1. A method comprising exposing at least a portion of a luminescent coating disposed on a surface of an article to ultraviolet light at one or more preselected wavelengths causing said luminescent coating to exhibit a luminescence spectrum wherein the luminescence spectrum exhibits a plurality of intensity peaks that have been predetermined to create a standard; determining the intensity of at least two peaks in the luminescence spectrum of the coating; determining a peak intensity ratio of at least two peaks; comparing the peak intensity ratio thereby determined with the standard; and, classifying the article according to whether or not the peak intensity ratio does or does not match the standard; wherein the luminescent coating comprises a particulate luminescent composition comprising a rare-earth-doped solid-state solution of alkaline earth fluorides represented by the chemical formula
REx(CaaSrbBac)1\u2212xF2+x\u22122yOy
wherein RE represents a three-valent rare-earth element, 0.005\u2266x\u22660.20, and 0\u2266y\u22660.2, a+b+c=1, with the proviso at least two of a, b, and c are not equal to zero; the particulate luminescent composition exhibiting a luminescence spectrum having a plurality of intensity peaks at characteristic wavelengths.
2. A method comprising within a first time period, a coater causing to be disposed upon the surface of a first plurality of articles a first luminescent coating producing a first plurality of coated articles; and, within a second time period, the coater causing to be disposed upon the surface of a second plurality of articles a second luminescent coating, thereby producing a second plurality of coated articles; a classifier causing to be exposed at least a portion of one or more of the first or second plurality of coated articles to ultraviolet light at one or more preselected wavelengths thereby causing the coating to exhibit, respectively a first or second luminescence spectrum, each said first or second luminescence spectrum exhibiting a plurality of intensity peaks the wavelengths of the peaks having been predetermined using light comprising the preselected wavelength or wavelengths to create a first standard corresponding to the first plurality of coated articles and a second standard corresponding to the second plurality of coated articles; determining the peak intensity ratio of at least two intensity peaks in the first or second luminescence spectrum of the first or second coating; comparing the peak intensity ratio so determined with, respectively, the first or second standard depending upon whether the coated article is from the first or second plurality of coated articles; and, classifying the article according to whether or not the peak intensity ratio does or does not match the first or second standard, respectively; each said coating comprising a particulate luminescent composition, the particulate luminescent composition comprising a rare-earth-doped solid-state solution of alkaline earth fluorides represented by the chemical formula
REx(CaaSrbBac)1\u2212xF2+x\u22122yOy
wherein RE represents a three-valent rare-earth element, 0.005\u2266x\u22660.20, and 0\u2266y\u22660.2, a+b+c=1, with the proviso at least two of a, b, and c are not equal to zero; the particulate luminescent composition exhibiting a luminescence spectrum having a plurality of intensity peaks at characteristic wavelengths.
3. The method of claim 1 wherein at least one pair of the plurality of peaks exhibits an intensity ratio with respect to one another that differs by at least 5% from the corresponding peak intensity ratio of the corresponding reference composition.
4. The method of claim 2 wherein at least one pair of the plurality of peaks exhibits an intensity ratio with respect to one another that differs by at least 5% from the corresponding peak intensity ratio of the corresponding reference composition.
5. The method of claim 1 wherein the coating further comprises a polymer.
6. The method of claim 2 wherein the first coating and the second coating further comprise a polymer.
7. The method of claim 1 wherein RE is Eu+3, Tb+3 or Er+3.
8. The method of claim 2 wherein RE is Eu+3, Tb+3 or Er+3.
9. The method of claim 1 wherein c=0.
10. The method of claim 2 wherein c=0.
11. The method of claim 1 wherein 0.01\u2266x\u22660.10.
12. The method of claim 2 wherein 0.01\u2266x\u22660.10.
13. The method of claim 3 wherein the intensity ratios differ by at least 10%.
14. The method of claim 4 wherein the intensity ratios differ by at least 10%.
15. The method of claim 5 wherein the polymer is ethyl cellulose.
16. The method of claim 6 wherein the polymer is ethyl cellulose.
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 rubber composition for a tire tread, which comprises:
30 to 80 parts by weight of a silica having a pH of 7.1 to 12.0 when dispersed in water to prepare a 5% aqueous dispersion; and
not more than 10 parts by weight of a carbon black on the basis of 100 parts by weight of a rubber component comprising an epoxidized natural rubber.
2. The rubber composition for a tire tread of claim 1, wherein a content of the epoxidized natural rubber in the rubber component is not less than 50% by weight.
3. A tire having a tread prepared by using the rubber composition for a tire tread of claim 1.