1. Technical Field
The present invention relates to an image-forming method of forming an image on a recording medium such as a plastic sheet in an electrophotographic process, and an image-forming apparatus such as a copying machine or a printer using the same.
2. Related Art
In electrophotographic processes, a color image has been formed, for example, in the following image-forming steps. Light is first irradiated on a color manuscript; the reflected optical image is detected by a color CCD with color separation; and image signals for multiple colors are obtained in an image-processor after predetermined image processing and color correction. For example, semiconductor laser is modulated based on the image signals for multiple colors, and semiconductor laser light modulated according to the image signals is emitted from the semiconductor laser. Multiple electrostatic latent images are formed on a photoreceptor by irradiating the laser beam multiple times each for one of the colors. The multiple electrostatic latent images are developed sequentially with color toners, for example in four colors of yellow (Y), magenta (M), cyan (C), and black (K). The developed toner images are then transferred from the photoreceptor onto an image-receiving medium such as paper and are heat-fixed with a fixing device having an heat-fixing roll or the like, to form a color image on the image-receiving medium.
The color toners used in these color image-forming apparatuses are, for example, particles having an average diameter of 1 to 15 μm made of a binder resin such as polyester resin, styrene/acrylic copolymer, or styrene/butadiene copolymer containing a colorant dispersed therein, on which fine particles having an average diameter of approximately 5 to 100 nm, for example inorganic fine particles such as of silicon oxide, titanium oxide, or aluminum oxide or resin fine particles such as of PMMA or PVDF are adhered. Examples of the colorant include yellow (Y) colorants such as benzidine yellow, quinoline yellow, and Hanza Yellow; magenta (M) colorants such as rhodamine B, rose bengal, and pigment red; cyan (C) colorants such as phthalocyanine blue, aniline blue, and pigment blue; black (K) colorants such as carbon black and aniline black; blends of color pigments; and the like.
The thus-obtained color image made of the color toners has a certain degree of glossiness since the surface thereof is smoothened at heat fixation. On the other hand, the paper surface is normally not glossy; and thus, the color image has a different glossiness from that of the paper surface. In addition, the glossiness of the color image is known to change as a result of variation of the viscosity of the toner at heat fixation depending on the kind of the binder resin used for color toner and the method of heat fixing.
By the way, preferred glossiness of a color image varies depending on the kind and application of the image. For example, when the color image is formed on a plastic sheet such as a display board or an outdoor display, a color image having a uniform surface higher in glossiness is generally preferred.