JPS62192929A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent dimensional stability and stable runnability by forming a layer contg. a resin curable by radiation on a nonmagnetic base and subjecting the layer to curing by radiation in an atmosphere of specific humidity. CONSTITUTION:The layer contg. the resin curable by radiation is formed on the nonmagnetic base and is cured by the radiation in an atmosphere of 60% relative humidity. A coating compd. for the magnetic layer is prepd. by kneading and dispersing the compsn. consisting of ferromagnetic Co-deposited Fe2O3, polyurethane resin curable by radiation, vinyl chloride/vinyl acetate copolymer, carbon black, polishing agent, lecithin, and solvent mixture by using a ball mill and sand mill then filtering the mixture with a filter of 1mum average pore size. The magnetic coating compd. is coated on a polyester film and after the film is subjected to magnetic field orientation and drying treatment, the film is subjected to a mirror finishing treatment by a super calender roll then to irradiation of electron rays in gaseous nitrogen flow and in the atmosphere of 60% relative humidity.

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 used in audio and video equipment, computers, and the like.

BACKGROUND OF THE INVENTION In recent years, the above-mentioned magnetic recording media are moving toward high-density recording, and therefore the recording wavelength is becoming shorter, the recording track width is narrower, and the recording medium thickness is becoming thinner. As a result, the playback output, S
Electromagnetic conversion characteristics such as N ratio are generally becoming disadvantageous. Conventional magnetic recording media are manufactured mainly for the purpose of improving the durability of the magnetic layer. Since these magnetic recording media were obtained by applying heat treatment for a relatively long time after calendering, various problems occurred in the production of magnetic recording media having homogeneous characteristics and highly smooth surfaces. For example, variations in coating film properties due to the short pot life of magnetic paints, or variations in the surface properties of the magnetic layer, not only due to the dispersibility of the magnetic powder but also due to the surface properties of the non-magnetic powder support on which the magnetic layer is formed. It is extremely susceptible to the influence of the surface properties of the back coat layer formed on the non-magnetic support, and there are problems such as the degree of influence being inclined in the longitudinal direction of the product. In order to solve these problems with conventional thermosetting magnetic recording media, a so-called radiation-curable magnetic recording medium was proposed, in which a magnetic layer containing a radiation-curable binder is irradiated with radiation to harden the coating. Many have already been done.

Radiation-curable resins are generally radiation-sensitive modified thermosetting resins, and specific examples include acrylic acid, methacrylic acid, 1'f, t1, etc., which exhibit radically polymerizable unsaturated double bonds. Noko x Dell compound J: Introducing into the molecule at the part 5 that crosslinks or polymerizes by radiation irradiation such as tuna (meth)acrylic-1F bond, maleic acid, maleic acid induction, and double bond of the body. That's true. Other IJ (unsaturated ■-6 bonds that are crosslinked or agreed by radiation irradiation can be used. Such radiation #1lflV! type resin has (1'i alone or a combination of nJ capacity, and can be used in combination with a thermosetting resin depending on the V-performance.

As the radiation, an electron beam using an electron beam added as a 4% source, an r-ray using a 0060 as a source, an X-ray using an X-ray generator as a source, etc. are used. In particular, an irradiation source In 1, the absorption line fife is controlled and introduced into the crusher culm line.

From the point of view of the coverage of ionizing radiation, the electron beam (1Φ method) using an electron beam accelerator is advantageous. 1 degree dose type electron beam accelerator (engineering 1/ri 1)
・“1-carn system) and scanning type low-dose” type electron beam made by [-1 New Bipolar Cine 1]
There are 1 speed gear etc.

1, radiation cross-linking (Ft, -'rii, N, Kas, CO.

IJ (radiation appetizer'・magnetic 1/1
It is said that the 41-radicals in the binder are exposed to oxygen, and due to radiation irradiation, the binder polymerizes due to the influence of ozone. , hardening is inhibited.

Traditionally, magnetic recording media (for example, a sumo wrestler) have been used and stored in environments where the indoor temperature is subject to fluctuations. In recent years, radio cassette players, video cameras, 8m1n Hiteo, etc. have become widely used, and magnetic recording media are often used and stored outdoors at high or low temperatures. ! Hold C
'At high temperatures, high vortices, and high humidity, the magnetic recording medium's
It is extremely easy to cause skew, output drop/(not to mention curling, etc.), which can easily lead to poor running.The recent diversification of magnetic recording devices.

With the improvement of performance, the reliability of the ten lines is becoming more and more the norm51.
-7) 1. It is required to maintain the characteristics of magnetic recording media under such harsh environments.

Conventionally, in order to solve these problems, the use of East-F2 film with a low thermal shrinkage ratio of 117 (for example, JP-A-59-11531, JP-A-59-107-424, JP-A-Sho 60-
15830, Japanese Patent Application Laid-open No. 60-98524),
Use a base film that has been heat-treated in advance (for example, JP-A No. 69-135632, JP-A No. 60-1
There is a proposal to do so.

Problems to be Solved by the Invention [7] In recent years, as the density of magnetic recording media has increased, base films have become thinner and their mechanical strength has weakened. Although it has many characteristics compared to those using thermosetting resins as mentioned above, there is no process of relaxing residual stress during thermosetting, so the = t-t method characteristics of magnetic recording media are not as good. I'm making it a work of art. For this reason, conventional methods are insufficient to maintain the characteristics of magnetic recording media containing radiation-curable resins at high temperatures.

In view of the above-mentioned problems, the present invention provides a magnetic recording medium formed with a layer containing a radiation-curable resin, which is superior in that deformation of the magnetic recording medium due to heat shrinkage is small even when placed under high temperature or high temperature and high humidity. The present invention provides a magnetic recording medium having high dimensional stability and stable running performance.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a magnetic recording medium of the present invention involves forming a layer containing a radiation-curable resin on a non-magnetic support, and forming a layer containing a radiation-curable resin at a relative humidity of 60%. It is characterized by radiation curing in the above atmosphere.

Operation The present invention uses the method described above to not only irradiate 01 with radiation in an inert gas stream but also apply humidity so that the moisture acts with the plasticizer [7] to reliably and quickly remove residual strain inside the magnetic recording medium. It can be removed to improve dimensional stability under high temperature and high humidity conditions.

EXAMPLES Hereinafter, examples of the present invention will be specifically explained using a magnetic tape. Note that all parts of components mentioned in the examples indicate weight ratios.

Non-magnetic supports include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. Derivatives: Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; Plastic films such as polycarbonate, polyimide, polyetherimide, polyamideimide, etc., but any can be applied.0 (Example 1) For magnetic layer Adjustment of paint [A]; Ferromagnetic CO-coated γ-Fe203 100 parts Electron beam curable polyurethane resin 10 parts Vinyl chloride vinyl acetate copolymer 10 parts Carbon blank 3 parts Abrasive agent (A1203)
4 part lecithin
1 part mixed solvent [” M li: K /
300 parts of the above composition (1-luene/anone-1/1/1) was subjected to cross-dispersion using a ball mill and a sand mill, and then filtered through a filter with an average pore size of 1 μm to obtain a magnetic layer coating material ('-A:B ,Got ready.

The above magnetic paint (A) was applied onto the polyester film shown in Table 1, subjected to magnetic field orientation, and drying treatment, followed by mirror polishing treatment using a super calender roll, and then an accelerating voltage of 160 k.
Electron beam irradiation was carried out under conditions such that the absorbed dose was s Mrad in an atmosphere with a relative humidity of 60% under a total nitrogen flow to obtain a raw roll having a magnetic layer with a thickness of 511 m. This is t'
A videotape sample (250 m long) was manufactured by cutting it to an A inch width.

(Example 2) "-Distributable paint (A) 'e Polyester film shown in Table 1" was applied, magnetic field oriented, and dried, followed by mirror polishing treatment using a super calender roll, and then accelerated voltage 1
Electron beam irradiation was performed in an atmosphere with a relative humidity of 80% under a nitrogen stream under conditions such that the absorbed dose was sMrad at 60 kV.
A raw roll having a magnetic layer with a thickness of E511 m was obtained. This was cut into μ inch width and a videotape sample (260 mm) was obtained.
(Comparative Example 1) The magnetic paint (Al:l') was applied onto the polyester film shown in Table 1, subjected to magnetic field orientation and drying treatment, followed by mirror polishing treatment using a super calender roll, and then accelerated treatment. Voltage 1
Electron beam irradiation was carried out in an atmosphere with a relative humidity of 40% under a nitrogen stream under conditions such that the absorbed dose of 60 kV was 8 Mrad, and a raw roll having a magnetic layer with a thickness of 5 μm was obtained. Cut and cut videotape samples (250
77+, long) manufactured 10.1. , did.

(Comparative Example 2) The above magnetic paint CAlk was coated on the polyester film shown in Table 1, subjected to magnetic field orientation, and drying treatment, followed by mirror finishing treatment using a super calender roll, and then an accelerating voltage of 160 k.
Electron beam irradiation was performed in an atmosphere of 50% relative humidity under a nitrogen stream under conditions such that the V absorbed dose was s Mrad, and a raw roll having a magnetic layer with a thickness of 1511 m was obtained. This was cut into inch-wide pieces to produce videotape samples (260 m long).

Table 1 Magnetic tape i? obtained in each of the Examples and Comparative Examples. Using L material, the bonds shown in Table 2 were obtained.

Table 2 1) Heat shrinkage rate Heat treatment strip ply; 1oo''C11 hour heat shrinkage rate - (L-L') /L (The length of the sample tape is at 30°C) 2) Under the heat treatment conditions described in Carl's notes, it was determined by [1st test f1].

39 runs VH8 type VTR (Matsu-1-manufactured by Denki Sangyo Co., Ltd., NY)
-8200) f, 60'' (+ (7) Environment 1; Run to check stability.

According to the present invention, a layer containing a radiation (1q1) type resin is formed on a river sand 4Il da carrier, and a layer containing radiation (1q1) type resin is formed on the river sand 4Il da carrier, and radiation Curing: Even if the magnetic recording medium is placed under high temperature or high temperature and high humidity, the deformation of the magnetic recording medium due to heat II or shrinkage is small, and the stability of the magnetic recording medium is 1.ρ.・A magnetic recording medium having stable running properties can be produced as much as 17'I'g.

Although magnetic tape has been described in Example I, it should be noted that the present invention is applicable not only to magnetic tape but also to other magnetic recording media such as magnetic disks and magnetic cards. It's not even a size.

Claims (1)

[Claims] A method for producing a magnetic recording medium, which comprises forming a layer containing a radiation-curable resin on a non-magnetic support, and curing the layer with radiation in an atmosphere with a relative humidity of 60% or more.