JP2006192597A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable countermeasure against an increase in the temperature of a head in a form using a head capable of discharging ink and a processing liquid from the same chip. <P>SOLUTION: To perform recording by using a head capable of discharging ink and a processing liquid from the same chip, the inkjet recording device detects the temperature of the chip and varies the temperature of the chip by controlling the discharge of the processing liquid in accordance with the result of detection. When the temperature of the chip is high for example, the device reduces the discharge quantity of the processing liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a temperature control method for an ink jet head, and more particularly to temperature control when using a head capable of ejecting ink and processing liquid (recordability improving liquid) from the same chip. Further, the present invention relates to a temperature rise countermeasure in a long head constituted by connecting such chips and having a large number of ink discharge ports arranged over a relatively wide range, a so-called full multi-type head.

  Printing devices used in printers, copiers, etc., or printing devices used as output devices such as composite electronic devices and workstations including computers and word processors are used for recording materials such as paper and plastic thin plates based on print information. An image (including characters and symbols) is printed. Such printing apparatuses can be classified into an ink jet type, a wire dot type, a thermal type, a laser beam type, and the like according to a printing method.

  In a so-called serial type printing apparatus that performs a printing operation while performing main scanning in a direction crossing the conveyance direction (sub-scanning direction) of the recording material, an image is printed by a printing means (print head) that moves along the recording material. By repeating the process of forming and feeding a predetermined amount of paper each time the printing operation for one main scanning is completed, and then performing the printing operation in the next main scanning on the recording material stopped again. Printing is performed on the entire recording material.

  Patent Document 1 discloses a head configuration capable of discharging a recording performance improving liquid on the same chip. Here, the recording property improving liquid helps fix the ejected ink on the paper surface, prevents bleeding between different color inks, and as a result, improves printing quality. Further, the water resistance of the printed matter is simultaneously improved by using the recording property improving liquid.

  On the other hand, in a line type printing apparatus that involves only the sub-scanning movement in the conveyance direction of the recording material during the printing operation, the recording material is set at a predetermined position and the printing operation for one line is performed continuously. By printing a certain amount of paper, the entire recording material is printed.

  Among the various types of printing apparatuses, the ink jet printing apparatus (inkjet recording apparatus) performs printing by ejecting ink from a print head as a printing means to a recording material, and the print head can be easily downsized. High-definition images can be formed at high speed, so-called plain paper can be printed without the need for special processing, so the running cost is low, and because it is a non-impact method, noise is low, There are advantages such as being easy to adopt a configuration for forming a color image using multicolored inks.

  A line printer using a so-called full multi-type print head in which a large number of inkjet print elements and nozzles (ink discharge ports) are arranged in a direction orthogonal to the recording material conveyance direction is used for image formation. Further speeding is possible, and the possibility as a printer for on-demand printing whose needs are increasing is drawing attention.

  On-demand printing is different from printing in units of several million copies like conventional newspapers and magazines, and printing speeds of 100,000 sheets per hour are not required, but labor saving is desired. A full multi-type line printer is inferior in printing speed compared to conventional offset printing machines, but it eliminates the need for making a printing plate and can save labor. It is optimal for on-demand printing because it can be performed in a short time. In such a full-line type head intended for high-speed printing, it is effective from the viewpoint of providing the recording property improving liquid to obtain an image quality equivalent to offset printing.

  The full multi-type line printer used for such on-demand printing has a resolution of 600 × 600 dpi (dots / inch) for a monochrome color printed document such as text, and a full color image such as a photograph. Is required to print at a high resolution of 1200 × 1200 dpi or more on an A3-sized recording material at 30 pages or more per minute.

  On the other hand, there are cases where images taken with a digital camera or the like are output in an L size as in the past, and there are cases where images are printed on small media such as postcards. It can be said that there are very many.

  However, in the full multi-type printer, it has been difficult to process the discharge ports and the inkjet print elements provided over the entire width of the printing region without any defects. For example, in a full multi-printer that performs photo-like output on large format paper such as materials output in offices, etc., about 14,000 discharge ports (recording width of about 280 mm) are required to print on A3 paper at 1200 dpi. It is. It is difficult in terms of the manufacturing process to process all the inkjet print elements corresponding to such a large number of discharge ports without any single defect. Even if it can be manufactured, the yield rate is low and the manufacturing cost is enormous.

Therefore, in a line printer type ink jet recording apparatus using a full multi-type print head, a print head that is elongated by arranging a plurality of relatively inexpensive short chips used in a serial type with high accuracy, so-called An apparatus realized by using a connecting head has been devised. In this case, it is possible to configure a connection head more suitable for high-speed printing by connecting short chips capable of discharging the recording property improving liquid at the same time (Patent Document 2).
Japanese Patent Laid-Open No. 10-278303 JP 2004-268326 A JP 2002-347223 A Japanese Patent Laid-Open No. 2003-112428

  However, in the case of a head classified as thermal ink jet, a head of about 0.25 to 1 inch (hereinafter referred to as a short chip) used in a serial printer has a large difference in temperature distribution in the head. Does not occur (that is, the temperature in the head becomes uniform). On the other hand, when the length is increased, a large temperature distribution is generated in the head depending on the image to be printed. Furthermore, it is possible to easily create a difference in temperature between the chips depending on the image to be printed in the connection head that is elongated by connecting short chips.

  In the first place, thermal ink jet heads are made of a material with high thermal conductivity, such as a silicon substrate, so if the head size is small, some of the generated heat will be instantly diffused into the head. The entire temperature becomes uniform. When the head becomes longer, it becomes difficult to make the temperature of the head uniform only by the diffusion of heat, and a temperature component is generated in the head. In the thermal ink jet head, when the temperature rises, the discharge amount increases accordingly, causing density unevenness in the printed matter.

  As a countermeasure for the temperature problem of thermal ink jet, Patent Document 3 and Patent Document 4 detect a partial temperature of the head, turn on a sub-heater mounted in the head in advance, and increase the head temperature, A method is disclosed in which an ejection signal that does not eject ink is applied to the head to make the temperature of the entire head uniform.

  However, in the case of using a head capable of ejecting both the ink and the recording property improving liquid from the same chip, it is preferable that a countermeasure for raising the temperature by a method different from the method disclosed in the above document is suitable. Found.

  The present invention is a recording apparatus using a head capable of ejecting ink and processing liquid (recordability improving liquid) from the same chip, in accordance with information from the detection means for detecting the temperature of the chip. And a means for changing the temperature of the chip by controlling the discharge of the processing liquid. Here, it is preferable to use a connection head constituted by connecting a plurality of the chips as the head.

  Here, as an example of processing liquid control, when the chip temperature is high, it is preferable to reduce the chip temperature by reducing the discharge amount of the processing liquid.

  In the present specification, “print” is not only formed when significant information such as characters and figures is formed, but also manifested so that human beings can perceive visually. Regardless of whether or not, a case where an image, a pattern, a pattern, or the like is widely formed on a recording material or a medium is processed.

  In addition, “recording material” refers to not only paper used in general ink jet recording apparatuses, but also materials that can accept ink ejected by a head, such as cloth, plastic film, metal plate, and the like. And

  Further, “ink” should be interpreted widely as the definition of “print” above, and is applied to a recording material to form an image, a pattern, a pattern, etc., or to process the recording material. Shall refer to the liquid that can be made.

  According to the present invention, in a head capable of ejecting ink and processing liquid (recording performance improving liquid) from the same chip, the temperature of the chip is detected by detecting the temperature of the chip and changing the discharge condition of the processing liquid based on the detected information. Thus, density unevenness on the recording medium caused by fluctuations in the ejection amount accompanying temperature rise can be prevented. Further, by changing this control depending on the type of recording medium, it is possible to obtain a higher quality image.

  FIG. 8 shows a system configuration diagram of an inkjet printer applicable in the present invention.

  In FIG. 8, 801 is a CPU that controls the entire system, 802 is a ROM in which a software program for controlling the system is written, 803 is a conveyance unit that conveys a recording material (paper, OHP film, etc.), and 804 is a head recovery. 805 is a carriage unit that scans the head, 806 is a head, 807 is a drive circuit that controls ejection of the head, 808 is a binarization circuit that converts an image to be recorded into ejection data (halftone processing, etc.) 809) corresponds to an image processing unit that performs color separation on a recorded image, for example, in the case of a color image. Reference numeral 810 denotes a processing liquid discharge controller necessary for the present invention. Reference numeral 811 denotes a head temperature detection unit that detects an output from a temperature sensor (for example, a diode sensor is generally used) mounted at several locations of the head (the number varies depending on the configuration of the head). 801 is analyzed, and a discharge control condition of the processing liquid is determined at 810.

  Here, even if nozzles (ink discharge ports) are physically present, not all nozzles are used, the nozzles used for image formation are determined, and the print data necessary for the nozzles is driven to 807. Transferred to the circuit.

  Hereinafter, the present invention will be described specifically by way of examples.

  First, as a first embodiment, a bubble jet (registered trademark) head is used as a head for ejecting ink, and as shown in FIG. 1, Bk (black), C (cyan), M (magenta), Y on the same chip. In addition to (yellow), it is a short chip capable of discharging SP (treatment liquid), and the case where the short chip as shown in FIG.

  First, the basic ejection operation of a bubble jet (registered trademark) head, which is one type of inkjet head, will be described.

  The bubble jet (registered trademark) head is a system in which ink is rapidly heated by, for example, a heater, and ink liquid is ejected by pressure caused by generation of bubbles due to evaporation of ink.

  FIG. 5 shows the configuration of a bubble jet (registered trademark) head. The head 55 is generally configured by a heater board 104 which is a substrate on which a plurality of heaters 102 for heating ink is formed, and a top plate 106 placed on the heater board 104. A plurality of discharge ports 108 are formed in the top plate 106, and a tunnel-like liquid passage 110 communicating with the discharge ports 108 is formed behind the discharge ports 108. Each liquid path 110 is isolated from an adjacent liquid path by a partition wall 112. Each liquid passage 110 is commonly connected to one ink liquid chamber 114 at the rear thereof, and ink is supplied to the ink liquid chamber 114 via an ink supply port 116, and the ink is supplied from the ink liquid chamber 114. It is supplied to each liquid passage 110. The heater board 104 and the top plate 106 are assembled by being aligned so that each heater 102 comes to a position corresponding to each liquid path 110.

  Although only two heaters 102 are shown in FIG. 5, the heaters 102 are arranged one by one corresponding to the respective liquid paths 110. When a predetermined drive pulse is supplied to the heater 102 in the assembled state as shown in FIG. 5, the ink on the heater 102 boils to form bubbles, and the ink expands from the discharge port 108 by the volume expansion of the bubbles. Extruded and discharged.

  This is the discharge principle of the Bubble Jet (registered trademark) head. The heater board 104 is manufactured by a semiconductor process using a silicon substrate as a base, and a signal line for driving the heater 102 is connected to a drive circuit formed on the same substrate.

  Next, a case where the present invention is applied will be described below by taking a bubble jet (registered trademark) head as an example. First, as a treatment liquid discharge control method, a method of controlling an appropriate amount of liquid to be discharged is given. A chip (head) configuration in which black (Bk), cyan (C), magenta (M), and yellow (Y) can be discharged in the same chip, and in addition, a processing liquid (SP) can be discharged is shown in FIG. Shown in

  As already described, the bubble jet (registered trademark) head generates air bubbles in the ink by abruptly heating the ink with a heater, and ejects the ink by ejecting it from the discharge port by the volume expansion of the bubble. . Therefore, by controlling the drive pulse applied to the heater, it is possible to adjust the size of the bubbles, thereby controlling the amount of ink droplets to be ejected. Here, the treatment liquid (SP) is discharged in the same manner.

FIG. 3 illustrates drive pulses for the heater. 3A shows a pulse waveform of single pulse drive, and FIG. 3B shows a pulse waveform of double pulse drive. In the case of single pulse drive of FIG. 3A, not only the voltage (V−V ₀ ) but also the pulse width (T ) Can be changed to control the discharge amount. Further, from the viewpoint of the discharge amount control width, the double pulse drive of (b) can be adjusted more widely, and the efficiency is good.

In FIG. 3, T ₁ is called a pre-pulse width, T ₂ is called a pause period, and T ₃ is called a main pulse width. The reason why double pulse driving is more efficient than single pulse driving is that most of the heat generated by the heater is absorbed by the ink touching the surface of the heater. This is because it can play a role in helping to fire at the main pulse thereafter.

In the double pulse driving, the main pulse width T ₃ is constant, the pre-pulse width T ₁ by a variable, it is possible to adjust the discharge amount of the nozzle of the overlap portion. That is, the discharge amount and a longer T ₁ increases, decreases and shortening.

  Next, an example of controlling the discharge amount by assigning a different pre-pulse T1 for each nozzle in double pulse driving will be described.

As shown in FIG. 7, 2-bit data corresponding to the nozzle is written in the RAM areas A and B of the system board that controls the inkjet head. The 810 processing liquid ejection control unit in FIG. 8 can select the four types of pulses PH _{1 to} PH ₄ shown in FIGS. 6A to 6D based on the 2-bit data. For example, when the droplet amount is decreased, the pulse of PH ₁ is selected because it is (0, 0), and when the appropriate amount of liquid is increased, the pulse of PH ₄ is selected because it is (1, 1). In this way, the ejection amount can be changed by assigning the pre-pulse selection bits for each nozzle. Thereafter, the main pulse MH of FIG. 6E is applied.

  Here, in the case of thermal ink jet, when a signal with a long pulse width is applied, the amount of heat generated in the nozzle increases, and the head temperature rises.

FIG. 4 shows an electric circuit configuration of the discharge amount control. In FIG. 4, the signal line VH is the power source of the inkjet head, H _GND is the GND line for VH, MH is the main pulse signal line, PH _{1 to} PH ₄ are the pre-pulse signal lines shown above, and B _LAT is PH ₁ to Signal line for latching bit data for selecting PH ₄ , D _LAT is a signal line for latching data (image data) necessary for printing, DATA is bit data and image data transferred as serial data This is a signal line confirmed by the shift register.

In the configuration as shown in FIG. 4, the bit data (selection bit) shown in FIG. 7 is stored as serial data from the DATA signal line to the shift register. When the bit data of all nozzles is ready, a B _LAT signal is generated and the bit data is latched.

Next, image data necessary for printing is similarly stored in the shift register from the DATA signal line. When the data for all the nozzles is ready, a _DLAT signal is generated and the data is latched. First, _{one of} PH _{1 to} PH ₄ is selected from the latched bit data through the selection logic circuit. The selected PH signal and the main pulse signal MH are combined, and the print data and the AND are further driven to drive the transistor of the nozzle N. VH is applied to the resistor (heater board) and ink is ejected from the nozzle. This process is performed over all nozzles.

The combined waveform of the PH signal and the MH signal is as shown in (f) to (i) of FIG. It is possible to control the discharge amount by sending new bit data to the shift register at a desired timing to change the discharge amount and generating the _BLAT signal.

  In the above driving example, four types of PH pulses can be selected using 2 bits. Furthermore, finer discharge amount control can be performed by increasing the number of bits. Needless to say, it becomes complicated.

  Next, a specific flow of discharge amount control will be described.

  First, the head temperature detection unit indicated by reference numeral 811 in FIG. Based on this, the CPU 801 determines how many pulses are applied to which position of the processing liquid discharge nozzle and determines the selection bit of the pre-pulse. Here, as a matter of course, the appropriate amount of the processing liquid changes with the pre-pulse. However, the processing liquid is a colorless liquid in the first place, and the driving amount is about 25% maximum at the initial setting. Since the effect is sufficiently exerted, even if the amount is slightly changed, the image is not affected.

  In this embodiment, pre-pulse selection is performed in 2 bits and 4 stages, but by increasing the number of bits, finer ejection amount control is possible (as a result, the head temperature can be finely controlled). However, since this is an action that complicates the circuit configuration and leads to an increase in cost, it is considered that the variable range of the required discharge amount (head temperature) is determined by preliminary examination from the specifications of the entire apparatus.

  In the above embodiment, the ejection amount is changed by switching the width of the drive pulse. In this case, the voltage is constant, but of course, the same effect can be obtained by changing the voltage instead of the pulse width.

  The timing at which the above-described control is performed in units of pages or within the same page printing is determined by the specifications of the apparatus.

  Furthermore, an object of the present invention is to eliminate density unevenness on a recording medium that occurs due to a difference in ink droplet amount depending on the head temperature. The density unevenness varies greatly depending on the type of recording medium. For example, so-called density unevenness that cannot be seen on plain paper is clearly visible on a medium whose surface is coated (glossy paper). In other words, more precise control is required for glossy paper. Therefore, in this embodiment, a sensor capable of detecting the level of reflected light, such as a photo sensor, is mounted, the type of the recording medium is detected, and the discharge condition of the processing liquid is automatically determined according to the type of the recording medium. It has changed.

  In the second embodiment, a method for controlling the temperature of the chip by changing the printing duty (number of ink droplets) of the treatment liquid will be described. The temperature of the bubble jet (registered trademark) head varies greatly depending on the number of nozzles used at one time and the print duty of each nozzle. By utilizing this property, the temperature of the chip itself can be changed. As already described in the first embodiment, the printing duty of the treatment liquid itself is about 25% and the effect is exhibited. That is, the temperature of the chip can be raised with the remaining 75%.

  For example, the temperature of each chip during printing is monitored, and when the temperature of a certain chip is low, the temperature is raised by increasing the duty of the processing liquid discharge data (print data) of that chip. It is determined by prior experiment how much the temperature of the chip can be changed by changing the duty of the treatment liquid. The print data is stored in the 810 treatment liquid discharge control unit of FIG. It is used as print data for the treatment liquid according to

  In the same manner as in the first embodiment, the above control method is determined according to the specifications of the apparatus as to which timing is to be executed in units of pages or within the same page printing. Also, the point of changing the control method conditions depending on the type of recording medium is the same as that described in the embodiment.

  As the third embodiment, a configuration in which the first and second embodiments are combined can be considered.

  When combined, control over a wider temperature range is possible. For example, the following control can be performed by combining them.

In the first place, the processing liquid is a recording performance improving liquid, but it is necessary to further increase the chip temperature even when the duty of the print data necessary for the original color ink image formation is high on the recording medium. Furthermore, it is considered that it is not a good idea to increase the print duty of the treatment liquid in view of the ink absorption capability of the recording medium. Under such circumstances, it can be dealt with by increasing the amount per one treatment liquid described in Example 1 and raising the temperature. (Of course, increasing the amount per droplet requires far less processing liquid on the recording medium than increasing the number of droplets itself.)
As described above, the combination of the first and second embodiments makes it possible to perform optimal control according to the printing situation.

  In the fourth embodiment, the case where the present invention is applied to an integrated head will be described instead of a configuration in which short chips are connected as shown in FIG.

  The integrated type is basically the same as the method described in the first to third embodiments, but in the case of the integrated type, the print duty of a part of the head is increased depending on the print pattern, and the location is increased. Even when the temperature is raised, it is easily expected that the temperature diffuses to the periphery and a gentle temperature gradient is formed. (Of course, depending on the material constituting the head, in the case of the Bubble Jet (registered trademark) head in this embodiment, heat transfer is fast because it is a silicon base). Therefore, it has been described in the previous embodiments. Compared to the connection head, density unevenness due to a partial difference in ink ejection amount due to a difference in temperature tends to be difficult to recognize from the viewpoint of visual characteristics.

Therefore, in the case of the integrated head, first, the temperature rise data of the head according to the printing conditions is experimentally confirmed. For example, in what area of the head (here, the number of nozzles) what print duty image is printed at what speed, how much temperature rise occurs in which area of the head It is necessary to keep an eye on it. (Since this differs depending on the material constituting the head as described above, it is necessary to confirm in advance by experiment)
As a result, the range in which the head temperature is controlled is known.

  The temperature control method using the discharge of the treatment liquid after detecting the head temperature is the same as in the first to third embodiments.

It is a figure which shows an example of the chip | tip which has the discharge nozzle of different color ink and a process liquid in the chip | tip. It is a figure which shows an example of the connection head which connected the chip | tip of FIG. It is a figure for demonstrating an ejection drive pulse. It is a figure which shows an example of a drive circuit. It is a figure showing the structure of a bubble jet (trademark) head. It is a figure for demonstrating selection of a drive pulse (a pre pulse, a main pulse, and a synthetic | combination pulse). It is the figure which showed the prepulse selection bit table. 1 is a system configuration diagram of an inkjet printer. It is a figure of the integrated head carrying processing liquid (SP).

Explanation of symbols

DESCRIPTION OF SYMBOLS 102 Heater 104 Heater board 106 Top plate 108 Ejection port 110 Ink liquid path 112 Partition 114 Ink liquid chamber 116 Ink supply tube

Claims (7)

An inkjet recording apparatus that performs recording using a head capable of ejecting ink and processing liquid from the same chip,
Detecting means for detecting the temperature of the chip;
An ink jet recording apparatus comprising: a control unit that controls discharge of the processing liquid according to a detection result of the detection unit and changes a temperature of the chip.   The inkjet apparatus according to claim 1, wherein the head is a connection head configured by connecting a plurality of chips.   2. The inkjet apparatus according to claim 1, wherein the treatment liquid is applied to the same position of the recording medium before the ink.   2. The ink jet apparatus according to claim 1, wherein the treatment liquid is applied to the same position of the recording medium after the ink.   The inkjet apparatus according to claim 1, wherein the control unit changes a discharge duty of the processing liquid.   The inkjet apparatus according to claim 1, wherein the control unit changes a discharge amount of the processing liquid.   The ink jet apparatus according to claim 1, wherein the control unit varies discharge control of the processing liquid according to a type of a recording medium.

Images