JPH0858081A - Ink jet printing device - Google Patents

Abstract

PURPOSE: To prevent the bleeding of pictures, etc., from occurring on a printing medium and thus perform printing in a satisfactory fixing-condition. CONSTITUTION: A sensor 708 is provided to measure the water content of a printing (recording) medium 707 through its transfer passage and, before the recording is effected on the recording medium 707 by discharging ink from an ink jet head 702, the water content is measured. According to the measured values, the amount of the ink discharged from the ink jet head 702 is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing apparatus, and more particularly to an arrangement for fixing a print medium.

[0002]

2. Description of the Related Art With the spread of copiers, word processors, information processing equipment such as computers, and communication equipment, an ink jet type recording head is used as one of image forming (recording) equipment of these equipment. Digital image recording is becoming popular. In such a printing device (hereinafter, also referred to as a recording device),
In order to improve the recording speed, a recording head having a plurality of recording elements integrated and arranged (hereinafter referred to as a multi-head in this section) having a plurality of ink ejection ports and liquid paths is used. Along with the progress of compatibility, there are many devices that are provided with a plurality of the multi-heads at the same time.

In the ink jet recording apparatus, since the ink droplets ejected from the multi-head are absorbed by the recording medium to form an image, the fixing property, that is, the ink absorbing property of the recording medium greatly influences the image quality. It is clear that this is one of the factors. For example, when the ink absorber of the recording medium is scarce, the inks landed on the surface of the recording medium come into contact with each other before being absorbed, and if these inks are of different colors, blurring of the boundary causes a remarkable deterioration of the image. .

As a means for solving such a problem, it is possible to cite the use of a dedicated coated paper which is rich in ink absorption and has good color developability. Recently, what kind of alternative is used? This paper is also provided with quick-drying ink that absorbs quickly, and it is possible to perform recording on most plain papers without considering the problem regarding ink absorption.

On the other hand, in the inkjet method, it is relatively easy to print a high-definition full-color image on various media. Therefore, in addition to plain paper and special-purpose coated paper, which are already in widespread use, an OHP film is also available. , Glossy paper, cloth,
There is also an increasing demand for printing on various print media (hereinafter, also referred to as recording media) such as leather that have greatly different ink absorbing capacities. Since it is difficult to form an image in this case only by the characteristics of the ink, it is common to change the recording method according to each recording medium. For example, when using plain paper or coated paper, which has a relatively large ink absorption capacity, a method of recording a relatively large amount of ink in the same area of the recording medium at one time is adopted, and recording with slow ink absorption such as an OHP film is performed. For the medium, a method is adopted in which the amount of ink applied to the same area at one time is reduced, and an image is completed by several recording scans while waiting for absorption of the applied ink.

As an invention aiming at improving the fixing property depending on the properties of the recording medium, for example, JP-A-1-29 is available.
No. 0429 and JP-A No. 61-16860. The former discloses a method of appropriately controlling the temperature of a heating device such as a fixing device according to the thickness and surface condition of the paper. According to this method, in the case of recording paper with poor fixability, high temperature is used. It is possible for the operator of the recording apparatus to set an appropriate heater temperature such that the temperature is low in a high humidity state where the recording paper contains a large amount of water.

The latter discloses setting the recording standby time for each line feed according to the hygroscopicity of the recording medium.
Here, the case of recording on a medium having particularly poor hygroscopicity such as an OHP film is taken as an example, and the line feed operation is delayed by the recording waiting time setting means for each line feed so that the medium is not fed until the ink is sufficiently dried. By doing so, a time for absorption is provided so that print quality is not impaired. As described above, in the ink jet system, image formation has been realized on various media having different ink absorbencies according to the ink absorbability.

By the way, the state of the recording medium varies depending on the type of the medium, but is greatly affected by the humidity of the recording environment. For example, in a place where the environmental humidity is high, the recording medium itself also absorbs moisture, and the medium that absorbs moisture in this way further deteriorates its ability to absorb ink, or the medium itself deforms.

In order to solve the problems caused by such environmental humidity, some methods have been proposed in which a recording device is provided with a hygrometer and various problems are solved depending on the value.

For example, according to the structure disclosed in Japanese Patent Laid-Open No. 1-157859, in an ink jet recording apparatus having a fixing heater for promoting ink fixing, the humidity in the vicinity of a recording area where recording is performed on a recording medium and By detecting the atmospheric humidity outside the recording device and controlling the heat generation temperature of the heater based on the humidity of both, dew condensation inside the device is prevented,
The ejection quality is stabilized and the deterioration of recording quality does not occur.

The structure disclosed in Japanese Patent Laid-Open No. 58-194582 is intended to provide a humidity detecting means in the printer so that the recording is not hindered by the bending of the recording paper due to the humidity during recording. . According to this, when it is determined that the recording paper is bent due to the ambient humidity, by feeding an appropriate amount of the recording paper,
Since the recording head is started to run after the deflection is automatically removed, accidents such as the recording head that runs can be caught by the recording paper and damaged, etc. can be prevented, and stable recording can be performed in good condition. It can be carried out.

Further, Japanese Patent Laid-Open No. 62-32068 is provided with a sensor for detecting the moisture absorption amount of the recording paper after recording and before sending out, and the moisture absorption amount detected by this sensor is the allowable moisture absorption amount. Disclosed is an ink jet recording apparatus provided with a drying means for drying the recording paper so that the amount of moisture absorption of the recording paper becomes the upper limit when the amount is larger than the upper limit. That is, the invention described in this publication is to increase the recording efficiency by controlling an appropriate amount of the drying means for preventing the paper, which has already been recorded and has absorbed moisture, from being jammed when discharged. The main purpose is. Here, as a sensor that detects the amount of moisture absorption, an image density sensor that uses the fact that the image density is considered to be approximately equal to the amount of moisture absorption by recording, and the specular reflectance on the ink surface increases in the area where much ink is attached. A specular reflectance measurement sensor using the above, an electrostatic capacitance measurement sensor utilizing the change of the electrostatic capacitance according to the change of the ink adhesion amount, and a humidity sensor measuring the humidity in the vicinity are mentioned. However, in any case, the purpose of these sensors is to determine the amount of ink adhered to the recording paper after printing.

As described above, in the ink jet recording system, various measures have been taken against the influence of the type of recording medium and the moisture absorption during printing.

[0014]

However, all of the above-mentioned conventional techniques have dealt with the case where the environmental humidity influences the print quality, but the medium before the printing which absorbs moisture is directly applied. The effect on the image has not been fully considered.

That is, it can be said that the factor that most affects the fixability and the image quality in a high humidity environment is the amount of water actually absorbed by the recording medium before printing.
As the amount of water already absorbed in the recording medium before printing is large, the absorbing ability of newly landed ink is lowered and the fixing property is deteriorated. Further, when the landed inks come into contact with each other on the surface of the medium and they are of different colors, the image is deteriorated as a boundary blur.

There is also the fact that the hygroscopicity varies depending on the recording medium even if the environmental humidity is the same. For example, on plain paper with a high fiber density, a slight change in humidity does not cause a large change in the image, but in an OHP film with a special ink absorption layer, a slight change in humidity greatly affects its fixability. There are many. Further, in the case of a cloth made of a material such as cotton, since the water absorbency is particularly higher than that of other cloths, boundary bleeding is likely to appear remarkably.

As described above, even if the moisture absorption state of the recording medium is surely greatly affected by the recording environment humidity,
It can be said that the amount of water actually contained in each recording medium directly affects the print quality, and the recording environment itself does not directly affect the image adverse effect but is a secondary factor.

On the other hand, the above-mentioned Japanese Patent Laid-Open No. 1-157.
In Japanese Laid-Open Patent Publication No. 859 and Japanese Patent Laid-Open No. 58-194582, measures are taken to measure the humidity of the recording environment and assume the moisture absorption state of the recording medium based on the measured value, that is, the fixing property and the bending of the recording paper. I'm just trying.

Further, in Japanese Patent Laid-Open No. 62-32068, a sensor for detecting the amount of moisture absorption of recording paper is provided. However, the amount of moisture absorption detected here is for knowing the amount of ink of the already recorded paper. This means also uses a method such as an image density sensor or a specular reflectance measuring sensor to indirectly determine the water content from a phenomenon peculiar to the portion where the ink is attached. Furthermore, the purpose is also to control the drying means to prevent paper jams during paper discharge,
It does not attempt to control the image quality at the time of printing by detecting the water content of the recording paper before printing.

As described above, in the conventional ink jet printing apparatus, one that detects the moisture content of the medium before printing, which directly affects the image, prevents bleeding at the boundary of the image and controls the fixing property, Not provided.

The present invention has been made from the viewpoint of the above-mentioned prior art, and an object of the present invention is to control various printing media by controlling the printing operation according to the water content of the printing media before printing. Prevents image bleeding,
An object of the present invention is to provide an inkjet printing apparatus capable of printing in a good fixing state.

[0022]

Therefore, according to the present invention,
In an inkjet printing apparatus that uses an inkjet head and ejects ink from the inkjet head onto a print medium to perform printing, a water content detection for detecting the water content of the print medium before receiving the ink ejected from the inkjet head And a control means for controlling the printing operation of the inkjet head in the printing according to the water content detected by the water content detection means.

Further, in an inkjet printing apparatus which uses an inkjet head and ejects ink from the inkjet head onto a print medium for printing, the inkjet means is provided in a transport means for transporting the print medium and a transport path by the transport means. And a water content detection sensor provided upstream of the head for detecting the water content of the print medium.

[0024]

According to the above construction, the water content of the print medium before printing is performed by the ink ejected from the ink jet head can be detected in advance. It is possible to change the ejection amount in one ejection.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 7 is a perspective view showing a schematic structure of a color printer as an ink jet printing apparatus according to an embodiment of the present invention.

In this figure, reference numeral 701 is an ink jet cartridge for ejecting black (K), cyan (C), magenta (M) and yellow (Y) inks, respectively. These inkjet cartridges 70
Each of No. 1 is integrally configured by an ink tank 709 that stores each ink and an inkjet head 702 having a plurality of ejections.

FIG. 8 is a schematic view showing the ejection ports arranged on the ink jet head in the z direction shown in FIG.

In FIG. 8, reference numeral 801 denotes an ejection port arranged on the head 702. In this figure, the discharge ports 801 are arranged in parallel along the Y axis in the figure, but for example, XY in the figure
It may have some inclination on a plane. In this case, while the head moves in the traveling direction X, ink is ejected from each ejection port while shifting the timing.

Referring again to FIG. 7, reference numeral 703 denotes a paper feed roller, which rotates together with the auxiliary roller 704 in the direction of the arrow while regulating the recording paper 707 as a print medium in a certain direction. It is conveyed intermittently in the y direction. Reference numeral 705 denotes a pair of paper feed rollers, which feed the recording paper and, like the rollers 703 and 704, regulate the recording paper 707 in a fixed direction. 706 is 4
Supporting the above ink jet cartridges 701,
It is a carriage that moves these together with recording. The carriage 706 stands by at the home position h at the position shown by the broken line in the figure when the recording operation is not performed or when the ejection recovery operation of the inkjet head 702 is performed.

Reference numeral 708 denotes a sensor which is provided in a part of the conveyance area of the recording paper 707 and measures the water content of the recording paper 707. In this embodiment, an electric resistance type sensor is used. This type of moisture meter utilizes the correlation between the amount of moisture in the medium and the electrical resistance when the medium is regarded as an electrical insulator.

FIG. 1 is a diagram schematically showing the water content measuring sensor 708.

When the recording paper 707 is fed, the two electrodes 1301 and 1302 come into contact with the surface of the recording paper 707, and a voltage of about 1.5 V is applied between both electrodes. Since the distance between the two electrodes is fixed, the resistance value R per unit length between both electrodes is detected based on the flowing current value. Since the easiness of current flow (resistance value) almost uniquely changes depending on the amount of water in the recording medium, if the type (characteristic) of the print medium is constant, the correlation between the amount of water in the print medium and the resistance value is Can be obtained in the form as shown in FIG.

However, since different types of print media have different correlations between the electric resistance and the water content, FIG.
As shown in (b), the relational expression between the two must be obtained in advance for each type of print medium used. Furthermore, even if the amount of water is the same, the characteristics that affect the image and the proper handling differ depending on the type of medium, so the final printing method is ultimately based on both the type of print medium and the detected electrical resistance. Establish.

In the embodiment shown in FIG. 1, the resistance value of the print medium is partially measured by setting the two electrodes at a relatively short distance. However, for example, the electrodes are brought into contact with both ends of the print medium. By adopting the configuration, the detection value is further averaged in the main scanning direction of the head, and the detection error of the water content in the print medium is alleviated.

In the structure shown in FIG. 7, when a recording command is detected, the paper feed roller 705 rotates and the recording paper 707 is sent to the recording area by the ink jet head 702 in the y direction shown in FIG. At the same time, the electrodes 1301 and 1302 of the moisture measuring sensor 708 are connected to the recording paper 7
When the surface of 07 is contacted, a voltage of 1.5 V is applied between both electrodes to measure the resistance value between both electrodes. The type of print medium is previously input by the user on the panel switch of the apparatus main body or the printer driver, and an appropriate print method is selected based on this information and the resistance value.

On the other hand, before the start of recording, the carriage 706 at the home position h moves in the x direction in response to a recording command, ejects ink from the n ejection ports 801 of the head 702, and onto the recording paper surface. Only the width D (see FIG. 8) is recorded. When the head 702 reaches the end of the recording paper and the recording for one line is completed, the carriage 706 returns to the home position and performs recording while operating in the x direction again. Alternatively, in the case of reciprocal recording, the recording for the next one line is performed at the stage of moving in the −x direction, that is, at the stage of returning to the home position. From the end of the previous recording to the start of the next recording, the paper feed roller 703 rotates in the arrow direction in the drawing to feed the paper in the y direction of a predetermined width. In this way, recording (printing) is completed on one sheet surface by repeating scanning of the carriage and sheet feeding.

The color printing method applied to plain paper in the ink jet printer of this embodiment described above will be described below.

Unlike a monochrome printer that prints only characters, it is necessary to satisfy various factors such as color development, gradation, and density uniformity when recording a color image. In particular, regarding the density uniformity, a slight variation in characteristics between the ejection ports that occurs during the manufacturing process of the inkjet head affects the ink ejection amount and ejection direction of each ejection port, and finally the density of the recorded image. It appears as unevenness and causes deterioration of image quality.

A specific example will be described with reference to FIGS. 9 and 10.

In FIG. 9A, reference numeral 91 is an ink jet head, which is similar to that shown in FIG. 8, but for the sake of simplicity of explanation, it is assumed that it is composed of eight ejection ports 92. . Reference numeral 93 is an ink droplet ejected from the ejection port 92. Usually, it is an ideal state that ink is ejected in a uniform ejection amount in the same direction as shown in FIG. When such ejection is performed, dots having a uniform size are formed on the recording paper as shown in FIG. 9B, and the density without density unevenness as a whole as shown in FIG. 9C. An image with uniform changes is obtained.

On the other hand, as described above, when there are variations in the ejection characteristics among the ejection ports, as shown in FIG. 10A, the size of the ink drop ejected from each ejection port is large. 10B is formed on the recording paper, and the dots are formed on the recording paper. As a result, according to the example shown in FIG. 10B, the area factor 100 is periodically set in the head main scanning direction.
%, There is a white paper part that cannot be satisfied, or conversely, dots are overlapped more than necessary, or a white streak appears in the center of the figure. A collection of dots formed in such a state is shown in FIG.
The density distribution shown in (c) is obtained, and as a result, these phenomena are recognized as density unevenness as far as the eyes of ordinary people can see.

Therefore, the following method is known as a method for eliminating this density unevenness. 11 and 1
2 is a diagram for explaining this method.

According to this method, the multi-head 91 is scanned (scanned) three times to complete the recording in the recording area shown in FIGS. 9 and 10.
Recording is completed in two scans in the pixel area. In this case, the eight ejection openings of the head 91 are the four ejection openings at the top,
The dots that are divided into groups of four lower ejection ports and formed by one scanning of one ejection port are
It is thinned out to about half according to a certain predetermined image data array. Then, during the second scan, dots are formed by the remaining half of the image data, and the recording of the area for 4 pixels is completed. The recording method as described above is hereinafter referred to as a divided recording method. By performing the divided recording method as described above, even when the same recording head as that shown in FIG. 10 is used, the influence on the recording image peculiar to each ejection port is averaged, so that each dot of the recorded image is Is as shown in FIG. 11 (b), and the black and white stripes as shown in FIG. 10 (b) are
It becomes less noticeable. Therefore, the density unevenness is also shown in FIG.
As shown in FIG. 10C, it is relaxed as compared with the case of FIG.

When performing such divided recording, the image data is divided in the first scan and the second scan so as to fill each other according to a certain arrangement, but here,
As an example of the array state (thinning pattern), as shown in FIG. 12, a staggered pattern is used for each vertical and horizontal pixel. Therefore, in the unit recording area (here, in units of 4 pixels), the first scan for recording the zigzag lattice dots (hatched dots in the figure) and the zigzag lattice dots (white circle dots in the figure) Recording is completed by the second scan for recording.

FIGS. 12 (a), 12 (b) and 12 (c) show how recording of a certain area is completed when the zigzag and inverse zigzag patterns are used, respectively.
Similarly to the above, the case where recording is performed using an inkjet head having eight ejection ports is described.

First, in the first scan, the staggered pattern is printed using the lower four ejection ports (FIG. 12A). Next, in the second scan, paper feeding is performed for 4 pixels (1/2 of the ejection opening array length), and an inverse zigzag pattern is recorded (FIG. 12B). Further, in the third scan, the paper is fed by 4 pixels again, and the zigzag pattern is recorded again (FIG. 12C). In this manner, by sequentially feeding the paper in units of 4 pixels and recording in the staggered and reverse zigzag patterns, it is possible to complete the recording area in units of 4 pixels for each scan.

As described above, the same area is divided into two different areas.
By performing recording with an inkjet that is ejected from various types of ejection ports, it is possible to obtain a high-quality image without density unevenness.

As described above, the same area is divided into 2 areas as the divided recording method.
I have explained the configuration that completes the image by recording scans once,
Such a two-division division recording method is often used when it is desired to record a color image quickly, since the absorption capacity is not so low as with plain paper. However, the effect of the divided recording method on the image quality increases as the number of divisions increases, and even when plain paper is desired to achieve high image quality, or when recording media such as coated paper or glossy paper is used. When the device itself is expensive, it is also possible to adopt a method in which the number of pixels to be printed in one scan is further halved and the width of the paper feed scan is set to 2 pixels (1/4 of the ejection port array length). . In this case, since the image is completed by four kinds of ejection ports in the same scanning direction, the recording speed is inferior,
Further, it is possible to obtain a good image with a smooth density change.

In addition, by recording the same area in a plurality of times in this way, an image can be completed while reliably fixing a small amount of ink on an OHP film or the like having low ink absorbency. It is possible to prevent not only the boundary of different colors but also the beading phenomenon in which unabsorbed ink droplets are fixed as a large lump of ink droplets which can be visually recognized on the medium surface due to the surface tension.

As described above, in a printer in which an appropriate recording method is set in advance depending on the recording medium,
In this embodiment, the detected water content (electrical resistance value) is further effectively reflected in this recording method.

The specific printing method of this embodiment based on the recording medium and the state of the water content will be described below.

In this embodiment, the amount of ink ejected onto the recording medium is controlled according to the detected amount of water. Two methods are conceivable as means for controlling the amount of ink ejected onto the recording medium. One is a method of adjusting the amount of ink per droplet ejected from an ejection port, and the other is a method of adjusting the number of dots formed in an image area to be printed.

In the case of ink jet recording, the control method is different depending on the means for ejecting the ink, but when the method is for ejecting the ink by applying thermal energy as in the recording head of the present embodiment, the amount of heat applied is given. In many cases, the discharge amount can also be adjusted by adjusting.

An example of the ejection amount control method in the ink jet system in which film boiling is caused in the ink by applying heat energy and the volume of the bubbles is expanded to eject the ink will be described below.

In this method, the head driving pulse for ejecting one droplet is a double pulse, and the first pulse (hereinafter, preheat pulse) is a second pulse for warming the ink around the bubble formation. (Hereinafter, referred to as a main pulse) is provided to form bubbles and eject ink from the respective bubbles.

FIG. 3 is a waveform diagram showing this double pulse.

As shown in the figure, there is an interval P2 between the preheat pulse (and its pulse width) P1 and the main heat pulse (and its pulse width) P3,
The ejection amount changes according to the width P1 of the preheat pulse, that is, the amount of heating of the ink. Hereinafter, such a discharge amount control method is referred to as PWM control.

Normally, this PWM control is applied to stabilize the ejection amount according to the temperature change of the head. That is, the ejection amount by the main heat pulse P3 is stabilized by modulating the pulse width P1 of the preheat pulse according to the temperature change of the head.

FIGS. 5A and 5B show two types of pulse width tables corresponding to the head temperature. As shown in FIG. 4, the ejection amount has a substantially linear relationship with the head temperature. This PWM control is effective in the region where it is open. In the table shown in FIG. 5A, the discharge amount Va is always
In the table shown in FIG. 5B, the ejection amount Vb is set. Thus, if the temperature can be detected and the discharge amount can be stabilized by setting the table, the discharge amount target value can be set to Va, Vb or another range by changing the contents of the table shown in this figure. Also, it becomes possible to control by the above table conversion. In the present embodiment, the PWM table is set to an appropriate ejection amount (for example, Va) obtained by the water amount detection means (FIG. 5A), and recording is performed with this ejection amount, so that the water amount of the recording medium is changed. Enables appropriate recording according to the requirements.

FIG. 6 shows an appropriate ejection amount table which is determined by the recording mode for each recording medium applicable to this embodiment and the amount of water detected for each recording medium. Each recording mode is independently set for the recording medium. The recording mode shown here is the divided recording method described above.
In other words, plain paper has two-pass (scan) bidirectional recording of 50% for all colors, coated paper has four-pass unidirectional recording of 25% for all colors, and transparent paper (TP, for example, OHP paper) has three colors. Black is 25% at 4% bidirectional recording of 25%
8 pass bidirectional recording, cotton cloth is 8 pass bidirectional recording with 25% of three colors and black is 50% 8 pass bidirectional recording. Here, the color of TP black and cotton cloth is 200
%, The black of cotton cloth is 400%. This is because the black when using TP needs to be emphasized in order to make the black clear when projected, and it is difficult for the cotton cloth to have its original density, and the back surface of the print is as ink-permeated as possible. This is because

As described above, when the appropriate ink ejection amount differs depending on the recording medium and the water content thereof, divided recording is performed by several recording scans, and the amount of each ink droplet, that is, the ejection amount, is controlled by PWM control. It is done in units of pl. Here, more preferably, in order to perform good recording from the recording characteristics depending on the recording medium and the recording quality required according to the recording medium, the divided recording described above is used for each type of recording medium. Control the amount of driving, while
It is desirable to control the ink ejection amount according to the detected water content.

In the example shown in FIG. 6, it is normally 40 pl / dot.
In the recording apparatus that forms an image, the appropriate ejection amount is shown according to the water content of each recording medium. Since the moisture content of plain paper or cotton cloth is easily affected by environmental humidity and the image quality is delicate, the discharge rate for the detection value is finely adjusted as compared with other recording media. Since the amount of water in coated paper is relatively unlikely to be affected by environmental humidity, the discharge amount needs to be adjusted almost at a level. Since the TP is a recording medium that originally has a large amount of water, even if the amount of water is the same as that of another recording medium, the amount of ink can be set to be large. However, since the amount of water tends to increase depending on the environmental humidity, it is necessary to adjust the amount of water in a wide range.

As described above, according to this embodiment, in the ink jet recording apparatus in which an appropriate recording mode is set for each recording medium, means for measuring the water content of the recording medium before recording is provided and the measurement is performed. By setting an appropriate ejection amount according to the value and the type of recording medium and adjusting the ejection amount using the PWM means, it is possible to prevent bleeding on the image at high humidity for each recording medium and to improve the fixability. Becomes

(Second Embodiment) In the second embodiment of the present invention,
Instead of changing the ejection amount according to the water content of the recording medium as in the above embodiment, the print speed or the number of scanning scans is adjusted with respect to the detected water content to prevent the deterioration of print quality.

FIG. 13 is a diagram for explaining a recording method according to the type of recording medium and the amount of water in the second embodiment of the present invention.

As is clear from the figure, the recording method is changed every time the amount of moisture detected in plain paper increases by 10%. 10
% Or less, the two-pass bidirectional recording is 10-2.
At 0%, 4-pass bidirectional printing is performed, and the number of divided prints is increased to print a small amount of ink in several times. When 20% to 30%, four-pass unidirectional printing is performed, and the ink drying time is provided for the return scanning time of the printhead. Furthermore, 30-40%, 40
At -50%, a carriage waiting time of 1 second or 2 seconds is provided for each scan, and the drying time is further increased to cope with image bleeding.

Further, as is apparent from the figure, when another recording medium is used, similarly, the number of divisions of divided recording, the waiting time of the carriage, and the recording method such as unidirectional / bidirectional recording are used to eject ink onto the medium. Control the speed to prevent image bleed.

In the above-described first embodiment, when the water content of the recording medium is large, the ejection amount is made lower than usual in order to prevent image bleeding. On the other hand, in the present embodiment, the number of divisions of the printing scan is increased, or 1 to
By adding a waiting time of 3 seconds and fixing a fixed amount of ink little by little, the bleeding is dealt with.

In this case, according to the above-described first embodiment, the recording time is constant irrespective of the water content, but since the ink ejection amount differs depending on the water content of the medium, a slight density difference may occur in the final printed image. May appear. On the other hand, in the present embodiment, although the recording time varies depending on the water content of the medium, the image after recording can always have the same density. That is, the above two embodiments are not superior or inferior, and both can be used properly for each recording medium depending on the expected image quality and recording time.

As described above, according to the present embodiment, the ink jet printing apparatus is provided with means for measuring the water content of the recording medium before recording, and an appropriate recording method is set according to the measured value and the type of recording medium. However, by adjusting the recording time, it becomes possible to prevent bleeding on the image at high humidity for each recording medium and to improve the fixability.

In addition to the above-described example, when the water content of the print medium is large, the recording speed is reduced to make the interval for drying the ejected ink longer than usual to cause image bleeding. It can also correspond to.
Also in this case, by further controlling the recording speed according to the type of print medium, it is possible to suppress image bleeding and achieve good recording.

Change of the number of divisions by the division recording described above,
The technique for achieving good printing by controlling the standby time for each printing scan and the printing speed is to control the ejection time interval between adjacent pixels or between consecutive scans in all cases. It is possible to reduce image bleeding due to the water content of the print medium.

(Third Embodiment) In the third embodiment of the present invention,
It is equipped with a preheat roller for promoting ink fixing. By heating the recording medium before recording fed by this preheat roller in advance, excess water contained in the medium is evaporated and the ink ejected by recording is dried to fix a good image. In addition to trying to obtain it, it is also possible to prevent bending of the paper after recording. In this case, the present embodiment is characterized in that the heating temperature and the heating time are adjusted depending on the type of the recording medium, and the heating amount of the preheat roller is adjusted in order to prevent image bleeding of different degrees even with the same type of recording medium. Is adjusted by the measured value of the water content of the medium.

FIG. 14 is a perspective view showing the schematic arrangement of the printing apparatus of this embodiment.

When a recording command is input, the recording medium is sent out by the paper feed roller 701. After the water content measuring sensor 708 detects the water content of the recording medium in accordance with the feeding, the recording medium is preheated by the preheat roller 1 according to the water content.
It is heated by 401 and 1402. Then, the recording medium thus preheated is sent to the recording position by the recording head.

In the present embodiment, the heating temperature of the preheat roller is set according to the amount of water detected by the sensor 708, but it is preferable to take into consideration the type of recording medium and the division number of divided recording. That is, the amount of heat required for the ink to be reliably fixed differs depending on the recording medium. For example, the high temperature setting effect is great for plain paper and cotton cloth, but too much heat is applied to coated paper or TP (transparent paper) at one time. If added too much, the material of the medium itself may deteriorate,
This is because contraction may occur. Further, even in the same recording medium, the heating time per unit area increases as the number of divisions of divided printing increases, so that a high temperature is not required when increasing the number of divisions.

In consideration of the above, the set temperature of the preheat roller and the recording mode obtained by the recording medium of this embodiment and the detected water content are shown in FIG.

In this figure, for plain paper or cotton cloth, which is likely to produce an effect by heating, adjustment is made only by setting the temperature of the heat roller. However, in the case of TP that performs 4-division recording, the set temperature is kept at 40 ° C in order to prevent material change due to high temperature heating for a long time, and when the water content is large, the set waiting temperature of the carriage is set. Take action without raising. In addition, the coated paper, which is relatively resistant to environmental humidity, is set so that it is hardly heated.

In this embodiment, as in the second embodiment described above, since the ink ejection amount is not changed, the image density can be kept constant. Further, since any recording medium may be heated by at least a predetermined amount by the preheat roller, the waiting time of the carriage can be suppressed and the throughput can be improved as compared with the second embodiment.

In this embodiment, the heat roller 1401,
Although two heat rollers 1402 are used, the present invention is not limited to this, and a configuration in which only one side is heated may be used. This is because it may be preferable to heat either the recording surface or the non-recording surface depending on the recording medium. Further, it goes without saying that the means for controlling the type of recording medium and the detected amount of water is not limited to the temperature of the heater but may be a method of controlling the number of heaters.

As described above, according to this embodiment,
In inkjet printing, a means for measuring the water content of a recording medium before recording, and setting an appropriate preheat roller heating temperature according to the measured value and the type of recording medium,
By heating the recording medium before recording, it is possible to prevent bleeding on the image at high humidity for each recording medium and to improve the fixability.

(Others) The present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, particularly in the ink jet recording system. The present invention brings about excellent effects in a recording head and a recording apparatus of the type in which the state of ink is changed by the heat energy. This is because such a system can achieve high density recording and high definition recording.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal in a one-to-one correspondence
It is effective because bubbles can be formed inside. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. It is more preferable to make this drive signal into a pulse shape because bubbles can be immediately and appropriately grown and contracted, so that liquid (ink) ejection with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, US Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The structure using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in JP-A-59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus, or the electrical connection to the main body of the apparatus or the ink from the main body of the apparatus by being attached to the main body of the apparatus The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add ejection recovery means of the recording head, preliminary auxiliary means and the like because the effect of the present invention can be further stabilized. Specifically, heating is performed by using a capping unit, a cleaning unit, a pressure or suction unit for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, and a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but it may be either the recording head is integrally formed or a plurality of combinations may be used. The present invention is also extremely effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet system, it is common to control the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change from the solid state of the ink to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as the form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function It may be a form or the like.

[0092]

As described above, according to the present invention,
The water content of the print medium before printing is performed by the ink ejected from the inkjet head can be detected in advance, and the ejection amount in one ejection of the inkjet head is changed according to the detected amount. It becomes possible.

As a result, image bleeding on various recording media can be prevented, and the recorded image can be completed in a good fixing state.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a water content measuring sensor for a recording medium according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a water content of a recording medium and a resistance value.

FIG. 3 is a schematic waveform diagram showing drive pulses for driving a head used in an embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating ejection amount control using the pulse.

5A and 5B are schematic diagrams of a pulse width table used in the ejection amount control.

FIG. 6 is a diagram showing the relationship between the recording mode for each recording medium and the ejection amount according to the water content according to the first embodiment of the present invention.

FIG. 7 is a schematic perspective view of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic diagram showing a discharge port surface of an inkjet head used in the above apparatus.

9A, 9B, and 9C are explanatory diagrams for explaining an ideal recording state of an inkjet printer.

FIGS. 10A, 10B, and 10C are explanatory diagrams illustrating a recording state of an inkjet printer that causes density unevenness.

11 (a), (b) and (c) are explanatory views for explaining divided recording according to an embodiment of the present invention.

12A, 12B and 12C are schematic diagrams showing a recording state by the divided recording.

FIG. 13 is a diagram showing a relationship between a recording medium according to a second embodiment of the present invention and a recording mode according to a water content.

FIG. 14 is a schematic perspective view of an ink jet recording apparatus according to a third embodiment of the invention.

FIG. 15 is a diagram showing the relationship between the recording medium and the heating temperature according to the water content and the recording method in the third embodiment.

[Explanation of symbols]

 91 Inkjet head 92,801 Discharge port 93 Ink droplet 701 Inkjet cartridge 702 Inkjet (recording) head 703 Paper feed roller 704 Auxiliary roller 705 Paper feed roller 706 Carriage 707 Recording medium 708 Moisture amount measurement sensor 709 Ink tank 1301,1302 Electrode 1401 , 1402 preheat roller

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Claims (15)

[Claims] 1. An inkjet printing apparatus that uses an inkjet head to eject ink from the inkjet head onto a print medium for printing, and detects the amount of water in the print medium before receiving the ink ejected from the inkjet head. An ink jet printing apparatus comprising: a water content detecting unit for controlling the printing operation by the ink jet head in the printing in accordance with the water content detected by the water content detecting unit. 2. The inkjet print according to claim 1, wherein the control unit changes the amount of ink ejected by one ejection from the inkjet head according to the detected amount of water. apparatus. 3. The control means further changes the ink amount according to the type of print medium used by the inkjet printing apparatus.
The inkjet printing apparatus described in 1. 4. An ink jet printing apparatus, which uses an ink jet head and ejects ink from the ink jet head onto a print medium for printing, to detect the water content of the print medium before receiving the ink ejected from the ink jet head. And a discharge amount control unit for controlling the amount of ink discharged by one discharge from the inkjet head in the printing according to the moisture amount detected by the moisture amount detecting unit, An ink jet printing apparatus comprising: an ejection number control means for controlling the number of times the ink jet head ejects ink droplets to a predetermined pixel according to the type of medium. 5. The ink jet printing apparatus according to claim 4, wherein the ejection control unit further controls the number of ejections to a predetermined pixel according to the amount of water detected by the water amount detection unit. 6. An inkjet printing apparatus for printing by using an inkjet head to eject ink from the inkjet head onto a print medium, and a main scanning unit for relatively scanning the inkjet head with respect to the print medium, and a predetermined recording. A recording control unit that complementarily prints an area by a predetermined plurality of scans by the main scanning unit, and a water content of the print medium before receiving the ink ejected from the inkjet head. A water content detecting means; and a control means for changing the predetermined number of scanning times for complementary printing by the recording control means in accordance with the water content detected by the water content detecting means. An inkjet printing apparatus characterized by the above. 7. The inkjet printing apparatus according to claim 6, wherein the control unit further changes the predetermined number of times of scanning according to the type of the print medium. 8. An inkjet printing apparatus that uses an inkjet head to eject ink from the inkjet head onto a print medium for printing, and a main scanning unit that relatively scans the inkjet head onto the print medium, and the inkjet head. Water content detecting means for detecting the water content of the print medium before receiving the ink ejected from the printing medium, and the waiting time for each recording scan by the main scanning means according to the water content detected by the water content detecting means. An ink jet printing apparatus comprising: a standby time setting means provided with. 9. The inkjet printing apparatus according to claim 8, wherein the standby time setting unit further sets a standby time for each recording scan according to the type of the print medium. 10. An inkjet printing apparatus that uses an inkjet head and ejects ink from the inkjet head onto a print medium for printing, and a main scanning unit that relatively scans the inkjet head onto the print medium, and the inkjet head. Water content detecting means for detecting the water content of the print medium before receiving the ink ejected from the ink, and control for changing the ejection time interval of the inkjet head according to the water content detected by the water content detecting means An ink jet printing apparatus, characterized by comprising: 11. The ink jet printing apparatus according to claim 10, wherein the control unit further changes the ejection time interval according to the type of the print medium. 12. An ink jet printing apparatus, which uses an ink jet head and ejects ink from the ink jet head onto a print medium for printing, to detect the water content of the print medium before receiving the ink ejected from the ink jet head. And a heating means for heating the print medium before the ink discharged from the inkjet head is received, the print medium having the water content detected by the water content detecting means. An inkjet printing apparatus comprising: a control unit that controls heating by the heating unit according to the amount of water detected by the detection unit. 13. The inkjet printing apparatus according to claim 12, wherein the control unit further controls the heating according to the type of print medium used by the inkjet printing apparatus. 14. An inkjet printing apparatus, which uses an inkjet head and discharges ink from the inkjet head onto a print medium to perform printing, and a carrying unit that carries the print medium, and a carrying path provided by the carrying unit. An inkjet printing apparatus, comprising: a water content detection sensor provided upstream of a head for detecting the water content of a print medium. 15. The ink jet head according to claim 1, wherein a bubble is generated in the ink by utilizing thermal energy and the ink is ejected as the bubble is generated. The inkjet printing apparatus described in 1.