Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-07-14
2003-04-01
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S065000
Reexamination Certificate
active
06540327
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording head and the recording by an ink jet recording apparatus. More particularly, the invention relates to the ink jet recording head which uses ink having different densities for the same color series for recording images.
2. Related Background Art
With the wide use of an information processing apparatus, such as a copying machine, a word processor, a computer, and also, of communication equipment, an apparatus which digitally records images by use of a recording head of an ink jet method has rapidly become popular as one of the image formation apparatuses (hereinafter referred to as recording apparatus) serving as information output means for these equipment. For a recording apparatus of the kind, it is generally practiced that the so-called multinozzle head, in which a plurality of ink discharge ports, liquid passages conductively connected to these ports, and others are integrated, is used as a recording element in order to improve the recording speed.
As a recording method of the kind, there is adopted for controlling a recording in an intermediate tone, a dot density control method with which to produce such an intermediate tone by controlling the number of recording dots per unit area by the application of the recording dots of a specific size, or a dot diameter control method with which to produce such an intermediate tone by controlling the sizes of the recording dots.
Here, the latter method which controls the dot diameters requires a complicated control to be carried out for the fine modification of the sizes of the recording dots, hence automatically restrict its implementation. In general, therefore, the former method which controls the dot densities is adopted.
The electro-thermal energy transducing elements, which make a high resolution possible, are used because of the ease with which to prepare the elements in a high density, but it is also difficult to control the amount of pressure variation, thus disabling the diameters of the recording dots to be modulated. For recording, therefore, the method for controlling dot density is adopted.
As one of the typical binarization methods for the intermediate tonal representation used for the dot density control method, an organizational design method may be employed. This method, however, has a problem that the number of gradations is limited by the matrix size. In other words, to increase the number of gradations, it is necessary to make the matrix size larger. If the matrix size is made larger, there is a problem encountered, among others, that one pixel of a recorded image consisting of one matrix becomes greater, thus spoiling the resolution. Also, there is a design method of a conditionally determining type, such as an error diffusion method as another typical type of binarization method. Whereas the aforesaid organizational design method is of an independently determining type for binarization using a threshold value which is not related to any input pixels, this type of method varies the threshold value in consideration of the surrounding pixels of an inputted pixel. The design method of a conditionally determining type which is represented by the error diffusion method has an excellent compatibility of tonality and resolution. Also, when an original image is a printed image, the creation of the moire pattern on the recording image is extremely small among other advantages, but, on the other hand, the graininess of the bright part of the image tends to become conspicuous, and a problem is encountered that the evaluation of the image quality is lowered. This problem is particularly conspicuous in a recording apparatus having a low recording density.
Therefore, in order to make the above-mentioned graininess less conspicuous, there is proposed a method for a conventional ink jet recording apparatus that the two recording heads, which discharge ink having a low density of a recorded image, and ink having a high density thereof, respectively, are provided so that the recording dots are formed with ink having a low density (light ink) for the bright part to the intermediate tonal part of an image, and also formed with ink having a high density (dark ink) for the intermediate tonal part to the dark part of the image.
FIG. 1
is a perspective view showing the principal part of a conventional color ink jet recording apparatus of a serial printing type which uses dark and light ink according to the above-mentioned recording method.
On a carriage
241
, there are respectively arranged at a given distance, a recording head Kk which discharges black dark ink; a recording head Ku, black light ink; a recording head Ck which discharges cyan dark ink; a recording head Cu, cyan light ink; a recording head Mk which discharges magenta dark ink; a recording head Mu, magenta light ink; and a recording head Yk which discharges dark yellow ink; a recording head Yu, yellow light ink. The carriage
241
is slidably supported by a guide shaft
243
to be guided to reciprocate along the above-mentioned guide shaft
243
by the driving force of a carriage motor
245
transmitted through a driving belt
244
.
In the liquid passages each conductively connected to the respective ink discharge port of each recording head, the heat generating elements (electro-thermal transducers) are arranged to generate the thermal energy used for discharging ink.
The ink used by each of the recording heads is retained in each of the ink cartridges
248
provided for the respective colors, and is supplied through each of the ink supply passages. Also, the control signals and driving signals are transmitted from an apparatus controller to the recording heads through a flexible cable
249
.
A recording material such a recording sheet or a plastic thin sheet is conveyed in the direction indicated by arrows in
FIG. 1
by means of a feed roller (not shown) and exhaust sheet rollers
242
when a feed motor (not shown) is driven. During this period, a recording is being executed on the surface of the recording material facing the recording heads along the traveling of each of the heads. In other words, in accordance with the reading timing of an encoder (not shown) which detects the traveling positions of the carriage
241
, the above-mentioned heat generating elements are driven on the basis of the recording signals to discharge each of the ink, black dark and light, cyan dark and light, magenta dark and light, and yellow dark and light, on the recording material in that order, thus enabling them to adhere thereto for recording images on the material.
In the home position defined outside the recording area in the carriage
241
travels, a recovery unit
246
is arranged with a capping unit
247
. With the recovery process by this recovery unit, the ink discharge characteristics are stabilized for each of the recording heads.
The conventional ink jet recording apparatus which uses the dark and light ink as described with reference to
FIG. 1
can solve the problem of the graininess of the recorded image comparatively well, and presents one of effective techniques in improving the quality of recorded image. However, there are roughly three problems still to be solved as described below.
1) Firstly, the conventional ink jet recording apparatus which uses the dark and light ink is at first provided with a recording head and an ink cartridge per ink to be used. Consequently, the number of recording heads and ink cartridges is increased, inevitably bringing about a larger size of the apparatus.
Also, the weight of the recording heads and the carriage is increased. At the same time, the distance required for the ramp up and down becomes long when the carriage travels, thus resulting likewise in the larger size of the apparatus. Also, due to.the increased weight, the load required to drive the carriage is increased, necessitating the provision of a driving motor having a greater torque. There is also a need for a complicated mechanism to maintain the capping performance
Akiyama Yuji
Gotoh Fumihiro
Hirabayashi Hiromitsu
Kanda Hidehiko
Kashino Toshio
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thinh
LandOfFree
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