A decolorizable toner allows for easy distinguishing between a sheet which can be reused and a sheet which is hardly able to be reused from each other. The decolorizable toner includes a color developable compound, a color developing agent, a decolorizing agent, a magnetic material, and a binder resin. The color developable compound is a precursor compound of a dye. The color developing agent is an electron accepting compound which donates a proton to the color developable compound. The decolorizing agent is a compound which inhibits a coloring reaction between the color developable compound and the color developing agent.

A positively chargeable toner includes toner particles. The toner particles each include a toner mother particle and an external additive attached to a surface of the toner mother particle. The toner mother particle includes a polyester resin having an acid value of at least 10.0 mgKOH/g, a compound having a quaternary ammonium cation group, and strontium titanate particles. The external additive includes no strontium titanate particles.

A decolorizable toner allows for easy distinguishing between a sheet which can be reused and a sheet which is hardly able to be reused from each other. The decolorizable toner includes a color developable compound, a color developing agent, a decolorizing agent, a magnetic material, and a binder resin. The color developable compound is a precursor compound of a dye. The color developing agent is an electron accepting compound which donates a proton to the color developable compound. The decolorizing agent is a compound which inhibits a coloring reaction between the color developable compound and the color developing agent.

A magnetic toner comprising a magnetic toner particle including a binder resin, a magnetic body and a crystalline polyester, wherein a storage elastic modulus E(40) [Pa] at 40 C. and a storage elastic modulus E(85) [Pa] at 85 C., which are obtained in a powder dynamic viscoelasticity measurement of the magnetic toner, satisfy the following formulas (1) to (3).

E(40)6.010.sup.9 (1)

E(85)5.510.sup.9 (2)

[E(40)E(85)]100/E(40) (3)

A toner including a toner particle that contains a binder resin, and an inorganic fine particle, wherein the inorganic fine particle contains aggregated particles; the aggregated particles contain primary particles of at least one metal salt selected from the group consisting of titanate metal salts and zirconate metal salts; the primary particles have a number-average particle diameter of from 15 nm to 55 nm; the aggregated particles have an aggregation diameter of from 80 nm to 300 nm, the aggregated particles have a volume resistivity of from 210.sup.9 .Math.cm to 210.sup.13 .Math.cm; and the aggregated particles cover a surface of the toner particle, and a coverage ratio of the aggregated particles with respect to the surface of the toner particle is from 0.3 area % to 10.0 area %.

The present invention provides: a ferrite carrier core material for an electrophotographic developer, the material having a mesh passing amount of 3 wt % or less as indicated by the ratio of the weight of particles passing through a 16 m-mesh to the weight of whole particles constituting a powder, and having a particle strength index of 2 wt % or less as indicated by a difference between the mesh passing amounts before and after crushing; a ferrite carrier which is for an electrophotographic developer and in which the surface of the ferrite carrier core material is coated with a resin; and an electrophotographic developer which includes the ferrite carrier and a toner.

A magnetic toner is provided, which has a magnetic toner particle containing a binder resin, a wax, and a magnetic body, wherein, when Dn is a number-average particle diameter of the toner, CV1 is coefficient of variation of a brightness variance value of the toner in a particle diameter range of Dn 0.500 to +0.500, and CV2 is coefficient of variation of a brightness variance value of the toner in a particle diameter range of Dn 1.500 to 0.500, a relationship CV2/CV11.00 is satisfied; an average brightness of the toner in the range of Dn 0.500 to +0.500 is 30.0 to 60.0; and when, in a cross section of the toner observed using a transmission electron microscope, which is divided with a square grid having a side of 0.8 m, coefficient of variation CV3 of an occupied area percentage for the magnetic body is 40.0 to 80.0%.

A toner comprising a binder resin and a colorant, wherein the toner has a Martens hardness, as measured at a maximum load condition of 2.010.sup.4 N, of from 200 MPa to 1,100 MPa.

The present invention provides a three-dimensional printing article for making dental products and the preparation method thereof, which comprises: Ethoxylated bisphenol A dimethacrylate, Diurethane dimethacrylate, Triethylene glycol dimethacrylate, and Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide. It not only improves the present time-consuming and labor-intensive dental device making, but also can be used in mass production of dental devices.

Provided is a magnetic toner having a toner particle containing a binder resin and a magnetic body, wherein the binder resin contains a polymer A having a first monomer unit and a second monomer unit, the first polymerizable monomer is at least one selected from the group consisting of the (meth)acrylic acid esters having C.sub.18-36 alkyl groups, a content of the first monomer unit and a content of the second monomer unit based on the total moles of all monomer units in the polymer A are respectively 5.0 to 60.0 mol % and 20.0 to 95.0 mol %, and assuming that an SP value of the first monomer unit and the second monomer unit are taken as SP.sub.11 (J/cm.sup.3).sup.0.5 and SP.sub.21(J/cm.sup.3).sup.0.5, respectively, 3.00(SP.sub.21SP.sub.11)25.00 is satisfied, and an oil absorption of the magnetic body is 5 to 40 ml/100 g.