JP2001171092A - Ink jet recorder and ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record an image having high image quality by preventing the image quality from lowering due to variation of density, uneven density or void. SOLUTION: Input data is converted into the density data of each pixel in a recording region (S1), an interested pixel is selected from the recording region (S202), a combination of the type of ink and the number of ink drops being used for recording the interested pixel is selected (S204) depending on the density data of the interested pixel, a density is predicted when the interested pixel is recorded on a recording medium according to the selected combination (S207), a combination of the type of ink and the number of ink drops being used is selected again if the difference between the predicted density and the density data is larger than a specified value (S209, S3), and recording is performed by generating a driving signal being transmitted to a recording head according to the combination of the type of ink and the number of ink drops selected finally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus and an ink jet recording method, and more particularly, to a method of using a plurality of ink jet recording heads for ejecting inks having different densities, for each pixel on a recording medium. TECHNICAL FIELD The present invention relates to an ink jet recording apparatus and an ink jet recording method for performing multi-tone printing by changing the type of ink ejected and the number of ink droplets.

[0002]

2. Description of the Related Art For example, as an information output device in a word processor, a personal computer, a facsimile, or the like, a recording device for recording desired information such as characters and images on a sheet-like recording medium such as a sheet or a film. The serial recording method of performing recording while reciprocally scanning in a direction perpendicular to the feeding direction of the recording medium is generally widely used from the viewpoint of low cost and easy downsizing.

As a recording method of such a recording apparatus, a state change accompanied by a steep volume change (generation of bubbles) is caused in the ink by applying energy such as heat to the ink, and an acting force based on the state change is generated. An ink jet recording method (so-called bubble jet recording method) is known in which an ink is ejected from an ejection port to fly and adhere to a recording medium to record an image.

In recent years, many recording apparatuses such as printers, copiers, and facsimile machines use the ink jet recording method, and high-speed recording, high resolution, high image quality, low noise, and the like are required. As an ink jet recording apparatus which meets these requirements, a recording head in which a plurality of ink ejection ports are integrated and arranged, and further, a plurality of the recording heads are used. Further, as a method for faithfully reproducing the gradation of image information, a halftone processing method such as a dither method or an error diffusion method is used.

[0005] In these halftone processing methods, 30 c
When observing the output image at a distance of about m, if the resolution is higher than about 900 to 1000 dpi (Dot Per Inch), the dot interval exceeds the eye resolution and the image is recognized as a smooth image. Rapid qualitative changes occur.

On the other hand, in a recording apparatus having a low resolution, such as 360 dpi, if a large number of gradations are to be obtained, dithering is difficult.
Matrix intervals become coarse and smooth images cannot be obtained. Conversely, if the dither matrix interval is made small in order to obtain smooth images, a sufficient number of gradations cannot be obtained. Further, in a recording apparatus having a sufficiently high resolution such as 1200 dpi, when the number of simulated dither matrices in a set of dither patterns increases, the visibility in low gradation and high gradation expression becomes low. Because of the loss, the gradation characteristics of the image are impaired.

Therefore, as a method of increasing the number of gradations without increasing the resolution, a method of multi-valued recording dots has been used. For example, in supplying energy to a recording head, a method is known in which the gradation is obtained by controlling the applied voltage and the pulse width in pulse driving to modulate the diameter of recording dots attached to a recording material. ing. In this method, it is difficult to reproduce many gradation values stably, for example, the environment dependence is high, the diameter of recording dots formed is unstable, and the minimum recordable dot size is limited. Although difficult, modulation of about several gradations is currently in practical use.

In the current ink jet recording apparatus,
Techniques for obtaining high-resolution images by improving gradation characteristics include:
A so-called multi-droplet system in which a plurality of droplets land on the same location on a recording material to form one recording dot (pixel), and the number of droplets to be landed is controlled to represent gradation. In addition, a recording method of expressing gradation by forming recording dots of at least two or more different densities of the same color using a plurality of inks having different densities, and a method of combining the two are proposed. It has been put to practical use.

On the other hand, as one means of pseudo tone reproduction by the error diffusion processing method, R. Floyd, L .; St
Einberg et al.'s paper "An Adaptive algorithm for
spatial greyscale ”(Step SI D75Dige
st, DP 36-37).

As an image recording method to which the above-mentioned error diffusion method is applied, for example, Katoh, Y. Arai, Y. Yasuda et al., “Multi-level error diffusion method” (National Conference of Communi).
cation, Department in Showa53 Year, Society of Elect
ronic Communication in Japan1973, pp504 (Japanes
In e)), an error diffusion method in which a plurality of threshold values are provided is realized in contrast to the conventional error diffusion method in which one fixed threshold value is provided. For example, if the range of image data is 0 to 255, error diffusion is conventionally performed using 128 as a threshold to obtain binary data, but Katoh, Y. Arai, Y. Yasuda
In the "multi-valued error diffusion method" of the authors, when grayscale printing is performed with two types of ink densities, 85 and 175 are set as threshold values to obtain ternary data with two types of recording densities. .

In recent years, attempts have been made to obtain multivalued data with three or more types of recording densities and express high-quality images.

As disclosed in US Pat. No. 4,723,129 and the like, a recording apparatus using an ink jet recording method includes a discharge port for discharging ink and an ink flow transmitted through the discharge port. An electro-thermal converter is generally provided as a path and an energy generating means for discharging ink into the ink flow path.

In an ink jet recording apparatus using the recording head, since the ink remains in the ink flow path of the recording head during non-operation and non-recording, deterioration such as an increase in viscosity due to drying and evaporation of the ink occurs. Measures have been taken to prevent

As means therefor, a so-called capping means for covering the ejection surface of the recording head with a lid to prevent drying and evaporation of ink, and, in addition to the capping means, for sucking air in the cap to form an ink flow path. Suction / pressurizing means for applying a negative pressure to the ink or applying pressure using a pump or the like to remove not only the degenerated interface but also foreign matter and bubbles from the ink flow path, or clean the ink discharge surface with a wiper. For example, a cleaning unit that removes the ink fixed matter near the ejection port is used.

[0015] Further, by ink ejection during the recording operation,
Ink is gradually wiped and cleaned at a predetermined timing in order to prevent the ink from gradually adhering to the ink ejection port surface and causing a change in the ejection direction and a defective ejection (non-ejection). Furthermore, in order to expel the deteriorated ink from the unused nozzles during the printing operation, a preliminary ejection for performing ejection different from the printing operation is performed at a predetermined timing, so that fresh ink always stays in the printing head, A method of performing stable recording is also performed.

[0016]

When the above-described recovery operation is performed, fresh ink is supplied into the ink flow path of the recording head. However, evaporation of the ink solvent is promoted by heating and remaining heat of the heater. Therefore, immediately after the recovery operation, the solvent forming the ink gradually evaporates from the discharge port, and a phenomenon occurs in which the ink concentration in the ink flow path relatively increases. as a result,
This causes a change in density and uneven density, and further causes sticking in the ink flow path, causing a change in the ink discharge direction and a non-discharge, thereby deteriorating the image quality.

In particular, in a multi-droplet system or a system in which gradation is expressed using a plurality of inks of similar colors and different densities, the linearity of the gradation reproduction characteristic is lost, the smoothness of the gradation is lost, and a pseudo contour (streak) is generated. In some cases, the image quality was impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an ink jet recording apparatus capable of recording a high quality and high quality image by suppressing image quality deterioration due to density change, density unevenness, white spots and the like. It is an object to provide a recording apparatus and an ink jet recording method.

[0019]

In order to achieve the above object, an ink jet recording apparatus according to the present invention uses a plurality of ink jet recording heads for discharging inks having different densities,
An ink jet recording apparatus that performs multi-tone recording by changing the type of ink and the number of ink droplets ejected to each pixel on a recording medium, and converts input data to the density of each pixel in a recording area A conversion unit for converting data into data, a selection unit for selecting a target pixel from the recording area, and a set of the type of ink and the number of ink droplets used when recording the target pixel according to the density data of the target pixel An ink distributing unit for selecting a combination; a density predicting unit for calculating a predicted density when the target pixel is recorded on a recording medium according to the combination; a difference between the predicted density and the density data being larger than a predetermined value In this case, the re-ink distributing means for selecting again the combination of the type of ink to be used and the number of ink drops, and the combination of the type of ink and the number of ink drops finally selected. I, and a driving means for generating drive signals to be transmitted to the recording head.

According to another aspect of the present invention, there is provided an ink-jet recording method using a plurality of ink-jet recording heads for ejecting inks having different densities, the type of ink ejected to each pixel on a recording medium and ink droplets. An ink-jet recording method for performing multi-tone recording by changing the number of pixels, wherein a conversion step of converting input data into density data of each pixel in a recording area, and selecting a target pixel from the recording area And an ink distributing step of selecting a combination of the type of ink and the number of ink droplets to be used when printing the target pixel according to the density data of the target pixel; and recording the target pixel according to the combination. A density prediction step of obtaining a predicted density when recorded on a medium; and a method of using when a difference between the predicted density and the density data is larger than a predetermined value. And a drive signal to be transmitted to the recording head in accordance with the finally selected combination of the type of ink and the number of ink droplets. And a driving step.

That is, when a plurality of ink jet recording heads for ejecting inks having different densities are used and multi-gradation recording is performed by changing the kind of ink ejected to each pixel on the recording medium and the number of ink droplets. The input data is converted into density data of each pixel in the printing area, a target pixel is selected from the printing area, and the type of ink used when printing the target pixel according to the density data of the target pixel. And a combination of the number of ink drops and a predicted density when the target pixel is recorded on the recording medium in accordance with the selected combination.If the difference between the predicted density and the density data is larger than a predetermined value, A drive for again selecting a combination of the type of ink and the number of ink droplets to be used, and transmitting the combination to the recording head in accordance with the finally selected combination of the type of ink and the number of ink droplets Performs recording the issue occurred.

In this way, the predicted density actually recorded on the recording medium is determined based on the combination of the selected type of ink and the number of ink drops, and the difference between the predicted density and the density data is determined by a predetermined value. If the value is larger than the value, the combination of the type of ink and the number of ink droplets can be selected again, and an image more faithful to the input data can be recorded.

Therefore, even when the ink density changes during the printing operation, high-quality and high-quality images can be printed while suppressing image quality deterioration due to density changes, density unevenness, white spots and the like.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the following embodiments, for simplicity of description, an ink jet recording apparatus that records a transmission image using an additive ink / film system will be described as an example.

First, the additivity and the density and ejection amount of the ink used in the following embodiments will be described.

<Additivity> When an ink-jet recording apparatus performs recording on a recording medium such as a film for recording a transmitted image, the ink / film system having an additivity is ejected a plurality of times onto the same spot. (Overlapping) means that the transmission density increases in accordance with the total ejection amount of the ink.

FIG. 3 is a graph showing the relationship between the ink discharge amount and the transmission density of the recording medium as an example of the case where the additivity is satisfied. Here, as a recording medium, BJ Trans @ Alliance Film CF-30 manufactured by Canon Inc.
1. Dye-based ink C.I. I. The relationship between the ink ejection amount and the transmission density when printing is performed by an inkjet printing apparatus using the solution of Direct Black 19 is shown.

In the figure, (A) shows a dye-based ink C.I. I. This shows a case where a 2% solution of Direct Black 19 is used. When recording is performed with an ink ejection amount of 40 [pl], the transmission density becomes 0.8D. Also, (B) in FIG. I. This shows a case where a 1% solution of Direct Black 19 is used. When recording is performed with an ink ejection amount of 40 [pl], the transmission density is 0.4D. When the two types of inks having different densities are superimposed and recorded on the same location on the recording medium, a transmission density of 1.2D can be obtained.

Further, it has been confirmed by experiments that when the above-mentioned two types of inks are used for recording on the above-mentioned film, additivity is substantially satisfied in the range of 0 to 2.5D.

As described above, the ink / additive /
When a film system is used, a plurality of inks having different densities are overprinted on the same location on a recording medium, thereby increasing the number of expressible gradations.

<Ink Density> Next, in the ink jet recording apparatus according to the present embodiment, up to four times overprinting is performed on the same location on the recording medium by using four types of inks having different densities that can be added. As will be described, the ink density used in such an ink jet recording apparatus will be described below.

In the above-described ink jet recording apparatus, the ratio of the four ink densities D0, D1, D2, and D3 is set to 1: 2: 4: 8, and overprinting is performed on the same location on the recording medium. By changing the combination of ink types, a maximum of 16 gradation numbers can be obtained.

FIG. 4 shows an example of an ink distribution table representing drive data of a recording head for ejecting each ink with respect to density data. This will be described below with reference to FIG.

D0 to d3 are signals (recording data) indicating the presence or absence of ink ejection for the inks D0 to D3 having different ink densities. When the signal is 1, the ink is ejected.
This is a binary signal that means non-ejection that does not eject when it is 0.

For example, if the image density value is 10, it indicates that the inks D1 and D3 are ejected so as to overlap the same location on the recording medium. Here, since the ink density ratio is set to 1: 2: 4: 8, density data from 0 to 15 can be expressed at equal intervals depending on the combination of the presence or absence of ejection of each ink.

That is, when there are n kinds of ink densities and the recording medium can absorb the total amount of ink by n times of overprinting, the density ratio of each ink is set to be an exponential multiple of 2 so that The maximum number of gradations of the nth power can be obtained.

<Ink Discharge Amount> As shown by the relationship between the ink discharge amount and the transmission density in FIG.
I. 40 [pl] of a 2% solution of Direct Black 19
The transmission density when ejected is 0.8 D, the ejection density is halved, and the ejection density when an ejection amount of 20 [pl] is ejected is 0.4 D, and the transmission density is also halved. Further, a dye-based ink C.I. I. Direct Black 19-1
% Solution when the solution is discharged at 40 pl.
4D, and when this discharge amount is halved (20 [p
l]) also has a transmission density of 0.2 D, indicating similar characteristics.
In such an ink / film system, experimentally
It has been confirmed that a proportional relationship is substantially established between the ink ejection amount and the transmission density in the range of 2.5D.

That is, since a proportional relationship is established between the ink ejection amount and the transmission density, the transmission density can be controlled by changing the ink ejection amount, and the number of gradations that can be expressed can be further increased. Becomes possible.

Therefore, in the present embodiment, a normal ink discharge amount (for example, 40 [p
l]), the ink discharge amount halved (for example, 20 [p
1]). Hereinafter, the normal ink ejection amount is referred to as large ejection, and the ink ejection amount halved is referred to as small ejection.

[First Embodiment] <Structure of Inkjet Recording Apparatus> FIG. 2 is a block diagram showing the structure of a first embodiment of an ink jet recording apparatus according to the present invention. This will be described below with reference to FIG.

Reference numeral 11 denotes an image input unit such as a scanner, 12 denotes an operation unit having various keys for setting various parameters and instructing start of recording, and 13 denotes various types of control programs 1501 provided in the ROM 15. It is a CPU that controls the inkjet recording apparatus according to a program. Reference numeral 14 denotes a RAM used as a work area for various programs, a register, a work area for image processing, and a page memory for storing various data necessary for image recording.

A control program group 15 stores various programs for controlling the ink jet recording apparatus.
Reference numeral 501, a temperature correction table 150 storing data for setting driving conditions according to the print head temperature, a gamma correction conversion table 1503 storing reference data for gamma conversion processing of image data, an ink density to be ejected from image density data The ROM is provided with an ink distribution table 1504 storing reference data at the time of the ink distribution processing for selecting the ink distribution processing, and an ink density raising table 1505 storing data indicating the degree of increase in the ink density due to continuous non-ejection of the print head. .

The reference numeral 15 is not limited to a ROM, but may be any other recording medium such as a floppy disk, hard disk, magneto-optical disk, CD-ROM, CD-R, DVD, magnetic tape, or non-volatile memory card. Can be adopted. Reference numeral 16 denotes an engine of an ink jet recording apparatus for recording an image on a recording medium.

<Engine Unit> FIG. 5 is an external view showing a schematic configuration of the engine unit 16 of the ink jet recording apparatus of the present embodiment. The engine unit 16 includes, for each of four types of inks D0 to D3 having different ink densities, four cartridges 2000 to 2000 each including a recording head for discharging ink and an ink tank for storing ink to be supplied to the recording head. 2003. The flexible cables 2010 to 2013 drawn from the cartridges 2000 to 2003 are bundled together via a carriage 1802 for transporting the cartridges,
It is connected to a circuit board (not shown) by a flexible cable 1801.

After the recording medium P is conveyed to conveyance rollers 1811 via a paper feeding means (not shown), the driving belt 181
0, the sheet is conveyed in the direction of the arrow by the drive of the conveyance motor 1809.

The carriage 1802 is mounted on the guide shaft 1
805, and reciprocates by driving a carriage motor 1806 via a drive belt 1808. The control of the transport speed at that time is performed by feedback control in which the linear encoder 1804 is read by the detection element 1803.

When the ink jet recording apparatus does not perform image recording, the cap 190 is located at the home position where the carriage 1802 is located, at a position facing the recording head.
A capping unit 19 having 0 to 1903 is provided. When the carriage 1802 is located at the home position, the capping unit 19 is raised by lifting means (not shown), and the caps 1900 to 1903 seal the discharge port surfaces of the respective recording heads, thereby fixing ink and dust due to evaporation of the ink. To prevent clogging due to adhesion of foreign matter. Further, a pump (not shown) is operated in the capped state, and ink is sucked from the ink ejection port, thereby eliminating and preventing ejection failure.

An ink receiver 17 for receiving ink droplets ejected from the recording head is provided in an area where the image is not recorded on the recording medium within an operation range where the carriage 1802 reciprocates. Then, when each recording head passes over the ink receiver 17, ink is ejected (preliminary ejection) to refill the ink in the nozzles that have been in a non-ejection state during the recording operation, thereby maintaining high-quality recording. I'm trying to drip.

Further, by disposing a wiping member (blade) for wiping the discharge port surface of the recording head at a position adjacent to the capping unit 19, it is possible to clean the ink discharge port surface. .

<Recording Head> FIG. 6 is a diagram showing the configuration of a recording head used in the ink jet recording apparatus of this embodiment. (A) is a longitudinal sectional view along the ink flow path, (b) is a view seen from the nozzle surface, and (c) is a transverse sectional view in the nozzle arrangement direction. This will be described below with reference to FIG.

The recording head is based on a support 1 mainly made of aluminum, and an element substrate 2 formed by a semiconductor process and a printed board 3 on which electric components are mounted are fixed on the support 1 with an adhesive. It is formed.

The element substrate 2 has a heating resistor 200 as an ejection energy generating element for ejecting ink.
(Electrothermal converter) is formed, covered with a protective film 210 such as silicon oxide or silicon nitride, and has a structure that does not directly contact ink.

At the time of the recording operation, the ink is supplied from the ink tank 6 to an ink flow path composed of an ink inflow section 701, an ink supply path 702, a common liquid chamber 703, and a plurality of nozzles composed of a pressure chamber 704 and an ink fine path 705. And is ejected as a flying droplet 8 from an ejection port 706 of each nozzle.

FIG. 7 is an enlarged view of a portion corresponding to the [i] -th nozzle in FIG. 6C. As shown, the heating resistance element 200 is provided in each nozzle, and includes two heating resistance elements 201 and 202 having different heating values. Here, the discharge amount based on the discharge energy (heat generation amount) of each of the heating resistance elements 201 and 202 is 201: 202 = 1:
It is theoretically possible to realize a quaternary discharge amount, that is, a density by driving the heating resistance elements 201 and 202 in combination by setting it to 2.

In this embodiment, the gradation expression is represented by three values, and when both of the heating resistance elements 201 and 202 are driven, large ejection is performed. When only the heating resistance element 202 is driven, small ejection is performed. The case where both 201 and 202 are not driven (the ink droplets are not ejected) is referred to as non-ejection, and is designed so that the ratio of the ink ejection amount between the large ejection and the small ejection is 2: 1. In addition, it is assumed that the drive control of only the heating resistance element 201 is not performed.

The terminals 301 provided on the printed circuit board 3 are for wiring the recording head and a control board (not shown) with a flexible cable or the like. The printed board 3 and the element board 2 are wired by wire bonding 4.

<Driving of Head> Heating resistance elements 201,
As the means for supplying energy to 02, pulse driving using a plurality of pulse signals is performed. FIG. 8 is a graph showing waveforms of a recording timing signal and a drive signal used in the present embodiment.

In the drive timing generation circuit described later, (a)
A recording timing signal shown in (b) is generated, and two pulse waveforms of a preheat pulse P1 applied at the start of the recording timing signal shown in (b) and a main heat pulse shown in (c) are The driving is performed using this.

The preheat pulse P1 is for controlling the temperature of the ink in the ink flow path without causing ink ejection, and is supplied to all nozzles including non-ejection nozzles that do not eject ink. You. On the other hand, the main heat pulse P2 causes bubbling in the pressure chamber to discharge ink from the discharge port, and is supplied only to the nozzle that discharges the ink. Therefore, the signal shown in (d) is applied to the heating resistance element of the nozzle that does not eject ink,
The signal shown in (e) is applied to the heating resistance element of the nozzle that ejects ink.

The driving voltage Vop is electric energy necessary for generating heat energy in the heating element, and includes an area, a resistance value, a film structure, a discharge port of the recording head, and the like of the heating element.
It is determined according to the ink liquid path structure, ink physical properties, and the like.

T1 and T2 are the driving pulses P, respectively.
T12 is an interval time provided for preventing mutual interference between the preheat pulse P1 and the main heat pulse P2 and for equalizing the temperature distribution in the ink flow path. is there. T21 is a refill time required for refilling the ink after the ink is ejected, and can be neglected because the ejection frequency (1 / Tdrv) of the recording head is usually sufficiently larger than the refill time. These times depend on the area of the heating element,
The desired discharge amount V is determined widely based on the resistance value, the film structure, the discharge port of the recording head, the ink liquid path structure, the ink physical properties, and the like.
When d is determined, T1, T12, T2, and T21 are arbitrarily determined as appropriate.

<Temperature Correction of Discharge Amount> FIG. 9 is a graph showing the relationship between the printhead temperature and the ink discharge amount. With reference to FIG. 9, the relationship between the amount of ink discharged by the above-described driving and the temperature will be described.

Drive voltage Vop, preheat pulse width T
1, when the interval time T12 and the main heat pulse width T2 are constant, the ink droplet ejection amount Vd is
It is proportional to the recording head temperature Th. If a coefficient representing this proportional characteristic is defined as a temperature-dependent coefficient KT, it can be expressed as KT = ΔVdT / ΔTh.

When the recording head is driven, the recording head temperature Th, the driving voltage Vop, the preheat pulse width T1, the main heat pulse width T2 are kept constant, and the interval time T12 is changed. V
d changes. FIG. 10 is a graph showing the relationship between the discharge amount Vd and the interval time.

As shown in FIG. 10, when the interval time T12 increases, the temperature of the nozzle that has been heated by the preheat pulse P1 decreases, and the discharge amount Vd decreases. If the coefficient representing the interval time dependence characteristic is defined as Kp1, it can be expressed as: Kp1 = − (ΔVdp / ΔT12).

Therefore, based on the characteristic that the ink discharge amount depends on the temperature and the interval time, the interval time can be changed according to the temperature of the recording head without changing the waveforms of the preheat pulse P1 and the main heat pulse P2. By adjusting the length of T12, the ink ejection amount can be made constant.

FIG. 11 is a graph showing the relationship between the printhead temperature and the variable interval time t12 in the present embodiment. As shown in the figure, when the print head temperature is higher than the interval time t12 at the reference standard temperature shown in FIG. As shown in (b), the interval time t12 is lengthened, and when the temperature of the recording head is low, the interval time is shortened as shown in (d).

As described above, in the present embodiment, a predetermined energy for raising the ink temperature is given by the preheat pulse P1, a desired ink temperature distribution is formed by the variable interval time t12, and the main heat pulse P2 As a result, a desired ink ejection amount is obtained.

<Image Processing Unit> FIG. 12 is a flowchart showing the procedure of image processing in this embodiment. Hereinafter, the image processing and related control will be described with reference to FIG.

First, image data input processing (step S
Perform 1). FIG. 13 is a flowchart showing the image data input processing. This will be described below with reference to FIG.

An image signal (referred to as CV) is input from the image input unit (step S101), and the input image signal CV is input.
Is converted into image data (referred to as CD) representing the density using the gamma correction conversion table 1503 (step S10).
2) The image density data CD is stored in the page memory area for storing images secured on the RAM 14 (step S).
103). This image data input processing (step S101)
Steps S104 to S104) are repeated until all data is input from the image input unit.

After the above image data input processing is completed,
The non-ejection dot count registers UCR0 to UCR3 secured in the register area of the RAM 14 are initialized (step S201). The initial values are unidirectional recording,
It is arbitrarily determined as appropriate depending on various recording control modes such as bidirectional recording and the device configuration.

One pixel is selected as a pixel of interest from the image density data CD in the page memory area stored in the RAM 14 (step S202), and the image density data CD is read (step S203).

The image density data CD of the read target pixel
Based on the value, referring to the ink distribution table 1504,
A combination of printheads (inks) at the time of large ejection drive is selected, and a distribution table of print data d0 to d3 is generated (step S204).

FIG. 14 is a diagram showing an example of the distribution table generated at this time. FIG. 14 shows an example in which the density data is replaced with an 8-bit image density signal level based on FIG.
An ink distribution table representing a ternary drive pattern of large ejection (2) / small ejection (1) / non-ejection (0) of D1, D2, and D3, and transmission density at the time of overprinting by ink combination of the distribution table Is shown.

As for the image density signal level in FIG. 14, the smaller the value, the lower the density, and the larger the value, the higher the density. For the sake of simplicity, the transmission density of the transparent film as the recording medium is assumed to be 0D, and the transmission density of each of the inks D0, D1, D2, and D3 is the transmission density when only the single ink is 100% solid printed. It is. The density ratio of each ink is adjusted so as to be 1: 2: 4: 8 so as to obtain the maximum number of gradations, and the 8-bit signal level is set in the range of 0D to 2.4D in the 16th floor. It is a tone expression.

Further, in the current digital processing, each bit is represented by a binary value of 0 and 1, so that the ternary drive pattern cannot be represented by one signal. Accordingly, heater control signals B / S0 to B / S3 representing large ejection / small ejection together with print data d0 to d3 relating to ejection / non-ejection of each ink.
, Large ejection is represented by 1 and small ejection is represented by 0.

This ink distribution processing (step S204)
In order to generate ink distribution data in the large ejection drive, the heater control signals B / S0 to B / S0
S3 is set to 1.

After the ink distribution processing is completed, the ink density prediction processing is performed. Before that, the principle of the ink density prediction means will be described below.

FIG. 15 is a graph showing an example of the ink density increasing characteristics with respect to the ink non-ejection continuation time. FIG.
The characteristic of No. 5 is obtained by linear approximation using the least squares method based on the experimental results. The horizontal axis indicates the non-discharge duration of ink, and the vertical axis indicates the rate of increase of the transmission density (OD) of the ink. Here, the ink non-ejection continuation time means the elapsed time from when an ink droplet is ejected from the ejection opening of the recording head to when the next ink droplet is ejected.

For example, assuming that an image is recorded at an ejection frequency of 10 KHz and a resolution of 600 dpi, the scanning speed of the recording head is about 423.3 mm / s and about 0.7. The short side of the A3 paper is scanned in seconds. When the characteristics shown in FIG. 15 are added to this, the ink density increases while scanning the short side (297 mm) of the A3 paper, and the rate of increase is 170% at maximum from the ink non-ejection continuation time (0.7 seconds). Will occur.

The above-described increase in the ink concentration with respect to the ink non-ejection continuation time is a phenomenon that occurs when the ink concentration in the nozzles relatively increases due to the evaporation of the ink solvent from the ejection openings. Therefore, when the ejection operation is performed, the ink having the increased density is discharged, and the nozzle is refilled with new ink, so that the ink density returns to the specified density again.

Accordingly, it is possible to predict the ink density increase value based on the above-described ink non-ejection continuation time.

FIG. 16 is a graph in which the non-ejection duration, the ejection frequency (1 / Tdrv), and the non-ejection dot duration obtained from the printing resolution are used as parameters instead of the ink non-ejection duration. FIG. 16 shows the density increase rate with respect to the number of continuous non-ejection dots, from which the ink density of the print data d0 to d3 can be predicted.

FIG. 17 shows an ink density increase table 1505 with respect to the number of non-ejection dots of print data d0 to d3.
And the ink density prediction process will be described below.

First, the values of the non-ejection dot count registers UCR0 to UCR3 are read (step S20).
5).

At this time, a table as shown in FIG. 17 is stored in the ink density increase table area 1505 of the ROM 15, and the number of continuous non-ejection dots (= non-ejection dot) is stored in the offset address of the memory space.・
And the data at the address records a previously calculated density increase rate. Therefore, each non-ejection dot count register UCR0
The offset address of the ink density increase table area is generated from the value of UCR3, and the read cycle is executed, whereby the ink density increase rates Kd0 to Kd3 are obtained (step S206).

For example, if the density rise rate of the ink density rise table is 4-byte data and long word access is to be made to the ink density rise table area, the non-ejection dot count register values UCR0 to UCR0
A value obtained by quadrupling CR2 (shifted by 2 bits) is set as an offset address in the ink density increase table area, and a read cycle is executed. As a result, the obtained read data is the ink density increase rate Kd0 to Kd3.

Then, the obtained ink density increase rate Kd0
To Kd3, the basic density of each ink, and print data d0 to d3
By performing the above calculation, the predicted ink density value Z of the target pixel can be obtained (step S207).

Next, a predicted density error ΔZ between the calculated predicted ink density value Z and the image density data CD of the target pixel is obtained by the following formula (step S208).

ΔZ = (Z−CD) Here, the obtained predicted density error ΔZ is within a desired allowable range η.
If so, the process proceeds from step S209 to step S210, where the recording data d0 to d3 and the heat control signal B / S
0 to B / S3 are stored in the page memory area (target pixel address) of the RAM 14. On the other hand, the predicted density error ΔZ
Exceeds the desired allowable range η, step S20
Then, the process proceeds from step S3 to step S3 to execute a re-ink distribution process described later. The resulting print data d0 to d3 and the heat control signals B / S0 to B / S3 are stored in a page memory area (target pixel address) of the RAM 14. Store in

FIG. 18 is a flowchart showing the ink re-distribution process performed in step S3. Hereinafter, the re-ink distribution processing routine will be described.

First, the number h of print heads for performing a large ejection drive is obtained based on the print data d0 to d3 and the heater control signals B / S0 to B / S3 (step S30).
1).

The number h of print heads for performing the large ejection drive
Accordingly, (2 ^h −1) registers are prepared, and the redistribution of the re-heater control signals B / Sr0 to B / Sr3 in the (2 ^h −1) patterns in which the large ejection drive is changed to the small ejection drive A redistribution data generation process for generating data is performed (step S302). Also, the re-recorded data dr0-d
r3 is the same as the recording data d0 to d3.

One of the generated (2 ^h -1) reheater control signals B / Sr0 to B / Sr3 is selected and read (step S303).

Since the ink ejection amount in the case of the small ejection drive is set to be half that of the large ejection drive, that is, the density is halved, the ink density increase rates Kd0 to Kd3,
By calculating the basic density of each ink and the print data d0 to d3 and the reheater control signals B / Sr0 to B / Sr1, a re-predicted density value Zr of the target pixel can be obtained (step S304).

Next, a re-predicted density error ΔZr between the re-predicted density value Zr and the image density data CD is calculated by the following formula (step S305).

.DELTA.Zr = (Zr-CD) If the re-predicted density error .DELTA.Zr is zero, that is, equal to the image density data CD, the flow advances from step S306 to step S321 to perform a data replacement routine for replacing data in the register (step S321). And terminate the re-ink distribution process.

If the re-predicted density error ΔZr is not zero (not equal to the image density data CD), the process proceeds from step S306 to step S307, where the predicted density error ΔZr
An absolute value comparison between Z and the re-predicted density error ΔZr is performed. Here, the smaller of the two is closer to the image density data CD. Therefore, if the re-predicted density error ΔZr is smaller than the predicted density error ΔZ, the process advances from step S307 to step S308 to execute a data replacement routine for replacing the data in the register (step S308). If ΔZ or more, the process proceeds from step S307 to step S309, and shifts to the next process.

The above processing (the processing from step S309 to step S303) is repeated until all the data generated in the redistribution data generation processing (step S302) is processed, and the processing of all the generated redistribution data ends. If so, the process proceeds to step S3 to shift to the next process.
From 09, the process proceeds to step S310.

If the predicted density error ΔZ stored in the register at this time is a negative value, the recording density can be made closer to the image density data by discharging the non-discharged recording head. there is a possibility. Therefore,
If the predicted density error ΔZ is positive, the ink re-distribution process ends. If the predicted density error ΔZ is negative, the process proceeds from step S310 to step S311. In step S311, a print head that can be changed to ink ejection is checked. In this case, the number hr of non-ejection recording heads is obtained.

Here, it is determined whether or not the number hr of non-ejection recording heads is zero (step S312). If it is zero, the following processing is unnecessary and the re-ink distribution processing ends. If the number hr of non-ejection recording heads is not zero, the process proceeds to step S313.

In step S313, (3 ^hr -1) registers are prepared based on the number hr of recording heads for which non-ejection is performed, and non-ejection driving is changed to small ejection driving and large ejection driving (3 ^hr). -1) Reprint data dr0 to dr3, which are patterns, reheater control signals B / Sr0 to B / S
A redistribution data generation process for generating redistribution data of r3 is performed.

One of the generated (3 ^hr -1) patterns is selected and read (step S314).

Then, the ink density increase rates Kd0 to Kd
3. Basic density of each ink, reprint data dr0-dr
3. By performing the calculation of the re-heater control signals B / Sr0 to B / Sr3, the re-predicted density value Zr of the target pixel can be obtained (step S315).

Next, a re-predicted density error ΔZr between the re-predicted density value Zr and the image density data CD is calculated by the following formula (step S316).

ΔZr = (Zr−CD) Here, it is determined whether or not the re-predicted density error ΔZr is zero, that is, equal to the image density data CD (step S3).
17). If ΔZr is zero, the flow advances to step S321 to execute a data replacement routine for replacing data in the register, and ends the re-ink distribution processing.

When the re-predicted density error ΔZr is not zero, that is, when the re-predicted density error ΔZr is not equal to the image density data CD, the flow advances to step S318 to compare the absolute values of the predicted density error ΔZ and the re-predicted density error ΔZr. Here,
A smaller one is closer to the image density data CD.
Therefore, if the re-predicted density error ΔZr is smaller than the predicted density error ΔZ, the flow advances to step S319 to execute a data replacement routine for replacing the data in the register. If the re-predicted density error ΔZr is equal to or larger than the predicted density error ΔZ, the process proceeds to step S319.
Move to 320.

In step S320, the processing from step S314 to step S320 is repeated until all the data generated in the redistributed data generation processing (step S313) is processed, and the processing for all the generated redistributed data ends. If so, the ink re-distribution process ends.

The above-described ink re-distribution processing (step S
After executing 3), the obtained recording data d0 to d3 and the heat control signals B / S0 to B / S3 are stored in the page memory area (target pixel address) of the RAM 14 (step S210).

Then, an update process is performed in which the value of the non-ejection dot count register is counted up in the case of non-ejection driving and reset in the case of ejection driving (step S211).

After the ink distribution data is determined, an error diffusion process (step S4) is performed to further improve the gradation characteristics of the image.

Here, the error diffusion processing will be described below with reference to an example of an error diffusion matrix and weighting of the error diffusion processing shown in FIG.

In FIG. 19, it is assumed that the main scanning direction in which the recording head scans is X, the sub-scanning direction is Y, and the coordinates of the pixels are (X, Y). The asterisk in the figure indicates the target pixel currently set in the image processing routine, and the coordinates of the target peripheral pixel described below are expressed by relative coordinates with the target pixel.

As a pixel matrix, a target peripheral pixel with respect to a target pixel is represented by pixel coordinates (1, 0); (1, 1);
(0, 1); (-1, 1) are set, and the error distribution coefficient G for each peripheral pixel of interest is 4/8, 0/8, 3 /
8, 1/8 is set. Here, since the error distribution coefficient of the peripheral pixel of interest (1, 1) is 0/8, it can be omitted in a control flow described later to improve the processing speed.

FIG. 20 shows a control flowchart of the error diffusion process. The error diffusion process will be described below with reference to this flowchart.

First, the predicted density error ΔZ for the pixel of interest during image processing is read (step S401). The predicted density error ΔZ is obtained by subtracting the predicted ink density Z of the target pixel formed on the recording medium and the image density data CD, and indicates a difference error in the target pixel. Then, based on the difference error, an error distribution process to the peripheral pixel of interest is performed.

Here, it is determined whether or not the predicted density error ΔZ is zero (step S 402). If it is zero, the processing described later becomes meaningless, and the error diffusion processing ends. If the predicted density error ΔZ is not zero, the flow shifts to step S403.

In step S403, one of the peripheral pixels of interest is selected from the image density data CD in the page memory area stored in the RAM 14 and read.

Next, the error distribution coefficient G of the selected peripheral pixel of interest is read (step S404).

Then, from the predicted density error ΔZ, the image density data CD of the peripheral pixel of interest and the error distribution coefficient G, an error distribution calculation process is performed by the following formula, (CD + ΔZ × G), and new image density data CD is obtained. (Step S405).

The image density data of the peripheral pixel of interest obtained by the above error distribution calculation processing is stored in the page memory area of the RAM 14 (step S406).

The above-described error distribution processing (step S403)
To S406) are determined for all the peripheral pixels of interest (step S407). If there is a pixel that has not been performed, the process returns to step S403, and the process returns to step S403. If so, the error diffusion process ends.

With the above processing, the ink distribution data is determined for the target pixel, and the error distribution to the target peripheral pixel is completed. Then, the pixel of interest set next to the above process is set as a pixel adjacent in the main scanning direction, and the above process (step S
202 to S212) are repeatedly executed.

When the image processing for the pixel data for one scan is completed, the value of the non-ejection dot count register is initialized, and the above processing (step S201) is performed until all the image data are completely processed. ~ S21
Repeat 3). Then, processing for all the image data is executed, and the image processing ends.

<Image Recording> After the completion of the image processing, the ink jet recording apparatus performs an image recording process of recording an image on a recording medium based on the generated image data (ink distribution data).

FIG. 1 is a block diagram showing a portion related to the recording head 10 of the ink jet recording apparatus according to the present embodiment, and FIG. 21 is a control flowchart of an image recording process according to the present embodiment. Hereinafter, description will be made with reference to these drawings.

In FIG. 1, each ink D0, D1, D
Since the configuration of the recording heads provided for D2 and D3 is almost the same, only the configuration relating to one recording head 10 is described for simplification, and the other recording heads are omitted.

The CPU 13 print data d0 to d3 generated by the image processing and heater control signals B / S0 to B /
S3 is transferred to the image data transfer circuit 1602 (step S501), and is repeated until data for one scan is transferred (step S502).

Then, the recording head temperature Th detected by the temperature sensor 9 provided in the recording head 10
Are converted from analog to digital by the A / D converter 1603 and transmitted to the drive timing generation circuit 1606. The CPU 13 reads the print head temperature Th via the drive timing generation circuit 1606 (step S503).

From the recording head temperature Th, the ROM 1
5, using the temperature correction table 1502 provided for the recording head,
The time T12 is obtained, and the drive timing generation circuit 1606
(Step S504).

The ink jet recording apparatus in which the recording operation has been performed performs the recording operation (step S6).

The printing operation is repeated until printing for one scan is performed (steps S6 and S505), and the above-described processes S501 to S506 are performed until the printing operation for the entire image area is completed.
Is repeated to form an image on the recording medium.

FIG. 22 shows a timing chart of signal waveforms at various parts in FIG. This will be described below with reference to FIG.

When the CPU 13 transfers the print data dn and the heat control signal B / Sn for one scan from the page memory area of the RAM 14, the image data transfer circuit 1
602 receives a start instruction signal (not shown) transmitted from the drive timing generation circuit 1606. The image data transfer circuit 1602 that has received the start instruction signal transfers the print data dn and the heater control signal B / Sn synchronized with the transfer clock SDCLK to the shift registers 301 and 302.

Now, the number of nozzle rows of the recording head is set to (m +
1), the shift registers 301 and 302 are (m +
A 1-bit shift register is configured, and the image data transfer circuit 1602 transfers (m + 1) -bit data.

The drive timing generation circuit 1606 has an internal counter, and the image data transfer circuit 1602
After the transfer of (m + 1) -bit data from the shift registers 301 and 302 to the latch circuits 311 and 312
And outputs the latch signal LAT.

The latch circuits 311 and 312 that have received the latch signal LAT latch the data subjected to serial-parallel conversion by the shift registers 301 and 302. In FIG. 22, the recording data dn latched at this time is
And the heater control signal B / Sn picks up the i-th nozzle from the plurality of nozzles of the print head and outputs dn [i],
B / Sn [i].

The drive timing generation circuit 1606 that has output the latch signal LAT8b) outputs a preheat start signal to the preheat pulse generation circuit 1604 in accordance with a print timing signal that is an internal signal that specifies the print head ejection timing. Upon receiving the preheat start signal, the preheat pulse generation circuit 1604 outputs a preheat pulse signal P1 having a preset pulse width T1.

The drive timing generation circuit 1606 that has output the preheat start signal uses the internal counter to count a predetermined count of T1 and a count of T12 of an interval time T12 set based on the recording head temperature. Outputs the main heat start signal. Upon receiving the main heat output signal, the main heat pulse generation circuit 1605 outputs a main heat pulse signal P2 having a predetermined pulse width T2.

The recording data dn [i], heater control signal B / Sn [i], preheat pulse signal P1,
The main heat pulse signal P2 is supplied to the gate circuit 321.
Enter in [i].

The gate circuit 321 forms a logic circuit for these input signals, and is connected to a driving element (a transistor in the figure) for driving the heating resistance elements 201 and 202 of the recording head. .

The logic of the gate circuit 321 is to output the preheat pulse signal P1 to each of the transistors that drive the heating resistance elements 201 and 202. The print data dn [i] = 1 and the heater control signal B /
When Sn [i] = 1, the main heat pulse signal P2 is output to each of the transistors that drive the heating resistance elements 201 and 202. Print data d indicating small ejection drive
When n [i] = 1 and the heater control signal B / Sn [i] = 0, the main heat pulse P2 is output only to the transistor that drives the heating resistance element 202, and the heating resistance element 201 is driven. No output to transistor. When print data dn [i] = 0 indicating non-ejection drive,
The logic is such that the main heat pulse P2 is not output to any of the transistors.

Among the three recording timings shown in FIG. 22, the data latched at the first timing is as follows.
Print data dn [i] = 1, heater control signal B / Sn
Since [i] = 0 (small ejection driving), after the energy consumption based on the preheat pulse P1, the energy consumption based on the main heat pulse signal P2 is only the heating resistance element 202 [i].

The data latched at the second timing is as follows: print data dn [i] = 1, heater control signal B / S
n [i] = 1 (large ejection drive), and after the energy consumption based on the preheat pulse P1, the main heat
Energy consumption based on the pulse signal P2 is consumed by both the heating resistance elements 201 [i] and 202 [i].

Further, the data latched at the third timing is the recording data dn [i] = 0, the heater control signal B
/ Sn [i] = 1 (non-ejection drive),
After the energy consumption based on the pulse P1, no energy consumption based on the main heat pulse signal P2 occurs.

As described above, according to the present embodiment,
Density change and density unevenness are suppressed, and the linearity of gradation reproduction characteristics can be maintained.

The present invention can also be realized by mounting the above-described image processing means on a system or apparatus different from the above-described configuration and performing the same image recording processing as described above based on the supplied image data. Can achieve the purpose.

[Modification] FIG. 23 is a block diagram showing a configuration of a portion related to a recording head according to a modification of the first embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals. The description is omitted. Hereinafter, the difference will be described with reference to FIG.

The printhead temperature Th detected by the temperature sensor provided in the printhead 10 is input to the interval time control circuit 1607. The interval time control circuit 1607 converts the A / D converter and the temperature correction table provided in the ROM 15 in the first embodiment into a look-up table (LUT).
It is provided as.

The recording head temperature Th is converted from analog to digital by an A / D converter, and is used for temperature correction L.
Input to UT. The temperature correction LUT has an interval time T1 with respect to the print head temperature calculated in advance.
2 is stored, and outputs an interval time signal corresponding to the input printhead temperature.

Therefore, in the first embodiment, it is possible to sequentially perform the temperature correction processing performed for each scan, and the processing efficiency is further improved.

[Second Embodiment] In the first embodiment, the ink ejection amount control using the interval time T12 is shown as the temperature correction means. In the present embodiment, the ink ejection amount is controlled using the preheat pulse T1. This is to control the amount. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

<Temperature Correction of Ejection Amount> As the driving conditions of the recording head, the recording head temperature Th (= 25 ° C.), the driving voltage Vop, the interval time T12, the main heat pulse width T2 are fixed, and the preheating is performed. .Pulse width T1
Is changed, the ink ejection amount Vd changes. FIG.
Is a graph showing the relationship between the ejection amount Vd and the preheat pulse width.

As shown in FIG. 24, while the preheat pulse width t1 is between 0 and T1 [max], the discharge amount V
A linear characteristic in which d is proportional to the preheat pulse width t1 is obtained. The preheat pulse width t1 is T1
During the period from [max] to T1 [lmt], the ejection amount Vd also increases, but the proportional relationship does not hold, and the preheat pulse width T1
The maximum ejection amount Vd [lmt] is obtained at [lmt]. Further, when the preheat pulse width t1 is equal to or greater than T1 [lmt], the ejection amount decreases.

This is because the energy applied by the drive voltage Vop and the preheat pulse width t1 is
When the pulse width t1 is equal to or greater than the value of T1 [lmt], minute bubbling (a state immediately before film boiling) occurs on the surface of the heating resistor element, and minute bubbles adhere. After that, the main heat pulse P2 is applied before the microbubbles disappear, so that the microbubbles disturb the bubbles generated by the main heat pulse P2, and as a result, the ejection amount becomes small, which is a so-called pre-bubble phenomenon. Things. This region is called a pre-foaming region, and it is difficult to control the discharge amount in this region.

Therefore, in the range of 0 to T1 [max] in which the discharge amount Vd with respect to the preheat pulse width t1 shows a proportional characteristic, the discharge amount can be easily controlled by changing the preheat pulse width t1. It is possible.

Here, the proportional relationship between the preheat pulse width t1 and the ejection amount Vd is expressed as follows: Kp2 = ΔVdp / Δt1, where the preheat pulse dependence coefficient is defined as Kp2. The dependence coefficient Kp2 takes different values depending on the horizontal structure of the recording head, the physical properties of the ink, and the like.

Therefore, in the present embodiment, as shown in FIG. 25, the ink mixture is increased based on the temperature dependence of the ink ejection amount described in the first embodiment and the preheat pulse dependence described above. The pulse width of the preheat pulse P1 for
A desired ink temperature distribution is formed by the heat conduction during the interval time T12 from the energy of 1 and a desired ink ejection amount is obtained by the main heat pulse P2.

<Image Recording> FIG. 26 is a block diagram showing a configuration of a portion related to the recording head of this embodiment, FIG. 27 is a flowchart of an image recording process according to this embodiment, and FIG. 5 is a timing chart showing a signal waveform in FIG. Hereinafter, description will be made with reference to these figures.

First, the image recording processing of this embodiment will be described with reference to FIG.

The CPU 13 has an image data transfer circuit 160
2, the print data d0 to d3 generated by the image processing and the heater control signals B / S0 to B / S3 are transferred (step S511) until the data is transferred for one scan (step S5).
12) Repeat.

Then, a recording operation described later (step S
7) is performed, and the process is repeated until printing of a printing area corresponding to one scan is performed (step S513). The above processing (S
Steps 511 to S513) are repeated until the recording operation of the entire image area is completed (step S514), and an image is formed on the recording medium.

The CPU 13 transmits the print data d0 to d3 for one scan and the heat control signals B / S0 to B / S3 from the page memory area of the RAM 14 to the drive timing generation circuit 1611, and receives the drive data. Reference numeral 1611 outputs a start instruction signal (not shown) to the image data transfer circuit 1602. Upon receiving the start instruction signal, the image data transfer circuit 1602 transmits the transfer clock SDCLK
Dn and the heater control signal B / S
n is transferred to the shift registers 301 and 302.

The drive timing generation circuit 1611 that has output the start instruction signal has an internal counter, and determines the print head temperature Th of the temperature sensor 9 disposed on the print head 10 at a desired timing by using the preheat pulse width. A print head temperature read signal for reading to the control circuit 1609 is output.

At this time, the preheat pulse width control circuit 1609 performs A / D conversion for analog-digital conversion of the recording head temperature Th sequentially detected by the temperature sensor 9.
A D converter, a latch circuit for determining the output of the A / D converter, and an LUT storing the data of the preheat pulse width T1 for the output (recording head temperature Th) of the latch circuit, that is, the above-described temperature correction table are stored. The recording head temperature Th is determined by the recording head temperature read signal, and the data is input to the LUT to obtain the preheat pulse width T1.

Then, the drive timing generation circuit 1611
Outputs a preheat pulse write signal to the preheat pulse width control circuit 1609 to output a preheat pulse width signal, which is data indicating the preheat pulse width T1, and outputs a preheat pulse write signal to the preheat pulse generation circuit 161.
A preset control signal (not shown) for presetting the preheat pulse width signal to 0 is output, and the preheat pulse width T1 of the preheat pulse signal P1 is determined.

Thereafter, the drive timing generation circuit 1611
Is the shift register 3 from the image data transfer circuit 1602.
After the (m + 1) -bit data is transferred to 01 and 302, a latch signal LAT is output to latch circuits 311 and 312. Here, the latched print data dn and heater control signal B / Sn indicate that only the i-th nozzle among the plurality of nozzles of the print head 10 is dn [i], B
/ Sn [i].

The drive timing generation circuit 1611 that has output the latch signal LAT uses the print timing signal, which is an internal signal that defines the print head ejection timing, to generate
The preheat pulse generation circuit 16 outputs the preheat start signal.
Output to 10

Upon receiving the preheat start signal, preheat pulse generation circuit 1610 outputs preheat pulse signal P1 having pulse width T1 determined by the preheat pulse width signal to gate circuit 321 and drive timing generation circuit 1611.

The drive timing generation circuit 1611 having received the preheat pulse signal P1 detects the falling edge of the preheat pulse signal P1, and detects an interval time T which is set in advance by a built-in counter.
After a lapse of time corresponding to 12, a main heat start signal is output to main heat pulse generation circuit 1605. Upon receiving the main heat start signal, the main heat pulse generating circuit 1605 outputs a main heat pulse signal P2 having a predetermined pulse width T2.

The above-described print data dn [i], heater control signal B / Sn [i], preheat pulse signal P1,
The main heat pulse signal P2 is supplied to the gate circuit 321.
Input to [i].

The gate circuit 321 constitutes a logic circuit for the above-mentioned input signal, and is connected to a driving element (a transistor in the figure) for driving the heating resistance elements 201 and 202 of the recording head. .

As the logic of the gate circuit 321, the preheat pulse signal P1 is output to each transistor for driving the heating resistance elements 201 and 202. When dn [i] = 1 and the heater control signal B / Sn [i] = 1, the main heat pulse signal P2 is used to drive the heating resistance elements 201 and 202. Output to each transistor. Print data dn [i] = 1 indicating small ejection drive and heater control signal B / Sn [i] = 0
In the case of (1), the main heat pulse P2 is output only to the transistor that drives the heating resistance element 202, and is not output to the transistor that drives the heating resistance element 201. When print data dn [i] = 0 indicating non-ejection drive, the logic is such that the main heat pulse P2 is not output to any of the transistors.

As data latched at the first timing shown in FIG. 28, print data dn [i] = 1, heater control signal B / Sn [i] = 0 (small ejection drive), and preheat pulse After the energy consumption based on P1, the energy consumption based on the main heat pulse signal P2 is only the heating resistance element 202 [i].

The data latched at the second timing includes print data dn [i] = 1, heater control signal B
/ Sn [i] = 1 (large ejection drive)
After the energy consumption based on the pulse P1, the energy consumption based on the main heat pulse signal P2 is generated by both the heating resistance elements 201 [i] and 202 [i].

Further, the data latched at the third timing is the recording data dn [i] = 0, the heater control signal B
/ Sn [i] = 1 (non-ejection drive),
After the energy consumption based on the pulse P1, no energy consumption based on the main heat pulse signal P2 occurs.

As described above, according to the present embodiment,
Density change and density unevenness due to temperature fluctuation and ink density fluctuation during printing operation are suppressed, and the linearity of gradation reproduction characteristics can be maintained.

[Third Embodiment] Hereinafter, a third embodiment of the present invention will be described. Components similar to those of the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted. I do. Hereinafter, differences from the above two embodiments will be described.

<Print Head> FIG. 29 is a sectional view showing the structure of a print head used in this embodiment. (A) is a longitudinal sectional view along the ink flow path, and (b) is a transverse sectional view in the nozzle arrangement direction. Hereinafter, the configuration of the recording head will be described with reference to FIG.

The recording head 10 is based on a support 1 mainly made of aluminum, and includes a multi-layer element substrate 2 formed on the support 1 by a semiconductor process and a printed board 3 on which electric components are mounted. It is formed by being fixed with an adhesive.

On the element substrate 2, a heating resistor 203 as an ejection energy generating element for ejecting ink is provided.
(Electro-thermal converter) is formed, covered with a protective film 210 such as silicon oxide or silicon nitride, and has a structure that does not come into contact with ink.

FIG. 30 is an enlarged view of a portion corresponding to the [i] th nozzle in FIG. 6C. Hereinafter, the configuration of each nozzle will be described with reference to FIG.

Heating resistance element 2 provided in each nozzle
03 denotes three contacts 211 and 21 shown by broken lines.
2,213. The contact 213 is for connecting to a common electrode for supplying the drive voltage Vop. The contact 212 is connected to the element substrate 2
In the same manner, the contact 211 is connected to the collector electrode (drain electrode) of the transistor 231 formed on the element substrate 2. It is for making a connection.

At this time, in the present embodiment, the ink ejection amount due to the ejection energy (heat generation amount) generated when the transistor 232 is driven alone and the ejection energy (heat generation amount) generated when the transistor 231 is driven alone. The ratio with the ink ejection amount is set to be 2: 1. It is clear that the ink ejection amount ratio may be set to a value other than the above.

Therefore, in this embodiment, the transistor 23
A three-level gradation expression is possible in which large ejection is performed when only 2 is driven, small ejection is performed when only the transistor 231 is driven, and non-ejection is performed when both transistors are not driven.

<Image Recording> FIG. 31 is a block diagram showing the configuration of a portion related to the recording head of this embodiment, and FIG. 32 is a timing chart showing signal waveforms at various portions of this embodiment. Hereinafter, description will be made with reference to these figures.

The print data d0 to d3 for one scan from the page memory area of the RAM 14 and the heat control signal B / S
0 / B / S3 CPU 13 is a drive timing generation circuit 16
08, the drive timing generation circuit 1608 that has received the image transfer end indicates that the image data transfer circuit 160
2, a start instruction signal (not shown) is output. The image data transfer circuit 1602 that has received the start instruction signal transfers the print data dn and the heater control signal B / Sn to the shift registers 301 and 302 in synchronization with the transfer clock SDCLK.

The drive timing generation circuit 1608 which has output the start instruction signal has an internal counter, and has an interval with respect to the recording head temperature Th of the temperature sensor 9 disposed on the recording head 10 at a desired timing. An interval time signal indicating data of the time T12 is read, and an interval time T12 which is a driving parameter of the recording head is set.

Thereafter, drive timing generation circuit 1608
Is the shift register 3 from the image data transfer circuit 1602.
After transferring (m + 1) -bit data to 01 and 302,
A latch signal LAT is output to the latch circuits 311 and 312. Here, the latched print data dn and the heater control signal B / Sn are used as signals for the i-th nozzle of the plurality of nozzles of the print head 10, and dn [i], B /
It is represented by Sn [i].

The drive timing generation circuit 1608 that has output the latch signal LAT uses a print timing signal, which is an internal signal that defines the print head ejection timing, to generate
The preheat pulse generation circuit 16 outputs the preheat start signal.
04.

Upon receiving the preheat start signal, the preheat pulse generation circuit 1604 converts the preheat pulse signal P1 having a preset pulse width T1 into the gate circuit 3
22.

The drive timing generation circuit 1608 that has output the preheat start signal outputs the preheat pulse P1 having a pulse width T1 preset by a built-in counter.
After a lapse of time corresponding to the interval time T12 determined above, the main heat pulse generation circuit 16
In step 05, a main heat start signal is output. Upon receiving the main heat start signal, the main heat pulse generating circuit 1605 outputs a main heat pulse signal P2 having a predetermined pulse width T2.

The recording data dn [i], heat control signal B / Sn [i], preheat pulse signal P1,
The main heat pulse signal P2 is supplied to the gate circuit 322.
Input to [i].

The gate circuit 322 constitutes a logic circuit for the above-mentioned input signal, and is connected to a driving element (a transistor in the figure) for driving the heating resistance element 203 of the recording head.

As the logic of the gate circuit 322, the preheat pulse signal P1 is output from the transistor 232 [i] which performs large ejection driving. Also, the print data indicating the large ejection drive, dn [i] = 1, and the heater control signal B / Sn
If [i] = 1, the main heat pulse signal P
2 is output to the transistor 232 [i]. When the print data indicating the small ejection drive, dn [i] = 1 and the heater control signal B / Sn [i] = 0, the main heat pulse P2 is output to the transistor 231 [i]. In the case of dn [i] = 0, print data indicating non-ejection drive, the main heat pulse P2 is applied to any of the transistors 23
2 [i] and 231 [i] are not output.

As data latched at the first timing shown in FIG. 32, print data dn [i] = 1, heater control signal B / Sn [i] = 0 (small ejection drive), and preheat pulse Heating resistance element 20 based on P1
3 is performed by the transistor 232 [i], and the energy consumption based on the main heat pulse signal P2 is performed by the transistor 231 [i].

The data latched at the second timing includes print data dn [i] = 1, heater control signal B
/ Sn [i] = 1 (large ejection drive)
The energy consumption of the heating resistance element based on the pulse P1 and the main heat pulse P2 is determined by the transistor 232
This is performed in [i].

Further, the data latched at the third timing is the recording data dn [i] = 0, the heater control signal B
/ Sn [i] = 1 (non-ejection drive),
Energy consumption of the heating resistance element 203 based on the pulse P1 is performed by the transistor 232 [i], and energy consumption based on the main heat pulse signal P2 does not occur.

As described above, according to the present embodiment,
Density change and density unevenness due to temperature fluctuation and ink density fluctuation during printing operation are suppressed, and the linearity of gradation reproduction characteristics can be maintained.

[Fourth Embodiment] Hereinafter, a fourth embodiment of the present invention will be described. Components similar to those in the first to third embodiments are denoted by the same reference numerals, and description thereof will be omitted. I do. Hereinafter, differences from the above embodiment will be described.

<Recording Head> FIG. 33 is a block diagram showing a configuration of a portion related to the recording head of this embodiment.
Description will be made with reference to this figure.

On the element substrate 2, two driving voltages Vop1 and Vop2 (where Vop1> V) are supplied from the driving voltage power supply to the heating resistance elements 204 disposed in each nozzle.
transistors 242, 2 for controlling the supply of
41 is formed by a semiconductor process.

At this time, in this embodiment, the transistor 2
42, the amount of ink ejected at the ejection energy (heat generation amount) by the driving voltage Vop1 supplied to the heating resistance element 204, and the heating resistance element 20
The ratio of the drive voltage Vop2 to the ink discharge amount at the discharge energy (heat generation amount) is set to 2: 1. It is obvious that the ink ejection amount ratio may be set to a value other than the above.

Therefore, in this embodiment, the transistor 2
42 (drive voltage Vop1) is driven, large discharge is performed, when the transistor 241 (drive voltage Vop2) is driven, small discharge is performed, and when both transistors are not driven, non-discharge is performed. And

<Image Recording> FIG. 34 is a timing chart showing the state of the signal waveform in each section in this embodiment. Hereinafter, the operation at the time of image recording according to the present embodiment will be described with reference to FIGS.

Recording data dn [i], heat control signal B
/ Sn [i], the preheat pulse signal P1, and the main heat pulse signal P2 are input to the gate circuit 323 [i].

The gate circuit 323 constitutes a logic circuit for these input signals, and is connected to a driving element (a transistor in the figure) for driving the heating resistance element 204 of the recording head.

As the logic of the gate circuit 323, the preheat pulse signal P1 is output to the transistor 242 [i] which performs large ejection driving. Also, the print data indicating the large ejection drive, dn [i] = 1, and the heater control signal B / Sn
If [i] = 1, the main heat pulse signal P
2 is output to the transistor 242 [i]. When dn [i] = 1 and the heater control signal B / Sn [i] = 0, the main heat pulse P2 is output to the transistor 241 [i]. In the case of dn [i] = 0, the print data indicating the non-ejection drive, the main heat pulse P2 is applied to any of the transistors 24
The logic is not output to 2 [i] and 241 [i].

The data latched at the first timing shown in FIG. 34 is print data dn [i] = 1, heater control signal B / Sn [i] = 0 (small ejection drive), and preheat pulse P1 Energy consumption of the heating resistance element 204 based on the transistor 242 [i] (driving voltage V
op1), the energy consumption based on the main heat pulse signal P2 is reduced by the transistor 241 [i].
(Drive voltage Vop2).

The data latched at the second timing is as follows: print data dn [i] = 1, heater control signal B / S
n [i] = 1 (large ejection drive), and the energy consumption of the heating resistance element based on the preheat pulse P1 and the main heat pulse P2 is determined by the transistor 242
[I] (drive voltage Vop1).

Further, the data latched at the third timing is the recording data dn [i] = 0, the heater control signal B
/ Sn [i] = 1 (non-ejection drive),
The energy consumption of the heating resistance element 203 based on the pulse P1 is determined by the transistor 232 [i] (driving voltage Vop1).
And no energy is consumed based on the main heat pulse signal P2.

As described above, according to the present embodiment,
Density change and density unevenness due to temperature fluctuation and ink density fluctuation during printing operation are suppressed, and the linearity of gradation reproduction characteristics can be maintained.

[0214]

[Other Embodiments] In the above embodiments, the description has been made assuming that the droplets ejected from the recording head are ink, and that the liquid contained in the ink tank is ink. Is not limited to ink. For example, an ink tank may contain a processing liquid discharged to a recording medium in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

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 performing ink ejection 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 nucleate boiling to an 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.

The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. 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 a 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-angled liquid flow path) as disclosed in the above-mentioned respective specifications, The configurations described in U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose a configuration in which the heat acting surface is arranged in a bending region, are also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slot is used as a discharge section of an electrothermal transducer for a plurality of electrothermal transducers, and an opening for absorbing pressure waves of thermal energy is discharged. A configuration based on JP-A-59-138461, which discloses a configuration corresponding to each unit, 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 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 the recording mode of only the mainstream color such as black, and may be a single recording head or a combination of plural recording heads. Alternatively, the apparatus may be provided with at least one of full colors by color mixture.

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

An object of the present invention is to supply a storage medium (or a recording medium) in which program codes of software for realizing the functions of the above-described embodiments are recorded to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. It is needless to say that the present invention can also be achieved by a CPU or an MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. Also,
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the operating system (OS) running on the computer based on the instructions of the program code.
It goes without saying that a case where the functions of the above-described embodiments are implemented by performing some or all of the actual processing, and the processing performs the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. Needless to say, the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

In the case where the present invention is applied to the storage medium, the storage medium described above (FIGS. 12, 13,
8, FIG. 20, FIG. 21, and / or FIG. 27).

[0228]

As described above, according to the present invention,
Based on a combination of the selected type of ink and the number of ink droplets, a predicted density to be actually recorded on the recording medium is obtained. If the difference between the predicted density and the density data is larger than a predetermined value, the ink density is calculated. And the number of ink droplets can be selected again to record a more faithful image with the input data.

Therefore, even when the ink density changes during the printing operation, it is possible to print a high quality and high quality image by suppressing the image quality deterioration due to the density change, density unevenness, white spots and the like. There is.

[Brief description of the drawings]

FIG. 1 is a block diagram of a portion related to a printhead of an inkjet printing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an overall configuration of the inkjet recording apparatus according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between an ink ejection amount and a transmission density.

FIG. 4 is a diagram illustrating an example of an ink distribution table for image density data.

FIG. 5 is an external perspective view illustrating a configuration of a print engine according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of a recording head according to the first embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view of a part of the recording head of FIG. 6;

FIG. 8 is a diagram illustrating a waveform of a drive pulse according to the first embodiment of the present invention.

FIG. 9 is a graph showing a relationship between a recording head temperature and an ink ejection amount.

FIG. 10 is a graph showing a relationship between an interval time and a discharge amount.

FIG. 11 is a diagram illustrating a waveform of a driving pulse according to the temperature of the recording head according to the first embodiment of the present invention.

FIG. 12 is a flowchart of image processing according to the first embodiment of the present invention.

FIG. 13 is a flowchart of an image data input process according to the first embodiment of the present invention.

FIG. 14 is a diagram illustrating an example of a distribution table by an ink distribution process according to the first embodiment of the present invention.

FIG. 15 is a graph showing a relationship between an ink non-ejection continuation time and an ink density increase rate.

FIG. 16 is a graph showing the relationship between the number of continuous ink non-ejection dots and the rate of increase in ink density.

FIG. 17 is a diagram illustrating an example of an ink density increase table with respect to the number of continuous ink non-ejection dots according to the first embodiment of the present invention.

FIG. 18 is a flowchart of a re-ink distribution process according to the first embodiment of the present invention.

FIG. 19 is a diagram illustrating an example of an error diffusion matrix used in error diffusion processing.

FIG. 20 is a flowchart of an error diffusion process according to the first embodiment of the present invention.

FIG. 21 is a flowchart of an image recording process according to the first embodiment of the present invention.

FIG. 22 is a timing chart showing states of respective signals according to the first embodiment of the present invention.

FIG. 23 is a block diagram of a portion related to a recording head according to a modified example of the first embodiment of the present invention.

FIG. 24 is a graph showing a relationship between a preheat pulse width and an ink ejection amount.

FIG. 25 is a diagram illustrating a waveform of a drive pulse according to the temperature of the printhead according to the second embodiment of the present invention.

FIG. 26 is a block diagram of a portion related to a recording head according to a second embodiment of the present invention.

FIG. 27 is a flowchart of an image recording process according to the second embodiment of the present invention.

FIG. 28 is a timing chart showing the state of each signal according to the second embodiment of the present invention.

FIG. 29 is a cross-sectional view illustrating a configuration of a recording head according to a third embodiment of the present invention.

30 is an enlarged cross-sectional view of a part of the recording head of FIG. 29.

FIG. 31 is a block diagram of a portion related to a recording head according to a third embodiment of the present invention.

FIG. 32 is a timing chart showing the state of each signal according to the third embodiment of the present invention.

FIG. 33 is a block diagram of a portion related to a printhead according to a fourth embodiment of the present invention.

FIG. 34 is a timing chart showing the state of each signal according to the fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support body 2 Element board 3 Printed board 4 Wire bonding 6 Ink tank 8 Ink droplet 9 Temperature sensor 10 Recording head 11 Image input part 12 Operation part 13 CPU 14 RAM 15 ROM 16 Engine part 17 Ink receiver 19 Capping unit 200- 204 Heating resistance element 231,232,241,242 Transistor 301,302 Shift register 311,312 Latch circuit 321-323 Gate circuit 501 Top plate 502 Wall plate 701 Ink inlet 702 Ink supply path 703 Common liquid chamber 704 Pressure chamber 705 Ink Narrow channel 706 Discharge port 1501 Control program group 1502 Temperature correction table 1503 γ correction conversion table 1504 Ink distribution table 1505 Ink density rise table 1601 Drive voltage power supply 602 Image data transfer circuit 1603 A / D converter 1604 Preheat pulse generation circuit 1605 Main heat pulse generation circuit 1606 Drive timing generation circuit 1607 Interval time control circuit 1608 Drive timing generation circuit 1609 Preheat pulse control circuit 1610 Preheat pulse Derived circuit 1611 Drive timing generation circuit 1612 Drive voltage power supply 1801 Flexible cable 1802 Carriage 1803 Detector 1804 Linear encoder 1805 Guide shaft 1806 Carriage motor 1807 Pulley 1808 Drive belt 1809 Transport motor 1810 Drive belt 1811 Transport roller

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kazumasa Matsumoto 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2C056 EA04 EA06 EA08 EB07 EB29 EB30 EB38 EB41 EC07 EC21 EC28 EC29 EC42 EC76 ED01 ED03 ED05 ED07 FA03 FA10 FA11 HA05 JA13 JB04 JC20 JC23 2C057 AF21 AF25 AG12 AG46 AH13 AL25 AL37 AM16 AM21 AN01 AN02 AR18 CA01 CA04 CA05 CA07 DB01 DB03 DC08

Claims (22)

[Claims] 1. An ink jet apparatus that performs multi-tone printing by using a plurality of ink jet print heads that discharge inks having different densities and changing the type of ink and the number of ink droplets discharged to each pixel on a print medium. A recording device for converting input data into density data of each pixel in a recording area; selecting means for selecting a target pixel from the recording area; An ink distributing means for selecting a combination of the type of ink and the number of ink droplets used when recording the target pixel; and a density prediction for obtaining a predicted density when the target pixel is recorded on a recording medium in accordance with the combination. Means, if the difference between the predicted density and the density data is greater than a predetermined value, select again the combination of the type of ink to be used and the number of ink droplets And ink distribution unit, according to the combination of the final number of types and ink drops of the selected ink jet recording apparatus characterized by comprising a drive means for generating drive signals to be transmitted to the recording head. 2. The method according to claim 1, wherein the density estimating means includes an elapsed time measuring means for measuring an elapsed time after each recording head has ejected the ink, and an ink droplet ejected when recording the target pixel from the elapsed time. 2. The ink jet recording apparatus according to claim 1, further comprising an ink density calculating unit for calculating a density. 3. The re-ink distributing unit selects a combination different from the combination selected by the ink distributing unit, and selects a combination different from the combination selected by the density estimating unit on the recording medium according to the selected combination. Calculating a predicted density, comparing the predicted density with the predicted density for the selected combination of the ink distribution means, and finally selecting a combination having a small difference from the density data with the predicted density. The ink jet recording apparatus according to claim 1 or 2, wherein: 4. An error diffusion means for distributing a difference between the predicted density of the finally selected combination and the density data to pixels around the pixel of interest in accordance with a predetermined pattern. The inkjet recording apparatus according to claim 3. 5. The recording head is configured to be capable of discharging ink droplets of different volumes, and the re-ink distributing means is configured to change the volume of the ink droplet discharged from at least one recording head. 5. The method according to claim 1, wherein
The inkjet recording device according to any one of the above. 6. The ink jet recording apparatus according to claim 5, wherein the recording head has two energy generating elements capable of selectively applying the drive signal. 7. The recording head according to claim 1, wherein the recording head ejects ink using thermal energy, and the energy generating element is a thermal energy converter for generating thermal energy applied to the ink. The ink jet recording apparatus according to claim 6, wherein 8. The ink dispenser according to claim 1, wherein the re-distribution unit changes the ink distribution unit to use a type of ink that is not used in the combination determined by the ink distribution unit. Item 6. The ink jet recording apparatus according to item 1. 9. A temperature detecting means for detecting a temperature of the recording head, and a driving signal for changing the driving signal based on the detected temperature so that a volume of an ink droplet ejected from the recording head becomes constant. The inkjet recording apparatus according to claim 1, further comprising a control unit. 10. The ink jet recording apparatus according to claim 9, wherein said drive signal includes at least two pulse signals. 11. The driving signal control unit changes at least one of the pulse widths.
3. The ink jet recording apparatus according to claim 1. 12. The apparatus according to claim 1, wherein the drive signal control means changes an interval between the two pulse signals.
0. The ink jet recording apparatus according to 0. 13. An ink jet apparatus that performs multi-tone printing by using a plurality of ink jet print heads that eject inks having different densities and changing the type of ink and the number of ink droplets ejected to each pixel on a recording medium. A recording method, comprising: converting input data into density data of each pixel in a recording area; selecting a pixel of interest from the recording area; An ink distributing step of selecting a combination of the type of ink and the number of ink droplets used when recording the target pixel; and a density prediction for obtaining a predicted density when the target pixel is recorded on a recording medium according to the combination. And if the difference between the predicted density and the density data is greater than a predetermined value, re-select a combination of the type of ink to be used and the number of ink drops. An ink-jet recording method, comprising: a re-ink distribution step; and a driving step of generating a driving signal to be transmitted to the recording head in accordance with a combination of the type of ink and the number of ink drops finally selected. . 14. The density estimating step includes: an elapsed time measuring step of measuring an elapsed time after each recording head has ejected ink; and an ink droplet ejected when recording the target pixel from the elapsed time. 14. The ink jet recording method according to claim 13, further comprising an ink density calculating step of calculating a density. 15. The ink re-distribution step in which a combination different from the combination selected in the ink distribution step is selected and recorded on a recording medium according to the combination selected in the density estimation step. And calculating a predicted density having a small difference from the density data and finally selecting a combination having a small difference from the density data. The inkjet recording method according to claim 13 or 14, wherein: 16. An error diffusion step of distributing a difference between the predicted density of the finally selected combination and the density data to pixels around the target pixel according to a predetermined pattern. The inkjet recording method according to claim 15. 17. A method according to claim 17, wherein the recording head is configured to discharge ink droplets of different volumes, and in the re-ink distribution step, the volume of ink droplets discharged from at least one recording head is changed. The inkjet recording method according to any one of claims 13 to 16. 18. The method according to claim 13, wherein in the ink re-distribution step, a change is made to use a type of ink that is not used in the combination determined in the ink distribution step. Item 2. The inkjet recording method according to item 1. 19. A temperature detecting step for detecting a temperature of the recording head, and a driving signal for changing the driving signal based on the detected temperature so that a volume of an ink droplet ejected from the recording head becomes constant. The method according to claim 13, further comprising a control step. 20. The ink jet recording method according to claim 19, wherein at least two pulse signals are generated as the driving signal in the driving step. 21. The ink jet recording method according to claim 20, wherein at least one of the pulse widths is changed in the drive signal control step. 22. The ink jet recording method according to claim 20, wherein in the driving signal control step, an interval between the two pulse signals is changed.