JP2006096007A - Head substrate, recording head, head cartridge, and recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a head substrate which can drive a uniform driving condition to all of driving elements regardless of voltage variation and irregularities of a power supply wiring system, and to provide a recording head, a head cartridge, and a recorder which carries out recording by using the recording head and head cartridge. <P>SOLUTION: A plurality of driving elements for driving the recording elements are provided respectively correspondingly to the plurality of recording elements at the head substrate equipped with the plurality of recording elements divided to a plurality of blocks for time sharing driving. A plurality of constant current circuits for carrying a constant current to the plurality of recording elements are set for every plurality of the blocks. Moreover, a control circuit is set for controlling a value of the constant current in accordance with a regulation signal inputted from the outside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a head substrate, a recording head, a head cartridge, and a recording apparatus, and in particular, for example, a head substrate including a plurality of recording elements that perform recording according to an inkjet method, a recording head using the head substrate, a recording head, and the recording head The present invention relates to a head cartridge incorporating an ink tank, and a recording apparatus that performs recording using the recording head or the head cartridge.

  Ink jet printers using thermal energy are widely used because they are inexpensive, can use plain paper, are easy to color record, and have high image quality.

  FIG. 11 is a diagram showing a configuration of a driving circuit of a conventional general thermal ink jet recording head (hereinafter referred to as a recording head).

  As shown in FIG. 11, a heater 101 formed on a substrate and a power transistor 102 for driving the heater 101 are connected between a VH wiring 106 and a GNDH wiring 107 as a power source. On the other hand, the control circuit 108 applies an on / off signal 109 generated by inputting print data and a control signal to the power transistor 102 to drive the heater 101.

  In the case of a print head equipped with a large number of recent heaters, in addition to adopting time-division driving, the following is performed so that a large number of heaters can be driven uniformly while keeping the amount of heat generated from the heater constant. Proposals have been made in consideration of various aspects as exemplified.

(1) From the aspect of time-division drive and distributed drive When all the heat generating elements built in are driven at the same time, a large current flows, resulting in a large voltage drop in the current path and a large power supply capacity, making it difficult to drive. I fall. Further, a large mutual pressure interference occurs between the nozzles that eject the ink, thereby preventing uniform ejection.

  Therefore, Patent Document 1 proposes a method in which a heater group is divided into a plurality of blocks and each block is driven in a time-sharing manner in the case of a recording head having a large number of heaters. Patent Document 2 proposes a method in which the heating elements that are driven simultaneously are distributed and driven so that adjacent heating elements in the block are not selected continuously. As described above, a method in which time-division driving and distributed driving are combined in consideration of both the power surface and the ink ejection surface is employed. Note that most of the time-division driving employs a matrix circuit configuration in order to reduce the circuit scale.

(2) From the aspect of uniform driving On the substrate of the recording head, a heater made of a thin film or thick film resistor is driven by a switching circuit composed of a transistor or the like, but is ejected to record a high-quality image It is necessary to make the amount of ink droplets constant. Regardless of the power supply voltage, the ambient temperature, and the characteristics of individual parts and forming members on the drive surface, the heating value of the heater is constant and between the heaters. It is required to drive uniformly.

(3) From the standpoint of block individual wiring, time-division driving combined with distributed driving consists of one block consisting of N bits (ie, N heaters). There is one that selectively drives only one heater. Therefore, when there are M blocks, the total number of simultaneously driven bits is N.

  Hereinafter, this time division configuration is referred to as M block × N bit time division.

  FIG. 12 is a diagram showing a power feeding configuration to the substrate of the recording head that is time-division driven.

  In the configuration shown in FIG. 12, power is supplied from the short sides 204 and 206 on the left and right sides of the substrate. Further, in the configuration shown in this figure, the ink supply port 202 is positioned in the central long side direction of the substrate 201, and two nozzle rows are arranged on both sides so as to sandwich this. In the recording head mentioned here, there are a total of (M × N) heaters, that is, (M × N) nozzles corresponding thereto. When the nozzle numbers from 1 to (M × N) are assigned to the nozzles, (M × N) nozzles are arranged in a staggered manner in this recording head, as if there are two nozzle rows. Become. Here, the nozzle row with an odd nozzle number is called an ODD side nozzle row, and the nozzle row with an even nozzle number is called an EVEN side nozzle row.

  As shown in FIG. 12, heaters corresponding to the nozzles and driver ICs 205 for driving the nozzles are disposed on the ODD side nozzle row 203a and the EVEN side nozzle row 203b on the side away from the ink supply port 202. When the recording head having such a configuration is driven, the two nozzle rows are divided into four regions of ODD_L, ODD_R, EVEN_L, and EVEN_R and simultaneously operated, as indicated by a one-dot chain line.

  Therefore, in this case, the power supply and the control line are fed separately for each of the four regions. However, in order to correspond to the configuration of the recording head in which a plurality of substrates are arranged to increase the recording width, the feeding point is the short side 204 , 206 side.

  FIG. 13 is a circuit diagram showing an example of power supply wiring in the ODD_L region shown in FIG.

  In time-division driving in which only one bit (that is, one heater) is selectively driven in the block, in order to apply a uniform voltage to all the heaters, as shown in FIG. The power supply VH wiring 106 and the GNDH wiring 107 wired to the drive circuit are designed to branch from the feeding point 103 and individually wire to each block so that the wiring resistance between the blocks becomes equal.

  The layer structure related to wiring here is a process of Al wiring two-layer structure, of which one layer is for power supply wiring and the other layer is for input / output signal wiring for connecting a heater, input / output signal and driver IC It is devoted to. In addition, about the place where wiring is long, Cu plating is partially performed to Al wiring, and it controls so that it may become fixed wiring resistance. In the case of wiring resistance specifications that can be handled by Al + Cu, as described above, Cu plating is partially applied and wiring is performed with a uniform width to each block. Change the width to a constant resistance. In this way, regardless of the distance from the feeding point to the block, the voltage drop in the power supply wiring is the same between the blocks, and the same voltage is applied to all the heaters.

(4) From the aspect of pulse width correction The amount of heat generated by the heater is controlled by the resistance value, applied voltage, and applied time. Of these, as long as the inventor confirms the resistance value in the manufacturing process, there is a variation of about 20% in the substrate, between the substrates, between the wafers, between the lots, and the like. Reference 3 refers to a resistance value of a dummy heater formed in the same process as a discharge heater built on a substrate, and a method of optimizing driving by adjusting a pulse width as an application time according to the reference value. is suggesting.

  Further, in Patent Document 4, a driving circuit is built in the substrate, and a MOS transistor built on the substrate is formed in the same manner as Patent Document 3 with respect to ON resistance variation of a MOS transistor that is a switching element for driving a heater. And a method of optimizing driving by referring to the ON resistance value of the dummy MOS transistor formed by the same process and adjusting the pulse width according to the reference value. Then, the resistance variation of the heater and the ON resistance variation of the MOS transistor are collectively corrected and the pulse width is corrected to drive uniformly.

  In the wiring example shown in FIG. 13, a wiring resistance Rc is interposed from the VH power supply 110 to the substrate of the recording head. Even if the simultaneous ON current is greatly reduced by the time-division driving, the number of bits that are driven simultaneously according to the recording data does not change, and the voltage fluctuation due to the voltage drop of the wiring resistance still remains. As a driving means for correcting the voltage fluctuation due to the load fluctuation, in Patent Document 5, the pulse width is changed based on the predetermined number of simultaneous ON bits and the voltage drop of the wiring resistance in accordance with the number of simultaneously driven bits. A method of optimizing driving is proposed.

As described above, in the time-division driving, the pulse width correction and the block individual wiring as described above are introduced to make the heat generation amount of the heater constant and to drive the plurality of heaters uniformly.
JP-A-9-327914 JP-A-7-112528 JP-A-7-76077 JP 10-95116 A Japanese Patent Laid-Open No. 10-181017

  However, in the above-mentioned conventional example, as a countermeasure against the heat generation fluctuation of the heater, the individual block wiring and the pulse width correction are introduced to cope with it. It has been pointed out that there are other factors that affect the amount of heat generated by the heater. Even if it is effective, it cannot be said to be a sufficient countermeasure.

  Each factor will be specifically described below.

(1) Influence on substrate size due to lengthening of recording head Individual block wiring based on time-division driving is an indispensable design requirement as described above, but as the number of blocks increases, In a long recording head, the area of the power supply wiring is greatly increased in the substrate width direction as the number of power supply wirings is increased.

For example, in the example of the wiring shown in FIG. 13, when the recording width of the region ODD_L is about 6 inches and the recording element of 88 blocks × 40 bits is time-division driven, the individual wiring resistance R _VH of the VH wiring is set in terms of driving design. VH wiring 106 and GNDH wiring when 50Ω, GNDH wiring individual wiring resistance R _GNDH = 50Ω, wiring length L = 1.7 mm-152.4 mm, Al wiring film thickness 0.6 μm, Cu film thickness 5 μm The design of 107 can be estimated as follows.

That is, when the line (WL) / space (WS) of the VH wiring 106 and the GNDH wiring 107 is 10 μm / 10 μm in a configuration in which partial Cu plating is applied to the Al wiring,
VH wiring area width (W _VH ) = 1.76 mm,
GNDH wiring area width (W _GNDH ) = 1.76 mm,
Power supply wiring area (WP) = W _VH + W _GNDH = 3.52 mm
It becomes.

  Note that the short side dimension of the driver IC 205 is 2.5 mm in the conventional example.

  FIG. 14 is an external view of the substrate based on the above estimation.

  From the above consideration, the power supply wiring area requires a total of 3.52 mm, and the fact that the dimension of the short side of the driver IC 205 greatly exceeds 2.5 mm increases the board area only for power supply wiring, This means that the number of substrates that can be taken is reduced. Furthermore, an increase in substrate area leads to a decrease in yield and an increase in heater resistance variation, resulting in an increase in cost.

  By reducing the ink ejection frequency from the nozzles and reducing the number of blocks, it is possible to design without increasing the substrate width to some extent, but for a long recording head featuring high-speed recording, the high-speed performance is halved. It is meaningless because it will be done. As described above, it is required to suppress the production cost of the recording head substrate while reducing the area as much as possible. For this reason, from the viewpoint of slimming down the substrate width to reduce costs, the block individual wiring is efficiently wired so as to satisfy the condition of “power supply wiring area width <driver IC width”. Is required.

(2) Matching design and complex control As described in the previous example, monitoring the dummy elements for pulse width correction and setting the optimum pulse width is an effective means that can be realized with a relatively simple configuration. is there. On the other hand, setting the optimal pulse width according to the number of simultaneously driven bits for pulse width correction is designed to make the parasitic resistance such as connector contact resistance and cable wiring resistance sufficiently smaller than the heater resistance. In addition, it is necessary to manage variations in these parasitic resistances. Further, complicated control for monitoring the recording data and setting the pulse width on the recording apparatus main body side is also required. In such pulse width correction, there is a problem that fine adjustment design and complicated control of parasitic resistance are forced.

(3) Other factors Other factors include: (a) variations in power supply voltage that supplies power to the heater and voltage fluctuations result in fluctuations in the voltage applied directly to the heater; (b) turning on the MOS transistor The resistance may fluctuate due to temperature changes or gate voltage, but the power supply voltage fluctuation is dealt with by tightening the factory adjustment specifications to reduce the voltage variation at the time of product shipment. On-resistance fluctuations have been neglected because they have less influence than other factors. However, at present, none of the measures is a decisive measure.

  The present invention has been made in view of the above-described conventional example. A head substrate, a recording head, and a head cartridge capable of driving uniform driving conditions for all recording elements regardless of voltage fluctuations and variations in the power supply wiring system. An object of the present invention is to provide a recording apparatus that performs recording using the recording head and the head cartridge.

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

  That is, a head substrate including a plurality of recording elements divided into a plurality of blocks for time-division driving, a plurality of driving elements corresponding to each of the plurality of recording elements and driving the recording elements; A plurality of constant current circuits provided for each of the plurality of blocks and supplying a constant current to the plurality of recording elements, and a D / A converter that generates a control current based on a reference voltage and an adjustment signal input from the outside And a first power transistor that receives the control current as a collector, and controls the value of the constant current.

  On the other hand, this constant current circuit includes a second power transistor that commonly connects one end of a plurality of drive elements that drive a plurality of recording elements included in one block, and inputs the common connection end to a collector; A power transistor and a third power transistor constituting a first current mirror circuit; a fourth power transistor connected to a collector of the third power transistor; a fourth power transistor; and a first current mirror circuit; It is preferable to have a fifth power transistor constituting a different second current mirror circuit and a diode for anode input of the collector output of the fifth power transistor.

  Further, it is preferable that a resistor connected to the emitter output of the second power transistor is provided for each of the plurality of blocks, and the constant current value is controlled by the voltage generated by the diode and the resistor.

  The current flowing through the diode is determined by the first and second current mirror circuits.

  Further, it is preferable that one end of the resistor is connected to the common ground line and the cathode of the diode.

  Furthermore, the constant voltage circuit and the drive element may be mounted so as to protrude from the outer edge of the head substrate.

  The plurality of recording elements are electrothermal transducers that generate thermal energy.

  According to another invention, a recording head using the head substrate having the above-described configuration is provided.

  Preferably, the recording head is an ink jet recording head that performs recording by discharging ink onto a recording medium.

  According to another aspect of the invention, there is provided a head cartridge comprising the ink jet recording head and an ink tank for storing ink to be supplied to the ink jet recording head.

  According to still another aspect of the invention, a recording apparatus that performs recording using the recording head having the above-described configuration or the head cartridge having the above-described configuration is provided.

  Therefore, according to the present invention, the recording element of each block that is time-division driven can be driven by applying a constant current, so that the number of recording elements is very large and the wiring to the recording elements becomes long. Even if the voltage drop that occurs up to the recording element varies depending on the driving conditions, there is an effect that the recording element can always be driven by supplying a certain amount of energy.

  Further, since the constant current can be controlled by an adjustment signal from the outside, it is possible to reduce the margin amount of the voltage applied to the recording element. As a result, the stress on the recording element is reduced and durability is improved. There is also an advantage of improvement.

  Further, by mounting the drive circuit of the recording element and the constant voltage circuit so as to protrude from the outer edge of the head substrate, there is an effect that the substrate width can be shortened.

  Furthermore, since variations in the power supply voltage can be allowed, there is an advantage that adjustment at the time of shipment of the recording head, which has been conventionally performed, is not necessary.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  In this specification, “recording” (sometimes referred to as “printing”) is not only for forming significant information such as characters and figures, but also for human beings visually perceived regardless of significance. Regardless of whether or not it has been manifested, it also represents a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or the medium is processed.

  “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.

  Furthermore, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly in the same way as the definition of “recording (printing)” above. It represents a liquid that can be used for forming a pattern or the like, processing a recording medium, or processing an ink (for example, solidification or insolubilization of a colorant in ink applied to the recording medium).

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

<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) transmits a driving force generated by a carriage motor M1 to a carriage 2 on which a recording head 3 that performs recording by discharging ink according to an ink jet system is mounted. 4, the carriage 2 is reciprocated in the direction of arrow A, and for example, a recording medium P such as recording paper is fed through a paper feeding mechanism 5 and conveyed to a recording position. Recording is performed by ejecting ink onto the recording medium P.

  Further, in order to maintain the state of the recording head 3 satisfactorily, the carriage 2 is moved to the position of the recovery device 10 and the ejection recovery process of the recording head 3 is performed intermittently.

  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.

  Now, the carriage 2 and the recording head 3 can achieve and maintain a required electrical connection by properly contacting the joint surfaces of both members. The recording head 3 applies energy according to a recording signal to selectively eject ink from a plurality of ejection ports for recording. In particular, the recording head 3 of this embodiment employs an ink jet system that ejects ink using thermal energy, and responds by applying a pulse voltage to a corresponding electrothermal transducer in accordance with a recording signal. Ink is ejected from the ejection port.

  Further, in FIG. 1, reference numeral 14 denotes a conveyance roller driven by a conveyance motor M2 to convey the recording medium P.

  In the above-described example, the recording head and the ink cartridge for storing ink are separable. However, as described below, the head cartridge in which these recording head and ink cartridge are integrated is used as the carriage 2. May be installed.

  FIG. 2 is an external perspective view showing an example of the configuration of the head cartridge.

  As shown in FIG. 2, the ink jet cartridge IJC is composed of a cartridge IJCK that discharges black ink and a cartridge IJCC that discharges three color inks of cyan (C), magenta (M), and yellow (Y). These two cartridges are separable from each other and can be detached from the carriage 2 independently.

  The cartridge IJCK includes an ink tank ITK that stores black ink and a recording head IJHK that discharges and records black ink. These cartridges have an integrated configuration. Similarly, the cartridge IJCC includes an ink tank ITC that stores three color inks of cyan (C), magenta (M), and yellow (Y), and a recording head IJHC that discharges and records these color inks. However, these are integrated. In this embodiment, the ink tank is filled with ink.

  Further, as apparent from FIG. 2, the nozzle row for ejecting black ink, the nozzle row for ejecting cyan ink, the nozzle row for ejecting magenta ink, and the nozzle row for ejecting yellow ink are arranged side by side in the carriage movement direction. The nozzle arrangement direction intersects the carriage movement direction.

<Control Configuration of Inkjet Recording Apparatus (FIG. 3)>
FIG. 3 is a block diagram showing a control configuration of the recording apparatus shown in FIG.

  As shown in FIG. 3, the controller 600 includes an MPU 601, a program corresponding to a control sequence to be described later, a required table, a ROM 602 storing other fixed data, a control of the carriage motor M1, a control of the transport motor M2, and a recording. A special purpose integrated circuit (ASIC) 603 that generates a control signal for controlling the head 3, and a RAM 604, an MPU 601, an ASIC 603, and a RAM 604, which are provided with image data development areas and program execution areas, are connected to each other. A system bus 605 for transferring data, and an A / D converter 606 for inputting analog signals from the sensor group described below, A / D converting them, and supplying digital signals to the MPU 601 and the like.

  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.

  Further, reference numeral 620 denotes a switch group, which instructs activation of a power switch 621, a print switch 622 for instructing printing start, and a process (recovery process) for maintaining the ink ejection performance of the recording head 3 in a good state. For example, a recovery switch 623 for receiving a command input from the operator. Reference numeral 630 denotes a position sensor 631 such as a photocoupler for detecting the home position h, a temperature sensor 632 provided at an appropriate location of the recording apparatus for detecting the environmental temperature, and the like. It is a sensor group.

  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 transport motor driver that drives a transport motor M2 for transporting the recording medium P.

  The ASIC 603 transfers drive data (DATA) of the recording element (heater) to the recording head while directly accessing the storage area of the RAM 602 during recording scanning by the recording head 3.

  Next, some examples of the head substrate used in the recording head of the recording apparatus having the above configuration will be described.

  FIG. 4 is a diagram showing the configuration of the head substrate according to this embodiment. In FIG. 4, the same components as those already described in the prior art are denoted by the same reference numerals, and the description thereof is omitted.

  First, the basic configuration and operation of the head substrate will be described.

<Basic configuration>
In addition to the components described with reference to FIG. 11 of the conventional example, the head substrate of this embodiment includes a constant current circuit 113 for setting the applied current (I _set ) of the heater 101 and the GNDH side terminal voltage (V _REF ) of the heater. As in the conventional example, each block is composed of M blocks (N blocks from the first block to the Mth block) each consisting of N bits (that is, N heaters and N power transistors). Composed. In this embodiment, a bipolar transistor is used instead of the conventional MOS transistor.

  In this embodiment, the heater 101 is connected to the power transistor 102 configured in units of N bits so as to correspond to M block × N bit time division driving. The other terminal of the heater 101 is connected to the VH wiring 106 serving as an applied power source. The output side of the power transistor 102 is shared in units of blocks (that is, N units) and connected to one terminal of the constant current circuit 113. The other terminal of the constant current circuit is connected to the GNDH wiring 107, and a voltage source terminal (not shown) that generates a bias voltage, which is another terminal of the constant current circuit 113, when the sense line 114 is pulled out. Connected to. Note that the VH wiring 106 and the GNDH wiring 107 are common wiring from the feeding point 103 to each of the M blocks.

<Operating principle>
Since the power supply wiring is formed in this way, the power supply wiring of the head substrate has a characteristic having a common impedance, and the voltage drop on the VH wiring 106 side and the GNDH wiring 107 side differs depending on the location of the block. Also, the voltage drop varies depending on the number of simultaneously driven bits of the heater. The constant current circuit 113 allows a set current (I _SET ) to flow through the sense line 114 with reference to a reference voltage (V _REF ) referring to the GNDH terminal voltage on the GNDH wiring 107 side.

This set current (I _SET ) is controlled by a bias voltage generated inside the constant current circuit 113. By making the reference voltage of this bias voltage the GNDH terminal voltage, regardless of the voltage fluctuation of the GNDH wiring 107. A constant bias voltage is generated for the GNDH wiring 107, and the circuit operates so as to flow a constant current. Further, such an operation of passing a constant current is not affected by voltage fluctuation of the VH wiring 106. As described above, in this embodiment, voltage fluctuations of the VH wiring 106 and the GNDH wiring 107 are absorbed, and constant current driving is performed so that a constant current flows through the heater 101.

  Next, an example of such driving will be described. The main drive specifications of the head substrate here are as follows.

  Recording width L inch, 4 area parallel drive, M block x N bit time division per area, number of nozzles M block x N bit x 4 area x 2 rows = 8 x M x N, heater resistance value RH, heater applied current IH is there.

  The configuration of the recording head is the same as the configuration shown in FIG. 12 referred to in the conventional example, and the ink supply port 202 is positioned in the central long side direction of the substrate 201, and the ODD side nozzle row 203a is located on both sides so as to sandwich this. And the EVEN side nozzle row 203b, and the heater corresponding to the nozzle and the driver IC 205 for driving the heater are arranged on the side farther from the ink supply port of each nozzle row. When the recording head is driven, the two nozzle rows are divided into four regions of ODD_L, ODD_R, EVEN_L, and EVEN_R and operated simultaneously. Accordingly, the power supply and the control line are individually fed to the four regions, but the feeding points are arranged on the short side 204 and 206 of the board in order to correspond to a configuration in which a plurality of head boards are arranged.

  FIG. 5 is a diagram showing a circuit configuration of one region (N heaters × M blocks) driven by the above-described power supply configuration. In this figure, the same components as those mentioned in the conventional example are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5, each block is provided with a driver IC 205 having an internal configuration in units of N bits.

Then, the heater 101 is connected to one end of a driver IC 205 which is internally configured in units of N bits so as to correspond to M block × N bit time division driving. Further, one constant current circuit 113 is provided in the N-bit driver. The other terminal of the heater 101 is connected to the VH wiring 106. A setting resistor (R _set ) 115 is connected between the constant current circuit 113 and the GNDH wiring 107. The role of this resistor is to set the set current (ISET) under a constant bias voltage as described above. A sense line 114 is connected to the GNDH wiring side of the setting resistor (R _set ) 115. The VH wiring 106 and the GNDH wiring 107 are configured by applying Cu plating to the Al wiring, and form a common wiring from the feeding point 103 to the first to M blocks.

  Since the VH wiring is thus common, the voltage drop on the VH wiring 106 side and the GNDH wiring 107 side differs depending on the location of the block. The voltage drop also differs depending on the number of simultaneously driven bits.

  Here, the resistance and the wiring width of the VH wiring 106 and the GNDH wiring 107 are obtained based on the driving specification described above. A common wiring resistance equivalent to a resistance of 50 Ω for the individual wiring is set so that it can be compared with the conventional example.

Assuming that the individual wiring is a resistance value obtained by bundling M blocks, VH wiring resistance R _{VH //} = R _VH / M and GNDH wiring resistance R _{GNDH //} = R _GNDH / M. If the wiring conditions are the same Al film thickness and Cu film thickness, the wiring width will be the amount excluding the space W _S , so VH wiring width W _{VH //} = W _L M, GNDH wiring width W _{GNDH //} = W _L M, therefore, the width W _{P //} = M of the power supply wiring region _{(W VH // + W GNDH //} ).

This result indicates that the space W _S of the conventional example does not contribute. At this time, the voltage drop due to the wiring resistances R _{VH //} , R _{GNDH //} is maximized at the Mth block farthest from the feeding point 103.

Estimating this, voltage drop ΔV _VH on the VH wiring side = (R _{VH //} / M) × I _H × M = R _{VH //} · I _H , voltage drop on the GNDH wiring side ΔV _GNDH = (R _{GNDH //} / M) × I _H × M = R _{GNDH //} · I _H

Therefore, the voltage value on the GNDH wiring 107 side, that is, the sense line 114 fluctuates at the maximum by R _{GNDH //} · I _H. On the other hand, the VH wiring 106 side has a voltage fluctuation R _{VH //} · I _H and the VH voltage is supplied to the heater 101.

The necessary VH voltage (V _{VH @ CHIP} ) at the feeding point 103 is
V _{VH @ CHIP} = ΔV _VH + ΔV _GNDH + I _H R _H + Constant current drive circuit loss
= I _H (R _{VH //} + R _{GNDH //} + R _H ) + Constant voltage drive circuit loss.

Furthermore, there is a voltage drop in the cable 111 that connects between the VH power supply 110 supplied from the outside and the substrate. When the resistances of the VH side cable 111 and the GNDH side cable 112 are R _c , respectively, the VH power supply voltage (V _VH ) necessary for the VH power supply 110 is
V _VH = V _{VH @ CHIP} + 2R _C・ I _H・ M
It becomes.

  Next, the driver IC 205 that is driven at a constant voltage will be described based on the VH wiring 106 and the GNDH wiring 107 designed as described above.

  FIG. 6 is a block diagram showing a functional configuration of a driver IC composed of Y blocks × N bits for constant current driving.

  As shown in FIG. 6, this driver IC has a configuration in which Y blocks 312 of N bits are provided. Outside these Y blocks, recording data and a selected bit address are received by a DATAIN signal. A shift register 301 that receives and rearranges, a latch 302 that stores recording data, a latch 303 that stores a selected bit address, an AND gate 304 that performs a logical product with an applied pulse signal (_HE), and a block based on the selected bit address N line decoder 305 for selecting one bit of the data, AND gate 306 for obtaining the logical product of the recording data and the selected bit, and a bias voltage for finely adjusting the bias voltage in the constant current circuit for controlling the heater application current. Receives data as an SDI signal and outputs the corresponding bias control current. D / A converter 307 to the shift register 309 and latch 308 to input store data (bias voltage adjustment data) corresponding to the bias voltage is provided.

  Data is stored in the shift register 301 in the order of the recording data and the selected bit address according to the clock signal (CLK1). Therefore, when a set of recording data and a selected bit address are input, the register 310 stores the recording data and the register 310 stores the selected bit address.

  Here, the operation of the driver IC having such a configuration will be described.

  First, the output of the register 310 of the shift register 301 storing the recording data is taken into the latch 302 at the input timing of the latch signal (_LT), and the AND gate 304 applies the logical product to the pulse width signal (_HE) applied to the heater. Then, the calculation result is output. Hereinafter, this calculation result is referred to as a segment signal.

  On the other hand, the output of the register 311 storing the selected bit address is taken into the latch 303 at the input timing of the latch signal (_LT), and the selected bit signal is output by the N line decoder 305. Hereinafter, this signal is referred to as a common signal.

  Next, the segment signal and the common signal are input to the AND gate 306. Thus, the AND gate 306 forms a matrix circuit. In this way, a matrix is constituted by the segment signal which is the arrangement of the recording data and the common signal which is the arrangement of the selection bit signal, and the logical product of both is generated to generate the time division drive signal. This is a signal for selecting any one heater (1 bit) in each block and energizing the selected heater for driving. The Y N-bit drivers 312 receive this time-division drive signal as a recording on / off signal, and drive the heater in a time-division manner.

On the other hand, the N-bit driver 312 includes a circuit that receives a bias control current from the D / A converter 307 and generates a bias voltage of a constant current circuit. Each block includes output terminals O _{i1 to} O _iN (i = 1, Y), a connection terminal REXi (i = 1, Y) of a setting resistor (R _set ) 115, and a connection terminal GNDHREFi (i = 1, Y).

  The serial data signal (SDI) transferred from the external control circuit is first stored in the shift register 309 and is taken into the latch 308 at the input timing of the latch signal (_LT2). Then, the D / A converter 307 generates a bias control current corresponding to the fetched SDI signal and outputs it to each block. Note that the resolution of the D / A converter 307 may be determined according to the range and accuracy of fine adjustment of the current flowing through the heater 101.

  Next, based on the heater drive signal from the matrix formed by the common signal and segment signal input to the AND gate 306, the bias control current from the D / A converter 307, and the GNDH voltage fluctuation from the sense signal line. The internal configuration and operation of the N-bit driver 312 that is driven at a constant current will be described.

  FIG. 7 is a circuit diagram showing an internal configuration of an N-bit driver 312 that is driven at a constant current.

As shown in FIG. 7, the N-bit driver 312 generates n power transistors Q1 to Qn that drive the heater, a transistor Q (n + 1) that drives at a constant current, and a bias voltage V _BIA of the power transistor Q (n + 1). It comprises diodes D1 to D3 and transistors Q (n + 2) to Q (n + 4).

The N-bit driver 312 is externally provided with a setting resistor R _set 115 for setting the setting current I _set and a power transistor Q (n + 5). Then, the transistors Q (n + 2) to Q (n + 4) and the power transistor Q (n + 5) constitute a constant current circuit that supplies the bias current I _BIA to the diodes D1 to D3. The bias current (I _{D / A} ) is set and controlled by the D / A converter 307.

The n heaters 101 are connected to the output terminals O1 to On of the power transistors Q1 to Qn, and the other terminals of the heaters are commonly connected to the VH wiring 106. On the other hand, the emitters of the power transistors Q1 to Qn are connected in common and connected to the collector of the power transistor Q (n + 1) of the constant current circuit. The emitter of the power transistor Q (n + 1) is output to the outside of the N-bit driver 312 via the connection terminal REX, is connected to the setting resistor (R _set ) 115, and its base is connected to the anode of the diode D1.

The diodes D1 to D3 are connected in series as shown in FIG. 7, and the output from the cathode of the diode D3 is taken out to the outside via the connection terminal GNDHREF and connected to the sense line 115. The diodes D1 to D3 receive a constant current from the transistor Q (n + 2) of the constant current circuit composed of the power transistors Q (n + 2) to Q (n + 5) and receive the bias voltage (V _BIA ) of the power transistor Q (n + 1). As it occurs, it is pulled out via the V _BIA terminal for monitoring the bias voltage (V _BIA ).

  Further, in the constant current circuit constituted by the power transistors Q (n + 2) to Q (n + 5), a first current mirror circuit is constituted by the transistors Q (n + 2) and Q (n + 3) and further controlled. Current mirror circuit is composed of transistors Q (n + 4) and Q (n + 5).

A D / A converter 307 is connected to the second current mirror circuit and supplies a bias control current I _{D / A.} The second current mirror circuit is also provided for other blocks, and the same current mirror circuit is configured in each block and is controlled in common by one D / A converter 307. The D / A converter 307 receives the reference voltage VREF and the bias voltage adjustment data from the outside as described above.

  Note that although the voltages of the VH wiring 106 and the VH terminal are the same, the VH terminal serves as a power source for a constant current circuit composed of the power transistors Q (n + 2) to Q (n + 5), and therefore the VH wiring 106 having a large voltage fluctuation. Is given through a separate terminal. Similarly, although the GNDH terminal has the same voltage as that of the GNDH wiring 107, the GNDH terminal 107 serves as a power source for a constant current circuit composed of power transistors Q (n + 2) to Q (n + 5). It is given separately.

In the N-bit driver 312 of this embodiment, the bias voltage V _BIA is generated with reference to the GNDH wiring 107. The remaining voltage obtained by subtracting the base-emitter voltage (V _be ) of the power transistor Q (n + 1) from the bias voltage (V _BIA ) is applied to the setting resistor (R _SET ) 115 and a setting current (I _SET ) flows. . That is, the set current (I _SET ) can be controlled by the set resistor (R _SET ) 115 and the bias voltage (V _BIA ) so that a desired heater applied current (I _H ) is obtained.

The set current (I _SET ) is
I _SET (= I _H ) = (V _BIA −V _be ) / R _SET
It becomes.

In this embodiment, since the bias voltage (V _BIA ) is generated by the forward voltage of the diode, the voltage applied to the setting resistor (R _SET ) has a substantially fixed value. Accordingly, the set current (I _SET ) is substantially set by the set resistor (R _SET ). The bias voltage (V _BIA ) varies slightly depending on the bias current (I _BIA ), temperature, and current amplification factor of the power transistor Q (n + 1). When stable and uniform driving is required, control according to the (I _BIA -V _BIA ) characteristic of the constant current circuit is performed with the bias control current (I _{D / A} ) from the D / A converter 307.

Since the constant current circuit composed of the power transistors Q (n + 2) to Q (n + 5) has a current mirror configuration, a relationship of bias current: I _BIA = I _{D / A} is established.

In this embodiment, the diode has been described as an element for generating the bias voltage (V ^BIA ). However, this element may be replaced with a resistor. When a resistor is used, a wide bias voltage (V _BIA ) can be obtained with one element. However, since the amount of fluctuation of the bias voltage (V _BIA ) increases according to the base current of the power transistor Q (n + 1), control according to the (I _BIA −V _BIA ) characteristic of the constant current circuit is indispensable.

Next, when the VH voltage (V _{VH @ IC} ) necessary for operating this constant current drive circuit is estimated,
V _{VH @ IC} = R _H I _H
+ Voltage between collector and emitter of power transistor Q1 (Vce)
+ Power transistor Q (n + 1) collector-emitter voltage (Vce)
+ R _SET I _H
It becomes.

Here, the loss voltage (V _LOSS ) in the constant current drive circuit is
V _LOSS = Vce of Q1 + Vce of Q (n + 1) + R _SET I _H
It becomes.

The Vce of Q (n + 1) is 0. It is several V or more and varies according to V _{VH @ IC} . In other words, it absorbs V _{VH @-over} voltage of minus the required voltage of (R _H I _H + Q1 of Vce + R _SET I _H) from _IC.

Again, the required VH voltage (V _{VH @ CHIP} ) at the feed point 103 is
V _{VH @ CHIP} = ΔV _VH + ΔV _GNDH + I _H R _H + V _LOSS
It becomes.

Estimating the final VH power supply voltage (V _VH )
V _VH = V _{VH @ CHIP} + 2R _C I _H M
It becomes.

  Next, following the conventional example, give specific specifications and constants to the above formula and compare with the conventional example.

The conditions here are 88 blocks × 40 bits time-division drive, heater resistance value R _H = 230Ω, heater application current I _H = 80 mA, common wiring resistance equivalent to individual wiring 50Ω, and cable resistance R _C = 0.1Ω. . Under such conditions, the following results were obtained with the head substrate according to this example. That is,
VH wiring resistance: R _{VH //} = 50Ω / 88 lines = 0.568Ω / bit,
GNDH wiring resistance: R _{GNDH //} = 50Ω / 88 lines = 0.568Ω / bit,
VH wiring width: W _{VH //} = 10 μm × 88 lines = 0.88 mm,
GNDH wiring width: W _{GNDH //} = 10 μm × 88 lines = 0.88 mm,
Power wiring area width: W _{P //} = 88 (0.88 mm + 0.88 mm)
= 1.76 mm.

This is half of W _P = 3.52 mm of the conventional example, which is smaller than the width dimension of the short side of the driver IC of 2.5 mm, and achieves efficient wiring with “power supply wiring area width <driver IC width”. ing. The substrate width is 1.76 mm for the ODD side nozzle row and 1.76 mm for the EVEN side nozzle row, and is slimmed to a total of 3.56 mm. This slimming is because, as described above, the wiring is eliminated from the space W _S = 10 μm, which was in the conventional example.

Next, an estimate of the VH power supply voltage (V _VH ) is shown.

Voltage drop on the VH wiring side:
ΔV _VH = 0.568Ω × 80mA = 0.045V
Voltage drop on the GNDH wiring side (sense line):
ΔV _GNDH = 0.568Ω × 80mA = 0.045V
Qce Vce = 0.6V
Voltage drop of set resistor (R _SET ):
Bbe of the bias voltage (V _BIA ) −Q (n + 1) = 1.2V
Here, V _BIA = 0.6V + 0.6V + 0.6V = 1.8V,
Vbe of Q (n + 1) = 0.6V,
R _SET = 1.2V / 80mA = 15Ω
(Note that Q (n + 1) base current is ignored)
VH voltage @ IC:
V _{VH @ IC} = (80 mA × 230Ω) +0.6 V + Q (n + 1) Vce
+ 1.2V = 20.2V + Q (n + 1) Vce
Loss voltage (Vce of Q (n + 1) = 0.6V):
V _LOSS = 0.6V + 0.6V + 1.2V = 2.4V
VH voltage @ feeding point:
V _{VH @ CHIP} = 4V + 4V + (80mA × 230Ω) + 2.4V
= 28.8V
VH power supply voltage:
V _VH = 28.8V + (2 × 0.1Ω × 80 mA × 88 bits)
= 30.2V
Finally, the simulation result of the constant voltage driving circuit of the present embodiment to which the circuit constant designed in this way is applied will be described.

  FIG. 8 is a diagram showing the result of simulating the function realized by the circuit shown in FIG.

  This figure shows the voltage fluctuation obtained by probing the 88th block having the largest power supply voltage fluctuation by giving the applied pulse width of 1 μs and the 88-bit simultaneous driving as the driving conditions.

During the period when the heater is on, the VH voltage waveform and the GNDH waveform have a voltage drop due to the current flowing through the power supply wiring path, and VH voltage drop ΔV _VH = 4.2V, GNDH voltage drop ΔV _GNDH = 4.4V. This is almost the same as the estimate in the design example described above.

At this time, the heater application current (I _H ) is I _H = 80 mA.

The GNDH voltage drop (ΔV _GNDH ) is also a voltage fluctuation of the sense line 104, and this fluctuation voltage 4.4V maintains a constant value in conjunction with the reference voltage of the bias voltage V _BIA generated inside the block. As a result, the set current (I _set ) is constant and the heater is driven at a constant current.

  As shown in the simulation results, it can be seen that a desired current flows through the heater even though the power supply voltage fluctuates by several volts. In addition, the fact that the desired current flows through the heater even though the VH voltage and the GNDH voltage fluctuate greatly means that the voltage variation of the VH power supply 106 can also be tolerated. No longer need it.

  Next, simulation results when the number of simultaneously driven bits is changed, that is, when the load is changed will be described.

  FIG. 9 is a diagram showing a result of simulating a function realized by the circuit shown in FIG. This figure shows the voltage fluctuation obtained by probing the 88th block having the largest power supply voltage fluctuation by giving 44 bits simultaneous driving as the driving condition.

While the heater is on, the VH voltage waveform and the GNDH waveform have a voltage drop due to the current flowing through the power supply wiring path, and VH voltage drop ΔV _VH = 2.4V, GNDH voltage drop ΔV _GNDH = 2.4V. It has become.

At this time, the heater applied current (I _H ) is almost equal to I _H = 80 mA.

  As shown in the simulation result, it can be seen that a desired current flows through the heater even if the load fluctuates. This means that the parasitic resistance matching design including control and variation management in which the pulse width is changed according to the number of simultaneously driven bits described in the pulse width correction of the conventional example and variation management is not required. .

  Therefore, according to the embodiment described above, it is possible to drive with an applied voltage in which the margin amount is greatly reduced by absorbing fluctuations and variations in the power supply system by the driver IC and eliminating the fluctuation factor to the heater. Thereby, the stress to the heater can be reduced, and the durability of the recording head can be improved.

  Although the present invention allows fluctuations and variations in the power supply system, since control is performed so that a constant current is applied to the heater, it is not possible to cope with variations in the resistance value of each heater. Therefore, when the recording head using the head substrate according to this embodiment is driven at a constant current, as proposed in Patent Document 3, a dummy heater formed by the same process as the discharge heater built on the substrate. Referring to the resistance value, the pulse width that is the application time is adjusted according to the reference value and optimized driving, or as proposed in Patent Document 4, the power transistor that drives the heater is turned on. For resistance variation, it is preferable to refer to the ON resistance value of the dummy power transistor formed by the same process as the power transistor built on the substrate and adjust the pulse width according to this reference value to optimize driving.

  In the first embodiment, the example in which the driver IC is mounted on the head substrate has been described. Here, an embodiment of overhang mounting will be described in order to further reduce the cost of the substrate and further reduce the substrate width.

  Overhang mounting is a mounting in which the driver IC is joined near the edge of the board and the driver IC protrudes from the outside of the board. The space required for mounting the driver IC and VH wiring is reduced, and the board is slimmed. I try to plan.

  FIG. 10 is a diagram showing the appearance of overhang mounting of the driver IC according to this embodiment.

  In FIG. 10, the same components as those described in FIG. 12 of the conventional example are denoted by the same reference numerals, and the description thereof is omitted.

  The head substrate 201 of this embodiment has a configuration in which the mounting space for the driver IC 205 and the VH wiring are omitted from the head substrate configured to supply power from the short side of the substrate described in FIG. As can be seen by comparing FIG. 10 and FIG. 12, in this embodiment, the driver IC 205 is provided so as to protrude from the head substrate 201, and a flexible printed cable (hereinafter, FPC) 207 is connected to one end of the protruding position of the driver IC 205. Then, a control line and a VH power line are connected to the driver IC 205 via the FPC 207.

  A printed circuit board 208 is connected to the other end of the FPC 207, and a control line and a VH power line are connected to the printed circuit board 208. Note that power is supplied to the GNDH wiring formed on the head substrate 201 at both ends 204 and 206 on the short side of the head substrate 201 by connecting the printed circuit board 208 and the head substrate 201 via the FPC 207. In addition, the head substrate of this embodiment is divided into four regions of ODD_L, ODD_R, EVEN_L, and EVEN_R and is driven simultaneously as in the head substrate shown in FIG.

  Further, the components and operation of the recording head using the head substrate according to this embodiment are the same as those of the first embodiment, but the driver IC 205 and the GNDH wiring are provided on the head substrate of this embodiment as compared with the first embodiment. Since there is no substrate, the substrate width is reduced accordingly.

Estimating the slim width in the substrate width direction of ODD_L for one side with the connection pad space with the driver IC 205 being 0.2 mm,
Slim width @ one side = GNDH wiring width (0.88 mm) −connection pad (0.2 mm) = 0.68 mm. Therefore, when the ODD nozzle row side and the EVEN nozzle row side are combined and viewed as the whole substrate, the thickness is reduced by 1.36 mm.

  On the other hand, the GNDH wiring is commonly connected to the FPC 207 and the printed circuit board 208 side.

With such a configuration, the VH wiring can be wired with less restrictions on the wiring width and thickness, so that the wiring resistance can be significantly reduced as compared with the first embodiment. When the wiring length is Cu wiring, thickness 12 μm, width 1 mm, and wiring length 152.4 mm in region ODD_L, the GNDH wiring resistance is GNDH wiring resistance = resistivity (1.69 × 10 ⁻⁸ ) × wiring length (152.4 mm) / (Thickness: 12 μm × width: 1 mm) = 0.214Ω.

The voltage drop (ΔV GNDH ) in the GNDH wiring is
ΔV _GNDH = GNDH wiring resistance (0.214Ω) × (80 mA × 88 bits) = 1.5V
Thus, the GNDH wiring voltage drop (ΔV _GNDH ) is changed from 4 V to 2.5 V in the first embodiment.

Therefore, the VH power supply voltage (V _VH ) is
V _VH = VH power supply voltage (30.2V) of Example 1−2.5V = 27.7V
It becomes.

  Therefore, according to this embodiment, by combining the overhang mounting of the driver IC and the constant voltage driving circuit described in the first embodiment, it is possible to achieve both further slimming of the head substrate and reduction of the power supply voltage.

  In the embodiment described above, the ink jet recording head using the heat energy by the heater has been described. However, the present invention is not limited to this, and for example, a thermal using a heater for the recording element. It can also be applied to recording heads.

  Furthermore, in the above embodiments, the liquid droplets ejected from the recording head have been described as ink, and the liquid stored in the ink tank has been described as ink. However, the storage is limited to ink. It is not a thing. For example, a treatment liquid discharged to the recording medium may be accommodated in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

  The above embodiment includes means (for example, an electrothermal converter or a laser beam) that generates thermal energy as energy used to perform ink ejection, particularly in the ink jet recording system, and the ink is generated by the thermal energy. By using a system that causes a change in the state of recording, it is possible to achieve higher recording density and higher definition.

  In the above embodiment, the serial scan type inkjet recording apparatus has been described as an example. However, the present invention is not limited to this, and inkjet recording using a full line recording head having the maximum width of a recordable recording medium. The present invention can be effectively applied to an apparatus. As such a recording head, either a configuration satisfying the length by a combination of a plurality of recording heads or a configuration as a single recording head formed integrally may be used.

  In addition, even the serial scan type as in the above-described embodiments is mounted on the recording head fixed to the apparatus main body or the apparatus main body so that the electrical connection with the apparatus main body and the ink from the apparatus main body The present invention is also effective when an exchangeable cartridge type recording head that can be supplied is used.

  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 a cross-sectional view of an ink jet recording apparatus that is a typical embodiment of the present invention. It is an external appearance perspective view which shows an example of a structure of a head cartridge. FIG. 2 is a block diagram illustrating a control configuration of the recording apparatus illustrated in FIG. 1. FIG. 3 is a diagram illustrating a configuration of a head substrate according to the first embodiment. It is a figure which shows the circuit structure of one area | region (N heaters x M blocks). FIG. 3 is a block diagram showing a functional configuration of a driver IC composed of Y blocks × N bits for constant voltage driving. 3 is a circuit diagram showing an internal configuration of an N-bit driver 312 that is driven at a constant voltage. FIG. It is a figure which shows the result of having simulated the function implement | achieved by the circuit shown in FIG. It is a figure which shows the result of having simulated the function implement | achieved by the circuit shown in FIG. It is a figure which shows the external appearance of the overhang mounting of the driver IC according to Example 2. It is a figure which shows the structure of the drive circuit of the recording head of the conventional general thermal inkjet system. FIG. 3 is a diagram illustrating a power feeding configuration to a substrate of a recording head that is time-division driven. FIG. 13 is a circuit diagram showing an example of power supply wiring in the ODD_L region shown in FIG. 12. It is an external view which shows an example of a board | substrate.

Explanation of symbols

3 Recording head 101 Heater 102 Power transistor 103 Feed point 106 VH wiring 107 GNDH wiring 108 Control circuit 109 ON / OFF signal 110 VH power supply 111 VH side cable 112 GNDH side cable 113 Constant current circuit 114 Sense line 115 Setting resistance 201 Substrate 202 Ink Supply port 203a ODD side nozzle row 203b EVEN side nozzle row 205 Driver IC
204, 206 Substrate short side 301 Shift register 302, 303, 308 Latch 304, 306 AND gate 305 N line decoder 307 D / A converter 309 Shift register 310 Register 312 N bit driver 600 Controller

Claims (11)

A head substrate provided with a plurality of recording elements divided into a plurality of blocks for time division driving,
A plurality of drive elements corresponding to each of the plurality of recording elements and driving the recording elements;
A plurality of constant current circuits provided for each of the plurality of blocks, and supplying a constant current to the plurality of recording elements;
A D / A converter that generates a control current based on a reference voltage and an adjustment signal input from the outside;
A first power transistor for collector input of the control current;
A head substrate that controls the value of the constant current. The constant current circuit is:
A second power transistor that commonly connects one end of a plurality of drive elements that drive a plurality of recording elements included in one block, and that collects the common connection end;
A third power transistor constituting a first current mirror circuit with the first power transistor;
A fourth power transistor connected to the collector of the third power transistor;
A fifth power transistor constituting a second current mirror circuit different from the fourth power transistor and the first current mirror circuit;
The head substrate according to claim 1, further comprising: a diode that inputs a collector output of the fifth power transistor as an anode. A resistor connected to the emitter output of the second power transistor for each of the plurality of blocks;
The head substrate according to claim 2, wherein the constant current value is controlled by a voltage generated by the diode and the resistance.   4. The head substrate according to claim 3, wherein a current flowing through the diode is determined by the first and second current mirror circuits.   The head substrate according to claim 3, wherein one end of the resistor is connected to a common ground line and a cathode of the diode.   The head substrate according to claim 1, wherein the constant voltage circuit and the plurality of driving elements are mounted so as to protrude from an outer edge of the head substrate.   The head substrate according to claim 1, wherein the plurality of recording elements are electrothermal transducers that generate thermal energy.   A recording head using the head substrate according to claim 1.   The recording head according to claim 8, wherein the recording head is an ink jet recording head that performs recording by discharging ink onto a recording medium.   A head cartridge comprising: the ink jet recording head according to claim 9; and an ink tank for storing ink to be supplied to the ink jet recording head. A recording apparatus that performs recording using the recording head according to claim 8 or 9 or the head cartridge according to claim 10.

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