JP2010131862A - Head substrate and inkjet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that temperature variation is generated in a head substrate by a rise of temperature due to heating of a functional circuit in the event of recording, which results in variation in an ejection amount of ink by each nozzle, thereby degrading quality of a recorded image in an inkjet recording head which is of a constant current drive type having the functional circuit accompanied by heat generation. <P>SOLUTION: At least a part of functional circuits accompanied by heat generation such as constant current sources or reference current circuits are laid out along a row formed by a plurality of nozzles. In addition, the constant current sources can be laid out between respective nozzle rows in parallel to a nozzle row direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a head substrate and an ink jet recording head.

  The ink jet recording method is a method of forming an image by ejecting droplets from a discharge port using a heating resistor element or a piezoelectric element, and attaching the droplets to a predetermined position on a recording medium. For this reason, a heating resistance element and a piezoelectric element corresponding to each ejection port are arranged on the head substrate of the ink jet recording head (hereinafter referred to as recording head). Then, ejection energy is selectively generated from these elements according to the input image data, and ink droplets are ejected by this energy.

  Such recording heads are increasing in number of nozzles with the aim of further speeding up.

  With regard to this nozzle, at present, the number of nozzles is increased to a maximum of 512 nozzles in one row by a recording head mounted on a recording apparatus that records an image on an A3 size recording medium.

  With the increase in the number of nozzles, the difference in current value due to the voltage drop of the power supply wiring placed on the head substrate when ink is ejected from a small number of nozzles and when ink is ejected from many nozzles, heating resistance The variation of the element (heater) is a harmful effect. As a countermeasure against this problem, for example, Patent Document 1 and Patent Document 2 propose a constant current adjustment circuit that alleviates this problem by adjusting a constant current flowing through the heater.

  FIG. 8 is a diagram showing a circuit configuration of a head substrate that drives a constant current of (x × m) heaters that are configured by m groups that contain x heaters.

  As shown in FIG. 8, each of the m groups 1100-1 to 1100-m includes x heaters 1101-11... And switching elements 1102-11.

  As shown in FIG. 8, the constant current drive circuit of the head substrate is roughly composed of a reference voltage circuit 101, a current adjustment circuit 102, a reference current circuit 103, and a constant current source block 104. The reference voltage circuit 101 generates a reference voltage (Vref). The current adjustment circuit 102 generates a variable current output corresponding to the digital input data based on the reference voltage (Vref) that is the output of the reference voltage circuit 101. The reference current circuit 103 is composed of a current mirror circuit, and generates a reference current (Iref).

  The constant current source block 104 outputs constant currents Ih1 to Ihm proportional to the reference current (Iref) by current mirror circuits 106-1 to 106-m, which are constant current sources, and supplies them to the heaters 1101-11 to 1101-mx. .

  These current mirror circuits are composed of MOS transistors.

  From the reference current circuit 103, the reference current is supplied not only to the constant current source block 104 but also to other constant current blocks 104a, 104b, and 104c having the same configuration.

  The current adjustment circuit 102 includes a shift register (S / R) 102a for inputting the recording data signal DATA in synchronization with the clock signal CLK from the outside, and a latch circuit (Latch) 102b for latching the recording data signal DATA by the latch signal LT. Yes.

  Further, the current adjustment circuit 102 includes a current variable circuit block including an R-2R resistor array and a MOS transistor.

  The recording data signal serial-parallel converted by the shift register (S / R) 102a and the latch circuit (Latch) 102b is output to the current variable circuit.

  The current variable circuit includes a resistor and a MOS transistor that functions as a switch. The (n + 1) resistors ra1 to ran + 1 whose resistance value is “R” are connected in series with the ground end (GND) as one end. On the other hand, one end of resistors rb1 to rbn having a resistance value “2R” twice as large as the resistors ra1 to ran + 1 is connected to each connection point of the resistors ra1 to ran. The other end is connected to each source of the MOS transistors 102-1a to 102-na and 102-1b to 102nb.

  The drains of the MOS transistors 102-1a to 102-na and the MOS transistors 102-1b to 102nb are connected to a reference current output terminal (Iref) and a reference voltage (Vref), respectively. On the other hand, a digital signal from the latch circuit 102b is applied to the gates of the MOS transistors 102-1a to 102na. An output obtained by inverting the signal from the latch circuit 102b by the inverter 102c is connected to the gates of the MOS transistors 102-1b to 102nb which are paired with the MOS transistors 102-1a to 102na.

  The MOS transistors 102-1a to 102-na and the MOS transistors 102-1b to 102nb function as switches that turn on / off between the source and the drain, and are controlled by a digital signal from the latch circuit 102b.

  The non-inverting input terminal (+) of the operational amplifier 102d is connected to the reference voltage (Vref) and the drains of the MOS transistors 102-1b to 102-nb. The inverting input terminal (−) is connected to the drain terminals of the MOS transistors 102-1a to 102-na and the source of the output MOS transistor 102e. The output of the operational amplifier 102d is connected to the gate of the MOS transistor 102e. The drain of the MOS transistor 102 e serves as an output terminal for current (Iref) and is output to the reference current circuit 103.

  Further, the inverting input terminal (−) of the operational amplifier 102d has the source output of the MOS transistor 102e for output so that the signal potential is the same as the reference voltage (Vref) connected to the non-inverting input terminal (+). Is entered. The output of the operational amplifier 102d is input to the gate of the output MOS transistor 102e, and the source output is controlled. As a result, the reference voltage (Vref) is also applied to the drains of the MOS transistors 102-1a to 102-na connected to the inverting input terminal (−) of the operational amplifier 102d.

  On the other hand, a reference voltage (Vref) is input to the drains of the MOS transistors 102-1b to 102-nb. As shown in FIG. 8, the MOS transistors 102-1a to 102na and the MOS transistors 102-1b to 102nb form a pair, and the gates of the MOS transistor pairs are connected via the inverter 102c. Therefore, one of the MOS transistor pairs connected to the resistors rb1 to rbn is always turned on.

  Here, the resistance between the source and the drain when the MOS transistors 102-1a to 102-na and the MOS transistors 102-1b to 102-nb are on can be ignored with respect to the resistance value (2R) of the resistances rb1 to rbn. Let it be small. Then, the reference voltage (Vref) is always applied to one end of the resistors rb1 to rbn via the MOS transistors 102-1a to 102-na or the MOS transistors 102-1b to 102nb.

  Here, the currents I1 to In flowing through the resistors rb1 to rbn are I1 = Vref / (2 × R), I2 = Vref / (2 × 2 × R),..., In = Vref / (2n × R) It becomes.

  Of the MOS transistors 102-1a to 102-na, the MOS transistors corresponding to the ON signal of the digital input signal output the sum of the corresponding portions of the currents I1 to In to the current output terminal (Iout). The

As described above, each of the currents I1 to In is a current weighted by 1/2. Therefore, a current having 2 ⁿ types of values can be output from the current output terminal (Iout) by an arbitrary digital signal input to the MOS transistors 102-1a to 102-na. In other words, the output reference current (Iref) is variable in the range of 0 to Vref / R in ²ⁿ steps.

  Note that by connecting a resistor Roff having a resistance value (R1) between the source of the MOS transistor 102e and GND, Vref is applied to both ends of the resistor Roff, and a current of Vref / R1 can always flow. Therefore, an offset of Vref / R1 can be added to the variable range of the current, and the variable range of the reference current (Iref) can be Vref / R1 to Vref / R1 + Vref / R.

However, the constant current adjustment circuit generates approximately the current of the reference current circuit by the heat generation of the current mirror circuit of the reference current circuit 103 and the heat generation of the current mirror circuit of m constant current sources in each heater group of the constant current source block 104. With 10 times the heat generation. For this reason, the temperature inside the head substrate is partially raised during recording. For example, when there are n nozzles in a row and m groups of x heaters in a row, the number of current mirror circuits is n in the reference current circuit and n × m in the constant current source block. . The ratio of the heat generation amount is heat generation of the reference current circuit: heat generation of the current source block = 1: 10 × m.
JP 2002-348725 A Japanese Patent Application No. 2004-158030

  FIG. 9 is a diagram showing an example of a typical layout in which a functional circuit (for example, a reference current circuit) with heat generation is mounted in a conventional recording head.

  In this layout configuration, as shown in FIG. 9A, two nozzle rows each composed of a plurality of nozzles are opposed to each other with a liquid supply port (ink supply port) interposed therebetween.

  Now, it is known that a head substrate provided with a heater and a switching element is made of Si and has high thermal conductivity. In the layout configuration shown in FIG. 9A, since the Si head substrate has slits as liquid supply ports, it is difficult to uniformly transmit the temperature between the nozzle rows. Therefore, as shown in FIG. 9A, when a functional circuit that generates heat is arranged at the end of the head substrate, the head substrate in the nozzle row direction XY is heated by the circuit that generates heat during recording. The temperature distribution on the surface is high on the outer side of the nozzle row and lower on the inner side, resulting in temperature unevenness.

  Such temperature unevenness leads to temperature unevenness of droplets for each nozzle. This unevenness causes a change in the ink discharge amount for each nozzle. For example, when the recording head ejects a plurality of colors of ink to perform color recording, color unevenness occurs, leading to image degradation. The problem is that the higher the heating value of the functional circuit is, or the longer the nozzle array is for higher recording speed, the greater the temperature gradient of the nozzle array on the head substrate and the more likely the color irregularity becomes. .

The present invention has been made in view of the above conventional example, and an object thereof is to provide a head substrate capable of reducing temperature unevenness and a recording head using the head substrate.
It is an object of the present invention to be in the chip.

  In order to achieve the above object, the head substrate of the present invention has the following configuration.

  That is, a slit-shaped ink supply port, a plurality of heaters arranged along the longitudinal direction of the ink supply port, and the plurality of heaters arranged along the row of the plurality of arranged heaters have a constant current. A head substrate for an ink jet recording head, comprising: a plurality of switching elements to be driven; and a functional circuit for controlling constant current driving of the plurality of switching elements, wherein the plurality of recording elements, the plurality of switching elements, At least a part of the functional circuit is arranged along the direction in which the components are arranged.

  According to another aspect of the invention, there is provided an ink jet recording head having a head substrate having the above-described configuration and an orifice substrate having a plurality of ink ejection openings corresponding to the plurality of recording elements.

  Therefore, according to the present invention, there is an effect that the temperature around the heater becomes uniform by laying out the functional circuit with heat generation along the row of the plurality of heaters and the plurality of switching elements for driving them. As a result, the temperature distribution biased in the heater array direction is eliminated, and good recording can be performed. For example, in the case of an ink jet recording head that ejects ink, the ink ejection amount becomes stable, and high-quality image recording can be realized.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to already demonstrated part and duplication description is abbreviate | omitted.

  In this specification, “recording” (sometimes referred to as “printing”) is not limited to the case of forming significant information such as characters and graphics, but may be significant. Furthermore, it also represents a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or a medium is processed regardless of whether or not it is manifested so that a human can perceive it visually.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Further, “ink” (sometimes referred to as “liquid”) should be interpreted widely as in the definition of “recording (printing)”. Therefore, by being applied on the recording medium, it is used for formation of images, patterns, patterns, etc., processing of the recording medium, or ink processing (for example, solidification or insolubilization of the colorant in the ink applied to the recording medium). It shall represent a liquid that can be made.

  Furthermore, unless otherwise specified, the “recording element” collectively refers to an ejection port or a liquid path communicating with the ejection port and an element that generates energy used for ink ejection.

  The head substrate used below does not indicate a simple substrate made of a silicon semiconductor but indicates a configuration in which each element, wiring, and the like are provided.

  Further, the term “on the substrate” means not only the element substrate but also the surface of the element substrate and the inside of the element substrate near the surface. The term “built-in” as used in the present invention is not a word indicating that each separate element is simply arranged separately on the surface of the substrate. It shows that it is integrally formed and manufactured on top.

<Description of Inkjet Recording Apparatus (FIG. 1)>
FIG. 1 is an external perspective view showing an outline of the configuration of an ink jet recording apparatus 1 which is a typical embodiment of the present invention.

  As shown in FIG. 1, an ink jet recording apparatus (hereinafter referred to as a recording apparatus) has an ink jet recording head (hereinafter referred to as a recording head) 3 that performs recording by discharging ink in accordance with an ink jet system. Recording is performed by reciprocating in the direction. A recording medium P such as recording paper is fed through the paper feeding mechanism 5 and conveyed to a recording position, and recording is performed by discharging ink from the recording head 3 to the recording medium P at the recording position.

  In addition to mounting the recording head 3 on the carriage 2 of the recording apparatus 1, an ink cartridge 6 for storing ink to be supplied to the recording head 3 is mounted. The ink cartridge 6 is detachable from the carriage 2.

  The recording apparatus 1 shown in FIG. 1 is capable of color recording. For this reason, the carriage 2 contains four inks containing magenta (M), cyan (C), yellow (Y), and black (K) inks, respectively. An ink cartridge is installed. These four ink cartridges are detachable independently.

  The recording head 3 of this embodiment employs an ink jet system that ejects ink using thermal energy. For this reason, an electrothermal converter is provided. The electrothermal transducer is provided corresponding to each of the ejection ports, and ink is ejected from the corresponding ejection port by applying a pulse voltage to the corresponding electrothermal transducer in accordance with the recording signal.

<Control Configuration of Inkjet Recording Apparatus (FIG. 2)>
FIG. 2 is a block diagram showing a control configuration of the recording apparatus shown in FIG.

  As shown in FIG. 2, the controller 600 includes an MPU 601, a ROM 602, a special purpose integrated circuit (ASIC) 603, a RAM 604, a system bus 605, an A / D converter 606, and the like. Here, the ROM 602 stores a program corresponding to a control sequence to be described later, a required table, and other fixed data. The ASIC 603 generates control signals for controlling the carriage motor M1, the transport motor M2, and the recording head 3. The RAM 604 is used as a development area for image data, a work area for program execution, and the like. A system bus 605 connects the MPU 601, the ASIC 603, and the RAM 604 to each other to exchange data. The A / D converter 606 inputs analog signals from the sensor group described below, performs A / D conversion, and supplies a digital signal to the MPU 601.

  In FIG. 2, reference numeral 610 denotes a computer (or a reader for image reading, a digital camera, etc.) serving as a supply source of image data, and is collectively referred to as a host device. Image data, commands, status signals, and the like are transmitted and received between the host apparatus 610 and the recording apparatus 1 via an interface (I / F) 611. This image data is input in a raster format, for example.

  Reference numeral 620 denotes a switch group, which includes a power switch 621, a print switch 622, a recovery switch 623, and the like.

  Reference numeral 630 denotes a sensor group for detecting the apparatus state, and includes a position sensor 631, a temperature sensor 632, and the like.

  Further, 640 is a carriage motor driver that drives a carriage motor M1 for reciprocating scanning of the carriage 2 in the direction of arrow A, and 642 is a conveyance motor driver that drives a conveyance motor M2 for conveying the recording medium P.

  The ASIC 603 transfers data for driving a recording element (ejection heater) to the recording head while directly accessing the storage area of the RAM 604 during recording scanning by the recording head 3.

  FIG. 3 is a diagram schematically showing the configuration of the recording head 3.

  3A is a partially broken perspective view schematically illustrating a three-dimensional configuration of the recording head, and FIG. 3B is a diagram illustrating an ink discharge surface of the recording head.

  As shown in FIG. 3A, the recording head 3 includes a head substrate provided with an electrothermal conversion element and an orifice that is laminated and bonded to the main surface of the head substrate to form a plurality of ink flow paths. And a substrate. Further, as shown in FIGS. 3A and 3B, the recording head 3 includes a plurality of electrothermal transducer elements and a plurality of nozzles, and a nozzle row 1 in which the plurality of nozzles are arranged in a row. , And a nozzle row 2 arranged in parallel to a position facing the nozzle row 1 across the ink supply port.

  The ink is filled from the ink supply port into the foaming chamber and the discharge port through the liquid supply path. Then, ink droplets are ejected from the ejection ports by a sudden foaming pressure due to a gas-liquid phase change caused by boiling the ink instantaneously by the electrothermal conversion element.

  The configuration shown in FIG. 1 is a configuration in which the ink cartridge 6 and the recording head 3 can be separated, but a replaceable head cartridge may be configured by integrally forming them.

  FIG. 4 is an external perspective view showing a configuration of a head cartridge IJC in which an ink tank and a recording head are integrally formed. In FIG. 4, a dotted line K is a boundary line between the ink tank IT and the recording head IJH. The head cartridge IJC is provided with an electrode (not shown) for receiving an electrical signal supplied from the carriage 2 when it is mounted on the carriage 2, and the recording head IJH as described above is provided by this electrical signal. Is driven to eject ink.

  In FIG. 4, reference numeral 500 denotes an ink ejection port array.

  Next, several embodiments of the recording apparatus and the head substrate used in the recording head will be described.

  FIG. 5 is a block diagram showing a layout of the head substrate according to the first embodiment of the present invention.

  As shown in FIG. 5, the head substrate sandwiches the slit-shaped ink supply port 100 and energizes the heaters 1101-11 to 1101-mx symmetrically (xxm) along the longitudinal direction thereof. Switching elements 1102-11 to 1102-mx to be controlled are provided. The (xxm) heaters and the (xxm) switching elements are each composed of m groups each containing x heaters and switching elements. The constant current sources 106-1 to 106-m, which are functional circuits with heat generation, are arranged in the vicinity of the heater.

  FIG. 6 schematically shows the layout configuration shown in FIG. In this example, a constant current source is shown as a functional circuit that generates heat.

  As shown in FIG. 6A, the constant current source is laid out between the nozzle rows in parallel with the nozzle row direction so as to have the same length as the nozzle row, so that the nozzle row direction as shown in FIG. The temperature distribution on the XY head substrate surface can be made uniform. Further, it is more effective if the reference current circuit is also laid out between the nozzle rows in parallel with the nozzle row direction as a function circuit with heat generation.

  Therefore, according to the embodiment described above, since at least a part of the functional circuit is laid out between the nozzle rows, it is possible to reduce the temperature variation in the nozzle row direction that has occurred in the conventional head substrate. Such an effect becomes more prominent as the calorific value of the functional circuit is larger.

  FIG. 7 is a diagram schematically showing a layout configuration of the head substrate according to the second embodiment of the present invention.

  In the configuration shown in FIG. 7, the reference current circuit is laid out at the end of the head substrate perpendicular to the nozzle row direction, and the constant current source is laid out between the nozzle rows in parallel with the nozzle row direction.

  Distributing constant current drive circuits in this way is effective when you do not want to increase the space occupied by constant current drive circuits between nozzle rows, for example, because you want to place other circuits between nozzle rows. is there. However, this configuration also contributes to uniform temperature variation of the head substrate because the constant current source is laid out between the nozzle rows in parallel with the nozzle row direction.

  In the above embodiment, the liquid droplets ejected from the recording head applied to the recording apparatus are described as ink, and the liquid stored in the ink tank is described as ink. Is not limited to ink.

  In addition, the above embodiment includes means (for example, an electrothermal converter) that generates thermal energy as energy used for performing ink ejection, particularly in the ink jet recording system. For this reason, it is possible to achieve higher recording density and higher definition by using a system in which the thermal energy causes a change in the state of the ink.

  In addition, the ink jet recording apparatus according to the present invention may be used as an image output apparatus for information processing equipment such as a computer, a copying apparatus combined with a reader, or a facsimile apparatus having a transmission / reception function. It may be one taken.

1 is an external perspective view showing an outline of a configuration of an ink jet recording apparatus that is a typical embodiment of the present invention. 3 is a block diagram illustrating a configuration of a control circuit of the recording apparatus. FIG. 2 is a diagram schematically illustrating a configuration of a recording head 3. FIG. 2 is an external perspective view showing a configuration of a head cartridge IJC in which an ink tank and a recording head are integrally formed. FIG. It is a block diagram which shows the layout of the head substrate according to Example 1 of this invention. FIG. 6 is a diagram schematically showing the layout configuration shown in FIG. 5. It is a figure which shows typically the layout structure of the head substrate according to Example 2 of this invention. It is a figure which shows the circuit structure of the head board | substrate which carries out constant current drive of the (xxm) heaters comprised with m groups which accommodate x heaters. It is the top view which showed an example of the layout of the conventional nozzle row and a functional circuit.

Explanation of symbols

3 Recording Head 100 Ink Supply Ports 1101-11 to 1101-mx Heaters 1102-11 to 1102-mx Switching Elements 106-1 to 106-m Constant Current Source

Claims (7)

The slit-shaped ink supply port, the plurality of heaters arranged along the longitudinal direction of the ink supply port, and the plurality of heaters arranged along the row of the arranged heaters are driven at a constant current. A head substrate for an inkjet recording head comprising a plurality of switching elements and a functional circuit for controlling constant current driving of the plurality of switching elements,
At least a part of the functional circuit is arranged along a direction in which the plurality of recording elements and the plurality of switching elements are arranged. The functional circuit is
A plurality of constant current sources for supplying a constant current to the plurality of switching elements;
The head substrate according to claim 1, further comprising a reference current circuit that supplies a reference current to the plurality of constant current sources.   The head substrate according to claim 2, wherein the plurality of constant current sources are arranged along a direction in which the plurality of heaters and the plurality of switching elements are arranged.   The head substrate according to claim 3, wherein the reference current circuit is further arranged along a direction in which the plurality of heaters and the plurality of switching elements are arranged.   4. The head according to claim 3, wherein the reference current circuit is disposed at an end portion of the head substrate along a direction perpendicular to a direction in which the plurality of heaters and the plurality of switching elements are arranged. 5. substrate. A plurality of the ink supply ports;
2. The plurality of heater rows, the plurality of switching element rows, and at least a part of the functional circuit are arranged along a longitudinal direction of each of the plurality of ink supply ports. The head substrate according to any one of 6. The head substrate according to any one of claims 1 to 6,
An ink jet recording head having an orifice substrate provided with a plurality of ink ejection openings corresponding to each of the plurality of heaters.

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