JP3480774B2 - Ink jet recording device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording apparatus, and in particular, a liquid ink in which a colorant is dispersed in a solvent is used, and at least the colorant component in the ink is ejected as an ink droplet onto a recording medium. The present invention relates to an inkjet recording device for recording.

[0002]

2. Description of the Related Art An apparatus for recording an image by forming recording dots by ejecting liquid ink as small droplets called ink droplets on a recording medium has been put into practical use as an inkjet printer. Inkjet printers produce less noise than printers of other recording methods,
It has the advantage that processing such as development and fixing is unnecessary,
It is drawing attention as a plain paper recording technology. Although many inkjet printer systems have been devised up to the present, in particular, (a) a system in which ink droplets are ejected by the pressure of vapor generated by the heat of a heating element (for example, Japanese Patent Publication No. 56-94).
29, Japanese Examined Patent Publication No. 61-59911), and (b) a method in which an ink droplet is ejected by a mechanical pressure pulse generated by a piezoelectric element.

A recording head used in an ink jet printer (referred to as an ink jet head) is mounted on a carriage for recording while moving in a direction (main scanning direction) orthogonal to a conveying direction (sub scanning direction) of a recording sheet. A serial scanning type head is used in practice. It is difficult to increase the recording speed of this serial scanning head. Therefore, the recording speed can be increased by using the recording head as a long head having the same size as the width of the recording paper.
So-called line scanning heads have been considered, but it is not easy to realize such line scanning heads for the following reasons.

In the ink jet recording system, the concentration and concentration of the ink are likely to occur locally due to the evaporation and volatilization of the solvent, which causes the clogging of individual thin nozzles corresponding to the resolution. Further, in the method of using the pressure of vapor for forming an inkjet, insoluble matter is attached due to a thermal or chemical reaction with the ink, and in the method of using the pressure of a piezoelectric element, complicated ink flow paths and the like are complicated. The structure makes it easier to induce clogging. Line scanning heads that require thousands of nozzles, which are even more numerous than serial scanning heads that use several tens to hundreds of nozzles, are probabilistically clogged at a fairly high frequency and are reliable. It becomes a big problem in terms of sex.

Further, there is a problem that the conventional ink jet recording apparatus is not suitable for improving the resolution. That is, with the method using the pressure of vapor, it is difficult to generate ink particles having a diameter of 20 μm or less (this corresponds to a recording dot having a diameter of about 50 and several μm on the recording paper), and the pressure generated by the piezoelectric element is generated. This is because in the method of using, the recording head has a complicated structure, and it is difficult to form a head with high resolution due to problems in processing technology.

In order to overcome these drawbacks, an ink jet recording system is devised in which a voltage is applied to a thin film electrode array and ink or a coloring material component therein is ejected as ink droplets from the ink liquid surface by using electrostatic force. Was done. Specifically, a method of ejecting ink droplets by using electrostatic attraction to the ink (JP-A-49-62024, JP-A-56-446).
No. 7, etc.) or a method in which an ink containing an electrically charged coloring material component is used to increase the density of the coloring material and eject ink droplets (WO93 /
11866: PCT / AU92 / 00665) and the like have been proposed. These methods use line scanning because the recording head configuration is a slit-shaped nozzle configuration that does not require a nozzle for each individual dot, or a nozzleless configuration that does not require a partition of an ink flow path for each individual dot. This is effective in preventing and recovering from clogging, which was a major obstacle in realizing a mold recording head. The latter is particularly suitable for high resolution because it can stably generate and fly ink particles having a very small diameter.

[0007]

In the ink jet recording apparatus of the type that ejects ink droplets by the electrostatic force described above,
By applying a pulse voltage according to an image signal to the electrode array, ink droplets fly. Here, consider a case where a pulse voltage is applied only to every other electrode of the electrode array to cause ink droplets to fly from those electrodes. This corresponds to recording vertical stripes, that is, stripes along the sub-scanning direction. In such a case, an electric field is formed from the electrode to which the pulse voltage is applied to the adjacent electrode to which the pulse voltage is not applied. By the electric field between the adjacent electrodes,
Since the charged coloring material component moves from the electrode to which the pulse voltage is applied to the electrode to which the pulse voltage is not applied, if this state continues, the density of the coloring material in the ink on each electrode becomes non-uniform and the recorded image Cause uneven density.

Further, if such a state continues for a long time, the coloring material component is deposited on the electrode to which the pulse voltage is not applied and the viscosity becomes high. Charged charges move between them, and the charges of the colorant components disappear. In such a case, the colorant component on the electrode to which the pulse voltage is not applied can no longer be moved by electric force and is fixed on the electrode. In this way, the colorant component fixed on the electrode causes a change in the shape of the electric field distribution, hinders the movement of other colorant components, and interrupts the continuous supply of ink.

According to the present invention, in an ink jet recording apparatus for recording by causing the coloring material components in the ink to agglomerate and fly by electrostatic force, the coloring material concentration on each electrode on the head substrate is made uniform and the coloring material is applied to the electrodes. An object of the present invention is to provide an ink jet recording apparatus that can prevent colorant components from sticking and perform stable recording.

[0010]

In order to solve the above problems, the present invention supplies an ink in which a colorant is dispersed in a solvent onto a head substrate, and applies an electrostatic force to the colorant component in the ink. In an inkjet recording apparatus that performs recording by ejecting ink droplets containing at least a colorant component toward a recording medium, the ink supplied on the head substrate with respect to a plurality of electrodes provided on the head substrate. It is characterized in that it is provided with a voltage applying means for applying a voltage for stirring the colorant component therein. More specifically, for example, at least first and second electrodes are provided on the head substrate,
The voltage applying means applies to these first and second electrodes,
A voltage is applied between the electrodes so that a potential difference in which the relationship of potential level is reversed in a predetermined cycle is generated.

Further, the voltage applying means includes the first and second voltage applying means.
A voltage that causes a potential difference between the two electrodes that causes the height relationship of the potentials to be reversed in a predetermined cycle as described above when the ink droplets are not flying is applied to the first electrode when the ink droplets are flying. The voltage is applied so that a different second potential difference is generated between both electrodes.

As described above, by applying a voltage to the first and second electrodes adjacent to each other on the head substrate so that a potential difference between the electrodes is reversed so that the height relationship of the potentials is reversed in a predetermined cycle, the head is formed. The charged colorant component in the ink supplied onto the substrate is agitated by reciprocating over both electrodes. By this stirring action, the colorant concentration on each electrode is made uniform, and the fixation of the colorant component to the electrodes is prevented.

The present invention can also be applied to the case of using a line scanning type ink jet recording head having an electrode array in which a plurality of electrodes are arranged on a head substrate. In that case, the potential of the electrode array is high or low. There is provided voltage applying means for applying a voltage so that a potential difference in which the relationship is reversed at a predetermined cycle is generated between the adjacent electrodes. Further, the voltage applying means selectively applies a voltage to the electrode array so that the first potential difference in which the potential level relationship is reversed in a predetermined cycle is generated between the adjacent electrodes when the ink droplets are not flying. However, when the ink droplets fly, a voltage is applied so that a second potential difference different from the first potential difference is generated between the adjacent electrodes.

Further, the voltage applying means applies a voltage to the electrode array so that a potential difference in which the level relationship of the potentials is reversed in a predetermined cycle is generated between the adjacent electrodes, and a mode other than the first mode. And a second mode in which a voltage is applied so that a potential difference that causes ink droplets to fly toward the recording medium during the period is generated between adjacent electrodes. In other words, the voltage applying means agitates the colorant component in the ink to the electrode array and applies a voltage for aggregating the colorant component in the ink on the target electrode, and the colorant component is applied on the target electrode. A second voltage is applied to cause the aggregated ink to fly as an ink droplet toward the recording medium.
And modes.

Specifically, for example, the voltage applying means has a structure capable of selectively applying at least three kinds of voltages of V0 <V1 <V2 to each electrode, and these voltages are applied to the electrode of interest and its surrounding electrodes. By applying the applied voltage to the colorant component, the step of stirring the colorant component and the step of aggregating onto the target electrode and the step of flying the agglomerated colorant component are performed in time division. For example, every other electrode that ejects ink drops is ejected after the colorant components in the ink are aggregated on these electrodes, and then the remaining ink is ejected on every other electrode. The ink droplets are ejected after the colorant components in the ink are aggregated.

Taking the case where the colorant component is positively charged as an example, in the step of aggregating the colorant component, the voltage of the electrode of interest is set to the lowest first voltage V0, and the adjacent electrodes on both sides are set to this voltage. By applying the high second voltage V1, the colorant component is aggregated on the target electrode (first mode). On the other hand, in the flight process of the ink droplets in which the colorant components are aggregated, the third voltage V2, which is sufficient for the ink droplets to be ejected, is applied to the target electrode, and the second voltage V1 lower than this is applied to the electrodes on both sides thereof.
Is applied to cause the ink, in which the colorant component has aggregated on the target electrode, to fly as an ink droplet (second mode). At this time, since the voltage V1 is applied to the electrodes on both sides of the target electrode, the escape of the ink from the target electrode can be suppressed to be small. After the ink droplets are ejected, the second voltage V1 is applied to the electrode on which the ink droplets are ejected, and the first voltage V0 is applied to the electrodes on both sides of the electrode to aggregate the colorant component on the adjacent electrodes. Then, the ink in which the colorant components have aggregated onto the electrode is ejected as an ink droplet.

When a charged colorant component is placed under a strong electric field for a long time, the charge is transferred between the colorant component and the electrode, the charge disappears, and it cannot be moved by an electric force. Since it becomes possible to adhere to the electrode, a voltage is applied in the present invention so that the target electrodes for aggregating the colorant component alternately move every other line, so that the fixation of the colorant component is prevented, As a result, good recording can be performed stably for a long time.

[0018]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a view showing the arrangement of an inkjet recording apparatus using a line scanning inkjet recording head according to an embodiment of the present invention. In the figure, a recording head 100 has a head substrate 1 having an electrode array 102 composed of stripe-shaped individual electrodes corresponding to respective image points arranged in a direction perpendicular to the plane of the drawing (main scanning direction).
01 and an upper lid 103 arranged on the upper lid 01, and the ink flow path 104 is formed by the head substrate 101 and the upper lid 103. Ink 106 is supplied to the ink flow path 104 from an ink recirculation mechanism 105 including a pump.
The ink 106 is obtained by suspending a positively chargeable colorant component together with a charge control agent, a binder, etc. in a colloidal state in an insulating solvent having a resistivity of 10 ⁸ Ωcm or more. While being transported to the flying position of the ink droplet in 104, a part is collected by the ink recirculation mechanism 105 from the collection port.

A drive circuit 107 is connected to the individual electrodes of the electrode array 102. The drive circuit 107 is configured to be able to selectively apply three types of voltages to each individual electrode, that is, a first voltage V0, a second voltage V1 and a third voltage V2 (V0 <V1 <V2). There is. These voltages V0, V1 and V2 are V1-V between the adjacent individual electrodes.
When a potential difference of 0 (first potential difference) is generated, the colorant components are aggregated but not caused to fly, and V2-V1 or V2
When a potential difference of −V0 (second potential difference) occurs, it is selected as a value at which an ink droplet containing a colorant component is ejected.

More specifically, the drive circuit 107 causes the electrode array 102 to have a first potential difference in which the level relationship of the potentials is alternately reversed at a predetermined cycle when the colorant components are aggregated (when ink droplets are not flying). Selectively applies the first voltage V0 or the second voltage V1 so that a voltage is generated between adjacent individual electrodes,
Further, when the ink droplets fly, a third voltage V2 that causes the ink droplets to fly toward the recording medium is applied. A specific configuration of the drive circuit 107 will be described in the second embodiment described later.

The recording paper 108 as a recording medium, which is arranged so as to face the tip of the recording head 100, passes in the direction indicated by the arrow while being in close contact with the recording drum 109 which also functions as a counter electrode. In a state where the ink is carried to a predetermined position on the electrode array 102 by the ink recirculation mechanism 105,
When a second voltage V1 is applied between a predetermined individual electrode (target electrode) and an individual electrode adjacent thereto according to an image signal to be recorded, an ink droplet 110 containing a colorant component is generated between the electrode array 102 and the recording drum 109. The electric field between them causes the image to fly onto the recording paper 108, and an image is recorded on the recording paper 108.

Next, a method of driving the electrode array 102 in this embodiment will be described with reference to FIG. This driving method shows an example in which all the individual electrodes of the electrode array 102 are divided into two and driven. That is, during driving, the electrode array 102 is divided into two groups of even-numbered individual electrodes 201 shown by diagonal lines and odd-numbered individual electrodes 202 shown in white, and each group is driven. 2 (A), (B), (C), and (D) show the voltage applied to each individual electrode at predetermined time intervals.

In a certain state, the first voltage V0 is applied to the group of the even-numbered individual electrodes 201 as shown in the timing chart of FIG. 2A, and the group of the odd-numbered individual electrodes 202 on both sides thereof is applied. It is assumed that the second potential difference is applied. As described above, for example, when the ink 106 contains a positively charged coloring material, V1> V0
Therefore, the colorant component is attracted to the even-numbered individual electrode 201 side and aggregates. FIG. 2B shows a state after a certain time T1 from this state. In this state, on the contrary, the second voltage V1 is applied to the group of the even-numbered individual electrodes 201, and the odd numbers on both sides thereof are odd. Since the first voltage V0 is applied to the second group of individual electrodes 202, the colorant component is attracted to the odd-numbered individual electrodes 202 side and aggregates.

FIG. 2 (C) further shows the time T1 from (B).
After that, and FIG. 2D shows the state after T1 from FIG. 2C, and as can be seen, there is a constant value in the group of the even-numbered individual electrodes 201 and the group of the odd-numbered individual electrodes 202. Voltage V0, alternately at time T1 intervals of
V1 is applied. In other words, the voltages V0 and V1 are applied to the individual electrodes so that a voltage difference between the adjacent individual electrodes in which the level relationship of the potentials is alternately inverted at the cycle of time T1, that is, V1-V0 and V0-V1. With the application of this voltage, the colorant component aggregates at the interval of time T1 on the individual electrode having the lower potential, and is agitated by alternately moving between the adjacent individual electrodes. Therefore, the charged colorant component can be effectively aggregated on the predetermined individual electrode, and the colorant component can be prevented from adhering to the individual electrode and its vicinity.

Next, at the time of image recording, a group of even-numbered individual electrodes 201 and an odd-numbered individual electrode 202 are respectively applied to a predetermined individual electrode by the drive circuit 107 according to the image signal to be recorded by the third voltage V2. Is applied, and the ink droplets 1 in which the colorant components have aggregated from the individual electrodes 1
10 flies toward the recording paper 108, and an image is recorded on the recording paper 108.

FIG. 3 is a timing chart of the voltage applied to the electrode array when the ink droplets are not flying and when they are flying in the present embodiment, and (I) at the time of flying indicates even-numbered individual electrodes 201 indicated by diagonal lines. Changes in applied voltage over time, and (II) is the odd numbered individual electrode 2 shown in white.
FIG. 3 is a diagram showing a temporal change of a voltage applied to 02.

When the power switch of the ink jet recording apparatus is turned on, all the individual electrodes of the electrode array 102 are maintained at the second voltage V1. At the start of recording, first, the first voltage V0 is applied to the group of even-numbered individual electrodes 201 that eject ink droplets. On the other hand, the odd-numbered individual electrodes 202 adjacent to the individual electrode 201 have a second
Voltage V1 is applied. When the colorant in the ink 106 is positively charged as described above, V1> V
Since the colorant component is 0, the colorant component is an even-numbered individual electrode 201.
It is attracted to the side and aggregates, and the colorant concentration near the individual electrode 201 increases. The above is the first mode.

After the first voltage V0 is applied to the even-numbered individual electrodes 201 for a time period indicated by T1 (aggregation time), the third voltage V2 is applied next. Where V2> V
Since the colorant component is 1, the colorant component aggregated near the even-numbered individual electrodes 201 is the third when the colorant is positively charged.
At the same time as being repulsed by the electric field formed between the individual electrode 201 and the ground potential of the recording drum 109, the colorant component whose density has increased from the tip of the individual electrode 201 is recorded as an ink droplet. It will fly toward the paper 108. The above is the second mode.

The third voltage V2 is applied for the time indicated by the maximum Tw. Since the flying amount of the ink droplet changes depending on the application time of the third voltage V2, it is possible to modulate the density of the image point. Therefore, depending on the gradation information (density information) of the image signal, as shown in FIG.
Gradation recording can be performed by changing the application time (flying time) of 2 in the range of 0 to Tw and performing so-called pulse width modulation. The second voltage V1 is applied to the electrode of the individual electrode 201 for which the data of the corresponding image signal is 0, that is, the electrode that does not cause ink droplets to fly.

In this way, the even-numbered individual electrodes 201
When the ink droplets have been ejected from, the ink droplets are ejected from the odd-numbered individual electrodes 202 next. Even in this case, the first voltage V0 is applied to the odd-numbered individual electrodes 202, and the second voltage V1 is applied to the even-numbered individual electrodes 201 on both sides of which the flying of the ink droplets has already finished, which is indicated by T1. Is applied. In this case, the colorant component aggregates in the vicinity of the odd-numbered individual electrodes 202 and the colorant concentration increases (first mode). In such a state, by raising only the applied voltage to the odd-numbered individual electrodes 202 to the third voltage V2, it is possible to cause the highly concentrated coloring material component to fly as an ink droplet from the tip of the individual electrode 202. Yes (second mode).

Image recording for one line is completed by the series of operations described above. By repeating such an operation, ink droplets are alternately ejected from the even-numbered individual electrodes 201 and the odd-numbered individual electrodes 202, and recording is sequentially performed for each line, so that a two-dimensional image is finally obtained. To record.

In this way, the even-numbered individual electrodes 20
The colorant component aggregates on the first electrode (first mode), and the ink droplet 110 flies from a predetermined electrode in accordance with the image signal (second mode). Then, the colorant component on the odd-numbered individual electrodes 202. Agglomerate (first mode) and the ink droplets 110 fly according to the image signal (second mode), which is repeated in a cycle of T1 + T1.
An image having a resolution determined by the 02 pattern is recorded on the recording paper 108.

As described above, according to the present embodiment, the coloring material can be sufficiently supplied to the predetermined position of the electrode array, and the coloring material can be prevented from adhering to the vicinity of the individual electrodes, which causes clogging. Strong and high-resolution recording can be performed.

The agglomeration / stirring operation of the colorant components shown in FIG. 2 may be performed at any time, for example, when the recording apparatus is started, or may be performed periodically during the operation of the recording apparatus. Good.

(Second Embodiment) FIG. 4 is a diagram for explaining a driving method of the electrode array 102 in the second embodiment, and is (A), (B), (C), (D). Indicates a voltage applied to each individual electrode at a predetermined time interval. This embodiment is an example in which all the individual electrodes of the electrode array 102 are divided into two and driven as in the first embodiment, and the operation at the time of recording is different from that of the first embodiment. Specifically, FIG.
(A), (B), or (C), (D) and FIG.
(C) corresponds, and after the first mode including the applied voltage patterns of FIGS. 4 (A) and 4 (C), FIG.
The difference from FIG. 2 is that the second mode consisting of the applied voltage pattern of (D) is inserted. Here, the first mode is a mode in which the colorant components are aggregated and stirred, and the second mode is
The mode is a mode in which the ink droplets in which the colorant components are aggregated are ejected.

FIG. 5 is a timing chart of the voltage applied to the electrode array when the ink droplets are not flying and when they are flying in the present embodiment. (I) at the time of flying indicates even-numbered individual electrodes 201 indicated by diagonal lines. Changes in applied voltage over time, and (II) is the odd numbered individual electrode 2 shown in white.
FIG. 3 is a diagram showing a temporal change of a voltage applied to 02. In FIG. 5, (A), (B), (C),
The timing shown in (D) is as shown in FIG.
This corresponds to the timing of (C) and (D).

When the power switch of the ink jet recording apparatus is turned on, all the individual electrodes of the electrode array 102 are maintained at the second voltage V1. At the start of recording, first, as shown in the timing of (A), the first voltage V0 is applied to the group of the even-numbered individual electrodes 201 that eject the ink droplets first. On the other hand, the second voltage V1 is applied to the odd-numbered individual electrodes 202 adjacent to the individual electrode 201. When the coloring material in the ink 106 is positively charged as described above, since V1> V0, the coloring material component is attracted to the even-numbered individual electrode 201 side and aggregates, and the individual electrode 201 The colorant density in the vicinity increases.

After the first voltage V0 is applied to the even-numbered individual electrodes 201 for a time period indicated by T1 (aggregation time), the third voltage V2 is applied next as shown in (B). . Since V2> V1 here, when the colorant is positively charged, the colorant component aggregated in the vicinity of the even-numbered individual electrodes 201 repels the third voltage V2 and, at the same time, is recorded with the individual electrodes 201. By being attracted by the electric field formed between the drum 109 and the ground potential, the colorant component having the increased density flies from the tip of the individual electrode 201 toward the recording paper 108 as an ink droplet.

The third voltage V2 is applied for the time indicated by the maximum Tw. Since the flying amount of the ink droplet changes depending on the application time of the third voltage V2, it is possible to modulate the density of the image point. Therefore, according to the gradation information (density information) of the image signal, as shown in FIG.
Gradation recording can be performed by changing the application time (flying time) of 2 in the range of 0 to Tw and performing so-called pulse width modulation. The second voltage V1 is applied to the electrode of the individual electrode 201 for which the data of the corresponding image signal is 0, that is, the electrode that does not cause ink droplets to fly.

In this way, the even-numbered individual electrodes 201
When the ink droplets have been ejected from, the ink droplets are ejected from the odd-numbered individual electrodes 202 next. Also in this case, as shown in FIG. 4C, the odd-numbered individual electrodes 2
The first voltage V0 is applied to 02, and the second voltage V1 is applied to the even-numbered individual electrodes 201 on both sides of which the ink droplets have already finished flying for the time indicated by T1. In this case, the colorant component aggregates in the vicinity of the odd-numbered individual electrodes 202 and the colorant concentration increases. In this state, next, as shown in FIG. 4D, by increasing only the applied voltage of the odd-numbered individual electrodes 202 to the third voltage V2, the coloring agent component having a high concentration from the tip of the individual electrode 202 is increased. Can be ejected as ink droplets.

The above-mentioned FIGS. 4 (A), (B), (C),
The image recording for one line is completed by the series of operations in (D). By repeating such an operation, ink droplets are alternately ejected from the even-numbered individual electrodes 201 and the odd-numbered individual electrodes 202, and recording is sequentially performed for each line, so that a two-dimensional image is finally obtained. To record.

In this driving method, as the recording time T0 for forming one image point, at least the aggregation time T1 +
The maximum flight time Tw is required. Further, since one individual electrode is separately used for aggregation and for flight, and ink droplets cannot be simultaneously ejected next to each other while the colorant components are being aggregated, it is necessary to divide into at least two. Recording one line requires at least twice as long as the recording time T0. The recording time becomes longer due to the division drive and the provision of the aggregation time T1. However, by applying a high voltage to the adjacent electrode as an electrode for aggregation, the coloring material component can be efficiently placed near the electrode to be recorded. It becomes possible to aggregate. Also, the aggregation time T1
By providing the above, it is possible to stably and continuously supply the ink.

From the above, according to the present embodiment, it becomes possible to stably and stably record the dark image points having a large agglutination effect. Further, in the present embodiment, the individual electrodes to which the first voltage V0 is applied are constantly moving during recording, and the colorant components are agitated, so that the colorant components aggregate on the same individual electrode for a long time. Never keep going. Therefore, the ink does not stick to the individual electrodes, and stable recording can be realized for a longer time.

Next, a configuration example of the drive circuit 107 for realizing the above-described drive method will be described with reference to FIGS. 6 and 7. FIG. 6 is a block diagram showing the overall configuration of the drive circuit 107. Each individual electrode of the electrode array 102 is connected to the output terminals OUT1 to OUT5 of the drive circuit 107. Outputs are derived from the high voltage drivers 21 to 25 to the output terminals OUT1 to OUT5, respectively. In addition,
Although only five output terminals OUT1 to OUT5 are shown in FIG. 6, actually, the same number of output terminals as the number of individual electrodes to be driven at the same timing are provided. In FIG. 6, parts other than the high voltage drivers 21 to 25 are logic control circuit parts,
It operates at a voltage of 5 V or less.

First, the logic control circuit will be briefly described. Since the high voltage drivers 21 to 25 need to switch and output at least three types of voltages, that is, the first voltage V0, the second voltage V1 and the third voltage V2, at least 2 bits are required for the switching control. Data is required. This 2-bit data is indicated by the input data DAT1 and DAT2 in FIG. 6, and is supplied from the circuit at the preceding stage (not shown). These input data DAT1 and DAT2 are converted into signals for controlling the high voltage drivers 21 to 25 through the circuits having exactly the same configuration.

First, the operation relating to the input data DAT1 will be described. The input data DAT1 is supplied together with the clock signal CLK1 signal from the previous circuit in the same number as the number of individual electrodes driven at the same timing, and the latches 31 to 35 are supplied.
Are transferred by a clock signal CLK1 in a shift register configured by cascading. Input data DAT1
Are supplied for a specified number, then the latch signal LATC
Latch 31 supplied with H1 and forming a shift register
The data transferred to .about.35 are output from the output terminals of the latches 41 to 45 in the next stage. The control data output from the output terminals of the latches 41 to 45 are gated by the recording timing signal EN1 by the gates 51 to 55, and then supplied to one input terminals of the high voltage drivers 21 to 25, respectively.

The operation regarding the input data DAT2 is exactly the same. That is, the input data DAT2 is supplied together with the CLK2 signal from the previous circuit by the same number as the number of individual electrodes driven at the same timing, and the input signal DAT2 is supplied to the shift register constituted by the cascaded latches 61 to 65 by the clock signal CLK2. Transferred. Input data DAT
When the specified number of 2 is supplied, the next latch signal LAT
Latch 6 supplied with CH2 and forming a shift register
The data transferred to 1 to 65 are latches 71 to 75 of the next stage.
It is output from the output terminal of. The control data output from the output terminals of the latches 71 to 75 are gated by the recording timing signal EN2 by the gates 81 to 85, and then supplied to the other input terminals of the high voltage drivers 21 to 25, respectively.

FIG. 7 is a circuit diagram specifically showing one of the high voltage drivers 21 to 25. This high-voltage driver will be briefly described. When the control signal CNT1 supplied from the gates 51 to 55 in FIG. 6 becomes high level, a current flows through the control resistor 97 to the base of the first transistor (Tr1) 91, and the transistor 91 is turned on. When the transistor 91 is turned on, the collector voltage to which the power supply voltage + V is applied via the load resistance 93 (resistance value R1) becomes 0V, and 0V is output to the output terminal OUT via the resistance 95 (resistance value R0). To be done. The collector of the second transistor 92 (Tr2) has a resistor 94 (resistance value R
Since it is connected to the collector of the transistor 91 via 2), when the transistor 91 is on, the voltage output from the output terminal OUT is 0 V regardless of whether the transistor 92 is on or off. The base of the transistor 92 is connected to the gates 81 to 81 of FIG.
The control signal CNT2 from 85 is input.

Transistor 91 is off, transistor 9
When 2 is off, the power supply voltage + is almost applied to the output terminal OUT.
The value of V will appear. This is because the load connected to the output terminal OUT of the high-voltage driver is the individual electrode of the electrode array 102 and is almost a capacitive load, and the resistance value R0 of the resistor 95 that also serves to prevent discharge is the load resistor 93. This is because the resistance value R1 is much larger than the resistance value R1. On the other hand, when the transistor 91 is off and the transistor 92 is on, a voltage of approximately V * R2 / (R1 + R2) appears at the output terminal OUT. In Table 1,
I have summarized these relationships.

[0050]

[Table 1]

That is, the output of this high-voltage driver is 0 V as the first voltage V0 and V * R as the second voltage V1.
2 / (R1 + R2), and + V is obtained as the third voltage V2. As an example of a specific value, + V = 400
V, R1 = R2 = 1 MΩ, R0 = 10 MΩ
0 = 0V, V1 = 200V, V2 = 400V are obtained.

In practice, a DC bias voltage (referred to as Vb) of about 1 kV is superimposed on the signal voltage of several 100 V output from the high voltage driver shown in FIG.
The ink droplets are ejected by being applied between the two individual electrodes and the recording drum 109. DC bias voltage V
In order to superimpose b, for example, the recording drum 109 may be insulated from the ground potential and connected to a DC bias power source of about -1 kV, or the surface of the recording drum 109 may be formed of an insulator, a wire charger or a solid state. The surface of the insulator or the recording paper pressed onto the recording drum 109 by the ion generator may be charged to about -1 kV.

With the above-mentioned configuration, Vb during standby
A bias of + V1 = 1.2 kV is applied, and the same effect as that of Vb + V0 = 1 kV is applied to the individual electrodes that aggregate the colorant components, and Vb + V2 = 1.4 kV is applied when the ink droplets fly. Is obtained. Further, in this way, the operating voltage of the drive circuit can be suppressed to several hundreds V, so that the IC can be easily formed. IC drive circuit
As a result, a large number of drive circuits can be arranged on the head, so that a small inkjet recording device can be realized.

(Third Embodiment) In the second embodiment,
The two-division driving method has been described in which all the individual electrodes of the electrode array 102 are divided into two groups, and recording is performed in one group and then in the other group. In this method, the aggregation time T1 of the colorant component and the flight time that is the application time Tw (maximum value) of the third voltage V2 are arbitrary values. Although such two-division driving is practically acceptable, the aggregation time T1 is an integral multiple of the maximum value Tw of the application time of the third voltage V2 in consideration of the surrounding conditions such as the image data generation circuit. More desirable.

In this embodiment, T1 is thus an integral multiple of Tw, and its timing chart is shown in FIG.
Shown in. FIG. 8A is an example of T1 = Tw = T. In this case, the time required to form one image point is 2T,
Further, since the 2-division driving is performed, it takes 4T to record one line. FIG. 8B shows T1.
= 2Tw, FIG. 8C is an example of T1 = 3Tw. When the density of the ink used is low or when the third voltage V2 is increased, the aggregation time T is thus compared to the flight time Tw.
It is desirable to lengthen 1. 8 (b) (c)
In the case of, the recording time for one line is the recording time T for one image point.
6 times and 8 times respectively.

The drive timing of the drive circuit 107 shown in FIGS. 6 and 7 will be described with reference to FIG. 9 by taking the case of FIG. 8A as an example. SYNC0 is a synchronization signal of cycle T, and the drive circuit 107 operates based on this synchronization signal SYNC0.

Timing (A): When the synchronizing signal SYNC0 rises, the data D together with the clock signal CLK10.
Latch 3 in which AT11 constitutes the shift register in FIG.
1-35. The data DAT11 is a signal for selecting an electrode for aggregating the colorant, and in this example, 2
Since division drive is performed, as shown in the figure, 1010
Is a number sequence in which 1 and 0 are alternately arranged.

Timing (B): Next, the synchronization signal SYN
Latch signal LATCH10 according to the timing of C0
Is supplied. By this latch signal LATCH10,
The transferred data is output to the output side of the latches 41 to 45. When the latch signal LATCH10 rises, the enable signal EN11 is output next.
The enable signal EN11 is a pulse that sets the time for causing the colorant components of the ink to aggregate, and in this example, the synchronization signal S
The pulse has a length substantially the same as the pulse cycle of YNC0. When the enable signal EN11 is output, the output from the gates 51 to 55 to which 1 is transferred by the data DAT11 becomes 1, so that the transistor 91 is turned on and 0V, that is, the first voltage V0 is supplied to the individual electrodes. To be done. Since the outputs from the gates 51 to 55 transferred by the data DAT11 become 0, the transistor 91 is turned off. Further, at this time, the enable signal EN21 is not output and is always 0, so that all the transistors 92 are turned on. Therefore, the output from the individual electrode to which 0 is transferred by the data DAT11 becomes the second voltage V1. That is,
At the timing of (B), the coloring material component in the ink is condensed around the target electrode that causes the ink droplet to fly.

Further, at the timing of (B), the latch 61
The transfer of the data DAT21 to ~ 65 is also performed at the same time. At this time, in the data DAT21, 1 is transferred to the electrode that causes the ink droplet to fly, and 0 is transferred to the electrode that does not fly according to the image signal. However, the image data is sent only to every other electrode where the colorant component is currently aggregated, and the data of 0 is transferred to the other electrodes where the aggregation is not currently performed.

Timing (C): At this timing (C), the data transferred at the timing (B) is first latched by the latch signal LATCH 20.
It is output from 5. Here, the enable signal EN21
Is supplied. The enable signal EN21 is a pulse having a pulse width Tw, and is a signal for applying the third voltage V2 to the individual electrode during the time Tw. Tw is determined by the flight characteristics of the ink droplets, but is the same as the recording time T for one image point at maximum. On the other hand, enable signal EN1
Since 1 is not output and is always 0, the transistor 91 remains off, and the first voltage is not applied to the individual electrode.

The voltage of each individual electrode is controlled by turning on / off the transistor 92, and the third voltage V2 is applied to the electrode that causes the ink droplet to fly, and the second voltage V1 is applied to the electrode that does not fly.
Are output respectively. At this time, the output time of the third voltage V2 is Tw. When this time Tw elapses, the second voltage V1 is output to all the individual electrodes. Further, the data DA transferred at the timing of (B)
Since T21 is 0 for the electrodes other than the electrode to which the first voltage V0 is applied at the timing of (B), T21 is T
Even when the third voltage V2 is applied during the period of w, the voltage is the second voltage V1 except for the electrode of interest.

With the above operation, recording for every other image point in one line is completed. Then record the other half of one line. At the timing of (C), at the same time as recording the first half of one line, data transfer for recording the remaining half is also performed. The latch 31 in which the data DAT11 and the clock signal CLK10 form a shift register
~ 35. The data DAT11 is a signal for selecting an electrode for aggregating the colorant component as described above. The electrode for aggregating the colorant component at the next timing (D) is the other half electrode of the electrode that first agglomerates, so as shown in the figure, 0 and 1 are arranged alternately with 0101 ... It becomes a number sequence.

Timing (D): Next, the synchronization signal SYNC
The latch signal LATCH10 is synchronized with the timing of 0.
Is supplied. By this latch signal LATCH10,
The transferred data is output to the output side of the latches 41 to 45. When the latch signal LATCH10 rises, the enable signal EN11 is output again. When the enable signal EN11 is output, the data D
The transistor 91 connected to the gates 51 to 55 transferred by the AT11 is turned on and 0V is applied to the individual electrodes.
That is, the first voltage V0 is supplied. Data DAT1
The transistor 91 connected to the gates 51 to 55 to which 0 is transferred by 1 is turned off. At this time, since the enable signal EN21 is always 0, all the transistors 92 are turned on. Therefore, the output from the individual electrode to which 0 is transferred by the data DAT11 becomes the second voltage V1.
That is, at the timing of (D), the ink is aggregated around the electrode of interest to which the ink droplet is next ejected, that is, the periphery of the remaining electrode other than the aggregate of the colorant component first.

Further, at the timing of (D), the latch 61
The transfer of the data DAT21 to ~ 65 is also performed at the same time. At this time, in the data DAT21, 1 is transferred to the electrode that causes the ink droplet to fly, and 0 is transferred to the electrode that does not fly according to the image signal. However, the image data is sent only to every other electrode where the colorant component is currently being aggregated, that is, only to the electrodes other than the electrode where the colorant component was first aggregated and the ink droplets were ejected, and other than that. Data of 0 is transferred to the electrode of.

Timing (E): At this timing (E), the data transferred at the timing (D) is first latched by the latch signal LATCH 20 to the latches 71 to 7.
It is output from 5. Here, the enable signal EN21
Is supplied. Since the enable signal EN21 is always 0, the transistor 91 remains off, and the first voltage V0 is not applied to the individual electrode. The voltage of each individual electrode is controlled by turning on / off the transistor 92,
The third voltage V2 is output to the electrode that causes the ink droplet to fly, and the second voltage V1 is output to the electrode that does not fly. The output time of the third voltage V2 is Tw, and when this time Tw elapses, the second voltage V2 is applied to all the individual electrodes.
1 is output. Further, the DAT 21 transferred at the timing of (D) is 0 for the electrodes other than the electrode to which the first voltage is applied at the timing of (D), so that the third voltage V2 is kept during the period of Tw. Even if applied, the target electrode is at the second voltage V3.

With the above operation, the remaining 1 of 1 line
The recording for every image point is also completed, and thus the recording for one line is completed. Also, at the timing of (E), 2
The aggregation data of the line is also transferred at the same time, and the same operation is repeated thereafter to form an image of many lines.

Although FIG. 9 shows the timing from the start of recording of the first line, the state shown by the dotted line in the figure is the state in which continuous recording is being performed. Further, this timing chart is an example, and some other timings can be considered even if the drive circuit 107 has the same configuration. For example, even if the enable signals EN11 and EN21 are always output and the data DAT11 and DAT21 are alternately set to 0 in each recording cycle, a completely similar driving method can be realized. Such an example is also included in the present invention as long as the final driving method is the same.

Further, as shown in FIGS. 8 (b) and 8 (c), when it is desired to make the aggregation time longer, between the timings (A) and (B) in the timing chart of FIG. Between (D), the timing at which only the enable signal EN11 is output may be inserted.

FIG. 10 shows an example of a timing chart when the aggregation time is twice the flight time as shown in FIG. 8B. Similarly, by increasing the period of the enable signal EN11, a driving method with a longer aggregation time can be realized.

(Fourth Embodiment) As described in the third embodiment, when the coagulation time T1 of the colorant components is set to an integral multiple of the ink droplet flight time Tw, substantially more multi-division driving is performed. Is equivalent to doing. For example, in the case of the example in FIG. 8A, the recording time T for one image point is ¼ of the recording time for one line, which is substantially equivalent to performing 4-division driving. . Therefore, since the recording speed does not decrease, four-division driving may be performed. Similarly, FIG.
The example of (b) is equivalent to performing 6-division driving, and the example of (c) is equivalent to performing 8-division driving.

In the fourth embodiment, since the aggregation of the coloring material component becomes more random, the effect of preventing the fixing of the coloring material component to the electrode becomes greater. The driving method in this embodiment will be described with reference to the timing charts of FIGS. 11 to 13. 11 to 13 show the relationship between the electrode array 102 and the applied voltage at each timing.

FIG. 11 shows an example in which five-division driving is performed, and the same voltage is applied to each of the five electrodes from the individual electrodes shown by hatching. In the example of FIG. 8A, recording can be performed by four-division driving when one cycle is required for aggregation of the colorant components, but five-division driving is performed by the driving method shown in FIG. Similarly,
FIG. 12 shows an example in which the colorant components are aggregated for three cycles. This is an example corresponding to the 8-division driving of FIG. 8C, but can be realized by the 10-division driving as shown in FIG. Further, FIG. 13 shows an example in which every 7 electrodes are driven at the same timing to perform aggregation for 5 cycles.
It will be divided drive.

As described above, in the fourth embodiment, the aggregation of the colorant components becomes more random, and the effect of preventing the colorant components from sticking to the individual electrodes is further increased. The driving method of FIGS. 11 to 13 can be easily realized by the configuration of the driving circuit shown in FIG. That is, in the timing chart of FIG. 9, the signal for aggregation and the recording data are transferred every cycle, and the enable signal EN11 for aggregation is transmitted.
And the enable signal EN21 for flight were also output at different timings. However, by slightly changing this timing, for example, the driving method of FIG. 11 is realized by transferring the aggregating data and the recording data in every cycle and latching them in every cycle, and continuously outputting the enable signals EN11 and EN21 in every cycle. it can. The driving method shown in FIGS. 11 to 13 is an example, and many other driving methods are possible. However, if the applied voltage is changed between the adjacent electrode and the electrode that is about to fly, and the flight is performed after the aggregation, FIG.
Even if the timing is different from that shown in FIG. 13, it is all included in the present invention.

The present invention is not limited to the above-described embodiment, but can be variously modified and implemented without departing from the spirit thereof. For example, in the above-described embodiment, the example using the line scanning type ink jet recording head having an electrode array in which a large number of stripe-shaped individual electrodes are arranged and performing recording for one line simultaneously or in a plurality of times has been described. . However, the present invention is not limited to the case of using a multi-head that ejects ink droplets from such a large number of positions, and ejects the ink droplets from one location so that the head moves relative to the recording medium in the main scanning direction. The present invention can also be applied to the case where a single head is used for recording one line while moving it manually. In the case of such a single head, at least two individual electrodes are provided adjacent to each other on the head substrate, and a potential difference is generated between the two electrodes such that the relationship of potential level is reversed at a predetermined cycle. It is possible to achieve the intended purpose by applying a voltage to the agglomerates and agitating the colorant components.

[0075]

As described above, according to the present invention, in the ink jet recording apparatus for recording by causing the coloring material component in the ink to aggregate and fly by electrostatic force, the coloring material on each electrode on the head substrate It is possible to make the density uniform and prevent the colorant component from sticking to the electrode, and perform stable recording.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an applied voltage pattern of an electrode array for explaining the driving method according to the first embodiment.

FIG. 3 is a timing chart of applied voltages to the electrode array for explaining the driving method according to the first embodiment.

FIG. 4 is a diagram showing applied voltage patterns of an electrode array for explaining a driving method according to a second embodiment.

FIG. 5 is a timing chart of applied voltages of an electrode array for explaining the driving method according to the second embodiment.

6 is a block diagram showing a specific configuration example of a drive circuit in FIG.

7 is a circuit diagram showing a specific configuration example of the high-voltage driver in FIG.

FIG. 8 is a timing chart of applied voltages of an electrode array for explaining the driving method according to the third embodiment.

FIG. 9 is a timing chart showing an operation example of the drive circuit according to the third embodiment.

FIG. 10 is a timing chart showing another operation example of the drive circuit according to the third embodiment.

FIG. 11 is a diagram showing an applied voltage pattern of an electrode array for explaining the first driving method according to the fourth embodiment.

FIG. 12 is a diagram showing an applied voltage pattern of an electrode array for explaining a second driving method according to the fourth embodiment.

FIG. 13 is a diagram showing an applied voltage pattern of an electrode array for explaining a third driving method according to the fourth embodiment.

[Explanation of symbols]

100 ... Inkjet recording head 101 ... Head substrate 102 ... Electrode array 103 ... Top lid 104 ... Ink flow path 105 ... Ink recirculation mechanism 106 ... Ink 107 ... Drive circuit 108 ... Recording paper 109 ... Recording drum 110 ... Ink drop 201 ... First individual electrode 202 ... Second individual electrode

(72) Inventor Hideyuki Nakao 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center Co., Ltd. (72) Koichi Ishii 1 Komukai-shiba, Kawasaki-shi, Kanagawa 1-share Corporate Toshiba Research and Development Center (72) Inventor Yasuo Hosaka 1 Komukai Toshiba Town, Komukai-shi, Kawasaki City, Kanagawa Prefecture Toshiba Research and Development Center (56) Reference JP-A-9-123459 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/06

Claims (3)

(57) [Claims] 1. An ink in which a colorant is dispersed in a solvent is supplied onto a head substrate, and an electrostatic force is applied to the colorant component in the ink to direct an ink droplet containing at least the colorant component to a recording medium. In an inkjet recording apparatus that performs recording by ejecting ink droplets, the potential of at least the first and second electrodes provided on the head substrate and the potentials of the first and second electrodes when ink droplets are not flying By applying a voltage so that a first potential difference is generated between both electrodes, the height relationship of which is reversed in a predetermined cycle .
And agitation of ink droplets by the first and second electrodes
And a voltage is applied so that a second potential difference, which is different from the first potential difference, is generated between the electrodes when the ink droplets are ejected .
An ink jet recording apparatus comprising: a voltage applying unit that causes ink droplets to fly . 2. An ink in which a colorant is dispersed in a solvent is supplied onto a head substrate, and an electrostatic force acts on the colorant component in the ink to direct ink droplets containing at least the colorant component to a recording medium. In an ink jet recording apparatus for performing recording by ejecting ink droplets, the electrode array provided on the head substrate and having a plurality of electrodes arranged thereon and the electrode array have high and low potentials when ink droplets are not flying. By applying a voltage so that a first potential difference in which the relationship is reversed at a predetermined cycle is generated between the adjacent electrodes ,
By causing the ink droplets to be agitated and agglomerated by the pole array , a voltage is applied so that a second potential difference different from the first potential difference is generated between the adjacent electrodes when the ink droplets fly .
An ink jet recording apparatus , comprising: a voltage applying unit that causes ink droplets to fly by the electrode array . 3. An ink in which a colorant is dispersed in a solvent is supplied onto a head substrate, and an electrostatic force acts on the colorant component in this ink to direct ink droplets containing at least the colorant component to a recording medium. In an ink jet recording apparatus for performing recording by flying by flying with an electrode array formed by arranging a plurality of electrodes on the head substrate, and the potential relationship of this electrode array is reversed at a predetermined cycle. By applying a voltage so that a potential difference that occurs between adjacent electrodes occurs , the electrode array stirs ink droplets.
A first mode to perform the aggregation and拌, especially potential difference of flying toward the recording medium ink droplets in the period other than the first mode to apply a voltage to occur between adjacent electrodes
An ink jet recording apparatus further comprising a voltage applying unit having a second mode in which ink droplets are ejected by the electrode array .