Transparent magnetic recording medium

Details Transparent magnetic recording medium Transparent magnetic recording medium

1999-09-07

2001-07-10

Baxter, Janet (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Radiation sensitive product

Identified backing or protective layer containing

C430S527000, C430S531000, C430S533000

Reexamination Certificate

active

06258519

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a transparent magnetic recording medium, a surface of which contains spherical inorganic particles having a Mohs' hardness of from 6 to 8, that provides no error of magnetic input/output and also excels in transparency.
BACKGROUND OF THE INVENTION
A magnetic recording layer of a magnetic recording medium, such as an audiotape, a videotape, and a floppy disc, contains a high content (coating amount).of magnetic substance, which results in lack of light-permeability, even though high magnetic output (reading) capability can be attained. Consequently, the above-described magnetic recording layer cannot be applied onto the printing surface of a magnetic card or onto a photographic film. U.S. Pat. No. 5,491,051 describes photographic elements that exhibit excellent magnetic and photographic characteristics, and that are capable of repeated use. A difficulty, however, arises for these photographic elements in that recording and reading of magnetic recording information, such as conditions at the time of development and printing, are not assured, as well as at the time of a repeat usage, incorporated with various information, such as the date of photographing, weather, conditions for illumination, conditions at the time of photographing (e.g. the ratio of reduction to enlargement), the number of leaves for reprinting, an area to be zoomed, and some messages. Further, transparent magnetic layer-related techniques are described in JP-A-4-214217 (“JP-A” means unexamined published Japanese patent application), JP-A-6-161033, U.S. Pat. No. 5,496,687, U.S. Pat. No. 5,432,050, U.S. Pat. No. 5,436,120, and U.S. Pat. No. 5,434,037.
SUMMARY OF THE INVENTION
Practically, when a transparent magnetic recording medium is used as, for example, a photographic element (photographic light-sensitive material), a stain (staining materials) of the magnetic head is mainly composed of a dried solid of the developing solution, and it is a very adhesive stain. The above-described adhesive stain, which does not exist when an ordinary magnetic recording medium is used, becomes adhered to and deposited on a magnetic head, so that the contact of a magnetic layer with the head is considerably deteriorated. Further, so-called spacing loss occurs, which results in an error in reading of the magnetic recording. Even if alumina abrasives, which are used for an ordinary magnetic recording medium, are used to clean the stained head, adhesion of a dried solid of the developing solution onto the magnetic head cannot be sufficiently prevented by a previously known method. Further, when the amount of the alumina abrasives to be used is increased, or the grain size of a alumina abrasives is increased, a new problem arises that, nevertheless, the stain-removing efficiency is not so improved, and undesirably the transparency of the medium is extremely decreased, which is disadvantageous to photographic use, and the life (duration) of the magnetic head is drastically shortened.
As a result of their investigation, the present inventors has made clear that it is very effective to locate, at the surface of the medium, spherical inorganic particles having a Mohs' hardness of 6 to 8, preferably monodispersed amorphous (noncrystalline) silica particles, to remove the stain that occurs when a transparent magnetic recording medium is used as a photographic element, i.e., a stain due to a dried solid of the developing solution. Further, according to the above-mentioned method, not only can the contact of a stain originating from a developing solution to a magnetic head be prevented, but also a highly adhesive stain can be removed (cleaned). Further, as a result of investigation, it has been found that these spherical inorganic particles can be extremely uniformly distributed in the surface by a method wherein the spherical inorganic particles are added to a coating solution containing a higher fatty acid ester sliding agent for an upper layer than the magnetic recording layer, and at the time of coating, a part of the magnetic recording layer that is an under layer is dissolved with a solvent of the said coating solution, to thereby incorporate the spherical inorganic particles therein, rather than by incorporating the spherical inorganic particles into the magnetic recording layer that is an under layer. However, the dispersion stability of inorganic particles with the lapse of time is not so good that the thus-prepared inorganic particles in a medium are apt to exist as an aggregate. Consequently, there is the possibility that such problems as reduction in transparency, falling off of the inorganic particles, and increase in a load at the production, will arise. Accordingly, the present invention aims to solve such problems, and to thereby provide an excellent magnetic recording medium.
That is, an object of the present invention is to provide a transparent magnetic recording medium that causes no error in magnetic input/output and also excels in transparency.
Other and further objects, features, and advantages of the invention will appear more fully from the following description.
DETAILED DESCRIPTION OF THE INVENTION
The above-described object of the present invention has been attained by (1) a transparent magnetic recording medium comprising a support and at least one magnetic recording layer containing magnetic particles provided thereon, which comprises, as an upper layer coated on the magnetic recording layer, a layer that contains at least one sort of spherical inorganic particles having a Mohs' hardness of 6 to 8, the surface of the particles being treated with at least one of primary, secondary, or tertiary amine-series silane coupling agents, and that contains a higher fatty acid ester sliding agent; and by (2) a silver halide photographic light-sensitive material which has the above-described transparent magnetic recording medium.
As preferable embodiments of the present invention, the following magnetic recording mediums and light-sensitive material can be mentioned.
(3) The transparent magnetic recording medium as stated in the above (1), wherein the surface of the spherical inorganic particles is treated with at least one of anionic surface active agents in combination with at least one of the primary, secondary, or tertiary amine-series silane coupling agents.
(4) The transparent magnetic recording medium as stated in the above (1), wherein the spherical inorganic particles are noncrystalline silica particles.
(5) The transparent magnetic recording medium as stated in the above (1), wherein said higher fatty acid ester sliding agent is previously dispersed with a solvent containing cyclohexanone, to form a dispersion thereof, and said upper layer contains the above-said dispersion of the higher fatty acid ester sliding agent, and at least one of coating solvents selected from a group consisting of diacetone alcohol, 1-acetoxy-2-methoxyethane, ethylene glycoldiacetate, methyl acetoacetate, and ethyl acetoacetate.
(6) The transparent magnetic recording medium as stated in the above (1), wherein said transparent magnetic recording layer contains inorganic particles having a primary particle size of from 1 nm to 50 nm in an amount of from 10 mg/m
2
to 200 mg/m
2
.
(7) The transparent magnetic recording medium as stated in the above (6), wherein the inorganic particles are colloidal silica.
(8) The transparent magnetic recording medium as stated in the above (1), which further comprises spherical organic high molecular particles.
(9) The transparent magnetic recording medium as stated in the above (8), wherein an average primary particle size of the spherical organic high molecular particles is larger than an average primary particle size of the spherical inorganic particles.
(10) The transparent magnetic recording medium as stated in the above (8), wherein said transparent magnetic recording layer further contains alumina abrasives having substantially higher particle size than the any average height of the surface protrusion of said spherical inorgan

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