Narrow multi-color ink jet printhead

The present invention relates to an inkjet print head. This solution relates generally to inkjet printing, and more particularly to a narrow, thin-film printhead.

The inkjet printing technique is relatively well developed. Commercial products such as computer printers, graphic plotters and fax machines have been made with inkjet technology for the creation of printed media. A Hewlett-Packard cartridge for the development of inkjet technology is described, for example, in various articles in the HewlettPackard Journal, Vol. 36, No. 5 (May 1985); vol. 39, No. 5 (October 1988); vol. 43, No. 4 (August 1992); vol. 43, No. 6 (Dec. 1992); and Vol. 45, No. 1 (Feb 1994); all these articles are referenced by the present application.

Generally, the ink-jet image is formed by accurately placing, on the print medium, the ink drops emitted by a drop-generating device known as an inkjet printhead. Typically, the inkjet printhead is mounted on a moving carriage that passes over the surface of the print medium and has a controlled ejection of ink drops at a designated time according to the commands of a microcomputer or other controller, the timing of the ejection of ink drops is determined by a pixel pattern of the printed image. .

A typical Hewlett-Packard inkjet printhead includes an array of precision-shaped nozzles in a pinhole plate that is attached to a barrier layer, which is then attached to a thin-film foundation structure that in turn uses heater resistors firing ink and a device to activate resistors . The ink barrier layer defines the ink channels containing the ink chambers disposed over the cooperating ink firing resistors, moreover, the nozzles in the orifice plate are coaxially aligned with the cooperating ink chambers. The areas of the ink drop generators are formed by the ink chambers, by a portion of the thin-film foundation structure and a portion of the orifice plate that is adjacent to the ink chambers.

The thin-layer foundation structure typically consists of a substrate, such as silicon, on which various thin layers are formed that form the thin-film ink firing resistors, a device for activating the resistors, and interconnection with contact pads that are made to provide external electrical connection. to the print head. The ink barrier layer is typically made of a polymeric material that is applied as a dry film to the thin-film foundation structure, and is designed to be light-defined and curable both by ultraviolet (UV) rays and thermally. In an inkjet-print head with a feed groove design, ink is supplied from one or more ink tanks to the different ink chambers through one or more feed grooves formed in the substrate.

An example of the physical positioning of the apertured plate, inkjet barrier layer, and thin-layer foundation structure is illustrated on page 44 of the previously cited HewlettPackard Journal, February 1994. Further examples of inkjet printheads are cited in US Pat.

Considerations for thin-film inkjet printheads include the problem of increased substrate size and / or increased substrate brittleness using more ink drop generators and / or feed grooves. Accordingly, there is a need for an inkjet printhead that is compact and has a large number of ink drop generators.

The present invention relates to an inkjet printhead comprising a printhead substrate with a plurality of thin-film layers, characterized in that it has three adjacent columnar arrays of drop generators formed in the printhead substrate and extending along an elongate region. Each column array of drop generators provides droplets of different color, and has at least 96 drop generators spaced according to a pitch P of the drop generators. In addition, the columnar arrays of the drop generators are spaced at most 1060 micrometers. Wherein the drop generators produce ink droplets having a multi-pass printable droplet volume with a resolution of less than 1 / 2P dpi along the printing axis parallel to the underlying

PL 199 196 B1 area. In addition, three arrays of FET power circuits formed in the printhead substrate respectively adjacent arrays of columnar drop generators.

Preferably, the pitch P ranges from 1/300 inch (0.085 mm) to 1/600 inch (0.042 mm).

Preferably, the drop generators are configured to emit droplets having a droplet capacity ranging from 3 to 7 picoliters. Each of the drop generators includes heater resistors having a resistance of at least 100 ohms.

The printhead further includes grounding bars overlapping the active regions of the FET power circuits.

Each of the FET power supply circuits has an turn-on resistance that is less than (250,000 ohms micrometer²) / A, where A is the area of ​​such a circuit feeding the FET in micrometers². Each of the power circuits of the FETs has an oxide gate thickness of at most 0.08 μτπ (800 Angstroms). Each of the power circuits of the FETs has a gate less than 4 micrometers long.

The printhead includes each of the power circuits for FETs with an on-resistance of at most 14 ohms. Each of the power circuits of the FETs has an turn-on resistance of at most 16 ohms.

The printhead further includes power paths, and the FET power circuits are configured to compensate for the parasitic resistance of the power paths.

The individual turn-on resistances of the FETs are selected to compensate for the variation in the parasitic resistance possessed by the power paths. Each of the FETs is sized to set the on resistance.

Preferably, each of the FET circuits includes drain electrodes, trigger areas, trigger contacts electrically connecting the trigger electrodes to the trigger areas, source electrodes, source areas, source contacts electrically connecting the source electrodes to the source areas, the trigger areas being configured to set the on-resistance of each. from the FET circuits to compensate for the change in parasitic resistance possessed by the power paths. The trigger regions include elongated trigger regions, each of which includes a continuously non-contacting segment having a length that is selected to adjust the turn-on resistance.

Preferably, each of the array of columnar drive FET power circuits is contained within an area having a width of at most 220 micrometers.

Each array of columnar FET power circuits is contained within an area having a width of at most 350 micrometers.

The printhead substrate has a length LS and a width WS, where the ratio LS / WS is greater than 2.7. Preferably, the WS is about 4200 microns, and in a most preferred embodiment, WS is about 3400 microns.

The benefits and features of the present invention will be readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawing.

The subject matter of the invention is illustrated in an embodiment in the drawing, in which: Fig. 1 is a non-scaled, schematic plan view illustrating an arrangement of the ink drop generators and basic selection paths of an inkjet printhead embodying the invention, illustrating the arrangement of the ink drop generators and the inkjet printhead grounding bars of Figs. 1, Fig. 3 is a partially cut-away schematic perspective view of the inkjet-printhead of Fig. 1, Fig. 4 is an uncalibrated, partially cut-away, schematic plan view illustrating the inkjet-printhead of Fig. 1, Fig. 5 is a schematic representation of generalized thin film layers. the foundation structure of the printhead of Fig. 1, Fig. 6 is a partial cutaway plan view, generally illustrating the layout of the layout of a representative field-effect (FET) power circuit and printhead ground bus of Figure 1, Figure 7 is an electrical diagram showing the electrical connections of a heater resistor and a field-effect transistor (FET) power circuit of the printhead of Fig. 1, Fig. 8 is a schematic plan view of representative selection paths of the primary printhead of Fig. 1, Fig. 9 is a schematic plan view illustrating the implementation of the field-effect transistor (FET) power circuit and the printhead ground bus of Fig. 1, Fig. 10 is a schematic, view. a vertical section of the power circuit of the field effect transistor (FET) of Fig. 9, Fig. 11 is a non-scaled, schematic perspective view of a printer in which the printhead of the present invention may be used.

PL 199 196 B1

In the following detailed description as well as in the individual figures of the drawing, the same elements are designated with the same reference numbers.

In fig. 1 - fig. 4, schematically illustrates uncalibrated, schematic, horizontal, and perspective views of an inkjet printhead 100 in which the invention may be applied and which typically comprises (a) a thin-film foundation structure 11 or a wafer containing a substrate such as silicon and having various thin layers. formed thereon, (b) an ink barrier 12 disposed on a thin-layer foundation structure 11, and (c) a plate 13 with apertures or nozzles layered on top of the ink barrier 12.

Thin-film foundation structure 11 comprises an integrated circuit semiconductor wafer which is formed, for example, according to conventional integrated circuit techniques and as schematically shown in Fig. 5, typically comprises a silicon substrate 111a, a field-effect transistor (FET) gate, a dielectric layer 111b, a layer resistor 111c and the first metallized layer 111d. Active devices, such as the field-effect transistor (FET) power circuits described in more detail in this application, are formed on the top of the silicon substrate 111a, in the gate of the field-effect transistor (FET), and in the dielectric layer 111b, which includes a gate oxide layer and polysilicon gates, with the dielectric layer adheres to the resistive layer 111c. The thin-film heater resistors 56 are formed by individually modeling the resistive layer 111c and the first metallized layer 111d. Further, the thin-layer foundation structure comprises a composite passivation layer 111e including, for example, a silicon nitride layer and a silicon carbide (carborundum) layer and a mechanically passivating tantalum layer 111f that at least covers the heater resistors 56. The 111g gold conductive layer covers the 111f tantalum layer.

The ink barrier 12 is formed of a dry film that is hot and pressurized applied to the thin-film foundation structure 11 and is luminous defined to form ink chambers 19 disposed therein over the heater resistors 56 and ink channels 29. The gold contact areas 74, enabling external electrical connections to be connected, are formed in a gold layer at the longitudinally distal opposite ends of the thin-film foundation structure 11 and are not covered by the ink barrier layer 12. For example, the barrier layer material comprises a dry acrylate-based photopolymer film such as like the product called Parad, which is a photopolymer dry film available from EI duPont de Nemours and Company of Wilmington, Delaware. Similar dry films are found in other duPont products, such as a dry film called Riston, or dry films made by other chemical suppliers. The plate with apertures 13 includes, for example, a flat substrate comprised of a polymeric material in which the apertures are formed by laser burn, for example as disclosed in US Patent 5,469,199, which is incorporated herein by reference. The orifice plate can also include a plated metal such as nickel.

As shown in Fig. 3, the ink chambers 19 in the ink barrier layer 12 are most often disposed over the individual heater resistors 56 ejecting ink 56, and each ink chamber 19 is defined by the interconnecting edges or walls of a chamber opening formed in the barrier layer 12. The ink channels 29 are defined by further openings formed in the barrier layer 12 and are integrally connected to the individual ink ejecting chambers 19. The ink channels 29 open towards the feed edge adjacent to the ink feed groove 71 and receive ink from this groove.

The plate with apertures 13 includes holes or nozzles 21 arranged above the individual ink chambers 19, such that each ink-firing heater resistor 56, the associated ink chamber 19, and the respective holes 21 are arranged to form an ink drop generator 40. Each resistor The radiator units have a nominal resistance of at least 100 ohms, such as about 120 or 130 ohms, and may include a segmented resistor as shown in Fig. 9, wherein the heater resistor 56 is comprised of two resistive regions 56a, 56b connected by a metallized region 59. This resistor structure provides a resistance greater than a single resistor region having the same area.

While the disclosed printheads are described as having a barrier layer and a separate aperture plate, it is of particular note that the printheads may be made of a unitary barrier / punch structure that can be made, for example, using a PL 199 196 B1 of a single photopolymer layer which is subjected to a shaping process by multiple exposure.

The ink drop generators 40 are arranged in columnar arrays or groups 61 along reference axis L and are spaced transversely spaced apart or transversely to reference axis L. Heater resistors 56 of each group of ink drop generators are typically aligned along reference axis L and have a predetermined spacing of centers or nozzles along the pitch P along the reference axis L. The nozzle spacing P may be 1/600 inch (0.042 mm) or greater, e.g., 1/300 inch (0.084 mm). Each column array 61 of ink drop generators includes, for example, 96 or more ink drop generators (i.e., at least 96 ink drop generators).

For illustrative purposes, the thin-film foundation structure 11 may be rectangular in which its opposing edges 51, 52 are longitudinal edges of length LS, while the longitudinally spaced opposing side edges 53, 54 are equal to its width or the lateral dimension WS which is less than LS length of the thin-layer foundation structure 11. The longitudinal extent of the thin-film foundation structure 11 is equal to the edges 51, 52, which may be parallel to the reference axis L. In practice, the reference axis L can be aligned, which is usually the case, along the axis of advancement of the carrier. For convenience, the longitudinally separated ends of the thin-film foundation structure will also be designated by the reference numerals 53, 54 used to refer to the edges at those ends.

While the ink drop generators 40 of each column array 61 of the ink drop generators are illustrated as being substantially collinear, it is of particular note that some of the ink drop generators 40 of the ink drop generator pattern may be slightly off the centerline of the column, for example to compensate for firing delay. .

While each of the ink drop generators 40 includes heater resistors 56, the heater resistors are suitably arranged in column groups or arrays that correspond to the columnar arrays of the ink drop generators. For convenience, arrays or groups of radiator resistors will refer to the same reference numerals 61.

The thin-film foundation structure 11 of the printhead 100 of Figs. 1-4 particularly includes three ink feed grooves 71 which are aligned with the reference axis L and are laterally spaced apart from and with respect to the reference axis L. The ink feed grooves 71 they respectively feed the three groups 61 of ink drop generators and, by way of an example to illustrate this, are placed on the same side as the groups of ink drop generators that feed them. In this way, each ink feed slot 71 feeds ink to the entire single feed edge. By way of a specific example, it is shown that each of the ink feed slots supplies ink of a different color than that of the ink provided by the other ink feed slots, such as cyan, yellow, and magenta.

The pitch, or CP spacing, between the column arrays of the ink drop generators is less than or equal to 1060 micrometers (m) (ie, at most 1060 µm). The nozzles of all the columns may be substantially aligned along the reference axis L so that transversely corresponding nozzles lying in the columns are substantially collinear.

The pitch P of the nozzle spacing and the volume of the ink drop generated by the ink drop generators are preferably configured to allow multiple-pass printing that provides a spacing between the droplets smaller than the pitch size P of the nozzle spacing, which is in the range of 0.084mm (1/300 inch) to 0.042 mm (1/600 inch). The droplet volume may be in the range of 3 to 7 pico liters for a dye based ink (as a specific example about 5 pico liters). In addition, the spacing between the droplets along the media axis that is parallel to the reference axis L can range from 0.021 mm (1/1200 inch) to 0.01 mm (1/2400 inch), which corresponds to the droplet resolution range from 1200 dpi to 2400 dpi. Corresponding to the nozzle pitch, the droplet printing range ranges from 1/4 to 1/8 of the nozzle spacing pitch for a 0.084 mm (1/300 inch) pitch or for a droplet pitch of 1/2 to 1/4 of the nozzle pitch pitch for a pitch of 0.042 mm (1/600 inch). Another example would be that the droplet print spacing along the scan axis which is perpendicular to the reference axis L may range from 0.042 mm (1/600 inch) to 0.021 mm (1/1200 inch), which corresponds to the print resolution range. 600 dpi to 1200 dpi along the search axis.

Preferably for an embodiment having three column arrays 61, each having at least 96 ink drop generators having a pitch pitch P of

PL 199 196 B1

0.084 mm (1/300 inch), as a illustrative example, the length LS of the thin-layer foundation structure 11 may be about 11,500 µm and the width of the thin-layer foundation structure may be about 4,200 µm. Another example is the width WS of a thin-film foundation structure may be about 3400 µ ^ ι. Typically, the length to width ratio (ie, LS / WS) of the thin-layer foundation structure may be greater than 2.7.

Correspondingly adjacent and cooperating with the columnar arrays 61 of the ink drop generators 40 are arrays 81 of FET power circuits formed in the thin-film foundation structure 11 of the printheads 100A, 100B, shown schematically in Fig. 6 for a representative columnar array 61 of ink drop generators. Each array 81 of FET drive circuits includes a plurality of FET drive circuits 85 having drain electrodes suitably connected to individual heater resistors 56 via heater resistor leads 57a. Interacting with each array 81 of FET power circuits and interacting with the array of ink drop generators is a columnar ground bus 181 to which the source electrodes of all FET power circuits 85 of the cooperating array of power FETs 81 are electrically connected. Each columnar array 81 of the FET power supply circuits and its associated ground bus 181 lie along the cooperating column array 61 of ink drop generators, and at least longitudinally have an equal area with the interacting column array 61. Each ground bus 181 is electrically connected to at least one contact pad 74 at one end of the printhead structure and to at least one contact pad 74 at the other end of the printhead structure as schematically shown in Figures 1 and 2.

Ground rail 181 and leads of heater resistors 57a are formed in the metallized layer 111d (FIG. 5) of thin-film foundation structure 11, as well as leads of heater resistors 57b, and the drain and source electrodes of the FET power circuits 85 described below in this application.

The FET power circuits 85 of each column array of the power FET power circuits are driven by a cooperating column array 31 of decoder logic circuits 35 that decode address information on an adjacent address bus 33 that is connected to corresponding contact fields 74 (FIG. 6). Address information identifies the ink drop generators that will be supplied with ink firing energy, as discussed below in this application, and is used by the decoder logic 35 to turn on the FET power circuit of the addressed or selected ink drop generator.

As schematically shown in Figure 7, one terminal of each heater resistor 56 is connected via a primary select path to a contact pad 74 which receives the primary ink firing select signal PS. Thus, since the different terminal of each heater resistor 56 is connected to the trigger terminal of the cooperating FET power circuit 85, the ink firing PS energy is supplied to the heater resistor 56 if the cooperating FET power circuit is turned on by the cooperating logic circuit. a decoder 35 which controls it.

As schematically shown in Fig. 8 for a representative columnar array 61 of ink drop generators, the ink drop generators of the columnar array 61 of the ink drop generators may be grouped into four primary groups 61a, 61b, 61c, 61d of adjacent adjacent ink drop generators, and the heater resistors 56 of the individual primary groups are electrically connected to the same, one of the four basic selection paths 86a, 86b, 86c, 86d, such that the ink drop generators of a particular core group are alternately connected in parallel with the same primary ink firing selection signal PS. For the specific example where the number N of the ink drop generators in the columnar pattern is an integer multiple of 4, each core group comprises N / 4 of the ink drop generators. For example, the core groups 61a, 61b, 61c, 61d are arranged in sequence from side edge 53 towards side edge 54.

Figure 8 shows in greater detail the schematic plan view of the primitive select paths 86a, 86b, 86c, 86d for the cooperating columnar array 61 of the drop generators and the cooperating columnar array 81 of the FET power supply circuits 85 (Fig. 6), as for example made by the paths in gold-plated layer 111g (fig. 5), which is above the other layers and is dielectrically separated from the cooperating array 81 of FET powering circuits and ground bus 181. Primary select paths 86a, 86b, 86c, 86d are respectively electrically connected to the four basic groups 61a , 61b, 61c, 61d by resistor terminals 57b (Fig. 8) formed in the metallized layer 111d and interconnect through contacts 58 (Fig. 9) that extend between the base select paths and resistor leads 57b.

The first primitive select path 86a extends longitudinally along the first core group 61a and covers a portion of the leads of the heater resistors 57b (Fig. 9) which are respectively connected to the heater resistors 56 of the first core group 61a and is connected by contacts 58 (Fig. 9). ) with these leads of heater resistors 57b. The second primary select path 86b includes a section that extends along the second core group 61b and covers a portion of the leads of the heater resistors 57b (Fig. 9) which are respectively connected to the heater resistors 56 of the second core group 61b and are connected via contacts 58 to these leads. radiator resistors 57b. The second track 86b includes a distal section that extends along the first primitive select path 86a on the side of the first primitive select path 86a that faces the heater resistors 56 of the first core group 61a. The second primitive select path 86b has an overall L shape with the second section narrower than the first section to pass the first primitive select path 86a that is narrower than the wider section of the second primitive select path 86b.

The first and second primitive select paths 86a, 86b are generally at least of equal longitudinal area with the first and second primitives 61a, 61b, and are respectively connected to individual contact pads 74 disposed on side edge 53 that is closest to the first and second traces. basic choice 86a, 86b.

The fourth primary select path 86d extends longitudinally along the fourth core group 61d and covers part of the leads of the heater resistors 57b (Fig. 9) which are connected to the heater resistors 56 of the fourth core group 61d and is connected via contacts 58 to the leads of the heater resistors 57b. . The third primary select path 86c includes a section that extends along the third core group 61c and covers a portion of the heater resistor leads 57b (Fig. 9) which are connected to the heater resistors 56 of the third core group 61c and is connected via contacts 58 to the resistor leads. radiator 57b. The third primitive select path 86c includes a further section that extends along the fourth primitive select path 86d. The third primitive select path 86c is generally L-shaped with the second section narrower than the first section to circumvent the fourth primitive select path 86d which is narrower than the wider section of the third primitive select path 86c.

The third and fourth primitive select paths 86c, 86d are generally at least of equal longitudinal area with the third and fourth primitives 61c, 61d, and are suitably coupled to individual contact pads 74 disposed in side edge 54 which is closest to the third and fourth core groups. primary path 86c, 86d.

In a characteristic embodiment, the primitive select paths 86a, 86b, 86c, 86d for the column array 61 of ink drop generators overlap the FET power supply circuits and the ground bus interacting with the column array of ink drop generators and are included in an area that has a longitudinally equal area. with a cooperating column pattern 61. Thus, the four base selection paths for the four basic column arrays 61 of ink drop generators extend along the array toward the ends of the printhead substrate. Preferably, the first pair of primitive select paths for the first pair of primitive groups 61a, 61b are disposed at one half of the length of the printhead substrate that is included in the area that extends along this first pair of base groups, while the second pair of primitive select paths for the second. the pairs of base groups 61c, 61d are disposed in the other half of the length of the printhead substrate, which is comprised in the region extending along this second pair of base groups.

For the sake of simplicity, the primitive select traces 86 and an associated ground bus that electrically connect the heater resistors 56 and their associated FET power circuits 85 to the contact pads 74 are collectively referred to as power paths. Also for the sake of simplicity of example, primitive select traces 86 may be thought of as voltage side or non-grounded power paths.

Generally, the parasitic resistance (or turn-on resistance) of each of the power circuits of the FETs 85 is configured to compensate for variations in the parasitic resistance.

To the different power circuits of the FETs 85 through a side path formed by the power paths, so as to reduce variations in the energy supplied to the heater resistors. In particular, the power paths form a side path that introduces a parasitic resistance into the circuits of the FETs that varies with their position in the path, the parasitic resistance of each of the power circuits of the FETs 85 is selected such that the parasitic resistance combination of each from the supply circuits of the FET 85 field effect transistors and the parasitic resistance of the supply paths, which was introduced into the power circuit of the FET, only slightly differentiates one ink drop generator from another. While all the heater resistors 56 have substantially the same resistance, the parasitic resistance of each of the power circuits of the FETs 85 is configured to compensate for the parasitic resistance variation of the cooperating power paths that have entered the various power circuits of the FETs 85. Thus, if substantially equal energies are provided to the contact pads connected to the power paths, substantially equal energies may be supplied to the different heater resistors 56.

Referring in more detail to Figs. 9 and 10, each of the power circuits of the FETs 85 includes a plurality of electrically interconnected fingers of a trigger electrode 87 disposed over the fingers of a trigger area 89 formed in the silicon substrate 111a (Fig. 5) and a plurality of electrically plurality. connected fingers of source electrode 97, mesh or interlaced with trigger electrodes 87, and disposed above the fingers of source area 99 formed in silicon substrate 111a. The fingers of the polysilicon gate 91, which are interconnected at their respective ends, are disposed on the thin gate oxide layer 93 formed on the silicon substrate 111a. A phosphor-silicon glaze layer 95 separates the drain electrodes and the source electrodes 97 from the silicon substrate 111a. A plurality of conductive trigger contacts electrically connect the trigger electrodes 87 to the trigger areas 89, while a plurality of conductive source contacts 98 electrically connect the source electrodes 97 to the source areas 99.

The area occupied by each FET power circuit is preferably small, and the turn-on resistance of each FET power circuit is preferably low, e.g., less than or equal to 14 ohms or 16 ohms (i.e. 14 ohms or 16 ohms at most), requiring efficient power circuits of FETs. For example, the turn-on resistance Ron can refer to region A of the circuit powering the FET as follows:

Ron <(250,000 ohms • micrometers²) / A where, area A is given in micrometers² ^ m²). For example, this may be true for a gate oxide layer 93 having a thickness less than or equal to 0.08 µm (i.e., at most 0.08 µm (800 angstroms), or having a gate length less than 4 µ ^. And also, having a heater resistor resistance of at least 100 ohms, allowing smaller FET circuits to be made, if the heater resistors have a lower resistance, because with a higher heater resistor value, a higher FET turn-on resistance can be tolerated given the energy distribution between parasitic resistors and radiator resistors.

Specifically, the drain electrodes 87, trigger areas 89, source electrodes 97, source areas 99, and polysilicon gate fingers 91 may generally extend perpendicular or transversely to the reference axis L and to the longitudinal area of ​​the ground bars 181. Also, for each FET circuit 85, the area of ​​trigger areas 89 and source areas 99 taken transversely to reference axis L is the same as the area of ​​gate fingers taken transversely to reference axis L as shown in Fig. 6, which defines an area of ​​areas active, taken transversely to the reference axis L. For the sake of simplicity, the finger area of ​​the drain electrode 87, the fingers of the trigger area 89, the fingers of the source electrode 97, the fingers of the source area 99, and the polysilicon gate fingers 91 may be taken as the longitudinal area of ​​these elements as long as the elements are long and narrow like stripes or fingers.

In an illustrative embodiment, the turn-on resistance of each of the FET circuits 85 is individually configured by controlling the elongated area or length of the permanently non-contacting finger segment of the trigger area, where the continuously non-contacting segment is devoid of electrical contacts 88. For example, the permanently non-contacting finger segments the finger segments of the trigger area may begin at the ends of the trigger areas 89 that are farthest from the heater resistor 56. The activation resistance of a particular FET circuit 85 increases with increasing

The length of the continuously non-contacting finger segment of the trigger area is selected to determine the turn-on resistance of a particular FET circuit.

As another example, the turn-on resistance of each FET circuit 85 may be configured by selecting the size of the FET circuit. For example, the extent of the FET circuit taken transversely to the reference axis L may be selected to determine the turn-on resistance.

For a typical embodiment where the power paths for a particular FET circuit 85 are deliberately defined by direct paths to the contact fields 74 at the nearest longitudinally distant ends of the printhead structure, the parasitic resistance increases with the distance from the nearest end of the printhead and the turn-on resistance of the transistor power circuits. field FET 85 decreases (increasing the efficiency of the FET circuit) with the distance from such nearest end, so as to compensate for the increase in parasitic resistance in the supply path. In a characteristic example of permanently non-contacting trigger finger segments of individual FET power circuits 85 that begin at the finger tips of the trigger area and are farthest from the heater resistors 56, the lengths of such segments decrease with distance from the nearest one of the longitudinally distant ends of the printhead structure.

Each ground bus 181 is formed of the same thin metallized layer as the drain electrodes 87 and the source electrodes 97 of the FET circuits 85, and the active areas of each FET circuit are composed of the source and trigger areas 89, 99 and polysilicon gates 91, preferably stretching. below the interacting ground bus 181. This allows the ground bus and the array of FETs to occupy narrower areas, which then allows the fabrication of a narrower, and therefore less costly, thin-layer foundation structure.

Also, in an embodiment where the permanently non-contacting finger segments of the trigger area begin at the finger tips of the trigger area farthest from the heater resistors 56, the extent of each ground bar 181 taken transversely or laterally to the reference axis L and towards the associated heater resistors 56 can be enlarged as the length of the sections of permanently non-contacting trigger fingers is increased, because the trigger electrodes do not need to be extended over such sections of the permanently non-contacting trigger fingers. In other words, the width W of the ground rail 181 can be increased by increasing the degree of overlap with which the ground rail covers the active areas of the FET power circuits 85, depending on the length of the permanently non-contacting trigger area segments. This was achieved without increasing the width of the area occupied by the ground bus 181 and the cooperating array of the FET power circuit 81, as the increase was achieved by increasing the degree of overlap between the ground rail and the active regions of the power circuits of FET 85. Preferably, in any particular FET circuit 85, the ground bar may overlap the active region transversely to the reference axis L with a substantial length of non-contacting trigger region segments.

For a specific example where the continuously non-contacting trigger area segments begin at the finger tips of the trigger area farthest from the heater resistors 56 and where the lengths of the continuously non-touching trigger area segments decrease with the distance from the nearest end of the head structure printing, modulation or variation of width W of ground bus 181 as the length of the permanently non-contacting trigger region segments changes, defines the width W181 of the ground bus, which increases with the approach to the nearest end of the printhead structure, as shown in Figure 9. Although the amount of shared currents increases as the contact areas 74 are approached, this shape advantageously reduces the resistance of the earth bar as the fields 74 are approached.

The resistance of the ground rail may also be reduced by means of transversely spaced portions of the ground rail 181 in longitudinally spaced areas between the decoder logic circuits 35. For example, such portions may be arranged transversely beyond the active areas, over the width of the area in which the decoder logic 35 has been placed. created.

The following parts of the circuitry interacting with the columnar array of ink drop generators may be included in individual regions having the following widths as indicated in Figs. 6 and 8 by reference numerals that allude to width values.

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<td>The areas include:</td><td>WIDTH</td>

<td>Resistor leads 57</td><td>Approx. 95 micrometers (μιτι) or less (W57)</td>

<td>FET circuits 81</td><td>At most 350 μιτ, or at most 220 μιτ, for example (W81)</td>

<td>Decoder logic circuits 31</td><td>Approx. 34 μιτ or less (W31)</td>

<td>Basic Paths 86</td><td>Approx. 290 μm or less (W86)</td>

These widths are measured perpendicular or transverse to a longitudinal area of ​​the printhead substrate that is aligned with the reference axis L.

Referring to Fig. 11, a schematic perspective view of an example inkjet-printing apparatus 20 in which the printheads described above may be used is shown. The inkjet printing device 20 of Fig. 11 includes a chassis 122 surrounded by a housing or shell 124, typically made of molded plastic. The chassis 122 is formed of, for example, a sheet of metal and includes a vertical plate 122a. Sheets of print media are individually fed through the printing zone 125, by an adaptive print media receiving system 126, which includes a tray 128, for storing the print media prior to printing. The print media can be any type of sheet of printable material such as paper, cardboard, transparencies, Mylar and the like, but for simplicity in the illustrated embodiment, paper is used as the print medium. The series of conventional motorized rollers include a drive roller 129, driven by a stepper motor, that can be used to transfer the print medium from the feed 128 to the print zone 125. After printing, the drive roller 129 transfers the printed sheet onto a pair of retractable wing members 130, an exit dryer, which are shown in an extended position ready to receive the printed sheet. The wing members 130 hold the newly printed sheet for a short time above any previously printed sheets still drying on the shelf 132, before rotating backwards as shown by the curved arrow 133 to drop the newly printed sheet onto the shelf 132. The print-medium pick-up system can include a variety of adaptation mechanisms to accommodate different sizes of print medium, including letterhead, official, A-4 envelopes, etc., such as a variable length adjuster arm 134 and an envelope feed slot 135.

The printer of FIG. 11 further includes a printer driver 136 schematically illustrated as a microprocessor disposed on a circuit board 139 attached to the rear side of vertical chassis 122a. The printer driver 136 receives instructions from a management device such as a personal computer (not shown) and controls the operation of the printer, including advance of the print medium through the print zone 125, further controls the movement of the printhead carriage 140 and the output of signals to the ink drop generators 40.

The printhead carriage guide rod 138 has a longitudinal axis parallel to the search carriage axis, the rod being attached to the chassis 122 to support the varying size of the printhead carriage 140 for reciprocating sliding movement or searching along the search carriage axis. The printhead carriage 140 holds the first and second removable ink cartridges with the integral printhead 150, 152 (each of which is sometimes referred to as a pen, printhead cartridge, or cartridge). The ink tanks with integral printhead 150,152 include individual printheads 154,156 which respectively have downward nozzles ejecting ink substantially downward onto a piece of print medium that is in the print zone 125. The ink cartridges with integral printhead 150, 152 are typically attached to the printhead carriage 140 by a ratchet mechanism that includes ratchet levers, ratchet members, or covers 170, 172.

In an exemplary embodiment, the print medium is advanced through the print zone 125 along a medium axis that is parallel to the tangent to a portion of the print medium located below the overlying nozzles of an ink cartridge having an integral print head 150, 152. the axis of the carriage are placed in the same plane as shown in Fig. 11, they should be perpendicular to each other.

PL 199 196 B1

An anti-rotation mechanism on the back of the printhead carriage connects a horizontally disposed anti-rotation bar 185 that is integrally formed with the vertical plate 122a of the chassis 122, e.g., to prevent the printhead carriage 140 from rotating forward about the slider bar. 138.

In the illustrated embodiment, the ink cartridge with integral printhead 150 is a monochrome printing ink cartridge with an integral printhead, while the ink cartridge with integral printhead 152 is a tri-color printing ink cartridge with an integral printhead.

The printhead carriage 140 is driven along a guide bar 138 by an endless belt 158 ​​that may be driven in a conventional manner, the linear encoder strip 159 is used to detect the position of the printhead carriage 140 along the search axis of the carriage, e.g. conventional techniques.

While the above description is illustrative of characteristic embodiments of the invention, various modifications and variations of the present invention can be made by those skilled in the art without departing from the scope and spirit of the invention, which is defined by the following claims.