JPH111007A - Recorder and method for controlling recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record a high quality gradation image by using an ink jet recording head. SOLUTION: In a multi-pass recording, image recording is completed on a predetermined region on a recording medium such that the region is scanned plural times with an ink jet recording head to which a plurality of black inks each having a different concentration are supplied. Multi-value image data is inputted, then determination as to what kind of ink is to be used and how many times the ink is ejected to roughly the same pixel position is made in accordance with a density value of the inputted multi-value image data. The operation of the recording head is controlled such that the plural times of ink ejection is executed on the same pixel position on the recording medium in accordance with the determined result in each of the pass recording by the recording head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a recording apparatus and a recording control method, and more particularly to a recording apparatus and a recording control method for recording a gradation image using a recording head according to an ink jet system.

[0002]

2. Description of the Related Art As a recording method conventionally applied to a facsimile machine, a digital copying machine, a digital printer, etc., there are an electrophotographic system, a sublimation transfer system, a thermal transfer system, and an ink jet recording system. As a method of recording a gradation image by these methods, a recording head, a PWM,
A method of modulating a recording dot diameter formed by toner, ink, dye, or the like attached to a recording medium by changing a voltage or a pulse width applied to recording means such as a modulation laser light generation circuit, There is known a method of modulating the number of dots to be recorded in a unit matrix while keeping the number constant. Further, a gradation recording method using a combination of the above-described dot diameter modulation method and dot number modulation method is known.

[0003] Among the above-mentioned recording methods, an ink-jet recording method of recording ink on a recording medium with a simple device configuration and on demand has been rapidly spread in recent years.

In a recording apparatus to which this method is applied,
In order to improve the recording speed, a recording head (multi-nozzle recording head) composed of an ejection port array in which a plurality of ink ejection ports are integrated and arranged is used. Further, in order to cope with color printing, printing apparatuses having a plurality of multi-nozzle printing heads are increasing.

In this ink jet recording apparatus, it was difficult to modulate the diameter of the recording dots formed on the recording medium. Was recorded.
However, when such dot number modulation is used, there is a problem that it is difficult to record a high-gradation and high-resolution image.

When the recording dot diameter is relatively large,
There has been a problem that the granularity of the recorded image is conspicuous, and the image quality deteriorates. In this case, making the recording dot diameter smaller is a direct solution to this problem, but for that purpose, it is required to make the structure of the recording head finer, and its manufacture is technically difficult. In addition, there has been a problem that the manufacturing cost increases.

Therefore, in order to reduce the graininess and enhance the gradation expression ability, there has been proposed a method of recording a gradation image using inks of similar colors and different densities (dark and light inks). This method will be briefly described as follows.

[0008] That is, from the highlight portion to the halftone portion of the image, recording is performed using low density ink (light ink), and the halftone portion uses both low density ink and high density ink (dark ink). Printing is performed while printing is performed using ink having a high density from the halftone portion to the high density portion. By such recording, the granularity of the recorded image is reduced, and an image with good gradation can be recorded.

For printing using such dark and light inks, several methods of generating print data corresponding to printing with each ink have been proposed.

For example, when two types of light and dark inks are used, as shown in FIG.
It is common to process to select one of the types of ink. That is, when image data in which each pixel is represented by 8 bits is input, if the value is “255”, it indicates white, if it is “0”, it indicates black, and “254” to “254”.
If "1" represents halftone gray, light black ink (A) is used when the value is "255" to "128", and light black ink (A) is used when the value is "127" to "0". A) Or use dark black ink (B).

The density range "255" to "128"
In this case, as the density increases (the density value decreases), the probability of performing ink ejection with the light black ink (A) increases. In the density range “127” to “0”,
As the density increases (the density value decreases),
In, the probability of performing ink discharge with the light black ink (A) is reduced, while the probability of performing ink discharge with the dark black ink (B) is increased.

In this way, an image is recorded corresponding to inks having different densities, and as a result, an image with rich gradation is recorded.

In addition, a method of expressing a gradation by overlapping or combining dots formed by some dark and light inks with respect to a pixel matrix region in which substantially the same pixels or some pixels are aggregated. Is also common.

For example, as shown in FIG. 12, 16 gradations are expressed by using three types of inks having different densities having a predetermined density ratio and superimposing dots formed by these inks. Is possible. Further, since various combinations can be obtained by increasing the number of times of superposition or changing the density ratio of the prepared ink, it is possible to express more gradation values.

Further, it is possible to record a color image with rich gradation by applying such a dark and light ink to each color ink.

Now, the present invention is not limited to the ink jet recording method using such dark and light inks. In a general ink jet recording method, ink droplets discharged from ink discharge ports of a recording head form recording dots on a recording medium. Sometimes it is desired that the concentration be stable.

However, in actual printing, it is difficult to accurately form dots in a pixel matrix assumed in advance on a printing medium, and a streak occurs in the printed image in a direction parallel to the scanning direction of the printing head. Image quality was degraded.

In order to solve such a problem, conventionally, a division recording method has been proposed, and the total dots to be recorded in the pixel matrix are recorded in a time-division manner, or the recording order of the dots is changed. Or it has been proposed.

Many of such divided printing methods aim at isolating the dot positions formed by the ink droplets ejected in each scan of the recording head to reduce the influence between the ink droplets. In addition, Japanese Unexamined Patent Publication No.
Japanese Patent No. 40046 also proposes a divisional printing method in which printing is performed continuously in the scanning direction (main scanning direction) of the printhead. In this method, printing of the pixel matrix is completed by scanning the print head a plurality of times.

Further, the quality of an image recorded by the ink jet method will be examined.

For example, in the case where ink is ejected by applying heat to the ink by a heater at the ink ejection port portion of the recording head, the ink concentration is increased by evaporation of the volatile components of the ink remaining near the ink ejection port at the time of ejection. Alternatively, high or low density ink droplets may be ejected at the beginning of each scan of the print head until the heat supply from the heater is stabilized, resulting in deterioration of image quality.

The deterioration of the image quality is caused not only by the unstable ejection of the ink droplets but also by the difference in the properties of the recording medium.

For example, a recording medium such as a transparency film (transparent medium) generally has a relatively low ink absorption speed, and ink droplets discharged from a recording head and reaching the recording medium are applied to the medium. Before being absorbed, the ink droplets attract each other. As a result, the combination of these droplets creates a gourd-like droplet, and a plurality of ink droplets deviate from the originally intended position. Merged dots may be formed.
This phenomenon is a phenomenon that tends to occur in a recording medium having a relatively low ink absorption speed, and is called “beading”.

When this phenomenon is viewed macroscopically on an image recorded on a recording medium using a serial type recording head having a predetermined recording width, the following is observed.

That is, in the case of low-density (low duty) recording in which ink droplets do not contact each other, each ink droplet can be located at the center of a predetermined pixel position without affecting each other. Can be maintained independently of each other. On the other hand, when recording is performed at a high density (high duty) such that the ink droplets come into contact with each other, the ink droplets adjacent to each other aggregate and coalesce, and some of the ink droplets discharged to each pixel position are Are combined, some of them are kept independent, and the positions and shapes of the recording dots become uneven. Such unevenness is
Macroscopically, it appears as deterioration of image quality. For example, if the scanning direction of the print head and the arrangement direction of the ink ejection ports of the print head are different (for example, orthogonal), a "horizontal stripe" pattern appears on the print image, and the unevenness appears. .

[0026]

However, when a gradation image is expressed by a combination of dots formed by light and dark inks in a pixel matrix using a conventional divided recording method, the density of the light and dark inks is determined by the recording apparatus. However, there is a problem that the predetermined density cannot be accurately represented by a pixel matrix assumed in advance.

Further, since the positioning accuracy of the dots formed on the recording medium is low, if the gray scale is expressed by overlapping the inks of the same density, the gray scale is different from the assumed density.
There is also a problem that accurate gradation expression cannot be performed.

Further, when recording is performed on a recording medium such as a transparency film (transmission medium) by an ink jet method, if a large number of ink droplets are used in a small area in order to obtain a high density, a "beading" phenomenon occurs. Is remarkable, and there is a problem that image quality is deteriorated. For example, when recording is performed using CF102 (trade name: Canon inkjet recording paper) as a transparent medium, streaks may be observed in the recorded image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional example, and has as its object to provide a recording apparatus and a recording control method capable of recording a high-quality gradation image using an ink jet recording head. And

[0030]

In order to achieve the above object, a recording apparatus according to the present invention has the following arrangement.

That is, the present invention is directed to a recording apparatus which completes image recording by scanning the same region of a recording medium a plurality of times with a recording head conforming to an ink-jet system, and comprising a plurality of inks each storing a plurality of types of inks having similar colors and different densities. An ink tank,
Input means for inputting multi-valued image data; and any one of the plurality of types of ink at substantially the same pixel position on the recording medium in accordance with the density value of the multi-valued image data input by the input means. Determining means for determining how many times ink is to be ejected, and a plurality of ink ejections at substantially the same pixel position on the recording medium in one scan of the recording head based on a result of the determination by the first determining means. Control means for controlling the operation of the recording head so as to perform the recording.

Furthermore, based on the result of the determination by the first determining means, a second determining means for determining which kind of ink should be ejected in which scan among a plurality of scans may be added. good.

Preferably, the recording head has a plurality of ink discharge nozzle groups for discharging ink using each of the plurality of types of ink.

The control means controls the recording head to 10
It is preferable to drive the recording head at a driving frequency of 00 Hz or more. In one scan of the recording head, control may be performed so that ink of the same density is ejected. Alternatively, ink of the same density or ink of a different density may be controlled. May be controlled to be discharged.

Here, the recording medium is a transparent medium, a polyethylene terephthalate (PET) film is used as a base material of the medium, and a receiving layer containing alumina hydrate as an image receiving layer is provided on the base material. Is preferably provided.

The above-mentioned recording head is a recording head for discharging ink using thermal energy, and preferably includes a thermal energy converter for generating thermal energy to be applied to the ink.

Further, in the recording by the above-described multiple scans, the recording head scans the same area of the recording medium four times for recording, and the recording head performs two scans with respect to substantially the same pixel position in each scan. It is preferable to perform ink ejection twice.

According to another aspect of the present invention, ink is supplied from a plurality of ink tanks which respectively store a plurality of types of inks having similar colors and different densities, and a plurality of the same areas of a recording medium are recorded by a recording head according to an ink jet system. A printing control method for completing image printing by scanning multiple times, comprising: an input step of inputting multi-valued image data; and a density control unit for inputting multi-valued image data at substantially the same pixel position on the recording medium. A first determining step of determining which type of ink is to be ejected and how many times out of the plurality of types of ink, and performing the printing in one scan of the print head based on a determination result in the first determining step. A control step of controlling the operation of the recording head so that ink is ejected a plurality of times at substantially the same pixel position on the medium.

Further, based on the result of the determination in the first determining step, a second determining step of determining which kind of ink is to be ejected and in which scanning in a plurality of scannings may be added.

With the above arrangement, the present invention supplies ink from a plurality of ink tanks which respectively store a plurality of types of inks of the same color and different densities, and uses a recording head in accordance with an ink jet system to form the same area on a recording medium. In the printing that scans a plurality of times to complete image printing, multi-valued image data is input, and in accordance with the density value of the input multi-valued image data, at substantially the same pixel position on the printing medium, among the plurality of types of ink, Decide what kind of ink and how many times to eject,
Based on the result of the determination, the operation of the print head is controlled so that one scan of the print head ejects ink a plurality of times to substantially the same pixel position on the print medium.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a schematic configuration of a recording apparatus having a recording head for performing recording in accordance with an ink jet system, which is a typical embodiment of the present invention.

As shown in FIG. 1, a carriage (not shown)
Is slidable by a guide shaft 3. The rotation of the carriage motor 7 via the drive belt 6 allows the recording head 2 to reciprocate in the x direction (main scanning direction) along the guide shaft 3. The recording medium 1 is transported in the y-direction (sub-scanning direction) by a transport roller 8 and a paper discharge roller 9 driven by a transport motor (not shown). Then, an image is recorded on the recording medium 1 by ink ejected from the recording head 2 while moving in the main scanning direction.

In FIG. 1, reference numeral 10 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end, and serves as a cantilever. Although the blade 10 is disposed adjacent to the recording area of the recording head 2, in the example shown in FIG. 1, the blade 10 is held in a form protruding into the movement path of the recording head 2. Reference numeral 11 denotes a cap, which is disposed at a home position adjacent to the blade 10, moves in a direction perpendicular to the moving direction of the print head 2, comes into contact with the ink ejection surface of the print head, and caps the surface. ing.

Further, reference numeral 12 denotes an ink absorber provided adjacent to the blade 10, similarly to the blade 10, and held in a form protruding into the movement path of the recording head 2.
The blade 10, the cap 11, and the ink absorber 12 are included in the recovery unit 13, and the blade 10 and the ink absorber 12 remove moisture, dust, and the like from the ink ejection port surface. In addition, the recovery unit 13 performs preliminary ejection of the recording head 2 to stabilize the ink ejection characteristics of the recording head 2.

In the above configuration, when the recording head 2 returns to the home position at the end of recording or the like, the recovery unit 13
Is retracted from the movement path of the recording head 2, while the blade 10 protrudes into the movement path. As a result, the ink ejection surface of the recording head 2 is wiped. When capping is performed by contacting the cap 11 with the ink ejection surface of the recording head 2, the cap 11 moves so as to protrude into the moving path of the recording head 2.

On the other hand, when the recording head 2 moves from the home position to the recording start position, the cap 11 and the blade 10 are at the same position as the position at the time of wiping described above. As a result, even in this movement, the ink ejection surface of the recording head 2 is wiped.

FIG. 2 is a diagram showing the ink ejection surface of the recording head 2.

As shown in FIG. 2, the recording head 2 has four nozzle groups 2a to 2d having 64 ink ejection ports arranged in the y direction. These nozzle groups 2a to 2d are arranged in the x direction. Nozzle group 2a-
The ink discharge ports of each 2d are arranged at a density of 360 dpi (dot / inch). A heater is mounted on each of the ink ejection nozzles constituting the nozzle groups 2a to 2d,
It generates thermal energy to be added to the ink. The nozzle groups 2a to 2d are attached to the carriage so as to face the recording medium 1. Further, a drive signal for discharging ink is supplied to the recording head 2 via a flexible printer cable (FPC: not shown) having a large number of conducting wires.

Now, referring to FIG. 1 again,
To the nozzle groups 2a to 2d of the recording head 2, ink is supplied from a plurality of ink tank groups 4 that store a plurality of inks having different densities. Each compartment of the ink tank group 4 contains four types of black ink having different densities. Here, these inks are referred to as ink D1, ink D2, ink D3, and ink D4 in order from the lowest density.

When a transparent medium is used as the recording medium 1, for example, CF301 (trade name: Canon inkjet recording paper) is used. In this method, a polyethylene terephthalate (PET) film is used as a substrate, and a receiving layer containing coagulated boehmite is applied to the substrate as an image receiving layer by several tens of microns and dried. Although this recording medium is a transparency film (transparent medium), it can absorb a large amount of ink, and is preferably used because a high quality image can be obtained.

FIG. 3 shows ink D1, ink D2, and ink D.
FIG. 3 is a diagram showing the optical reflection density of ink D4. Here, the values shown are for the recording medium LC at an area ratio of 100%.
201 (trade name: Canon inkjet recording paper). The ink D
Reference numeral 4 denotes BJI-201Bk (trade name: Canon Ink Cartridge Black), and ink D3, ink D2, and ink D1 are prepared by diluting ink D4 with water.

FIG. 4 is a block diagram showing a configuration of a control circuit of the printing apparatus shown in FIG.

In FIG. 4, reference numeral 101 denotes an image input unit serving as an interface for inputting an image signal from a computer, a video device, or the like. 102 denotes various keys for instructing setting of various parameters and start of recording, a device state, and a message. An operation unit including an LED and an LCD, a CPU 103 for executing various control programs for controlling the entire printing apparatus, and a ROM 104 for storing a program executed by the CPU 103 for controlling the printing apparatus.

The ROM 104 stores a program for converting input data input from the image input unit 101 into multi-valued data and generating output image data to be output to a printer.

An image processing unit 105 multi-values input image data in accordance with a program stored in the ROM 104 to generate output image data. A work area and an error 106 for executing various programs stored in the ROM 104 are provided. A temporary save area at the time, a RAM used as a buffer for output image data, and a printer unit 107 for forming an image on a recording medium based on the output image data. Reference numeral 108 denotes a CPU bus that interconnects the components of the printing apparatus and transmits an address signal, data, a control signal, and the like for controlling the entire printing apparatus between the components.

Next, a description will be given of a process of printing a gradation image by multi-pass printing control in the printing apparatus having the above configuration. Here, a description will be given assuming that multi-pass printing is performed in which the print head scans the same area of the print medium four times to complete image printing in that area. In addition, in order to enhance the gradation expression ability, it is assumed that, in each pass printing, ink is discharged at the same pixel position up to twice.

FIG. 5 is a flowchart showing a gradation image recording process.

First, in step S1, the image input unit 1
01, image data is input. Here, the image input unit 1
In the input image data input from 01, one pixel represents 8 bits (0 to 255), the brightest part is “0”, and the darkest part (highest density) is “255”. It is also assumed that the resolution of the recorded image is 180 dpi.

Next, in step S2, the input image data is stored in the RAM 106.

In step S3, image data to be output to the recording head 2 is generated.

First, in each pixel of the input image data,
If the pixel value (P) is 255 ≦ P ≦ 240, the threshold value (TH1) is set to 248 and the binarization process is performed. And 2
The pixels obtained by the binarization processing are stored in the RAM 106 as image data N16.

Next, when the pixel value (P) is 239 ≦ P ≦ 2
If the number is 24, the threshold value (TH2) is set to 232 to perform the binarization processing. Then, the pixels obtained by the binarization processing are stored in the RAM 106 as image data N15.

Hereinafter, similarly, for each pixel of the input image data, a binarization process is performed using different thresholds (TH3, TH4,..., TH16) for every 16 gradations from pixel values of 223 to 0. Then, N1 is generated from the image data N14, and this is stored in the RAM 106.

The image data (N
., N1) with reference to the table shown in FIG. 6 to generate output image data (M1, M2, M3, M4) corresponding to four types of dark and light inks (D1, D2, D3, D4). I do. Here, the output image data (M1) is the ink D
1, the output image data (M2) is the number of ink discharges by the ink D2, the output image data (M3) is the number of ink discharges by the ink D3, and the output image data (M4) is the number of ink discharges by the ink D4. Is shown.

For example, when image data N6 is generated from input image data indicating a certain pixel, referring to the table shown in FIG. 6, M1 = 6, M2 = 2, M3 =
Output image data of 0 and M4 = 0 is generated.

Further, in step S4, the output image data (M1, M2, M3, M4) generated in step S3
, It is determined which type of ink is to be used in what pass and in what ink discharge, and a print signal indicating this determination is generated.

FIG. 7 shows image data (N16, N15,...)
, N1) is a table showing which kind of ink is used in what number of passes and in what number of ink discharges.

For example, the output image data (M1, M2, M
3, M4) is generated by the image data N6, the ink discharge with the ink D2 is performed twice in the first pass, and the ink discharge with the ink D1 is performed in the second to fourth passes.
Execute it twice.

Similarly, image data of other values (N16... N
7, N5... N1), it is determined with reference to the table shown in FIG. 7 what kind of ink is to be used in what pass and in what ink discharge.

Finally, in step S5, the recording signal thus generated is transmitted to the recording head 2 to perform recording. Here, the driving frequency related to ink ejection of the recording head 2 is set to 1000 Hz, and recording is performed on the above-described transparent recording medium CF301.

FIGS. 8 and 9 are diagrams schematically showing recording dots formed by two ink droplets at the same pixel position on the recording medium. FIG. 8 is a diagram in which the recording dots are viewed from the upper surface of the recording medium, and FIG. 9 is a diagram in which the same recording dots are viewed from the side surface of the recording medium. In FIG. 8, the drawn cells represent one pixel.

FIGS. 8A to 8C show that the first and second ink droplets are ejected to the same pixel position while the recording head is slowly moved (the driving frequency is small). This shows how dots are formed by two ink droplets. In this case, the first and second ejections occur while the recording head moves, so that the dot positions due to these ejections are slightly shifted, and the density of the overlapping portion of the two ink droplets increases. For example, when the driving frequency of the recording head is set to 15 Hz and the recorded image is observed, a recording streak occurs.

8D to 8E, when the recording head moves faster (the driving frequency is 1000 Hz),
A state in which a larger dot is formed by two ink droplets by ejecting the first and second ink droplets to the same pixel position is shown.

FIG. 9A shows dot formation corresponding to FIGS. 8A to 8C. In this case, since the recording frequency is low, dots are recorded by the first ink ejection,
After the ink is absorbed by the recording medium, dots are recorded by the second ink ejection. The dot diameter formed by these ink ejections is “b”.

FIG. 9B shows dot formation corresponding to FIGS. 8D to 8E. In this case, since the driving frequency is large, the dots formed by the second ink ejection are recorded before the ink of the dots formed by the first ink ejection is absorbed and fixed on the recording medium. Further, since the recording head moves at high speed, the dot diameter formed by these ink ejections is “a (> b)”. At this time, 1
The recording dots corresponding to the pixels are recorded so as to overlap at least half of the two dot diameters, and necessarily have a dot shape spread in the horizontal direction (scanning direction of the recording head). However, before the ink of the dot formed by the first ink ejection is absorbed and fixed on the recording medium, the dot formed by the second ink ejection is recorded, so the example shown in FIG. Although the dot size becomes larger as compared with, the non-uniform density is reduced in the dot formed by combining the two inks and combining the two ink droplets.

When a recording signal is generated with reference to the table shown in FIG. 7, since only the same type of ink is ejected in the same pass, density unevenness due to mixing of two dots can be reduced. Further, since different types of inks are used in different passes, one ink and another ink are used with sufficient time, that is, the ejected ink is sufficiently absorbed and fixed on the recording medium. Since another ink is ejected later, density unevenness caused by mixing different types of ink is reduced, and an intended gradation can be expressed.

Therefore, according to the embodiment described above, by appropriately combining the types of inks used in multi-pass printing with ink ejection to the same place in the same pass, it is possible to perform printing at high speed and achieve gradation Image recording with enhanced expression quality can be performed. From the image recorded in this way, streaks considered to be caused by minute variations in ink droplets to be ejected are reduced,
A high-quality recorded image can be obtained.

In the above-described embodiment,
Even when the driving frequency is set to 5000 Hz, it is possible to obtain the result that the recording streak is reduced and the image quality is improved.

Further, in accordance with the value of the image data, which kind of ink is used in what pass and in what ink discharge is not limited only by the table shown in FIG. For example, if the driving frequency of the recording head is 10
00Hz and a table as shown in FIG. 10 in the same manner as in the above-described embodiment, it is determined which kind of ink is to be used in what pass and in what ink discharge. May be recorded based on the information. Even with such printing, it has been confirmed that streaks, which are considered to be caused by minute variations in ejected ink droplets, are considerably reduced, and that the quality of a printed image is improved.

Further, in the embodiment described above, the transparent recording medium CF301 is used as the recording medium, but the present invention is not limited to this. For example,
As a recording medium, LC201 (trade name: Canon inkjet recording paper) may be used. Even when printing is performed by using this print medium at a print head driving frequency of 5000 Hz, stripes considered to be caused by minute variations in ejected ink droplets are reduced, and the quality of a printed image is improved. .

However, the same image data (M) is recorded on a transparent recording medium (for example, CF301) such as an OHP film and an opaque recording paper (for example, LC201).
1, M2, M3, and M4), for example, when recording is performed using the same table shown in FIG. 7, since the two recording media have different optical characteristics, the resulting recorded images also have different gradations. No.

In the above embodiments, a plurality of black inks having different densities have been described. However, the present invention is not limited to this. For example, a color ink using another color tone or colorant may be used. The present invention can be applied even if is used.

The gradation image recording in the embodiment described above is used for recording an image such as an X-ray image and an ultrasonic diagnostic image which are often used in the field of medical images.

The above-described embodiment is particularly provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for causing ink to be ejected even in an ink jet recording system. By using a method in which a change in the state of the ink is caused by energy, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, liquid (ink)
By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding the film boiling to the electrothermal transducer arranged corresponding to the sheet or the liquid path holding the Since thermal energy is generated in the electrothermal transducer and film boiling occurs on the heat-acting surface of the recording head, bubbles in the liquid (ink) corresponding to this drive signal on a one-to-one basis can be formed. It is valid. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of the liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angle liquid flow path) as disclosed in the above-mentioned respective specifications, A configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600, which discloses a configuration in which a heat acting surface is arranged in a bent region, is also included in the present invention. In addition, for multiple electrothermal transducers,
JP-A-59-123670 which discloses a configuration in which a common slot is used as a discharge part of an electrothermal transducer, and JP-A-59-123670 which discloses a configuration in which an opening for absorbing a pressure wave of thermal energy corresponds to a discharge part. A configuration based on 138461 may be adopted.

Further, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is determined by combining a plurality of recording heads as disclosed in the above-mentioned specification. This may be either a configuration satisfying the above requirements or a configuration as a single recording head formed integrally.

In addition to the cartridge-type recording head in which the ink tank is provided integrally with the recording head itself described in the above embodiment, the recording head is electrically connected to the apparatus main body by being mounted on the apparatus main body. A replaceable chip-type recording head, which enables a simple connection and supply of ink from the apparatus main body, may be used.

It is preferable to add recovery means for the printhead, preliminary auxiliary means, and the like to the configuration of the printing apparatus described above, since the printing operation can be further stabilized. Specific examples thereof include capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof. It is also effective to provide a preliminary ejection mode for performing ejection that is different from printing, in order to perform stable printing.

Further, the recording mode of the recording apparatus is not limited to a recording mode of only a mainstream color such as black, but may be a recording head integrally formed or a combination of a plurality of recording heads. Alternatively, the apparatus may be provided with at least one of full colors by color mixture.

In the above-described embodiment, the description has been made on the assumption that the ink is a liquid. However, even if the ink solidifies at room temperature or lower, it is possible to use an ink that softens or liquefies at room temperature. Or, in the ink jet method, it is common to control the temperature of the ink itself in a range of 30 ° C. or more and 70 ° C. or less so that the viscosity of the ink is in a stable ejection range.
It is sufficient that the ink is in a liquid state when the use recording signal is applied.

In addition, in order to positively prevent temperature rise due to thermal energy as energy for changing the state of the ink from the solid state to the liquid state,
Alternatively, in order to prevent evaporation of the ink, an ink which solidifies in a standing state and liquefies by heating may be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy recording signal and the liquid ink to be ejected, or by the time the ink reaches the recording medium, the solidification of the ink already begun. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, as described in JP-A-54-56847 or JP-A-60-71260, the ink is held in a liquid state or a solid state in the concave portion or through hole of the porous sheet. It is good also as a form which opposes an electrothermal transducer. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

[0095] In addition to the above, the recording apparatus according to the present invention may be provided not only as an image output terminal of an information processing apparatus such as a computer but also integrally or separately, a copying apparatus combined with a reader or the like, and a transmission / reception apparatus. It may take the form of a facsimile machine having functions.

The present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), and can be applied to a single device (for example, a copier, a facsimile). Device).

[0097]

As described above, according to the present invention, ink is supplied from a plurality of ink tanks each storing a plurality of types of inks having similar colors and different densities. In multi-pass printing in which image printing is completed by scanning the same area of the printing medium a plurality of times, multi-valued image data is input, and according to the density value of the input multi-valued image data, at substantially the same pixel position on the printing medium, It is determined which kind of ink is to be ejected and how many times out of the plurality of kinds of inks, and based on the result of the decision, one scan of the print head performs ink ejection at substantially the same pixel position on the print medium a plurality of times. Since the operation of the recording head is controlled as described above, there is an effect that a high-quality gradation image can be recorded.

[0098]

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a printing apparatus including a print head that performs printing according to an inkjet method, which is a typical embodiment of the present invention.

FIG. 2 is a diagram illustrating an ink ejection surface of a recording head 2.

FIG. 3 is a diagram illustrating optical reflection densities of ink D1, ink D2, ink D3, and ink D4.

FIG. 4 is a block diagram illustrating a configuration of a control circuit of the printing apparatus illustrated in FIG.

FIG. 5 is a flowchart illustrating a gradation image recording process.

FIG. 6 is a diagram showing a table for determining the number of times of ink ejection.

FIG. 7 is a table showing which type of ink is used in what number of passes and in what number of times of ink ejection in accordance with the value of image data.

FIG. 8 is a top view schematically showing recording dots formed by two ink droplets at the same pixel position on a recording medium.

FIG. 9 is a side view schematically showing recording dots formed by two ink droplets at the same pixel position on a recording medium.

FIG. 10 is another example of a table indicating which type of ink is used in what pass and in what ink discharge in accordance with the value of image data.

FIG. 11 is a diagram illustrating selection probabilities of two inks.

FIG. 12 is a diagram illustrating the number of ejections of a plurality of inks according to a gradation value.

[Explanation of symbols]

 2 Recording Head 3 Guide Shaft 4 Ink Cartridge Group 6 Drive Belt 7 Carriage Motor 8 Conveyance Roller 9 Discharge Roller 10 Blade 11 Cap 12 Ink Absorber 13 Recovery Unit 101 Image Input Unit 102 Operation Unit 103 CPU 104 ROM 105 Image Processing Unit 106 RAM 107 Printer unit 108 CPU bus

Claims (11)

[Claims] 1. A recording apparatus for completing image recording by scanning the same area of a recording medium a plurality of times with a recording head conforming to an ink-jet method, comprising a plurality of inks each storing a plurality of types of inks having similar colors and different densities. An ink tank, input means for inputting multi-valued image data, and according to the density value of the multi-valued image data input by the input means, at substantially the same pixel position on the recording medium, First determining means for determining which type of ink is to be ejected and how many times; and, based on a result determined by the first determining means, a plurality of times at substantially the same pixel position on the recording medium in one scan of the recording head. And a control unit for controlling the operation of the print head so as to perform the above-described ink discharge. 2. The apparatus according to claim 1, further comprising: a second determination unit that determines which type of ink is to be ejected in which scan in the plurality of scans based on a determination result of the first determination unit. The recording device according to claim 1, wherein: 3. The recording apparatus according to claim 1, wherein the recording head has a plurality of ink ejection nozzle groups for ejecting ink using each of the plurality of types of ink. 4. The control device according to claim 1, wherein
2. The recording apparatus according to claim 1, wherein the recording apparatus is driven at a driving frequency of 00 Hz or more. 5. The printing apparatus according to claim 1, wherein the control unit controls so as to eject ink of the same density in one scan of the print head. 6. The printing apparatus according to claim 1, wherein the control unit controls so as to discharge ink of the same density or ink of a different density in one scan of the print head. 7. The recording medium is a transparent medium, wherein a polyethylene terephthalate film is used as a base material of the medium, and a receiving layer containing alumina hydrate is provided as an image receiving layer on the base material. The recording device according to claim 1, wherein 8. The printing head according to claim 1, wherein the printing head uses thermal energy to eject ink, and includes a thermal energy converter for generating thermal energy to be applied to the ink. Item 2. The recording device according to Item 1. 9. The printing by scanning a plurality of times is performed by scanning the same area of a print medium four times with the print head, and printing the print head with respect to substantially the same pixel position in each scan. 2. The recording apparatus according to claim 1, wherein ink is ejected twice. 10. Ink is supplied from a plurality of ink tanks which respectively store a plurality of types of inks having similar colors and different densities, and the same area of a recording medium is scanned a plurality of times by a recording head according to an ink jet system to record an image. A recording control method for completing, comprising: an inputting step of inputting multi-valued image data; and a method of inputting the plurality of types of inks at substantially the same pixel position on the recording medium according to a density value of the input multi-valued image data. The first to determine which type of ink is to be ejected and how many times
Determining the operation of the recording head based on a result of the determination in the first determining step so that ink is ejected a plurality of times to substantially the same pixel position on the recording medium in one scan of the recording head. A recording control method comprising: 11. A method according to claim 1, further comprising a second determining step of determining which type of ink is to be ejected and in which scan in the plurality of scans based on the determination result in the first determining step. The recording control method according to claim 10, wherein: