JPS583132A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium excellent in electric characteristic abrasion resistance performance in which the processing time for curing is short and generation of curl is prevented, by providing a background layer including a polymer made by electron rays at a plane opposite to the magnetic substance layer of a supporting body. CONSTITUTION:One plane of a support is provided with a coating type magnetic substance layer or a metallic thin film type magnetic substance layer obtained through the irradiation of electrons of a layer including a chemical compound possible for polymerization with electron rays and a ferromagnetic powder, for example, and another plane is provided with a layer including a chemical compound possible for polymerization with electron rays, such as those having vinyl or vinylidene carbon-carbon double bond, acryloyl group, acrylamide group, allyl group, vinylether group and vinylthioether group and unsaturated polyester, and the background layer is formed by irradiating the electron rays for polymerization and curing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium that prevents curling of the magnetic recording medium and has excellent electrical properties and wear resistance.

Magnetic recording media that are currently widely used include ferromagnetic magnetic powders such as ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, and ferromagnetic alloy powder on a non-magnetic support, and a vinyl chloride-acetate-based copolymer. , a coating type in which the resin is dispersed in an organic binder such as a polyvinylidene chloride copolymer, a cellulose resin, an acetal resin, a urethane resin, or an acrylonitrile butadiene resin, and then coated and dried has been widely used. In addition, with the increasing demand for high-density recording, vacuum evaporation.

2. Description of the Related Art Metal thin film type magnetic recording media in which a magnetic recording layer is a ferromagnetic metal thin film formed by a paper deposition method such as sputtering or an ion plater have been attracting attention. In either case, the magnetic recording medium is curled with concave portions on the magnetic layer side, resulting in poor contact with the head of a video tape recorder or audio tape recorder, resulting in a significant drop in electrical characteristics.

The edges that are likely to come into contact with the head 9 are prone to wear, which may cause P dropout or a decrease in output.

The cause of curling in coated magnetic recording media is presumed to be volumetric contraction of the magnetic layer due to solvent evaporation. In the case of metal thin film type magnetic recording media, the cause is thought to be thermal contraction of the support due to heating of the support surface on which the magnetic layer is formed.

In recent years, there has been a demand for thinner supports for long-term recording on magnetic recording media, but as the supports are made thinner, curling becomes larger and this poses an extremely serious problem in practice.

A method of providing a coating film (back layer) consisting of inorganic pigment powder and thermoplastic resin on the back side of a support is disclosed in Japanese Patent Publication No. 54-3432.
No. 4, etc., when only a thermoplastic resin was used, the problem was that the atomic layer was easily damaged and the scraped powder increased P dropout.

JP-A-51-144604 discloses the use of a thermoplastic resin and a trifunctional incyanate compound as a binder for the back layer in order to improve scratch resistance.
This method has the drawback that it takes too much time for thermal curing, and is economically disadvantageous. In addition, there was a quality defect in that blocking occurred because it was stored in rolled rolls during the curing process.

The above-mentioned method of providing the groove layer is intended to reduce running tension by increasing the surface roughness of the back layer by mixing inorganic pigment powder, but it is also effective in preventing curling. However, the conventional back layer had a quality defect in that blocking occurred due to the long curing process time.

As a result of intensive research, the present inventors solved the above problem by providing a back layer containing a polymer produced by electron beams on the support surface opposite to the magnetic layer.

The purpose of the present invention is, firstly, to provide a magnetic recording medium with excellent electrical properties, secondly, to provide a magnetic recording medium with excellent wear resistance, and thirdly, to provide a magnetic recording medium with excellent abrasion resistance. An object of the present invention is to provide a magnetic recording medium that requires extremely short processing time.

The above-mentioned object of the present invention is to provide a magnetic recording medium having a magnetic layer on one side of a support and a back layer on the other side, when the back layer contains a compound polymerizable by electron beams and is irradiated with an electron beam. This is achieved by a magnetic recording medium that is a layer obtained by using K.

Although the present invention can be applied to a recording medium having any kind of magnetic layer, the most preferred embodiment uses a magnetic layer obtained by electron irradiation of a layer containing a compound that can be polymerized by electron beams and ferromagnetic powder. The invention is to provide the back layer on a magnetic recording medium having a magnetic recording medium. In this case, the manufacturing method is
■ A method of coating a magnetic recording layer using a support having a back layer that has been irradiated with an electron beam in advance and then irradiating it with an electron beam; ■ A method of sequentially or simultaneously coating a back layer and a magnetic recording layer each containing a compound that can be polymerized by an electron beam. There are two methods: a method in which the back layer and the magnetic recording layer are simultaneously polymerized and hardened by applying electron beam irradiation, and a method in which the back layer is formed after coating the magnetic recording layer and electron beam irradiation. A method of polymerizing and curing by simultaneous electron beam irradiation is preferred because it has high energy efficiency.

The two layers of the present invention are a thermosetting coating type magnetic recording medium,
It can also be used in the case of metal thin film type magnetic recording media, and a dramatic improvement in electrical properties can be achieved.

In these cases, either the magnetic layer or the magnetic layer may be provided first.

Compounds that can be polymerized by electron beams are compounds that have unsaturated bonds that can be polymerized by electron beams, such as compounds that preferably have a plurality of vinyl or vinylidene carbon-carbon double bonds, such as acryloyl groups, acrylamide, etc. P
These include compounds containing a group such as a group, an allyl group, a vinyl ether group, a vinyl thioether group, etc., and a compound such as an unsaturated polyester.

Particularly preferred are compounds having acryloyl or methacryloyl groups at both ends of a straight chain as the above-mentioned unsaturated bond-containing compound;
Fatipsc Congress”11 19 (19
72). for example.

The polyester skeleton of the exemplified compound may be a polyurethane skeleton, an epoxy resin skeleton, a polyether skeleton, a polycarbonate skeleton, or a mixture thereof. Moreover, the terminal of the illustrated compound may be a methacryloyl group. The molecular weight is preferably about 500 to 20,000.

Furthermore, a monomer having an unsaturated carbon-carbon bond in the molecule can be added to these compounds.

Examples of such monomers include:

Acrylic acid, methacrylic acid, itaconic acid, methyl acrylate and its homologues, acrylic acid alkyl esters, methyl methacrylate and its homologs, methacrylic acid alkyl esters, styrene and its homologs α
Examples include -methylstyrene, β-chlorostyrene, acrylonitrile, methacrylaterile, acrylamide, methacrylamide, vinyl acetate, vinyl propionate, and the like. There may be two or more unsaturated bonds in the molecule. An example of this compound is "Photosensitive resin data collection"
Sogo Kagaku Kenkyusho Co., Ltd. Published in December 1960 235-2
Examples include the compounds listed on page 36. In particular, unsaturated esters of polyols.

For example ethylene diacrylate, :) ethylene glycol diacrylate, glycerol trimethacrylate,
Preferred are ethylene dimethacrylate, pentaerythritol tetramethacrylate, and grindyl methacrylate having an epoxy ring. A compound having one unsaturated bond in the molecule and a compound having two or more unsaturated bonds may be used in combination.

When adding monomer, the ratio to polymer is polymer/
Monomers of 2278 or more are preferred. Outside this range, a large amount of energy is required for curing.

Further, fine inorganic pigment powder can be added to the back layer of the present invention, if necessary. Carbon black and /raffite are used as inorganic pigment fine powder.

Zinc oxide, titanium oxide, nosium sulfate, talc/kaolin, chromium oxide, merium sulfide, goethite, silica tyrosyl, anhydrous alumina fine powder calcium carbonate, molybdenum disulfide, carbon fluoride, etc. are used. The particle size of these powders is preferably 3 microns or less.

The back layer of the present invention may contain thermoplastic resins such as vinyl chloride/vinylidene chloride copolymers, cellulose resins, acetal resins, vinyl chloride vinylidene chloride resins, urethane resins, acrylonitrile butadiene resins, etc., singly or in combination, as necessary. May be added.

Further, the knock layer of the present invention contains a lubricant 1 dispersant.

Additives such as abrasives, rust preventives, and antistatic agents may also be included. In particular, lubricants include saturated and unsaturated higher fatty acids, fatty acid esters, higher fatty acid amides 9, higher alcohols, silicone oils, mineral oils, food oils, animal oils, furan compounds, and the like.

In preparing the coating solution for the back layer, the above-mentioned components are all added to a kneader simultaneously or individually one after another. Various types of crosstalk machines are used for crosstalk dispersion of coating compositions. For example, two-roll mill, three-roll mill, whole mill, pebble mill, tron mill, Santo 9 glider, Szθg
vari attritor.

These include high-speed impeller dispersion machine, high-speed stone mill, high-speed impact mill, disper, Ni-Goo, high-speed mixer homogenizer, and ultrasonic dispersion machine.

The technologies related to crosstalk dispersion are T, C, PATTON”
Pa1nt Flow and Pigment Di
John Will (1964)
(Published by Ey & 5ons). Also, U.S. Patent Nos. 2,581,414 and 2,855,156
It is also mentioned in the issue.

Methods for applying the back layer onto the support include air doctor coating, plaid coating, air knife coating, squeeze coating, impregnation coating, reverse roll knee),
) Lance fur roll coat, gravure coat, kiss coat, cast coat.

Spray coat, spin code, etc. can be used, and other methods are also possible, and detailed explanations of these methods are given in "Coating Engineering", pages 256 to 277 (published by Asakura Shoten on March 20, 1970). ing.

The thickness of the layer is applied so that the dry thickness ranges from 0.1 to 5 μm.

The materials for the 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, and cellulose acetate propionate. Cellulose derivatives such as nate:
Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; In addition to plastics such as polycarbonate, polyimir, and polyamideimide, non-magnetic metals such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these, depending on the application: Paper, baryta, or paper coated with or laminated with α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, and ethylene-butene copolymers can also be used. These nonmagnetic supports may be transparent or opaque depending on the purpose of use.

In addition, the form of non-magnetic support is film or tape.

It may be a sheet, disk, car) #, )e ram, etc., and various materials are selected as necessary depending on the form.

The thickness of these non-magnetic supports is about 1 to 50 μm, preferably 2 to 25 μm in the case of films, tapes, and sheets.
It is a book.

As the electron beam accelerator, a Van de Meraf type scanning system, a double scanning system, or a curtain beam system can be adopted, but the curtain beam system is preferable because it is relatively inexpensive and can provide a large output. As for the electron beam characteristics, the accelerating voltage is 100 to 1000 kv, preferably 1
50-300kv, absorbed dose 0.5-20
Megarats P is preferably 2 to 10 Megarats F. When the accelerating voltage is less than 100 kV, the amount of energy transmitted is insufficient, and when it exceeds 1000 kV, the energy efficiency used for polymerization decreases, which is not economical. as an absorbed dose.

If it is less than 0.5 megarans, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained, and if it is more than 20 megarads 9.

The energy used for curing becomes less efficient.

This is not preferable because the object to be irradiated generates heat and the plastic support in particular deforms.

The present invention will be explained in more detail below using Examples and Comparative Examples. It will be readily understood by those skilled in the art that the proportions of ingredients, order of operations, etc. shown herein may be changed without departing from the spirit of the present invention.

Therefore, the invention should not be limited to the examples below. In addition, in the following Examples and Comparative Examples, all "parts" indicate "parts by weight."

Example 1 Magnetic layer coating liquid A "-Fe2"3 100 parts Nitrocellulose (R8μH') 10
〃Polyester polyurethane (Mn 30.000)
5 tt diethylene glycol diacrylate 2 Butoxyethyl acrylate
4〃Stearic acid
1. Silicone oil (polydimethylsiloxane) 1. Methyl ethyl ketone
A mixture of 250 kotara was placed in a ball mill and mixed and dispersed for 2 hours.

Back layer coating liquid B carbon black (average particle size 0.1μ) 50
Calcium carbonate (average particle size 0.08μ) 1
00〃Polyester polyurethane (molecular weight approximately 20,00
0) 30 // Nitrocellulose (viscosity R8+
)I) 401/diethylene glycol diacrylate 10 cyptoxyethyl acrylate 20 thizotyl stearate 1q
6 Methyl ethyl ketone 500 The mixture was placed in a ball mill and kneaded for 10 hours.

Liquid A was applied onto polyethylene terephthalate having a thickness of 15 μm to a dry thickness of 5 μm, subjected to magnetic field orientation treatment, and dried. After drying, the magnetic surface was smoothed using a super calendar roll. Liquid B was applied to the back side of this support to a dry thickness of 1 μm and dried. Then acceleration voltage 165
Electron beam irradiation was performed at a kV beam current of 15 mA. Let's call this sample M1.

Example 2 In Example 1, liquid A was replaced with liquid C, and after smoothing with a calender roll, heat treatment was performed at 60'C for 48 hours.

Next, in the same manner as in Example 1, solution B was applied to the nock and irradiated with an electron beam. Let's call this sample boiled 2.

Liquid C r FgzOs 10 parts Nitrocellulose 15 parts Polyester polyurethane 5 parts Stearic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 250 parts Example 6 The same procedure as Example 1 was carried out except that Liquid B was replaced with liquid in Example 1. . Liquid D as sample I63 Carbon black 30 parts Silica Aerosil (average particle size 0.08μ) 100
Part ester acrylate oligomer (Toagosei Aronix M6100) 4
0 parts hexanediol diacrylate 1
5 parts 2-ethylhexyl acrylate 1
5 parts acrylic acid 2
0 parts methyl stearate
1 part methyl ethyl ketone 50
0 parts Example 4 The same procedure as in Example 1 was carried out except that instead of applying liquid A in Example 1, a magnetic layer was formed by Connold vapor deposition. Using an electron beam evaporation source, cobalt was obliquely evaporated to 200 OA at an incident angle of 70°. Let this sample be 164.

Comparative Example 1 In Example 1, no insulation layer was provided. Sample A
5.

Comparative Example 2 Liquid B in Example 1 was replaced with liquid E. The obtained sample is called Todoroki 6.

Liquid E Carbon black (average particle size 0.1μ) 50
Calcium carbonate (average particle size 0.08μ) 1
00 parts polyester polyurethane (molecular weight 20,000)
30 parts nitrocellulose (viscosity R81H)
9Q part butyl stearate
1 part methyl ethyl ketone 5
The following measurements were performed on the samples obtained in excess of 00 copies, and Table 1 was obtained.

(1) Degree of curl A sample having a width of A inch was slit and the size of two frames in the longitudinal direction was stood on a glass plate at a temperature and humidity of 23t:'651RH, and the distance α traveled by the top end due to curling was measured. (Unit ability) (2) Measurement of methyl scratches by slitting the sample in an inch.

A VHS videotape recorder (Japan Victor Co., Ltd., HR3600) was operated at 1Ar with StillMor (still image playback). Scratches on the surface of the magnetic layer were observed.

(3) Electrical characteristics Color signal taste was measured. Sample JI61 was used as the standard.

Table 1 Preferred embodiments include the following.

(1) A magnetic recording medium in which the support is made of polyethylene terephthalate having a diameter of 5 to 50 microns.

(2. In the claims, the acceleration voltage is 100 to 100
A magnetic recording medium irradiated with an electron beam having a 0 kV absorbed dose of 0.5 to 20 Megaland.

(3) A magnetic recording medium in which the back layer has a thickness of 0.1 to 5 μm within the scope of the claims.

Agent Patent attorney (8107) Kiyotaka Sasaki (and 3 others) Procedural amendment September 1980 Patent application No. 100420 Request 2, Name of the invention Magnetic recording medium 3, Relationship with the person making the amendment case : Patent applicant name (520) Fuji Photo Film Co., Ltd. 7, subject of amendment "Detailed description of the invention" column 8, contents of amendment "Detailed description of the invention" column are amended as follows.

1) Page 7, line 5 of the specification, 1 after "~preferable." Commercially available compounds include Aronix M6100 manufactured by Toagosei Co., Ltd. There are M7100, etc. ” to join.

2) Same page 8, line 2, 1, “Ethylene diacrylate,
After "butoxyethyl acrylate, 1,4-butanediol diacrylate), 1,6-hexanediol diacrylate, stearyl acrylate, 2-ethylhexyl acrylate, 1 is added.

3) On page 8, line 2, 1, after [...diacrylate], add ``diethylene glycyl diacrylate, tetraethylene glycyl diacrylate.''

4) On page 8, lines 2 to 4, add "trimethylol pronotriacrylate, pentaerythritol triacrylate" after "glycerol trimethacrylate."

Amendment to the above procedure June II, 1980 Patent Application No. 100420 2, Name of invention Magnetic recording medium 3, Person making the amendment Relationship to the case: Name of patent applicant (520) Fuji Photo Film Co., Ltd. Name Patent Attorney (8107) Kiyotaka Sasaki (Haga3
Name) 7. Subject of amendment [Detailed description of the invention] column 8. Contents of amendment.

Claims (2)

[Claims] (1) In a magnetic recording medium having a magnetic layer on one side of a support and a back layer on the other side, the back layer is a layer obtained by electron beam irradiation of a layer containing a compound that can be polymerized by electron beams. A magnetic recording medium characterized by: (2) In a magnetic recording medium having a magnetic layer on one side of a support and a knock layer on the other side, electron irradiation is performed on a layer in which the magnetic layer contains a compound polymerizable by electron beams and ferromagnetic powder. 1. A magnetic recording medium, wherein the back layer is a layer obtained by irradiating a layer containing a compound polymerizable with an electron beam with an electron beam.