Toner, toner cartridge, development device, and image forming apparatus

1. A toner comprising:

binder resin; and

a coloring agent provided in the binder resin,

wherein the coloring agent is configured so that

hue of a hue measurement print image printed on a print medium with the toner satisfies

−8.6≤ a *( Y )≤−7.9 and 93.4≤ b *( Y )≤95.4

where a*(Y) and b*(Y) respectively represent an a* value and a b* value of the hue measurement print image in an L*a*b* color model,

light resistance F of a light resistance measurement print image printed on a print medium with the toner, after an irradiation test in which the light resistance measurement print image is irradiated with light having 0.36 W/m 2 spectral irradiance at a wavelength of 340 nm for 663 hours satisfies

F≥70%, and

the light resistance F is obtained as

F (%)=( D ( E )/ D ( S ))×100(%)

where D(E) represents optical density of a 100% density image with the toner after the irradiation test and D(S) represents optical density of the 100% density image with the toner before the irradiation test, and

wherein the toner is configured so that melt viscosity η of the toner at 120° C. satisfies

1400(Pa·s)≤η≤1600(Pa·s).

2. The toner according to claim 1 , wherein

the coloring agent includes a plurality of pigments, and

the plurality of pigments include C.I. Pigment Yellow 155 and C.I. Pigment Yellow 185.

3. The toner according to claim 2 , wherein a mixture ratio of the C.I. Pigment Yellow 155 and the C.I. Pigment Yellow 185 is 4:1.

4. The toner according to claim 1 , wherein

the a*(Y) and the b*(Y) of the hue measurement print image printed on the print medium are values measured

by using an underlay made by stacking five sheets of white paper as a first underlay for the print medium, the white paper as the first underlay satisfying

96.3≤ L *( W )≤96.8,

1.7≤ a *( W )≤2.0, and

−5.6≤ b *( W )≤−5.2

where L*(W), a*(W) and b*(W) respectively represent an L* value, the a* value and the b* value in the L*a*b* color model, and

by setting a color model setting at the L*a*b* color model, setting an observation light source setting at D50, and setting a viewing angle setting at 2° in a measuring instrument used for the measurement of the hue of the hue measurement print image printed on the print medium.

5. The toner according to claim 1 , wherein

optical density of the hue measurement print image printed on the print medium is a value measured

by using black paper as an underlay for the print medium, the black paper satisfying

25.1≤ L *( B )≤25.9,

0.2≤ a *( B )≤0.3, and

0.5≤ b *( B )≤0.7

where L*(B), a*(B) and b*(B) respectively represent an L* value, the a* value and the b* value in the L*a*b* color model, and

by setting a status setting at status I, setting a white reference setting at absolute white reference, and setting a filer setting at no polarizing filter in a measuring instrument used for the measurement of the optical density of the hue measurement print image.

6. The toner according to claim 1 , wherein

the light resistance F is percentage representation of a value obtained by dividing second optical density of the light resistance measurement print image with the toner after the irradiation test by first optical density of the light resistance measurement print image with the toner before the irradiation test, and

the first optical density and the second optical density are values measured

by using an underlay made by stacking five sheets of white paper as a second underlay for the print medium of the light resistance measurement print image, the white paper as the second underlay satisfying

96.3≤ L *( W )≤96.8,

1.7≤ a *( W )≤2.0, and

−5.6≤ b *( W )≤−5.2

where L*(W), a*(W) and b*(W) respectively represent an L* value, the a* value and the b* value in the L*a*b* color model, and

by setting a status setting at status I, setting a white reference setting at absolute white reference, and setting a filer setting at no polarizing filter in a measuring instrument used for the measurement of the optical density of the light resistance measurement print image.

7. The toner according to claim 1 ,

wherein the toner is configured so that sublimation resistance Sr of a sublimation resistance measurement print image printed on the print medium with the toner, after a heating test heating the sublimation resistance measurement print image on a heat source at 180° C. for 10 minutes, satisfies

Sr≥98%, and

the sublimation resistance Sr is obtained as

Sr (%)=( b *( E )/ b *( S ))×100(%)

where b*(E) represents the b* value of a 100% density image with the toner after the heating test and b*(S) represents the b* value of the 100% density image with the toner before the heating test, and

wherein the toner is configured so that the b* value of a thermocompression bonding transferability measurement print image with the toner printed on transfer paper for thermocompression bonding transfer, after undergoing a press at 180° C. and 60 psi for 10 seconds, satisfies

b*≤ 2.9.

8. The toner according to claim 7 , wherein

the coloring agent includes a plurality of pigments, and

the plurality of pigments include C.I. Pigment Yellow 155 and C.I. Pigment Yellow 185.

9. The toner according to claim 8 , wherein a mixture ratio of the C.I. Pigment Yellow 155 and the C.I. Pigment Yellow 185 is within a range from 73:27 to 80:20.

10. The toner according to claim 7 , wherein

the a*(Y) and the b*(Y) of the hue measurement print image printed on the print medium are measured by

using white paper weighing 80 g/m 2 as an underlay for the print medium, the white paper satisfying

96.3≤ L *( W )≤96.8,

1.7≤ a *( W )≤2.0,

−5.6≤ b *( W )≤−5.2, and

78.0 (sec)≤Beck smoothness≤129.3 (sec)

where L*(W), a*(W) and b*(W) respectively represent an L* value, the a* value and the b* value in the L*a*b* color model,

using status I stipulated in ISO, absolute white reference, and no polarizing filter as conditions of density measurement in a measuring instrument used for the measurement of the optical density of the hue measurement print image, and

using the hue measurement print image with the toner printed so that yellow optical density equals 1.4.

11. The toner according to claim 7 , wherein

the b*(S) and the b*(E) of the sublimation resistance measurement print image printed on the print medium are measured by

using black paper as an underlay, the black paper satisfying

25.1≤ L *( B )≤25.9,

0.2≤ a *( B )≤0.3, and

0.5≤ b *( B )≤0.7

where L*(B), a*(B) and b*(B) respectively represent an L* value, the a* value and the b* value in the L*a*b* color model,

using status I stipulated in ISO, absolute white reference, and no polarizing filter as conditions of density measurement in a measuring instrument used for the measurement of the optical density of the hue measurement print image, and

using the sublimation resistance measurement print image with the toner printed so that yellow optical density equals 1.4.

12. The toner according to claim 1 , wherein the binder resin is styrene-acrylic copolymer resin.

13. A toner cartridge comprising:

a toner storage container that can be attached to a development device for supplying a toner to a surface of an image bearing body; and

a toner that is being stored in the toner storage container,

wherein the toner that is being stored in the toner storage container is the toner according to claim 1 .

14. A development device comprising:

a toner storage part;

a toner that is being stored in the toner storage part; and

a toner bearing body that supplies the toner that is being stored in the toner storage part to a surface of an image bearing body bearing an electrostatic latent image,

wherein the toner that is being stored in the toner storage part is the toner according to claim 1 .

15. An image forming apparatus comprising:

an image bearing body that bears an electrostatic latent image;

a development device including a toner storage part;

a toner that is being stored in the toner storage part; and

a transfer unit that transfers a toner image foamed on the image bearing body by the toner supplied from the development device, onto a print medium,

wherein the toner that is being stored in the toner storage part is the toner according to claim 1 .