JPH0440186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conventional fluid jet printing apparatus;
In particular, the present invention relates to an elongated continuous fluid jet printing device capable of printing with virtually unlimited printing width.

Various fluid jet printing devices are known in the prior art. For example, some of these are currently commercially available.

Primarily, conventional fluid jet printing devices form a linear array of fluid jet holes through which a pressurized core of colorless fluid (ink, dye, etc.) is ejected. Also downstream of each small hole, individually controllable electrostatic charge electrodes are arranged in the so-called droplet formation region. In accordance with the well-known principles of electrostatic induction, the fluid cores carry electrical potentials of different polarities and are related to the strength of the potential at each charged electrode. When such a fluid core forms a droplet, the droplet is charged with an induced electrostatic charge.

Typically, two charging potentials are selectively used: zero or a predetermined voltage. Thus, by suitably selecting the charging potential on each electrode, the droplet ejected from each aperture can be selectively charged or uncharged.

Further downstream of each charging electrode, the droplet is excited primarily by a fairly strong transverse electric field (deflection electrode). The deflection electrode deflects the charged droplets to a fluid catcher that circulates the droplets not used for printing to a source of pressurized fluid that supplies the fluid jet apertures. The uncharged droplets continue (fly) onto the substrate (paper, textile, etc.) that is primarily printed or selectively processed. This substrate may be stationary, but it is primarily moving in a direction transverse to the flight direction of the droplet. Known techniques align a moving substrate with selected charges of individual droplets ejected from selected apertures of the above-described array of fluid jet apertures to create a desired pattern on the surface of the substrate, e.g. It is used to create geometric patterns, alphabetical patterns, etc.).

The prior art issued in the following US patents is not significant for an exhaustive list of prior art related to the present invention: US Pat. However, these lists are typically representative of fluid jet printing devices.

US Patent No. 3373437 Sweet et al. (1968) 〃 3596275 Sweet et al. (1971) 〃 3298030 Lewis et al. 〃 3701998 No. Matisse (1972) No. 3787883 Cassil (1974) Typically, the prior art uses individual, separate controlled charging electrodes for each fluid jet hole. Also, when multiple fluid jet hole arrays are used in a direction (usually linear) across the device, an equal number of carefully aligned and aligned fluid jet hole arrays and charged electrode arrays are used. used.

For example, in the prior art cited above, an exception to this arrangement is the Robertson embodiment of No. 5 US Pat. No. 3,656,171. Here, a circumferential array of six small fluid jet holes are placed within a single cylindrical electrode that serves as both a charging electrode and a deflection electrode.
However, when such arrays are applied to linear printing transverse machine arrays, maintaining precise alignment between the fluid jet holes and electrodes is a fairly limiting requirement. That is clear.

Typically, when prior art fluid jet printing devices printed lines on a substrate that was aligned directly across the machine and moved through the machine (perpendicular to the transverse direction), a fairly serious problem occurred. The precision requirements result in precisely aligned assembly and manufacture of the fluid jet apertures and the array of individual charging electrodes.

For example, in the second prior art, an array of approximately 0.002 inch (0.0508 mm) diameter fluid jet holes spaced 0.01667 inch (0.42 mm) apart is
Creates droplets approximately 0.004 inch (0.10 mm) in diameter. These pores are surrounded by conductive charged tunnels or electrodes having an inner diameter of 0.013 inches (0.33 mm). The individual charge tunnels must therefore be electrically insulated and cannot therefore be made with significantly larger diameters. If each fluid jet hole were assumed to be precisely aligned within each charging electrode, the distance between the droplet and the inside wall of the charging tunnel would be 0.0045 inches (0.1143
A radial spacing of only mm) is required.

The fluid jet hole array is typically fabricated separately from the charged electrode array (such as an array of conductively coated holes in an insulating substrate) and placed in a plate. It is a pore array. Even if we assume that the droplet could pass directly near the charged tunnel surface without any problems, the fluid jet hole array and the separately manufactured charged electrode array will not be able to handle each other after assembly. Even in position
It is noteworthy that it must be assembled and manufactured within an error of 0.1143 mm. For typical prior equipment with print widths of approximately 10 inches (25.4 cm), mechanical assembly manufacturing tolerances often ranged from approximately
It is noted that it must be kept below 4.5 parts. If the cross-machine direction is sufficiently increased (as required for typical textile printing applications), the required machine tolerances become tighter with each side-by-side alignment.

It has now been discovered that the traditional strict requirements for element-to-element mechanical alignment of stoma arrays with charged electrode arrays can be completely eliminated. By effectively removing these two types of arrays from element-to-element alignment requirements,
Allowable manufacturing and assembly tolerances increase. In some circumstances, increased mechanical tolerances are necessary, although not absolutely necessary, to make practical implementations of the significantly wider machine dimensions required for example in textile printing and other applications.

For example, in the case of textile pattern generators, it is necessary to maintain resolution at the rate of 100 dots per inch (2.54 cm) over a width range of 2 meters or more. Printing on textile sheets also requires a generous resolution of 70 dots per inch. Furthermore, when it comes to printing high-resolution text etc. on paper, the print width is much smaller (e.g. 8.5 inches) in order to match the quality standards that exist.
A resolution of 300 dots per inch is typically required. In all these applications,
The conventional requirement for accurate element (hole)-to-element (charged electrode) alignment of a large number of separately manufactured assemblies of small hole arrays and charged electrode arrays is as follows:
We offer one of the most difficult and exacting manufacturing requirements.

It is believed that the present invention significantly increases the mechanical tolerance for manufacturing or assembly errors in fluid jet printing devices using fluid jet aperture arrays and individually charged electrode arrays. In summary, the number of fluidic orifices increases substantially with respect to the number of individual charged electrodes, and in the impractical but unlimited case an infinite number of fluidic orifices would result in a virtual fluidic sheet. used for. The cross-sections of this virtual sheet are then selectively charged and deflected to produce the desired printed pattern.

The fairly dense linear pore arrays used in the present invention do not require precise element (pore)-element (charged electrode) alignment along the length of these two assembled arrays; Incorporated into a low density array of individually charged electrodes. This increased printing resolution after assembly is fundamentally possible with the low density charged electrode array while simultaneously freeing the system from the need for precise element-to-element alignment. Although some degree of printing error will occur as long as the printing holes are coincidentally located between the individual charged electrodes, such errors can be minimized and, at any given time, are trivial in many applications. . This resulting average printed pixel is simultaneously lowered by the plurality of fluid pores charged and associated with each electrode. The width of each electrode thus corresponds to the printed line in the machine direction produced by the invention and is approximately equal to the pixel width of the dot assembly in the cross machine direction.

In the technique, individual fluid cores and collections of droplets charged by individually associated electrodes can be printed in single dots, thus printing a line of dots in the machine direction one dot wide. .

Stated another way, the present invention provides an elongated fluid jet printing device having an average pixel width capacity of about L/N and improved print resolution position formed as follows.

(a) A first elongated fluid jet orifice array for individual passage of fluid jet wicks having M fluid jet orifices per L unit length.

(b) the second elongate array of individual charged electrodes is connected to the first
can electrically charge the droplet as it forms from the fluid core.

(c) This second charged electrode array has N number of charged electrodes per L unit length.

(d) The fluid jet hole M is considerably larger than the charging electrode N.

In the context of the present invention, a pixel means a unit of printed ink controlled by each electrode. This pixel contains one or more dots, and how many jet streams are controlled by each electrode, and how many machine direction dots are controlled by each jet stream each time the electrodes are not charged. It depends on how it is printed. Machine direction printed lines are the result of printing by groups of pixels controlled by the same electrode as the substrate passes through the print head.

In some embodiments, there are at least twice as many fluid jet holes for each charging electrode. While in some embodiments a charged electrode array may be formed on only one side of a fluid droplet, other embodiments of the invention include a pair of charged electrode arrays disposed on opposite sides of the droplet. . Still other embodiments provide that the pore arrays and the charged electrode arrays are separated from each other so long as each of the pair of parallel fluid jet pore arrays is independently controlled by each charged electrode array. This creates improved resolution for the entire printing device.

It will be appreciated that these and other objects and advantages will become apparent from the following description of presently preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

In FIG. 1, a pressurized fluid source 100 is
It primarily forms an ink, dye, or other fluid that selectively places a pattern (eg, a geometric pattern, text, etc.) on the underlying and moving substrate 102.
Mainly, the substrate 102 (as indicated by arrow 104)
It is moved in a direction through the machine by a conventional transport mechanism, shown schematically as drive rollers 106.

This source of pressurized fluid 100 is supplied to a stoma array 108 that extends along all cross-machine directions (perpendicular to the plane of the page of FIG. 1). Each small hole 11
0 ejects a core 112 of fluid that becomes individual droplets 114 in the droplet formation region. This droplet formation can be predicted in any system by known physical considerations. Downstream of the pores 110 near this droplet formation region are individual pores that selectively apply a charging voltage to the pore array (which is typically electrically grounded as shown at 120). A charging electrode array 116 is formed in which the charging electrodes are arranged in a cross-machine direction. Through electrostatic induction development, separated droplets 114 are selectively charged as they are formed.

These droplets 114 are generated by a fairly strong (electrostatic) force that directs the charged droplets in the cross direction of the droplet movement from a deflection electrode 122 which deflects the charged droplets to a getter or collection device 124, as shown in FIG.
The electric field continues downstream. The array thus allows charged droplets 114 to be electrically deflected and collected in a collector 124 from where they are circulated via pump 126 to pressurized fluid source 100. Uncharged droplet 1
14 is a movable substrate 10 that continues downstream and is in a predetermined position.
2 as a result.

A conventional printing process control circuit 128 is connected to the substrate 102.
In accordance with a conventional pattern input mechanism 130 (charged electrode array 116
is used to align the movement of the substrate (via transport rollers 106) while selectively charging the droplets (via transport rollers 106).

All elements and systems shown in FIG.
6 are conventional and will not be described in more detail here. However, those skilled in the art will recognize that variations in the general fluid jet printing mechanism of the general type shown in FIG. 1 are possible and may be used in the practice of the present invention.

A typical conventional structure of a stoma array 108 and an element-by-element aligned charging electrode array 116 is shown in FIGS. This second
The conventional arrangement of the figure, as previously mentioned, has an assembly tolerance between the stoma array 108 and the charging electrode array 116 of greater than about 4.5 parts per 10,000 over a mechanical cross width of only about 25.4 cm. Must be retained.

Also, in most conventional arrangements, only a single electrode was formed facing each fluid hole, as shown in FIG. Although these prior systems provided high resolution, strict assembly tolerances between the stoma array and the individual charged electrode arrays were required.

Now, in the embodiment of the present invention shown in FIGS. 1 and 4, the element-to-element alignment between the fluid jet holes 110a-110g and the charging electrodes 16a, 16b in the orifice plate or hole array is Although not required, it is possible to achieve approximately the same or somewhat higher resolution printing than before. This loose and acceptable mechanical intersection is
This is accomplished by forming a significantly greater number of fluid jet holes 110 than the number of individual charging electrodes 16a, 16b, etc. Thus, precise element-to-element alignment between the pore array and charging electrode array is not required, but it is ensured that each charging electrode controls one or more fluid jet pores.

In order to maintain the same average fluid flow rate over the substrate, a significantly smaller diameter aperture 110 is used in the present invention when compared to that of the prior art. In short, the total integrated stoma area on the stoma array remains approximately constant in most instances.
Thus, as shown in FIG. 4, if the same fluid flow were maintained as in the prior art embodiment of FIG. must be reduced by the factor .

For the embodiment of the invention shown in FIGS. 5-8, only a portion of the printing head is shown. The structure thus extends outwardly in both directions and is continuous to the desired machine cross length. These alternating embodiments assume a certain alignment tolerance requirement between two charged electrode arrays, but such requirements are not applicable between dissimilar structures such as a charged electrode array and an aperture plate. It is believed that less practical implementation is required than the alignment requirements of the prior art. In the present invention, each charging electrode has charging electrodes facing each other as shown in FIGS. 5 to 7, or has charging electrodes facing each other in a shifted manner as shown in FIG.
Acting on or influencing one or more of the flow of individual droplets and the fluid core as they travel from the orifice plate.

For example, as shown in FIG.
4 are associated with or act upon at least two fluid cores 28. Also in FIG. 6, electrodes 30 and 32 influence or act on three fluid cores 34, 36 and 38, while in FIG. 7 each electrode affects four fluid cores 44-50.
Further, in FIG. 8, each electrode affects a plurality of jet fluid cores, but in this example the electrodes are staggered and placed on opposite sides so as not to be paired in opposition. Therefore, the two rows of jets are arranged differently offset. This arrangement produces about twice the resolution as compared to a single row array of small holes and a single or double-sided arrangement of charged electrode arrays. A common deflection electrode is typically placed downstream between the two rows of stoma arrays.

Because of these various arrangements, the density of the jet holes and fluid core flow of the present invention results in significantly higher resolution, approximately 150 to 400 jets per inch, compared to the 100 dots per inch of standard inking devices. have.

In order to maintain the fluid dependence of conventional systems, each of the hole diameters of the present invention increases in number and two groups, since the number of holes per inch is increased relative to the corresponding prior art system. It must be reduced according to the formula derived from the recovery area of the hole. Assuming it is a round hole, M with diameter D
The total area of the number hole is M×π(1/2D) ² ,
This is equal to the total area of M' number of holes in the conventional system with diameter D', ie, M'×π(1/2D') ² .
Therefore, the diameter D is D=D'×√'.

The size of the holes of the present invention is therefore proportional to the square root of the ratio of the two numbers or densities of holes. For example, if the hole density in a conventional device is 100/inch (i.e., a resolution of 100 dots/inch),
The corresponding system implemented by the present invention is
For a hole density of 200/inch (with two rows of charged elements of 100/inch each), the hole size of the conventional system is typically 0.002 inch, while the hole diameter of the present invention is is 0.002×√100×
200 or approximately 0.001414 inches. The flow from each jet hole in the present invention is halved, but since the number of holes is doubled, the flow through a unit length of orifice plate is the same in the two systems.

In one presently preferred embodiment of the invention, the charged electrode plates are spaced about 0.007 inches center-to-center, or about 143 charged electrodes per inch. The associated small holes are about 0.0035 inches center-to-center or about 283/
inch density, each with a diameter of approximately
It is 0.0013 inches. The droplet is therefore about twice the diameter of the ostium or 0.0026 inches.

In embodiments of the invention, the orifice plate and printing head rods may be 1.8 to 3 meters or more.

In FIG. 5, charging electrodes 22 and 24 are
They are arranged face-to-face and affect at least two jet streams 26 and 28.

In FIG. 6, charging electrodes 30 and 32 are
They are arranged face-to-face and affect at least three jet streams 34, 36 and 38.

In FIG. 7, charging electrodes 40 and 42 are
They are arranged directly facing each other and affect at least four jet streams 44, 46, 48 and 50.

In FIG. 8, charging electrodes 60, 62 and 6
4 are located in two rows on one side of the jet stoma arrays 66,68, while charging electrodes 70, 72, 74 and 76 are located on the opposite side of the stoma arrays 66,68 in two rows. This electrode 60 is connected to electrodes 70 and 72.
Also, electrode 70 compensates for the gap between electrodes 60 and 62. This staggered arrangement of electrodes between opposite sides of the two rows of stoma arrays 66 and 68 continues along the entire length, with no electrodes being placed face-to-face. This jet staggering allows double resolution to be printed compared to a single row of aperture arrays.

By controlling the alignment of the electrodes in each array, it is possible to leave a print or gap along the cross-machine direction in increments primarily equal to the length of the individual electrodes. Also, whenever the print is affected by a two-row array of holes, the cross-machine resolution is double, but the minimum possible print increase is a single electrode width.

As mentioned above, current applications of the invention include 1
Preferably, there are about 100 or more electrodes per inch. However, each electrode charges two or more jets in its vicinity. It is noted that there is therefore no required alignment between the jet aperture and the charging electrode, and that charging electrodes of various configurations may be used, as shown in FIGS. 4-8. Two or more jets are thus controlled by one electrode. That is, the ratio between the number M of jets per unit length and the number N of charged electrodes does not have to be an integer.

With the present invention, it is no longer required to maintain close assembly tolerances between the charging electrode and the orifice plate element. Tolerances are therefore not limited to the mechanical width of the inkjet system, and the absence of this allows for lower costs even in fairly short width devices. Further, since conventional manufacturing methods for forming fine holes in close proximity are available in the semiconductor or printed circuit board manufacturing industry, there is no problem in forming each small hole with a suitable profile in the orifice plate. Similarly, the charge plate can be manufactured to suitable tolerances by conventional techniques (printed circuit board manufacturing by photo-etching techniques).

If the jet is placed correctly between the charged and uncharged electrodes, the droplet will be partially charged and therefore partially deflected into the getter or circulation mechanism. In this case, the droplet slightly adheres to the substrate. However, the droplet getter structure can collect droplets even at fairly low angles of deflection, resulting in slightly erroneous droplets being deposited on the substrate.

Although the invention has been described with regard to the presently most practical and preferred embodiments, it is not limited to these embodiments, but on the contrary includes all modifications and equivalent arrangements.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a fluid jet printing device embodying the present invention, FIG. 2 is a diagram of the arrangement of small holes and electrodes in a conventional fluid jet printing device, and FIG. 3 is a diagram of another conventional fluid jet printing device. Arrangement diagram of small holes and electrodes,
FIG. 4 is a detailed view of one embodiment of the small hole array and charging electrode array used in the fluid jet printing device shown in FIG. 1, and FIGS. FIG. 4 is a detailed view of another embodiment of a pore array and a charged electrode array; 16a, 16b... Charged electrode, 108... Small hole array, 110... Small hole (orifice), 112... Fluid core, 116... Charged electrode array.

Claims (1)

[Scope of Claims] 1. A first array in which M small holes for each unit length L are arranged through which a wick-shaped fluid jet stream passes individually; and at least one downstream side of the first array. N charging electrodes are arranged for each unit length L, and each charging electrode has a charging electrode that charges the droplets when the fluid jet flow becomes a droplet. a second array of 100 or more arrays per inch; and means for deflecting the droplets charged by the charging electrode; and between the first and second arrays, the small holes and A fluid jet printing device, wherein the fluid jet printing device is not aligned with the charging electrode, the M is at least twice the N, and the average pixel width is L/N. 2. A fluid jet printing apparatus according to claim 1, wherein the first array is parallel to the second array. 3. A fluid jet printing apparatus according to claim 2, wherein the second array is located on both sides downstream of the first array. 4. A fluid jet printing apparatus according to claim 3, further comprising means for supplying printing liquid to said small holes to generate a plurality of parallel fluid jet flows. 5. Any one of claims 1 to 4, characterized by having means for selecting a corresponding electrode for charging a droplet passing through the electrode by means of a predetermined electrical signal. A fluid jet printing device as described in . 6. A fluid jet printing apparatus according to any one of claims 1 to 5, further comprising means for collecting droplets deflected by said deflecting means. 7. Claims 1 to 6, characterized in that the width of each of the charging electrodes is a width spanning at least two wick-shaped fluid jet streams injected from the plurality of small holes. The fluid jet printing device according to any one of the above. 8. The invention as claimed in claims 1 to 7, characterized in that it comprises means for applying a voltage to a plurality of individually selected charging electrodes for charging a corresponding predetermined droplet. A fluid jet printing device according to any one of the above.