JPH0562159A - Metal fine particle magnetic recording material and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a recording material which achieves both magnetic recording and optical recording with a simple process. CONSTITUTION:By heating a metal compound and a reducer within a binder for reaction, a compound metal fine particle layer is formed, thus enabling a magnetic recording material to be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density magnetic recording material and a high density optical recording material in the information field.

[0002]

2. Description of the Related Art Although many magnetic recording materials are known so far, the magnetic material is made into fine particles by means such as pulverization,
It is usually prepared by dispersing in a binder and coating, or by evaporating a metal species on a substrate in a vacuum. Therefore, the manufacturing process of the recording material has many steps and is complicated.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a simple method for producing a recording material which is capable of simultaneously producing fine metal particles and forming a recording layer by a heat treatment using a metal compound as a raw material, and an inexpensive recording material. It is a thing.

[0004]

The inventors of the present invention have previously heated a composition comprising an organometallic salt compound, a reducing agent, and a binder (hydrophobic organic polymer) as disclosed in JP-A-2-160582. Although a hole-piercing type optical recording material obtained by the above is proposed, as a result of research on these inventions, it was found that a magnetic recording material can be obtained, and the present invention was completed. The fact that magnetic recording materials can be obtained by utilizing the reduction reaction of metal compounds in this way is completely new. In addition, it provides a completely new recording material in that optical recording and magnetic recording can be performed on the same material.

That is, the present invention is as follows. 1. 1. A magnetic recording material characterized in that fine metal particles obtained by reducing a ferromagnetic metal compound are dispersed in a binder. A magnetic recording material, characterized in that a coating liquid containing a ferromagnetic metal compound and a binder is applied and dried to form a smooth surface, and then the ferromagnetic metal compound is reduced to form metal fine particles. Is.

In order to impart the magnetic recording characteristics to the fine metal particles in the present invention, at least one compound selected from ferromagnetic compounds of iron, cobalt and nickel is used as the metal compound. Examples of ferromagnetic metal compounds include iron (III) acetylacetonate, iron (III) cyclohexylbutyrate, cobalt acetate, cobalt (II) acetylacetonate, cobalt (III) acetylacetonate, and cobalt benzoate. (II), cobalt (II) gluconate, cobalt stearate, cobalt phenyldiazosulfonate (I
I), potassium bromopentacyanocobaltate (III), cobalt (II) cyclohexylbutyrate, cobalt naphthenate, nickel acetate, nickel (II) acetylacetonate, nickel (II) cyclohexylbutyrate, nickel naphthenate and the like can be used. Various metal salts of organic carboxylic acids, various inorganic salts, complex salts and the like can be used.

Further, in order to form the composite metal fine particles in order to further improve the magnetic recording characteristics, it is desirable to use two or more kinds of metal compounds. As the compound of the non-ferromagnetic metal other than iron, cobalt and nickel, various metal salts of organic carboxylic acids, various inorganic salts, complex salts and the like can be used. Examples of useful metal compounds include silver trifluoroacetate, silver heptafluorobutyrate, silver-hexafluoroacetylacetonate, potassium chloroplatinate (II), palladium acetate, chromium (II).
I) Acetylacetonate, chromium (III) phenyldiazosulfonate, copper (II) bis (acetylacetonate), copper (I) phenyldiazosulfonate and the like. When two or more kinds of metal compounds are used, a combination of only ferromagnetic metal compounds may be used.
A compound of a ferromagnetic metal and a compound of a non-ferromagnetic metal may be combined, and in this case, the ratio of the compound of the ferromagnetic metal contained in all the metal compounds used should be 5% or more in terms of molar ratio. Is desirable.

Further, as a method of producing the composite metal fine particles, two or more kinds of metal compounds are not necessarily required, and the metal catalyst nucleus is added to the recording material composition layer to be contained in the recording material composition. There is also a method of forming composite metal fine particles with a metal compound. In the present invention, a suitable reducing agent may be used in order to form the metal fine particle-containing layer in the binder. Any reducing agent may be used as long as it can reduce the metal compound used. Various phenols are useful as preferable reducing agents. Examples of the compound as a preferable reducing agent include 2,6-di-t-butyl-4-methylphenol and 2,2'-methylenebis- (4-ethyl-6).
-T-butylphenol), 2-t-butyl-6-
(3'-t-butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate, hydroquinone and the like can be used. These reducing agents may be used alone or in combination of two or more depending on the type of metal compound used. The amount of the reducing agent depends on the kind of the metal compound and the reducing agent, but preferably, the amount of the reducing agent is about 0.01 per 1 mol of the metal compound.
The molar amount is about 10 mol, more preferably about 0.1 mol to about 3 mol.

The polymer compound used as the binder is
In order to obtain a recording material having good storage stability, a hydrophobic polymer compound is preferable. In particular, in order to obtain better stability under storage conditions of high temperature and high humidity, use of hydrophilic polymer compounds such as gelatin and polyvinyl alcohol should be avoided. The preferred binder in the present invention can be appropriately selected from a wide range of hydrophobic organic polymer compounds such as polymethylmethacrylate, polyvinylbutyral, vinyl acetate, polystyrene and polystyrene-methylmethacrylate copolymer.

The recording material of the present invention may contain various additive components in order to enhance the performance. For example, in order to control the reaction rate of the metal compound and the size of the metal fine particles, an oxidizing agent, a metal complex forming agent, a metal ion transfer agent, etc. can be added. The recording material of the present invention can be produced, for example, as follows. That is, a metal compound, a reducing agent, and a polymer compound as a binder are previously dissolved or dispersed in an appropriate solvent to prepare a uniform coating solution. The solvent used at this time can be selected from commonly used organic solvents depending on the metal compound and the reducing agent. Next, this coating solution is applied to a substrate by an appropriate method such as a spin coating method or a roll coating method and dried to obtain a recording material composition layer. The thickness of the recording material composition layer is preferably 1 μm or more and 50 μm or less after drying. A metal catalyst nucleus is formed as a catalyst nucleus on the surface of this recording material composition layer, and when this is further heated, a reflective metal fine particle-containing layer is formed on the surface. The metal catalyst nucleus has a function of precipitating metal fine particles on the surface of the recording material composition layer in a high concentration, and is important because it forms a magnetic recording layer or an optical recording layer.

Noble metal species such as silver, palladium, platinum, gold and rhodium can be used as the metal catalyst nucleus. These metal catalyst nuclei may be a single metal species, a composite system of these metal species, or a compound such as silver sulfide or silver oxide. As a method of forming a metal catalyst nucleus on the surface of the recording material composition layer, a method of dispersing the metal catalyst nucleus in a solvent containing a suitable binder and coating the surface of the recording material composition layer, or a vapor deposition method, Method of forming metal catalyst nuclei on the surface by sputtering, etc., exposing the surface to a reducing solution or reducing gas to reduce a part of the metal compounds contained in the recording material composition layer to form metal catalyst nuclei. And a method of forming a metal catalyst nucleus of palladium or the like by immersing in an activating liquid used in the pretreatment of the electroless plating method. The most appropriate method may be selected depending on the type of metal compound, binder, etc.

The recording material composition layer having the metal catalyst nuclei thus formed on the surface thereof is heated under appropriate heating conditions, for example, at least 7.
When heated at a temperature of 0 ° C. or higher for several minutes to several tens of minutes, a recording material containing a reflective metal fine particle layer on the surface is obtained. Suitable heating conditions are preferably 90 to 170.
The temperature is about 50 seconds to 40 minutes. It is necessary to control the heating conditions to optimum conditions depending on the kinds of the metal compound, reducing agent and binder so as to satisfy the characteristics of the recording material of the present invention. It should be noted that if the heating is insufficient, the unreacted metal compound may adversely affect the storage stability of the recording material under high temperature and high humidity.

The recording material of the present invention thus obtained has a structure in which fine metal particles are dispersed in a binder. However, in the case of punching type optical recording, the density is particularly high in a portion close to the surface. It is necessary to deposit metal fine particles on the surface to form a reflecting surface having an optical reflectance of about 15% to 80%. That is, the volume filling rate of the metal fine particles in the binder may be 2% to 75% in the case of a magnetic recording material, but in order to use it as a magnetic / optical recording material,
The volume filling rate of the metal fine particles in the layer 0.2 μm from the surface is 1
It is preferably 0% to 75%, more preferably 25% to 65%. The particle size of the metal fine particles is preferably 5 nm to 1 μm, and in the case of a magnetic / optical recording material, it is preferably 10 nm to 100 nm.

In order to control the dispersion structure of the metal fine particles in the binder as described above, it is necessary to select the combination and composition ratio of the metal compound, the reducing agent and the binder to be used, the kind and density of the metal catalyst nucleus, the heating conditions and the like. There is. That is, if the reduction reaction of the metal compound is too fast or the activity of the metal catalyst nucleus is weak, it is not possible to deposit metal fine particles at a high density in a portion near the surface, and an optical reflection surface cannot be obtained. In other words, in order to produce a magnetic / optical recording material, the reduction reaction proceeds rapidly in the vicinity of the metal catalyst nucleus, and the reaction proceeds slowly in the binder as compared with that, by the movement of the metal compound or metal ion to the surface. This means that it is necessary to select a combination of raw materials capable of producing a concentration gradient of the metal fine particles and manufacturing conditions such as heating conditions.

When the recording material of the present invention is applied to a medium, a transparent protective layer may be provided on the surface. For optical recording, this protective layer should be transparent at the wavelength of light used. The recording material of the present invention can be written and read using a recording / reproducing device for a magnetic card. It is also possible to write and read data in the form of a disk using a floppy disk recording / reproducing device. When performing optical recording, for example, the wavelength is 83
Using a semiconductor laser of 0 nm and an output of 10 mW,
It is possible to record with a pulse width of 1 to 0.1 μs with a beam diameter of 3 μm, and to reproduce with continuous light with a power of 0.3 to 1 mW.

As described above, the greatest feature of the recording material of the present invention is that the same material can be used for magnetic recording and optical recording. Therefore, magnetic recording having both a magnetic recording portion and an optical recording portion can be performed.
It can be applied to media such as optical cards. When applied to such a medium, it is not necessary to separately provide the magnetic recording portion and the optical recording portion, which is extremely effective in simplifying the manufacturing process and reducing the cost. Further, even when manufactured as a magnetic recording material, the manufacturing process can be simplified and the cost can be reduced as compared with the conventional method.

[0017]

EXAMPLES Examples will be shown below for illustrating the present invention further in detail, but the present invention is not limited thereto.

[0018]

Example 1 A solution containing the following components was prepared as a coating solution. Cobalt (II) acetylacetonate 4.7g 2,2'-methylenebis- (4-ethyl-6-t-butylphenol) 2.8g polymethylmethacrylate 4.6g 2-butanone 50.0g After homogenizing this solution Undissolved substances and dust were removed through a filter having a pore size of 0.2 μm. This coating liquid was applied to a polyethylene terephthalate film having a thickness of 75 μm using an applicator so that the thickness after drying would be 7 μm, and dried to form a recording material composition layer.

Next, on the surface of this recording material composition layer, platinum catalyst nuclei were vapor-deposited to a thickness of about 20 nm by a sputtering method and heated with a hot air heater at 145 ° C. for 20 minutes to form a cobalt-platinum composite. A fine particle recording layer was formed to obtain a recording material. It was possible to write to and read from this recording material using an improved recording / reproducing device for floppy disks.

[0020]

Example 2 A solution containing the following components was prepared as a coating solution. Cobalt (II) phenyldiazosulfonate 1.6 g Nickel (II) acetylacetonate 0.7 g Chromium (II) phenyldiazosulfonate 2.5 g 2-t-butyl-6- (3'-t-butyl-) 5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate 2.3 g 1-phenyl-3-pyrazolidone 1.1 g hydroquinone 0.4 g polystyrene-methyl methacrylate-methyl acrylate copolymer [copolymerization composition ratio 40 -50-10 (weight ratio)] 5.2 g 2-butanone 40.0 g Toluene 10.0 g Methanol 2.2 g After homogenizing this solution, undissolved substances and dust were removed through a filter having a pore size of 0.2 μm. This coating solution was applied to a polyethylene terephthalate film having a thickness of 75 μm by using an applicator so that the thickness after drying would be 9.6 μm, and dried to form a recording material composition layer.

Next, the recording material composition layer was subjected to the following pretreatment liquids 1 to 4 for electroless plating for the times shown below,
Sequential immersion and drying were carried out to form palladium catalyst nuclei on the surface of the recording material composition layer. [Treatment liquid 1] ... 30 seconds Activator Neogant 834 8 ml [trade name, manufactured by Nippon Schering Co., Ltd.] Sodium hydroxide 0.6 g Pure water 988 ml [Treatment solution 2] ... 30 seconds Reducer Neogant WA 1 ml [trade name, manufactured by Nippon Schering Co., Ltd.] Boric acid 1 g Pure water 990 ml [Treatment liquid 4] 5 seconds Pure water 1 l Next, this sample was heated at 150 ° C. for 10 minutes and then surface A reflective cobalt-nickel-chromium composite metal fine particle-containing layer was formed on to obtain a recording material. The reflectance of this recording material was 38%. Next, this recording material was punched with a hollow blade to prepare a credit card size medium.

A semiconductor laser with a wavelength of 830 nm (power 10 mW, beam diameter 3 μm) was used for this medium.
When recording was performed at a scanning speed of 0 cm / sec, pits could be formed, and the recording signal could be reproduced with 0.5 mW continuous light. In addition, it was possible to write and read information with a recording / reproducing device for a magnetic card.

[0023]

INDUSTRIAL APPLICABILITY The present invention provides a simple method for producing a magnetic recording material, and can obtain a new recording material capable of both magnetic recording and optical recording as well as magnetic recording.

Claims (2)

[Claims] 1. A magnetic recording material characterized in that fine metal particles obtained by reducing a ferromagnetic metal compound are dispersed in a binder. 2. A coating solution containing a ferromagnetic metal compound and a binder is applied and dried to form a smooth surface, and then the ferromagnetic metal compound is reduced to form fine metal particles. Magnetic recording material.