and colloidal silver are converted into the amount of silver, and an increased dye (indicated by SD)
Is expressed as the number of moles per mole of silver.

First Layer (Antihalation Layer) Black Colloidal Silver 0.16 UV-1 0.3 CM-1 0.044 OIL-1 0.044 Gelatin 1.33 Second Layer (Intermediate Layer) AS-10 .16 OIL-1 0.20 Gelatin 1.40 Third layer (low-sensitivity red-sensitive layer) Silver iodobromide a 0.12 Silver iodobromide b 0.50 SD-1 3.0 × 10 ^-5 SD-4 1.5 × 10 ^-4 SD-3 3.0 × 10 ^-4 SD-6 3.0 × 10 ^-6 C-1 0.51 CC-1 0.047 OIL-2 0.45 AS- 2 0.005 Gelatin 1.40 4th layer (medium-speed red-sensitive layer) Silver iodobromide c 0.64 SD-1 3.0 × 10 ^-5 SD-2 1.5 × 10 ^-4 SD- ^{3 3.0 × 10 -4 C-2} 0.22 CC-1 0.028 DI-1 0.002 OIL-2 0.21 AS-3 0.006 Zera Down 0.87 Fifth Layer (high sensitivity red-sensitive layer) Silver iodobromide c 0.13 Silver iodobromide d 1.14 SD-1 3.0 × 10 -5 SD-2 1.5 × 10 ^-4 SD-3 3.0 x 10 ^-4 C-2 0.085 C-3 0.084 CC-1 0.029 DI-1 0.027 OIL-2 0.23 AS-3 0.013 Gelatin 1 .23 6th layer (intermediate layer) OIL-1 0.29 AS-1 0.23 gelatin 1.00 7th layer (low sensitivity green color sensitive layer) Silver iodobromide a 0.245 Silver iodobromide b 0.105 SD-6 5.0 × 10 ⁻⁴ SD-5 5.0 × 10 ⁻⁴ M-1 0.21 CM-2 0.039 OIL-1 0.25 AS-4 0.063 gelatin 0. 98 8th layer (intermediate layer) M-1 0.03 CM-2 0.005 OIL-1 0.16 AS-1 0.11 gelatin 0.80 9th layer (middle) Sensitive green color-sensitive layer) Silver iodobromide e 0.87 SD-7 3.0 × 10 ^-4 SD-8 6.0 × 10 ^-5 SD-9 4.0 × 10 ^-5 M-10. 17 CM-2 0.048 CM-3 0.059 DI-2 0.012 OIL-1 0.29 AS-4 0.05 AS-2 0.005 Gelatin 1.43 10th layer (high sensitive green color sensitivity) Silver iodobromide f 1.19 SD-7 4.0 × 10 ^-4 SD-8 8.0 × 10 ^-5 SD-9 5.0 × 10 ^-5 M-1 0.09 CM-3 0.020 DI-3 0.005 OIL-1 0.11 AS-4 0.026 AS-5 0.014 AS-6 0.006 Gelatin 0.78 11th layer (yellow filter layer) Yellow colloidal silver 05 OIL-1 0.18 AS-7 0.16 Gelatin 1.00 12th layer (low-sensitivity blue-sensitive layer) Silver iodobromide g 0 .29 silver iodobromide h 0.19 SD-10 8.0 × 10 ^-4 SD-11 3.1 × 10 ^-4 Y-1 0.91 DI-4 0.022 OIL-1 0.37 AS- 2 0.002 Gelatin 1.29 13th layer (high-sensitivity blue color-sensitive layer) Silver iodobromide h 0.13 Silver iodobromide i 1.00 SD-10 4.4 × 10 ^-4 SD-11 1 .5 × 10 ⁻⁴ Y-1 0.48 DI-4 0.019 OIL-1 0.21 AS-2 0.004 Gelatin 1.55 14th layer (first protective layer) Silver iodobromide j 0. 30 UV-1 0.055 UV-2 0.110 OIL-2 0.63 Gelatin 1.32 Fifteenth layer (second protective layer) PM-1 0.15 PM-2 0.04 WAX-1 0.02 D-1 0.001 Gelatin 0.55 In addition to the above composition, coating aids SU-1 and SU-
2, SU-3, dispersing aid SU-4, viscosity modifier V-1,
Stabilizers ST-1, ST-2, antifoggant AF-1, weight average molecular weight: 10,000 and weight average molecular weight: 1,
100,000 two types of polyvinylpyrrolidone (AF-
2), inhibitors AF-3, AF-4, AF-5, hardener H
-1, H-2 and the preservative Ase-1 were added.

The structures of the compounds used in the above samples are shown below.

Table 13 shows the characteristics of the above silver iodobromide.

[0120]

[Table 13]

[0121]

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[0122]

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[0123]

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[0124]

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[0125]

[Chemical 6]

[0126]

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[0127]

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[0128]

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[0129]

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As a preferable example of the formation of silver halide grains of the present invention, a production example of silver iodobromide d and f is shown below.

Preparation of seed crystal emulsion-1 A seed crystal emulsion was prepared as follows.

Japanese Patent Publications 58-58288 and 58-58
No. 289, a silver nitrate aqueous solution (1.161 mol) was added to the following solution A1 adjusted to 35 ° C.
And a mixed aqueous solution of potassium bromide and potassium iodide (2 mol% of potassium iodide) at the same time while maintaining the silver potential (measured with a silver ion selective electrode using a saturated silver-silver chloride electrode as a reference electrode) at 0 mV. Was added over 2 minutes to form nuclei. Subsequently, the liquid temperature was raised to 60 ° C. over 60 minutes, the pH was adjusted to 5.0 with an aqueous sodium carbonate solution, and then an aqueous silver nitrate solution (5.902 mol), potassium bromide and iodide were added. A mixed aqueous solution of potassium (2 mol% potassium iodide) was added over 42 minutes by the simultaneous mixing method while maintaining the silver potential at 9 mV. After the addition was completed, the temperature was lowered to 40 ° C., and desalting and washing with water were immediately performed using a usual flocculation method.

The obtained seed crystal emulsion had an average sphere-converted diameter of 0.24 μm, an average aspect ratio of 4.8, and 90% or more of the total projected area of silver halide grains had a maximum side ratio of 1.0.
The emulsion consisted of hexagonal tabular grains of .about.2.0.
This emulsion is called seed crystal emulsion-1.

[Solution A1] Ocein gelatin 24.2 g Potassium bromide 10.8 g HO (CH ₂ CH ₂ O) _m (CH (CH ₃ ) CH ₂ O) _19.8 (CH ₂ CH ₂ O) _n H (m + n = 9.77) (10% ethanol solution) 6.78 ml 10% nitric acid 114 ml H ₂ O 9657 ml Preparation of silver iodide fine grain emulsion SMC-1 6.0% by weight aqueous gelatin solution containing 0.06 mol of potassium iodide. While vigorously stirring 5 liters, 7.06
2 liters of an aqueous silver nitrate solution and 2 liters of a 7.06 mol aqueous potassium iodide solution were added over 10 minutes. During this time, the pH was controlled at 2.0 using nitric acid, and the temperature was controlled at 40 ° C. After the particles are prepared, the pH is adjusted using an aqueous sodium carbonate solution.
Was adjusted to 5.0. The average particle size of the obtained silver iodide fine particles was 0.05 μm. This emulsion is called SMC-1.

Preparation of silver iodobromide d Seed crystal emulsion-1 corresponding to 0.178 mol and HO (CH ₂ CH ₂
O) _m (CH (CH ₃ ) CH ₂ O) _19.8 (CH ₂ CH ₂ O) _n
H (m + n = 9.77) in 10% ethanol solution 0.5
4.5 wt% inert gelatin aqueous solution containing 70 ml
Keep 0 ml at 75 ° C, pAg 8.4, pH 5.0
Then, particles were formed by the simultaneous mixing method with vigorous stirring by the following procedure.

1) 2.1 mol of silver nitrate aqueous solution and 0.19
5 mol of SMC-1 and an aqueous solution of potassium bromide were added to pA
g while maintaining the pH at 8.4 and the pH at 5.0.

2) Then, the solution was cooled to 60 ° C., and pAg
Was adjusted to 9.8. Then, 0.071 mol of SMC
-1 was added and aging was performed for 2 minutes (introduction of dislocation lines).

3) 0.959 mol of silver nitrate aqueous solution and 0.
03 mol of SMC-1 and an aqueous solution of potassium bromide were added to p
Ag was added at 9.8 and the pH was maintained at 5.0.

In addition, each solution was added at an optimum rate during the formation of particles so that the formation of new nuclei and the aging of Ostwald between particles do not proceed. After completion of the addition, the resultant was subjected to a water washing treatment at 40 ° C. using a normal flocculation method, and then gelatin was added and redispersed to adjust the pAg to 8.1 and the pH to 5.8.

The obtained emulsion had a grain size (cubic 1 having the same volume).
The emulsion was composed of tabular grains having a halogen composition of 0.75 μm in side length, an average aspect ratio of 5.0, and a halogen composition of 2 / 8.5 / X / 3 mol% (X is a dislocation line introduction position) from the inside of the grains. . When this emulsion was observed with an electron microscope, five or more dislocation lines were observed both in the fringe portion and in the inside of the grain in 60% or more of the total projected area of the grain in the emulsion. The surface silver iodide content was 6.7 mol%.

Preparation of silver iodobromide f In the preparation of silver iodobromide d, pAg was adjusted to 8.
The silver iodobromide f was prepared in exactly the same manner as the silver iodobromide d except that the amount of silver nitrate added in step 3) was 0.92 mol and the amount of SMC-1 was 0.069 mol. .

The obtained emulsion had a grain size (cubic 1 having the same volume).
An emulsion comprising tabular grains having a halogen composition of 0.65 μm, an average aspect ratio of 6.5, and a halogen composition of 2 / 8.5 / X / 7 mol% (X is a dislocation line introduction position) from the inside of the grains. . When this emulsion was observed with an electron microscope, five or more dislocation lines were observed both in the fringe portion and in the inside of the grain in 60% or more of the total projected area of the grain in the emulsion. The surface silver iodide content was 11.9 mol%.

The above-mentioned sensitizing dyes were added to each of the above emulsions and ripened, and then triphosphine selenide, sodium thiosulfate, chloroauric acid and potassium thiocyanate were added, and the fog and the sensitivity were optimized according to a conventional method. Chemical sensitization was performed so that

Silver iodobromide a, b, c, e, g, h, i, j
Was also subjected to spectral sensitization and chemical sensitization according to d and f above.

The samples 101 to 115 were subjected to the following magnetic head clogging evaluation test (undeveloped).
Further, the same exposure test was performed on the photographic component layer, which was subjected to image exposure and developed as described below.

(Treatment Step) Treatment Step Treatment Time Treatment Temperature Replenishment Amount * Color development 3 minutes 15 seconds 38 ± 0.3 ° C. 780 ml Bleach 45 seconds 38 ± 2.0 ° C. 150 ml fixation 1 minute 30 seconds 38 ± 2. 0 ° C. 830 ml stable 60 seconds 38 ± 5.0 ° C. 830 ml dry 1 minute 55 ± 5.0 ° C .- * Replenishment amount is a value per 1 m ² of the light-sensitive material.

The following color developing solution, bleaching solution, fixing solution, stabilizing solution and its replenishing solution were used.

Color developer and color developing replenisher developer Replenisher replenisher Water 800 ml 800 ml Potassium carbonate 30 g 35 g Sodium hydrogen carbonate 2.5 g 3.0 g Potassium sulfite 3.0 g 5.0 g Sodium bromide 1.3 g 0.4 g Iodide Potassium 1.2 mg-Hydroxylamine sulfate 2.5 g 3.1 g Sodium chloride 0.6 g-4-Amino-3-methyl-N-ethyl-N- (β-hydroxylethyl) aniline sulfate 4.5 g 6.3 g Diethylenetriamine pentaacetic acid 3.0 g 3.0 g Potassium hydroxide 1.2 g 2.0 g Water was added to make 1 liter, and potassium hydroxide or 20%
The color developing solution is adjusted to pH 10.06 and the replenisher is adjusted to pH 10.18 using sulfuric acid.

Bleaching solution and bleach replenishing solution Bleaching solution Replenishing solution Water 700 ml 700 ml 1,3-Diaminopropanetetraacetic acid iron (III) ammonium 125 g 175 g Ethylenediaminetetraacetic acid 2 g 2 g Sodium nitrate 40 g 50 g Ammonium bromide 150 g 200 g Glacial acetic acid 40 g 56 g Water The pH of the bleaching solution is adjusted to pH 4.4 and the replenishing solution is adjusted to pH 4.0 using ammonia water or glacial acetic acid.

Fixing Solution and Fixing Replenishing Solution Fixing Solution Replenishing Solution Water 800 ml 800 ml Ammonium thiocyanate 120 g 150 g Ammonium thiosulfate 150 g 180 g Sodium sulfite 15 g 20 g Ethylenediaminetetraacetic acid 2 g 2 g Ammonia water or glacial acetic acid is used as a fixing solution at pH 6.2.
Then, the pH of the replenisher is adjusted to 6.5, and then water is added to make 1 liter.

Stabilizer and stable replenisher water 900 ml p-octylphenol ethylene oxide 10 mol adduct 2.0 g dimethylolurea 0.5 g hexamethylenetetramine 0.2 g 1,2-benzisothiazolin-3-one 0.1 g siloxane (UCC) L-77) 0.1 g ammonia water 0.5 ml After adding water to make 1 liter, ammonia water or 50
Adjust to pH 8.5 with% sulfuric acid.

<< Evaluation Method >> 1. Evaluation of magnetic recording performance (S / N) Each sample obtained by cutting a magnetic recording medium coated with each layer having the composition described above in a multi-layered manner to a width of 1 inch and a length of 50 m was provided with a track width of 1.5 mm, a head gap of 7 μm, and the number of turns. 1
100 mm / S using 000 input / output heads
A recording density signal of 1000 bpi is recorded at a feed speed of. Thereafter, the ratio of the output S to the noise N when the signal was reproduced at the same head and at the same speed was measured.

The values shown are the values when the S / N ratio of the magnetic recording layer obtained in the comparative example is 0 dB. The evaluation was performed at 23 ° C. and 58% RH.

[0154] 2. Clog evaluation test of magnetic head A magnetic recording medium coated with each layer of the composition described above in multiple layers was cut into a sample having a width of 1 inch and a length of 50 m.
A square wave signal of Hz was recorded at a transport speed of 100 mm / S.

Next, the above-mentioned development processing was performed on the above-mentioned sample. The composition of the processing solution used in each step is as described above.

Next, the rectangular waveform signal was read by the magnetic reading head at the same speed, and the number of reproduction errors in which the output became 35% or less of the initial value was evaluated.

Reproduction error: The pulse output is 35% of the initial value.
The phenomenon that became the following. The same phenomenon of 100 pulses or less is counted as one.

3. Observation of Head Contamination with Microscope The head was removed, and the condition of surface contamination was observed with a microscope and evaluated according to the following grades.

Whole surface dirt: × Head dirt 50% or more: △ Head dirt, 10% or less: ○ 3. Haze (finished base) The haze of the sample (finished base) before coating the emulsion is measured by a turbidimeter (TURBINDIMETER: Mitsubishi Kasei Kogyo Co., Ltd.).
Was used for the measurement.

4. Durability of Magnetic Layer Using HEIDON-14DR (manufactured by Shinto Kagaku Co., Ltd.), the film was repeatedly worn for 100 passes at a head load of 300 g and a speed of 100 mm / s.

Scratched state None: ○ Weak scratch: Δ Strong scratch: × The above results are shown in Table 14.

[0162]

[Table 14]

Further, except for the magnetic layer coating liquid 15, all the liquids were not separated even after 3 days from the preparation of the magnetic layer coating liquid, and the stability was good.

As is clear from Table 14, since the non-magnetic abrasive of the present invention is substantially coated with the binder, the coating liquid is not separated, and the magnetic recording performance, the clogging of the magnetic head, the head contamination, A magnetic recording medium having improved haze and durability of the magnetic layer can be obtained. In particular, an abrasive and a binder are kneaded and dispersed at a dispersion viscosity of 100,000 cp to 100 million cp to obtain a dispersion of the abrasive. It can be seen that the objects of the invention can be achieved.

[0165]

According to the present invention, firstly, the head cleaning property is imparted to improve the head clog resistance after the treatment. Secondly, to provide a magnetic recording medium with less head contamination. Thirdly, to prevent deterioration of magnetic properties and optical properties due to aggregation of abrasive particles. Fourthly, it was possible to provide a recording medium having an excellent magnetic coating film strength capable of withstanding repeated use of the head.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G11B 5/842 G11B 5/842 A // G03C 1/00 GAP G03C 1/00 GAPE

Claims (5)

[Claims] 1. A magnetic recording medium having a magnetic recording layer containing at least magnetic particles, a non-magnetic abrasive and a binder on a support, wherein the abrasive is substantially covered with the binder. And a magnetic recording medium. 2. A method for producing a magnetic recording medium, which comprises kneading and dispersing an abrasive and a binder at a dispersion viscosity of 100,000 cp to 100 million cp to obtain an abrasive dispersion. 3. The method for producing a magnetic recording medium according to claim 2, wherein the kneading dispersion is a pressure kneader kneading dispersion. 4. The weight average molecular weight of the binder is 2 to
A cellulose ester of 300,000.
The manufacturing method of the magnetic recording medium according to the above. 5. A method for producing a magnetic recording medium, which comprises preparing a coating liquid for a magnetic recording layer by dispersing an abrasive in a low molecular weight binder and then adding a magnetic particle dispersion and a high molecular weight binder.