JP3226882B2 - Recording head and image recording apparatus using the recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing industry that requires high-speed output of high-quality images, an office, a printer industry based on personal requirements, and a low-cost general-purpose output device that uses various types of recording paper. The present invention relates to an ink jet recording apparatus for obtaining an output image on a recording sheet that can meet a wide range of needs up to the consumer goods industry.

[0002]

2. Description of the Related Art A slit jet recording method (Susumu Ichinose et al .: "Slit Jet Recording Method"), the first non-impact printing technology symposium, p. 119
-124, 1984). This slit jet method will be described with reference to FIGS.

As shown in FIGS. 9 (a) and 9 (b), the recording head comprises a head section 911 and an opposing electrode section 912 arranged opposite to the head section 911.
Reference numeral 11 denotes an ink discharge port 901 formed in a single slit-shaped opening, an upper substrate 902 and a lower substrate 903 forming the ink discharge port 901, and a slit divided into recording pixel units on the lower substrate 903. The recording electrodes 904 arranged in the longitudinal direction and each of the recording electrodes 9 based on an image recording signal.
The recording circuit 904 includes a control circuit 907a for controlling whether or not to apply a voltage to the recording electrode 904, and a high-voltage power supply 906a for supplying a constant voltage pulse to a selected electrode of the recording electrode 904.

The counter electrode portion 912 is composed of a support 917 and a common electrode 905 provided on the support 917. The common electrode 905 faces the ink discharge port 901 and has a small gap. The recording paper 910 intervenes in the minute gap. In addition, a control circuit 907b controls the counter electrode unit 912 so as to supply a constant voltage pulse having a polarity opposite to that of the recording electrodes in synchronization with a driving cycle of the recording electrode array (hereinafter, one recording line) in the head unit 911. And a high-voltage power supply 906b.

Hereinafter, the longitudinal direction of the slit of the ink discharge port 901 is defined as the main scanning direction, and the intervening direction of the recording paper 910 that intersects with the longitudinal direction is defined as the sub-scanning direction. Then, the ink 908 having a high resistance value is filled in the ink discharge port 901 of the head section 911, and the head section 911 and the counter electrode section 912 are driven. Then, as shown in FIG. 9B, a predetermined constant voltage pulse is simultaneously applied between the recording electrode 904 and the common electrode 905, whereby charges are supplied from the recording electrode 904 to the ink 908 in the head unit 911, In addition, an electric field is generated between the common electrode and the recording electrode. The charged ink 908 receives Coulomb force in the generated electric field and is discharged in the direction of the counter electrode portion 912, so that the leap ink 909 adheres to the recording paper 910 and penetrates to obtain a desired image output. Become.

In such a conventional slit jet recording method, the nozzle used for ink jet recording is replaced with the single slit-shaped ink discharge port 901 elongated in the main scanning direction, thereby eliminating the restriction of the resolution by the nozzle. At the same time, the cleaning of the ink discharge ports 901 can be facilitated. Further, the slit jet recording method uses a plurality of the recording heads, supplies the inks 908 of different colors into the respective ink ejection ports 901, drives each of them in the main scanning direction based on a recording image signal, and performs recording. By repeatedly scanning the paper 910 in the sub-scanning direction by a predetermined amount, color output printing can be easily obtained.

[0007]

However, the recording head and the recording apparatus in the conventional slit jet recording method have the following problems. (1) In the head section, recording electrode patterns divided in recording pixel units and arranged in the main scanning direction, wiring to a circuit for independently controlling the electrodes and selectively applying a voltage to drive the same, Since the functions of the ink supply means such as an ink chamber for storing a fixed amount of ink and an ink tank or an ink supply path are integrated, the structure of the head portion becomes very complicated, and the production yield is poor.

(2) In the head portion, the recording electrode is always in direct contact with the ink in order to supply electric charge to the ink, and since the electrode is finely divided, it is easily corroded by reactions such as electrolysis and oxidation. The durability is not good. (3) When printing, a constant voltage pulse is applied only to the recording electrodes from which ink is ejected, so that a large potential difference is generated between the recording electrodes from which ink is ejected and the recording electrodes from which ink is not ejected. Since the recording electrodes supply electric charges to the ink, the surface cannot be insulated. In addition, since the adjacent recording electrodes are electrically connected via the ink, a voltage is applied between the adjacent electrodes. This causes a drop, and it is actually difficult to obtain a potential difference required for ink ejection. Therefore, the selectivity of the ink ejection position is deteriorated. As a countermeasure, it is conceivable to previously set a large voltage value to be applied to the recording electrode at the position where ink is ejected, or to set a large voltage value to be applied to the common electrode. There is a risk of causing a discharge between the common electrodes on the electrode part.

(4) Since the electric field generated in the recording head is generated by applying a voltage to the divided recording electrodes on the head portion side and a common electrode on the counter electrode portion side, the voltage applied portion during the operation is static. The electric field is concentrated on the head portion side where the divided thin electrodes are arranged, but is dispersed in a plane on the counter electrode side. Therefore, the ink discharge position at the ink discharge port in the head portion is accurately positioned, but becomes unstable at the landing position of the flying ink toward the counter electrode portion due to the spread of the electric field. Therefore, misalignment of ink dots easily occurs in an output image as a device, and it is difficult to obtain high-quality output.

(5) At the time of multi-color printing such as color printing, it becomes possible by stacking and arranging recording heads corresponding to at least the respective colors in the short direction of the slit discharge ports and driving them independently. Since the recording head and drive circuit for each color are required independently, the cost becomes high as a device,
In addition, it becomes large. At this time, the relative printing dot deviation of each color in the main scanning direction on the recording paper (hereinafter, printing deviation)
In order to reduce as much as possible, the heads of the respective colors adjust the positions of the recording electrodes arranged in the main scanning direction so that they are aligned with the scanning direction of the recording paper, that is, the sub-scanning direction. Must be incorporated into This also applies to the accuracy of feeding the recording paper in the sub-scanning direction. Since the pitch of the adjacent electrodes of the recording electrodes is set to be equal to that of the recording pixels, the pitch of the adjacent electrodes is about 85 μm for a recording head having a recording resolution of 300 dpi, for example. Therefore, for example, if the allowable range of the displacement is ± 20%, ± 17%
Position accuracy within μm must be maintained. However, assuming that the recording electrodes of each head are aligned with reference to the substrate end face of the head, the lower substrate on which the recording electrodes are arranged as the current head configuration is formed by patterning the electrodes on a copper-clad laminated printed board, a glass substrate, or the like. Since it is a process of cutting using dicing or a cutter after the polishing, the limit is about ± 50 μm in consideration of the positional accuracy between the recording electrode and the end face of the substrate and the mounting accuracy at the time of assembling in the apparatus. Also, the feeding of the recording paper in the sub-scanning direction is caused by a positional deviation at the time of transfer from the recording paper supply unit to the transport roller, a transport roller shape error, a balance error of a pressure distribution between rollers, and the like.
The occurrence of skew cannot be denied, and this can be a factor that causes printing misalignment more than the positioning of the head.

Therefore, when a plurality of recording heads are incorporated in the apparatus, it is extremely difficult to adjust the positions of the recording electrodes in each head unit. Inevitably, if a fine adjustment mechanism is included, the cost cost increases, and the manufacturing time also increases due to the long adjustment time. (6) In many cases, the surface of the recording paper is charged due to friction between the recording papers when the paper is taken out of the bundle of recording papers by the automatic sheet feeder and friction between the recording paper and the rollers during conveyance, and the distribution is uneven. is there. In such a state, when driving the recording head, an unnecessary electric field is generated between the recording head and the common electrode, thereby forming a defective dot such as making the dot diameter non-uniform or discharging ink at unnecessary portions. As a result, the output image is significantly deteriorated.

[0012]

In order to solve the above-mentioned problems, a recording head according to the present invention has a common arrangement near a slit-shaped ink ejection port in a head portion, and is divided corresponding to recording image pixels. An ink supply means for supplying ink to the ink ejection port of the head unit, a power supply for supplying a constant voltage between the common electrode and the recording electrode, and a power supply from the power supply. There is provided a driving means for selectively applying a voltage to the recording electrode in accordance with a recording image signal by controlling a voltage.

The recording head is used as a recording device, and recording paper is supplied to a minute gap between an ejection port provided in the recording head and an opposing electrode, and scanning is performed in synchronization with driving of the recording head. And a recording paper conveying means for causing the recording paper to be conveyed. That is, in the recording head, by arranging the head portion as a common electrode and arranging the divided recording electrodes on the counter electrode side, the structure of the head portion can be simplified, and manufacturing restrictions can be reduced, thereby improving the yield. Therefore, it is possible to improve the maintainability of the recording head and reduce the manufacturing cost.

Further, since the divided recording electrode side is disposed on the opposite electrode side, it does not come into contact with ink, and it is possible to perform insulation treatment on the recording electrode surface, so that a high insulating property is provided between adjacent recording electrodes. Can be secured. As a result, deterioration of the electrodes and discharge between the electrodes can be prevented, and the life of the recording head can be extended. Further, the potential difference between the recording electrode that ejects ink and the recording electrode that does not eject ink can be increased, so that the selectivity of the ink ejection position can be stabilized.

Further, since the electric field concentrates on the recording electrode side on the counter electrode, which is the end point on the ink ejection direction side, the accuracy of the ink landing position is improved and the quality of the output image can be improved. Further, a plurality of recording heads are vertically stacked with respect to the longitudinal direction of the slits of the ink discharge ports, arranged and driven independently, and further, the recording paper is scanned in synchronization with the driving, whereby a color image can be easily output. .

Further, a plurality of heads are arranged in the sub-scanning direction, a single counter electrode facing the head is provided, and the recording electrodes are vertically run in a direction intersecting all the common electrodes. And an ink supply means for supplying ink of an arbitrary color to each of the plurality of head units independently, and a power supply for supplying a constant voltage between the common electrode and the recording electrode; A recording head having a simple configuration can be obtained by using a configuration having a driving unit that independently and synchronously controls a plurality of arranged common electrodes and a large number of recording electrodes arranged in the main scanning direction and sequentially applies a predetermined voltage. A color image can be output.

Further, according to such a configuration, the ink ejection direction depends only on the position where the common electrodes arranged in the sub-scanning direction intersect with the recording electrodes arranged in the main scanning direction. It does not depend at all on the accuracy, nor does it depend at all on the positional accuracy between the heads since it has only one counter electrode. In other words, it is not necessary to pursue paper feeding accuracy or positional accuracy of each head unit, and it is possible to guarantee the displacement of ink dots in the main scanning direction without fail.Therefore, complicated assembly adjustment work and fine adjustment mechanisms are required. It is unnecessary, and the manufacturing cost and the cost cost can be reduced.

Therefore, it is possible to reduce the size of the apparatus and the cost of the apparatus, and it is possible to easily obtain a high-quality image with less displacement.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a side view (a) and a perspective view (b) showing a first configuration of a head section 111 and a counter electrode section 112 constituting a recording head according to the present invention.

First, the configuration of the head section 111 is shown in FIG.
A description will be given based on (a) and (b). 103 is the head 1
11, a thin-film common electrode 118 is formed on the upper surface of the lower substrate 103 at least near the end face forming the ink discharge port and over the ink discharge width. It is wired to a high voltage power supply 106a via a drive circuit 107a as a means. And the lower substrate 1
03 on the upper substrate 102 via a spacer having a uniform thickness.
Are fixed by means such as adhesion. At this time, the spacer is arranged so as to surround the end surface of the lower substrate 103 where the ink ejection port is formed in a U-shape. By thus configuring the head unit 111 integrally, a gap having a fixed height determined by the spacer thickness is formed between the two substrates as an ink chamber for filling ink, and furthermore, a counter electrode facing the head unit 111 is formed. A single slit-shaped opening 101 (hereinafter, referred to as a slit discharge port) on the side of the portion 112
Is formed.

The upper substrate 103 has an opening 119 for supplying the ink 108 to the ink chamber, and is connected to an ink supply means (not shown) composed of an ink supply tank and a supply tube. . At this time, the ink supply means 119 causes the ink 108 to receive a substantially constant pressure (hereinafter referred to as a static pressure) due to the ink's own weight and the atmospheric pressure, through the ink chamber and through the slit ejection port 10.
1 is supplied. The static pressure applied to the ink 108 balances the surface tension of the ink at the slit discharge port 101, and forms a semi-lunar convex surface, that is, a meniscus, and maintains this state.

Also, as shown in FIG.
The cross section of the portion forming the eleventh slit ejection port 101 is wedge-shaped, and has a structure in which the meniscus is made thinner to concentrate the electric field on the ink. In an electrostatic ink jet recording system having a slit discharge port, it is important to maintain a stable ink meniscus shape in order to stabilize ink discharge. In order to stabilize the meniscus shape of the ink, the shape accuracy of the slit orifice and the contact angle with the ink are large factors, so that the shape accuracy of the portion constituting the slit orifice 101 is naturally high, and the larger the contact angle with the ink, the better. desirable. Therefore, for example, the lower substrate 103 and the upper substrate 102 of the head portion 111 are formed by processing the surface of a substrate made of an insulating material such as glass or ceramics with a silane coupling agent or the like, thereby providing a large contact angle and a stable meniscus. The shape can be secured. This stabilizes the surface state of the ink at the slit discharge port 101,
The direction in which the ink jumps is managed, and the ink ejection amount and speed are stabilized. Further, by managing the curve of the ink meniscus, the concentration efficiency of ink can be increased, and the energy for ink jump can be reduced.

In this embodiment, the lower substrate 103 and the upper substrate 102 of the head portion 111 are formed of an insulating glass substrate having a high surface accuracy, so that the shape of the slit discharge port 101 is accurately formed. Around 101 was subjected to the above surface treatment. In addition, a method was used in which aluminum was vacuum-deposited on the upper surface of the lower substrate 103, and a chemical etching process was performed on the aluminum thin film to form a common electrode.

In the case of the present invention, it is sufficient that the head section 111 has the common electrode 118 for supplying electric charge to the ink, so that the condition of the shape accuracy of the slit discharge port 101 and the contact angle with the ink as described above is satisfied. For example, the lower substrate 10
3 itself may be formed of a metal material. However, since a high voltage is applied to the common electrode 118, in this case, it is desirable to cover the periphery with an insulator in order to avoid the danger of discharge or electrical contact with other members. Although the common electrode 118 is formed using aluminum in the present embodiment, the present invention is not limited to this, and a metal material such as copper, chromium, gold, and nickel may be used. Further, the position at which the common electrode 118 is provided is not limited to the lower substrate 103, and may be, for example, the upper substrate 102, as long as the arrangement is such that the electric charge can be supplied by contacting the ink 108.

Next, the structure of the counter electrode portion 112 will be described with reference to FIG.
It will be described based on. Reference numeral 117 denotes a support for the opposing electrode, which is opposed to the slit discharge port 101 of the head unit 111 and is arranged with a constant minute gap. On the surface thereof, recording electrodes 104 which are subdivided are formed so as to be arranged in the main scanning direction at the same pitch of the recording image pixels over the width substantially equal to the longitudinal direction of the slit ejection port 101 in the head portion 111. The recording electrodes 104 are arranged so that the cross-sectional direction thereof faces the slit discharge ports 101. Further, these recording electrodes 104 are configured to be independently controlled by a driving circuit 107b as a first driving means so that a predetermined constant voltage pulse can be applied to the recording electrodes 104, and to the high voltage power supply 106b via the driving circuit 107b. It is connected.

Since the recording electrodes 104 on the support 117 of the counter electrode portion 112 are arranged at a high density of about 10 to 24 / mm, in this embodiment, the support 117 is an insulator and has high planar accuracy. Using a glass substrate, the recording electrode 104
After patterning aluminum on the substrate by vacuum evaporation,
The aluminum thin film was manufactured by performing a chemical etching process. Further, the surface of the recording electrode 104 is coated with an insulating protective layer in order to prevent discharge or contact between adjacent electrodes or the common electrode 118 in the head portion 111 or a peripheral member.

In the present embodiment, the recording electrode 104 is made of aluminum, but is not limited to the same as the common electrode 118 in the head portion 111.
It goes without saying that a metal material such as copper, chromium, gold and nickel may be used. The head portion 111 of the recording head is 0.5 to 1 m with respect to the counter electrode portion 112.
The recording paper 110 intervenes while being conveyed in the sub-scanning direction by recording paper conveying means (not shown) in the minute gap. The flying ink 109 discharged to the electrode section 112 side adheres to the printing surface of the recording paper 110. As a recording paper conveying means, a conveyance mechanism such as a friction feed system using a roller pair is used, and the recording paper is intermittently or continuously intermittently or continuously in a sub-scanning direction in synchronization with driving of a recording electrode in a recording head. It is transported by a predetermined amount.

Since it is difficult to insert the recording paper 110 into the minute gap when the recording paper 110 is conveyed to the recording head, for example, the head unit 111 or the counter electrode 112 is provided in the conveyance mechanism. It is desirable to provide a mechanism for retracting the paper in the direction in which the paper spreads, setting the paper with the paper intervening in the gap, and then returning the paper to the specified minute gap.

Next, the recording electrode 104 and the common electrode 118
The connection of the wiring will be described. The high voltage power supply 1 is connected to the common electrode 118 in the head unit 111 via the drive circuit 107a.
06a is connected to the negative electrode side. Also, the counter electrode section 11
A drive circuit 107 is provided on the divided recording electrode 104 side in
The positive electrode side of the high-voltage power supply 106b is connected via b.

In addition to the connection method, when the number of recording heads is one as in the recording head configuration shown in this embodiment, ink can be ejected even if the common electrode 118 side is grounded. However, the electric field applied between the electrodes must be ensured by setting the potential applied to the recording electrode 104 higher than the set value or by narrowing the minute gap between the electrodes, so as to secure the electric field strength between the electrodes necessary for discharging ink. No.

Next, an example of a method of driving the recording head to which the electrodes are connected as described above will be described with reference to a block diagram shown in FIG. First, a parallel signal output from an external device 601 such as a PC terminal is input to an interface 602 which is an entrance / exit as a recording device, and a control signal including a parallel recording image signal, a signal for controlling the device, and the like from the interface 602. Is output.

The parallel recording image signal output from the interface 603 is output to a signal processing circuit 603.
To enter. The control signal output via one of the interfaces 602 is input to a control circuit 604, and the signal processing circuit 603 and the counter electrode driver 60
5 and each of the head driver 608 is converted into a control signal for performing a synchronized operation with a certain timing.

The signal processing circuit 603 converts the parallel recording image signal output from the interface 602 into a serial binary signal while receiving the control signal from the control circuit 604, and converts the signal into a binary signal.
Enter 05. At this time, the counter electrode driver 6
A shift register type latch is built in the print unit 05, and a print image signal for one print line extending in the longitudinal direction of the slit of the head unit 111 is set based on the input of the shift register. A control signal for driving one recording line is output from 604. By this driving operation, the counter electrode unit driver 608
, A constant voltage pulse of positive polarity for one recording line based on the recording image signal is selectively supplied to each recording electrode 606.

A similar control signal is input from the control circuit 604 to the head driver 608 in synchronization with the driving operation of the recording electrode 606, and the polarity is opposite to the voltage applied to the recording electrode 606 (here, A negative voltage pulse is supplied to the common electrode 607 for driving. At this time, the first potential applied to the common electrode 607 in the head portion 611 has a negative voltage polarity, the absolute value of the voltage ranges from 1.5 to 2 kV, and the second potential applied to the recording electrode 606 in the counter electrode portion 612. Has a positive voltage polarity and a voltage absolute value of 300 to 750.
V range. Further, the pulse application time was set to 1 ms in synchronization with each other, and driving was performed with an application cycle of 2 to 4 ms.

The above is the operation for one line of recording. By repeating this operation sequentially and conveying the recording paper by a predetermined amount in the sub-scanning direction, a desired image is output on the recording paper. In this embodiment, a method of simultaneously driving one recording line to increase the printing speed has been described. In particular, in an electrostatic inkjet recording method having a single slit opening, adjacent recording electrodes are used. When a voltage is applied to the ink at the same time, the ink is electrically and physically connected in the slit, causing a voltage drop between adjacent recording electrodes and the influence of stress in the ink due to the surface tension and viscosity of the ink. In some cases, problems such as ejection failure or deviation of the landing position on the recording paper may occur. In order to prevent these phenomena, it is easy to avoid it by a method of driving the recording electrodes in a time-division manner by delaying the recording electrodes in a plurality of recording electrodes for one recording line.

Next, the conditions of the ink used in the present invention are described below. Factors that greatly contribute to ink jump as ink physical properties include surface tension, viscosity, and volume resistance. The relationship between the surface tension and the maximum interval of the ink jumped to the counter electrode (hereinafter referred to as the maximum recording interval) is as follows.
When the surface tension is in the range of 20 to 50 dyn / cm, the surface tension increases as the surface tension decreases. Therefore, as the surface tension is smaller, the resistance in the ink ejection process is smaller, and the ink can be ejected even with a weak electric field, so that the maximum recording interval can be increased. The surface tension of water-based ink is generally higher than that of pure water at 72.8 dyn / cm (20 ° C.), but the organic solvent is from 20 dyn / cm to 35 dyn / cm.
Therefore, an ink in which a dye is dissolved in an organic solvent can be used as the ink of the present invention. The maximum recording interval can also be increased by dissolving an anionic surfactant, a cationic surfactant, a nonionic surfactant, or the like as a surfactant in the ink to improve the surface tension.

The viscosity of the ink solvent can be selected from a wide range. However, since the solvent having a low viscosity has high volatility, the preservability of the ink is deteriorated. Select a range of solvents. Regarding the relationship between the viscosity and the maximum recording interval, when the surface tension and the volume resistance value are considered to be constant, the maximum recording interval increases as the viscosity decreases. Therefore, when the viscosity is low as in the case of the surface tension, the resistance in the ink ejection process is reduced, and the maximum recording interval can be increased.

In order to discharge the ink, it is necessary to charge the ink from the common electrode in the head portion. Therefore, it is desirable that the volume resistance is high, and the ink volume resistance in the present invention is set to an appropriate range. Is 1 × 10
⁶ Ω · cm or more. In the present embodiment, ink having a volume resistivity of 1 × 10 ⁷ to 1 × 10 ⁹ Ω · cm is used.

The above-mentioned setting of the ink characteristic values is based on the voltage value supplied between the common electrode and the recording electrode on the counter electrode, the distance to the counter electrode, the slit width of the slit discharge port, etc. Because the structure, and the shape and structure of the electrode itself depend on whether or not ink jumps,
It goes without saying that the characteristic ranges such as the optimum surface tension, viscosity and volume resistance value are not necessarily limited to the above values.

Next, the recording operation of the apparatus will be described with reference to FIG. In this embodiment, the recording head is a recording paper 11
A description will be given assuming that the line head has a slit discharge port 101 substantially equal to zero. When a printing command is issued from the apparatus, first, as an initial operation, a cleaning operation of the slit discharge unit 101 in the head unit 111 is performed by a discharge port cleaning mechanism (not shown), and the recording head is brought into a state where ink can be discharged. When the cleaning operation is completed, the recording paper 110 is transported using a paper supply mechanism such as an automatic sheet feeder and a roller pair (not shown).
By intervening in a minute gap formed by the head unit 111 and the counter electrode unit 112, the position of the recording start portion is determined by controlling the transport mechanism using a position detecting means such as a paper edge sensor.

When the initial operation is completed, the drive for one line of printing is performed as shown in the drive operation of the print head. That is, a constant voltage pulse of negative polarity is applied to the common electrode 104 on the head portion 111, whereby negative charges are charged in the ink 108, and negative charges are generated on the entire meniscus portion of the slit discharge port 101. When a positive constant voltage pulse is applied to the portion of the recording electrode 104 to be printed almost simultaneously with this operation, the common electrode 1
A large potential difference occurs only between the recording electrode 18 and the recording electrode 104, and an intense electric field is locally generated. At this time, the negatively charged ink 108 at the slit discharge port 101 receives a Coulomb force due to the generation of the electric field, and the ink 109 is attracted to the recording electrode 104 to which the voltage is applied, jumps, and the intermediate recording occurs. Landed on paper 110,
The ink 109 permeates the recording paper 110. At this time, the electric field generated from the common electrode 118 to the recording electrode 104 converges on the recording electrode 104 side, so that the ink lands accurately at a desired position.

After the recording for one line is completed, the recording paper 110 is conveyed in the sub-scanning direction by an amount determined to a predetermined resolution in the direction of the arrow, and the same recording operation is performed for the second and subsequent lines. repeat. As described above, an image can be output on the recording paper 110 within the range of the width of the recording head and the scanning amount of the recording paper 110. (Embodiment 2) FIG. 2 is a side view (a) and a perspective view (b) showing a second configuration of a head portion and a counter electrode portion constituting a recording head in the present invention.

First, the configuration of the head section 211 is shown in FIG.
A description will be given based on (a) and (b). 203 is the head 2
11, a thin-film common electrode 218 is formed over a wide area on the upper surface of the lower substrate 203, and the high-voltage power supply 20 is driven through a driving circuit 207a as a second driving means.
6a. An upper substrate 202 is fixed on the lower substrate 203 via a spacer having a uniform thickness by means such as adhesion. At this time, the spacer is the lower substrate 2
At 03, an end face forming an ink discharge port is arranged so as to surround the U-shape. By thus integrally configuring the head portion 211, a gap having a fixed height determined by the spacer thickness is formed between the two substrates as an ink chamber for filling ink.
The slit discharge port 20 is provided on the side of
1 will be formed. The upper substrate 203 has an opening 21 for supplying ink 208 to the ink chamber.
9, an ink supply means (not shown) composed of an ink supply tank and a supply tube is connected. At this time, the ink 2
08 is supplied to the slit discharge port 201 through the ink chamber while receiving a static pressure. The static pressure applied to the ink 208 is balanced with the surface tension of the ink at the slit discharge port 201, and forms a semi-lunar convex surface, that is, a meniscus, and maintains this state.

Further, as shown in FIG.
The cross section of the portion constituting the eleventh slit discharge port 201 is wedge-shaped, and has a structure in which the meniscus is made thinner to concentrate the electric field on the ink. Next, the counter electrode unit 2
12 will be described with reference to FIG. Reference numeral 217 denotes a support for the counter electrode, which is opposed to the slit discharge port 201 of the head unit 211 and is arranged with a certain minute gap. On the surface thereof, the recording electrode 204 which is subdivided is provided with the slit ejection port 20 in the head portion 211.
1 over the width substantially equal to the longitudinal direction, and are arranged in the main scanning direction at the same pitch of the recording image pixels, and so that the surface of the recording electrode 204 faces the slit discharge port 201 at a right angle. Is formed. The recording electrodes 204 are independently controlled by a driving circuit 107b as a first driving means so that a predetermined constant voltage pulse can be selectively applied.
Is connected to the high voltage power supply 206b.

In an electrostatic ink jet recording system having a slit discharge port, charged ink is discharged by receiving a Coulomb force by an electric field generated in a minute gap formed between an electrode in a head portion and an electrode in a counter electrode portion. I do. Therefore, in order to perform stable printing particularly in a line head, it is important that the electric field applied to the minute gap is uniform no matter where the voltage is applied to the recording electrode.

Since the electric field strength E when a voltage is applied between the two electrodes arranged to form a minute gap to provide a potential difference is inversely proportional to the distance between the electrodes, the distance between the electrodes is uniform. Therefore, by making the distance between the electrodes in the line direction uniform, a uniform electric field can be obtained in the above direction. In the first embodiment, the slit discharge port and the recording electrode are arranged so as to abut each other in cross section. Therefore, as described above, in order to apply a uniform electric field between the common electrode and the recording electrode, the distance between the common electrode and the recording electrode in the gap direction is required. In addition, the positioning must be performed also in the main scanning direction of the recording electrode facing the slit discharge port in the sectional direction.

However, by disposing the counter electrode portion 212 having such a shape as shown in the second embodiment, only the distance in the gap direction between the common electrode and the recording electrode needs to be regulated. Can be incorporated into the device. FIG. 3 shows another example of the shape of the counter electrode portion.
(A) and (b) are also conceivable.

FIG. 3 (a) shows an electrode cover 320, which is an insulating member, is molded and integrated on the recording electrode 304 side on a support 317 on which the recording electrode 304 is formed as in the first embodiment. . With such a configuration, the insulating property between the adjacent electrodes of the recording electrode 304 is sufficient and the danger such as discharge can be suppressed, and the voltage value of the constant voltage pulse applied to the recording electrode 304 can be increased. . In other words, since the electric field at the portion where the ink is ejected can be increased, the Coulomb force applied to the ink can be increased, and stable printing can be performed.

FIG. 3B shows a structure in which a recording electrode pattern is formed on a flexible substrate 321 and attached to a support 317 to form a counter electrode portion 312. The counter electrode portion 312 can be manufactured at low cost. It can be easily replaced at the time of maintenance. In addition, both of the above can be used as a guide for the recording paper by making the leading end a curved surface. The paper is conveyed while maintaining a small gap between the paper and the paper, so that the paper can be easily and stably conveyed in the small gap.

(Embodiment 3) FIGS. 5A and 5B are a side view and a perspective view, respectively, showing a second configuration of a recording head for simultaneously recording a plurality of colors using the recording head of the present invention. is there. Four head units 511 in the print head described in the first or second embodiment are arranged in a row in the sub-scanning direction so as to be stacked, and the head units 511Y and 511 of each print head are arranged.
M, 511C, and 511Bk are supplied with color inks in the order of yellow (hereinafter, Y), magenta (hereinafter, M), cyan (hereinafter, C), and black (hereinafter, Bk) in the paper transport direction. The counter electrode portion 512 is the same as that of the second embodiment.
It has the same shape as. However, one counter electrode portion 512 is provided for each of the four head portions 511 of each color, and the recording electrodes 504 in the counter electrode portion 512 are vertically arranged in the sub-scanning direction and arranged in the main scanning direction. The common electrodes 518Y, 518M, 518M, 518M in the range opposed to all of the ink ejection ports 501Y, 501M, 501C, 501Bk of the unit 511.
518C, 518Bk are configured to intersect perpendicularly.

The surface of the recording electrode 504 and the head 51
1 are also provided for the minute gaps provided in the slit discharge portions 501 in all the slit discharge ports 501Y, M,
Each head section 511 and the counter electrode section 512 are provided in a state guaranteed for C and Bk. The head 51
A driving circuit 507a as a second driving unit on one side is provided independently for each color, and only one driving circuit 506b as a first driving unit on the counter electrode unit 512 side is provided in common.

By arranging the head portion 511 and the counter electrode portion 512 in the above-described configuration, the four common electrodes 518Y, 518M, 518 provided in each head portion 511 are provided.
C and 518Bk are sequentially arranged in the sub-scanning direction, and the recording electrodes 504 provided in the opposing electrode portion 512 by dividing the number of recording pixels in the main scanning direction are sequentially arranged in the main scanning direction. They intersect and are formed in a matrix.

Next, an example of a method of driving the electrodes arranged in a matrix as described above (hereinafter referred to as matrix driving) will be described with reference to the block diagram shown in FIG. First PC
A parallel signal output from an external device 801 such as a terminal is transmitted to an interface 80 serving as an entrance as a recording device.
2, a control signal including a parallel red, green, and blue (hereinafter, R, G, and B) recording image signal and a signal for controlling the apparatus is output from the interface 802.

The parallel R, G, and B recording image signals output from the interface 803 are input to a signal processing circuit 803. One of the interfaces 8
The control signal output via the control circuit 02 is input to the control circuit 804, and the signal processing circuit 803, the counter electrode driver 812 and the head drivers 808Y and 808 are provided.
M, 808C, and 808Bk are converted into control signals for operating in synchronization with timing.

The signal processing circuit 803 receives the control signal from the control circuit 804 while receiving the parallel R, G, B output from the interface 802.
The recorded image signal is converted to Y · M by a parallel / serial conversion circuit and a color conversion circuit built in the signal processing circuit 803.
Convert to a C.Bk serial binary signal, and input the recorded image signal to the counter electrode driver 805 corresponding to each color.

At this time, the Y, M, C, and Bk recording image signals are controlled so as to receive the control signal from the control circuit 804, sequentially scan the recording image signals of each color, and input the signals to the counter electrode driver 805. ing. Therefore first Y
Is input to the opposing electrode driver 805, and the opposing electrode driver 805 selectively turns on / off the recording electrode 806 in accordance with the recording image signal for one recording line.
FF is controlled, and a voltage pulse is simultaneously supplied to the recording electrode 806 in synchronization with the timing of the control signal.

A similar control signal is input from the control circuit 804 to the head driver 808Y in synchronization with the driving operation of the recording electrode 806, and the head driver 808Y applies a voltage applied to the recording electrode 806. A constant voltage pulse having a polarity opposite to that of the recording signal
6 and is supplied to the common electrode 807Y in synchronization with the driving cycle.

At this time, the voltage supply on the recording electrode side and the voltage supply on the common electrode side are performed almost simultaneously. After the same driving as described above is repeated with a slight delay in time division in the order of M, C, and Bk, the amount determined by the predetermined resolution in the sub-scanning direction is conveyed in the direction of the arrow, and the next operation is performed again. The same recording operation is repeated for the input of the recording image signal. As described above, a color image can be output on the recording paper within the range of the arrangement width of the recording electrode groups in the main scanning direction and the scanning amount of the recording paper in the sub-scanning direction.

Since the slit discharge ports 501 of the plurality of recording heads are sequentially arranged at intervals in the sub-scanning direction (hereinafter referred to as the distance between recording heads), the recording heads 511 of each color use one line for recording each color. Cannot be simultaneously recorded on recording paper. Therefore, the recording image signal of each color from the signal processing circuit 803 is delayed by the delay circuit 8 to apply a delay corresponding to the distance between the recording heads.
After a predetermined time via the counter electrode driver 8
Input to the counter electrode unit driver 8 or a memory provided with image data corresponding to the distance between the recording heads in advance.
05 must be entered.

FIG. 7 is a driving chart showing a specific example of the matrix driving method. First, a voltage pulse Vs for Y printing is selectively applied to the recording electrode 704 in the counter electrode portion 712 on the recording electrode 704 side by a recording image signal based on the image data for Y. In FIG. 7, the voltage pulse Vs is applied only to the recording electrode positions B and J in order to attract ink to the recording electrode positions B and J.

At the same time or at a slightly earlier timing, a voltage pulse -Vc having a polarity opposite to the voltage applied to the recording electrode 704 is applied to the common electrode 718Y in the Y head portion 711Y. At this time, the recording electrode position AC
The potential difference between the electrodes in DEFGHI is only Vc, and the ink is not ejected because the electric field strength due to this potential difference does not exceed the Coulomb force threshold for ejecting ink. The potential difference between the electrodes at the recording electrode positions B and J is Vc + Vs, and the electric field strength due to this potential difference is set to exceed the threshold value of the Coulomb force for ejecting the ink. , J, and two ink dots are formed on the recording paper 710 interposed between the two electrodes while maintaining the above positions.

Next, after a short time Δt with respect to the driving, the recording electrode 704 in the counter electrode portion 712 is supplied to the recording electrode 704 side by a recording image signal based on the image data for M.
, A voltage pulse Vs is applied only to the recording electrode positions D and J. Further, the driving of the head section 711 shifts to the common electrode 718M in the head section M, and the same driving as described above is performed to apply the voltage pulse -Vc, thereby forming ink dots at the recording electrode positions D and J on the recording paper 710. You.

Next, after a short time Δt with respect to the driving, the recording electrode 704 in the counter electrode portion 712 is supplied to the recording electrode 704 by a recording image signal based on the image data for C.
, A voltage pulse Vs is applied only to the recording electrode positions F and J. Further, the driving of the head section 711 shifts to the common electrode 718C in the head section C, and the same driving as described above is performed to apply the voltage pulse −Vc, thereby forming ink dots at the recording electrode positions F and J on the recording paper 710. You.

Next, after a short time Δt with respect to the driving, a recording image signal based on the image data for Bk is applied to the recording electrode 704 side on the recording electrode 704 side.
4, a voltage pulse Vs is applied only to the recording electrode position H. The driving of the head section 711 is shifted to the common electrode 718Bk in the head section Bk, and the same driving as described above is performed to apply the voltage pulse -Vc, thereby forming an ink dot at the recording electrode position H on the recording paper 710.

By the above operation, on the recording paper 710, the Y color ink dot at the B position, the M color ink dot at the D position, the C color ink dot at the F position, the Bk ink dot at the H position, and the J position The ink dots in which the YMC colors are sequentially overlapped are formed on a straight line in the main scanning direction. After these operations are completed, the recording paper 710 is driven in the sub-scanning direction by a predetermined amount, and the above operation is repeated according to the image data, whereby a color image output can be obtained.

The recording head is constructed by intersecting the common electrode and the recording electrode as in this embodiment, and the matrix drive as shown in this embodiment is carried out, so that a very large number of recording electrodes can be formed. Since only one counter electrode portion 512 and one drive driver 507b forming the pattern are required, it is possible to reduce the size and cost of the color output device.

The ink is supplied with electric charge by the common electrode in the head portion, and receives a Coulomb force by an electric field selectively generated by driving the recording electrode on the opposite electrode portion, and is ejected to finely correspond to the recording pixel. It lands on the divided recording electrodes. At this time, since the counter electrode portion itself is fixed and the counter electrode portion is formed by one piece, the ejection position is set to the recording electrode of the counter electrode portion regardless of the mounting position of the head portion and the feeding accuracy of the recording paper. It is determined by the position where the common electrode crosses.

Accordingly, the displacement of the ink dots in the main scanning direction can be reliably assured without the necessity of the alignment between the respective head portions. Therefore, a complicated assembly adjustment operation and a fine adjustment mechanism are not required. Manufacturing costs and cost costs can be reduced. Therefore, the size of the apparatus can be reduced and the cost of the apparatus can be reduced, and a high-quality image with less displacement can be easily obtained.

FIG. 4 shows another example of the shape of the counter electrode portion applicable to the recording head shown in the second embodiment and FIG.
(A) and (b) are conceivable. FIG.
Reference numeral 412 in (a) and (b) denotes a flexible substrate in which recording electrodes 404 are patterned on a base film 421 made of an insulating material such as polyimide.
It is fixed on the top by means such as adhesion. At this time, the supporter 417 has a protrusion in the main scanning direction so as to protrude in a wedge shape with respect to the ink ejection port of the head portion. The flexible substrate 412 is fixed along the protrusion, and the flexible substrate 412 is fixed. The upper recording electrode 404 is directed so as to protrude from the ink ejection port of the head unit. As the shape of the projection, a wedge shape as shown in FIG.
Even with the rectangular convex shape shown in (b), the following effects can be sufficiently obtained.

By adopting such a configuration, the electric field generated between the common electrode and the recording electrode 404 in the head portion is easily concentrated, and the generation of unnecessary electric fields around the head is reduced, so that stable ejection is achieved. Easy to obtain characteristics. Further, if the recording electrode 404 is formed of a flexible substrate having a high degree of freedom in molding as shown in the drawing, the recording electrode 404 can be applied to the counter electrode portion 512 side of the recording head as shown in FIG.

Next, the recording operation of the apparatus will be described with reference to FIG. In this embodiment, the recording head is a recording paper 51.
A description will be given assuming that the line head has a slit discharge port 501 substantially equal to zero. When a printing command is issued from the apparatus, first, as an initial operation, the head units 511Y, 511M, 511C, and 51 are driven by a discharge port cleaning mechanism (not shown).
The cleaning operation of the slit discharge unit 501 within 1Bk is performed, and the recording head is brought into a state where ink can be discharged from the head unit of each color. When the cleaning operation is completed, the recording paper 510 is transported using a paper supply mechanism such as an automatic sheet feeder and a roller pair (not shown).
First, a charge removing brush 551 serving as a charge removing means for removing a charge previously charged on the recording paper 510
And is conveyed to the recording head side via. Static elimination brush 551
Is made of a conductive brush having a width of the recording paper and is electrically grounded. The brush portion is brought into contact with the recording surface of the recording paper 510 to remove the electric charge of the recording paper 510.

The surface of the recording paper 510 is often charged due to friction between the recording papers when the recording paper is taken out of the bundle of recording papers by the automatic sheet feeder and friction between the recording papers 510 and the rollers at the time of conveyance, and the distribution is uneven. It is. In such a state, when driving the recording head, an unnecessary electric field is generated between the recording head and the common electrode, and the ink ejection becomes unstable.
It is desirable to provide static elimination means in this way. In the present embodiment, the static elimination brush is used. However, as another method, there is a method in which a grounded conductive roller or blade is pressed against the recording paper 510 or a corotron device is used.

Then, the recording paper 510 is connected to the discharging brush 55
After passing through the recording paper 510, the recording paper 510 intervenes in a minute gap formed by the head unit 511 and the counter electrode unit 512, and controls the transport mechanism using position detecting means (not shown) such as a paper edge sensor. To determine the position of the recording start portion. Then, when the initial operation is completed, the recording paper 510 performs the driving shown in the driving operation of the recording head,
A plurality of color images are output on recording paper 510.

In the present embodiment, the four color inks of Y, M, C, and Bk are used as the plurality of color inks. However, the present invention is not particularly limited to this. By providing a plurality of ink colors, an arbitrary number of ink colors can be printed. For example, by providing each head unit and ink supply means using two types of inks of different shades for the Y, M, and C colors shown in this embodiment, color gradation can be easily obtained, and higher High quality color image output can be obtained.

[0075]

The present invention is embodied in the form described above and has the following effects. (1) In the recording head, by arranging the head portion as a common electrode and disposing the divided recording electrodes on the counter electrode side, the structure of the head portion can be simplified, and manufacturing restrictions can be reduced, thereby improving the yield. Therefore, it is possible to improve the maintainability of the recording head and reduce the manufacturing cost. Further, since the structure of the head portion is simply configured, a long line head can be easily manufactured. By scanning the recording paper in a plane with this line head, the recording speed is greatly reduced, and high-speed printing can be performed.

(2) Since the divided recording electrode side is disposed on the counter electrode portion side, it does not come into contact with the ink, and the recording electrode surface can be subjected to insulation treatment. Thus, deterioration of the electrodes and discharge between adjacent electrodes can be prevented, and the life of the recording head can be extended. Furthermore, since the recording electrodes do not come into contact with the ink and the recording electrodes can be covered with an insulating material, the insulating property between the adjacent electrodes is sufficiently high, and the recording electrodes that eject ink and the recording electrodes that do not eject ink have the same properties. Since the potential difference can be made large, the selectivity of the ink ejection position can be stabilized.

(3) Since the electric field is concentrated on the recording electrode on the counter electrode, which is the end point on the ink ejection direction side, the ink landing position accuracy is improved, and the quality of the output image can be improved. (4) A color image output can be easily obtained by vertically stacking the recording heads and driving them independently.

(5) In the recording head, a plurality of heads are vertically overlapped, one counter electrode is arranged for the plurality of heads, and both electrodes are driven in a matrix to output a color image. It becomes possible. Therefore, the configuration of the apparatus is greatly simplified, and the size and the cost of the apparatus as a color image output apparatus can be reduced. (6) An ink of an arbitrary color is supplied to the plurality of heads, and one counter electrode is provided so as to face the heads, and a recording electrode on the counter electrode is common to the plurality of heads. A color image can be output by driving both electrodes in a matrix with the electrodes crossing each other, and the displacement of the ink dots in the main scanning direction can be reliably ensured without the need for alignment between the heads. This eliminates the need for complicated assembly and adjustment operations and fine adjustment mechanisms, and can reduce manufacturing costs and cost costs.

Therefore, it is possible to reduce the size of the device and reduce the cost of the device, and it is possible to easily obtain a high-quality image with less displacement. (7) By providing a static eliminator for removing the charged charges on the recording medium upstream of the recording head, the electric field between the common electrode and the recording electrode is not disturbed, and the occurrence of defective dots is prevented and stable image output is achieved. It can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first configuration of a recording head according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a second configuration of a recording head according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a configuration of another example of the counter electrode unit according to the second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of another example of the counter electrode unit according to the third embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a configuration of a recording head that outputs a color image using the recording head of the second configuration of the present invention.

FIG. 6 is a block diagram showing a driving method when the recording head according to the first or second embodiment of the present invention is used.

FIG. 7 is a driving timing chart showing a driving method when a recording head according to Embodiment 3 of the present invention is used.

FIG. 8 is a block diagram showing a driving method when a recording head according to Embodiment 3 of the present invention is used.

FIG. 9 is an explanatory diagram showing a configuration of a recording head according to a conventional slit jet method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Slit discharge port 104 Recording electrode 106 Power supply 107 Drive circuit 108 Ink 109 Flying ink 110 Recording paper 111 Head part 112 Counter electrode part 118 Common electrode

Continuation of the front page (72) Inventor Hiroyuki Muramatsu 1-8 Nakase, Mihama-ku, Chiba-shi, Chiba Prefecture SII IRD Center (56) References JP-A-62-23963 (JP, A) 58-49264 (JP, A) JP-A-63-59539 (JP, A) JP-A-9-239987 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2 / 06

Claims (2)

(57) [Claims] 1. An electrostatic ink jet recording head which applies an electrostatic force to ink to discharge ink from a discharge port in a fixed direction, comprising: an ink discharge port having a single slit-shaped opening with no break for each dot ; A head portion comprising a common electrode located in the vicinity of the ink ejection port and located in the longitudinal direction of the ink ejection port, facing the ink ejection port of the head portion with a minute gap. The counter electrode portion is composed of a large number of recording electrodes arranged and divided in accordance with recording image pixels .
And the head section is moved in the short direction of the ink discharge port (hereinafter referred to as the sub-scanning direction).
And a single counter electrode portion facing the plurality of head portions is provided.
The recording electrode is connected to the inside of the plurality of heads.
Run vertically in the direction that intersects all common electrodes.
Ink ejection ports in the longitudinal direction (hereinafter referred to as the main scanning direction).
Position, the intersection of the recording electrode and the common electrode
In simple ink ejecting position is defined, any color in the each independently to the plurality of head
An ink supply means for supplying a click, the common electrode and the power supply for supplying a constant voltage between the recording electrodes, the main scanning direction is controlled in accordance with the recording image signal corresponding to the voltage from the power supply to the desired color selectively a first driving means for applying a voltage, the first synchronization control to the desired color to the operation of the drive means relative arrayed recording electrodes in
Are arranged in the sub-scanning direction in the head section to which
A voltage having a polarity opposite to that of the recording electrode is applied to the common electrode.
And a second driving unit for applying the voltage, wherein the driving by the first driving unit and the second driving unit is performed.
A recording head for sequentially scanning a work in a time-division manner for each color . 2. An ink jet printer according to claim 1, further comprising:
The recording medium is supplied to the minute gap, and the recording head
Scans the recording medium in the sub-scanning direction in synchronization with the drive of the
Having a recording medium transporting means for inspecting the
An ink droplet corresponding to the recording image signal is applied to an arbitrary position on the medium.
2. An image recording apparatus using a recording head according to claim 1, wherein said recording head is attached and penetrated .