Toner, two-component developer and image forming apparatus
A toner including: toner base particles; and an external additive, the toner base particles each comprising a binder resin and a colorant, wherein the external additive comprises non-spherical particles and spherical particles, wherein the non-spherical particles are each a secondary particle in which spherical primary particles are coalesced together, and wherein the non-spherical particles and the spherical particles in the external additive satisfy a relationship expressed by the following formula (1): 3 Ca (%)< Cb (%) Formula (1) where Ca is greater than 10% but smaller than 20% and Cb is greater than 40% but smaller than 70%, and Ca and Cb are values given by: Ca = ( an amount of the non - spherical particles ( % by mass ) / 100 ) × ( a projected area of the non - spherical particles ( cm 2 / g ) ) ( an amount of the toner base particles ( % by mass ) / 100 ) × ( a surface area of the toner base particles ( cm 2 / g ) ) × 100 Cb = ( an amount of the spherical particles ( % by mass ) / 100 ) × ( a projected area of the spherical particles ( cm 2 / g ) ) ( an amount of the toner base particles ( % by mass ) / 100 ) × ( a surface area of the toner base particles ( cm 2 / g ) ) × 100
1. A toner comprising:
toner base particles; and
an external additive,
the toner base particles each comprising a binder resin and a colorant,
wherein the external additive comprises non-spherical particles and spherical particles,
wherein the spherical particles comprise dry silica, and have an average particle diameter of 10 nm to 35 nm,
wherein the non-spherical particles comprise sol-gel silica and are each a secondary particle in which spherical primary particles are coalesced together, wherein the non-spherical particles have an average particle diameter of 60 nm to 480 nm, and
wherein the non-spherical particles and the spherical particles in the external additive satisfy a relationship expressed by the following formula (1):
3 Ca (%)< Cb (%) Formula (1)
where Ca is greater than 10% but smaller than 20% and Cb is greater than 40% but smaller than 70%, and Ca and Cb are values given by:
Ca
=
(
an
amount
of
the
non
-
spherical
particles
(
%
by
mass
)
/
100
)
×
(
a
projected
area
of
the
non
-
spherical
particles
(
cm
2
/
g
)
)
(
an
amount
of
the
toner
base
particles
(
%
by
mass
)
/
100
)
×
(
a
surface
area
of
the
toner
base
particles
(
cm
2
/
g
)
)
×
100
Cb
=
(
an
amount
of
the
spherical
particles
(
%
by
mass
)
/
100
)
×
(
a
projected
area
of
the
spherical
particles
(
cm
2
/
g
)
)
(
an
amount
of
the
toner
base
particles
(
%
by
mass
)
/
100
)
×
(
a
surface
area
of
the
toner
base
particles
(
cm
2
/
g
)
)
×
100
where the surface area of the toner base particles is a value given by: 6/(an average particle diameter of the toner x a specific gravity of the toner);
the projected area of the non-spherical particles is a value given by: 3/(2×an average particle diameter of the non-spherical particles x a specific gravity of the non-spherical particles); and
the projected area of the spherical particles is a value given by: 3/(2×an average particle diameter of the spherical particles x a specific gravity of the spherical particles).
2. The toner according to claim 1 ,
wherein the non-spherical particles have an average of degrees of coalescence of 1.7to 4.0, each of the degrees of coalescence being given by: a particle diameter of the secondary particle/an average particle diameter of the primary particles.
3. The toner according to claim 1 ,
wherein an amount of carbon remaining in the sol-gel silica and derived from an alkoxy group is 1% by mass or less.
4. The toner according to claim 1 ,
wherein an amount of water remaining in the sol-gel silica is 1% by mass or less.
5. The toner according to claim 1 ,
wherein the spherical particles further comprise titanium oxide.
6. The toner according to claim 1 ,
wherein the toner has a ratio Dv/Dn of 1.0 to 1.2 where Dv is a volume average particle diameter of the toner and Dn is a number average particle diameter.
7. A two-component developer comprising:
the toner according to claim 1 ; and
a carrier.