JPH01109520A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent stability by subjecting a magnetic tape continuously to a heating and humidifying treatment at 20-50g/cm tension, 80-120 deg.C, and >=60% relative humidity. CONSTITUTION:The magnetic tape is delivered from a raw sheet roll 1 and is coated with a back coating layer by a coating machine 2. This tape passes a drying zone 3 set with successively high temps. so that the coated film is dried. The tape is subjected to surface finishing by a super calender consisting of a specular-surface roll 4 and an elastic roll 5 and is further sent to a heating and humidifying zone 7 for the purpose of the heating and humidifying treatment. The control of the tape traveling and low tension is executed by nip rolls 6, 9 and dancer rolls 8 at this time. The film travel is unstable if the tension is <=20g/cm and the relieving of residual stress is insufficient if the tension exceeds 50g/cm. The skew strain quantity is greatly decreased and the deformation by thermal shrinkage is decreased in spite of exposing the tape to a high temp. if the temp. is kept at 80-120 deg.C and the humidity at >=60% in the heating and humidifying treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic sheets used in audio equipment, video equipment, computers, etc. The present invention also relates to a method of manufacturing a magnetic recording medium with excellent dimensional stability.

Conventional magnetic tapes are obtained by forming a magnetic layer on a non-magnetic support, but as recording density increases, the magnetic layer becomes highly smooth and running properties deteriorate. As a countermeasure against this problem, a back coat layer is often provided (for example, JP-A-57-2027811).

Non-magnetic supports used in magnetic tapes include polyesters such as polyethylene terephthalate and polyethylene 2.6 naphthalate, polyolefins such as polyethylene and polypropylene, cellulose acetate, and cellulose diacetate.

Examples include cellulose derivatives such as cellulose acetate butyrate and cellulose acetate propylate, vinyl resin polycarbonates such as polyvinyl chloride and polyvinylidene chloride, and plastic films such as polyimide, polyetherimide, and polyamideimide.

Currently, dimensional stability is 9, elongation is 9, surface roughness is 9, and film formability is high.

Polyethylene terephthalate is superior in terms of cost.
(PET) is widely used as a non-magnetic support for magnetic tape.

Conventionally, magnetic recording media, such as audio tapes and video tapes loaded in cassettes, have been used and stored in environments with moderate indoor temperature changes.

However, in recent years, radio cassettes, portable/l/VTR
.

With the widespread use of camera-integrated VTRs, 8m VTRs, etc., magnetic recording media are increasingly being used outdoors in high and low temperature environments. Especially at high temperatures,
The problem is that the deformation of the magnetic recording medium is significant, causing not only skew, output reduction, and reproduction frequency change (for example, 1988 Institute of Electronics and Communication Engineers General Conference 1-188), but also the occurrence of curling, which tends to cause running problems. there were. With the recent diversification and higher performance of magnetic recording systems, running reliability is becoming increasingly important, and there is a need to maintain the characteristics of magnetic recording media under such harsh environments.

Conventionally, in order to solve these problems, the use of a base film with a low heat shrinkage rate (for example, JP-A-59-11531, JP-A-59-107424, JP-A-60-15830, JP-A-6O-98524) and Use of a heat-treated base film (e.g. JP-A-59-135632)
．． JP-A-6098524) has been proposed.

Problems to be Solved by the Invention In addition to the above-mentioned demands for better dimensional stability in magnetic recording media, base films are also becoming thinner as the density of magnetic recording media increases. , the mechanical strength is weakened, making it even more difficult to maintain the dimensional stability of the magnetic recording medium. For this reason, conventional methods have been insufficient in maintaining the characteristics of magnetic recording media at high temperatures.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a magnetic recording medium that has dimensional stability and stable running performance even when the magnetic recording medium is placed under high temperatures.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method of forming a magnetic recording layer on one main surface of a continuously running non-magnetic support.
A back coat layer is fixed on the other main surface, and in the surface finishing process, the magnetic tape is continuously applied with a tension of 20 to 5
0 g/3, a temperature of 80 to 120°C, and a relative humidity of 60% or more.

Function: As a result of intensive research, the inventor of the present invention found that by applying heating and humidification under low tension during the drying process of the back coat layer, the residual strain inside the magnetic recording medium is rapidly removed, making it possible to use the medium at high temperatures. It has also been found that it has excellent dimensional stability and that its properties are maintained.

Note that if the tension is too low, such as 2097 as or less, the running of the film will become unstable, and if it is higher than 509/CIA, the removal of residual strain, which is the objective of the present invention, will not be sufficient. Similarly, if the temperature and humidity are outside the above ranges, the removal effect will not be sufficient.

EXAMPLE Next, a method for manufacturing a magnetic recording medium according to the present invention will be explained using a magnetic tape as an example.

First, the magnetic layer is formed as follows. A magnetic coating solution having a desired component ratio is prepared by sufficiently mixing and dispersing magnetism and the like with an organic solvent in a mixer.

The magnetic powder used here is magnetic iron oxide.

Any of cobalt-magnetized iron oxide, chromium dioxide, metallic magnetic powder, barium ferrite magnetic powder, iron nitride magnetic powder, iron carbide magnetic powder, etc. may be used.

As the antistatic agent, an inorganic conductive starch powder such as carbon black or graphite powder or an organic surfactant is used in a required amount.

The abrasive materials include alpha alumina, r alumina, titanium oxide, red iron oxide, chromium oxide, and silicon carbide.

One or a combination of two or more of inorganic high-hardness fine particles such as cerium oxide, boron carbide, and silicon oxide and fine plastic powder are used.

Fiber resins such as binders, nitrocellulose, cellulose acetyl butyrate, vinyl chloride vinyl acetate copolymer resins, vinylidene chloride resins, polyurethane resins, polyamide resins, urea resins, epoxy resins, polyester resins, epoxy resins , fluorocarbon resin, acrylonitrile resin.

Among phenol resins and derivatives of these resins, one type or a combination of two or more types are used in consideration of dispersibility and durability of the coating film (for example, Japanese Patent Application Laid-Open No. 50-1774).
27).

Dispersants include higher fatty acids, higher fatty acid metal salts, higher fatty acid amides, higher alcohols, phosphoric acid esters, glycerin, and silane coupling agents.

There are titanium coupling agents, aluminum coupling agents, etc., which are added as necessary.

Examples of the curing agent include polyfunctional low-molecular isocyanates, low-molecular polyamines, and low-molecular polyamides when thermosetting is used, and polyfunctional low-molecular polyepoxy when electron beam curing or radiation curing is used.

To further improve reactivity, organic tin compounds, acidic catalysts,
A crosslinking inhibitor such as an alkaline catalyst may be added.

Examples of organic solvents include mixtures of methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, xylene, cyclohexanone, ethyl acetate, butyl acetate, tetrahytronane, dimethyl formamide, ethyl alcohol, isopropyl alcohol-rho, ethylene chloride, ethyl alcohol, etc. liquid is used.

These compositions are thoroughly mixed and dispersed together with a solvent in a mixer to produce a magnetic paint having a desired component ratio. Mixing machines include paint shaker, V-sil, Bot mill, Dyna mill, and sand mill.

Pin Mill, Pebble Mill, Stone Mi μ, Day Silver,
Atofita, high speed mixer, Henschel mixer, planetarium mixer, pressure kneader.

A continuous kneader, three-roll mill, two-roll mill, ultrasonic dispersion machine, etc. may be used.

The magnetic paint thus obtained is applied onto a non-magnetic support. In order to improve the adhesion between the magnetic coating film and the non-magnetic support, an anchor coating treatment may be performed, or the non-magnetic support may be subjected to a corona discharge or plasma discharge treatment.

As the coating method, a doctor blade method, a Clavier roll method, a reverse roll method, a kiss roll method, a spin cord method, and a Spray Knee 14 method are used. In order to improve the smoothness of the coating film immediately after application, a smoother may be brought into contact with it. A bar smoother, wire smoother, or film smoother is used for this purpose.

Immediately before drying, an orientation treatment is performed using an orientation device using a permanent magnet or an electromagnet, or a randomizer, in order to properly align the magnetic powder in the coated film.

After this, the coating film is dried to remove the solvent. Heat curing treatment, electron beam curing treatment, annealing treatment, etc. are also performed as necessary.

In order to further smooth the coated and dried wide magnetic layer surface, a super calender consisting of an elastic roll and a mirror roll is used to perform surface treatment. The material used for the elastic roll may preferably be nitrium, natural rubber, nylon, polyamide, polyimide, or the like. Calendar conditions include temperature 60-10
0t:, pressure 60-400 storage, 4 shoulders, speed 60-400
m7 minutes is desirable.

For the back coat layer, an inorganic powder, a binder, an organic solvent, and a lubricant (9) and a dispersant (added if necessary) are sufficiently mixed and dispersed in a mixer to prepare a back coat coating solution having a desired component ratio. The pigment contained in the back coat layer is carbon black,
Inorganic pigments such as graphite, calcium carbonate, barium carbonate, titanium oxide, and alumina, or organic pigments such as benzoguanamine are used, and one or more of these pigments are dispersed in the binder. The binder, lubricant 9, dispersant 2, dispersing machine, and coating method are the same as those used for magnetic paint.

The figure shows part of the magnetic tape manufacturing process. The magnetic tape on which the magnetic layer has been formed is sent out from the raw roll/L/1, and after being coated with a back coat layer by a coater 2, it passes through a drying zone 3 whose temperature is set to a high temperature to dry the coating film. The surface is finished with a super calender consisting of a mirror surface L/4 and an elastic L/6, and then sent to zone 7 for heating and humidification treatment. At this time, tape running and low tension control are performed by the nip roll 6.9 and dancer row Iv8. The tape that has been heated and humidified under low tension is wound up as a raw material roll/L'10.

The raw roll thus obtained is cut into inch width pieces to produce a videotape.

(Example 1) The magnetic paint was prepared as follows.

(All parts of each component of the magnetic paint indicate parts by weight.) CO
Contains r F e 203 Magnetic iron oxide 100 parts Polyurethane resin 10 parts PVC resin
10 parts alumina abrasive
5 parts MEK 150 parts Toluene 150 parts The above composition was mixed and dispersed in a sand mill for 16 hours, filtered through a filter having an average particle size of 0.6 μm, coated on 15 μm thick polyethylene terephthalate to a thickness of 4 μm, oriented and dried. Get the jumbo roll.

Next, a back coating solution was prepared as follows.

Carbon black 100 parts Nitrocellulose 40 parts MEK
200 parts toluene
150 parts of the above composition was mixed and dispersed for 24 hours in a Ball Me YV, filtered through a filter having an average particle size of 1 μm, and then applied to the above jumbo roll in a thickness of 1 μm.

It was dried and passed through the heating and humidification treatment zone 7 described above. In the heating and humidification treatment zone 7, the base material tension is 20g2
Temperature is constant at 80℃, relative humidity is 40%, 60℃
% and 80% to obtain raw fabric raw/L/10. This was cut to a width of 1.5 inches to produce a videotape.

(Example 2) The base material tension of heating and humidification treatment zone 7 was 20 g/cm, the temperature was 120°C, and the relative humidity was 40%, 60%, and 80%.
A videotape was produced in the same manner as in Example 1, except that the percentage was changed.

(Example 3) The base material tension of the heating and humidification treatment zone 7 was set to 5097 am,
Got temperature: 40% relative humidity, 60%.

A videotape was produced in the same manner as in Example 1 except that the ratio was changed to 80%.

(Example 4) The base material tension of heating and humidification treatment zone 7 is 6017/ax, the temperature is 1201r, and the relative humidity is 40%, 60%, 80%.
A videotape was produced in the same manner as in Example 1, except that the percentage was changed.

(Comparative Example 1) A videotape was produced in the same manner as in Example 1 except that the base material tension of the heating and humidifying zone 7 was 20 g/cyx, the temperature was 60° C., and the relative humidity was changed to 40%, 60%, and 80%. Created.

(Comparative Example 2) The base material tension of heating and humidification treatment zone 7 is 509/Ql,
Temperature: 60°C, relative humidity: 40%, 60%.

A videotape was produced in the same manner as in Example 1 except that the ratio was changed to 80%.

(Comparative Example 3) The base material tension of heating and humidification treatment zone 7 was 100 I/TI, the temperature was 80° C., and the relative humidity was 40% and 60%.

A videotape was produced in the same manner as in Example 1 except that the ratio was changed to 80%.

(Comparative Example 4) The base material tension of heating and humidification treatment zone 7 was 100 g/ffi, the temperature was 120 t:, the relative humidity was 40%, 60%,
A videotape was produced in the same manner as in Example 1 except that the ratio was changed to 80%.

(Comparative Example 5) The base material tension of heating and humidification treatment zone 7 was 150 g/3,
Temperature: 80°C, relative humidity: 40%, 60%.

A videotape was produced in the same manner as in Example 1 except that the ratio was changed to 80%.

(Comparative Example 6) A videotape was produced in the same manner as in Example 1 except that the substrate tension of the heating and humidification zone 7 was 1 sog/z, the temperature was 120° C., and the relative humidity was changed to 40%, 60%, and 80%. Created.

(Comparative Example 7) A videotape was produced in the same manner as in Example 1 except that it was not passed through the heating and humidification treatment zone 7.

The amount of skew distortion was measured for each sample above, and the results are shown in the table below.

In the above table, the amount of nuke distortion was determined by leaving the VHS system VTR for a day, returning it to an atmosphere of 26° C.-60% R, H, reproducing the image 24 hours later, and measuring the amount of nuke distortion on the monitor screen.

As is clear from the table above, the magnetic tapes obtained as described above are excellent in that the amount of Venue distortion is significantly reduced compared to conventional products.

In the embodiments, only magnetic tape has been described, but it goes without saying that the present invention can be applied not only to magnetic tape but also to magnetic recording media such as magnetic sheets and magnetic cards.

Effects of the Invention As detailed above, according to the present invention, it is possible to obtain a magnetic recording medium which exhibits small deformation due to heat-absorbing MK and excellent dimensional stability even when placed under high temperatures, and which has practical advantages. There is great value.

[Brief explanation of the drawing]

The figure is an explanatory diagram showing a part of the manufacturing process of a magnetic tape. 1...PET raw roll, 2...Gravure coating machine, 3...Drying zone, 4...
・Mirror roll, 6...Elastic roll, θ...
. . . Nip roll, 7 . . . Heating and humidification M-processing zone, 8 . . . Dancer roll, 9 . . . Nip roll, 10 . . . Raw fabric roll.

Claims (1)

[Claims] After forming a magnetic recording layer on one main surface of a continuously running non-magnetic support, a back coat layer is formed on the other main surface, and in the surface finishing process, the magnetic tape is continuously heated to a tension of 20 50 g/cm, temperature 80 to 120° C., and relative humidity 60% or more.