JPH06191142A - Ink jet recording method and apparatus - Google Patents

Abstract

PURPOSE:To eliminate the rough feeling of a highlight part and to enhance resolving power in a low density part by making the temp. of a recording head at the time of the emission of ink different from that of the recording head at the time of the emission of other ink droplet. CONSTITUTION:The recording of one line is performed in such a state that a heater 103 is not driven in the forward operation of a carriage. The temp. and volume of the emitted ink from a recording head are 35 deg.C and 12pl. Next, the heater 103 is driven and the same line is again recorded by the rearward operation of the carriage without feeding paper. The temp. and volume of emitted ink of the recording head at this time are different from those at the time of forward movement and are 55 deg.C and 18 pl. In this recording operations, the dot formed by the ink droplet emitted at the time of the first forward movement becomes a relatively small size d1 and the dot formed by the emitted ink droplet at the time of the rearward operation becomes a relatively large size d2. The dot formed by overlapping emitted ink droplets in the forward and rearward movements of the carriage becomes a size d3.

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 method and an ink jet recording apparatus, and more particularly to an ink jet system gradation recording.

[0002]

2. Description of the Related Art Several methods for recording an image having gradation by an ink jet method are conventionally known.

In these methods, for example, the size of the ejected ink droplet is changed by various means to change the area of the dot formed by the ink droplet (ink droplet diameter modulation method), and the density is different. A method of recording using ink (dark and light ink method), a method of forming a pixel by a collection of a predetermined number of dots, and expressing a gradation by changing the number of dots in this pixel (density pattern method,
(Dither method, etc.), multiple ink droplets are deposited on the same pixel, and the dot area / density is changed according to the number of the deposited ink droplets to express gradation (multi-droplet method).

However, it is generally difficult to largely modulate the ink droplet diameter by the ink jet method. Therefore, it is not possible to perform recording with a wide gradation range by the above-mentioned ink droplet diameter modulation method. Further, the dark and light ink method requires recording heads and ink tanks for inks of different densities, which increases the number of recording heads and the like, which increases the cost of the apparatus and increases the size of the apparatus. There is. Further, the density pattern method has a problem that the resolution cannot be so high because the dots tend to diffuse.

On the other hand, the multi-droplet method is a method capable of recording with relatively high gradation and high resolution. However, in order to express the gradation by the multi-droplet method alone, the individual ink droplets to be ejected must be very minute in view of the relationship between the pixel size and the gradation value, that is, the ink droplet to be ejected. I won't. For example, 16
Recording with 64 gradations with a resolution of pixels / mm (maximum 63
When recording is performed by overlapping one droplet), the required ink droplet size should be about 10 μm in diameter. An inkjet recording head capable of ejecting such minute ink droplets requires extremely fine processing, which makes it difficult to manufacture and extremely high in cost.

Therefore, a method has been proposed in which the multi-droplet method and the density pattern method are combined to record a relatively large number of relatively large droplets. According to this method, it is possible to increase the density of one dot formed by overlapping ejection of ink droplets by the multi-droplet method, and thus, the decrease in resolution by the density pattern method can be suppressed to a small extent. In addition, the recording head can be easily manufactured at low cost.

[0007]

However, when the multi-droplet method and the density pattern method are combined for recording, there are the following problems.

That is, when ink droplets are ejected overlappingly to form dots, the dot density increases as the number of ejected ink droplets increases, but at this time, each ink droplet has the same volume. However, the density does not increase linearly, and the rate of increase in density decreases as the number of dots to be printed increases. Therefore, in order to express a relatively high density, the ejected ink droplets may have a sufficient size, but in this case, the dots are too large to record a low-density image, For example, there is a problem that the resolution is lowered when the highlight portion of the image is recorded, and the image is rough.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is not to have a grainy feeling particularly in a highlight portion and to have a high resolution in a low density portion. An object is to provide an inkjet recording method and an inkjet recording apparatus capable of recording an image.

[0010]

Therefore, according to the present invention,
In an inkjet recording method in which a recording head for ejecting ink is used and a pixel is formed by a plurality of ink droplets ejected from the recording head, at least one ink droplet among the plurality of ink droplets is ejected. The temperature of the recording head is different from the temperature of the recording head when the other ink droplet is ejected.

Further, in an ink jet recording apparatus for recording by using a recording head for ejecting ink and forming a pixel by a plurality of ink droplets ejected from the recording head, the temperature of the recording head is changed. By controlling the temperature changing means and the temperature changing means, the temperature of the recording head at the time of ejecting at least one of the plurality of ink droplets is set to the temperature at the time of ejecting the other ink droplet. And a control unit for changing the temperature of the recording head.

[0012]

According to the above structure, by relatively lowering the temperature of the recording head when, for example, one ink droplet is ejected from among a plurality of ink droplets that form a pixel, the dots formed by this are formed. It can be relatively small. As a result, it becomes possible to form an image of a low density portion with these dots.

[0013]

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

First, the principle of the recording method according to the present invention will be described.

It is generally known that the volume of ink droplets ejected by the ink jet method changes in correlation with the temperature of the recording head. The present inventors have studied using a recording head of a type that ejects ink by generating bubbles due to thermal energy. As a result, the amount of change in the ink droplet volume increases by several% of the ink droplet volume per 1 ° C. of the temperature rise of the recording head. It was about. Therefore, with this volume change alone,
It is difficult to perform gradation recording by the above-described ink droplet diameter modulation method, but by combining this volume change and the multi-droplet method, it is possible to record ink droplets having different volumes in an overlapping manner.

That is, for example, when the maximum number of dots that can be printed in one pixel is two, as shown in FIG. 1, the dots d1 formed by ejection when the print head temperature is relatively low, and the print Three types of dots can be formed: a dot d2 formed by ink droplets ejected when the head temperature is relatively high, and a dot d3 formed by overlapping these. As a result, the density of the dots d1 used for recording in the low density portion can be lowered as compared with the case where recording is performed using ink droplets of the same volume, so that the highlight portion can be recorded with high resolution, and the graininess of the image can be suppressed. it can.

Further, in the method of ejecting a maximum of two ink drops of the same volume, three-valued recording (no dot, one dot, two dots)
However, the method using ink drops when the printhead temperature is low and ink drops when the printhead temperature is high is 4
It is possible to record values (no dots, 1 dot with ink drops at low temperature, 1 dot with ink drops at high temperature, dots with overlapping inks at low and high temperatures) You can record with high quality.

In order to increase the volume of the ink droplet, it is not essential to raise the temperature of the entire recording head, and if the temperature of the ink in the recording head is high, the volume of the ejected ink droplet will increase.

As the ink jet recording head used in the present invention, any one can be used as long as the ejected ink droplet volume changes depending on the temperature change of the recording head, but the volume of the ink droplet according to the change of the recording head temperature can be used. As a method in which the change is relatively large, a method in which bubbles are generated in the ink by thermal energy and the ink is ejected along with the generation of the bubbles is more preferable.

Further, as a method for changing the ink temperature of the recording head, a heating heater or a cooling element is attached to the recording head, and a heating pulse that does not cause ejection to the ejection heater for generating the thermal energy. In addition, any known method can be used as long as the recording head temperature changes efficiently in a short time. However, in order to increase the recording speed and increase the ink temperature in a short time, the above-mentioned heating heater or cooling element may be provided on the same substrate as the substrate on which the ejection heater is provided, or It is more preferable to send a heating pulse to the discharge heater to control the temperature.

In such a case, it is sufficient that only the substrate provided with the discharge heater and the ink in contact with it rises to a predetermined temperature, and according to the experiments by the present inventors, it takes about 0.1 second. The temperature can be raised in a very short time. In this case, since the temperature of the entire recording head has not risen, when heating is stopped, the temperature drops to the temperature before heating in an extremely short time of about 0.1 seconds.

Therefore, for example, in a so-called serial printer, after the carriage is scanned in one direction, the temperature of the print head can be changed in about the time during which the direction is reversed, and the print speed can be reduced without reducing the printing speed. The invention may be implemented.

In addition, even when the entire recording medium is once recorded at the first temperature and then changed at the second temperature by changing the temperature of the recording head, the time required to change the temperature of the recording head is increased. Since it is short, it does not reduce the recording speed.

Recording according to the embodiment of the present invention will be specifically described below.

(Embodiment 1) FIG. 2 is a schematic perspective view of an ink jet recording apparatus according to an embodiment of the present invention.

The apparatus shown in FIG. 2 is composed of yellow, magenta,
Recording head 1 for cyan and black ink
A recording device that includes Y, 1M, 1C, and 1Bk and is capable of full-color recording is shown. Recording heads 1Y, 1M, 1
C and 1 Bk are arranged on the carriage 2. The carriage 2 is slidably engaged with the pair of guide shafts 3 and is connected to a part of the wire 4 stretched by the pulleys 5A and 5B. The pulley 5B is rotated by the driving force of the motor 6. With the above configuration, the recording heads 1Y, 1M, 1C, and 1Bk mounted on the carriage 2 move (also referred to as scanning) along the guide shaft 3, and during this time, the respective ejection ports move to the recording surface of the recording paper. Ink is ejected toward the recording.

The recording paper 10 is sandwiched between the platen roller 7 and a pinch roller (not shown) arranged around the platen roller 7, whereby the recording paper 10 is conveyed in accordance with the rotation of the platen roller. This conveyance and the recording heads 1Y, 1
Recording is sequentially performed on the recording paper 10 by the movement of M, 1C, and 1Bk. The recorded portion of the recording paper 10 is sequentially sent to the upper side of the apparatus as it is conveyed, and when recording is completed, it is ejected to a paper ejection portion such as a paper ejection tray (not shown) by a conveyance roller (not shown). . The platen roller 7 is rotated by the driving force from the paper feed motor 9 transmitted through the gear train 8.

FIG. 3 is a plan view showing a substrate which constitutes each recording head shown in FIG.

Each recording head has 64 ejection ports and an ink path communicating with each ejection port with a density of 16 ejection ports / m.
Arrange by m. Correspondingly, 64 heaters 102 (electrothermal converters) for generating thermal energy are formed in a portion corresponding to the ink path on the substrate 101,
In addition, electrodes 104 for supplying electric power to the respective heaters 102 are formed on the substrate 101. This heater 10
2 is driven at a discharge frequency of 4 kHz. Also, the heater 1
Heaters for heating are formed on both sides where 02 is formed.

The ink used for recording was 20% diethylene glycol, 5% ethyl alcohol, 72% water,
C. I. A composition consisting of Direct Black 154 3% was mixed and dissolved, and then filtered through a filter. The recording medium used for recording was Matte Coat NM paper (manufactured by Mitsubishi Paper Mills).

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

The CPU 100 controls the operation of each part of the apparatus of this embodiment and executes data processing. ROM100A is the above C
The procedure of the process executed by the PU 100 is stored in the RAM 10
0B is used as a work area in the above processing.

The CPU 100 sends drive data and drive control signals to the head driver 1YD (1MD, 1CD, 1Bk).
D), and the recording head 1Y (1M, 1C, 1Bk)
To discharge. Along with this, the motor driver 6A
And 9A to control the rotation of the carriage motors 6 and 9, respectively.

Further, the CPU 100 controls the ink ejection accompanying the movement of the recording head as described above, and also controls the heating heater 103 via the heater driver 103A as will be described later with reference to an embodiment of the present invention. Control heating.

Recording was performed as follows using the apparatus having the above configuration. First, in the forward movement of the carriage 2, recording for one line is performed with the heater 103 for heating not driven (OFF). At this time, the recording head temperature and the ejected ink droplet volume are 35 ° C. and 12 pl, respectively. next,
The heater 103 for heating is driven (ON), and the same line is recorded again by the returning operation of the carriage 2 without feeding the paper.
The recording head temperature and the ejected ink droplet volume at this time are 55 ° C. and 18 pl, respectively, unlike in the forward movement.

In the above recording operation, the dots formed by the ejected ink droplets during the first forward movement are relatively small and become the dots d1 shown in FIG. 1, and the dots formed by the ejected ink droplets during the backward movement are Figure 1
Dot d2. Further, the dots formed by overlapping the ejected ink droplets of each reciprocating direction are the dots d3 in FIG.

As a result, the low density portion in the image can be formed by the dots d1, and the medium density can be formed by the dots d2. Further, the high density portion can be configured by the dot d3 in which the ink drops are superposed. The image recorded in this manner is a good image with less graininess in the highlight portion, high resolution in the low density portion, and good expression of high density.

(Embodiment 2) FIG. 5 is a plan view showing a substrate of a recording head according to this embodiment.

This recording head is the same as that of the first embodiment in the portion such as the ejection port, but is not provided with a heater for heating, and the temperature of the recording head is controlled by using the ejection heater 402.

The method will be described with reference to the discharge heater drive signal shown in FIG. That is, pulse 5 for ejection
In the middle of the timing when 01 is applied, the ejection pulse 5
Five pulses 502 having a pulse width of ⅕ of 01 can be applied as heating pulses, and the temperature of the recording head is controlled by changing the number of these pulses 502.

Needless to say, ink is not ejected even if the pulse 502 is continuously applied.

Using the recording head having such a structure, the number of temperature control pulses is set to 0 in the forward movement and 5 in the backward movement, and an image is recorded using the same apparatus, ink and recording medium as those in the first embodiment. As a result, the same recording head temperature and ejected ink droplet volume as in Example 1 were obtained, and good images could be recorded.

(Embodiment 3) 256 discharge ports, density 16
Recording was performed using a recording head with ejection ports / mm by the same temperature control method as in Example 2 (using 1 or 5 as the number of temperature control pulses). The same ink and recording medium as in Example 1 were used. The temperature and ink drop volume of the recording head used in this example are 36 ° C. and 8 pl when the temperature control pulse number is 1, and 52 ° C. and 12 pl when the temperature control pulse number is 5. In the dot forming method of this example, one pixel (dot) is formed at a maximum of three times, and the number of temperature control pulses is set to 1 at the time of the first scanning and the second scanning for recording one row, and the third time. Recording was performed with the number of temperature control pulses set to 5 during scanning.

In the image recorded in this way, as shown in FIG. 7, the relatively low density portion can be formed by the dots E1, and the graininess in the highlight portion and the resolution in the low density portion are extremely high. It was a good image.

(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 the typical structure and principle thereof, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
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. Due to the growth and contraction of the bubbles, the liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) 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 respective 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 mounted on 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 effects 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 or number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or 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 of the ink from the solid state 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 thermal energy such as ink that is liquefied by applying thermal 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, the ink jet recording apparatus of the present invention may be 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, or a facsimile apparatus having a transmitting / receiving function. It may be a form or the like.

[0054]

As is apparent from the above description, according to the present invention, the temperature of the recording head when ejecting, for example, one ink droplet among a plurality of ink droplets forming a pixel is made relatively low. As a result, the dots formed thereby can be made relatively small. As a result, it becomes possible to form an image of a low density portion with these dots.

As a result, it is possible to eliminate the feeling of graininess in the highlight portion of the recorded image and to improve the resolution of the low density portion.

[Brief description of drawings]

FIG. 1 is a diagram showing the density of dots formed according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 3 is a plan view of a recording head substrate according to an embodiment of the present invention.

4 is a block diagram showing a control configuration of the device shown in FIG.

FIG. 5 is a plan view of a recording head substrate according to another embodiment of the present invention.

FIG. 6 is a waveform diagram showing drive signals for a discharge heater in the other embodiment.

FIG. 7 is a diagram showing the density of dots formed according to still another embodiment of the present invention.

[Explanation of symbols]

 1Y, 1M, 1C, 1Bk Recording head 1YD, 1MD, 1CD, 1BkD Head driver 2 Carriage 3 Guide shaft 4 Wire 5A, 5B Pulley 6 Carriage motor 7 Platen roller 9 Paper feed motor 10 Recording paper 100 CPU 100A ROM 100B RAM 101, 401 substrate 102, 402 discharge heater 103 heating (temperature control) heater 103A heater driver 104, 404 electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B41J 2/205 9012-2C B41J 3/04 103 X

Claims (6)

[Claims] 1. An ink jet recording method for forming a pixel by a plurality of ink droplets ejected from the recording head, wherein at least one ink droplet among the plurality of ink droplets is used. An ink jet recording method, wherein the temperature of the recording head when ejecting the ink is different from the temperature of the recording head when ejecting the other ink droplet. 2. Each of the plurality of ink droplets is ejected by each of a plurality of scans of the recording head,
2. The ink jet recording method according to claim 1, wherein the temperature of the recording head is set to a temperature different from that of the other scanning when at least one of the plurality of scannings is performed. 3. The ink jet recording according to claim 1, wherein the recording head uses the thermal energy to generate bubbles in the ink and ejects the ink in association with the generation of the bubbles. Method. 4. An ink jet recording apparatus which uses a recording head for ejecting ink, and comprises a plurality of ink droplets ejected from the recording head to form a pixel for recording, for changing the temperature of the recording head. By controlling the temperature changing means and the temperature changing means, the temperature of the recording head when ejecting at least one ink droplet among the plurality of ink droplets is set to the temperature when ejecting another ink droplet. An ink jet recording apparatus comprising: a control unit for changing the temperature of the recording head. 5. Each of the plurality of ink droplets is ejected by each of a plurality of scans of the recording head,
The ink jet recording apparatus according to claim 4, wherein the temperature of the recording head is set to a temperature different from that of the other scanning during at least one of the plurality of scans. 6. The ink jet recording according to claim 4, wherein the recording head uses the thermal energy to generate bubbles in the ink and ejects the ink in association with the generation of the bubbles. apparatus.