1. Field of the Invention
The present invention relates to an image processing method and an image processing apparatus, capable of recording high quality image having less printing bleeding.
2. Description of the Related Art
Image recording and image erasing on a thermoreversible recording medium as a recording medium have been carried out so far by a contact method in which a heating source is brought into contact with the thermoreversible recording medium to heat the thermoreversible recording medium. As the heating source, in the case of image recording, a thermal head is generally used, and in the case of image erasing, a heat roller, a ceramic heater or the like is generally used.
Such a contact image processing method has advantage in that, if a thermoreversible recording medium is a flexible material such as paper, an image can be uniformly recorded and erased by evenly pressing a heating source against the thermoreversible recording medium with use of a platen etc., and an image erasing device can be produced at low costs by using components of a conventional thermosensitive printer.
However, when an RF-ID tag as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2004-265247 and Japanese Patent (JP-B) No. 3998193 is embedded in a thermoreversible recording medium, the thermoreversible recording medium needs to be thickened and the flexibility thereof degrades, and thus high pressure is required for uniformly pressing a heat source against the thermoreversible recording medium. In addition, in the contact image processing method, a surface of the thermoreversible recording medium is scraped due to repetitive printing and erasure and irregularities are formed therein, and some parts are not in contact with a heating source, such as a thermal head, and hot stamp. Thus, the thermoreversible recording medium may not be uniformly heated, causing degradation in image density and erasing failure (see Japanese Patent (JP-B) No. 3161199 and Japanese Patent Application Laid-Open (JP-A) No. 09-30118).
In view of the fact that RF-ID tag enables reading and rewriting of memory information from some distance away from a thermoreversible recording medium in a non-contact manner, a demand arises for thermoreversible recording media as well. The demand is that an image be rewritten on such a thermoreversible recording medium from some distance away from the thermoreversible recording medium. To respond to the demand, a method using a laser is proposed as a method of uniformly recording and erasing each image on a thermoreversible recording medium from some distance away from the thermoreversible recording medium or when there are irregularities on the surface thereof (see JP-A No. 2000-136022). It is the method by which non-contact recording is performed by using thermoreversible recording media on shipping containers used for physical distribution lines. Writing is performed by using a laser and erasing is performed by using a hot air, heated water, infrared heater, etc.
As such a recording method using a laser, a laser-recording device (laser maker) is proposed by which a thermoreversible recording medium is irradiated with a high-power laser light to control the irradiation position. A thermoreversible recording medium is irradiated with a laser light using the laser marker, and a photothermal conversion material in the thermoreversible recording medium absorbs light so as to convert it into heat, which can record and erase an image. An image recording and erasing method using a laser has been proposed, wherein a recording medium including a leuco dye, a reversible developer and various photothermal conversion materials in combination is used, and recording is performed thereon using a near infrared laser light (see JP-A No. 11-151856).
According to the methods described in JP-A Nos. 2008-62506 and 2008-213439, a thermoreversible recording medium can be uniformly heated, and image quality and durability against repeated use can be improved. However, there is a problem that the time required for image recording and erasing becomes long, due to jump and waiting time between drawing lines.
On the other hand, as a method of printing without rewriting, there are exemplary methods as follows: a printing method in which a surface of a product, such as a plastic, a semiconductor, etc. is irradiated with a laser beam, and then the surface absorbs the laser beam so as to generate heat, which causes deformation, modification and removal, to thereby perform printing; and a printing method in which thermal recording paper for one recording is attached to a product, and then the paper is irradiated with a laser beam so as to partially heat a part to be printed. However, since printing is performed by heat, thermal diffusion adversely affects printing, and this causes a problem that when a small character is printed, character bleeding occurs, causing degradation of visibility.
Thus, at present there has not been provided an image processing method and an image processing apparatus, which can record high quality image having less bleeding, and attain durability against repeated use, by calculating a density of a character to be recorded based on information of a type, size, and line width of the character to be recorded, and adjusting an irradiation energy of the laser beam according to the density.