JP2002086764A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a yield of a manufacturing process from decreasing. SOLUTION: Dots to be formed when mutually combined ink drops break up or when mutually separated ink drops are not combined are adapted to overlap with each other.

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.

[0002]

2. Description of the Related Art An ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying apparatus, and a plotter includes a nozzle for discharging ink droplets and an ink flow path (discharge chamber, An ink jet head having a pressure chamber, a pressurized liquid chamber, a liquid chamber, etc.) and energy generating means for generating energy for pressurizing the ink in the ink flow path is mounted. By driving, the ink in the ink flow path is pressurized, and an ink droplet is ejected from a nozzle to record an image.

In an ink jet head used in this ink jet recording apparatus, a vibration plate forming a wall surface of an ink flow path is deformed by using a piezoelectric element as an energy generating means for generating energy for pressurizing ink in the ink flow path. So-called piezo type in which ink droplets are ejected by changing the internal volume of the ink flow path (JP-A-2-51).
No. 734), or a so-called bubble type in which an ink droplet is ejected by pressure generated by heating ink in an ink flow path using an exothermic resistor to generate bubbles (Japanese Patent Application Laid-Open No. 61-59911). Japanese Patent Application Laid-Open Publication No. HEI 9-131, the diaphragm and the electrode forming the wall surface of the ink flow path are arranged in parallel, and the diaphragm is deformed by the electrostatic force generated between the vibration plate and the electrode, thereby reducing the volume in the ink flow path. An electrostatic type in which ink droplets are ejected by changing the state (see JP-A-6-71882) is known.

In the conventional ink jet recording apparatus, an image is represented by a binary value based on ON / OFF of a dot of a fixed size, and this method does not require much gradation of characters and line drawings. Although there was no particular problem with images, it cannot be applied to images that require gradation such as photographs.

Therefore, in order to enable multi-value recording, a density modulation method in which the density is changed by having a plurality of inks of the same color having different densities, is formed by striking minute dots into the same position many times. A dot number modulation method for changing the size of a dot, a dot diameter modulation method for changing the size of a dot formed by separating a plurality of volumes (drop volumes) of ink droplets, and the like are employed.

[0006] Of these three methods, the density modulation method and the dot number modulation method are easy to realize, but the number of inks that must be mounted increases and the apparatus becomes larger, or the number of nozzles that can be mounted at one time is reduced. There is an inconvenience that the printing speed is sacrificed because of the limitation and the number of hits at the same location many times.

On the other hand, the dot diameter modulation method has an advantage that an image having high gradation can be formed without lowering the printing speed. In this case, the variable ink drop volume is
In the PZT method using a piezoelectric element, the drive voltage is increased or decreased. In the valve method using film boiling, a plurality of heaters are mounted. However, in these means, in the case of inkjet recording, since the capacity of the ejected ink droplet and the nozzle diameter, the configuration of the liquid chamber to be pressurized, the drive pulse waveform, and the like are complicatedly related, if the optimal combination is deviated. There is a risk that the ejection stability of the ink droplets may be significantly reduced, and the ink capacity cannot be changed much.

Therefore, as disclosed in JP-A-59-207265 and JP-A-60-157875, ink droplets generated in response to the first pressure pulse are:
Before separating from the meniscus surface, the second, third,. . . In some cases, a plurality of ink droplets connected to each other are ejected by applying the pressure pulse to make the total amount of the ink droplets variable, thereby enabling gradation control by dots.

[0009]

However, as described above, the next pulse is applied before the ink droplet ejected at the first pressure pulse separates from the liquid surface (meniscus surface) formed on the nozzle surface. When changing the ink drop volume by doing, the larger the ink drop volume, the more air resistance it receives, the easier it is to break up into small drops,
Image quality will be degraded.

It is also conceivable to change the ink droplet volume by ejecting the second to n-th droplets after the first droplet separates from the meniscus surface and combining the droplets during flight, thereby changing the ejection direction. If it deviates, it will land without being combined during flight, and the image quality will be similarly degraded.

The only way to prevent such droplet breakup and drop uncoupling (uncoalescing) is to perform adjustment on a nozzle-by-nozzle basis. Is difficult to perform, and the yield in the manufacturing process is significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an ink jet recording apparatus capable of suppressing a decrease in image quality and improving the yield of a manufacturing process.

[0013]

In order to solve the above-mentioned problems, an ink jet recording apparatus according to the present invention discharges a plurality of connected drops from a nozzle to form one drop, and the connected plurality of drops are flying. In this configuration, at least some of the dots formed when the dots are divided and landed overlap each other.

Here, it is preferable that the overlap ratio of dots formed when one of a plurality of connected drops breaks and lands during flight is 30% or more. In addition, it is preferable that the overlap ratio between dots formed when two of the connected plurality of droplets split and land during flight is 60% or more. Further, it is preferable that the vertical and horizontal size of the entire dot formed when a plurality of connected droplets divide and land during flight does not exceed the vertical and horizontal size of the dot formed when the plurality of droplets land without being separated.

[0015] The ink jet recording apparatus according to the present invention comprises:
A plurality of droplets separated from each other are ejected from the nozzle and combined during flight to form one drop, and at least a part of dots formed when the separated droplets land without being combined during flight overlap. It is configured.

Here, it is preferable that the overlap ratio between dots formed when one of a plurality of droplets separated from each other lands without being combined during flight is 30% or more. In addition, it is preferable that the overlap ratio of dots formed when two droplets of a plurality of droplets separated from each other land without being combined during flight is 60% or more. further,
It is preferable that the vertical and horizontal size of the entire dot formed when a plurality of droplets separated from each other land without being combined during flight does not exceed the vertical and horizontal size of the dot formed when the plurality of droplets are combined and landed.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of the mechanism.

This ink jet recording apparatus includes a carriage movable in the main scanning direction inside the recording apparatus main body 1, a recording head including an ink jet head mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. The paper feed cassette 4 or the manual feed tray 5 takes in the paper 3, and records the required image by the print mechanism 2, and then the output tray mounted on the rear side. 6 is discharged.

The printing mechanism 2 slides the carriage 13 in a main scanning direction (a direction perpendicular to the paper surface in FIG. 2) by a main guide rod 11 and a sub guide rod 12 which are guide members which are laterally mounted on left and right side plates (not shown). This carriage 1
3 is provided with a head 14 composed of an ink jet head for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet discharge direction facing downward. Above 13, each ink tank (ink cartridge) 15 for supplying each color ink to the head 14 is exchangeably mounted.

Here, the carriage 13 is slidably fitted to the main guide rod 11 on the rear side (downstream side in the paper transport direction), and the front side (downstream side in the paper transport direction) of the slave guide rod 1.
2 slidably mounted. The main scanning motor 1 is moved to scan the carriage 13 in the main scanning direction.
A timing belt 20 is stretched between a driving pulley 18 and a driven pulley 19, which are driven to rotate by 7, and the timing belt 20 is fixed to the carriage 13.

Although the heads 14 of the respective colors are used here as recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used. Furthermore, head 1
The ink jet head used as 4 is a piezo type which presses ink through a vibration plate forming a liquid chamber (ink flow path) wall with an electromechanical transducer such as a piezoelectric element, or a bubble generated by film boiling due to a heating resistor. A bubble type that pressurizes ink by generating it, or an electrostatic type that presses ink by displacing the diaphragm with electrostatic force between a diaphragm forming an ink flow path wall surface and an electrode facing the diaphragm Etc. can be used.

On the other hand, the paper 3 set in the paper feed cassette 4
Roller 21 and a friction pad 22 for separating and feeding the paper 3 from the paper feed cassette 4 and a guide member 23 for guiding the paper 3
A transport roller 24 that reverses and transports the fed paper 3, a transport roller 25 that is pressed against the peripheral surface of the transport roller 24, and a tip roller 26 that defines an angle at which the paper 3 is fed from the transport roller 24. Is provided. The transport roller 24 is driven to rotate by a sub-scanning motor 27 via a gear train.

A print receiving member 29 is provided as a paper guide member for guiding the paper 3 fed from the transport roller 24 below the recording head 14 in accordance with the moving range of the carriage 13 in the main scanning direction. I have. On the downstream side of the printing receiving member 29 in the sheet conveying direction, a conveying roller 31 and a spur 32, which are driven to rotate in order to send out the sheet 3 in the sheet discharging direction.
And a paper discharge roller 33 and a spur 34 for feeding the paper 3 to the paper discharge tray 6 and guide members 35 and 36 for forming a paper discharge path.

A reliability maintenance / recovery mechanism (hereinafter referred to as a "subsystem") 37 for maintaining and recovering the reliability of the head 14 is disposed on the right end side in the moving direction of the carriage 13. The carriage 13 is moved to the subsystem 37 side during printing standby, and the head 14 is capped by capping means or the like.

Next, an example of the ink jet head constituting the head 14 of the ink jet recording apparatus will be described with reference to FIGS. 3 is an exploded perspective view of the ink jet head, FIG. 4 is a cross-sectional explanatory view of the head along the longitudinal direction of the diaphragm, and FIG. 5 is an enlarged cross-sectional view of a main part of the head along the lateral direction of the diaphragm.

This ink jet head is, for example, a flow path substrate 41 which is a first substrate using a single crystal silicon substrate.
An electrode substrate 42 which is a second substrate using a silicon substrate, a glass substrate, a ceramics substrate or the like provided below the flow path substrate 41, and a nozzle which is a third substrate provided above the flow path substrate 41 A plurality of nozzles 44 for discharging ink droplets, a discharge chamber 46 which is an ink flow path communicating with each nozzle 44, and communication with each discharge chamber 46 via a fluid resistance portion 47 also serving as an ink supply path. A common liquid chamber 48 is formed.

A through hole is formed in the flow path substrate 41 to form a plurality of discharge chambers 46 communicating with the nozzles 44, and a diaphragm 50 is formed on the lower surface of the flow path substrate 41 and forms a bottom surface which is a wall surface of the discharge chamber 46.
Is in contact with The nozzle plate 43 has a hole for forming the nozzle 44 and a groove for forming the fluid resistance portion 47, and the passage substrate 41 and the electrode substrate 42 have a through portion for forming a common liquid chamber 48.

A p-type or n-type single crystal silicon substrate is used as the electrode substrate 42, and the oxide layer 4 is formed by a thermal oxidation method or the like.
2a, a concave portion 54 is formed in the oxide layer 42a, and an electrode 55 facing the diaphragm 50 is formed on the bottom surface of the concave portion 54.
Is provided, a gap 56 is formed between the diaphragm 50 and the electrode 55, and the diaphragm 50 and the electrode 55 constitute a microactuator.

The electrode 55 is made of gold, Al, C which is generally used in a process of forming a semiconductor element.
Metal materials such as r and Ni, refractory metals such as Ti, TiN, and W, and polycrystalline silicon materials whose resistance is reduced by impurities can be used. And this electrode 55
Is covered with an electrode protection film 57, and the electrode 55 is extended outside to form a connection portion (electrode pad portion) 55a, on which an FPC cable in which a driver IC as a head drive circuit is mounted by wire bonding. They are connected via an anisotropic conductive film or the like.

The nozzle plate 43 has a large number of nozzles 44 and a groove for forming a fluid resistance portion 47 for communicating the common liquid chamber 48 and the discharge chamber 46.
Here, a water-repellent film is formed on the ink ejection surface (the surface side of the nozzle 44). The nozzle plate 3 is made of a stainless steel substrate (SUS). In addition, a nickel plating film formed by an electroforming (electroforming) method, a resin made of polyimide or the like subjected to excimer laser processing, and a metal plate formed by pressing. Drilled holes can also be used.

In the ink jet head configured as described above, the diaphragm 50 is used as a common electrode, and the electrode 55 is used as an individual electrode. Electrostatic force (electrostatic attraction force) is generated between the electrode 55 and the electrode 55, and the diaphragm 50
Deforms and displaces to the 5th side As a result, the inner volume of the discharge chamber 46 is expanded and the internal pressure is reduced, so that the discharge chamber 6 is filled with ink from the common liquid chamber 48 via the fluid resistance part 47.

Next, when the voltage application to the electrode 55 is stopped,
The electrostatic force stops working, and the diaphragm 50 is restored by its own elasticity. With this operation, the internal pressure of the ejection chamber 46 increases, and ink droplets are ejected from the nozzles 44. When a voltage is applied to the electrode 55 again, the diaphragm 50 is drawn toward the electrode again by the electrostatic attractive force.

Next, an outline of the head drive control section of the ink jet recording apparatus will be described with reference to FIG.
The head drive control unit includes a main control unit 61 that controls the entire recording apparatus, a waveform generation circuit 62, an amplifier 63,
And a drive circuit (driver IC) 64 and the like. The main control unit 61 includes a microcomputer, a ROM storing required fixed information, and an R used as a working memory.
AM, an image memory for storing data obtained by processing image data transferred from the host, and a parallel input / output (PI
O) It has a port, an input buffer and the like.

Then, the main control section 61 controls the waveform generation circuit 6
2 for generating a drive waveform, and a print signal (serial data) S to the driver IC 64.
D, a shift clock CLK, a latch signal LAT, and the like.

The waveform generation circuit 62 is composed of a D / A converter or the like, and converts the voltage data supplied from the main control unit 61 into a D / A signal.
The A-conversion generates energy for discharging ink droplets between the diaphragm 50 and the electrode 55 of the ink jet head. And generates and outputs a driving waveform for displacing the driving waveform. In this embodiment, a driving waveform that includes three driving pulses in one driving cycle is used.

The driver IC 64 receives the drive waveform Pv supplied from the waveform generation circuit 62 via the amplifier 63, selects the number of drive pulses corresponding to the print signal, and selects each of the individual ink jet heads constituting the head 14. Electrode 5
Give 5

That is, the driver IC 64 includes a shift register 65 for inputting the serial clock CLK from the main control section 61 and the serial data SD as a print signal;
A latch circuit 66 for latching a register value of the shift register 65 with a latch signal LAT from the main control unit 61, and a level conversion circuit 6 for changing an output value of the latch circuit 66 to a level
7 and an analog switch array 68 whose on / off is controlled by the level conversion circuit 67. The analog switch array 68 includes analog switches AS1 to ASm connected to m individual electrodes 55 of the inkjet head (the number of nozzles is m). The diaphragm 50 serving as a common electrode of the ink jet head is grounded.

Then, serial data (print signal) SD is fetched into the shift register 65 according to the shift clock, and the serial data SD fetched into the shift register circuit 65 by the latch signal LAT by the latch circuit 66.
Is latched and input to the level conversion circuit 67. The level conversion circuit 67 turns on / off the analog switch ASm (m = 1 to m) connected to the individual electrode 55 of each actuator according to the content of the data.

This analog switch ASm (m = 1 to
Since the drive waveform Pv is given to the m) from the waveform generation circuit 62, the drive waveform when the analog switch ASm (m = 1 to m) is turned on is selectively given to the individual electrode 55.

Next, the operation of the head drive control unit in the ink jet recording apparatus thus configured will be described with reference to FIG.
This will be described with reference to FIG. First, as described above, the waveform generation circuit 62 generates and outputs three drive pulses P (P1, P2, and P3) in one drive cycle in a time series as shown in FIG. 7A. Are supplied to the analog switches AS1 to ASm of the driver IC 64.

Here, by performing data transfer for each drive pulse P to turn on / off the analog switch ASn (n = 1... M), the analog switch ASn is turned on as shown in FIG. The on-time width can be selected.
Thereby, as shown in FIG. 7C, the number of driving pulses P to be passed can be changed, and multi-valued small dots, medium dots, and large dots are realized according to the number of passing pulses. be able to.

Next, the operation of the ink jet recording apparatus configured as described above will be described with reference to FIGS. First, when the above-described head drive control unit is used, by adjusting the interval t of each drive pulse P,
A plurality of ink droplets connected to each other are ejected to form one ink droplet to form a dot, or a plurality of ink droplets separated from each other are ejected and united (combined) during flight to form one ink droplet. Can be formed to form dots.

For example, as shown in FIG. 8, by giving the second drive pulse P2 before the ink droplet I1 ejected by the first drive pulse P1 leaves the meniscus surface, the ink droplet I1 The droplets I2 are ejected in a connected state, and a third drive pulse P3 is given before the ink droplets I2 are separated from the meniscus surface.
Are ejected in a connected state, and these connected ink drops I1, I2, and I3 are ink drops I2 and I3 because the first ejected ink drop I1 receives air resistance. Ink droplet I absorbed by I1
123, and finally arrives as one ink droplet I.

Further, as shown in FIG. 9, immediately after the ink droplet I1 ejected by the first drive pulse P1 leaves the meniscus surface, the second drive pulse P2 is applied to the ink droplet I1 so that the ink droplet I1 is discharged from the ink droplet I1. When the separated ink droplet I2 is ejected, and immediately after the ink droplet I2 is separated from the meniscus surface, a third drive pulse P3 is applied to eject the ink droplet I3 separated from the ink droplet I2. During the flight, the ink drop I2 catches up with the ink drop I1 and merges into the ink drop
The ink droplet I3 catches up with these combined ink droplets I12, and combines to form an ink droplet I123, and finally lands as one ink droplet I.

As a result, for example, as shown in FIG. 10, a dot Ds as shown in FIG. 10A is formed by one driving pulse, and as shown in FIG. 10B by two driving pulses. A dot Dm larger than the dot Ds is formed, and a dot Dl (D1>Dm> Ds) larger than the dot Dm is formed by three drive pulses as shown in FIG.

By using the ink droplets subjected to such dot diameter modulation, multi-valued area gradation can be performed as shown in FIG. FIG. 11A illustrates the case where the dot Ds is used, FIG. 10B illustrates the case where the dot dm is used, and FIG. 10C illustrates the case where the dot Dl is used.

However, when a plurality of ink droplets connected to each other are ejected as shown in FIG. 8, if the ink droplet speed is too high, the ink droplets I1 and I2 connected to each other as shown in FIG. , I3 are split during the flight and land as independent ink droplets I1, I2, I3 as they are, and as shown in FIG.
The three dots D1 to D3 are formed by I3.

In the case where a plurality of ink droplets separated from each other are ejected as shown in FIG. 9, if a bend occurs in the flight direction of the ink droplets, as shown in FIG. Ink drops I1, I2, I
3 fly as it is and independent ink drops I1, I2, I3
And the ink droplets I as shown in FIG.
Three dots D1 to D3 are formed by 1, I2 and I3.

As described above, when a plurality of ink droplets land separately from each other, the image quality is greatly deteriorated unlike the normal satellite generation. That is, as shown in FIG. 14A, even when the satellite droplet S is generated with respect to the main droplet Im, the satellite droplet S is usually very small with respect to the main droplet Im. As shown, the influence of the satellite dots Sd on the main dots Md is small, and the image quality does not significantly decrease.

On the other hand, if a plurality of ink droplets land separately due to a failure in the combination, the ink droplets are not originally combined into one droplet for several dots, and the individual ink droplets are not different from the main droplet. This is the same as the occurrence of satellite dots of the same size as the main dots.

As a result, for example, in the case of printing a dense image of dots as shown in FIG.
As shown in FIG. 16, when the dense portion of the dot is crushed and the resolution is reduced, or when a ruled line or the like as shown in FIG. 16A is printed, it does not exist as shown in FIG. A false line L1, which is supposed to occur, occurs. On the other hand, a normal satellite is affected to some extent as shown in FIGS. 17 (a) and (b).
There is no quality degradation as shown in FIG.

The above-described division or failure of the ink drop is caused by a change with time or environmental conditions, but is often caused by variations in a manufacturing process and mutual interference at the time of driving the head. For example, when there is a processing residue 81 such as a burr in the nozzle 80 as shown in FIG. 18A, and when there is a displacement of the joining position between the nozzle 80 and the flow path 82 as shown in FIG. As shown in FIG.
For example, when the dust 83 adheres to the zero, the ejection direction is bent.

As shown in FIG. 19, when the head is driven, the pressure vibration caused by the pressurization of the flow path 82 propagates to another flow path 82 via the partition wall 84, or to another flow path via the common liquid chamber 85. When mutual interference such as propagation to the nozzle 82 occurs, the pressure of the flow path 82 fluctuates and the speed of the ejected ink droplets increases.
It will vary by 0.

In order to prevent the above-described division of the ink droplets and the uncoupling (uncoalescence) of the ink droplets, it is necessary to perform adjustment for each nozzle. However, for a high-density head having several hundred channels per head, It is not easy to adjust the nozzle, and the yield in the manufacturing process will be reduced.

Therefore, in this ink jet recording apparatus, first, two connected drops are ejected, and the positional relationship between two dots formed when the connected two drops are split during flight and landed, and the separation. 2 formed when the two droplets landed without being combined during flight
By changing the positional relationship between the three dots, the quality of characters, the quality of ruled lines, the resolution, the graininess of a shadow portion, and the graininess of a highlight portion were evaluated. The result is shown in FIG.

From this evaluation result, it can be seen that if the positional relationship between the two dots overlaps by 30% or more in terms of the dot diameter conversion ratio, a certain quality can be obtained. Therefore, the parameters of the drive pulse (voltage,
(Rise time constant, fall time constant, pulse width, etc.) and the intervals of each drive pulse are set, and even if a dot to be formed by one drop is formed by two ink drops, The positional relationship of the formed dots overlaps by 30% or more in terms of the dot diameter conversion ratio. This makes it possible to perform multi-value recording with a simple configuration while suppressing a significant decrease in image quality.

Next, three connected drops are ejected, the positional relationship between the three dots formed when the connected three drops split and land during flight, and the three separated drops during flight. By changing the positional relationship between the three dots formed when they landed without being combined, the quality of characters, the quality of ruled lines, the resolution, the graininess of shadow portions, and the graininess of highlight portions were evaluated. The result is shown in FIG.

From this evaluation result, it can be seen that if the positional relationship of two of the three dots overlaps by 60% or more in terms of the dot diameter conversion ratio, it is possible to obtain a reasonable quality.
Therefore, the parameters of the drive pulse (voltage, rise time constant, fall time constant,
Pulse width, etc.) and the interval of each driving pulse, and even if a dot to be formed by one drop is formed by three ink drops, the positional relationship between the dots formed by two ink drops is The diameter conversion rate was set so as to overlap by 60% or more. As a result, it is possible to perform a wider range of multi-valued printing than in the case of FIG. 19 with a simple configuration while suppressing a significant decrease in image quality.

Further, based on these results, a plurality of connected droplets are ejected, the positional relationship between a plurality of dots formed when the connected plurality of droplets divide and land during flight, and the plurality of separated droplets. As a result of studying the positional relationship of a plurality of dots formed when the ink droplets are landed without being combined during the flight, the overall length and width of the dots formed by the plurality of ink droplets are combined or separated. If the size does not exceed the vertical and horizontal sizes of the dots formed when the ink droplet lands, the multi-value recording can be performed with a simple configuration while suppressing a significant decrease in image quality.

Therefore, by setting the parameters (voltage, rise time constant, fall time constant, pulse width, etc.) of the drive pulse that forms the drive waveform to be applied to the head and the interval between each drive pulse, a plurality of ink droplets can be used. The vertical and horizontal sizes of the formed dots are set so as not to exceed the vertical and horizontal sizes of the dots formed when a plurality of droplets are landed without being combined or separated.

In this way, even if division or uncoalescing occurs in multi-value recording, it can be tolerated with a small margin, and the yield in the manufacturing process can be improved while maintaining image quality.

In the above embodiment, an example is described in which the ink jet head is an electrostatic ink jet head. However, a piezo ink jet head using a piezoelectric element or a bubble ink jet head using a heating resistor is used. For example, the present invention can also be applied to a case where the drive of another type of inkjet is controlled.

[0063]

As described above, according to the ink jet recording apparatus of the present invention, the ink jet recording apparatus of the present invention forms a single droplet by discharging a plurality of mutually connected droplets from a nozzle. At least a part of the dots formed when a plurality of droplets split and land during flight overlap, so that the yield in the manufacturing process can be improved while suppressing a decrease in image quality. .

Here, by setting the overlap ratio between dots formed when one of a plurality of connected droplets divides during the flight and lands, it is not less than 30%, the production can be performed while suppressing the deterioration of image quality. The yield in the process can be improved.

Further, by setting the overlapping rate of dots formed when two of the plurality of connected droplets split and land during the flight to be 60% or more, deterioration in image quality can be suppressed. The yield in the manufacturing process can be improved.

Furthermore, the vertical and horizontal size of the entire dot formed when a plurality of droplets connected to each other are divided during flight and landed does not exceed the vertical and horizontal size of the dot formed when the plurality of droplets land without being separated. Thus, the yield in the manufacturing process can be improved while suppressing a decrease in image quality.

According to the ink jet recording apparatus of the present invention, a plurality of droplets separated from each other are ejected from the nozzle and combined during flight to form a single droplet, and the separated plurality of droplets land without being combined during the flight. Since at least some of the dots that are sometimes formed overlap each other, it is possible to improve the yield in the manufacturing process while suppressing a decrease in image quality.

Here, the overlapping rate of dots formed when one of a plurality of droplets separated from each other lands without being combined during flight is set to 30% or more, thereby suppressing deterioration in image quality. The yield in the manufacturing process can be improved.

Further, by setting the overlap ratio between dots formed when two of the plurality of droplets separated from each other land without being combined during flight to be 60% or more, it is possible to suppress a decrease in image quality. The yield in the manufacturing process can be improved.

Further, the vertical and horizontal size of the entire dot formed when a plurality of droplets separated from each other land without being combined during flight exceeds the vertical and horizontal size of the dot formed when the plurality of droplets are combined and landed. By not having the above, the yield in the manufacturing process can be improved while suppressing the deterioration of the image quality.

[Brief description of the drawings]

FIG. 1 is a schematic perspective explanatory view of a mechanism section of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory side view of the mechanism.

FIG. 3 is an exploded perspective view of a head of the recording apparatus.

FIG. 4 is an explanatory cross-sectional view of the head in the longitudinal direction of the diaphragm.

FIG. 5 is an enlarged sectional explanatory view of a main part of the head in the transverse direction of the diaphragm;

FIG. 6 is a block diagram illustrating an example of a head drive control unit of the recording apparatus.

FIG. 7 is an explanatory diagram for explaining the operation of the head drive control unit;

FIG. 8 is an explanatory diagram for explaining a case where a plurality of ink droplets connected to each other are ejected to form one dot;

FIG. 9 is an explanatory diagram for explaining a case where one dot is formed by discharging a plurality of ink droplets separated from each other;

FIG. 10 is an explanatory diagram of dots obtained by dot formation in FIG. 8 or FIG.

FIG. 11 is an explanatory diagram illustrating area gradation using the dots in FIG. 10;

FIG. 12 is a diagram showing an example of ejecting a plurality of ink droplets connected to each other;
Explanatory drawing for explanation of the case of division when forming dots

FIG. 13 is a diagram showing a state in which a plurality of ink droplets separated from each other are ejected.
Explanatory drawing for explanation when dots are not combined when forming dots

FIG. 14 is an explanatory diagram for explaining the occurrence of normal satellite dots.

FIG. 15 is an explanatory diagram provided for describing a character image when division or non-combination occurs;

FIG. 16 is an explanatory diagram serving to explain a ruled line image when division or uncoupling has occurred;

FIG. 17 is an explanatory diagram for explaining a character and a ruled line image when a normal satellite is generated;

FIG. 18 is an explanatory diagram for explaining the cause of the occurrence of bending of the injection direction.

FIG. 19 is an explanatory diagram for explaining a cause of a variation in ink droplet speed;

FIG. 20 is an explanatory diagram illustrating the relationship between the case where two ink droplets are split or uncombined and the image quality.

FIG. 21 is an explanatory diagram illustrating the relationship between the case where three ink droplets are split or uncombined and the image quality.

[Explanation of symbols]

13: carriage, 14: head, 24: transport roller,
33: paper ejection roller, 40: ink jet head, 41
... channel substrate, 42 ... electrode substrate, 43 ... nozzle plate, 44 ...
Nozzle, 46: discharge chamber, 47: fluid resistance part, 48: common liquid chamber, 50: diaphragm, 55: electrode, 56: gap, 6
DESCRIPTION OF SYMBOLS 1 ... Main control part, 62 ... Waveform generation circuit, 91 ... Main control part
64: Driver IC, 65: Shift register, 66: Latch circuit, 67: Level conversion circuit, 68: Analog switch array

Claims (8)

[Claims] 1. An ink jet recording apparatus in which a plurality of interconnected droplets are ejected from a nozzle to form one droplet to enable area gradation, and when the connected plurality of droplets split and land during flight. An ink jet recording apparatus, wherein at least a part of dots to be formed overlap. 2. The ink jet recording apparatus according to claim 1, wherein an overlap ratio between dots formed when one of the plurality of connected droplets divides and lands during flight is 30% or more. An ink jet recording apparatus comprising: 3. The ink jet recording apparatus according to claim 1, wherein an overlapping rate of dots formed when two of the connected plurality of droplets are split and landed during flight is 60%. An ink jet recording apparatus characterized by the above. 4. The ink jet recording apparatus according to claim 1, wherein a plurality of droplets are separated by a total of vertical and horizontal sizes of dots formed when the connected plural droplets divide during flight and land. An ink jet recording apparatus characterized in that the size does not exceed the vertical and horizontal sizes of dots formed when the ink droplet lands. 5. An ink jet recording apparatus in which a plurality of droplets separated from each other are ejected from a nozzle and combined during flight to form a single droplet to enable area gradation, the plurality of separated droplets are combined during flight. An ink jet recording apparatus characterized in that at least some of the dots formed when the ink droplets land without being overlapped. 6. The ink jet recording apparatus according to claim 5, wherein an overlap ratio of dots formed when one of the plurality of separated droplets lands without being combined during flight is 30% or more. An ink jet recording apparatus, comprising: 7. The ink jet recording apparatus according to claim 5, wherein an overlap ratio of dots formed when two of the plurality of separated droplets land without being combined during flight is 60. % Or more. 8. The ink jet recording apparatus according to claim 5, wherein a plurality of droplets formed when said plurality of separated droplets land without being combined during flight have a plurality of droplets. An ink jet recording apparatus characterized in that it does not exceed the vertical and horizontal sizes of dots formed when all are combined and landed.