The present invention provides an electrophotographic toner binder containing, as a main component, a polymer whose constituent monomer is a monomer having an ethylenically unsaturated bond, the electrophotographic toner binder being excellent in low-temperature fixability, hot-offset resistance, and storage stability. The present invention provides an electrophotographic toner binder containing a polymer (A) containing a monomer (a) and a monomer (x) different from the monomer (a) as essential constituent monomers, wherein the monomer (a) is a (meth)acrylate having a C18-C36 acyclic hydrocarbon group, the polymer (A) has an acid value of 40 or less, and the polymer (A) satisfies the following relational expression (1):

1.1 (cal/cm.sup.3).sup.0.5|SP(x)SP(a)|8.0 (cal/cm.sup.3).sup.0.5relational expression (1):

wherein SP(a) is the SP value of a structural unit derived from the monomer (a) constituting the polymer (A); and
SP(x) is the SP value of a structural unit derived from the monomer (x) different from the monomer (a) constituting the polymer (A).

An electrostatic latent image developing toner includes a plurality of toner particles containing a binder resin. The binder resin has an amide bond and an ester bond. An area ratio of a peak originated from CO stretching of the amide bond to a peak originated from CO stretching of the ester bond is at least 0.00010 and no greater than 0.02000 in a FT-IR spectrum of the toner obtained by Fourier transform infrared spectroscopy analysis. The toner has a storage elastic modulus at 80 C. of at least 3.510.sup.4 Pa and no greater than 5.010.sup.4 Pa. The toner has a storage elastic modulus at 120 C. of at least 1.010.sup.3 Pa and no greater than 1010.sup.4 Pa. The toner has a storage elastic modulus at 150 C. of at least 1.010.sup.3 Pa and no greater than 1010.sup.4 Pa.

Toner particles each have a toner core, a shell layer covering a surface of the toner core, and first resin particles containing a melamine resin. A shell layer coverage is 60% to 80%. The first resin particles each have an embedded portion and a protrusion portion. The embedded portions are embedded beneath the surface of the toner core. The protrusion portions protrude outward from the surface of the toner core in a radial direction of the toner particle. An average value Wd of thicknesses b of the shell layers, a number average value Dp of embedment depths c of the first resin particles, and a number average value Pd of primary particle diameters d of the first resin particles satisfy relations (1) to (3) shown below.
0.2Dp/Pd0.8(1)
(PdDp)>Wd(2)
0.10 mPd1.00 m(3)

An electrostatic latent image developing toner includes a plurality of toner particles containing a binder resin. The binder resin has an amide bond and an ester bond. An area ratio of a peak originated from CO stretching of the amide bond to a peak originated from CO stretching of the ester bond is at least 0.00010 and no greater than 0.02000 in a FT-IR spectrum of the toner obtained by Fourier transform infrared spectroscopy analysis. The toner has a storage elastic modulus at 80 C. of at least 3.510.sup.4 Pa and no greater than 5.010.sup.4 Pa. The toner has a storage elastic modulus at 120 C. of at least 1.010.sup.3 Pa and no greater than 1010.sup.4 Pa. The toner has a storage elastic modulus at 150 C. of at least 1.010.sup.3 Pa and no greater than 1010.sup.4 Pa.

Toner particles each have a toner core, a shell layer covering a surface of the toner core, and first resin particles containing a melamine resin. A shell layer coverage is 60% to 80%. The first resin particles each have an embedded portion and a protrusion portion. The embedded portions are embedded beneath the surface of the toner core. The protrusion portions protrude outward from the surface of the toner core in a radial direction of the toner particle. An average value Wd of thicknesses b of the shell layers, a number average value Dp of embedment depths c of the first resin particles, and a number average value Pd of primary particle diameters d of the first resin particles satisfy relations (1) to (3) shown below.

0.2Dp/Pd0.8(1)

(PdDp)>Wd(2)

0.10 mPd1.00 m(3)

A part material for printing three-dimensional parts with an electrophotography-based additive manufacturing system, the part material including a composition having a copolymer (including acrylonitrile units, butadiene units, and aromatic units), a charge control agent, and a heat absorber. The part material is provided in a powder form having a controlled particle size, and is configured for use in the electrophotography-based additive manufacturing system having a layer transfusion assembly for printing the three-dimensional parts in a layer-by-layer manner.

A toner includes a plurality of toner particles (10) each including a toner mother particle (11) and a plurality of external additive particles (12) attached to a surface of the toner mother particle (11). The external additive particles (12) each include a silica particles (12a), a metal hydroxide layer, and a coating layer (12b). The metal hydroxide layer is disposed on a surface of the silica particle (12a). At least a part of the coating layer (12b) is disposed on a surface of the metal hydroxide layer. The coating layer (12b) is made substantially from a nitrogen containing resin.

A part material for printing three-dimensional parts with an electrophotography-based additive manufacturing system, the part material including a composition having a high-performance thermoplastic material and a charge control agent. The part material is provided in a powder form having a controlled particle size, and is configured for use in the electrophotography-based additive manufacturing system having a layer transfusion assembly for printing the three-dimensional parts in a layer-by-layer manner.

[Object] An object of the present invention is to provide a photoresponsive polymer that sufficiently secures photoresponsiveness to be fluidized by light irradiation and reversibly non-fluidized, improves fixability, and further has good color reproducibility. [Solution] Provided is a photoresponsive polymer containing a structural unit derived from an azomethine derivative represented by the following general formula (1), the photoresponsive polymer being fluidized by light irradiation and reversibly non-fluidized:
R.sub.1Z.sub.1Z.sub.2R.sub.2General formula (1): Z.sub.1 and Z.sub.2 are N or CH, while Z.sub.1Z.sub.2, R.sub.1 contains an aromatic hydrocarbon structure, R.sub.2 contains an aromatic heterocyclic structure, and a hydrogen atom is bonded to at least one carbon atom bonded adjacent to a carbon atom in the aromatic heterocyclic structure bonded to the Z.sub.2.

An image forming apparatus includes an image holding member, a first charging unit that charges a surface of the image holding member, a latent image forming unit that forms an electrostatic latent image on a charged surface of the image holding member, a second charging unit that charges a toner contained in a liquid developer, a developing unit that accommodates the liquid developer and develops the electrostatic latent image by using the liquid developer containing the toner charged by the second charging unit to form a toner image, a transfer unit that transfers the toner image to a recording medium, and a fixing unit that fixes the toner image to the recording medium. The liquid developer includes a toner in which a compound having a charge-accepting functional group has been bonded to a surface of toner particles, an ionization-controlling agent that ionizes the charge-accepting functional group, and a carrier liquid.