JPH06115074A - Printing device - Google Patents

Abstract

PURPOSE:To prevent an image from deteriorating qualitatively by eliminating a temperature difference in a printing head between an occasion when the entire printing head is used simultaneously and an occasion when its divided parts are used one by one, and correcting density irregularities effectively based on a correction table obtained when the entire head is used, even if it is required to use the divided head parts as is the case with a diminished copy. CONSTITUTION:A printing head 101 is heated using heaters 102, 103, 107 respectively which are arranged to the right of the center and to the left of the center of the printing head 101. Further, the heaters 102, 103, 107 are independently driven by heater drivers 104a, 104b, 104c, and the use of the entire printing head or its divided parts is instructed by a mode switching means 105. In addition, the heater driver is selectively driven using a control means 106 upon the instruction of the mode switching means 105.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus, particularly a printing apparatus for printing by heat, for example, an ink which is one of the ink jet systems is heated to cause foaming, and by the force of bubbles generated at that time. The present invention relates to a printing apparatus using a bubble jet system (hereinafter referred to as BJ system) head for ejecting ink or a thermal head used in a thermal transfer system.

[0002]

2. Description of the Related Art In recent years, a printing apparatus using a BJ type print head (hereinafter referred to as an ink jet type) which heats and foams ink and ejects the ink by the force of bubbles generated at that time A conventional example) has been devised.

A print head of this type is, for example, 128
The individual ink ejection ports are arranged in a straight line, and an image is formed by moving the print head in a direction perpendicular to the ejection port array.

However, the discharge amount from each ink discharge port is not uniform, and therefore, when a halftone image such as a photograph is printed instead of a line drawing such as characters, density unevenness occurs and image quality is deteriorated. Will be deteriorated.

Next, correction of density unevenness in the conventional example will be described with reference to FIG. The following method is used as a correction method for improving the density unevenness. FIG. 2 is a diagram showing an image structure of the present invention and a conventional example.

In order to improve this density unevenness, conventionally, as shown in FIG. 2, a shading correction table 202 is provided, and the image data sent from the image data generation unit 201 is corrected. There is.

The correction table 202 is created as follows. That is, the image data generation unit 201
When uniform data such as 80H is sent from the above, the correction table 202 is passed through without correction, and printing is performed, a pattern having density unevenness is printed in the ejection row direction.

After that, when the printed pattern is read by using a reading sensor, the read data becomes non-uniform as shown in FIG. 3 because the print pattern has density unevenness.

FIG. 3 is a diagram showing correction of print density unevenness in the present invention and the conventional example. In FIG. 3, a difference ΔD (n) between the average value Dave of the density data at that time and the density data D (n) of each pixel number is calculated and used as a correction value,
It is stored in the correction table 202.

Next, with respect to the image data actually sent from the image data generator 201, the correction data ΔD
By correcting using (n), density unevenness is reduced.

Next, the conventional equal-magnification and reduction copy method will be described with reference to FIG. FIG. 4 is a diagram showing the relationship between the read sensor and the print head at the same size and reduced copy in the present invention and the conventional example.

First, the same size copying will be described. Figure 4
As shown in (a), in order to simplify the image processing circuit, as the normal reading sensor 401, a sensor having the same number of pixels as the print head 402 is used.
And the print head 402 are simultaneously driven in synchronization with each other, and the pixels of the read sensor 401 and the print head 402 are made to correspond to each other in a one-to-one manner, so that the same size copying is performed.

Next, a reduction copy method will be described. As shown in FIG. 4B, first, the print head 402
The number of pixels used by the reading sensor 401 is determined so that the number of pixels is reduced as a result of reduction by using the first half of the above, and the reading operation and the printing operation are performed at the same time.

Next, the reading sensor 401 is moved to a position where the next pixel after the last reading can be read, and the latter half of the print head is used. The number of pixels used by the reading sensor 401 is determined, and the reading operation and the printing operation are performed simultaneously. After that, the non-printed material (paper) is moved by the print head 402. Reduction copying is performed by repeating these series of operations.

[0015]

However, in the above-described conventional example, the temperature of the vicinity of the ejection port that ejected the ink rises due to the heat generated by the heating means for ejecting the ink, and the ejection port that does not eject the ink rises. The temperature will not rise in the vicinity.

FIG. 5 is a diagram showing the temperature distribution of the head at the time of printing, (a) shows the case where all 128 nozzles are used at the same time, and (b) shows the reduction in the conventional example. This is a case where copying is performed and printing is performed using nozzles 1 to 64. Further, (c) is a temperature distribution when the reduction copying is performed similarly to the case of using the present invention and printing is performed by using nozzles 1 to 64.

In FIG. 5, in the above-mentioned conventional example, the head temperature distribution is as shown in FIG. 5A because the entire head is used at the same time when printing a pattern for correcting density unevenness during printing. ing.

However, when the heads are divided and used as in the case of reduction, the temperature distribution of the heads becomes as shown in FIG. 5 (b). Comparing (a) and (b) of FIG. 5, in the vicinity of the center of the print head, in the case of (b) as well, the temperature is higher than that of (a), despite the vicinity of the ejection outlet that is printing. It's getting low. This is because in the case of (a), the heat from the heating means of the ejection ports ejecting the 65th and subsequent inks is transmitted and the temperature rises, whereas in the case of (b), it is 6
This is because the fifth and subsequent prints are not printed, and the heat for that amount is not transmitted.

Further, in this type of print head, when the temperature of the head itself rises, the ejection amount tends to increase due to a change in ink viscosity and thermal expansion.

Therefore, as described above, a temperature difference occurs between the time when the entire head is used and the time when the head is divided, and the temperature changes even at the same ejection port for printing, the ink ejection amount changes, and the density at the time of printing is changed. There was a problem that the appearance of unevenness would change.

Therefore, at the time of reduction copying, even if the density unevenness correction is performed using the correction table obtained for the pattern using the entire head, the correction is incomplete and the image quality deteriorates.

The present invention has been made to solve the above problems, and eliminates the temperature difference between the time when the entire print head is used at the same time and the time when the print head is divided and used as a reduced copy head. Even when dividing and using, the density unevenness correction using the correction table obtained when the entire head is used is effective, and it is an object to prevent deterioration of image quality.

[0023]

Therefore, according to the first aspect of the present invention, a print head having a plurality of printing elements arranged in parallel and printing by heat, and a central portion of the print head near the right end thereof. A heater for heating the print head, a heater driver for independently driving the heater, and the print head, all of which are provided at the same time or dividedly. The above-mentioned problem is solved by a printing device characterized by comprising a mode switching means for instructing whether or not, and a control means for selectively driving the heater driver according to an instruction from the mode switching means. It is intended to achieve the above object.

Further, according to a second aspect of the present invention, the above-mentioned problem is solved by the printing apparatus according to the first aspect, characterized in that the temperature sensor is arranged in the central portion of the print head.
It is intended to achieve the above object.

Further, according to a third aspect of the present invention, the printing head ejects ink by heat, and the printing apparatus according to the first or second aspect solves the above problems and achieves the above object. Is what you are trying to do.

[0026]

In the printer according to the first aspect of the present invention, the print head is heated by the heaters arranged near the center right end and the center left end of the print head, and the heater is independently driven by the heater driver. It is driven and the mode switching means instructs whether the print heads are all used at the same time or divided. Then, the controller selectively drives the heater driver according to an instruction from the mode switching unit.

In the printing apparatus according to the second aspect of the present invention, the temperature of the central portion of the print head is detected by the temperature sensor provided in the central portion of the print head.
Further, the printer according to claim 3 of the present invention ejects ink by heat according to claim 2 or 3.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a printer according to a first embodiment of the present invention.

In FIG. 1, 101 is a BJ type print head, 102, 103 and 107 are planar sub-heaters for heating the heads respectively, and 104a, 104b and 104c are for driving the sub-heaters 102, 103 and 107, respectively. A driver, 105 is a mode switching means for switching whether to use the entire head or divided heads, and 106 is a control means for selectively driving the drivers 104a to 104c according to an instruction from the mode switching means 105. 108 is a temperature sensor.

In the first embodiment, 101 is a BJ type head having 128 nozzles and a nozzle pitch of 63.5 μm.

The ink discharge amount of the print head of this system is
Each nozzle (ink ejection port) is different, and therefore, when printing a halftone image such as a photograph instead of a line drawing such as characters, unevenness is seen and the image quality is deteriorated.

Next, the density unevenness correction of the first embodiment will be described. The correction method for improving this unevenness is the same as that of the conventional example, but will be redundantly described below with reference to FIG.

In order to improve this density unevenness, the shading correction table 20 has the structure shown in FIG.
2 is provided, and the image data sent from the image data generation unit 201 is corrected.

The correction table 202 is created as follows. That is, the data generator 201
To send uniform data of 80H from the correction table 2
When No. 02 is passed through without correction and printing is performed, a pattern having unevenness in the ejection port array direction is printed.

After that, when the printed pattern is read by using the reading sensor, the read data becomes uneven as shown in FIG. 3 because the print pattern has unevenness. In FIG. 3, the average value Dav of the density data at that time
difference ΔD between e and the density data D (n) of each pixel number
(N) is calculated and used as a correction value, and the correction table 20
Remember in 2.

Next, with respect to the image data actually sent from the image data generator 201, the correction data ΔD
Correct using (n).

Next, the same size copying operation of the first embodiment will be described with reference to FIG. With this type of head,
Further, a copying operation in the case of having a copying machine function by integrating with a reading device will be described.

As shown in FIG. 4A used in the conventional example, the reading sensor 4 is used in order to simplify the image processing circuit.
As 01, one having the same number of pixels as the print head 402 is used.

First, the case of equal size copying will be described.

As shown in FIG. 4A, the reading sensor 4
01 and the print head 402 are driven at the same time, and the sensor 401
The same size copying is performed by associating each pixel with the print nozzle of the head 402 in a one-to-one correspondence.

At this time, the density unevenness correction using the shading correction table 202 (FIG. 2) described above is performed to correct the density unevenness due to the difference in the ejection amount of the print nozzles and prevent the deterioration of the image quality.

Next, the reduction copy operation of the first embodiment will be described with reference to FIG. In order to perform reduction copying with a device having such a configuration, as shown in FIG. 4B, first, the first half of the print head 402 is used, and reading is performed so that the number of pixels is reduced as a result. The number of pixels used by the sensor 401 is determined. For example, as shown in the figure, in the case of 70% reduction, 64 ÷ 0.
The reading sensor 401 for 91 pixels obtained by 7 = 91 is used. Then, the reading sensor 401 and the print head 4
02 are driven simultaneously.

Next, the reading sensor is moved to a position where the next pixel after the last reading can be read, for example, a distance of 91 pixels in the case of 70% reduction, and the second half of the print head 402 is used. Like the reading sensor 40
1 and the print head 402 are simultaneously driven. After that, the non-printed material (paper) is moved by the print head, and the operation is repeated from the first operation.

Next, the density unevenness correcting method in the reduced copy will be described with reference to FIGS. 1 and 2. First, the density unevenness correction using the shading correction table 202 (FIG. 2) described above is performed, and the density unevenness is also corrected in the reduction copy operation by selectively driving each of the sub-heaters 102 and 103 in FIG. It is possible to prevent deterioration of image quality.

First, the driving method of each of the sub-heaters 102 and 103 will be described. In the reduction copy mode, the head is divided and used as described above by the mode switching means. At this time, the control means 106 receives a signal from the mode switching means 105, and when the heads 1 to 64 of the head 101 are used, printing is performed while applying a DC voltage to turn on the sub heater 103. The heater driver 104b is controlled to perform.

Further, 65 to 128 of the head 101
The heater driver 104a is controlled so that printing is performed while applying a DC voltage to turn on the sub-heater 102 when printing up to No.

While controlling as described above, the head 101
FIG. 5C shows the temperature distribution of the head when printing Nos. 1 to 64. As can be seen by comparing with FIGS. 5A and 5B described above, in the portion where the temperature is lower than that in FIG.
In, the temperature reached the same level as (a). As a result, it is possible to prevent image deterioration during reduction copying.

Next, another driving method of the sub-heater when the head temperature is low in the first embodiment will be described with reference to FIG. When the environmental temperature is low, the head temperature is low, and when normal ink ejection cannot be expected, the sub heater is turned on to raise the head temperature. In the first embodiment, when the temperature is lower than 25 ° C., the sub heaters 102, 1
03 and 107 are kept ON until each temperature reaches 25 ° C. The amount of heat generated by the sub-heater 107 is about twice that of the sub-heaters 102 and 103. The temperature of the head is recognized by the output of the temperature sensor 108.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be explained. FIG. 6 is a block diagram of a printer according to the second embodiment of the present invention.

In FIG. 6, reference numerals 609 and 610 denote pulse waveform generating means, 601 denotes a BJ type print head,
Reference numerals 602, 603, and 607 denote planar sub-heaters for heating the head, 604a and 604b denote drivers for driving the sub-heaters 602 and 603, respectively.
Reference numeral 5 is a mode switching means for switching between use of the entire head or divided use, 606 is a control means for selectively driving the driver 604 according to an instruction from the mode switching means 605, and 608 is a temperature sensor.

The pulse waveform generation means 609 and 610 are controlled by the output of the control means 606 to output or not output the pulse waveform.

Next, a method of driving the sub heaters 602 and 603 will be described. In the reduction copy mode, the head is divided and used by the mode switching means 605 as described above. At this time, the control means 606 receives a signal from the mode switching means 605 and receives the head 60.
When 1 to 64 of 1 are used, the pulse waveform generating means 61 is used to turn on the sub heater 603.
For 0, printing is performed while controlling to output a pulse waveform.

Further, the heads 601 65 to 128
In order to turn on the sub-heater 602 at the time of printing the numbers up to, the printing is performed while controlling the pulse waveform generation means 609 to output a pulse-shaped waveform.

The state of the temperature distribution of the print head when controlled in this way is the same as that shown in FIG. 5 (c). That is, as can be seen from comparison with FIGS. 5A and 5B, in the portion where the temperature is lower than that in FIG. The temperature has reached a certain level. As a result, it is possible to prevent image deterioration during reduction copying.

In the first embodiment, since the sub-heater is driven by the DC voltage, if the heater capacity is not optimized, there is a possibility that the temperature becomes higher than a predetermined temperature when turned on during printing. is there.

On the other hand, in the second embodiment, in order to drive the sub-heater with a pulsed waveform, the pulse width is optimized so that a predetermined temperature can be obtained. Further, it is possible to detect the temperature immediately before the printing operation by the output of the temperature sensor 608 and change the pulse width accordingly.

Next, the third embodiment of the present invention will be described with reference to FIG.
Will be explained. FIG. 7 is a block diagram of a printer according to the third embodiment of the present invention.

In FIG. 7, 711 is a temperature sensor, and 70
Reference numerals 9 and 910 denote pulse waveform generating means, and 701 denotes B.
J-type print heads 702, 703, and 707 are planar sub-heaters for heating the heads 704a and 704b, respectively.
Is a driver for driving the sub-heaters 702 and 703, and 705 is a mode switching means for switching whether to use the entire head or to divide the head.
Reference numeral 6 denotes a control means for selectively driving the driver 704 according to an instruction from the mode switching means 705, 708
Is a temperature sensor.

The temperature sensor 711 is a sensor for detecting the temperature of the central portion of the head, and 708 is a sensor for detecting the temperature of both end portions of the head.

The pulse waveform generation means 709, 710
Is controlled by the output of the control means 706 whether or not to output a pulse-like waveform.

Next, the driving method of each of the sub-heaters 702 and 703 will be described with reference to FIG. In the reduction copy mode, the head is divided and used by the mode switching means 705 as described above. At this time, the control means 706 receives a signal from the mode switching means 705, and when the heads 701 of Nos. 1 to 64 are used, the control means 706 instructs the pulse waveform generation means 710 to turn on the sub heater 703. , Printing is performed while controlling to output a pulse waveform.

However, at this time, if the output of the temperature sensor 711 exceeds 40 ° C., the control means 705 causes the pulse waveform generation means 710 to stop the output of the pulsed waveform.

Further, 65 to 128 of the head 701
In order to turn on the sub-heater 702 at the time of printing the numbers up to, the printing is performed while controlling the pulse waveform generation means 709 so as to output a pulse waveform.

However, similarly to the above, if the output of the temperature sensor 711 becomes 40 ° C. or more at this time, the control means 705 causes the pulse waveform generation means 710 to stop the output of the pulsed waveform.

The state of the temperature distribution of the head when controlled in this way is the same as in FIG. 5 (c). That is, as can be seen from comparison with FIGS. 5A and 5B,
In the portion where the temperature is lower than that in (a) while printing is performed in (b), the temperature reaches the same level as in (a) in (c). As a result, it is possible to prevent image deterioration during reduction copying.

In the first and second embodiments, the heater capacity and pulse width must be optimized in order to constantly drive the sub-heater with DC voltage or pulse waveform during printing. There was a risk that the temperature would rise above the predetermined temperature.

On the other hand, in the third embodiment, it is possible to prevent the head temperature from rising above a predetermined level because the sub heater is driven while monitoring the temperature in the vicinity of the central portion of the head.

In the present invention, printing includes recording not only characters but also images.

The present invention, in particular, in an ink jet recording apparatus, is provided with a means for generating thermal energy as energy used for ejecting ink, and recording by a system in which the thermal energy causes a change in ink state. In a head and a recording device, it has an excellent effect. This is because such a system can achieve high density recording and high detail recording.

Regarding the typical structure and principle of this, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, the system is arranged so as to correspond to the sheet or flow path holding the liquid (ink). By applying at least one drive signal to the electrothermal converter, which corresponds to the recorded information and causes a rapid temperature rise exceeding nucleate boiling, thermal energy is generated in the electrothermal converter, and the heat of the recording head is generated. This is effective because the film is boiled on the working surface, and as a result, bubbles can be formed in the liquid (ink) in one-to-one correspondence with this drive signal. The liquid (ink) is ejected through the ejection openings by the growth and contraction of the bubbles 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, U.S. Pat. Nos. 4,463,359 and 4,345 are used.
Those as described in the '262 patent are suitable. Further excellent recording can be performed by adopting the conditions described in US Pat. No. 4,313,244 of the invention relating to the rate of temperature rise on the heat acting surface.

As the constitution of the recording head, in addition to the combination constitution of the ejection 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, The configuration using US Pat. No. 4,558,333 and US Pat. No. 4,459,600 which disclose the configuration in which the heat acting portion is arranged in the bending region is also effective 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 an electrothermal conversion pair for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 59-138461, which discloses a configuration corresponding to the ejection portion.

Further, although the serial type ink jet recording apparatus is shown in the embodiment, the present invention can be effectively applied to a full line type recording head having a length corresponding to the maximum recordable width. As a full-line type recording head, by a combination of a plurality of recording heads as disclosed in the above-mentioned specification, either a configuration that satisfies the length or a configuration as one recording head integrally formed is used. Although good, the present invention can more effectively exhibit the above-mentioned effects.

Further, it is preferable to add a recovery means for the recording head and a preliminary auxiliary means provided as a constitution of the ink jet recording apparatus of the present invention because the effect of the present invention can be further stabilized. Specific examples thereof include capping means, cleaning means, pressurization or suction means, an electrothermal converter or a heating element other than this, a preheating means for the recording head, and a recording head for the recording head. It is also effective to perform a stable recording by performing a preliminary discharge mode in which another discharge is performed.

Regarding the type and the number of the recording heads to be mounted, for example, a single color ink and one recording head are provided, and a plurality of inks having different recording colors and densities are supported. A plurality of heads may be provided, and any combination may be effective. The present invention is effective not only as a recording mode of black or the like as a recording mode of the recording apparatus but also in a full-color recording mode of different colors or mixed colors.

In the above-described embodiments of the present invention, the ink is described as a liquid, but it is an ink that solidifies at room temperature or lower and softens or melts at room temperature, or the above-mentioned ink. In the inkjet, it is common to control the temperature of the ink itself in the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is in a stable ejection range. Anything can be used. In addition, in order to prevent temperature rise due to heat energy, ink that is positively used as energy for phase change from solid state to liquid state, or ink that solidifies when left standing for the purpose of preventing ink evaporation is used. In any case, the thermal energy such as the one that the ink is liquefied by applying the thermal energy according to the recording signal and ejected as an ink liquid, or the one that has already started to solidify when it reaches the recording medium. The use of an ink having the property of liquefying for the first time is also applicable to the present invention. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

Further, the present invention is an ink jet method such as a piezo jet method in which electricity is converted into force to eject ink, and a recording head in which a recording head is disposed in non-contact with a recording medium and ink is ejected to perform recording. Is effective in.

In addition, as a form of the recording apparatus of the present invention, a copying apparatus which is integrally or separately provided as an output terminal of information processing equipment such as the word processor and the computer as described above, or a copying apparatus which is combined with a scanner or the like, Further, it may be in the form of a facsimile machine having a transmission / reception function.

[0078]

As described above, according to the present invention, when the print heads are divided and used, when the right half head is used for printing, the heater near the left end of the central portion is turned on and the left half head is printed. When it is used for printing, by turning on the heater near the right end of the central part, the temperature difference between the heads when the entire print head is used at the same time and when the print head is divided and used is eliminated, and the heads are divided and used as in reduced copying. Even at this time, the density unevenness correction using the correction table obtained when the entire head is used is effective, and the deterioration of the image quality can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a printer according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an image structure of the present invention and a conventional example.

FIG. 3 is a diagram showing print density unevenness in the present invention and a conventional example.

FIG. 4 is a diagram showing a relationship between a reading sensor and a print head at the same size and reduced copy in the present invention and the conventional example.

FIG. 5 is a diagram showing a temperature distribution of the head when printing is performed.

FIG. 6 is a configuration diagram of a printer according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a printer according to a third embodiment of the present invention.

[Explanation of symbols]

101, 601, 701 Print heads 102, 103, 107, 602, 603, 607, 7
02, 703, 707 heater 105, 605, 705 mode switching means 106, 606, 706 control means 107, 607, 707 heaters 108, 608, 708, 711 temperature sensor 201 image data generation unit 202 shading correction table 203 binarization processing Part 401 reading sensor

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

Claims (3)

[Claims] 1. A print head, which is arranged in parallel and has a plurality of printing elements for performing printing by heat, and a print head, which is arranged near the center right end and near the center left end of the print head, respectively. A heater for heating, a heater driver for independently driving the heater, a mode switching unit for instructing whether the print heads are all used simultaneously or dividedly, and an instruction from the mode switching unit. And a control unit that selectively drives the heater driver. 2. A printer according to claim 1, wherein a temperature sensor is arranged at the center of the print head. 3. The printer according to claim 1, wherein the print head ejects ink by heat.