1. A copper-covered steel foil for carrying a negative electrode active material for a lithium ion secondary battery, which has a steel sheet as a core material thereof and has, on both surfaces thereof, a copper covering layer having a mean thickness tCu of from 0.02 to 5.0 \u03bcm on each surface, and of which the total mean thickness, t, including the copper covering layer is from 3 to 100 \u03bcm with tCut of at most 0.3.
2. The copper-covered steel foil as claimed in claim 1, wherein the copper covering layer is a copper electroplating layer (including one rolled after plating).
3. The copper-covered steel foil as claimed in claim 1, wherein the copper covering layer is a copper foil layer integrated with the steel sheet through cladding.
4. The copper-covered steel foil as claimed in claim 1, wherein the steel sheet is formed of a cold-rolled steel plate (including steel strip) as defined in JIS G3141:2009.
5. The copper-covered steel foil as claimed in claim 1, wherein the steel sheet has an austenitic or ferritic chemical composition as defined in JIS G4305:2005.
6. The copper-covered steel foil as claimed in claim 1, wherein the steel sheet has a composition comprising, in terms of % by mass, C: 0.001 to 0.15%, Si: 0.001 to 0.1%, Mn: 0.005 to 0.6%, P: 0.001 to 0.05%, S: 0.001 to 0.5%, Al: 0.001 to 0.5%, Ni: 0.001 to 1.0%, Cr: 0.001 to 1.0%, Cu: 0 to 0.1%, Ti: 0 to 0.5%, Nb: 0 to 0.5%, N: 0 to 0.05%, with a balance of Fe and an inevitable impurity.
7. The copper-covered steel foil as claimed in claim 1, wherein the steel sheet has a composition comprising, in terms of % by mass, C: 0.0001 to 0.15%, Si: 0.001 to 4.0%, Mn: 0.001 to 2.5%, P: 0.001 to 0.045%, S: 0.0005 to 0.03%, Ni: 6.0 to 28.0%, Cr: 15.0 to 26.0%, Mo: 0 to 7.0%, Cu: 0 to 3.5%, Nb: 0 to 1.0%, Ti: 0 to 1.0%, Al: 0 to 0.1%, N: 0 to 0.3%, B: 0 to 0.01%, V: 0 to 0.5%, W: 0 to 0.3%, total of Ca, Mg, Y, REM (rare earth metal): 0 to 0.1%, with a balance of Fe and an inevitable impurity.
8. The copper-covered steel foil as claimed in claim 1, wherein the steel sheet has a composition comprising, in terms of % by mass, C, 0.0001 to 0.15%, Si: 0.001 to 1.2%, Mn: 0.001 to 1.2%, P: 0.001 to 0.04%, S: 0.0005 to 0.03%, Ni: 0 to 0.6%, Cr: 11.5 to 32.0%, Mo: 0 to 2.5%, Cu: 0 to 1.0%, Nb: 0 to 1.0%, Ti: 0 to 1.0%, Al: 0 to 0.2%, N: 0 to 0.025%, B: 0 to 0.01%, V: 0 to 0.5%, W: 0 to 0.3%, total of Ca, Mg, Y, REM (rare earth metal): 0 to 0.1%, with a balance of Fe and an inevitable impurity.
9. The copper-covered steel foil as claimed in claim 1, which has a tensile strength of from 450 to 900 MPa.
10. The copper-covered steel foil as claimed in claim 1, which has a tensile strength of from more than 600 to 900 MPa.
11. A negative electrode collector for a lithium ion secondary battery, which has an active material layer for a negative electrode of a lithium ion secondary battery, as formed on the surface of at least one copper covering layer of the copper-covered steel foil of claim 1.
12. A negative electrode collector for a lithium ion secondary battery, which has a carbon-based active material layer for a negative electrode of a lithium ion secondary battery, as formed on the surface of at least one copper covering layer of the copper-covered steel foil of claim 1, at a density of at least 1.50 gcm3.
13. A negative electrode collector for a lithium ion secondary battery, which has a carbon-based active material layer for a negative electrode of a lithium ion secondary battery, as formed on the surface of at least one copper covering layer of the copper-covered steel foil of claim 1, at a density of at least 1.80 gcm3.
14. A negative electrode collector for a lithium ion secondary battery, which has a carbon-based active material layer for a negative electrode of a lithium ion secondary battery, as formed on the surface of at least one copper covering layer of the copper-covered steel foil of claim 1, at a density of at least 2.00 gcm3.
15. A method for producing a negative electrode collector for a lithium ion secondary battery, which comprises:
a step of forming a coating film that contains a carbon-based active material for a negative electrode of a lithium ion secondary battery, on the surface of at least one copper covering layer of the copper-covered steel foil of claim 1, and
a step of roll-pressing the coating film, after drying it, to reduce the coating film thickness by from 30 to 70% thereby densifying the coating film.
16. A method for producing a negative electrode collector for a lithium ion secondary battery, which comprises:
a step of forming a coating film that contains a carbon-based active material for a negative electrode of a lithium ion secondary battery, on the surface of at least one copper covering layer of the copper-covered steel foil of claim 1, and
a step of roll-pressing the coating film, after drying it, to increase the density of the coating film to at least 1.80 gcm3 thereby densifying the coating film.
17. A lithium ion secondary battery using the negative electrode collector of claim 11 for a negative electrode therein.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A heat-sensitive recording material comprising (a) a support and (b) a heat-sensitive recording layer formed on the support and containing a leuco dye, a developer and a binder, the heat-sensitive recording layer containing at least two hydroxy-diphenylsulfone compounds as the developer and a black-color-forming leuco dye and a red-color-forming leuco dye as the leuco dye, the red-color-forming leuco dye being present in an amount of 0.5 to 3.5 wt. % relative to the black-color-forming leuco dye.
2. The heat-sensitive recording material according to claim 1 wherein the hydroxy-diphenylsulfone compounds are a mixture of 4-hydroxy-4-isopropoxy-diphenylsulfone and at least one member selected from the group consisting of 2,4-dihydroxy-diphenylsulfone and 4,4-dihydroxy-diphenylsulfone.
3. The heat-sensitive recording material according to claim 2 wherein said at least one member selected from the group consisting of 2,4-dihydroxy-diphenylsulfone and 4,4-dihydroxy-diphenylsulfone is used in an amount of about 0.5 to about 2.0 parts by weight per part by weight of 4-hydroxy-4-isopropoxy-diphenylsulfone.
4. The heat-sensitive recording material according to claim 1 wherein the black-color-forming leuco dye is at least one member selected from the group consisting of 3-di(n-butyl)amino-6-methyl-7-anilinofluoran, 3-di(n-pentyl)amino-6-methyl-7-anilinofluoran and 3-di(n-butyl)amino-7-(o-chloroanilino)fluoran.
5. The heat-sensitive recording material according to claim 4 wherein the black-color-forming leuco dye is a mixture of 3-di(n-butyl)amino-7-(o-chloroanilino)fluoran and at least one member selected from the group consisting of 3-di(n-butyl)amino-6-methyl-7-anilinofluoran and 3-di(n-pentyl)amino-6-methyl-7-anilinofluoran.
6. The heat-sensitive recording material according to claim 5 wherein 3-di(n-butyl)amino-7-(o-chloroanilino)fluoran is used in an amount of 30 to 300 wt. % relative to at least one member selected from the group consisting of 3-di(n-butyl)amino-6-methyl-7-anilinofluoran and 3-di(n-pentyl)amino-6-methyl-7-anilinofluoran.
7. The heat-sensitive recording material according to claim 1 wherein the red-color-forming leuco dye is 3-diethylamino-7-chlorofluoran.
8. The heat-sensitive recording material according to claim 1 which contains the red-color-forming leuco dye in an amount of about 0.8 to about 3.0 wt. % relative to the black-color-forming leuco dye.
9. The heat-sensitive recording material according to claim 1 wherein the heat-sensitive recording layer further comprises a blue-color-forming leuco dye in an amount of about 0.5 to about 5 wt. % relative to the black-color-forming leuco dye.
10. The heat-sensitive recording material according to claim 1 wherein a water dispersible resin is contained as the binder in the heat-sensitive recording layer.
11. The heat-sensitive recording material according to claim 1 wherein the heat-sensitive recording layer further comprises a sensitizer, a print stability-improving agent or a mixture thereof.
12. The heat-sensitive recording material according to claim 1 which further comprises a protective layer on the heat-sensitive recording layer.