JPH03102623A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce contamination in the production process such as that of a roll by incorporating aluminum, silicon, and phosphorus into magnetic powder and specifying the amt. of phosphorus to 0.3 - 0.8wt.% to iron. CONSTITUTION:The medium consists of a nonmagnetic supporting body 1 such as polyethylene terephthalate, magnetic layer 2 formed on the supporting body, and if required, a back coating layer 3 provided on the opposite side to the magnetic layer 2. The magnetic powder used for the magnetic layer 2 contains aluminum, silicon and phosphorus. Aluminum improves durability of the medium, while silicon increases dispersibility of the magnetic powder. Further, the amt. of phosphorus to be incorporated is specified to 0.3 - 0.8wt.% to iron. Thereby, contamination in the production process such as that of rolles can be reduced.

Description

[Detailed description of the invention] a. INDUSTRIAL APPLICATION FIELD The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

B. BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it.

In the magnetic recording medium manufactured in this manner, when the magnetic paint is applied, dried, and then calendered, a portion of the magnetic layer may adhere to the calendar roll, resulting in roll staining. When such roll stains occur, it is necessary to temporarily stop the process line and clean the roll stains with acetone or the like.

Therefore, although attempts have been made to reduce such contamination in conventional media, the relationship with magnetic powder composition has not been sufficiently studied.

C. OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that can significantly reduce process stains such as the roll stains described above.

2. Structure of the invention and its effects, that is, the present invention provides a magnetic recording medium in which a magnetic layer provided on a non-magnetic support contains magnetic powder, in which the magnetic powder contains aluminum, silicon, and phosphorus. It contains
The content of phosphorus is 0.3% by weight or more, 0.3% by weight or more based on iron.
This relates to a magnetic recording medium characterized in that the content is 8% by weight or less.

According to the present invention, since magnetic powder containing aluminum, silicon, and phosphorus (especially cobalt-containing iron oxide magnetic powder) is used as the magnetic powder of the magnetic layer, the durability of the medium is improved by aluminum. , silicon can improve the dispersibility of magnetic powder. In addition to this, by specifying the phosphorus content to be 0.3 to 0.8% by weight of iron, it was found that process stains such as roll stains were significantly reduced during calendering as described above. That's what I did. The reason for this is not clear, but by setting the phosphorus content within the above range, magnetic powder and binder (
Additives such as binders) and fatty acids may peel off from the magnetic layer,
Seepage is effectively prevented. Phosphorus content is 0.
If the phosphorus content is less than 3% by weight, the magnetic powder and binder will peel off due to too little phosphorus, and if it exceeds 0.8% by weight, the amount of fatty acids adsorbed on the surface of the magnetic powder will decrease, resulting in a decrease in the amount of phosphorus adsorbed onto the surface of the magnetic layer. This is thought to be due to increased seepage of fatty acids.

The phosphorus content should be further 0.5 to 0.8% by weight (
0.5, o,'l weight % is more desirable.

In the present invention, in order to further reduce the above-mentioned process stains, 0.3 to 0.7% by weight of manganese is added to the magnetic powder. Manganese has the effect of reducing flaking of the magnetic powder, and the above-mentioned content range is preferable.

Furthermore, in the above, when the phosphorus content increases, the Young's modulus and Lumie S/N of the magnetic layer tend to decrease.
In order to prevent this, it is preferable to add a small amount of fatty acids (especially those with a melting point of 80° C. or less), especially 2.0% by weight or less based on iron.

In addition, the BET value is large (especially 30rrr/g or more)
When using fine particle magnetic powder, it is desirable to increase the silicon content proportionately as the particles become finer to ensure dispersibility. In this case, the silicon content in the magnetic powder is 2
．． Of! It is preferable to keep it below 0.1 to 1.
More preferably, the content is 2% by weight. The silicon content is 2.
Even if it exceeds 0 Nil%, the effect commensurate with the increase in content may not be achieved, and the magnetic properties may deteriorate on the contrary. The content of aluminum is preferably 0.7% by weight or less of the magnetic powder, and o. oos~0.4
% by weight is more preferred. In order to exhibit the effects of each element, silicon and argonium, at the same time, it is preferable that the silicon/aluminum weight ratio is 3 or more.

In addition, in the above, silicon, aluminum and phosphorus (
Furthermore, "containing" (manganese) also means when it is attached to the surface of the core of the magnetic powder or when it is mixed inside the core.

In order to attach silicon, aluminum, and phosphorus (and even manganese) to magnetic powder, for example, a silicon compound soluble in a dispersion prepared by dispersing magnetic powder in an alkaline aqueous solution,
It can also be carried out quantitatively by adding an aluminum compound, phosphorus or a phosphorus compound (or even a manganese compound). Usable silicon compounds include, for example, orthosilicic acid (01aSiOa), metasilicic acid (}12SiOs
), metanisilicic acid (FlzSizO), metatrisilicate (
H4Sts(1+), metatetrasilicic acid (fl6sid)
+ +); silicon monoxide, silicon dioxide; sodium orthosilicate CNaaSxOa), sodium metasilicate (NaSiO+), potassium metasilicate (
lhsi(h), calcium orthosilicate (Ca4Si
．． 04), calcium metasilicate (CazStCl+)
, barium metasilicate (BazSiO+), cobalt metasilicate (CozSi03), and other silicate metal salts. These silicon compounds may be used alone or in combination of two or more.

In addition, as an aluminum compound that can be used to attach aluminum to magnetic powder, orthoaluminic acid (H
3^1 (owl). ), metaaluminic acid (IIAI
Aluminic acids such as (Olla), sodium orthoaluminate (Na3A1 (OH) b), sodium metaanolemate (NaAl(Off) 4), potassium orthoaluminate (K3Al(0!1) 6), potassium metaaluminate (κAl (011) 4) and the like are mentioned. These may be used alone or in combination of two or more.

Phosphorus compounds that can be used to attach phosphorus to magnetic powder include phosphoric acids such as orthophosphoric acid (l13PO4) and metaphosphoric acid (HPO3), sodium orthophosphate (Na3poa), and sodium metaphosphate (NaPO3).
z), potassium orthophosphate (K3PO4), potassium metaphosphate (KPOi), and other phosphate metal salts. These may be used alone or in combination of two or more. When attaching phosphorus, it is desirable that the particle size of the added phosphorus be in the range of {00 to IOOOA.

Note that sodium manganate (NaJ) is a manganese compound that can be used to attach manganese to magnetic powder.
metal manganates such as potassium manganate (KJnOa) and potassium manganate (KJnOa). These may be used alone or in combination of two or more.

Further, in order to quantitatively mix silicon, aluminum, and phosphorus (furthermore, manganese) into the magnetic powder, a method can be adopted in which the magnetic material is brought into contact with a gas containing silicon, aluminum, and phosphorus (furthermore, manganese). In addition, in the case of magnetic powder obtained by thermal reduction of goethite, treatment with aluminum, silicon, and phosphorus (and even manganese) may be performed during the production or processing stage of the raw goethite, and then this may be reduced. good.

In the above, silicon, aluminum, and phosphorus (and even manganese) are oxides on the surface area of the magnetic powder? is preferably present in the form of a hydrous oxide.

The magnetic powder used in the present invention is 7FezOz, Co
It is iron oxide magnetic powder such as containing rFezOz, Fe=Os, Co-containing Fe■04, and CO-containing TFe
zO3 is preferred. Others: Fe, Ni, CoSFe-
Ni-Co alloy, l'' (B-Ni alloy, Fe-AI2 alloy, Fe-Af-Ni alloy, Fe-Al-Co alloy, F
e-Mn-Zn alloy, Fe-Ni-Zn alloy, Fe-
A/! -Ni-Co alloy, Fe-Al-Ni-
Cr alloy, Fe-Aj2-CoCr alloy, Fe-Co
-Ni-Cr alloy, Fe-Go-Ni-P alloy, Co-
Metal magnetic powder containing mainly Fe, Ni, Co, etc. such as Ni alloy can also be used.

In the magnetic recording medium of the present invention, polyurethane, vinyl chloride resin (vinyl chloride resin consisting of vinyl chloride homopolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer) is used as the binder (binding agent) of the magnetic layer. , copolymer resins such as vinyl chloride-acrylonitrile copolymer), butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives, cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose brobionate, nitro cellulose, etc.), styrene-butadiene copolymers, polyester resins, various synthetic rubbers, phenolic resins, epoxy resins, urea resins, melan resins, phenoxy resins, silicone resins, acrylic reaction resins, high molecular weight polyester resins Examples include mixtures of polyester polyols and isocyanate brevolimers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/isocyanates, and mixtures thereof.

These binders are -So:l M, -COOM,-
Contains a hydrophilic polar group such as PO (OM' )z (where M is hydrogen or an alkali metal such as lithium, potassium, or sodium, and M' is a hydrocarbon residue or an alkali metal such as hydrogen, lithium, potassium, or sodium). It is best to use a resin that has a high temperature. In other words, the polar groups in the molecules of these resins improve their compatibility with the magnetic powder, which further improves the dispersibility of the magnetic powder and prevents agglomeration of the magnetic powder, further improving the stability of the coating liquid. Therefore, the electromagnetic conversion characteristics and durability of the medium can be improved.

In particular, a vinyl chloride copolymer can be obtained by copolymerizing a vinyl chloride monomer, a copolymerizable monomer containing an alkali salt of sulfonic acid or phosphoric acid, and, if necessary, other copolymerizable monomers. Since this copolymer is based on vinyl coalescence, it is easy to synthesize, and various copolymerization fractions can be selected, allowing the properties of the copolymer to be optimally adjusted.

The metal of the above-mentioned salt of sulfonic acid or phosphoric acid is an alkali metal (especially sodium, potassium, lithium), and potassium is particularly preferred in terms of solubility, reactivity, yield, etc.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
It has a magnetic layer 2 on a non-magnetic support 1 such as polyethylene terephthalate, and if necessary, a BC layer 3 is provided on the opposite side of the magnetic layer 2. Also,
As shown in FIG. 2, the magnetic layer 2 of the magnetic recording medium of FIG.
An overcoat layer (OC layer) 8 may be provided thereon.

In addition to the above, the magnetic layer 2 contains lubricants (such as silicone oil, graphite, molybdenum disulfide, tungsten disulfide, and monobasic fatty acids having 12 to 20 carbon atoms).
(e.g., stearic acid), fatty acid esters having a total of 13 to 40 carbon atoms, etc.), abrasives (e.g., fused alumina), antistatic agents (e.g., carbon black, graphite),
A dispersing agent (for example, powdered lecithin, phosphate ester), etc. may be added.

Further, the magnetic recording media shown in FIGS. 1 and 2 may be provided with an undercoat layer (not shown) between the magnetic layer 2 and the support 1, or may be provided with no undercoat layer. It's okay. Further, the support may be subjected to corona discharge treatment.

Further, when providing the back coat layer 3, the above-described binder contains non-magnetic particles such as halium sulfate and is applied to the back surface of the support.

Further, as the material of the support 1, plastics such as polyethylene terephthalate and polypropylene, AA
, Zn and other metals, glass, BN, Si carbide, porcelain, ceramics such as earthenware, etc. are used.

Further, as shown in FIG. 3, the magnetic recording medium of the present invention has the following features:
On the non-magnetic support 1, a first magnetic layer 4, a second magnetic layer N5
may be stacked in this order. The example in Figure 5 is
The upper layer is further divided into N6 and N7.

In the magnetic recording media of FIGS. 3 and 4, the thickness of the first magnetic layer 4 is preferably 1.5 to 4.0 μm.
The thickness of the second magnetic layer 5 or the second and third magnetic layers 6 and 7
It is preferable that the total film thickness is 0.6 μm or less (for example, 0.5 μm).

When the magnetic layer is composed of a plurality of layers as shown in FIGS. 3 and 4, the layer containing the magnetic powder according to the present invention may be the uppermost layer 5 or 7; 6, or may be contained in any one of a plurality of layers or at least IN. The composition of these multiple layers may be the same as that of the magnetic layer 2 described above. However, in addition to cases in which there is substantially a clear boundary between each layer, there may also be a boundary area where magnetic powder from both layers coexists at a certain thickness. The removed upper or lower layer is the above-mentioned upper or lower layer.

In the above structure, the upper layer of the plurality of magnetic layers has good high-frequency recording and playback characteristics such as video output, and the lower layer has relatively low-frequency recording and reproduction characteristics such as chroma and audio output.
Each layer can be shaped to provide good reproduction characteristics. For this purpose, it is generally necessary that the coercive force (Hc) of the upper N (especially the uppermost N) be larger than that of the lower layer, and that the film thickness (or layer thickness) of the upper layer be thin, especially 0.6 μm or less. It is desirable to do so. Also, the thickness of the lower layer adjacent to this upper layer is l. It is desirable to set it as 5-4.0 micrometers.

Ho. Example Examples of the present invention will be described below.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention. In addition, in the following examples, all "parts" are parts by weight.

First, the compositions shown below were kneaded and dispersed using a sand mill to prepare magnetic paints.

Cor FetO3 100 parts PVC copolymer 10 parts Polyurethane resin 7 parts α-Aj2,
0.7 parts stearic acid
1 part putyl stearate
1 part cyclohexanone
200 parts methyl ethyl ketone
200 parts toluene 1
00 parts Carbon black I part Polyisocyanate 3 parts Note)
In the above, Co 1 FezO3 is Co-containing (or deposited) γ-FezO, and its Af content is 0.04% by weight, its Si content is 0.2% by weight, and its P and Mn contents are It is described in Tables IA to IC below.

PVC copolymer is vinyl chloride-vinyl acetate copolymer (VA
GH: U. C. In the structural formula, the polyurethane resin is polyurethane (referred to as polyurethane A), and the polyisocyanate is Coronate L (manufactured by Nippon Polyurethane Co., Ltd.).

The magnetic powder used above is as follows.

That is, untreated Co-containing 7-Fe,03 magnetic powder (Co
Content 2.5% by weight, needle ratio 9) was suspended in an aqueous NaOH solution, and Na 4S i 0 4 , Na
A I (011) a, and N a Z M n
．． 04 aqueous solution and phosphorus powder are added, and while stirring well, carbon dioxide gas is blown into the suspension to neutralize it, and silicon oxide, aluminum oxide, manganese oxide, and phosphorus are formed on the surface of the magnetic powder. A film was formed. After washing this magnetic powder with water, it was dried at a predetermined drying temperature for a predetermined time. As the magnetic powder, Na. Si○4, Na3 AfO3
Specify the concentration and amount of the aqueous solution and check the above St, AI! ．． Magnetic powders having the P and Mn contents shown in Tables 1A to 1C were obtained.

The above magnetic paints were extruded using an extrusion coater and applied onto a polyethylene terephthalate base with a thickness of 14 μm to a dry thickness of 4.0 μm. After orientation and drying treatment, supercalender treatment was performed. provided.

Thereafter, the following back coat paints were applied to the opposite side of the magnetic layer to a dry thickness of 1.0 μm.

Carbon black (average particle size 20 mμ) 40 parts Carbon plaque (average particle size 300 mμ) 5 parts Nitrocellulose 25 parts (Cellnova BTHV2 manufactured by Asahi Kasei Co., Ltd.) N-2301 (manufactured by Nippon Polyurethane Co., Ltd.) 25 parts Coronet L (Japan Polyurethane Co., Ltd.) ) 10 parts xanone 400 parts methyl ethyl ketone
250 parts toluene
250 copies of a wide magnetic film were thus obtained and wound up. This film was cut into 2-inch widths to make each videotape. The following performance evaluations were performed on each of these tapes, and the results are shown in Tables IA to IC. In the following, "actual" represents an example, and "ratio" represents a comparative example.

(a) Process soiling test: In the above tape manufacturing process, the degree of soiling of the calender roll used for calendering was visually observed.

XX: Lots of dirt ×Δ: Slightly dirty ΔΔ: Some dirt Δ○: Almost no dirt ○○: No dirt at all (b) Lumie S/N: Color video noise meter rShibasoku92
5 D/IJ, rHRS manufactured by Victor Japan Co., Ltd.
It is expressed as a value (dB) with respect to a reference tape (manufactured by Konica) using a 7000 J deck.

(The following is a blank space) Table 1B Next, the compositions shown below were kneaded and dispersed using a kneader and a sand mill to prepare magnetic paints.

<Magnetic paint A for upper layer> Co-T-Fez 03 100 parts (Hc=9000e, BET value 45 n{/g, average major axis length 0.2 μm) Potassium sulfonate-containing PVC resin 10 parts (MR
IIO, Nippon Zeon (manufactured by lko) polyurekne resin
5 parts (polyurethane A described above) a-Affi. 03 (average particle size 0.2μm)
Part 6 Carbon foil 1
1 part myristic acid 1 part stearic acid 1 part butyl stearate 1 part coronate
Part 5 (Japan Polyurethane Industry 1
(Made by M) (Magnetic paint B for lower layer) Co-1-Fe.03100 parts (H c =700 0 e, B ET value 28 n {/
g, average major axis length 0.25 μm) 10 parts of PVC resin containing potassium sulfonate (MR
IIO, manufactured by Nippon Zeon ■) Polyurethane resin 5 parts (the above mentioned, manufactured by Takeda Pharmaceutical Co., Ltd.) Myristic acid 1 part Stearic acid 1 part Butylstearate 1 part Coronate
5 parts (manufactured by Nippon Polyurethane Industries ■) Next, on a polyethylene terephthalate base film with a thickness of 14.5 μm, various types of magnetic paint B for the lower layer and magnetic paint A for the upper layer were applied sequentially using an extrusion coater, and after orientation and drying. , calendar processing was performed.

In this case, the dry film thickness was 0.3 μm for the upper layer and 2.0 μm for the lower layer.

Thereafter, the next set of paints for the BC layer was applied to the surface opposite to the magnetic layer to a dry thickness of 0.4 μm.

Carbon black (Ravenl035)
40 parts barium sulfate (average particle size 300 mμm)
10 parts Nitrocellulose 25
Part N-2301 (made by Nippon Polyurethane) 25 parts Coronate L (〃) 10 parts Cyclohexanone 400 parts Methyl ethyl Katone 250 parts Toluene
250 copies of a wide magnetic film was thus obtained and wound up. This film was cut into % inch widths to produce video tapes shown in Tables 2A to 2c below.

In addition, as for the magnetic powder used above, for the upper magnetic layer or the lower magnetic layer,... The content is 0.04% by weight, the Si content is 0.2% by weight, and the P and Mn contents are in Table 2A below.
- The one described in 2c was used.

Note that the other magnetic layers have a /l content of 0.04% by weight, St
The content was 0.2% by weight, and the P and Mn contents were each 0% by weight.

(The following are blank spaces) Table 2A Table 2B Table 2C From the above results, it can be seen that the process staining is low when the P content is 0.3 to 0.8 wt% based on Fe. Among them, it is also found that in order to further reduce process stains, the Mn content may be adjusted to 0.3 to 0.7 wt%.

The process stain test was performed when the magnetic layer was a single layer (Table IA
~IC), when in the upper layer or when in the lower layer (Tables 2A to 2C)
), but there was no change in their effectiveness. In other words, irrespective of whether the magnetic layer is a multilayer or a single layer, if at least one layer is applied, it is effective in reducing process contamination.

In the case of multiple layers, even better results can be expected if the magnetic powder of the present invention is used in both layers.

However, as the P content increases, Young's modulus and Lumie S/
There is a tendency for N to decrease. Young's modulus is at least 4°50kg
/ Sir 2, Lugo - It is desirable that the S/N be at least 45 dB as a characteristic of the tape. Therefore, in order to suppress the decline in Young's modulus, it is necessary to reduce the amount of fatty acids added.
In order to improve the electrical properties, we considered using a binder with functional groups. The results are shown in Table 3 below and Figure 5. The samples used were the same as in Example 34, except that the amount of fatty acid and the type of binder were changed.

(Left below) However, the P content of the magnetic powder is 0.79wt%, and the P average particle size is 986. Fatty acid melting point: 80°C or less. The binder is a vinyl chloride resin (such as the above-mentioned MR110).

From this result, in order to satisfy the Young's modulus of 450 kg/mm2 or more, it is desirable that the amount of fatty acid added be 2.0% or less based on the magnetic powder. The fatty acid melting point at this time is 80°C or less. Also, -So. A binder with a functional group such as K, -P○, or K is effective in improving electrical characteristics, and by using this, the Lumie S/N can be maintained at 45 dB or more.

[Brief explanation of drawings]

The drawings are for illustratively explaining the present invention, and FIGS. 1, 2, 3, and 4 are cross-sectional views of four examples of magnetic recording media, and FIG. 5 is a cross-sectional view of four examples of a magnetic recording medium. It is a graph showing changes in characteristics when the amount added is changed. In addition, in the symbols shown in the drawings, 1...Nonmagnetic support 2...Magnetic layer 3...Back coat layer 4... . . . Lower N magnetic layer 5, 7 . . . Upper magnetic layer 6 . . . Intermediate magnetic layer.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic layer provided on a non-magnetic support contains magnetic powder, the magnetic powder contains aluminum, silicon, and phosphorus, and the content of phosphorus is equal to that of iron. A magnetic recording medium characterized in that the content is 0.3% by weight or more and 0.8% by weight or less.