Patent US4178416A successfully refreshed from Google Patents.
US4178416A
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Acicular ferric oxide for magnetic recording and process for producing same
Assignee: Eastman Kodak Co
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Filing: 1978-11-09
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Granted: 1979-12-11
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Expires: 1998-11-09
Abstract
Abstract Cobalt doped, acicular, gamma ferric oxide which exhibits reduced print-through without substantial loss in signal output or recording sensitivity is disclosed. This cobalt doped, acicular, gamma ferric oxide is prepared in the presence of a water soluble, acyclic dicarboxylic acid or its precursor which alters or modifies the usual distribution of the cobalt doping ions in the crystal lattice. The dicarboxylic acid directs the distribution of the cobalt doping ions into the crystal lattice in such a way that the crystals obtained by the process disclosed exhibit an increase of at least 5% in the ratios between the intensities of each of the triplet lines 110, 210 and 211 with respect to the 111 line, as shown upon examination by X-ray diffraction analysis. Typical dicarboxylic acids disclosed are oxalic acid, malonic acid, succinic acid, glutaric acid and maleic acid. Magnetic recording products such as tapes, discs and the like, containing the improved cobalt doped, acicular, gamma ferric oxide are also disclosed.
Inventors
- 👤 Jean-Marie H. Hector
- 👤 Bernard J. Pingaud
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:04
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668; G11B5/70673; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
161 words
A process for preparing cobalt doped, acicular, gamma ferric oxide crystals that exhibit improved print-through without substantial loss in signal output or recording sensitivity which process comprises: (1) forming an aqueous dispersion of ferrous hydroxide particles by adding an aqueous solution of ferrous salt having a pH up to about 5.5 to an aqueous solution of a stoichiometric excess of an alkaline hydroxide, in the presence of cobalt doping ions, while substantially avoiding local excesses of said ferrous salt, (2) introducing oxygen into said dispersion at a temperature below 60° C. for a period of time sufficient to convert said ferrous hydroxide particles to ferric oxide hydrate crystals, and, (3) subjecting said crystals to dehydration, reduction and oxidation to form cobalt doped, acicular, gamma ferric oxide, said process being characterized by the addition of about 0.5 to 20 percent, by weight, based on ferrous hydroxide, of a water soluble acyclic dicarboxylic acid or its precursor prior to said introduction of oxygen.
Claim 2
Dependent Claim
161 words
A process for preparing cobalt doped, acicular, gamma ferric oxide crystals that exhibit improved print-through without substantial loss in signal output or recording sensitivity which process comprises: (1) forming an aqueous dispersion of ferrous hydroxide particles by adding an aqueous solution of ferrous salt having a pH up to about 5.5 to an aqueous solution of a stoichiometric excess of an alkaline hydroxide, in the presence of cobalt doping ions, while substantially avoiding local excesses of said ferrous salt, (2) introducing oxygen into said dispersion at a temperature below 60° C. for a period of time sufficient to convert said ferrous hydroxide particles to ferric oxide hydrate crystals, and, (3) subjecting said crystals to dehydration, reduction and oxidation to form cobalt doped, acicular, gamma ferric oxide, said process being characterized by the addition of about 0.5 to 20 percent, by weight, based on ferrous hydroxide, of a water soluble acyclic dicarboxylic acid or its precursor prior to said introduction of oxygen.
Claim 3
Dependent Claim
28 words
A process according to claim 1 in which said dicarboxylic acid is added at a concentration in the range of from about 2 to 10 percent, by weight.
Claim 4
Dependent Claim
24 words
A process according to claim 1 in which said dicarboxylic acid is a straight chain, saturated acid containing from 2 to 7 carbon atoms.
Claim 5
Dependent Claim
18 words
A process according to claim 3 in which said dicarboxylic acid is oxalic, malonic, succinic or glutaric acid.
Claim 6
Dependent Claim
15 words
A process according to claim 1 in which said dicarboxylic acid is an unsaturated acid.
Claim 7
Dependent Claim
23 words
A process according to claim 1 in which said dicarboxylic acid is a substituted dicarboxylic acid containing a halogen, alkyl or aryl group.
Claim 8
Dependent Claim
29 words
A process according to claim 1 in which doping metal ions of nickel, chromium, manganese or zinc are present during the formation of said dispersion of ferrous hydroxide particles.
Claim 9
Dependent Claim
29 words
A product for magnetic recording comprising a support coated with a magnetic recording layer containing cobalt doped, acicular, gamma ferric oxide prepared according to the process of claim 7.
Claim 10
Dependent Claim
18 words
A process according to claim 1 in which said pH is in the range about 2 to 5.
Claim 11
Dependent Claim
111 words
Cobalt doped, acicular, gamma ferric oxide crystals that exhibit improved print-through without substantial loss in signal output or recording sensitivity, said crystals being formed according to the process of claim 1 by cobalt doping in the presence of a water soluble, acyclic, dicarboxylic acid which directs cobalt ions into substitution sites within the crystal lattices, said crystals exhibiting an increase of at least 5 percent in the ratios between the intensities of each of the triplet lines 110, 210, 211, with respect to the 111 line, as determined by X-ray diffraction, in comparison to corresponding crystals prepared according to the process of claim 3 but, in the absence of said acid.
Claim 12
Dependent Claim
24 words
Cobalt doped, acicular, gamma, ferric oxide according to claim 10 which exhibits an increase of about 15 l to 25 percent in said ratios.
Claim 13
Dependent Claim
24 words
A product for magnetic recording comprising a support coated with a magnetic recording layer containing cobalt doped, acicular, gamma ferric oxide of claim 10.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-12-10 | 1983-06-11 | 1983-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-12-10 | 1987-06-11 | 1987-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-12-10 | 1991-06-11 | 1991-12-11 | $7700.00 | Window Closed / Lapsed |