JPS6216450B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium having a magnetic layer on a support, such as a magnetic tape or a magnetic disk. In particular, magnetic tapes are required to have various characteristics, such as a low coefficient of friction, smooth and stable running, a small amount of powder falling off, and good splicability. That is, when magnetic tape is used in magnetic recording and reproducing devices such as VTRs, it runs at high speed while physically contacting tape guides, magnetic heads, etc., so it has excellent wear resistance and remains stable over long periods of time. It is important to be able to drive at For example, if the coefficient of friction on the tape surface changes during recording or playback, the tape will vibrate at the guide or magnetic head. As a result, the frequency of the recorded/playback signal (for example, an audio signal) on the tape changes, resulting in a sound different from the original frequency, or the vibration sound of the tape (so-called Q sound) can be directly heard. There is. In order to prevent this, various attempts have been made to impart lubricity to the tape. for example,
A solid lubricant such as molybdenum disulfide, graphite, wax, etc. is added to a magnetic paint containing magnetic powder such as r-Fe ₂ O ₃ and a vinyl chloride binder. However, this solid lubricant is undesirable because it is not very effective in improving durability and, if added in large amounts, deteriorates the magnetic properties. On the other hand, higher fatty acids, higher fatty esters, paraffinic hydrocarbons,
Silicone oil (e.g. dimethyl silicone oil, diphenyl silicone oil) is sometimes used as a lubricant, but even this cannot provide sufficient durability and lubricity, especially for VTRs.
This is insufficient for use with cassettes. Moreover, blooming, in which the lubricant oozes out onto the surface of the magnetic layer, is likely to occur, causing tape sticking phenomena, stick slips, and the like. In this way, conventional lubricants improve the durability of the tape,
It has the drawback that its running stability and surface properties are not very good, and its still characteristics especially become unstable due to changes over time. The present invention has been made to correct the above-mentioned defects, and is directed to a magnetic recording medium having a magnetic layer on a support, the magnetic recording medium having the general formula (However, R ¹ and R ³ are saturated or unsaturated monovalent hydrocarbon groups having 7 to 21 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 5 carbon atoms, p is an integer of 1 to 12, and 0 <k≦2,0
<l≦1, 0<m<3, 0<n<3, 2≦k+l
+m+n≦3, 0.1<n/m<10, and the number of silicon atoms in one molecule is 2 to 600). It is. According to the present invention, since the organopolysiloxane compound described above contains ^two R ¹ COOR groups and R ³ COO groups in the silicon molecule side chain, it has excellent durability as a magnetic recording medium and has a low coefficient of friction. As the screen size becomes smaller, the slipperiness improves, and the still characteristics and running characteristics after many runs are stable, and wow and flutter (screen shaking) are hardly observed. That is, the ester group represented by R ¹ COOR ² is Si-
Since it is strongly bonded to the molecular chain through C bonds, it has excellent durability. accordingly
It is essential that the number of carbon atoms in R ² is 1 or more, and preferably 5 or less. In addition, the R ³ COO group has an excellent ability to reduce the coefficient of friction,
It has the advantage of contributing to lowering the coefficient of friction, especially when driving at low speeds. As a result, the organopolysiloxane compound represented by the above general formula can provide both durability during high-speed running and running stability during low-speed running. Therefore, the balance n/m between [R ¹ COOR ² ] _n and [R ³ COOR] _o is important, and it is necessary that 0.1<n/m<10. The number of carbon atoms in R ¹ and R ³ is 7 to 21
The reason for this is that if it is less than 7, the friction coefficient will not be lowered sufficiently and the durability will decrease, and if it exceeds 21, the compatibility with the magnetic layer will decrease and the melting point will increase, making it easier to cause blooming. It is from. Regarding (CF ₂ ) _P of the F-containing hydrocarbon group, p is set to 1 to 12 because
This is because if it exceeds 12, the compatibility with the magnetic layer will decrease and the melting point will increase, making it easier to cause blooming and head staining. Regarding [0(CF ₂ ) _P CH ₂ CH ₂ ] _l , l is set to 1 or less because if it exceeds 1, the compatibility with the magnetic layer decreases, blooming tends to occur, and the durability deteriorates. It is from.
Regarding [R ¹ COOR ² ] _n , if the value of m is small, the slipperiness (durability during high-speed running) will be insufficient, and if the value is large, the ratio n to the [R ₃ COO] group in the molecule will be insufficient. /m becomes small, and the friction coefficient does not decrease sufficiently. Therefore, it is more preferable that 0.1<m<2.5. Regarding [R ³ COO−] _o , if the value of n is small, the coefficient of friction will not decrease sufficiently, and if the value is large, the ratio n/m to the [R ¹ COOR ² ] group in the molecule will become large. Durability decreases. Therefore 0.1
It is preferable that <n<2.5. The organopolysiloxane compound represented by the above general formula may have a linear, branched, or cyclic molecular structure. If the number of silicon atoms in one molecule exceeds 600, the compatibility with the magnetic layer will decrease and blooming will easily occur, so the number should be 600 or less. The amount of the organopolysiloxane lubricant used in the present invention is 0.5 to 7 parts by weight per 100 parts by weight of the magnetic powder in the magnetic layer, in order to fully exhibit the above-mentioned effects. (PHP) is preferable. When it is included in the back coat layer (described later) on the back of the base, it is preferably 0.5 to 20 parts by weight (PHR) per 100 parts by weight of the binder in the back coat layer. Further, when a top coat layer or coating layer (both described below) made of the above-mentioned lubricant is applied, the amount of the lubricant applied is preferably 1 to 1000 mg/m ² . Next, a typical method for synthesizing this organopolysiloxane compound will be explained. Representative example 1 SiH ^group - _{containing organopolysiloxane} represented ^by
It is obtained by reacting a fatty acid unsaturated alcohol ester represented by divalent hydrocarbon group (3) with a fatty acid represented by R ³ COOH in the presence of a platinum catalyst at a temperature in the range of 50°C to 150°C. Representative example 2 (However, R ⁵ is a divalent hydrocarbon group having 2 to 5 carbon atoms.) The Si-Cl group-containing organopolysiloxane represented by ≡ and R ¹ COOH and R ₃ COOH were heated at 30°C in the presence of a hydrochloric acid scavenger. Obtained by reaction at a temperature range of ~150°C. Examples of hydrochloric acid scavengers include tertiary amine compounds such as triethylamine, pyridine, and picoline. A magnetic recording medium, such as a magnetic tape, according to the present invention is illustrated in FIGS. 1 to 5. FIG. 1 shows a non-magnetic base 1 on which a magnetic layer 2 containing the lubricant of the present invention is formed. In the following figures as well, the layer containing the lubricant according to the invention is shown in dotted cross-sections. Figure 2 shows
This figure shows a state in which a top coat layer 3 made of a lubricant according to the present invention is formed on the surface of a magnetic layer 2. FIG. 3 shows a state in which a coating layer 4 made of a lubricant according to the present invention is formed on the back surface of the nonmagnetic base 1. FIG. 4 shows a state in which the lubricant according to the present invention is contained in the back coat layer 5 formed on the back surface of the nonmagnetic base 1, and further, FIG. A state in which layer 6 is formed is shown. The back coat layer 5 is provided for various purposes, including stabilizing runnability by appropriately controlling the surface roughness of the back surface, and preventing static electricity. For this purpose, the back coat layer may be coated with a binder mixed with carbon black, or may further contain a nonmagnetic pigment such as α-Fe ₂ O ₃ , alumina, talc, etc. The magnetic recording medium of the present invention can be applied not only to such magnetic tapes but also to magnetic disks having magnetic layers on the front or back surfaces. Also, among FIGS. 1 to 5, for example, a combination of FIG. 1 and FIGS. 2 to 5,
A combination of Figure 2 and Figures 3 to 5, Figure 3
As shown in FIG. 4 and FIG.
It can be placed inside, or on the front and/or back surface of the magnetic layer 2. Ferromagnetic powder (magnetic powder) that can be used in the magnetic layer of the present invention includes γ-Fe ₂ O ₃ , Fe ₃ O ₄ , γ-Fe ₂ O ₃
and Fe ₃ O ₄ , cobalt-doped γ-
Fe ₂ O ₃ , cobalt-doped Fe ₃ O ₄ , chromium dioxide, barium ferrite, various alloy powder magnetic materials (e.g. Fe-Co, Co-Ni, Fe-Co-Ni, Fe
-Co-B, Fe-Co-Cr-B, Mn-Bi, Mn-
Al, Fe-Co-V, etc.), iron nitride, etc., and two or more of these may be used in combination. Binders that can be used in the magnetic layer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinylidene chloride. copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-sterene copolymer, Thermoplastic polyurethane resin, phenoxy resin polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-acrylic acid copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl petyral , polyvinyl acetal, cellulose derivatives, styrene-butadiene copolymers, polyester resins, phenol resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, and the like. Additionally, reinforcing materials that can be used for the magnetic layer include aluminum oxide,
Chromium oxide, silicon oxide, etc. can be used singly or as a mixture. Furthermore, conventionally known fine particulate carbon black can be used as an antistatic agent, and lecithin can be used as a dispersant. When preparing magnetic paint, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone are used as organic solvents;
Alcohols such as methanol, ethanol, propanol, butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate,
Esters such as monoethyl ether; glycol ethers such as ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, and dioxane; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and heptane; nitropropane, etc. can be used alone or as a mixture. Non-magnetic bases for applying magnetic paint prepared with this organic solvent include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene,
Examples include cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarbonate, polyvinyl chloride, polyimide, metal materials such as aluminum and copper, and paper. Further, as a magnetic recording medium to which the organopolysiloxane compound of the present invention is applied as a lubricant,
The present invention is not limited to so-called coated magnetic recording media in which a magnetic layer is formed by applying magnetic powder together with a binder as described above, but can also be applied to metal thin film magnetic recording media. This metal thin film type magnetic recording medium is produced by so-called physical vapor deposition (PVD) technology such as vacuum evaporation, ion plating, or sputtering, or by liquid phase deposition of magnetic metals such as Co, Fe, Ni, or their alloys onto a nonmagnetic support. It is formed using the Metsuki technique. This metal thin film type magnetic recording medium has a high magnetic flux density because it does not require the use of a binder, and since it is formed into a very thin layer, it is useful for short wavelength, high density recording. Hereinafter, the present invention will be explained in detail with reference to examples. First, examples of synthesis of the lubricant made of the organopolysiloxane compound used in this example are listed in the table below.

[Table] Next, the composition and characteristics of the magnetic paint common to this example were as follows. γ-Fe ₂ O ₃ 100 parts by weight Vinyl chloride-vinyl acetate copolymer (VAGH manufactured by UCC) 18 parts by weight Polyurethane resin (Estan 5702 manufactured by BF Gutduritsu) 12 parts by weight Carbon (antistatic agent) 0.5 parts by weight Lecithin (dispersant) 1.0 parts by weight Lubricant (below) (below) Methyl ethyl ketone (solvent) 150 parts by weight Methyl isobutyl ketone (solvent) 150 parts by weight These raw materials were mixed in a ball mill for 24 hours, then taken out through a filter. Furthermore, immediately before coating, 3 parts by weight of an isocyanate compound was added and stirred for 30 minutes. This mixture was then placed on a polyethylene terephthalate base with a thickness of 12 μm to a thickness of 5 μm after drying.
The film was coated so as to have a thickness of μ, followed by orientation, and after drying, it was rolled up. After surface treatment, this was cut into 1/2-inch width and used as a sample tape. Examples 1 to 7 Examples 1 to 7 were sample tapes in which 2.0 PHP (parts by weight) of each of the seven organopolysiloxane compounds of Synthesis Examples 1 to 7 were added to the magnetic powder. Comparative Examples 1 and 2 Sample tapes were prepared using dimethyl silicone oil (Comparative Example 1) and methylphenyl silicone oil (Comparative Example 2) as lubricants, respectively. Reference Example 1 As a lubricant, R ¹ COOR ² groups and R ³ COO from Synthesis Example 1
A sample tape was prepared using an organopolysiloxane compound with a group ratio of n/m=0.04/0.5=0.08. After examining the various characteristics of the tapes in each of the above examples, we found that
The results shown in the table below were obtained.

【table】

[Table] From this data, using the lubricant according to this example lowers the friction coefficient and achieves running stability, almost no wow or flutter (screen shaking) is observed, and the still characteristics are significantly improved. do. Furthermore, since durability is improved, it is advantageous for extending the life of the tape. In addition, as compared with Reference Example 1, there is a tendency for μd to increase as the R ³ COO− content decreases. Example 8 A magnetic layer was formed by vacuum evaporating Co to a thickness of 1000 Å on a base made of polyethylene terephthalate having a thickness of 12 μm by an oblique evaporation method. On the thus formed magnetic layer, a 1% Freon solution of the organopolysiloxane of Synthesis Example 1 was applied (top coat) so that the coating amount of the organopolysiloxane was 20 mg/m ² . The μd of the magnetic layer of the magnetic tape thus obtained was 0.205. Example 9 A magnetic coating obtained by removing the lubricant from the magnetic coating composition described above was applied to a thickness of 5μ on a polyethylene terephthalate base having a thickness of 12μ to form a magnetic layer. A 1% Freon solution of the organopolysiloxane of Synthesis Example 1 was applied onto this magnetic layer (top coat) so that the coating amount of the organopolysiloxane was 80 mg/m ² . The characteristics of the magnetic tape thus obtained were as follows: μd=0.175 Still characteristics: 60 minutes or more No wow or flutter. Example 10 The following components: Carbon 100 parts by weight Polyurethane resin (Estan 5702) 50 parts by weight Epoxy resin (Epicron 351 Dainippon Ink Co., Ltd.)
After mixing 50 parts by weight of lubricant (Synthesis Example 2), 2 parts by weight of methyl ethyl ketone, 400 parts by weight, and 400 parts by weight of toluene, 20 parts by weight of Dismodule L was added to prepare a paint for back coating. Example 10 was prepared by applying this paint to the back surface of the base so that the thickness after drying was 3 μm to form a back coat layer 5 (see FIG. 4). Comparative Example 3 A sample tape to be used as a back coat layer was prepared by applying a paint obtained by removing only the lubricant component from the back coat paint shown in Example 10 to the back surface of a base. Example 11 A 1% Freon solution of the organopolysiloxane of Synthesis Example 3 was applied onto the back coat layer of Comparative Example 3 so that the coating amount of the organopolysiloxane was 20 mg/m ² to form coating layer 4 (Fig. 5). reference)
Example 11 was a sample tape formed by forming the following. Example 12 A magnetic coating obtained by removing the lubricant from the magnetic coating composition described above was applied to a thickness of 5μ on a polyethylene terephthalate base having a thickness of 12μ to form a magnetic layer, and 1 of the organopolysiloxane of Synthesis Example 3 above was coated on the back of the base. Example 12 was a sample tape in which a coating layer 4 (see FIG. 3) was formed by coating a % Freon solution at a coating amount of organopolysiloxane of 2 mg/m ² . Comparative Example 4 A sample tape was prepared from Example 12 except that coating layer 4 was removed. The results of examining the characteristics of the tapes of each of the above examples are shown in the table below.

[Table] As described above, in this example, the coefficient of friction of the tape is reduced, running stability is obtained, and no wow or flutter (screen shaking) is observed.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views showing embodiments of magnetic recording media according to the present invention. 1 is the base, 2 is the magnetic layer, 3 is the top coat,
4 and 6 are lubricant coating layers, and 5 is a back coat layer.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer on a support, the magnetic recording medium having the general formula (However, R ¹ and R ³ are saturated or unsaturated monovalent hydrocarbon groups having 7 to 21 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 5 carbon atoms, p is an integer of 1 to 12, and 0 <k≦2,0
<l≦1, 0<m<3, 0<n<3, 2≦k+l
+m+n≦3, 0.1<n/m<10, and the number of silicon atoms in one molecule is 2 to 600).