JP2885994B2 - 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 ink jet recording apparatus using a recording head for discharging ink droplets.

[0002]

2. Description of the Related Art A conventional ink jet recording apparatus comprises a recording head for discharging ink droplets by means of energy from a discharging energy generating means, and means for relatively moving the recording head and a recording medium. And the recording medium are arranged to face each other as shown in FIG. 7 to form an image.

That is, in FIG. 7, 1 is a recording head, 42 is pressure generating means, and 7 is a recording medium. The ink 43 in the recording head 1 is extruded by the pressure of the pressure generating means 42, and the recording medium 7 is extruded. An image is formed by depositing ink droplets on the recording medium and conveying the recording medium 7 in the direction of arrow A by a recording medium conveying means (not shown).

[0004]

However, in the above conventional example, when the movement of the ink droplet is affected by the electric force due to the electric field between the recording medium 7 and the recording head 1,
In some cases, the ink droplets did not land at an intended position on the recording medium 7 and caused image disorder.

An object of the present invention is to provide an ink jet recording apparatus which can form an accurate image without image disturbance while avoiding the influence of an electric field existing between a recording head and a recording medium. .

[0006]

According to the present invention, there is provided an ink jet recording apparatus, comprising: an ink jet recording head for discharging ink; a means for relatively moving the recording head and a recording medium; and a surface for measuring a surface potential of the recording medium. Potential measuring means, adjusting means capable of adjusting a potential difference between the recording head and the recording medium, and control means for controlling the adjusting means in accordance with the value of the surface potential measured by the surface potential measuring means. It is characterized by comprising.

[0007]

The ink jet recording apparatus of the present invention measures the surface potential of a recording medium and adjusts the potential difference between the recording head and the recording medium in accordance with the measurement result, so that the distance between the recording head and the recording medium is reduced. The electric field strength of
The disturbance of the image caused by the electric field is prevented.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic side view showing a first embodiment of an ink jet recording apparatus according to the present invention.

In FIG. 1, 1Bk, 1y, 1m, 1c
Are recording heads corresponding to black, yellow, magenta, and cyan ink colors, respectively. Each recording head is
A heating resistor is used as a built-in ejection energy generator, and bubbles are generated in the ink by using thermal energy generated when the heating resistor is energized, and the ink droplets are ejected from the ejection ports by the bubbles. And are fixed to the block 2 respectively. Further, each of the recording heads is arranged in a row at a density of 400 dpi, and forms 4736 ejection ports.

Reference numeral 3 denotes a capping unit which caps the lower side of the block 2 which has been raised to a position A shown by a dashed line in FIG. Further, the capping unit 3 serves as a waste ink tray at the time of the circulation recovery, and receives the waste ink which is fed from a recovery pump and an ink supply system (not shown) and is pushed out from the discharge port at the time of the circulation recovery. The waste ink received by the capping unit 3 is guided to a waste ink tank (not shown).

Reference numeral 4 denotes recording heads 1Bk, 1y, 1m, and 1c.
Endless charging and suction belts 5 are provided opposite to each other at a predetermined interval to convey a recording sheet, and 5 is a back platen provided to face each recording head via the charging and suction belt 4. The charge absorption belt 4 is charged by a charging roller 31 described later in detail.

Reference numeral 6 denotes a paper feed cassette which accommodates recording sheets 7 such as plain paper and is detachably mounted on the apparatus main body. Reference numeral 8 denotes a pickup roller which feeds out and feeds only one uppermost recording sheet 7. . Reference numeral 9 denotes a transport roller that transports the recording sheet 7 sent from the pickup roller 8 to a transport path 10, and reference numeral 11 denotes a transport roller disposed on the exit side of the transport path 10.

Reference numerals 13 and 14 denote heaters and fans for drying and fixing the ink droplets adhered to the recording sheet 7 for recording by hot air, and 15 a discharge roller for discharging the fixed recording sheet 7 out of the apparatus. Reference numeral 16 denotes a tray for sequentially storing the discharged recording sheets 7.

Numeral 32 denotes a recording sheet 7 on the charge absorbing belt 4.
A charge-injecting brush-like electrode 33 is in contact with a surface potential measuring means for measuring the surface potential of the recording sheet 7 on the charge absorbing belt 4. In FIG. 3, reference numeral 34 denotes the charging roller 3.
1 is a power supply for applying a predetermined voltage, 35 is an electrode provided on the recording head 1 and grounded, 36 is a variable power supply for applying an adjustable voltage to the brush-like electrode 32, and 37 is a recording sheet measured by the measuring means. 7 based on the surface potential of the variable power supply 3
6 is control means for controlling the output voltage. In FIG. 3, reference numeral 42 denotes an electrothermal converter provided in the recording head 1;
43 is an ink liquid.

Next, the operation of the embodiment having the above configuration will be described.

First, when a recording start operation is performed, a recording sheet 7 of a designated size is sent out of the sheet cassette 6 by the pickup roller 8. The fed recording sheet 7 is placed on the charging suction belt 4 by the transport rollers 9 and 11. The belt 4 rotates while being charged by the charging roller 31 so that its surface potential becomes a predetermined voltage (for example, +2 kV), and has a planar shape above the back platen 5. Then, as described later, the surface potential on the recording sheet 7 is measured by the surface potential measuring means 33, and the control means 37 controls the voltage applied from the variable power supply 36 to the brush-like electrode 32 according to the measured value. . Further, in conjunction with the leading end of the recording sheet 7 arriving at the lower part of each of the heads 1c, 1m, 1y, and 1Bk, the energy generator of each recording head is changed according to image data via a drive circuit (not shown). Drive. By this driving, ink droplets corresponding to the image information are ejected from the ejection openings of the respective recording heads to the surface of the recording sheet 7 to perform recording.

If the recording sheet 7 has poor hygroscopicity, the ink droplets adhering to the surface do not dry, and the ink droplets may be rubbed to cause printing stains. To fix the ink droplets. The recording sheet 7 on which the fixing of the ink droplets has been completed is discharged to the tray 16 by the discharge roller 15.

As described above, a color image is formed on the recording sheet 7 by applying a recording signal corresponding to each of the recording heads corresponding to the cyan, magenta, yellow, and black inks.

Next, the principle of ejection of the ink jet recording head used in the apparatus of this embodiment will be described.

A recording head applied to an ink jet recording apparatus generally has a fine liquid ejection port (orifice),
The apparatus includes a liquid flow path communicating with the discharge port, an energy action part provided in a part of the liquid flow path, and an energy generating means for generating ink droplet forming energy to act on the liquid in the action part. .

As an energy generating means for generating such energy, a recording method using an electromechanical transducer such as a piezo element or the like, or an electromagnetic wave such as a laser or the like is irradiated and absorbed by a liquid there. And a recording method using an energy generating means for discharging and flying ink droplets by the action of the heat generation, or a recording method using an energy generating means for heating and discharging the ink liquid by an electrothermal converter. .

Among them, a recording head used in an ink jet recording method for discharging an ink liquid by thermal energy has a high liquid discharge port (orifice) for discharging a recording ink liquid to form a flying ink droplet. Since they can be arranged at a high density, it is possible to record at a high resolution. In addition, a recording head using an electrothermal transducer as an energy generating means can be easily made compact as a whole as a recording head, and has recently achieved remarkable advances in technology and reliability in the semiconductor field, such as IC technology and microelectronics. The advantages of processing technology can be fully utilized, and it is easy to make it longer and more planar (two-dimensional), so it is easy to use multiple discharge ports / high-density mounting, and mass productivity. It is possible to provide an ink jet recording head which is well manufactured and inexpensive.

In general, an ink jet recording head manufactured through a semiconductor manufacturing process using an electrothermal converter as an energy generating means is provided with a liquid flow path corresponding to each discharge port, An electrothermal converter is provided for each liquid flow path, and thermal energy is applied to the liquid filling each liquid flow path by each electrothermal converter, and the liquid is ejected from the corresponding orifice to form a flying ink droplet. In addition, each liquid flow path is configured to supply the ink liquid from a common liquid chamber communicating with the liquid flow paths.

FIG. 2 shows a schematic configuration of the above-described ink jet recording head. This recording head is
It comprises an electrothermal converter 103, an electrode 104, a liquid path wall 105, and a top plate 106 formed on a substrate 102 through a semiconductor manufacturing process such as vapor deposition and sputtering.

The recording ink liquid 112 is supplied from a liquid storage chamber (not shown) through the liquid supply pipe 107 to the recording head 10.
It is supplied into one common liquid chamber 108. In the figure, reference numeral 109 denotes a liquid supply pipe connector. The liquid 112 supplied into the common liquid chamber 108 is supplied into the liquid path 110 by capillary action, and is stably held by forming a meniscus at the discharge port surface at the tip of the liquid path. By energizing the electrothermal converter 103 in the liquid passage 110, the ink liquid on the surface of the electrothermal converter 103 is heated, and a bubbling phenomenon occurs. Ink droplets are ejected from.

With the above configuration, the discharge port density 4
A multi-ejection port ink jet recording head is formed with a high-density ejection port arrangement such as 00 dpi.

Next, a method of applying a voltage to the brush-like electrode 32 will be described with reference to FIGS.

First, the charging roller 31 has a configuration in which a conductive rubber is provided around a metal core, and a voltage of about +2 kV is applied to the metal core by a power supply 34.
The charging roller 31 comes into contact with the charging adsorption belt 4 to induce a positive charge on the belt 4.
When the recording sheet 7 comes into close contact with the belt 4, a negative charge is induced on the recording sheet 7 on the side of the belt 4, and an attraction force is generated between the recording sheet 7 and the belt 4. On the other hand, a positive charge is induced on the side of the recording sheet 7 opposite to the side of the belt 4 (the side facing the recording head 1), and a potential difference is generated between the recording head 1 and the recording sheet 7 to form an electric field. . The magnitude of this potential difference, that is, the strength of the electric field, is affected by the dielectric constant of the recording sheet 7 and the decay rate of the surface potential of the belt 4, which change depending on the surrounding temperature and humidity. This change in the strength of the electric field causes a shift in the landing position of the ink droplet, causing unintended image disturbance. Incidentally, conventionally, it was not possible to control the strength of the electric field.

In this embodiment, the surface potential measuring means 3
The control means 37 controls the output voltage of the variable power supply 36 according to the algorithm shown in FIG. 4 according to the value of the surface potential of the recording sheet 7 on the belt 4 measured by the recording sheet 7. The surface potential of the recording sheet 7 is set to a predetermined value (in the present embodiment, minus 100 V to plus 100 V) by controlling the amount of escape of the plus charges on the surface of the recording sheet 7.

First, the voltage Vc applied to the brush-like electrode 32 is set to a predetermined initial value (standard value) (step S2), and the voltage Vc is applied to the brush-like electrode 32. Recording sheet 7 by measuring means 33
Is measured (step S3), and based on the measurement result, the control means 37 obtains a voltage Vc required to maintain the surface potential of the recording sheet 7 between minus 100V and plus 100V (step S4). ), And uses the obtained voltage Vc as the output voltage of the variable power supply 36 (step S
6) Return to step S3. And recording sheet 7
The recording is started while the surface potential of the recording medium is kept between minus 100 V and plus 100 V (step S5). Such control is performed every time the recording sheet 7 passes.

As described above, since the surface potential of the recording sheet 7 is controlled to be between minus 100 V and plus 100 V, and the potential of the recording head 1 is set to "0" by grounding the electrode 35, the recording head 1 and the recording head 1 are recorded. The magnitude of the potential difference with the sheet 7, that is, the strength of the electric field is suppressed within a predetermined range. As a result, it is possible to avoid image disturbance due to displacement of the landing position of the ink droplet due to a change in the electric field. Ideally, it is preferable that the surface potential of the recording sheet 7 is set to “0” potential similarly to the recording head 1 and the potential difference therebetween is set to “0”. But,
The surface potential of the recording sheet 7 is set to minus 100 V to plus 1
A sufficient effect could be confirmed by setting the voltage to 00V.

The range for controlling the surface potential of the recording sheet 7 is not limited to the above range.
For example, the surface potential is increased from plus 100 V to plus 300
The ink droplet may be controlled to be in the range of V and the ink droplet may be negatively charged, and the ink droplet may be attracted to the recording sheet 7 by an electric force. In this case, a power supply for positively charging the electrode 35 may be connected between the electrode 35 and the variable power supply 36 in FIG.

In this embodiment, since the strength of the electric field can be controlled, the electric force acting on the ink droplet can be controlled to prevent unintended image disturbance due to a change in the electric force. Further, the surface potential of the recording sheet 7 may be charged to a predetermined negative range. In short, it is only necessary that the potential difference between the recording head 1 and the surface of the recording sheet 7 can be reduced.

[Second Embodiment] In the case of this embodiment, FIG.
As shown in FIG. 5, the power supply for applying a voltage to the core metal of the charging roller 31 is a variable power supply 38, the power supply for applying a voltage to the brush-like electrode 32 is a constant-pressure power supply 39, and the measured value of the surface potential measuring means 33 The control means 37 changes the variable power supply 3 accordingly.
8, the surface potential of the recording sheet 7 is controlled to control the potential difference between the surface of the recording sheet 7 and the recording head 1 within a predetermined range (ideally, the potential difference “0”). I try to keep it.

It should be noted that the power sources of both the brush-like electrode 32 and the charging roller 31 may be variable power sources and may be relatedly controlled.

[Third Embodiment] In the case of this embodiment, as shown in FIG. 6, a variable power supply 40 is connected to the electrode 35, and the control means 37 responds to the measured value of the surface potential measuring means 33. By controlling the output voltage of the variable power supply 40, the potential of the recording head 1 is controlled so that the potential difference between the recording head 1 and the surface of the recording sheet 7 falls within a predetermined range (ideally, the potential difference “0”). ).

In this embodiment, since there is no feedback sequence, there is an advantage that the time required for control is shorter than in the first and second embodiments.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for performing ink ejection, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44,558 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even in the case of the serial type as described above, a recording head fixed to the apparatus main body or an electric connection with the apparatus main body and ink from the apparatus main body can be provided by being mounted on the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

It is preferable to add a recording head ejection recovery unit, a preliminary auxiliary unit, and the like as the configuration of the recording apparatus of the present invention since the effects of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

The type and number of recording heads to be mounted are not limited to those provided only for one color ink, for example, and for a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiment of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or to prevent evaporation of the ink, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start solidifying when it reaches the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

Further, the form of the ink jet recording apparatus of the present invention is not limited to the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. It may take a form.

[0048]

As described above, the ink jet recording apparatus of the present invention measures the surface potential of the recording medium which is directly related to the potential difference between the recording head and the recording medium, and responds to the measurement result. Since the configuration is such that the potential difference between the recording head and the recording medium is adjusted, the surface potential of the recording medium is accurately measured without being affected by the dielectric constant of the recording medium that changes due to the surrounding temperature and humidity. Based on the measurement result, it is possible to accurately adjust the potential difference between the recording head and the recording medium to be kept within a predetermined range,
As a result, image disturbance due to the potential difference can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing a first embodiment of the present invention.

FIG. 2 is an enlarged configuration diagram of the recording head shown in FIG.

FIG. 3 is a schematic diagram of a recording sheet conveyance system shown in FIG. 1;

FIG. 4 is a flowchart for explaining the operation of the control means shown in FIG. 3;

FIG. 5 is a schematic diagram of a recording sheet conveyance system according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram of a recording sheet conveyance system according to a third embodiment of the present invention.

FIG. 7 is an enlarged sectional view of a tip portion of a recording head for explaining a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording head 4 Charging adsorption belt 7 Recording sheet (recording medium) 31 Charging roller 32 Brush electrode 33 Surface potential measuring means 34 Power supply 35 Electrode 36 Variable power supply 37 Control means 42 Electrothermal converter (pressure generating means) 43 Ink liquid

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-85044 (JP, A) JP-A-62-283151 (JP, A) JP-A-61-237653 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) B41J 2/01 B41J 2/05 B41J 29/00

Claims (3)

(57) [Claims] 1. A an ink jet recording head for discharging ink, and means for relatively moving the recording medium and the recording head, and the surface potential measuring means for measuring the surface potential of said recording medium, said recording head and said recording medium ink jet recording apparatus and an adjusting unit capable of adjusting the potential difference, characterized by comprising a control means for controlling said adjusting means in accordance with the value of the surface potential measured by the surface potential measuring means between. Wherein said control means includes a surface potential of said recording medium measured by the surface potential measuring means, the potential of the ink which the recording head ejects, sufficiently small differences in
2. The ink jet recording apparatus according to claim 1 , wherein the adjusting unit is controlled so as to keep the predetermined range . 3. The ink-jet recording head according to claim 1, further comprising an electrothermal conversion element for generating thermal energy for causing film boiling of the ink as energy used for discharging the ink. 2
3. The ink jet recording apparatus according to claim 1.