Patent Grant
8231195
1. Field of the Invention
The present invention relates to a print element substrate including a plurality of print element arrays in which different numbers of print elements are arrayed, a printhead, and a printing apparatus.
2. Description of the Related Art
A printhead which prints on a printing medium by discharging ink according to a thermal inkjet method includes, as print element building elements in the printhead, heaters formed from heat generation elements. Drivers for driving heaters, and logic circuits for selectively driving the drivers in accordance with print data are formed on a single element substrate of the printhead.
The resolution of thermal inkjet type color inkjet printing apparatuses is increasing year by year. Along with this, the orifice arrangement density of a printhead is set to discharge ink in the range of a resolution of 600 dpi to resolutions of 900 dpi and 1,200 dpi. There is known a printhead having orifices at such high density.
Demand has arisen for reducing graininess at a halftone portion or highlight portion in a gray image and color photo image. To meet this demand, the size of an ink droplet (liquid droplet) discharged to form an image was about 15 pl several years ago, but is recently decreasing to 5 pl and then 2 pl year after year in a printhead which discharges color ink.
A high-resolution printhead in which orifices for discharging small ink droplets are arranged at high density satisfies a user need for high-quality printing when printing a high-quality color graphic image or photo image. However, when not high-resolution printing but high-speed printing is required in, for example, printing a color graph in a spreadsheet, the above-mentioned printhead may not meet the demand for high-speed printing because printing with small ink droplets increases the number of print scan operations.
To achieve even high-speed printing, there has been proposed a printhead which discharges small ink droplets for high-quality printing and large ink droplets for high-speed printing. There have also been known a printhead in which a plurality of heaters are arranged for one orifice to change the discharge amount by these heaters, and a printhead in which a plurality of orifices having different discharge amounts are arranged in one element substrate.
Element substrates having a plurality of orifices for discharging different amounts of ink include an element substrate in which an orifice array (small-droplet orifice array) of orifices for discharging small ink droplets, and an orifice array (large-droplet orifice array) of orifices for discharging large ink droplets are juxtaposed. To achieve high-quality printing at high speed by this element substrate, there is proposed an element substrate in which the orifice arrangement density of a small-droplet orifice array is higher than that of a large-droplet orifice array. An example of this element substrate is one having a large-droplet orifice array in which 600 orifices are arranged per inch (arrangement density is 600 dpi), and a small-droplet orifice array in which 1,200 orifices double in number are arranged per inch (arrangement density is 1,200 dpi). Examples of this element substrate are arrangements disclosed in the U.S. Pat. Nos. 6,409,315, 6,474,790, 5,754,201, and 6,137,502, and Japanese Patent Laid-Open No. 2002-374163.
Recent inkjet printing apparatuses discharge small ink droplets to print a high-quality image. At the same time, these inkjet printing apparatuses need to increase the print speed. Simply forming the same image requires the same ink amount. Thus, if the discharged ink droplet is downsized to decrease the discharged ink amount to ½, the print speed simply decreases to ½.
To discharge the same ink amount in the same time in order to prevent a decrease in print speed, the number of heaters needs to be doubled. However, if the number of heaters is doubled without changing the heater arrangement density, the size of an element substrate in which heaters are arranged increases double or more. In addition to the increase in element substrate size, this also increases the size of the printhead which moves at high speed in the printing apparatus, the size of the printing apparatus, and vibrations and noise. To prevent these, the heater arrangement density needs to be increased.
To stably discharge ink, a stable voltage needs to be applied to heaters. When all heaters are driven concurrently, a large current flows, and the voltage greatly drops owing to the wiring resistance. To solve this, there is a time-divisional driving method of dividing a plurality of heaters on an element substrate into a plurality of blocks, and sequentially driving heaters for the respective blocks time-divisionally to stably discharge ink.
Recent inkjet printing apparatuses adopt a printhead having an element substrate in which a small-droplet orifice array and large-droplet orifice array are juxtaposed, and heaters corresponding to the respective arrays are arranged. Further, these inkjet printing apparatuses achieve both high-speed printing and high-quality printing by selectively driving orifices for discharging small ink droplets and those for discharging large ink droplets. However, to implement both high-speed printing and high-quality printing, the numbers of orifices and heaters integrated on the element substrate need to be increased.
An element substrate including a large-droplet orifice array at an arrangement density of 600 dpi and a small-droplet orifice array with a double number of orifices at a double arrangement density of 1,200 dpi, which are arranged on a single substrate, will be exemplified. In this element substrate, when printing one pixel by one bit, the number of heaters directly equals the number of bits of print data. The data amount necessary for the orifice array at the arrangement density of 1,200 dpi is double the data amount necessary for the orifice array at the arrangement density of 600 dpi. The difference in data amount is directly related to the data transfer speed. Heaters in different arrays can be driven at individual driving frequencies as long as a clock signal is prepared for each print data corresponding to an orifice array. Even when the time-divisional count and data amount differ between orifice arrays, data can be transferred within almost the same time. In a case where orifice arrays at arrangement densities of 600 dpi and 1,200 dpi coexist, data can be transferred within almost the same time by transferring data to the 1,200-dpi orifice array at double the speed of the 600-dpi orifice array.
However, preparing a clock signal line for each print data signal line corresponding to an orifice array increases the number of pads of the element substrate and the number of signal lines between the printhead and the printing apparatus main body. As the numbers of pads and signal lines increase, the apparatus including the element substrate, printhead, and printing apparatus main body becomes bulky.
To prevent this, an element substrate which includes a plurality of orifice arrays at different arrayed densities and performs time-divisional driving employs the following arrangement. More specifically, a common clock signal CLK is used, and the data transfer speed is set proportional to the number of data bits held in a shift register used for transfer. Data is transferred for each orifice array. Thus, the number of data bits which need to be held in the shift register differs between high- and low-density orifice arrays in time-divisional driving. This difference leads to a transfer speed difference. That is, the transfer speed for the high-density orifice array for which the shift register needs to hold a large number of bits decreases. For example, assume that the number of bits in the shift register used for transfer is 6 bits (4 bits for print data and 2 bits for block control data) in a shift register corresponding to a 600-dpi orifice array, and 10 bits (8 bits for print data and 2 bits for block control data) in a shift register corresponding to a 1,200-dpi orifice array. Under this condition, the data transfer speed of the 6-bit shift register complies with that of the 10-bit shift register. Hence, the 6-bit shift register transfers data at 6/10 of the original data transfer speed, decreasing the data transfer speed.
The area of a circuit pattern including a shift register depends on the number of data bits held in the shift register. If the number of bits differs between a shift register corresponding to a high-density orifice array and that corresponding to a low-density orifice array, the area of the circuit pattern also differs between them, decreasing the circuit layout efficiency. Along with recent demand for smaller-size printing apparatuses, more compact printheads are required. Under the restriction on the printhead size, it is necessary to lay out circuits more efficiently.
Accordingly, the present invention is conceived as a response to the above-described disadvantages of the conventional art.
For example, a print element substrate including a plurality of print element arrays in which different numbers of print elements are arranged according to this invention is capable of efficiently laying out circuits, and is capable of efficiently transferring data to each print element.
According to one aspect of the present invention, preferably, there is provided a print element substrate comprising: a first print element array having a plurality of print elements; a second print element array having a plurality of print elements; a first driving circuit which divides the plurality of print elements included in the first print element array into a predetermined number of groups and time-divisionally drives print elements belonging to each group; a second driving circuit which divides the plurality of print elements included in the second print element array into the predetermined number of groups and time-divisionally drives print elements belonging to each group; and a shift register circuit which holds data for driving the print elements belonging to the first print element array, data for driving the print elements belonging to the second print element array, and information for selecting print elements to be driven from print elements belonging to the respective groups of the first print element array and the second print element array.
According to another aspect of the present invention, preferably, there is provided a printhead having the above print element substrate.
According to still another aspect of the present invention, preferably, there is provided a printing apparatus having a carriage to which the above printhead can be attached.
The invention is particularly advantageous since data can be transferred to each print element efficiently and circuits can be laid out efficiently in an element substrate including a plurality of print element arrays in which different numbers of print elements are arranged.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Exemplary embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.
In this specification, the terms “print” and “printing” not only include the formation of significant information such as characters and graphics, but also broadly includes the formation of images, figures, patterns, and the like on a print medium, or the processing of the medium, regardless of whether they are significant or insignificant and whether they are so visualized as to be visually perceivable by humans.
Also, the term “print medium” not only includes a paper sheet used in common printing apparatuses, but also broadly includes materials, such as cloth, a plastic film, a metal plate, glass, ceramics, wood, and leather, capable of accepting ink.
Furthermore, the term “ink” (to be also referred to as a “liquid” hereinafter) should be extensively interpreted similar to the definition of “print” described above. That is, “ink” includes a liquid which, when applied onto a print medium, can form images, figures, patterns, and the like, can process the print medium, and can process ink. The process of ink includes, for example, solidifying or insolubilizing a coloring agent contained in ink applied to the print medium.
Furthermore, an element substrate (substrate for a printhead) in the description not only includes a simple substrate made of a silicon semiconductor, but also broadly includes an arrangement having elements, wires, and the like.
The expression “on a substrate” not only includes “on an element substrate”, but also broadly includes “on the surface of an element substrate” and “inside of an element substrate near its surface”. The term “built-in” in the invention not only includes “simply arrange separate elements on a substrate”, but also broadly includes “integrally form and manufacture elements on an element substrate by a semiconductor circuit manufacturing process or the like”.
<Inkjet Printing Apparatus>
A printing apparatus capable of mounting a printhead including an element substrate according to the present invention will be explained.
In the inkjet printing apparatus (to be also simply referred to as a printing apparatus hereinafter) shown in
The carriage 102 is guided and supported reciprocally along guide shafts 103, which elongates in a main scanning direction, provided to the printing apparatus main body. A carriage motor 104 drives the carriage 102 via a driving mechanism including a motor pulley 105, associate pulley 106, and timing belt 107. Further, the carriage motor 104 controls the position and movement of the carriage 102.
An auto sheet feeder (ASF) 132 feeds printing media 108 separately one by one as a feed motor 135 rotates a pickup roller 131 via a gear. As a conveyance roller 109 rotates, the printing medium 108 is conveyed (sub-scanned) via a position (printing portion) facing the orifice surface of the head cartridge H1000. The conveyance roller 109 rotates via a gear as a conveyance motor 134 rotates. When the printing medium 108 passes through a paper end sensor 133, the paper end sensor 133 determines whether the printing medium 108 has been fed, and finalizes the start position upon paper feed.
The head cartridge H1000 mounted on the carriage 102 is held so that the orifice surface extends downward from the carriage 102 and becomes parallel to the printing medium 108 between the pair of two conveyance rollers.
The carriage 102 supports the head cartridge H1000 so that the orifice arrangement direction of the printhead coincides with a direction perpendicular to the scanning direction of the carriage 102. The head cartridge H1000 discharges liquid from orifice arrays to print.
<Control Arrangement>
A control arrangement for executing printing control of the above-described inkjet printing apparatus will be explained.
Referring to
The operation of this control arrangement will be explained. When a print signal is input to the interface 1700, it is converted into print data between the gate array 1704 and the MPU 1701. Then, the motor drivers 1706 and 1707 are driven. At the same time, the printhead 3 is driven in accordance with the print data sent to the head driver 1705, thereby printing.
<Head Cartridge>
<Element Substrate>
An element substrate according to the present invention will be explained.
Referring to
The clock input terminal 1107 receives clocks CLK by the number of bits of print data stored in the shift register 1104. Data is transferred to the shift register 1104 in synchronism with the leading edge of the clock CLK. Print data DATA for turning on/off each heater 1101 is input from the print data input terminal 1106.
An element substrate in which the number of bits of print data stored in the shift register 1104 is equal to that of heaters and that of power transistors for driving heaters will be explained for descriptive convenience. Pulses of the clock CLK are input by the number of heaters 1101, and the print data DATA is transferred to the shift register 1104. Then, the latch signal LT is input from the latch signal input terminal 1108, and the latch circuit 1103 latches print data corresponding to each heater. The switch 1109 is turned on for an appropriate time. Then, a current flows through the transistor 1102 and heater 1101 via the power supply line 1105 in accordance with the ON time of the switch 1109. The current flows into the GND line 1110. At this time, the heater 1101 generates heat necessary to discharge ink, and the orifice of the printhead discharges ink in correspondence with print data.
A time-divisional driving method will be explained with reference to
For example, an arrangement in which all the heaters of a single heater array are divided into m groups each having N (N=2n: n is a positive integer) heaters will be considered. In this arrangement, N heaters belonging to one group are time-divisionally driven. When time-divisionally driving heaters in the m respective groups, heaters are driven at the same timing across plural groups. Concurrently driven heaters across plural groups will be called a block. Assume that N heaters in one group are driven in N-time division. If the number of heaters in one group equals the time-divisional count, the number of concurrently driven heaters across plural groups is m because the number of groups is m. Thus, the number of blocks is also N.
Data held in the shift register are a “block selection signal” for selecting a heater corresponding to time division, and a “print data signal” in time division. For N-divisional driving, N=2n via the decoder, and signals input to the shift register are an n-bit block selection signal and an m-bit print data signal. The block selection signal from the shift register is input to a decoder 1203, and output as m block selection signals. In
The decoder 1203 receives block control data to generate a block selection signal based on the block control data. Each AND circuit 1201 builds part of the driving circuit of the heater 1101. The AND circuit 1201 is arranged in correspondence with each heater 1101. The number of bits in the shift register 1104 and latch circuit 1103 is n+m bits. In N-time-divisional driving, (n+m)-bit data is input N times, thereby inputting driving signals in one-to-one correspondence with heaters. In other words, in this element substrate, to drive all the heaters of the hater array once, the gate array 1704 outputs (n+m)-bit data formed from print data and block control data N times.
<Method of Manufacturing Element Substrate and Printhead>
A method of manufacturing an element substrate according to the present invention and a printhead including the element substrate will be explained for a part associated with the present invention.
To supply ink to each orifice 1132, an ink supply port 1121, which is a long groove-like through-hole with a surface inclined from the lower surface to upper surface of the element substrate, is formed by anisotropic etching using the crystal orientation of the Si wafer.
The element substrate having this structure can build a head cartridge by connecting the ink supply port 1121 and a channel member for guiding ink to the ink supply port 1121, and combining them with a container which stores ink. Particularly when the head cartridge is configured by combining containers which store inks of a plurality of colors, and element substrates for the respective colors, color printing can be performed using this head cartridge.
<Driving Circuit in Element Substrate>
In the element substrate shown in
Several embodiments of a heater array and shift register in the element substrate according to the present invention will be explained below in detail.
Element substrates in the following embodiments are those for an inkjet printhead. In these element substrates, a plurality of heater arrays each including a plurality of heaters are arranged along the ink supply port 1121. More specifically, each element substrate includes a heater array (first print element array) made up of a relatively large number of heaters serving as print elements, and a heater array (second print element array) made up of a relatively small number of heaters as printing elements. In the following embodiments, both the number of heaters (number of print elements) and the heater arrayed density differ between heater arrays to clarify features of the present invention. However, the present invention is also applicable to a case where the heater arrayed density is equal and only the number of heaters differs between heater arrays.
In an element substrate according to the first embodiment, the number of heaters of a heater array in which heaters are arranged at high density (1,200 dpi) is 32. The number of heaters of a heater array in which heaters are arranged at low density (600 dpi) is 16, which is ½ of the number of heaters of the heater array in which heaters are arranged at high density. These juxtaposed heater arrays are equal in length. The heater array in which heaters are arranged at low density and the heater array in which heaters are arranged at high density are driven by the same time-divisional count. Time-divisional driving uses a common clock and latch signal within the element substrate. In the first embodiment, the number of heaters of the heater array in which heaters (print elements) are arranged at high density is larger than that of heaters of the heater array in which heaters are arranged at low density.
In the element substrate of
The difference in the number of bits between the shift register corresponding to the heater array in which heaters are arranged at low density, and the shift register corresponding to the heater array in which heaters are arranged at high density in the element substrate of
On the other hand, in an element substrate according to the first embodiment, one shift register holds print data and block control data corresponding to a plurality of heater arrays in each of which heaters are arranged at low density.
Referring back to
Similarly, the latch circuit 1103 outputs data D4, D5, D6, and D7 to the respective groups of the heater array L3. A decoder 1203B performs the same operation as that of the decoder 1203A. In the shift register 1104, the first area of bit 0 (b0) to bit 3 (b3) holds print data for the heater array L2. The second area of bit 4 (b4) to bit 7 (b7) holds control data. The third area of bit 8 (b8) to bit 11 (b11) holds print data for the heater array L3. Further, bit 4 (b4) and bit 5 (b5) in the second area hold control data for the heater array L2, and bit 6 (b6) and bit 7 (b7) hold control data for the heater array L3.
The shift register 1104 shown in
The data generation unit 1800 generates print data of 4 bits used in the heater array. Although not described in detail, the data generation unit 1800 generates column binary data when data buffered in the print buffer are raster multilevel data. The data generation unit 1800 buffers print data D0 to D3 and block control data B0 and B1 for the heater array L2 among generated data in a buffer 1800A. The data generation unit 1800 also buffers print data D4 to D7 and block control data B0 and B1 for the heater array L3 in a buffer 1800B.
A latch circuit 1803 latches block control data for the heater array L2. A latch circuit 1805 latches block control data for the heater array L3. A latch circuit 1804 latches print data for the heater array L2. A latch circuit 1806 latches print data for the heater array L3. A data coupling unit 1802 couples outputs from the latch circuits 1803 and 1805. A data coupling unit 1801 couples a total of 12 bits: the print data D0 to D3, print data D4 to D7, and two block control data B0 and B1.
The transfer unit 1900 includes a transfer buffer 1900A which buffers data to be transferred to the shift register 1104 in
The shift register 1104 in
In the element substrate according to the first embodiment, a shift register circuit corresponding to a print element array formed from a small number (16) of print elements holds block control data corresponding to each of two print element arrays. When the time-divisional counts of two print element arrays are equal to each other, it is also possible for the two print element arrays to use a common block selection signal based on block control data.
In the element substrate of the second embodiment, as shown in
In the element substrates described in the first and second embodiments, shift register circuits arranged for two print element arrays formed from the same number of print elements are combined into one. However, the present invention is not limited to this. For example, the present invention is also applicable to an arrangement in which shift register circuits arranged for three or more print element arrays formed from the same number of print elements are combined into one. Also in this case, one shift register circuit has one independent data input line.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2008-122774, filed May 8, 2008, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-122774 | May 2008 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5754193 | Elhatem | May 1998 | A |
| 5754201 | Ishinaga et al. | May 1998 | A |
| 6137502 | Anderson et al. | Oct 2000 | A |
| 6293655 | Imanaka et al. | Sep 2001 | B1 |
| 6409315 | Komuro | Jun 2002 | B2 |
| 6431685 | Misumi | Aug 2002 | B1 |
| 6474790 | Kaneko | Nov 2002 | B2 |
| 6966629 | Nakajima et al. | Nov 2005 | B2 |
| 7309120 | Hatsui et al. | Dec 2007 | B2 |
| 7819493 | Hirayama et al. | Oct 2010 | B2 |
| 20020089565 | Lopez et al. | Jul 2002 | A1 |
| 20020118241 | Fujii | Aug 2002 | A1 |
| 20060238558 | Hatasa et al. | Oct 2006 | A1 |
| 20070091131 | Hatsui et al. | Apr 2007 | A1 |
| 20070165055 | Hirayama et al. | Jul 2007 | A1 |
| 20070296745 | Kasai et al. | Dec 2007 | A1 |
| 20080100649 | Matsui et al. | May 2008 | A1 |
| 20080111864 | Yamaguchi et al. | May 2008 | A1 |
| 20110012950 | Hirayama et al. | Jan 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 1163828 | Nov 1997 | CN |
| 1543972 | Jun 2005 | EP |
| 2002-374163 | Dec 2002 | JP |
| I249472 | Feb 2006 | TW |
| I253402 | Apr 2006 | TW |
| Number | Date | Country | |
|---|---|---|---|
| 20090278878 A1 | Nov 2009 | US |
