JP2805775B2 - Printing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The present invention is excellent in gradation (image density),
The present invention relates to a printing device having a simple structure.

[Prior Art] Conventionally, the following methods (1) to (3) have been known as gradation recording methods used in this type of printing apparatus.

(1) Gradation recording method based on change in ink particle density: This method controls the number of ink particles of the same diameter adhering to one pixel area (ink particle density) in accordance with the image density. It is for recording.

(2) Gradation recording method based on change in diameter of ink particles: This method performs gradation recording by controlling the size of ink particles (particle size of ink) according to the image density.

(3) Gradation recording method based on ink flow rate change: This method performs gradation recording by controlling the flow rate of the string-like ink in accordance with the image density.

"Problems to be Solved by the Invention" By the method (1), it is difficult to obtain finer gradation than ink particles because the ink particle diameter is constant.

This disadvantage can be solved by the above-described method (2), which is a gradation recording method based on a change in the diameter of ink particles. However, in practice, it is necessary to finely control the particle diameter of each particle. Is very difficult.

In addition, the methods (1) and (2) are generally applied to a known continuous-type ink jet storage device. In this case, an ink pressurizing mechanism, an ink reproducing mechanism, and the like are required. , The structure becomes complicated.

Further, even in the gradation recording method based on the ink flow rate change of the above (3), since the method uses only the flow of the string-like ink, it is difficult to perform minute control, and there is a limit in obtaining natural gradation. there were.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a printing apparatus which is excellent in gradation and has a simple operation or structure.

"Means for Solving the Problems" The invention according to claim 1 includes a record carrier that carries a recording medium, an ink nozzle, and a counter electrode that is disposed to face the ink nozzle at a predetermined interval. A signal voltage generation circuit for applying a signal voltage corresponding to the gradation data between the ink nozzle and the counter electrode, and the ink nozzle relatively moving in a predetermined direction along a recording medium surface carried on the recording carrier. Main scanning means for running, and sub-scanning means for relatively moving the ink nozzle along the recording medium surface in a direction perpendicular to the predetermined direction, and between the ink nozzle and a counter electrode. In a printing apparatus in which an amount of ink corresponding to an applied signal voltage is attracted from the ink nozzles and adhered to a recording medium to perform gradation recording, the signal voltage generation circuit includes a low-density gradation data. In response to the,
The ink generates a signal voltage at which the ink becomes atomized ink on the recording medium surface, and generates a signal voltage at which the ink becomes a string-like ink on the recording medium surface in accordance with high-density gradation data. The ink nozzle has a cylindrical shape, and is formed by cutting a tip end surface of the ink nozzle at an acute angle.

According to a second aspect of the present invention, in the printing apparatus according to the first aspect, the pair of opposing electrodes are linearly opposed to each other via a gap for allowing the induced ink to pass therethrough. It is characterized by comprising a rod-shaped electrode.

According to a third aspect of the present invention, there is provided a recording medium for carrying a sheet-shaped recording medium, an ink nozzle, a counter electrode disposed at a predetermined distance from the ink nozzle, and a gradation data. A signal voltage generating circuit for applying a signal voltage between the ink nozzle and the counter electrode in accordance with the above, and the ink nozzle is disposed at an arbitrary position on the recording medium along the surface of the recording medium carried by the recording carrier and XY to move
Coordinate moving means, Z-axis moving means for arbitrarily adjusting the distance from the tip surface of the ink nozzle to the surface of the recording medium carried on the record carrier, the signal voltage generating circuit,
The ink generates a signal voltage at which the ink becomes atomized ink on the recording medium surface according to the low-density gradation data, while the ink is pulled on the recording medium surface according to the high-density gradation data. Generating a signal voltage that becomes a thread-like ink, the counter electrode is attached to the surface of the record carrier,
The recording medium also serves as an electrostatic attraction electrode for electrostatically attracting and fixing the recording medium.

"Operation" In accordance with the high density gradation data, the spinning ink adheres to the recording medium, while the atomized ink adheres to the recording medium according to the low density gradation data. The thread-like ink is suitable for high-density recording, but is not suitable for low-density recording. on the other hand,
The atomized ink is suitable for low-density recording, but is not suitable for high-density recording.

Therefore, in this manner, high gradation recording from a low density area to a high density area can be obtained.

Further, if gradation recording is performed in a zigzag manner, a smoother halftone recording can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 is a block diagram showing a configuration of a printing apparatus according to a first embodiment of the present invention.

 First, the mechanical configuration will be described.

In FIG. 1, reference numeral 1 denotes a platen roller around which a printing paper 2 is wound. The platen roller 1 is driven by a pulse motor (not shown), and rotates the print paper 2 in the direction of arrow A with the rotation of the pulse motor. The platen surface of the platen roller 1 is grounded. Reference numeral 3 denotes an ink jet head body for attracting and ejecting the ink 4 by electrostatic attraction. The ink jet head body 3 has a liquid chamber 5 for storing ink 4.
And a conductive ink nozzle 6 extending vertically from the lower surface of the liquid chamber 5. The ink nozzle 6 has an outer diameter of 50
0μm, 300μm inside diameter, 15mm length cylindrical part and shaft
It has a tip surface inclined at 30 degrees. This is because the diameter of the generating portion of the ink liquid column (hereinafter, referred to as a string) which is induced and ejected from the ink nozzle 6 corresponds not to the inner diameter of the ink nozzle 6 but to the radius of curvature of the tip end portion of the front end surface. . A DC bias voltage Vb is applied to the cylindrical portion of the ink nozzle 6 during operation. As the ink 4, a low-conductive and high-dielectric oil-based ink is used.
The ink 4 forms a meniscus on the tip surface of the ink nozzle 6 by static pressure. In front of the ink nozzle 6 (to the right in the figure), at a predetermined interval (for example, 2 mm),
A counter electrode 7 is provided. The counter electrode 7 includes a pair of rod-shaped electrodes having the same shape. These rod electrodes are
They are arranged in a straight line on the left and right, with a gap for passing the thread. When the counter electrode 7 is configured in this manner, clogging of ink can be more effectively prevented as compared with an electrode having a pinhole. The ink jet head is constituted by the ink jet head main body 3 and the counter electrode 7. 8 depends on the number of pulses
This is a linear pulse motor for moving a slider (movable element) 8a along a scale (stator) 8b. The scale 8b is provided along the axis of the platen roller 1. And
The ink jet head is mounted and fixed on the upper surface of the slider 8a. Thus, the ink jet head can travel in the axial direction of the platen roller 1.

 Next, the electrical configuration will be described.

Reference numeral 9 denotes a data input unit for inputting gradation data of an image;
Reference numeral 10 denotes a control circuit for controlling each unit (the signal voltage generation circuit 11, the main scanning driver 12, and the sub-scanning driver 13) of the ink jet printer. The signal voltage generation circuit 11 is a circuit that generates a signal voltage Vs according to gradation data of an image. The main scanning driver 12 is a drive circuit that drives the pulse motor to rotate the platen roller 1 in the circumferential direction. The sub-scan driver 13 is a drive circuit that drives the linear pulse motor 8 to move the ink jet head in the axial direction of the platen roller 1. Reference numeral 14 denotes a converter for converting digital gradation data into analog gradation data.

 Next, the principle of the gradation recording operation of this example will be described.

In this example, the signal voltage applied to the counter electrode 7
Vs changes in the range of 0V to 600V according to the gradation data. On the other hand, the DC bias voltage Vb applied to the ink nozzle 6 is set to 2.2 KV. Therefore, if the signal voltage Vs changes, the potential difference (Vb−Vs) between the ink nozzle 6 and the counter electrode 7 also changes, and eventually, the potential difference (Vb−Vs) between the ink nozzle and the counter electrode also becomes the gradation data. Accordingly, it will change in the range of 1.6 KV to 2.2 KV. Further, a meniscus of the ink 4 is formed on the tip end surface of the ink nozzle 6. Then, an electrostatic attraction according to the potential difference (Vb−Vs) between the ink nozzle and the counter electrode acts on the meniscus. In this example, the signal voltage
When Vs is about 500 V or less, in other words, when the potential difference between the ink nozzle and the opposing electrode (Vb-Vs) is 1.7 KV or more, the electrostatic attractive force acting on the meniscus overcomes the surface tension and the ink nozzle 6 Ink 4 is attracted. As shown in FIG. 2, the attracted ink 4 initially flies as a string Sa. However, the Coulomb repulsion caused by the polarized charges induced in the thread Sa reduces the apparent surface tension,
Eventually, the thread Sa becomes split and atomized. That is, at some point,
The attracted ink 4 changes from the thread Sa to the atomized ink Sb (atomized state). The attracted ink 4 flies for a while after becoming the atomized ink Sb, but when it reaches a certain point, it transitions to the scattering ink Sc (scattering state).

The gradation recording according to the present invention is performed by using the 3
Of the states, the former two states, namely, the spinning line Sa and the atomized ink
Although Sb is used, the gradation recording principle of the present invention will be described in detail below.

That is, it is known from the experiment that the length of the string Sa is determined by the static pressure applied to the meniscus of the ink 4 and the potential difference between the meniscus and the counter electrode (Vb-Vs). Therefore, by controlling the potential difference (Vb-Vs) between the meniscus and the counter electrode, the spinning line Sa or the atomized ink Sb can be adhered to the surface of the printing paper 2, and the spinning line Sa can be adhered. Also, the flying speed of the atomized ink Sb can be controlled. At this time, in a region where the potential difference between the meniscus and the counter electrode (Vb-Vs) is high, a long string Sa is obtained, and thus the string Sa adheres to the paper surface. Further, as the potential difference between the meniscus and the counter electrode (Vb-Vs) increases, the flying speed of the string Sa increases. Thus, in this high-potential-difference region, high-density gradation recording in which the density becomes high in accordance with the rise in the potential difference is obtained. On the other hand, in a region where the potential difference between the meniscus and the counter electrode (Vb-Vs) is low, the atomized ink Sb is obtained, and therefore, the atomized ink adheres to the paper surface. Further, as the potential difference between the meniscus and the counter electrode decreases, the flying speed of the atomized ink Sb decreases. Thus, in this low-potential-difference region, low-density gradation recording in which the density becomes low in accordance with the decrease in the potential difference is obtained.

 Next, the operation of this example will be described.

First, the signal voltage Vs is initially set to 600 V for the counter electrode 7, the DC bias voltage Vb is set to 2.2 KV, and applied to the ink nozzle 6. In this state, the control circuit 10 controls the main scanning driver 12 and the sub-scanning driver 13, and
Scanning of the printing paper 2 in the circumferential direction of the platen roller 1 (hereinafter, referred to as main scanning) and scanning in the axial direction (hereinafter, referred to as sub-scanning) are started. In this case,
The control circuit 10 performs one sub-scan every time one main scan is completed. Here, when the ink jet head reaches a predetermined position on the printing paper (for example, a printing start position),
The control circuit 10 sends the gradation data of the image supplied from the data input unit 9 to the signal voltage generation circuit 11 via the D / A converter 14. When receiving the grayscale data, the signal voltage generation circuit 11 generates a signal voltage Vs according to the grayscale data and applies the signal voltage Vs to the common electrode 7. When the signal voltage Vs is applied to the counter electrode 7, the ink 4 is attracted from the ink nozzle 6 according to the signal voltage Vs. In this way, a single main scan prints a gradation image by one dot line. Next, sub-scanning is performed. By repeating the above process, gradation recording for one screen is completed.

Second Embodiment FIG. 3 is a block diagram showing the configuration of a printing apparatus according to a second embodiment of the present invention.

In this figure, parts corresponding to the respective parts in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. The ink jet printer of this example is greatly different from the printer shown in FIG. 1 in that a zigzag deflection electrode 15 and a zigzag voltage generating circuit 16 are provided. The zigzag deflection electrode 15 is
The ink nozzles 6 are arranged in front of the ink nozzles 6 (to the right in the drawing) at predetermined intervals. Zigzag deflection electrode 15
A pair of rod-shaped deflection electrodes 15a, 15b, which are linearly opposed to each other, with a gap for passing Sa or atomized ink Sb
Consists of On the other hand, a counter electrode 7 is provided orthogonal to the axis of the zigzag deflection electrode 15. The center point of the gap of the counter electrode 7 is arranged so as to coincide with the center point of the gap of the zigzag deflection electrode 15. The zigzag voltage generation circuit 16 responds to a zigzag command from the control circuit 10,
The zigzag signal voltage Vf of one pulse is output. Switch 17
Has a function of alternately applying a zigzag signal voltage Vf of 15 pulses to the rod-shaped electrodes 15a and 15b.

 Next, the operation of this example will be described.

The operation of this example is different from that of the first embodiment in that
The point is that at the same time as the gradation data of one pixel is output from the control circuit 10 to the signal voltage generation circuit 11, a zigzag command signal is sent from the control circuit 10 to the zigzag voltage generation circuit 16. Thus, the timing at which the signal voltage Vs for one pixel is applied to the counter electrode 7 and the one-pulse zigzag signal voltage Vf is applied to one of the left and right deflection electrodes 15a and 15b constituting the zigzag deflection electrode 15. The application timing coincides. At this time, when a one-pulse zigzag signal voltage Vf is applied to the left deflection electrode 15b, the ink 4 attracted according to the signal voltage Vs, as shown in FIG. Is deflected to the side (downward in the figure). This is O
The left deflection electrode 15b in the N state and the right deflection electrode 1 in the OFF state
This is because a downward electric field generated between the light emitting element and 5a acts.
This deflection state is reversed at the timing when the next gradation data is input to the signal voltage generation circuit 11. That is,
At this time, a signal voltage Vs according to the gradation data is applied to the counter electrode 7. On the other hand, in synchronization with this, the left deflection electrode 15b changes from the ON state to the OFF state, and the right deflection electrode 15b changes.
a changes from the OFF state to the ON state. That is, the zigzag signal voltage Vf of one pulse is applied to the right deflection electrode 15a this time. At this timing, the ink 4 induced according to the newly applied signal voltage Vs
As shown in (2), the light is deflected to the side (upward in the figure) of the left deflection electrode 15b in the OFF state. This, contrary to the above,
This time, an upward electric field acts. By repeating the above-described operation, it is possible to perform gradation recording with zigzag processing (hereinafter referred to as zigzag gradation recording). Using this zigzag gradation recording, dot lines are formed by recording based on gradation data, and new dot line recording based on interpolation data is also performed between the dot lines thus formed. Can be. In this case, when one deflection electrode (for example, left deflection electrode 15b) is ON and the other deflection electrode (for example, right deflection electrode 15a) is OFF, interpolation data is sent to the signal voltage generation circuit 11. The signal voltage Vs is output and applied to the counter electrode 7. Here, there are various methods for obtaining the interpolation data. For example, as shown below, the average density of four adjacent pixels can be calculated, and this average density can be used as the interpolation data. FIG. 5 shows original image information composed of N × N pixels. In this figure, symbols A, B, C, and D represent respective density data of four adjacent pixels. From these density data A, B, C, and D, an average density, that is, interpolation data X1, is calculated using the following equation: X1 = (A + B + C + D) / 4. As shown in FIG. 6, this interpolation data X1 is used as density data for interpolating the center point of four adjacent pixels for recording the interpolated gradation between dot lines.

As described above, according to the printing apparatus of the first embodiment, since the flying ink 4 is deflected in a zigzag manner and the interpolation data is used, a smoother halftone recording can be obtained, and the image quality can be further improved. The ink nozzle 6 can be improved in the sub-scanning direction.
Apparent scanning can be performed with a movement amount that is half of the movement amount of.

Third Embodiment FIG. 7 is a perspective view showing a configuration of a printing apparatus according to a third embodiment of the present invention, and FIG. 8 is a sectional side view showing the same.

In these figures, reference numeral 18 denotes a recording table on which recording paper 19 is placed on a plane. The recording table 18 includes an insulating plate 20 and electrostatic suction electrodes 21a and 21b laminated on both surfaces of the insulating plate 20. Electrodes 21a and 21b for electrostatic attraction
The recording paper 19 placed on the recording paper 19 is brought into close contact with the recording paper 19 by applying an electrostatic attraction force. Reference numeral 22 denotes a linear pulse motor for moving the X-axis, which is disposed along the X-axis of the recording table 18. This linear pulse motor 22 has the same configuration as that shown in FIG. A pulley 24 is mounted and fixed on the upper surface of a slider 22b of the linear pulse motor 22 via a Y-axis moving pulse motor 23 and a support (not shown). The pulse motor 23 and the pulley 24 are arranged opposite to each other on a straight line parallel to the Y axis via the surface on which the recording paper 19 is placed, and a belt 25 is hung on both. A linear pulse motor 26 for Z-axis movement is locked to the belt 25 so that the belt 25 can move as the belt 25 moves. The linear pulse motor 26 has a short scale unlike the linear pulse motor 22 described above. The linear pulse motor 26 is provided so that the slider can be moved in a direction perpendicular to the paper surface of the recording paper 19 (Z-axis direction). An ink jet head 27 is mounted and fixed on the slider. Ink jet head
The 27 ink nozzles 28 are arranged to face the recording paper 19. A signal voltage Vs according to the gradation data of the image is applied to the ink nozzle 28. This point is different from the first and second embodiments. In this example, the attractive force acting on the ink 29 is given by the potential difference (Vd-Vs) between the electrostatic attraction electrode 21a and the ink nozzle 28.

In such a configuration, after the recording paper 19 is placed on the recording table 18, a predetermined voltage Vd is applied between the electrostatic attraction electrodes 21a and 21b, and the recording paper 19 is suction-fixed. Next, after driving the linear pulse motor 26 to adjust the distance between the paper surface and the ink nozzle 28, the linear pulse motor 22 and the pulse motor 23 are driven to move the ink nozzle 28 to a predetermined recording position. When the ink nozzle 28 reaches a predetermined recording position, a signal voltage Vs corresponding to the gradation data corresponding to the recording position is applied to the ink nozzle 28. By the signal voltage Vs, more precisely, the electrostatic suction electrode 21a and the ink nozzle 28
The density of the ink to be printed is determined by the potential difference between the electrodes (Vd-Vs). By repeating the above, a two-dimensional gradation recording image can be created.

[Effects of the Invention] As is clear from the above description, the present invention utilizes a thread in a high-density recording area and uses atomized ink in a low-density recording area. Near gradation recording can be obtained. In particular, in a low-density recording area using atomized ink, much better gradation can be obtained. Further, the structure of the device is simple.

Further, according to the first aspect of the present invention, since the tip surface of the ink nozzle has an acute angle, it is possible to smoothly fly the ink.

According to the third aspect of the present invention, since the electrode for sucking and fixing the recording paper also serves as the electrode for electrostatically sucking the ink, the apparatus can be simplified and
Since it has the Z-axis moving means, it can be applied to recording media having different thicknesses.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a printing apparatus according to a first embodiment of the present invention, FIG. 2 is a diagram showing a state transition of flying ink, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of a certain printing apparatus, FIG. 4 is a view for explaining the deflection of flying ink in the second embodiment, and FIG.
FIG. 9 is a diagram showing original image information including N × N pixels, and FIG.
FIG. 7 is an explanatory view for explaining zigzag gradation recording using interpolation data, FIG. 7 is a perspective view showing the configuration of a printing apparatus according to a third embodiment of the present invention, and FIG. It is a side sectional view. DESCRIPTION OF SYMBOLS 1 ... Platen roller (recording carrier), 2 ... Printing paper (recording medium), 3 ... Ink jet main body, 4 ... Ink, 6 ... Ink nozzle, 7 ... Counter electrode, 8 ... Linear pulse motor (Sub-scanning means), 10 ... control circuit, 11 ...
... Signal voltage generation circuit, 12 ... Main scanning driver, 13 ... Sub-scanning driver, Sa ... String, Sb ... Atomized ink, 15 ...
Deflection electrode for zigzag, 15a ... Right deflection electrode, 15b ...
Left deflection electrode, 16 ... Zigzag voltage generation circuit, A, B, C, D
... Density data of four adjacent pixels (tone data near four),
X1, X2, X3, X4 ... interpolation data, 19 ... recording paper, 21a, 21b
…… electrode for electrostatic attraction, 22 …… linear pulse motor (XY coordinate moving means), 23 …… pulse motor (XY coordinate moving means), 26 …… linear pulse motor (Z-axis moving means), 27
… Ink jet head.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-99952 (JP, A) JP-A-63-233844 (JP, A) JP-A-49-100165 (JP, A) JP-A-47-197 31531 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B41J 2/205 B41J 2/095 B41J 2/105

Claims (3)

(57) [Claims] A recording medium for carrying a recording medium, an ink nozzle, a counter electrode disposed at a predetermined distance from the ink nozzle, and a signal voltage corresponding to gradation data to the ink nozzle. And a signal voltage generation circuit applied between the counter electrodes, main scanning means for relatively moving the ink nozzle in a predetermined direction along a recording medium surface carried on the record carrier, and Sub-scanning means for relatively running in a direction perpendicular to the predetermined direction along the recording medium surface, and an amount of ink corresponding to a signal voltage applied between the ink nozzle and the counter electrode is provided. In a printing apparatus which performs gradation recording by attracting from the ink nozzles and attaching the recording medium to a recording medium, the signal voltage generation circuit is configured to perform the recording on the recording medium surface in accordance with low-density gradation data. While the ink generates a signal voltage that becomes the atomized ink, the ink generates a signal voltage that causes the ink to become a string-like ink on the recording medium surface in accordance with the high-density gradation data. A printing device having a cylindrical shape and having a front end surface cut at an acute angle. 2. The printing method according to claim 1, wherein said counter electrode comprises a pair of rod-like electrodes which face each other in a straight line via a gap for allowing the induced ink to pass therethrough. apparatus. 3. A record carrier for carrying a sheet-like recording medium, an ink nozzle, a counter electrode arranged at a predetermined distance from the ink nozzle, and a signal voltage corresponding to gradation data. A signal voltage generating circuit to be applied between the ink nozzle and the counter electrode; and XY coordinate moving means for moving the ink nozzle to an arbitrary position on the recording medium along a surface of the recording medium carried on the recording medium. And Z-axis moving means for arbitrarily adjusting the distance from the tip surface of the ink nozzle to the surface of the recording medium carried on the record carrier, wherein the signal voltage generation circuit responds to low-density gradation data. And generating a signal voltage at which the ink becomes atomized ink on the recording medium surface, while the ink is a string-like ink on the recording medium surface in accordance with high-density gradation data. The composed signal voltage generated, the counter electrode, the recording is attached to the carrier surface, and the printing apparatus, characterized in that said recording medium also serves as an electrostatic attraction electrode for fixing by suction electrostatically.