JPH0668447A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To increase the strength of the side end faces of the medium even if the thickness thereof is reduced and to obviate the edge breakage, etc., thereof by depositing a resin on at least a part of the side end faces. CONSTITUTION:The magnetic tape 1 is produced by applying a magnetic layer 3, etc., on a base film 2 which is a broad nonmagnetic base by a known method, then slitting the film. The medium constituting layers, such as magnetic layer 3 and back coating layer 4, are formed by kneading necessary components together with org. solvents selected from ethers, esters, ketones, arom. hydrocarbon, etc., according to the kinds of binders to prepare a coating material, applying such coating material on the nonmagnetic base 2 and drying the coating. After monomers are continuously applied on both flanks of the magnetic tape 1, the coating is irradiated with UV rays and is thereby polymerized and curd, by which resin films 5, 6 are formed. The resins 5, 6 are deposited on at least a part of the side end faces of the medium in such a manner, by which the strength of the side end faces is increased and the edge breakage and destruction are prevented.

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 its manufacturing method.

[0002]

2. Description of the Related Art At present, as the capacity of a magnetic recording medium, for example, a magnetic tape is being increased, the total thickness of the medium is being reduced. However, as the thickness of the medium becomes thinner, the mechanical and physical strengths of the medium itself decrease, and one example thereof is edge breakage of the medium due to guide regulation. This phenomenon frequently occurs when the total thickness of the medium becomes thin and the strength of the medium decreases, and it is often seen at both ends (side end faces) in the medium width direction.

Both ends in the width direction of the magnetic recording medium are not particularly post-treated after the cutting process (slitting) is completed. However, both end portions in the width direction of the medium are weaker than the surface of the magnetic layer with respect to the load, and particularly those having a poor cutting state are considerably damaged due to long-time running or running restriction by a guide.

As a result, the durability of the medium deteriorates, which may cause dropout during use.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the recording capacity by reducing the thickness of a medium and to improve the reliability by eliminating the deterioration of the durability of the end face on the medium side and the increase of dropout. .

[0006]

That is, the present invention relates to a magnetic recording medium in which at least a part of the side end surface is coated with a resin.

In the medium of the present invention, it is desirable that the side end surfaces are covered with a photo-cured (particularly UV-cured) resin.

The present invention also provides a magnetic recording medium, which comprises a step of applying a liquid polymerizable monomer or oligomer to at least a part of a side end surface of the magnetic recording medium, and a step of curing the polymerizable monomer or oligomer. A manufacturing method is also provided.

In the production method of the present invention, a polyfunctional monomer or oligomer, which is a high boiling point liquid and has a photopolymerizable group, is applied to the side end surface of the magnetic recording medium, and then the polyfunctional monomer or oligomer is applied. It is desirable to cure the oligomer by light irradiation (especially UV irradiation).

Further, after a long medium with a magnetic layer is produced by slitting with a predetermined width, a polymerizable monomer or oligomer is applied to the side end surface of the long medium, and the polymerizable monomer or oligomer is cured. It is desirable to wind it after it is made.

In the present invention, it is desirable that the above-mentioned conditions from coating to light irradiation are as follows. (1) Thickness of photo-cured film (application amount) 0.1 to 0.5 mg / m ² (2) Boiling point of polyfunctional monomer 150 ° C or higher (3) Light (ultraviolet) irradiation energy 100 to 500 mJ / cm ² (4) Light (UV) irradiation time 5-30 seconds

[0012]

EXAMPLES Examples of the present invention will be described below.

1 to 5 show a first embodiment of the present invention. 1 and 2 show an example 1 of the magnetic recording medium (for example, a magnetic tape for video) of the present invention.

In this magnetic tape 1, a magnetic layer 3 is formed on one surface of a non-magnetic support (base film) 2 and a back coat layer 4 is formed on the other surface, and both ends (side end surfaces) in the width direction of the tape are formed. ) Is the one in which protective coatings 5 and 6 of resin are formed according to the present invention.

It should be noted here that the end face on the tape side is sufficiently protected by the resin protective coatings 5 and 6 (particularly, the ultraviolet-cured cured resin coating described later) over substantially the entire length. Even if the tape is made thin, both ends in the width direction have high strength, and edge breakage or breakage no longer occurs due to guide regulation or the like.

The protective coatings 5 and 6 are in a state in which the resin has soaked into the end face on the tape side so as to fill up the irregularities and minute recesses, so that the protective coats 5 and 6 do not peel off from the end face on the same side. The reinforcing effect is sufficient. Further, damage is likely to remain on the tape-side end surface during slitting described later, but this damage can also be removed by the protective coatings 5 and 6. In addition,
Since the protective coatings 5 and 6 do not substantially extend onto the surface of the magnetic layer 3, the protective coatings 5 and 6 do not affect the magnetic characteristics or the running property.

As described above, the protective coatings 5 and 6 provide a medium having high durability and high reliability with no dropout, and capable of increasing the recording capacity by reducing the thickness. be able to.

Although various resins can be used as the material of the protective coatings 5 and 6, in particular, polyfunctional monomers or oligomers (acrylic type, urethane type acrylic type, epoxy type, etc., which will be described later) are preferable, and an ultraviolet curing type. The resin obtained by curing (polymerization) is preferable.

In the above, the magnetic layer 3 is made of a binder such as polyurethane or vinyl chloride, Co-γ-Fe ₂ O ₃ or Co.
-In addition to Ni-based magnetic powder, if necessary, a dispersant such as lecithin, a lubricant such as stearic acid ester, an antistatic agent such as carbon black, an abrasive such as alumina, and a rust preventive agent are added. It is a thing. In addition, the back coat layer 4 is
It is mainly composed of non-magnetic powder and a binder. As the base film (nonmagnetic support) 2, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate can be used.

The magnetic tape 1 shown in FIGS. 1 and 2 is produced by applying a magnetic layer or the like to a wide base film by a known method and then slitting.

The above-mentioned magnetic layer, back coat layer, and other medium-constituting layers contain necessary components such as ethers, esters, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, and chlorinated carbons depending on the type of binder. It can be formed by kneading with an organic solvent selected from hydrogen or the like to prepare a coating material, coating the coating material on a non-magnetic support, drying and, if necessary, calendering.

Next, an example of a method of manufacturing the magnetic tape of this embodiment will be described with reference to FIGS.

FIG. 3 shows a so-called pancake winding body 7 formed by winding a long medium with a magnetic layer slitted to a predetermined width in a magnetic tape manufacturing process.
The process of forming the above-mentioned protective film is shown while sequentially unwinding.

First, a method of making the pancake 7 will be described. A magnetic paint having the composition shown below is prepared. Fe-based metal magnetic powder (specific surface area 50 m ² / g) 100 parts by weight Polyester polyurethane (N-2304: manufactured by Nippon Polyurethane Company) 10 parts by weight Vinyl chloride-vinyl acetate copolymer (VAGH: manufactured by UCC) ) 10 parts by weight Carbon black 4 parts by weight Alumina 8 parts by weight Methyl ethyl ketone 150 parts by weight Toluene 70 parts by weight Myristic acid 1 part by weight Butyl stearate 2 parts by weight

After mixing and dispersing the above materials in a sand mill for 4 hours, 4 parts by weight of a curing agent (Coronate L) was added,
It is coated on a polyethylene terephthalate base film having a thickness of 7 μm so as to have a thickness of 3 μm. Next, after drying and calendering, the surface is mirror-finished and then at 60 ℃
Leave in the oven for 20 hours to form a magnetic layer.

Next, 100 parts by weight of carbon black, 100 parts by weight of polyester polyurethane (above), 500 parts by weight of methyl ethyl ketone, and 500 parts by weight of toluene were coated with a ball mill to prepare a coating material for the back coat layer.
After mixing and dispersing for 10 hours, 10 parts by weight of a curing agent (Coronate L) is added and coated on the base film on the side opposite to the above magnetic layer to a thickness of 0.6 μm, and dried to form a back coat layer. Form.

Thus, a wide magnetic tape material having a total thickness of 10.6 μm can be obtained. This is slit into a width of 8 mm and used as a sample magnetic tape. The composition of the magnetic layer and the back coat layer is an example, and the composition is not limited thereto.

After winding the magnetic tape produced as described above into a pancake, as shown in FIG. 3, the magnetic tape 1 is sequentially unwound from the pancake 7 and guided by each guide roller 8. The protective films 5 and 6 described above are continuously formed until the pancake 9 is wound up.

That is, the magnetic tape 1 is attached to a pair of guide rollers.
While passing between 10-11, felt-like applicators 12, 13 were respectively brought into contact with both ends (tape side end surface) in the tape width direction in the region between the guide rollers as shown in FIGS. 4 and 5. In the state, the applicator 12, 13 to the nozzle 14,
Liquid photopolymerizable monomers (or oligomers) 5A and 6A are dropped from 15 by a drip method to sufficiently impregnate these monomer liquids.

As a result, the above-mentioned monomer (or oligomer) liquid is uniformly and continuously applied to the end surface on the tape side by the applicators 12, 13. Immediately thereafter, as shown in FIG. 3, it is placed in an ultraviolet irradiation furnace 16 where the above-mentioned monomer (or oligomer) liquid is irradiated with ultraviolet rays.

In this case, the conditions of coating → ultraviolet irradiation are, for example, as follows. (1) Thickness of UV-cured film (application amount) 0.1 mg / m ² (2) Boiling point of monomer of UV-curable resin Approx. 200 ° C (3) UV irradiation energy 300 mJ / cm ² (by UV lamp) (4) UV irradiation Time 10 seconds

The UV-irradiated monomers (or oligomers) 5A and 6A undergo addition polymerization with the energy and are cured with a sufficient degree of polymerization to become resin coatings 5 and 6 firmly attached to the end surface on the tape side.

As shown schematically in FIG. 1, the resin protective coatings 5 and 6 only need to have a film thickness necessary to uniformly adhere to the tape side end surface, and need not be so thick. In this case, the coatings 5 and 6 are preferably applied to a thickness such that minute irregularities on the cut surface generated during slitting on the tape are filled and damage caused by slitting can be removed.

In the above-mentioned manufacturing method, the photopolymerizable monomer or oligomer used for forming the protective coatings 5 and 6 of the resin is a liquid having a high boiling point (at room temperature) and having a photopolymerizable group. Desirably it is a functional monomer or oligomer. Since such a monomer or oligomer is a liquid in itself, it can be directly applied for coating without a solvent, and drying is also unnecessary.

Further, since this polyfunctional monomer or oligomer is a photopolymerizable one including ultraviolet curing, it can be polymerized without heating, and therefore the base film 2 having poor heat resistance can be used. It doesn't matter at all. Moreover, since the obtained resin coating is made of synthetic resin,
It has good adhesiveness to the magnetic layer 3 and the back coat layer 4 (further, the resin base film 2) using a resin as a binder, and has a high adhesive strength.

Furthermore, in the above-mentioned manufacturing method, the coatings 5 and 6 are formed.
At the time of forming, the tape is sequentially unwound in the state of the pancake 7 and is rewound as the pancake 9, so that the processing can be performed without affecting other lines in the magnetic tape production.

As the above-mentioned polyfunctional monomer or oligomer, the following acrylic type, urethane type acrylic type and epoxy type having the following photopolymerizable groups are preferable.

Photopolymerizable group: name structure ─────────────────────── acryloyl group CH ₂ ═CH—COO-methacryloyl group CH ₂ ═C ( CH ₃₎ -COO - acrylamide group CH ₂ = CH-CONH-

Acrylic: Compound name Structural formula ──────────────────────────────────── ethylene glycol diacrylate CH ₂ = CHCOOCH ₂ CH ₂ OCOCH = CH ₂ polyethylene glycol diacrylate CH ₂ = CHCOO (CH ₂ CH ₂ O) _n COCH = CH ₂ polyethylene glycol dimethacrylate CH ₂ = C (CH ₃ ) COO (CH ₂ CH ₂ O) _n COC (CH ₃ ) ＝ CH ₂

Urethane type acrylic type:

[Chemical 1]

Epoxy type:

[Chemical 2]

Other than this epoxy type, for example, SD-17 (epoxy acrylate / polyfunctional acrylate type oligomer) manufactured by Dainippon Ink and Chemicals, Inc. can be used. This oligomer does not have a boiling point because it heat-polymerizes before reaching the boiling point.

6 to 9 show another embodiment of the present invention. According to the example of FIG. 6, the discharge port of the nozzle 15 for supplying the liquid monomer (or oligomer) shown in FIG. 5 (the same applies to the other nozzle 14) is arranged in contact with the applicator 13. This also allows the applicator to be sufficiently impregnated with the liquid monomer (or oligomer) from the nozzle and then used for coating.

In the example of FIG. 7, one of the applicators 13 (the same applies to the other applicator 12) is provided with a discharge port 25 from the side, and a liquid monomer (or oligomer) supply cylinder 20 is applied to this. Inject the monomer (or oligomer) 6A.
The cylinder 20 is configured to be able to supply a predetermined amount of liquid by moving a piston-type head 21 in the direction of the arrow.

In the case of the magnetic tape 1 of FIG. 8, the resin protective coatings 5 and 6 are applied only to the respective edge portions of the four upper and lower sides, which are particularly susceptible to damage, on both sides of the tape. Even with this, even if the thickness of the tape is reduced, the strength of the end surface on the tape side can be improved and edge breakage or the like can be effectively prevented. In order to locally form the protective coatings 5 and 6 on the edge portion, the coating method may be changed, such as dividing the above-mentioned applicator.

Unlike the example of FIG. 3 described above, FIG. 9 shows that protective films 5 and 6 of resin are formed on the end surface on the tape side before winding on a pancake after slitting.

The outline of the magnetic tape slitting step and the subsequent winding step (step of forming pancake) will be explained. The magnetic tape material 1A wound around the feeding hub 61 is fed with a pair of feeding rolls 63A and 63B. A slitter 65A that is rotated in a direction indicated by an arrow at a predetermined speed by a transport mechanism 62 that is in contact with and rotates while slightly overlapping each other.
The magnetic tape 1 is cut into a predetermined width by a mechanism 64 composed of 65B.

The pair of guide rollers 66, 66 divides the conveying directions of the magnetic tapes 1 and 1 which are adjacent to each other, and they are conveyed by the nip rolls 67, 68 and 67, 68, respectively, and wound on the winding hubs 71, 71, respectively. Pancakes 7 and 7. A predetermined tension is applied to the magnetic tape material 1A and the magnetic tape 1 between the guide rollers 66, 66 and the transport mechanism 62 by the nip rolls 67, 68 and 67, 68 so that the slitting can be smoothly performed. is there.

Immediately after slitting, between the guide rollers 66 and 66 and the nip rolls 67, 68 and 67, 68, the liquid monomer (or oligomer) applicators 12, 13 similar to those shown in FIG. 3 are respectively provided. And 12, 13 and the subsequent ultraviolet irradiation furnaces 16 and 16 are sequentially arranged.

Therefore, immediately before slitting, before forming the pancake 7, the liquid side monomer (or oligomer) for the resin coating is applied to the end surface on the tape side as described above, and further, this is UV-cured, and after that, it is cured. Can be rolled up as a pancake.

According to this example, the same operation and effect as in the above-described example can be obtained, and since the resin film can be formed between the slitting mechanism 64 and the pancake 7, continuous operation is possible, and the production is improved. It improves the sex.

Although the present invention has been illustrated above, the above-described embodiments can be further modified based on the technical idea of the present invention.

For example, the range of formation of the resin film formed on the end face on the tape side may be changed, and also in the molding method, the method of applying and curing the monomer and the type of the monomer (or oligomer) may be variously changed. You may The light applied for curing may be other than ultraviolet light, and may be based on other methods such as electron beam curing. Further, the applicator can be made of a material other than felt.

Further, in the above example, the curing was performed after slitting and before being wound on the pancake, but it can be performed in another process. When the medium is not tape,
It can also be done as a product.

[0055]

As described above, according to the present invention, at least a part of the side end surface of the medium is coated with the resin, so that the strength of the side end surface becomes large even if the medium is thinned.
No longer causes edge breakage or destruction. In this case, the above resin is in a state of being soaked as to fill the unevenness and the minute recesses with respect to the end face on the medium side.
It does not peel off from the end face on the same side, and its reinforcing action is sufficient.

In this way, it is possible to provide a medium which has good durability and is free from dropouts and which has a large storage capacity by thinning.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view in a width direction showing a structure of a magnetic tape according to an embodiment of the present invention (a sectional view taken along line I-I of FIG. 2).
(However, the size is exaggerated in the tape thickness direction.).

FIG. 2 is a perspective view of a part of the magnetic tape.

FIG. 3 is a schematic view of a step of forming a resin protective coating on a side end surface of the magnetic tape.

FIG. 4 is a main part plan view showing a supply means of a polymerizable monomer used for forming the protective film.

FIG. 5 is a perspective view showing the supply means.

FIG. 6 is a side view showing a means for supplying a polymerizable monomer according to another embodiment of the present invention.

FIG. 7 is a front view showing a means for supplying a polymerizable monomer according to another embodiment of the present invention.

FIG. 8 is an enlarged sectional view similar to FIG. 1, showing a structure of a magnetic tape according to another embodiment of the present invention.

FIG. 9 is a schematic view of a process of forming a resin protective coating on a side end surface of a magnetic tape in still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic tape 2 ... Non-magnetic support body (base film) 3 ... Magnetic layer 4 ... Back coat layer 5, 6 ... Resin protective coating 5A, 6A ... Liquid monomer 7 , 9 ... Pancake 10, 11 ... Guide roller 12, 13 ... Applicator 14, 15 ... Nozzle 16 ... UV irradiation furnace

Claims (5)

[Claims] 1. A magnetic recording medium in which a resin is adhered to at least a part of a side end surface. 2. The magnetic recording medium according to claim 1, wherein the side end surface is coated with a photo-cured resin. 3. A method of manufacturing a magnetic recording medium, comprising: a step of applying a liquid polymerizable monomer or oligomer to at least a part of a side end surface of the magnetic recording medium; and a step of curing the polymerizable monomer or oligomer. 4. A polyfunctional monomer or oligomer which is a high boiling point liquid and has a photopolymerizable group is applied to the side end surface of a magnetic recording medium, and the polyfunctional monomer or oligomer is cured by irradiation with light. The manufacturing method according to claim 3. 5. A long medium having a magnetic layer is produced by slitting with a predetermined width, a side surface of the long medium is coated with a polymerizable monomer or oligomer, and the polymerizable monomer or oligomer is cured. The manufacturing method according to claim 3, wherein the manufacturing method is performed and then wound.