Typically, printers as output devices for computers and for digital images may be classified into thermal transfer printers, ink jet printers, laser printers, and so forth, according to recording methods. Thermal transfer printers use an ink sheet and a recording sheet to print images in dotted lines on the recording sheet by selectively driving a plurality of heating elements aligned in a main-scanning direction while conveying the ink sheet and the recording sheet in a sub-scanning direction. In recent years, thermal transfer printers have been gaining popularity as image input devices with the development of digital cameras, digital video cameras, scanners, and the like. Thermal transfer printers are suitable for printing image information captured by an image pickup apparatus such as a digital camera or a digital video camera which records still images, by utilizing a computer or a recording medium.
Ink jet printers uses binary printing, namely, whether or not forming dots. Small dots are formed on a recording sheet, and apparent resolution and gradation are provided by error diffusion or other methods. In contrast, thermal transfer printers easily control a heat value for each pixel. Accordingly, each pixel may have wide gradation. Thus, thermal transfer printers are advantageous in the production of smooth and high-quality images compared with other printers such as ink jet printers. In addition, since the performance of thermal heads and the characteristics of recording sheets are excellent, thermal transfer printers can print images having a finishing quality as high as that of pictures obtained by silver salt cameras. Because of this, thermal transfer printers have been gaining popularity particularly as printers for obtaining natural images, in parallel with the development of the digital camera in recent years.
There is also a system that allows printing of image information captured by an image pickup apparatus, by direct communication of a thermal transfer printer with an image pickup apparatus without the use of a computer or a recording medium. Such a system allows the image pickup apparatus to set parameters for printing, and hence, it is possible to print the image information easily, thereby making the thermal transfer printer more attractive to users.
In a thermal transfer method, a plurality of colors of ink are repeatedly transferred to a recording sheet in a case of full-color printing. Typical configurations for the full-color printing will be described below.
A first exemplary configuration of a thermal transfer printer of the related art is shown in FIGS. 32A and 32B. As shown in FIG. 32A, the uppermost recording sheet set in a recording sheet cassette 107 is separated and fed by a sheet feed roller 108 and a separating unit 109, and conveyed to a position between a thermal head 104 and a platen roller 105. A printing operation starts with winding of the recording sheet P around the platen roller 105. Then, an ink sheet 106 and the recording sheet P are pressed by the thermal head 104 and the platen roller 105. The platen roller 105 has an outer circumference comparatively larger than the whole length of the recording sheet P. The thermal head 104 generates heat to transfer ink applied on the ink sheet 106 to the recording sheet P while the platen roller 105 is rotated. As shown in FIG. 32B, to print the next color after the first color is printed, the pressure of the thermal head 104 is released, the platen roller 105 is rotated to convey the recording sheet P to a print start position, and the remaining colors are printed in the same manner as that of the first color. Full-color printing is performed with the colors yellow, magenta and cyan.
A second exemplary configuration of a thermal transfer printer of the related art is shown in FIGS. 33A and 33B. As shown in FIG. 33A, the uppermost recording sheet set in a sheet cassette 201 is separated and fed by a sheet feed roller 202 and a separating unit 203, and conveyed to a position between a thermal head 204 and a platen roller 205. A printing operation starts with pressing of an ink sheet 206 and the recording sheet P by the thermal head 204 and the platen roller 205. Then, the thermal head 204 generates heat to transfer ink applied on the ink sheet 206 to the recording sheet P while a pair of rollers disposed downstream in a print direction, i.e., a capstan roller 207 and a pinch roller 208, convey the recording sheet P. As shown in FIG. 33B, the next color is printed after the first color is printed. The pressure of the thermal head 204 is released, the capstan roller 207 and the pinch roller 208 are rotated in the reverse direction to the printing direction to return the recording sheet P to the print start position, and the remaining colors are printed in the same manner as that of the first color. Full-color printing is performed with the colors yellow, magenta and cyan.
In either one of the examples shown in FIGS. 32A, 32B, 33A and 33B, the recording sheet and the ink sheet in the sheet cassette are consumable supplies, and they are required to be replaced or supplied when consumed. Generally, an ink sheet is provided to a user in the form of a cartridge in which both ends of the ink sheet are wound around two bobbins and such bobbins with the ink sheet are accommodated in a frame (110 in FIG. 32A or 210 in FIG. 33A). The cartridge has a space 110a in FIG. 32A or a space 201a in FIG. 33A. When the cartridge is inserted, the cartridge is guided and mounted in place such that the thermal head 104 or 204 provided in a main body is accommodated in the space 110a or 201a. 
The above-described two examples are typical printing methods. The first example has a problem in that the size of the printer is increased since a platen roller having an outer circumference comparatively larger than the whole length of the recording sheet P is necessary, and a problem in that the configuration of the printer is complicated since the printer requires a mechanism (not shown in FIGS. 32A and 32B) that winds a recording sheet around the platen roller and holds the recording sheet. Meanwhile, the first example has an advantage of a decrease in print time since a print start portion for the second color is provided directly behind a print end position of the first color, and thus the time required for returning the recording sheet as in the second example is not necessary. In contrast, the second example has a problem in that the print time is increased, but it has an advantage of miniaturization and simplification of the printer.
The aforementioned thermal transfer printer uses as the recording sheet a special sheet for thermal transfer printing having a surface that allows ink to be easily transferred thereto, for realizing fine printing. Hence, a set product of fifty recording sheets with an ink cartridge accommodating an ink sheet for the fifty recording sheets is commercially available. The user unpacks the recording sheets and the ink cartridge of the purchased set product, and applies the ink cartridge to the main body while applying the recording sheets to the sheet cassette when using the printer. This is labour intensive.
In the case of a thermal transfer printer, the ink sheet may be effectively used if the ink sheet is prepared so as to be of a size in accordance with the size of the recording sheet as shown in FIG. 34. For example, there are commercially provided a set product of A6 size recording sheets with an ink cartridge accommodating an ink sheet for A6 size, and a set product of A7 size recording sheets with an ink cartridge accommodating an ink sheet for A7 size. The user may purchase either set product according to the purpose. To perform A7 size printing after A6 size printing, the A6 size recording sheets as well as the ink cartridge accommodating the ink sheet for A6 size are removed, and the A7 size recording sheets as well as the ink cartridge accommodating the ink sheet for A7 size are mounted. At this time, the removed A6 size recording sheets and the removed ink cartridge accommodating the ink sheet for A6 size must be stored until they are used again. Therefore, since the ink cartridge and the recording sheets are separately provided, and the recording sheets and the ink cartridge should not be exposed to dust and direct sunlight, they must be stored in storage bags or the like. This is also labour intensive work.
To address these problems, there is provided a cartridge in which an ink sheet and recording sheets are provided together in an integrated manner, as disclosed in Japanese Patent Laid-Open Nos. 2-81660 and 2000-108442.
As disclosed in Japanese Patent Laid-Open No. 2-81660, an ink cartridge and a sheet cassette are integrated. However, a printing operation may not be performed while the ink sheet is accommodated in the cartridge. To perform the printing operation, a mechanism that draws the ink sheet from the cartridge and brings the ink sheet to a print position is necessary. The complexity of the printer may thus be increased, and there may be a decrease in reliability due to this mechanism being introduced. The problem of the configuration disclosed in Japanese Patent Laid-Open No. 2-81660 is addressed by a configuration disclosed in Japanese Patent Laid-Open No. 2000-108442. This configuration performs a printing operation without an ink sheet brought to a print position after the integrated cartridge is mounted. Therefore, the user will not face the troublesome work of separately supplying the ink sheet and the recording sheets, or that of separately storing the ink sheet and the recording sheets removed when different sized recording sheets are supplied. However, when photo printing is the primary purpose, a sheet to be used has a predetermined thickness for securing conservation property, durability, and print quality. Owing to this, if such a sheet is strongly bent or the like upon conveyance for printing, a print surface thereof may be damaged or wrinkled. In addition, for example, such a thick recording sheet is separated from the cassette by separation with pawls, and the sheet may not be reliably separated if a sufficient space for bending the recording sheet is not provided. In Japanese Patent Laid-Open No. 2000-108442, a conveyance path of the sheet is formed with a cassette. The exterior of the cassette has a curved portion with a comparatively large radius so that the sheet will not be strongly bent for preventing damage to the sheet and improving the reliability of the conveyance of the sheet. However, the inside of the curved portion of the cassette for providing the conveyance path is not utilized. In addition, a certain thickness of the cassette is necessary for providing a gently bent conveyance path, and hence, miniaturization is limited. Accordingly, the accommodation of the recording sheets requires a space larger than that necessary for the ink sheet, thereby causing an increase in the size of the main body of the printer.
The present invention provides an integrated ink-and-paper cassette for a compact printer with high usability that may address these problems.
Typically, in dye sublimation printing, which is a thermal transfer printing method, a platen roller and a thermal head are pressed together with an ink sheet and a recording sheet interposed therebetween in printing. Due to this, the ink sheet is taken up while being strongly pulled in printing. At this time, since the ink-and-paper cassette partly comes into contact with the ink sheet near the ink-sheet conveyance path, the cassette may receive a tension due to the ink sheet, and become bent or deformed if its rigidity is insufficient. Accordingly, conveyance of the ink sheet may be unstable.
Due to production restrictions, the integrated ink-and-paper cassette is usually composed of two casings including one for a recording sheet housing and one for an ink-sheet housing, or more than two casings. However, since the cassette involves an eject function for the recording sheet, a plurality of openings are necessary, which may degrade the rigidity of the casings. Further, in procedural steps, two frames are easily coupled if, for instance, the coupling is made using pawls and holes utilizing elastic deformation of resin material. However, it is difficult to maintain the required rigidity of the whole cassette.
The present invention provides an integrated ink-and-paper cassette for a compact printer with high usability. Also, the present invention provides a cassette for a printer that may maintain rigidity and avoid deformation due to a load in printing.