White toner, and image forming method and image forming apparatus using the white toner
A white toner has a first temperature range not less than 25° C. in which 60° glossiness is 10 or less between a fixable minimum temperature and a fixable maximum temperature thereof. The white toner has a second temperature range not less than 25° C. in which 60° glossiness is from 30 to 60 therebetween.
1. A white toner, comprising:
a first binder resin having a weight-average molecular weight of from 6,000 to 14,000 and an acid value of not greater than 12 mg KOH/g;
a second binder resin having a weight-average molecular weight of from 25,000 to 90,000 and an acid value of not less than 20 mg KOH/g;
a tri- or more valent metal salt; and
a titanium dioxide white pigment,
wherein a weight ratio of the first binder resin to the second binder resin is from 70/30 to 90/10.
2. The white toner of claim 1 ,
wherein the white toner has a first temperature range and a second temperature range between a fixable minimum temperature and a fixable maximum temperature,
an image formed by the white toner at a first temperature in the first temperature range has a 60° glossiness of 10 or less,
an image formed by the white toner at a second temperature in the second temperature range has a 60° glossiness of from 30 to 60, and
each of the first and second temperature ranges has a width of not less than 25° C.
3. The white toner of claim 1 , wherein each of the first binder resin and the second binder resin is a polyester resin.
4. An image forming method, comprising:
charging a surface of a photoreceptor;
irradiating the surface of the photoreceptor with imagewise light to form an electrostatic latent image thereon;
developing the electrostatic latent image with the white toner of claim 1 to form a white toner image on the photoreceptor;
transferring the white toner image onto a recording medium; and
fixing the white toner image on the recording medium.
5. An image forming apparatus, comprising:
a photoreceptor;
a charger configured to charge a surface of the photoreceptor;
an irradiator configured to irradiate the surface of the photoreceptor with imagewise light to form an electrostatic latent image thereon;
an image developer configured to develop the electrostatic latent image with the white toner of claim 1 to form a white toner image on the photoreceptor;
a transferer configured to transfer the white toner image onto a recording medium; and
a fixer configured to fix the white toner image on the recording medium.
6. The white toner of claim 1 , further comprising:
a crystalline polyester having a melting point of from 60 to 110° C.
7. The white toner of claim 1 , wherein the tri- or more valent metal salt comprises a tri- or more valent salicylic acid metal compound.
8. The white toner of claim 1 , wherein the first and second binder resins have a glass transition temperature of from 40 to 75° C.
9. The white toner of claim 1 , wherein the titanium dioxide white pigment is included in the white toner in an amount of from 37 to 45% by weight.
10. The white toner of claim 1 , wherein the titanium dioxide white pigment is surface treated with a polyol.
11. The white toner of claim 1 , further comprising:
a release agent comprising an monoester wax; and
a wax dispersant.
12. The white toner of claim 1 ,
wherein the first binder resin has the weight-average molecular weight of from 6,100 to 14,000, and the acid value of from 4 to 10 mg KOH/g, and
the second binder resin has the weight-average molecular weight of from 25,000 to 87,000, and the acid value of from 23 to 33 mg KOH/g.
13. The white toner of claim 11 ,
wherein an amount of the first binder resin included in the white toner is from 63 to 81 parts by mass per 100 parts by mass of a total of the first and second binder resins, the tri- or more valent metal salt, the release agent, and the wax dispersant, and
an amount of the second binder resin included in the white toner is from 9 to 27 parts by mass per 100 parts by mass of the total of the first and second binder resins, the tri- or more valent metal salt, the release agent, and the wax dispersant.
14. The white toner of claim 1 , wherein the titanium dioxide white pigment has a volume-average particle diameter of from 200 to 300 nm.
15. The white toner of claim 1 , further comprising:
an external additive comprising an inorganic particulate.
16. The white toner of claim 6 , wherein the first and second binder resins have a glass transition temperature of from 40 to 75° C.
17. The white toner of claim 12 ,
wherein an amount of the first binder resin included in the white toner is from 63 to 81 parts by mass per 100 parts by mass of a total of the first and second binder resins, the tri- or more valent metal salt, the release agent, and the wax dispersant, and
an amount of the second binder resin included in the white toner is from 9 to 27 parts by mass per 100 parts by mass of the total of the first and second binder resins, the tri- or more valent metal salt, the release agent, and the wax dispersant.
18. The white toner of claim 2 , further comprising:
a crystalline polyester having a melting point of from 60 to 110° C.
19. The white toner of claim 6 , wherein the crystalline polyester has an endothermic peak temperature of from 65 to 75° C.
20. A developing agent, comprising:
the toner of claim 1 ; and
a carrier,
wherein the development agent includes the carrier in an amount of from 1 to 15 parts by weight per 100 parts by weight of the carrier.