JPS62154227A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape having excellent durability without troubles in the physical properties of the film, unstable traveling under high-temp. and high-humidity conditions, damages of a guide, and troubles in electromagnetic transduction by specifying the surface roughness of a magnetic layer, and incorporating barium carbonate into a backcoat layer to specify the surface roughness. CONSTITUTION:In the magnetic recording medium having the magnetic layer on one surface of a carrier and the backcoat layer contg. a binder and nonmagnetic powder and having <=1.5mum thickness on the other surface of the carrier, the surface roughness (Ra) of the magnetic layer is controlled to <=0.02mum average roughness (Ra) at the cutoff 0.25mm center line. Barium carbonate having 0.01-0.8mum average particle diameter is incorporated in the backcoat layer as the nonmagnetic powder, and the surface roughness (Ra) is adjusted to <=0.05mum at the cutoff 0.25mm center line. The thickness of the backcoat layer is limited to <=0.15mum, or preferably to 0.3-1.2mum, to control the phenomenon such as cupping.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to magnetic recording media, and in particular to magnetic tape.

BACKGROUND OF THE INVENTION Magnetic recording media such as magnetic tapes, magnetic tapes, and magnetic disks are widely used in the audio, video, and computer fields. Among these, for example, regarding magnetic tape in the video field, magnetic tape stored in a cassette is used to record and play back images.
This cassette is mounted on a video deck, and the tape travels along a route while its front and back sides are rubbed by guide poles and guide rollers, and is rubbed and scanned by a magnetic head.

The surface of the magnetic layer is finished to be smooth so that the sliding condition of the magnetic tape against the magnetic head does not change when the magnetic tape runs on a circuit.

However, the other side of the magnetic layer of the magnetic tape has a similar effect on the above fluctuations, and when the running performance and durability of the other side are poor, excessive tension is applied to the running magnetic tape, causing damage to the magnetic layer. Not only does powder drop occur, but the winding shape is disturbed and the edges of the tape become uneven, resulting in poor image or electromagnetic conversion characteristics such as skew, jitter, and chroma S/N.

Therefore, a bank coat layer is provided on the back side of the magnetic tape support to improve running properties and durability against guide poles, guide rolls, guide pins, etc., and this back coat layer contains non-magnetic There is one in which the layer contains inorganic powder as a filler. This is a method in which the surface of the back coat layer is roughened to reduce the contact area with guide poles, etc., and to reduce the frictional resistance.
No. 1135, No. 57-53825, No. 58-2415
No. 50-3927 all show examples using inorganic powders, and many of these also show those with limited particle sizes. However, even those using these inorganic powders not only do not provide sufficient smoothness, but also cause the bank coat layer to come into contact with guide pins, etc., as in the case of the alumina particles described in Japanese Patent Publication No. 50-3927. When doing so, especially when the guide pin etc. is an organic resin member, the pin etc. will be scraped, impairing the function of the guide pin to smoothly guide and run the magnetic tape.

One of these causes is that inorganic powders generally have a wide variety of particle shapes and are not constant, and also have a wide distribution of particle sizes, which causes the surface of the back coat layer to become rougher than necessary.

From this, for example, measures can be taken such as setting the center line average roughness Ra of the surface roughness of the back coat layer to 0.010 to 0.050 μm and the dynamic friction coefficient μ from 0.10 to 0.36. It is necessary to improve the runnability and durability of the back coat layer without imprinting irregularities on the magnetic layer.

In addition, since inorganic powder has a relatively strong affinity for water, it absorbs moisture in the air during use, and the surface of the back coat layer tends to stick to guide poles, etc., and the adhesion causes the running magnetic tape to suddenly Places where stopping and sudden starts are repeated 311 Stick-slip is likely to occur. Further, the moisture may change the quality of the magnetic powder, resulting in deterioration of performance.

Further, the solid powder filler such as the above-mentioned inorganic powder must be contained in the back coat layer etc. in a sufficiently well dispersed state. Therefore, the fillers used are required to have good dispersibility.

In particular, the recent miniaturization and high density of video equipment has made the route of the magnetic tape more complicated, and the guide poles, guide rolls, and Iζ of this tape have more opportunities to come into contact with magnetic heads, etc., and are more likely to be rubbed. There is a need for improvements in running performance, wear resistance to prevent powder falling, etc., and durability.

(Objectives of the Invention) The objects of the present invention are (1) good M physical properties, (2) no interlayer adhesion, (3) good filler retention and uniform dispersion, and (4) repeated running. (4) has a back coat layer with good paint stability, and magnetic recording that does not cause problems with film properties, unstable running at high temperatures and high humidity, damage to tape or video deck guides, and electromagnetic conversion failures. The objective is to provide a medium (hereinafter referred to as magnetic tape).

(Structure of the Invention) The object of the present invention is to provide a back coat layer having a magnetic layer on one side of a support, and a back coat layer having a thickness of 1.5 μm or less containing a binder and non-magnetic powder on the other side of the support. In a magnetic recording medium having a magnetic layer, the surface roughness (Ra) of the magnetic layer is
Off 0.25 center line average roughness (rLa) is cut off 0.25 *vt center line average roughness (Ra) 0.02
μm or less, and the bank coat layer contains barium carbonate with an average particle size of 0.01 to 0.8 μm as the nonmagnetic powder, and the surface roughness (Ra) is a center line average of about 0.25 μm. This can be achieved by a magnetic recording medium characterized by a roughness (Ra) of 0.05 μm or less.

Next, the present invention will be explained in detail.

The magnetic layer according to the present invention has a center line average roughness R, a with a cutoff of 0.25 mm in surface roughness in order to improve surface properties such as smoothness and retention of magnetic powder, and electromagnetic conversion characteristics. )
is 0.02 μm or less, preferably 0.02 to 0,
OOlnm is particularly preferably 0.015 to 0.001.

Moreover, barium carbonate is selected as the non-magnetic powder contained in the back coat layer according to the present invention, taking into consideration its solubility, chemical stability, hardness, and cost.

The average particle size of the barium carbonate is 0.01 to 0.8 μm, and if it is larger than 0.08 μm, the surface roughness becomes excessive, and the roughness is transferred to the magnetic layer and deteriorates the electromagnetic conversion characteristics. If it is smaller, the degree of surface roughening will be too small and the frictional resistance will increase, causing problems in running performance and often causing nching (local loosening of the winding) when starting or stopping suddenly.

In addition, when the thickness of the back coat layer exceeds 5 μm, force and pinging phenomenon occurs that causes spiral curling in the longitudinal direction, causing trouble in contact with the head, deteriorating electromagnetic conversion characteristics, and further causing nitching. There are many things.

In the present invention, in order to suppress phenomena such as cupping, the film thickness is reduced to 1.
．． Keep it below 5 μ tu, preferably 0.3 to 1.2 tu
Let it be g.

Furthermore, the surface roughness of the back coat layer was adjusted to 0.
The center line average roughness (rLa) is suppressed to less than O,OS μm to improve the surface properties and suppress the transfer of the roughness of the bank coat layer to the magnetic layer, but preferably (Ra) is 0015 to 0.25.
0.0571111. Particularly preferably 0.02 to 0.0
Good electromagnetic conversion characteristics can be obtained in the range of 45 am.

In the present invention, an organic powder can be used in combination with the barium carbonate according to the present invention as the non-magnetic powder.

The organic powder is preferably acrylic styrene resin, penzoquanamine resin powder, melamine resin powder, or phthalocyanine pigment, but polyolefin resin powder, polyester resin powder, polyamide resin powder,
Polyimide resin powder, polyfluoroethylene resin powder, etc. can also be used.

In particular, benzoguanamine-based and/or melamine-based resins are preferred for use in combination with barium carbonate.

Furthermore, inorganic powders used in combination with the barium carbonate powder according to the present invention include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, chromium oxide, silicon carbide, calcium carbide, α-F e
203s Talc, kaolin, calcium sulfate, zinc sulfate, boron nitride, zinc fluoride, magnesium hydroxide, aluminum hydroxide, and molybdenum dioxide.

The filler content in the back coat layer is 0.2 to 0.9, preferably 0.4 to 0.85 of the total solid weight.

In the present invention, carbon black may be added to the magnetic layer and the back coat layer to impart conductivity and light shielding properties.

By dividing the carbon black into the two layers and adding C, it is possible to avoid the difficulty in dispersing the carbon black and provide sufficient light-shielding properties.

The carbon black to be mixed in the magnetic layer and the back coat layer is preferably one in which the particles are connected like a cluster of grapes, and is porous and has a large specific surface area, for the purpose of improving conductivity. so-called straphtia
A high level is desirable.

Examples of such carbon blanks include Fundactex (Co-nducte) manufactured by Columbia Carbon Co., Ltd.
x) 975 (specific surface area 270 m/g, particle size 24 mμ
), Condactex 950 (specific surface area 245 m'/
g, particle size 46 mB), Cabot Palcan (Cabo
tVulcan) XC-72 (specific surface area 257 m'/
g, particle size 30 mμ), etc. can be used.

On the other hand, as light-shielding carbon black, carbon black with small particle size, relatively low stracture level, and relatively low specific surface area is used, such as Reven 2000 (specific surface area: 1 s Oz) manufactured by Columbia Carbon Co., Ltd.
'/ g s particle size 19 mμ), 430.420.14.
2100.1170, 1000.1255.1250.
3200.3500.5000.5250°550.
7000; #30, #35, #4 manufactured by Mitsubishi Kasei Corporation
0, #44, ##75, #1001 #970, #100
0, +2200, #2350, #2400, MA
7, MA8, MAII, MAloo: Cabot Black Pearl 700.800.1100.1300
, L1 Legal 4QO1500, 660, etc. can be used.

Further, in the present invention, it is preferable that the pH is 7 or less, which provides good uniform dispersibility.

The carbon black having a pH of 7 or less is manufactured by Columbia Carbon Co., Ltd.; Raven 1000.1170.1250.1255.2
000.3200.3500.5000.5250.5
750.7000, Fundactex 975, manufactured by Cabot; Black Pearl 1000.1100.1300. L1
Manufactured by Mitsubishi Kasei Corporation; #1OO1#970, #1000, +2200B,
#2350. #: 2400B, MA7, MA8, M
Examples include AII, MAloo, and the like.

In the present invention, conventional techniques can be used to create the magnetic tape of the present invention.

As the binder used in the magnetic tape constituent layers such as the magnetic layer and the back coat layer according to the present invention, abrasion-resistant polyurethane can be mentioned. It has strong adhesion to other substances, is mechanically strong by withstanding repeated stress or bending, and has good abrasion resistance and weather resistance.

Furthermore, if a cellulose resin and a vinyl chloride copolymer are also contained in addition to polyurethane, the dispersibility of the filler in the constituent layers will be improved and the mechanical strength thereof will be increased. However, if only the cellulose resin and the vinyl chloride copolymer are used, the layer becomes too hard, but this can be prevented by containing the above-mentioned polyurethane.

Usable cellulose resins include cellulose ether, cellulose inorganic acid ester, cellulose organic acid ester, and the like. The vinyl chloride copolymer described above may be partially hydrolyzed. Preferable examples of the vinyl chloride copolymer include copolymers containing vinyl chloride and vinyl acetate.

Phenoxy resins can also be used.

Phenoxy resin has advantages such as high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, chemical resistance, and good adhesiveness.

These binders have mutually complementary strengths and weaknesses, and can significantly improve the stability of tape physical properties over time.

Furthermore, in addition to the binders described above, mixtures of thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used.

Among the binders, a combination of polyurethane resin and cellulose resin, particularly nitrocellulose, is preferred as the resin used for the back coat layer. The mixing weight ratio of both is 9/1 to 2/8, preferably 8/2 to 3/7, based on polyurethane as a molecule.

In the present invention, polyisocyanate can be included as a curing agent in the binder.

Aromatic polyisocyanates that can be used include, for example, tolylene diisocyanate (TDI) and adducts of these polyisocyanates and active hydrogen compounds, and those having an average molecular weight of 100 to 3,000 are suitable.

Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (HMDI) and adducts of these incyanates and active hydrogen compounds. Among these aliphatic polyisocyanates and adducts of these polyisocyanates and active hydrogen compounds,
Preferably, the molecular weight is in the range of 100 to 3,000. Among the aliphatic polyisocyanates, non-alicyclic polyisocyanates and adducts of these compounds and active hydrogen compounds are preferred.

The amount of the polyisocyanate added to the binder is from 0.1 to 0.7, particularly preferably from 0.15 to 0.5, based on the sum of their weights.

The coating material used to form the above-mentioned constituent layers may contain additives such as a dispersant, a lubricant, and an antistatic agent, if necessary.

Examples of dispersants used in the constituent layers of the present invention include lecithin, phosphoric acid esters, amine compounds, alkyl sulfates, fatty acid amides, and higher alcohols. f? lJ ethylene oxide, sulfoconoctate, sulfosuccinic acid ester, known surfactants, and salts thereof,
Also, negative organic groups (e.g. -COOHl-PO,H)
It is also possible to use salts of polymeric dispersants having .

These dispersants may be used alone or in combination of two or more. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder.

In addition, lubricants include silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, fatty acids such as lauric acid, palmitic acid, oleic acid, stearic acid, behenic acid, myristic acid, and butyl stearate. , octyl palmitate, octyl myritate, and other fatty acid esters can also be used. These lubricants are added in an amount of 0.02 to 20 parts by weight per 100 parts by weight of the binder.

Antistatic agents include carbon blank, conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds, natural surfactants such as saponin, and alkylene oxides. Non-ionic surfactants such as polyester, glycerin, and glycidol; carton surfactants such as higher alkyl amines, quaternary ammonium salts, pyridine, other heterocycles, phosphonium or sulfonium; carboxylic acid, sulfonic acid , phosphoric acid, sulfuric acid ester groups, anionic surfactants containing acidic groups such as phosphoric ester groups; bifacial active agents such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric esters of amino alcohols, and the like.

The magnetic layer according to the present invention may be a coated magnetic layer using a magnetic paint made of magnetic powder, a binder, a dispersant, a lubricant, etc., or may be a coated magnetic layer using a vapor deposition method, a sputtering method, a paper deposition method, etc. It may also be a thin film type magnetic layer formed by.

Examples of magnetic materials include r-F”e203, Co-containing r-Fe2O3, Co-coated r-Pe203, Fe5
0<, Co-containing Fe3O4, Co-coated Pe304. Cr
Oxide magnetic materials such as O2, e.g. Fe, Ni, Co,
Fe-Ni alloy, F'e-Co alloy, re N1-
P alloy, Fe-Ni-Co alloy, Fe Mn-Zn
alloy, Fe-Ni-Zn alloy, FeCoNi
-Cr alloy, Fe -Co -Ni-P alloy, Co-N
i alloy, Co-P alloy, Co-Cr alloy, etc. Fe, Ni
, and various ferromagnetic materials such as metal magnetic powder containing Co as a main component. Additives to these metal magnetic materials include Sl, Cu, Zn, Al, p, Mn, Cr.
It may contain elements such as or compounds thereof.

Hexagonal ferrite such as barium ferrite and iron nitride are also used.

Furthermore, an abrasive can be added if necessary. The polishing agent is commonly used materials such as fused alumina,
Silicon carbide, chromium oxide, furundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. are used. These abrasives have an average particle size of O, OS to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are used in an amount of 1 to 2 parts by weight per 100 parts by weight of the binder.
It is added in an amount of 0 parts by weight.

Solvents blended in the above back coat and magnetic paint or diluting solvents during application of this paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, furopanol, and phthanol; acetic acid. methyl,
Esters such as ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol monoacetate; Ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, and tetrahydrofuran; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride (7) Halogenated hydrocarbons such as , ethylene chloride, carbon tetrachloride, chloroform, dichlorobenzene, etc. can be used.

In addition, as a support, polyethylene terephthalate,
Examples include polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarboate; metals such as Cu, 11% Zn, etc.
Ceramics such as glass, BN, Si carbide, porcelain, and ceramics can also be used.

The thickness of these supports is about 3 to ioo μm in the case of a film or sheet, preferably 5 to 50 μm,
In the case of a disk or card shape, the diameter is about 30 μm to 10 μm, and in the case of a drum shape, a cylindrical shape is used, and the shape is determined depending on the refuder used.

An intermediate layer for improving adhesion may be provided between the support and the back coat layer or magnetic layer.

The coating method for forming the above layer on the support is as follows:
Air doctor coat, blade coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure coat,
A kiss coat, a cast coat, a spray coat, etc. can be used, but are not limited to these.

(Example) The present invention will be specifically explained using examples.

Examples 1 to 4 The composition of the following magnetic coating formulation I was sufficiently mixed and dispersed in a ball mill, 5 parts of polyfunctional incyanate was added as a hardening agent, filtered through a 1 μm filter, and applied to a polyethylene terephthalate base having a thickness of 15 μm. A sample film was obtained by coating with a reverse roll coater 9 so that the dry film thickness was 4.5 μm. The film was subjected to supercalender treatment.

Next, the composition of back coat paint formulation (1), which was different for each sample shown in Table 1, was dispersed in a ball mill for 5 hours to obtain a bank coat paint for each sample. The paint was applied to the back side of the sample film using a reverse roll coater to a dry film thickness of 0.5 μm, and dried to form a back coat layer on each side.
Example sample tapes 1 to 4 and Comparative example sample tapes (1) and (4) were obtained by applying rinsing 1 to a 2-inch width.

Magnetic paint formulation 1 (parts by weight) containing Co'
FE2E3100 polyurethane 12 PVC one vinegar bee co -polymer 8 stearate boutills 08 millistic acid 08 millistic acid 5 carbon braced 5 carbon brazuku 5 lecithin 100 methyl ethyl ketone 5 ° Toruene 10 Batsuku coat prescription ■ Table 1] ] (Note) In parentheses The numerical value indicates the average particle size.

The sample obtained as described above was tested for the first time (0-pass, virgin tape) and after 200 repeated runs (200
- The tape conditions, physical properties, and electromagnetic conversion characteristics of the tape (Pass) were checked, and the results are listed in Table-2. The surface roughness of the back coat layer was adjusted by adjusting the dispersion time. Moreover, BC in the table means a back coat layer.

2. The following margin is Banokuko-1 layer using barium phosphate, and R3 is 0.02.
Examples 1 to 4 in which the magnetic layer was coated on a magnetic layer with a diameter of 71. Fluctuations in F output are small and there is little damage to the tape. Furthermore, the increase in the coefficient of dynamic friction of the back coat is small, making it possible to obtain a tape with excellent running performance and durability.

However, comparative examples (+1) in which the It, a of the magnetic layer is 0.02 μm or more have very poor electromagnetic conversion characteristics including chroma S/N.

Further, as shown in Comparative Example (2), the na of the magnetic layer is 0.0.
Even if the surface roughness is 2 μm or less, if the surface roughness (Ra) of the back coat layer is 0.05 μm or more, the deterioration of S/'N is significant.

Comparative example (3
) has a larger Ra of the back coat layer, compared to comparative example (2).
), the chroma S/N decreases, and the durability is also inferior.

Comparative example (4) using titanium dioxide with an average particle size of 01μ
has a large interlayer friction coefficient, tends to cause cinching (local loosening of the tape) when the tape stops abruptly, and has poor durability because the bank foot layer is often scraped.

Measuring method for Examples and Comparative Examples (at) Pack the tape into the Is socket, 20°C,
NV-6200 (manufactured by Matsushita Electric) in 60% rtl-r
Using a deck, the test was run repeatedly for 200 passes, and at the same time, nF output fluctuations were also measured.

fb) Tape damage was visually evaluated after running 200 passes.

(c) Backcoat layer dynamic friction coefficient...curve 23'0,
In 60% RH, a runnability tester (TB) manufactured by Yokohama System Co., Ltd.
T-300D), set the inlet tension to 20 g, and place one sample tape on a stainless steel pin with a diameter of 3.8 mm.
80' winding, run at 3.3 cm/sec,
The outlet tension was measured and calculated from the following formula.

fdl Coefficient of interlayer friction...23°0.60%
In RTH, using the same device as in (c), setting the inlet tension to 20 g, wind the magnetic layer on the stainless steel drum with a diameter of 62 mm on the upper side, and then wrap the sample tape around it 1800 times. It was run on 80 surfaces at 0.2α/see, the exit tension was measured, and was determined from equation (1).

(e) Surface roughness Ra (
μm)...Three-dimensional roughness measuring instrument 5E-3PK (
Koita Research Institute), cutoff 0.25, stylus force 30 ml.
It was determined by measuring a length of 2.5 mm on the sample surface.

(fl Chroma S/N measurement...HR-71
00 (manufactured by Victor Japan) at the maximum recording current of 4.5
It was determined by recording the MHz and measuring the noise voltage during reproduction.

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer on one side of a support and a back coat layer containing a binder and non-magnetic powder and having a thickness of 1.5 μm or less on the other side of the support, the surface of the magnetic layer is The roughness (Ra) is 0.25 mm cutoff and the center line average roughness (Ra) is 0.02 μm or less, and the back coat layer has an average particle size of 0.01 to 0.02 μm as the nonmagnetic powder.
The surface roughness (Ra) includes 8 μm of barium carbonate and has a center line average roughness (Ra) of 0.25 mm with a cutoff of 0.25 mm.
A magnetic recording medium characterized in that it has a diameter of 0.05 μm or less.