An apparatus is provided for controlling a liquid electrophotography printer (LEP). The LEP may include a plurality of ink developers, IDs, to transfer charged ink to a photoreceptor, by virtue of a potential difference between the engaged ID and the photoreceptor selectively dischargeable to allow an image to be formed on a print medium in use through printing a spread of plural color separations thereon each corresponding to ink from one of a plurality of engaged IDs. the apparatus may comprise a print controller to, in use monitor an order of color separations to be printed onto the print medium. The print controller may also detect in the order of color separations an empty separation of an ID followed by a printing separation of the same ID, an empty separation representing a separation in which no image is formed on the photoreceptor and the engaged ID is at a voltage different to the voltage of the ID for a printing separation so as to, in the empty separation, substantially wet the photoreceptor and substantially not transfer ink thereto. The print controller may also, in response to the detection, replace in the order of the color separations the ID for the empty separation with a different ID.

In one example, a developer roller for liquid electrophotographic printing includes a cylindrical metal inner core, a rigid conductive plastic outer core surrounding the inner core, and a compliant exterior surrounding the outer core.

In some examples, a printing liquid developer includes a developer roller that has a hollow tubular base body formed of a material including conductive carbon fiber, a conductive, compliant layer around an outer surface of the hollow tubular base body, and an electrically conductive support separate from the hollow tubular base body and electrically contacted to a surface of the hollow tubular base body.

A printing apparatus is described in which a guide member biases a printing substrate against a plurality of electrodes comprised in an electrode array of the printing apparatus. A layer of wet printing fluid is comprised in the printing substrate. Based on an output of the electrode array when the plurality of electrodes is in electrical contact with the printing substrate, an index of a thickness of the layer of wet printing fluid is determined by processing circuitry of the printing apparatus.

In an example, a method of wetting a print blanket includes receiving a null cycle trigger during a printing session. The method also includes maintaining printing voltages on a forecast BID (binary ink developer) that has been prepared to print a next color separation onto a photoreceptor, and applying wet null voltages to a non-forecast BID. The method then includes engaging the non-forecast BID with the photoreceptor to transfer fluid other than ink to the photoreceptor during the null cycle.

An example method of performing a null cycle in a liquid electrographic printer is described. The method involves collecting, at a photo imaging plate cleaning station, imaging oil deposited on a photo imaging plate during a print cycle. During a null cycle, the photo imaging plate cleaning station is controlled to apply the collected imaging oil to the photo imaging plate.

Herein is described an electrophotographic printing process in which a liquid electrophotographic ink image and a dry electrophotographic toner image may be printed on a print substrate.

An image-forming apparatus includes an electrophotographic photosensitive member including a conductive base and a single-layer photosensitive layer disposed on the conductive base, the single-layer photosensitive layer including a binder resin, a charge-generating material, a hole-transporting material, and an electron-transporting material; and a developing unit including a developing roller that develops an electrostatic latent image formed on a surface of the electrophotographic photosensitive member with a developer including a toner in order to form a toner image, the developing roller being arranged to come into contact with the photosensitive layer. The ratio R/P of the content R [mass %] of the binder resin in the photosensitive layer to the pressing force P [N/mm] at which the developing roller is pressed against the photosensitive layer is about 11.5 or more and about 19.6 or less.

An apparatus is provided for controlling a liquid electrophotography printer (LEP). The LEP may include a plurality of ink developers, IDs, to transfer charged ink to a photoreceptor, by virtue of a potential difference between the engaged ID and the photoreceptor selectively dischargeable to allow an image to be formed on a print medium in use through printing a spread of plural colour separations thereon each corresponding to ink from one of a plurality of engaged IDs. the apparatus may comprise a print controller to, in use monitor an order of colour separations to be printed onto the print medium. The print controller may also detect in the order of colour separations an empty separation of an ID followed by a printing separation of the same ID, an empty separation representing a separation in which no image is formed on the photoreceptor and the engaged ID is at a voltage different to the voltage of the ID for a printing separation so as to, in the empty separation, substantially wet the photoreceptor and substantially not transfer ink thereto. The print controller may also, in response to the detection, replace in the order of the colour separations the ID for the empty separation with a different ID.

In an example, a method of wetting a print blanket includes receiving a null cycle trigger during a printing session. The method also includes maintaining printing voltages on a forecast BID (binary ink developer) that has been prepared to print a next color separation onto a photoreceptor, and applying wet null voltages to a non-forecast BID. The method then includes engaging the non-forecast BID with the photoreceptor to transfer fluid other than ink to the photoreceptor during the null cycle.