As computer application technologies have become widespread in recent years, various types of documents and images are being produced using computers, and are being printed using printers. Such printers include, for example, dot-matrix impact printers, laser printers, thermal printers, inkjet printers, and the like. Among these printers, laser printers, which use a laser beam in printing (also referred to as electrophotography), and inkjet printers are widely used by general consumers because of their high printing speeds and their ability to print high-resolution images.
Electrophotography, when used in copiers and/or printers, generally has several imaging processing steps. A photoconductive drum or belt is charged to a constant potential in a dark environment. A Laser beam is irradiated on the charged surface of the photoconductive drum or belt to form electrostatic latent images thereon. The electrostatic latent images are developed with developer, e.g., charged toner, where the toner is transferred onto the electrostatic latent images formed on the photoconductive drum or belt by, e.g., electrostatic force, to form toner images.
A recording medium is made to move past the photoconductive drum or the belt so that the toner image is transferred therefrom onto the recording medium. The recording medium may be conductive, at least to some extent, in order for the toner images to be transferred thereto by electrostatic force. The toner image transferred to the recording medium is fixed thereon by a hot fusing process in which heat and pressure are applied to the recording medium typically with the use of one or more rollers.
Electrophotographic printers employing the electrophotography process generally described above can use various recording media, including paper. With improvements in the performance of toner that is used in electrophotographic printers, and with enhancements in the transferring and fixing technologies, recording media suitable for use in electrophotographic printers have become more widely available. For example, highly glossy recording medium is available for use with inkjet printers.
Generally, a sheet of paper or printing medium suitable for use with electrophotographic printers is formed by coating a toner fixing layer on one side or on both sides of a base layer. More particularly, a filler and a binder resin are mixed in a suitable ratio to prepare a composition used to form the toner fixing layer. The composition is then coated on the base layer. Such a toner fixing layer enables a printing medium used for electrophotographic printers to have excellent smoothness and glossiness compared to ordinary paper. The smoothness and the glossiness of the recording media may affect the print glossiness during printing, and could significantly influence the print quality.
To increase the smoothness and the glossiness of a conventional electrophotographic recording medium, an inorganic material having small-sized particles can be used or attempts to improve the conditions, e.g., temperature and pressure conditions, during the calendering process can be made. However, when an inorganic material having small-sized particles is used in a conventional electrophotographic recording medium, the cost may become disadvantageously high and/or it may be difficult to treat the inorganic material due to the small particle size. When, an inorganic material of a large particle size is used, on the other hand, a calendering process may be required.
During the calendering process, the temperature and pressure are adjusted to achieve a varying degree of thickness, smoothness and/or glossiness of recording media. More particularly, the calendering process enables the heat and the pressure that is applied to a recording medium to improve the smoothness of a surface of the recording medium. Generally, as the smoothness of the surface improves, the glossiness of the surface is also improved.
As the temperature and the pressure increase, the thickness of the recording media decreases while the smoothness and the glossiness of the recording media improve. Excessively high temperature and/or pressure, however, can be a source of problems in the manufacturing of the recording media. An inappropriate choice of the base layer can also influence the toner fixing layer. It may thus be generally advantageous to apply suitably temperature and/or pressure.
As another attempt to improve upon the glossiness of recording media, a plastic pigment can be used to form a toner fixing layer so as to improve the glossiness, the opacity and the printability of the recording media. However, such use of plastic pigments to yield high glossiness may also require a calendering process.