JPS5836465A - Ink jet printer - Google Patents

Abstract

PURPOSE:To provide the titled printer having a large array independent of electric conductivity of ink and a high resolving property and a high by composing an ink holding means of a film body and a substrate and arranging a heating means facing ink through the film body. CONSTITUTION:A part of one surface of a substrate 11 such as sapphire etc. is covered with a metallized film layer 13. A narrow D1 wide A narrow nonconductive strip 14 D1 width and a conductive strip D2 width are provided to make a resistance 16 in a layer 13. About 3OMEGA is suitable as the resistance. Capillary blocks 15 are joined on the surface of the layer 13 and the width of channel 17 is made to correspond to the width of the nonconductive strip 14. An ink storing part 19 is arranged on the back of the block 15 and on the upper part of the substrate 11. Expansion of the bubble made on the resistance 16 makes impulses.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-impact inkjet printer, and more particularly to the configuration of a printhead.

As data processing technology advances, numerous devices have been developed to permanently record output data. Currently, we are busy with non-impact (non-mechanical impact) methods. Among these, the most important one is the inkjet type. This is because the print output can be easily and directly controlled electronically, and it is also contactless, high speed, and particularly suitable for printing on flat paper.

The inkjet method can be classified into the following three basic types. ■Continuous method (applies constant pressure to ink,
(generates ink droplets continuously at a constant speed), ■Electric field control method, ■On-demand method (impulse jet method).

The present invention relates to an on-demand method.

Traditionally, on-demand systems have used piezoelectric crystals to eject ink from an oriice in a narrow cross-section tube. This method is used, for example, in U.S. Patent No. 3.83.
No. 2.579, in which a small cylindrical piezoelectric transducer is affixed to the outer surface of a cylindrical nozzle. Ink is conveyed to the nozzle end by an ink hose connecting the wide end of the nozzle to an ink reservoir.

When the transducer receives an electrical impulse, it generates a pressure wave that accelerates the 'C ink toward the ends of the nozzle. An ink droplet is formed when an ink pressure wave overcomes the surface tension of the meniscus at the small end orifice of the nozzle.

A problem with this piezoelectric inkjet device is related to the relative dimensional mismatch between the piezoelectric transducer and the inkjet orifice. That is, the transducer is generally substantially larger than its orifice, limiting either the minimum separation distance between each jet or the number of jets that can be mounted on a given printhead. Additionally, piezoelectric transducers are relatively expensive to fabricate and are difficult to implement with many existing semiconductor fabrication techniques.
is not compliant.

Another type of conventional on-demand method is U.S. Patent No. 3.17.
No. 4.042, this system utilizes multiple ink-containing tubes. Electrodes within the tubes are in contact with the ink and, in response to the occurrence of a trigger signal, current flows through the ink itself. This current heats the ink with high I2R losses (where ■ is the current value and R is the resistance value of the ink), vaporizes a portion of the ink in the tubes, and causes the ink and ink gas to flow through them. Inject it from the tube.

The main drawbacks of this vapor-type method are that the ink mist is difficult to control since highly conductive inks require large currents to achieve the desired vaporization, and there are also limitations on the conductivity of the ink. This is what happens.

Therefore, the types of ink that can be used are extremely limited.

Despite many years of research into each of the above-mentioned systems, on-demand inkjet technology still has many fundamental problems that must be resolved.

The present invention relates to an on-demand inkjet printer, and the present invention relates to an ink-containing capillary tube having an orifice for ejecting ink and an ink heating mechanism disposed proximate to the orifice (e.g., disposed in or adjacent to the capillary tube). Provided is an inkjet printer having an inkjet printer.

An overview of the operation will be explained. The ink heating section heats rapidly and transfers the energy generated therein to the ink, thereby vaporizing a portion of the ink and generating bubbles within the capillary.

The bubble then creates a pressure wave that propels the ink droplet from its orifice onto a nearby paper surface. By properly selecting the relative position of the ink heating section and the orifice and by closely controlling the energy transfer, the bubbles will be able to move to or near the ink heating section before the ink gas escapes from the orifice. It disappears quickly.

Much of the existing hardware and software used to implement other printer-matrix printing devices can be readily adapted to printers according to the present invention.

Embodiments of the invention are basically divided into two geometric configurations. In a first configuration, ink is ejected from an orifice located at the end of a capillary tube. In a second configuration (the ink capillary essentially defines a plane and the ink is ejected from the orifice in a direction perpendicular to that plane), each of these configurations uses standard electronic manufacturing techniques. It has an advantage over the prior art in that it can be used to produce large pupils.Furthermore, the dimensions of printheads produced using the principles of the present invention are virtually unlimited;
Very large arrays and very high resolutions are possible because there is no need for space-consuming piezoelectric crystals. Furthermore, this technique is independent of the conductivity of the ink used. The present invention will be explained below using the drawings.

FIG. 1 is an exploded perspective view of a print head of an inkjet printer according to an embodiment of the present invention, and FIG. 2 is an overall perspective view after assembly. Reference numeral 11 denotes a substrate, and a portion of one side of the substrate 11 made of sapphire, glass, or an inert composite material (for example, composite gold or coated silicon) is covered with a thin simulated metallization layer 13 . This thin film metallization layer 13 has a narrow non-conductive tube 14 of width DI (~0.1 degrees) and a width D to create a resistor 16 within layer 13.
2 (~about Q, l u+ ) of IJ tube. Approximately 3Ω is suitable as the resistance value. In a typical configuration, resistor 16 is connected to substrate 1
Distance D3 (nominal) from the edge of 1 is approximately Q, I n
+, but generally about 11.05fil (D3<Jo,
25u range). A capillary block 15 is bonded to the top surface of the thin film metallization layer 13 . Capillary block 15 is generally made of glass and has capillary channels 17 with orifices at each end.

Channel 170 width is approximately 0.08JLl, depth is approximately 0.0
8 m, its width corresponds to the width of the non-conductive layer 14 of the metallization layer 13.

Behind the capillary block 15 and above the substrate 11,
A reservoir 19 for holding ink is arranged parallel to the capillary block 15. Channel 7 is the reservoir 1
The ink is drawn from its reservoir by capillary action into the vicinity of the orifice on the opposite side of 9. As seen in FIG. 2, in the completed configuration the printer has two electrodes 23 and 2 attached to the thin film metallization layer 13.
5, and the electrode creates a potential difference of 6 across the resistor 16. FIG. 3 is a cross-sectional view of the inkjet printer shown in FIGS. 1 and 2, showing the relative positions of ink 21, capillary block 15, resistor 16, and printing surface 27. FIG. In operation, the distance D5 between the printer orifice and the printing surface 27 is approximately 0.8 mm.

Figure 4 is a partial cross-sectional view showing the process of ink droplet generation during one cycle of printing operation.
3 and 25, the current through resistor 16 generates Joule heat, heating the ink. and bubble 12 on resistor 16 as shown in FIG. 4a.
create. The bubble continues to rapidly expand in the direction of the orifice, as shown in Figure 4b. However, its expansion is limited by the energy transferred to the ink.

By carefully controlling this total energy and controlling the time distribution of the energy delivered to resistor 16,
Bubbles of various sizes can be formed.

However, it is necessary to control the total energy absorbed by the ink so that it is not so great as to force gas out of the orifice. The bubble begins to deflate toward and above resistor 16 as shown in FIG. 4C, while the forward momentum imparted to the ink by the expansion of the bubble causes an ink droplet to be ejected from the orifice (however, It should be noted that depending on the ink used, the orifice geometry and the applied voltage, one or more subsequent ink droplets are produced that shrink and disappear to near zero. Refilling begins (Figure 4e), while the ink droplet rests on the printing surface. Figure 4f shows the channel filled with ink back to its original position in preparation for the next cycle. Printing is accomplished by continuously applying voltage to resistor 16 in the appropriate sequence. The orifice and printing surface are moved relative to each other to produce the desired printing pattern.

It should be noted that dimensions such as substrate dimensions, capillary block dimensions, and capillary charge dimensions can be varied over a wide range depending on the desired mass, construction materials and technology, droplet size, capillary filling rate, ink viscosity and surface tension, etc. it is obvious.

In addition, compared to the conventional device, the conductivity of the ink is increased by increasing It(
There is no need to balance heat losses or to make the ink conductive.

An essential feature of the invention is that the impulse required to eject an ink droplet from an orifice is created by the expansion of a bubble rather than by a pressure wave provided by a piezoelectric crystal or other element. . Resistor 1
By carefully controlling the energy transfer from 6 to the ink, it is possible to ensure that ink gas does not escape from the oriice along with the ink droplets. The puzzle disappears on its own to prevent ink gas from splattering. Furthermore, it is extremely important to closely control the temporal sequence of energy transfer.

approximately IA with a period of approximately 5 μsec through resistor 16
Although a single square-wave current pulse of 100 mL achieves similar results, such direct methods are generally not applicable to a variety of jet configurations. Additionally, problems arise when it is desired to create larger bubbles (eg, use a more narrow orifice) or to obtain faster droplet ejection rates.

If the pulses are lengthened to impart more energy to the ink, the statistical nature of bubble formation will result in substantial time jitter.

On the other hand, increasing the pulse height to improve the time jitter problem will result in premature burnout of the resistor due to the substantially higher current density required.

Each of the above-mentioned problems is substantially solved by the method shown in FIG. 5 and 6 are waveform diagrams of pulses used for bubble formation. Here, no DC level is required, but the pre-pulse IP is used to preheat the ink near the resistor 16 at a rate low enough to avoid bubble nucleation. A nucleation pulse IN follows the preceding pulse IP. This nucleation pulse IN rapidly heats the resistor 16 close to the heating limit of the ink, ie, to the point where bubbles spontaneously nucleate within the ink. However, the bubble core thus formed grows very rapidly, and its ripening size is determined by the volume of ink heated by the preceding pulse IP.During this bubble growth process, the voltage applied to resistor 16 is The voltage applied is generally attenuated to zero because heat transfer to the ink during this period is less efficient and maintaining the current would cause resistor 16 to heat up too much.

Typically, resistor 16 is approximately 30 Ω and the preceding pulse IP is approximately 0.3 A in magnitude and approximately 40 μsec
The nucleation pulse IN has a width TP of about 5 μsec, and the nucleation pulse IN has a width about IA and a width TN of about 5 μsec. However, these parameters vary over fairly wide ranges, such that the typical ranges encountered in actual operation are:
That is, 0(R(100Ω; 1 o<'rp(100
μsec, O(I P(3A, 0(TN (10
μsec, 0.01 (it is appropriate to consider for IN<5A.

Many other methods for controlling bubble formation can be used as well, such as, for example, Norculus spatial modulation or pulse height modulation. A further method is shown in FIG. In this way, the magnitude of the leading pulse is reduced from an initial value of about 0.5 A to a value of around +1.2 A (the value just before the nucleation pulse starts). The shape of the leading pulse changes over time. This maintains the resistor temperature at a nearly constant temperature, resulting in optimal ink energy distribution prior to nucleation, while at the same time reducing the required nucleation pulse width. At the same time, it increases the reproducibility of nucleation.

FIG. 7A shows an inkjet printer according to another embodiment of the present invention.
FIG. 7B is an exploded perspective view of the print head of the printer. FIG. 7B is a perspective view of the print head shown in FIG. 7A after assembly. The print head shown in both figures has a plurality of oriswises. Itl [l @ Edge Shooter (e
The apparatus consists of a substrate 71 and a capillary block 75 having several ink capillary channels 77 located at the interface between itself and the substrate 71. Typical materials used for substrate 71 include glass, ceramic,
electrical insulators such as coated metal or coated silicon;
On the other hand, the material used for the capillary block 75 is
The ink capillary channel 77 is chosen to be easy to fabricate. For example, as standard, capillary block 75 is made of molded or etched glass. In that configuration, the substrate 71 and the capillary block 75 are, for example,
The C-type can be sealed in a number of ways with epoxy, anodic bonding or sealing glass. Channel spacing D6 and channel width D7 are determined by the desired separation and dimensions of the inkjet. Channel 79 is a reservoir channel that supplies ink to ink capillary channel 77 from an ink reservoir (not shown) at a remote location.

What about the board 71', h? J number of resistors 73 are provided, the position of each resistor corresponding to the bottom of each capillary channel 77. A corresponding number of electrical connections 72 are provided for supplying power to each resistor 73. Resistor 7
3 and electrical connections 72 are formed using standard electronic fabrication techniques such as physical or chemical vapor deposition.

Typical materials for electrical connections 72 include chromium/gold (i.e., a thin chromium underlayer for adhesion;
(top layer for conductivity) or aluminum. Suitable materials for resistor 73 should, as a standard, avoid platinum, titanium-tungsten, tantalum-aluminum, materials that are corroded or dull plated by diffused silicon or amorphous alloy seed inks. . For example, in the case of water-based inks, aluminum and tantalum-aluminum have odor problems at the current and resistivity used as standards (i.e., resistances in the range of 3-5 ohms and currents on the order of IA). to raise. However, these two materials
(Also can be used if a passivation layer is used to insulate the electrical conductor and resistor from the ink.

FIG. 8 is a cross-sectional view of an inkjet printer printhead according to another embodiment of the present invention, illustrating an edge-jitter-inkjet printhead. In this configuration, the thermal energy for generating bubbles within the ink is provided by resistor 83. As in the previous embodiment, resistor 83 is located a short distance (~0.1
m) apart (Note: The cross-section in Figure 8 is taken through resistor 83, so its ink channels
The orifice is not shown (C). In this example, a substrate 81 of glass is provided as standard, which is bonded to an etched silicon capillary block 89. Block 89 is ink channel 8
2. Overlying capillary block 89 and ink channel 82 is typically a high temperature, non-conductive, thermally conductive material such as silicon carbide, silicon dioxide, silicon nitride or boron nitride. Furthermore, the thin film 87 is made of a flexible material. Resistor 83 is mounted on membrane 87 by standard techniques, and power to resistor 83 is provided through metallization 1-85 on each side of the resistor.

The advantage of this configuration over non-flexible structures is that the lifetime of the device can be improved. Also, the structure consisting of the substrate 81, the capillary block 89 and the thin film 87 is essentially completed before forming the resistor and metallization layers, thereby simplifying the construction technique. As in the examples, this structure is easily adapted to multi-channel devices and mass production techniques. Various variations in the technique of forming resistors on flexible thin films are conceivable to those skilled in the art. For example, By appropriate selection of materials, flexible thin films as isolation structures can be completely eliminated by providing a resistor that is itself flexible and self-supporting.

FIG. 9A shows an inkjet printer according to another embodiment of the present invention.
FIG. 9B is an exploded perspective view of the print head of the printer after assembly. The structure shown in both figures is an alternative configuration of a thermal inkjet print head, a so-called 5-ide-shooter device. Constructed of an inert, rigid, thermally insulating material. Electrical connections to resistor 93 are provided by resistors 7A and 7B.
This is provided by two conductors 92 as in the structure shown in the figure.

Two plastic spacers 94 are attached to the lid 95 and the substrate 9.
A capillary channel 96 is used to maintain the separation of
is formed. However, it is clear that many other techniques may be used to provide adequate spacing. For example, instead of plastic, the glass substrate 91 itself may be etched to provide such channels.

The lid 95 in this embodiment is constructed of silicon, which provides a convenient crystalline structure for etching the tag, which acts as an orifice 97 for the inkjet. This orifice 97 is described, for example, in U.S. Pat.
．． 007.464. The orifice 97 is standard and has a temperature of about 0.1 °C. Side Shooter - Fist Ink Jet Lid 9
Many other materials can also be used for 5. For example, a metal layer or even plastic with holes in the part opposite each resistor can be used.

FIG. 10A is a partially sectional perspective view of a print head of an ink-shed printer according to another embodiment of the present invention;
Figure B is a plan view of the substrate of the printhead shown in Figure 10A. This embodiment is a side shooter device with multi-jet, and the substrate 101 is made of glass, on which two glass spacers 104 for holding ink 102 are placed. Silicon lid 105 is provided with a series of etched tapered holes, such as represented by hole 107. Each hole is formed inside the trough 108. Thicker lids can be used; thicker lids allow for larger prints on composite jets.
It can provide better structural stability to support the head. Element 109 is a fill tube connected to a remote ink reservoir (not shown) to allow a continuous supply of ink to the resistor/orifice fist system.

In FIG. 10B, the second resistor 106 is also
It is shown lying along trough 108 in Figure A.

Power to resistors 103 and 106 is provided by two independent electrical connections 110 and 111 and a common ground 112. A barrier 113 is provided between resistors 106 and 103 to prevent ink from being ejected from orifice 107 when resistor 106 is energized.
is formed. In the above configuration, barrier 113 is constructed of glass, silicon, photopolymer, glass-peed-filled epoxy, or electroless plated metal;
Formed on the inner surface of the substrate or lid. If a metal lid is used, other methods are available to provide the barrier. For example, the barrier may be constructed by metal plating directly onto the inner surface of the metal lid.

FIG. 11 shows an inkjet printer according to another embodiment of the present invention.
FIG. 9 is a partially cross-sectional perspective view of the print head of the printer incorporating the thin film and external resistor shown in FIG. 8;

The details of this example are that the substrate is made of silicon carbide, silicon dioxide,
Thin film 120 made of silicon nitride or boron nitride and substrate 1
21, except that it is replaced by
It is the same as the one in Figure 0. The resistor 123 is a thin film 120
It is placed above and outside the ink. As in the previous example, electrical connection to resistor 123 is provided by two conductors 122. Substrate 121 is provided for structural stabilization and typically has an etched glass.

Many other embodiments are possible, constructed of various materials and having different geometries, depending on the particular nature and needs of the application. For example, within the limits of Depending on the ink being used, the orifice size can be increased to increase the droplet size, or the orifice can be decreased to decrease the droplet size. The maximum frequency for droplet ejection depends on the relaxation time of the substrate and the refill time of the ink. The electrical properties of the ink may require different geometries. For example, if a highly conductive ink If current flowing through the ink is a concern, a passivation layer may be placed on top of the resistor itself and on the conductors to avoid current conduction.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of the print head of an inkjet printer according to an embodiment of the present invention, FIG. 2 is an overall perspective view of the print head shown in FIG. 1 after assembly, and FIG. 3 is the same as that shown in FIG. FIG. 4 is a diagram showing the process of ink droplet generation during one cycle of printing operation, FIGS. 5 and 6 are waveform diagrams of electric pulses used to form bubbles, FIG. 7A is an exploded perspective view of a print head of an inkjet printer according to another embodiment of the present invention, FIG. 7B is an assembled perspective view of the print head shown in FIG. 7A, and FIG. 8 is an exploded perspective view of a print head of an inkjet printer according to another embodiment of the present invention. FIG. 9A is a cross-sectional view of a printhead of an inkjet printer according to an embodiment of the invention.
9B is an exploded perspective view of a print head of an inkjet printer according to another embodiment of the present invention, FIG. 9B is an assembled perspective view of the print head shown in FIG. 9A, and FIG. 10A is another embodiment of the present invention. FIG. 10B is a partially cross-sectional perspective view of a print head of an inkjet printer according to an example.
Top view of the print head substrate shown in Figure 0A, No. 11
The figure is a partially sectional perspective view of a printhead of an inkjet printer according to another embodiment of the present invention. 11: Substrate, 13: Thin metallization layer, 14: Non-conductive strip, 15: Capillary block, 16: Resistor, 17:
capillary channel, 19: ink reservoir, 23, 25: electrode, 21: ink, 71: substrate, 72: electrical connection,
731 resistor, 75: capillary block, 77: capillary channel, 81 two substrates, 82: channel, 83: resistor,
85: metallized layer, 87: thin film, 91: substrate, 92: conductor, 93: resistor, 94 varnish spacer, 95: lid, 97:
Orifice, 112: Common ground, 101: Substrate, 1o2
: ink, 1o3: resistor, lO4: suhesa, 108
:)97.12o: thin film, 121=conductor, 123: resistor. Applicant Yokogawa Yokogawa Neerett Buckard Co., Ltd. Agent Patent Attorney Tsuguo HasegawaFIG 5
FIG B Continued from Page 1 0 Inventor Christopher A. Tacklint 250 Calaper Street, Palo Alto, California, United States 0 Inventor Howard H. Tubb 1556 Jose Nissington Place, California, United States

Claims (1)

[Claims] an ink holding means having an orifice for holding ink and ejecting the ink, and an iA of the orifice;
and a heating means for supplying energy to the ink and for vaporizing the ink and ejecting ink droplets from the orifice; 1. An inkjet printer, characterized in that it is formed of a body and a substrate, and the heating means is arranged opposite to the ink via the thin film body.