JP2004314354A - Recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a yield decrease in a manufacturing process of recording heads even when a chip size is increased due to a great increase of the number of heating elements to be set on one substrate. <P>SOLUTION: An inkjet recording head with a plurality of the heating elements, a plurality of driving circuits for driving each heating element, and a logic circuit for selectively operating the driving circuits by a predetermined sequence discharges ink by utilizing a heat energy generated from the heating elements. Each driving circuit is configured to include a plurality of switch elements (T1-T10) connected in parallel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recording head, and more particularly, to an ink jet recording head that discharges ink using thermal energy generated from a heating element.
[0002]
[Prior art]
2. Description of the Related Art As an information output device in a word processor, a personal computer, a facsimile, or the like, a printer that records desired information such as characters and images on a sheet-like recording medium such as paper or film is widely used.
[0003]
Various methods are known as recording methods for printers. Ink jet methods have recently been used because non-contact recording is possible on recording media such as paper, colorization is easy, and quietness is high. It has attracted special attention, and its configuration includes a serial head that mounts a recording head that ejects ink in accordance with desired recording information and performs recording while performing reciprocal scanning in a direction that intersects the feed direction of a recording medium such as paper. The recording method is generally widely used because of its low cost and easy downsizing.
[0004]
As an inkjet method, a method is known in which an electrothermal converter such as a heating element is provided, and bubbles are generated in ink near the heating element by thermal energy to discharge the ink.
[0005]
In a print head of such a type, a driving element for driving a heating element is generally used as a driving circuit for the heating element, a preamplifier for driving the switching element, and a predetermined sequence and print data. A logic circuit for generating a pulse-like drive signal.
[0006]
FIG. 8 is a block diagram showing a configuration of one heating element 802 and its driving circuit. A MOS transistor 801 or a bipolar transistor is used as a switch element. When a MOS transistor is used, a level converter 803 is provided to generate a necessary drive voltage (for example, see Patent Document 1). On the other hand, when a bipolar transistor is used, a current booster is provided to generate a necessary drive current.
[0007]
The driving capability required for the switching element is determined from the relationship between the resistance value of the heating element 802 and the driving current, and the size of the switching element is determined from the specifications of the semiconductor process to be manufactured. For example, when the resistance value of the heating element is 100Ω and the driving current is 100 mA, a driving voltage of 10 V is required, and the current and withstand voltage required for the switching element are 100 mA or more and 10 V. If the switch element is a MOS transistor, and if it has an element size of 10 μm × 1 mm (source / drain electrode width 4.5 μm, gate length 3 μm, gate width 1 mm) in a certain semiconductor process specification, a heating element, a switch element, The area occupied by the switch elements in the silicon substrate chip in which other circuits are formed becomes a large ratio. In the above design example, the occupied area is about 35%.
[0008]
On the other hand, in order to improve the productivity of the printhead, it is an important issue to improve the yield in the process of manufacturing a chip (printhead element base). Various kinds of contamination (particles) are generated at a certain probability in the manufacturing process, and a defect resulting from the contamination is generated, resulting in a defective chip and lowering the yield. In order to improve the yield, it is necessary to reduce the chip size as much as possible, in addition to devising the particles in the manufacturing process, in addition to increasing the chip area, the probability of encountering the particles increases.
[0009]
In particular, the switch element section tends to have a larger area and a higher defective rate than other circuit sections. On the other hand, the drive circuit can be downsized to some extent by miniaturizing the design rules and making the layout efficient.
[0010]
[Patent Document 1]
JP-A-10-034898
[Problems to be solved by the invention]
However, a chip of an ink jet recording head having the above-described heating element is generally configured to include a drive circuit and a heating element on the same substrate, and in this case, an important factor that determines a printing speed. The size and layout of the drive circuit are determined according to the number of nozzles (the number of heating elements) and the nozzle arrangement for determining the resolution. That is, the chip size of the inkjet recording head depends on the number of nozzles and the resolution.
[0012]
As described above, the chip of the ink jet recording head has a different function from that of a general semiconductor chip such as a memory or a CPU, and the drive circuit can be downsized to some extent by miniaturization and efficient layout. It is not a solution to improve the yield in.
[0013]
Further, in recent years, there has been a strong demand for a higher recording speed, and as the number of nozzles, that is, the number of heating elements, has greatly increased, the chip size and the drive circuit area have also increased. Since it is difficult to lower the density, the probability of occurrence of a defective chip tends to increase. In particular, the probability of occurrence of a defect is high in the switch element portion where the chip occupation area ratio is high, which is a main factor that hinders improvement in yield.
[0014]
The present invention has been made in view of the above situation, and even if the number of heating elements provided on one substrate is greatly increased and the chip size is increased, the yield in the manufacturing process of the recording head is reduced. It aims at suppressing.
[0015]
[Means for Solving the Problems]
A recording head according to one embodiment of the present invention that achieves the above object is an inkjet recording head that ejects ink by using thermal energy generated from a heating element,
A plurality of heating elements,
A drive circuit provided for each heating element and driving the corresponding heating element;
A logic circuit for selectively operating the plurality of drive circuits in a predetermined sequence,
Each drive circuit includes a plurality of switch elements connected in parallel.
[0016]
That is, in the present invention, a plurality of heating elements, a driving circuit provided corresponding to each heating element and driving the corresponding heating element, a logic circuit for selectively operating the plurality of driving circuits in a predetermined sequence, In an ink jet recording head that ejects ink using thermal energy generated from a heating element, each drive circuit is configured to include a plurality of switch elements connected in parallel.
[0017]
With this configuration, even when one of the switching elements does not operate normally, the heating element can be driven by another normally operating switching element.
[0018]
Therefore, when a substrate of a recording head is manufactured in a semiconductor manufacturing process, the substrate can be used even if a defect occurs in a part of the switch element portion, so that the number of heating elements provided on one substrate is greatly increased. Therefore, even if the chip size becomes large, it is possible to suppress a decrease in the yield in the manufacturing process of the recording head.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0020]
In the present specification, “recording” (sometimes referred to as “printing”) refers not only to forming significant information such as characters and figures, but also to meaningless or insignificant human perception. Regardless of whether or not the image is exposed, a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or a case where the medium is processed is also described.
[0021]
In addition, the term “recording medium” refers to not only paper used in general recording devices, but also a wide range of materials that can accept ink, such as cloth, plastic films, metal plates, glass, ceramics, wood, and leather. Shall be.
[0022]
Further, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly as in the definition of “recording (printing)”, and when applied on a recording medium, an image or pattern , A liquid that can be used for forming a pattern or the like, processing a recording medium, or treating ink (for example, coagulation or insolubilization of a colorant in ink applied to a recording medium).
[0023]
Further, the term “element substrate” used below does not indicate a simple substrate made of a silicon semiconductor, but indicates a substrate provided with each element, wiring, and the like.
[0024]
Further, the expression “on the element substrate” used in the following description not only indicates the upper side of the element substrate but also the surface of the element substrate and the inside of the element substrate near the surface. In addition, the term "built-in" in the present invention does not mean that individual elements are simply arranged on a substrate, but rather that each element is integrated on the element substrate by a semiconductor circuit manufacturing process or the like. It is shown that it is formed and manufactured.
[0025]
First, a typical overall configuration and a control configuration of a recording apparatus using the recording head of the present invention described below will be described.
[0026]
<Schematic description of the device body>
FIG. 9 is an external perspective view showing the outline of the configuration of an ink jet printer IJRA which is a typical embodiment of the present invention. In FIG. 9, the carriage HC that engages with the spiral groove 5004 of the lead screw 5005 that rotates through the driving force transmission gears 5009 to 5011 in conjunction with the forward and reverse rotation of the drive motor 5013 has a pin (not shown). Then, it is supported by the guide rail 5003 and reciprocates in the directions of arrows a and b. On the carriage HC, an integrated type ink jet cartridge IJC containing a recording head IJH and an ink tank IT is mounted.
[0027]
Reference numeral 5002 denotes a paper pressing plate, which presses the recording paper P against the platen 5000 in the moving direction of the carriage HC. Reference numerals 5007 and 5008 denote photocouplers, which are home position detectors for confirming the presence of the carriage lever 5006 in this area and switching the rotation direction of the motor 5013.
[0028]
Reference numeral 5016 denotes a member that supports a cap member 5022 that caps the front surface of the print head IJH. Reference numeral 5015 denotes a suction device that suctions the inside of the cap, and performs suction recovery of the print head through an opening 5023 in the cap. Reference numeral 5017 denotes a cleaning blade. Reference numeral 5019 denotes a member that allows the blade to move in the front-rear direction. These members are supported by a main body support plate 5018. It goes without saying that the blade is not limited to this form and a known cleaning blade can be applied to the present embodiment.
[0029]
Reference numeral 5021 denotes a lever for starting suction for recovery from suction, which moves with the movement of the cam 5020 which engages with the carriage, and the driving force from the driving motor is controlled by a known transmission mechanism such as clutch switching. Is done.
[0030]
These capping, cleaning, and suction recovery are configured so that desired operations can be performed at the corresponding positions by the action of the lead screw 5005 when the carriage comes to the area on the home position side. If the above operation is performed, any of the embodiments can be applied.
[0031]
<Description of control configuration>
Next, a control configuration for executing the recording control of the above-described apparatus will be described.
[0032]
FIG. 10 is a block diagram showing a configuration of a control circuit of the inkjet printer IJRA. In the figure showing a control circuit, 1700 is an interface for inputting a recording signal, 1701 is an MPU, 1702 is a ROM for storing a control program executed by the MPU 1701, and 1703 is various data (the recording signal and the recording data supplied to the head). Etc.) are stored in the DRAM. A gate array (GA) 1704 controls supply of print data to the print head IJH, and also controls data transfer between the interface 1700, the MPU 1701, and the RAM 1703. Reference numeral 1710 denotes a carrier motor for transporting the recording head IJH, and reference numeral 1709 denotes a transport motor for transporting the recording paper. Reference numeral 1705 denotes a head driver for driving the recording head, and 1706 and 1707 denote motor drivers for driving the transport motor 1709 and the carrier motor 1710, respectively.
[0033]
The operation of the above control configuration will be described. When a print signal enters the interface 1700, the print signal is converted into print data between the gate array 1704 and the MPU 1701. Then, the motor drivers 1706 and 1707 are driven, and the recording head is driven in accordance with the recording data sent to the head driver 1705 to perform recording.
[0034]
In this example, the control program executed by the MPU 1701 is stored in the ROM 1702. However, an erasable / writable storage medium such as an EEPROM is further added, and the control program is changed from a host computer connected to the inkjet printer IJRA. It can be configured to be able to do so.
[0035]
As described above, the ink tank IT and the recording head IJH may be integrally formed to constitute a replaceable ink cartridge IJC. However, the ink tank IT and the recording head IJH may be configured to be separable. Then, when the ink runs out, only the ink tank IT may be replaced.
[0036]
<Description of ink cartridge>
FIG. 11 is an external perspective view showing a configuration of an ink cartridge IJC in which an ink tank and a head can be separated. In the ink cartridge IJC, as shown in FIG. 11, the ink tank IT and the recording head IJH can be separated at the position of the boundary line K. When the ink cartridge IJC is mounted on the carriage HC, the ink cartridge IJC is provided with an electrode (not shown) for receiving an electric signal supplied from the carriage HC side. Is driven to eject ink.
[0037]
In FIG. 11, reference numeral 500 denotes an ink ejection port array. Further, the ink tank IT is provided with a fibrous or porous ink absorber for holding ink.
[0038]
<First embodiment>
As described above, the present invention is directed to an ink jet recording head that ejects ink using thermal energy generated from a heating element, and includes a plurality of heating elements, and a corresponding heating element provided for each heating element. A printhead comprising: a driving circuit to drive; and a logic circuit to selectively operate the plurality of driving circuits in a predetermined sequence, wherein each driving circuit includes a plurality of switch elements connected in parallel. However, the recording head of this embodiment also has the following features.
[0039]
Even when any of the plurality of switch elements does not operate normally, the other switch elements can drive the corresponding heating elements under predetermined conditions.
[0040]
When one switch element does not operate normally, the number of the plurality of switch elements is determined so as to satisfy a predetermined condition. Specifically, the number of switch elements is ten.
[0041]
The switch element is an N-type semiconductor, specifically, an enhancement type NMOS transistor.
[0042]
Hereinafter, the recording head according to the present invention will be described in detail.
[0043]
FIG. 5 is an external view showing the configuration of the recording head according to the present invention. A silicon substrate chip 503 as an element substrate in which a nozzle array 501 and a drive circuit 502 are formed is fixed on a support substrate 505. In the present embodiment, two rows of nozzle rows are arranged, an ODD row and an EVEN row. A heating element and a driving circuit are arranged on the ODD side and the EVEN side, respectively, so as to correspond to the two nozzle rows of the ODD row and the EVEN row.
[0044]
A sub-tank 506 for storing ink to be supplied to the nozzles via the support substrate 505 is provided, and the ink in the sub-tank 506 passes through the ink supply port provided in the chip 503 of the silicon substrate via the support substrate 505 and enters the chip. The ink is supplied to the formed ink flow path. A heating element is formed in the ink flow path, and ink is ejected from a nozzle by energizing and driving the heating element. An ink supply tube 507 is a tube that supplies ink from the ink tank, and a cable 504 supplies a signal and a power supply for a drive circuit and a power supply for a heating element from the apparatus main body.
[0045]
Hereinafter, the configuration of one of the driving circuits on the ODD side and the EVEN side will be described. FIG. 6 is a block diagram showing a configuration of the driving circuit 502.
[0046]
A drive power supply for supplying current is connected to one terminal of each of the 7040 heating elements H1 to H7040, and a MOS transistor as a switching element is connected to the other terminal. The applied signal processed by the preceding AND gate matrix 601 is converted into a voltage amplitude signal for driving the switch element by the level converter 602, and a gate signal is selectively applied to T1 to T7040 to drive the heating element corresponding to the recording data. I do.
[0047]
Here, an enhancement type NMOS transistor is used as a switch element, a driving power supply is 15 V, and a gate signal is a pulse signal having a voltage amplitude of 0 V / 8 V. Here, the switch element is equivalently illustrated by one transistor. The heating elements H1 to H7040 are divided into 44 groups every 160 in the order of their arrangement, and are driven for each group. The AND gate matrix 601 forms a 160 × 44 group for this drive.
[0048]
FIG. 7 is a block diagram showing the configuration of the AND gate matrix 601 in detail. A cell 701 including a heating element (H), a switching element (T), a level converter (LC), and an AND gate (AND) is a matrix wiring composed of segment wirings S1 to S160 and common wirings C1 to C44. Of each. The common line corresponding to the print data is selected in synchronization with the print data of 160 being output in parallel to the segment lines S1 to S160 from the preceding latch 606. The heating elements of the cells satisfying both the conditions of the segment line and the common line are driven.
[0049]
From the viewpoint of the arrangement of the heating elements, 160 heating elements arranged at 44 pitches are simultaneously selected and driven in order from the end according to the recording data. The driving of 160 groups per group is repeated for 44 groups to drive 7040 heating elements on one side. As a whole, the ODD side and the EVEN side are simultaneously driven while being synchronized with each other, so that 14080 heating elements on both sides are driven.
[0050]
FIG. 3 is a diagram showing a layout of heating element and drive circuit blocks formed in the chip 503. Heating element block 302, switch element block 303, level converter block 304, matrix wiring block 305, and shift register block 306 and decoder block 307 are laid out on the ODD side and the EVEN side, respectively, centering on ink supply port area 301. ing.
[0051]
Here, the dimensions in the short side direction of the switch element block 303, the level converter block 304, and the matrix wiring block that occupy most of the chip area are about 1.2 mm, 0.4 mm, and 0.6 mm, respectively. As can be seen from this value, the size of the switch element block 303 is particularly large at 1.2 mm, and when the area ratio is determined, about 40% of the entire chip area excluding the connection pad portion of the cable 504 and the peripheral blank portion having no circuit is removed. Occupy.
[0052]
FIG. 1 is a diagram illustrating a drive circuit for one heating element in the present embodiment. In FIG. 6, the switch element is indicated by one transistor symbol. However, in detail, as shown in FIG. 1, the switch element is configured by a switch element group 101 including ten switch element cells T1 to T10. Each of the switch element cells of the switch element group 101 has a drain terminal connected in parallel to the heating element 103 and a gate terminal connected in parallel to the output of the level converter 104. Switch element cells operate in parallel. That is, a single heating element 102 functions as an aggregate of ten switching element cells connected in parallel.
[0053]
FIG. 2 is a diagram showing a layout of a switch element group on a chip in the present embodiment. The drain electrode and the gate electrode are arranged on both sides in a branch shape with the drain electrode 202 and the gate electrode 201 as a center, and a switch element group 206 including a total of ten switch element cells T1 to T10 is formed. More specifically, for example, T1 has an L-shaped gate electrode, a drain electrode branch on one side, and a source electrode on the other side to form a MOS transistor. Other switch element cells are formed in a similar pattern. Here, the source electrode 203 is shared with the source electrode of the adjacent switch element 208, and the layout is more efficient. This utilizes a matrix driving method in which adjacent heating elements are not driven simultaneously.
[0054]
According to the actual semiconductor process specifications, in the layout of the present embodiment, an NMOS transistor having a drive current of 100 mA, a withstand voltage of 15 V or more, and an on-resistance of 20 Ω or less was designed. 2 mm x 0.0423 mm was obtained.
[0055]
The operation of the switch element group 206 according to the present embodiment when particles are attached to a part of the switch element cells during the manufacturing process and an open failure occurs will be described.
[0056]
It is assumed that an insulating particle has just adhered to the position of the drain electrode in the switching element cell T1, resulting in an open failure. In this case, T1 is in an open state between the source electrode and the drain electrode and is not turned on. A similar situation occurs when a contact failure with the n + region 204 of the drain electrode or the source electrode occurs as another open failure. On the other hand, since the remaining switch element cells T2 to T10 operate normally, the heating element 207 can be driven by nine switch element cells excluding T1.
[0057]
In this case, the driving performance (on-resistance value) is reduced by 10% as compared with the case where no defect occurs, but the driving can be performed without any problem as long as the defect is within a predetermined allowable defect range. In the present embodiment, the allowable amount of defects is set to one switch element cell, and the design is made such that the entire driving capability is 110% of the desired driving capability. That is, as a result of designing with a total gate width of about 2 mm with a driving capability of 110%, the dimensions of the switch element group were 1.2 mm × 0.0423 mm as described above.
[0058]
Next, the operation of the switch element group 206 according to the present embodiment when a short circuit occurs in a part of the switch element cells due to a pattern defect in the manufacturing process will be described.
[0059]
It is assumed that the drain electrode and the source electrode in the switch element cell T1 have a short circuit failure. In the design of the present embodiment, the drain electrode and the source electrode are patterned on one aluminum layer in the metal two-layer structure, and there is a possibility that a short circuit occurs due to particles or the like.
[0060]
In this case, if it is left as it is, the heating element 207 is destroyed due to excessive energization because T1 is always in an ON state. Therefore, a short-circuit point is specified at the stage of the inspection process, and then the laser is blown with a laser. At the time of this fusing, it is desirable that the function of T1 can be restored without causing harm to a portion other than the short-circuited portion. However, this requires high-precision laser control and position detection. Laser fusing often puts stress on the device, deteriorating its characteristics and leading to destruction.
[0061]
In the present embodiment, assuming that the element is destroyed, the fusing process is actively performed to make the short-circuited cell an open defect. Thus, as in the case of the open failure described above, the function of the entire switch element group can be maintained at the expense of one switch element cell.
[0062]
Here, a description will be given of the improvement of the yield accompanying the remedy of a chip in which the above-described defect has occurred. According to the present embodiment, a defect generated in the switch element block 303 occupying 25% of the chip area can be relieved, so that the yield is surely improved. Even with a simple area effect, a yield improvement of up to 40% can be expected.
[0063]
<Second embodiment>
Hereinafter, a second embodiment of the present invention will be described. In the following description, the description of the same parts as those in the first embodiment will be omitted, and the description will focus on the characteristic parts of the present embodiment.
[0064]
In the first embodiment, the enhancement type NMOS transistor is used as the switch element. However, in the present embodiment, a bipolar transistor is used as the switch element.
[0065]
FIG. 4 is a diagram illustrating a drive circuit for one heating element in the present embodiment. In the present embodiment, a switch element cell group 403 including ten switch element cells each including an NPN transistor and a current booster 402 are provided for one heating element 401.
[0066]
Each transistor of the switch element cell group 403 has a collector terminal connected in parallel to the heating element 401 and a base terminal connected in parallel to the output of the current booster 402, and operates in parallel according to a drive signal output from the current booster 402. I do. That is, a single heating element 401 is made to function as an aggregate in which ten switching element cells are connected in parallel.
[0067]
As described above, even when the bipolar transistor is used as the switch element, the same operation as in the first embodiment is performed, and the same effect is obtained.
[0068]
<Other embodiments>
In the above embodiment, the number of switch element cells constituting the switch element cell group corresponding to one heating element is set to 10, but the number of switch element cells constituting the switch element cell group is not limited to this number. Instead, an appropriate number is appropriately selected according to the driving requirements of the heating elements and the like. In this case, it is preferable that the number of switch element cells constituting the switch element cell group is an even number from the viewpoint of layout efficiency.
[0069]
In the first embodiment, an enhancement type NMOS transistor is used as a switch element, and in the second embodiment, an NPN transistor is used. However, the switch element of the recording head of the present invention is manufactured by other semiconductor manufacturing processes. Possible switching elements can also be used.
[0070]
In the above embodiments, the recording head according to the present invention has been described. However, the present invention includes not only the recording head but also an element substrate constituting the above-described recording head and a recording apparatus which performs recording using the above-described recording head. included.
[0071]
In addition to the above, the recording apparatus according to the present invention may include, as an image output terminal of an information processing apparatus such as a computer, an integrated or separate apparatus, a copying apparatus combined with a reader, etc., and a transmission / reception function. It may take the form of a facsimile machine.
[0072]
【The invention's effect】
As described above, according to the present invention, even when one of the switch elements does not operate normally, the heating element can be driven by another switch element that operates normally.
[0073]
Therefore, when a substrate of a recording head is manufactured in a semiconductor manufacturing process, the substrate can be used even if a defect occurs in a part of the switch element portion, so that the number of heating elements provided on one substrate is greatly increased. Therefore, even if the chip size becomes large, it is possible to suppress a decrease in the yield in the manufacturing process of the recording head.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a drive circuit for one heating element according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a layout on a chip of a switch element group according to the first embodiment.
FIG. 3 is a diagram showing a layout on a chip of a block of a heating element and a driving circuit.
FIG. 4 is a diagram illustrating a drive circuit for one heating element according to a second embodiment of the present invention.
FIG. 5 is an external view showing a configuration of a recording head according to the present invention.
FIG. 6 is a block diagram illustrating a configuration of a drive circuit according to the first embodiment.
FIG. 7 is a block diagram showing a configuration of an AND gate matrix in detail.
FIG. 8 is a block diagram showing a configuration of one conventional heating element and its driving circuit.
FIG. 9 is a diagram illustrating an appearance of a printer according to the invention.
FIG. 10 is a block diagram illustrating a control configuration of the printer in FIG. 9;
FIG. 11 is a diagram illustrating an ink jet cartridge of the printer in FIG. 9;

Claims (1)

An ink jet recording head that ejects ink using thermal energy generated from a heating element,
A plurality of heating elements,
A drive circuit provided for each heating element and driving the corresponding heating element;
A logic circuit for selectively operating the plurality of drive circuits in a predetermined sequence,
A recording head, wherein each drive circuit includes a plurality of switch elements connected in parallel.

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