JP2006110750A - Inkjet recording apparatus and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate beading caused by temperature rise.
SOLUTION: For a multi-pass mask pattern that easily causes beading due to an increase in the temperature of the recording head, only a part of the recording nozzles having a high ejection duty is thinned out, and the beading occurs even when the head temperature increases. Always get enough image quality.
[Selection] FIG.

Description

  The present invention relates to an ink jet recording apparatus that performs recording by ejecting ink from nozzles, and more particularly, to a recording head formed by arranging a plurality of nozzle groups including a plurality of nozzles in the same main recording scanning region on a predetermined recording medium. In contrast, the present invention relates to a recording apparatus employing a so-called multi-pass method in which main scanning is performed a plurality of times by different nozzle groups, a thinned image is formed according to a thinning mask pattern by each main scanning, and the image is completed. The present invention relates to reduction of image deterioration factors such as ink beading, density unevenness and white stripes.

  A recording apparatus such as a printer, a copying machine, or a facsimile is configured to record an image formed of a dot pattern on a recording medium such as paper or a plastic thin plate based on image information. This recording apparatus can be classified according to the recording system into an ink jet system, a wire dot system, a thermal system, a laser beam system, etc. Among them, a recording apparatus (ink jet recording apparatus) using the ink jet system is a recording head. Ink (recording liquid) droplets are ejected and ejected from the ejection opening of the nozzle, and this is adhered to a recording medium for recording.

  In recent years when many recording devices are used, high-speed recording, high resolution, high image quality, low noise, and the like are required for the recording devices, and examples of the recording devices that meet such requirements include the inkjet recording device. be able to. In this ink jet recording apparatus, since recording is performed by ejecting ink from a recording head, stabilization of ink ejection and stabilization of ink ejection amount are required to satisfy the above requirements.

  In particular, as a means of obtaining high-definition, high-gradation, high-quality print images, it is considered that a method for improving the resolution by reducing the volume of ink to be ejected, narrowing the arrangement interval of the ejection ports, is considered particularly effective. Therefore, a high response frequency of the discharge port and the ink discharge head for discharging a stable ink droplet volume and landing on the recording medium with high accuracy is required. For this reason, in the ink jet recording apparatus, various improvements on the apparatus main body side such as a recovery apparatus have been made, but stabilization of the ink discharge amount largely depends on the performance of the recording head alone. In other words, slight errors that occur during the recording head manufacturing process, such as the shape of the discharge head of the recording head and the variation of the electrothermal transducer (discharge heater), have a large effect on the amount of ink discharged and the direction of the discharge direction. As a result, density unevenness of the finally formed image is a cause of deterioration of image quality.

  Note that multi-pass printing is known as a technique for eliminating density unevenness caused by variations in the discharge amount of each nozzle of an inkjet head (for example, Patent Document 1).

Further, in the thermal ink jet system that ejects ink using thermal energy, it is known that the ink foaming state and the fluid physical properties of the ink change due to the temperature rise of the recording head, and the ink ejection amount tends to increase. In addition, in order to suppress an increase in ejection amount due to a temperature rise, a configuration for controlling a recording head drive pulse according to a temperature change has been conventionally known (for example, Patent Document 2). However, it is difficult to control the pulse so as to completely suppress the variation in the discharge amount, and the control becomes complicated. When the ink discharge amount is increased, in a region where the recording duty is high, different inks are mixed with each other on the recording medium, and image quality called beading may be deteriorated.
Japanese Patent Laid-Open No. 07-060968 Japanese Patent Laid-Open No. 06-297718

  In the conventional technology, as a means to obtain high-definition and high-gradation high-quality print images, the recording duty is set high in order to reduce the volume of ink to be ejected, narrow the interval between the ejection openings and improve resolution There was a need to do. In addition, the temperature rise of the recording head is unavoidable due to the necessity, and the volume of ejected ink droplets tends to increase, and different inks mix on the recording medium, degrading the image quality called beading. was there. The present invention has been made paying attention to the above-mentioned problems of the prior art, and an object thereof is to provide an ink jet recording apparatus and an ink jet recording method capable of reducing beading caused by temperature rise in the recording head. .

  In order to achieve the above object, the present invention has the following configuration.

  That is, the present invention uses a recording head in which a plurality of nozzle groups each having a plurality of nozzles are arranged, and performs a main movement a plurality of times by forward and backward movements of different nozzle groups with respect to the same main recording scanning area on a predetermined recording medium. In an ink jet recording apparatus that performs scanning and forms a thinned image according to a thinning mask pattern in each main scan to complete the image, a means for measuring the temperature or temperature rise of the recording head, and a measured value by the measuring means is a predetermined value A means for determining whether or not the above is satisfied, and means for storing a plurality of types of thinning mask patterns in which the same recording scanning area is divided at a predetermined pitch and the recording duty is set to a different value in each divided area. The mask pattern to be used differs depending on the temperature of the head or the temperature rise.

  Further, the present invention selects a mask pattern that increases the thinning-out rate of the divided area having a relatively high recording duty when the determination means determines that the temperature of the recording head or the value of the temperature increase is equal to or greater than a predetermined value. It is desirable.

  Further, if each recording scan area is divided and a different recording duty is set for each divided recording area, it is possible to prevent density unevenness (white stripes) as seen at the pitch of the paper feed width.

  As described above, according to the present invention, with respect to a multi-pass mask pattern that tends to cause beading due to a rise in the temperature of the print head, only a part of the print nozzles having a high discharge duty is thinned, and the head temperature rises. Even if it does not raise beading, the inkjet recording device which can always obtain sufficient image quality can be provided.

  Further, if each recording scan area is divided and a different recording duty is set for each of the divided recording areas, it is possible to prevent density unevenness (white stripes) as seen at the pitch of the paper feed width.

  Hereinafter, an embodiment according to a recording apparatus of the present invention will be described with reference to the drawings.

  An embodiment in which the image forming apparatus according to the present invention is applied to an ink jet printer will be described in detail with reference to FIGS. 1 to 9, but the present invention is not limited to such an embodiment, and these may be further combined. The present invention can also be applied to other technologies that are included in the concept of the present invention described in the claims of this specification.

  The external appearance of the mechanism part of the ink jet printer in this embodiment is shown in FIG. 1, the external appearance of the head cartridge used in the ink jet printer is shown in FIG. 2, and the external appearance of the print head is shown in FIG. That is, the chassis 10 of the ink jet printer in this embodiment is composed of a plurality of plate-like metal members having a predetermined rigidity, and forms the skeleton of this ink jet printer. For the chassis 10, a medium feeding unit 11 that automatically feeds a sheet-like print medium (not shown) into the ink jet printer, and a print medium that is fed one by one from the medium feeding unit 11 are desired. A medium transport section 13 that guides the print medium from the print position to the medium discharge section 12, a print section that performs a predetermined print operation on the print medium transported to the print position, and a recovery for the print section. A head recovery unit 14 that performs processing is assembled.

  The print unit includes a carriage 16 that is supported so as to be able to scan and move along the carriage shaft 15, and a head cartridge 18 that is detachably mounted on the carriage 16 via a head set lever 17.

  The carriage 16 on which the head cartridge 18 is mounted is engaged with a carriage cover 20 for positioning the print head 19 of the head cartridge 18 at a predetermined mounting position on the carriage 16 and a tank holder 21 of the print head 19. The above-described head set lever 17 is provided to press the print head 19 so as to be positioned at a predetermined mounting position. The head set lever 17 as the attaching / detaching means of the present invention is provided on the upper portion of the carriage 16 so as to be rotatable with respect to a head set lever shaft (not shown), and the engaging portion with the print head 19 is spring-biased. A head set plate (not shown) is provided and is mounted on the carriage 16 while pressing the print head 19 by the spring force of the head set plate.

  One end of a contact flexible print cable (hereinafter referred to as a contact FPC) 22 (not shown) is connected to another engagement portion of the carriage 16 with respect to the print head 19, and a contact (not shown) formed at one end of the contact FPC 22. And the contact part 23 which is an external signal input terminal provided in the print head 19 are in electrical contact so that various information for printing can be exchanged and power can be supplied to the print head 19. It has become.

  An elastic member such as rubber (not shown) is provided between the contact portion of the contact FPC 22 and the carriage 16, and the contact portion of the contact FPC 22 and the print head 19 are set by the elastic force of the elastic member and the pressing force by the headset plate. The contact portion 23 can be reliably contacted. The other end of the contact FPC 22 is connected to a carriage substrate (not shown) mounted on the back surface of the carriage 16.

  The head cartridge 18 in the present embodiment discharges ink supplied from the ink tank 24 from the ink outlet 24 (see FIG. 4) of the print head 19 in accordance with print information. And a print head 19. The print head 19 of this embodiment employs a so-called cartridge system that is detachably mounted on the carriage 16.

  Further, in this embodiment, in order to enable high-quality color printing with photographic tone, for example, six ink tanks 24 in which black, light cyan, light magenta, cyan, magenta and yellow inks are independent. Can be used. Each ink tank 24 is provided with an elastically deformable detachable lever 26 that can be locked with respect to the head cartridge 18. By operating the detachable lever 25, as shown in FIG. 19 can be removed. Therefore, the detaching lever 26 functions as a part of the attaching / detaching means of the present invention.

  The print head 19 includes a print element substrate 27 described later, the tank holder 21 described above, and the like. FIG. 4 shows the fracture structure of the print element substrate 27 of the print head 19 in this embodiment, FIG. 5 shows the arrangement of the discharge ports, and FIG. 6 shows the AA ′ cross-sectional structure thereof. The print element substrate 27 in this embodiment forms a discharge energy generating portion, a common ink chamber 31, an ink path 33, a discharge port 25, and the like on a silicon substrate having a thickness of 0.5 mm to 1 mm using a film forming technique. It is a thing. That is, the print element substrate 27 is formed with an elongated hole-like ink supply port 28 penetrating therethrough. On both sides of the ink supply port 28, a plurality of (256 in this embodiment) electrothermal transducers 29 arranged in two rows at a predetermined interval along the print medium conveyance direction, that is, the longitudinal direction of the ink supply port 28. Are formed in a state shifted from each other by a half pitch. The center-to-center distance of each row is 233 μm, and each forms a discharge energy generation unit. In addition to these electrothermal transducers 29, the printed element substrate 27 includes electrode terminals 30 for electrical connection between the electrothermal transducers 29 and the printer main body and electrical wiring (not shown) formed of aluminum or the like. It is formed by a film forming technique.

  The electrical wiring board 36 connected to the electrode terminals 30 formed on the print element board 27 is for applying an electrical signal for ejecting ink to the print element board 27. It has a corresponding electrical wiring and the above-mentioned contact portion 23 for receiving an electrical signal from the printer main body located at the end of this electrical wiring, and this contact portion 23 is positioned on the back side of the tank holder 21. It is fixed. A drive signal for the electrothermal transducer 29 is given from a drive IC (not shown) via the electrical wiring board 36, and at the same time, drive power is supplied to the electrothermal transducer 29.

  An ink flow path extending from the ink tank 24 to the ink supply port 28 of the print element substrate 27 is formed in the tank holder 21 that detachably holds the ink tank 24.

  On the print element substrate 27, an upper plate member 32 having a plurality of ejection ports 25 respectively facing the electrothermal transducer 29 via a common ink chamber 31 communicating with the ink supply port 28 is formed. That is, an ink path 33 that communicates with each ejection port 25 and the common ink chamber 31 is formed between the upper plate member 32 and the print element substrate 27, and a partition wall is formed between the adjacent ink paths 33. 34 is formed. The common ink chamber 31, the ink path 33, the partition wall 34, and the like are formed together with the upper plate member 32 by photolithography technology in the same manner as the ejection port 25.

  The liquid supplied into each ink path 33 from the ink supply port 28 boils as the electrothermal conversion body 29 generates heat by giving a drive signal to the electrothermal conversion body 29 facing the corresponding ink path 33. , And is discharged from the discharge port 25 by the pressure of the bubbles generated thereby. In this case, bubbles generated in the liquid chamber 31 are brought into an air communication state from the discharge port 25 as they grow.

(First embodiment)
A first example of the above embodiment will be described.

  FIG. 7 is a flowchart showing the operation of the printer of this embodiment. Here, when an event occurs, if the event is a printing operation, printing is performed, and when printing of all pages is completed, the process returns to the event waiting state, and processing is also performed in the end processing and other events. Indicates that the event is waiting.

  FIG. 8 is a block diagram showing the image processing unit in the embodiment of the present invention.

  FIG. 9A is an explanatory diagram showing a 4-pass multi-pass printing operation, and FIGS. 9B and 9C are explanatory diagrams showing a mechanism of density unevenness due to a dot firing order difference in a reciprocating printing operation.

  FIG. 10 is an explanatory vertical cross-sectional side view showing the mechanism of ink permeation into the recording medium, and describes the mechanism of permeation in time series. FIG. 11 is a diagram showing the surface coverage calculated for each pass in the case of 4-pass printing. FIG. 12 is a diagram showing the recording duty in each pass in the 4-pass printing. FIG. 12A shows a case where normal multi-pass printing is performed in which each printing scan area is printed with a uniform duty (25%), and FIG. 12B shows that the printing duty of each printing area is different. A case where the surface coverage of the ink on the recording medium is controlled is shown.

  13A and 13B are diagrams showing the recording duty in each pass in 4-pass printing. FIG. 13A shows a case where each recording scanning area is recorded with a uniform duty (25%), and FIG. 13B shows each recording area. A case where the recording duty is divided into two and the recording duty of each region is different is shown. FIG. 14 is a schematic diagram of an image formed in 4-pass printing, and shows a case where each pass area is divided into two and the print duty in each area is set to a different value.

  FIG. 15 is a schematic diagram of an image formed in four-pass printing. (A) shows a case where each pass area is formed with a uniform recording duty, and (b) shows that each pass area is divided into two parts. A case where the recording duty in each region is set to a different value is shown.

  16 to 19 are used to explain the cause of density unevenness in the print head and multi-pass printing for eliminating the density unevenness.

  FIG. 16A is a schematic diagram illustrating an appropriate ejection state of ink droplets ejected from the recording head, and FIG. 16B is a schematic diagram illustrating an image having no droplet density unevenness obtained by ejection of ink droplets in FIG. (C) is a diagram showing the density distribution of the image shown in FIG.

  FIG. 17A is a schematic diagram illustrating a variation state of ink droplets ejected from the recording head, and FIG. 17B is a schematic diagram illustrating an image with droplet density unevenness obtained by ejecting the ink droplets of FIG. (C) is a diagram showing the density distribution of the image shown in FIG.

  18A and 18B are diagrams illustrating a case where multi-pass printing (two-pass printing) is performed. FIG. 18A is a schematic diagram illustrating an ejection state of ink droplets ejected from the recording head, and FIG. ) Is a schematic diagram showing an image in which droplet density unevenness is obtained by ejecting ink droplets, and FIG. 8C is a diagram showing the density distribution of the image shown in FIG.

  FIG. 19 is a diagram showing an image formed by multi-pass printing (two-pass printing). (A) shows an image formed in the first pass, and (b) shows an image formed in the second pass. , (C) respectively show images formed in the third pass.

  FIG. 20 is a schematic diagram of a random mask pattern in which concentrated pixel groups are arranged.

  FIG. 21 is a plan view schematically showing the recording head of the present invention.

  22A and 22B are diagrams showing random mask patterns, where FIG. 22A shows a case where a uniform recording duty is set in each pass, and FIG. 22B shows a case where a different recording duty is set for each pass. .

  The characteristic configuration of the present invention will be described below.

  In the recorded image, the change in color that occurs in each pass is seen by the pitch of the paper feed width for each pass (hereinafter referred to as banding), in addition to the difference in dot placement order between forward and backward movements. It is clear that the resulting density unevenness is caused by visual recognition. Therefore, in the first embodiment, in order to further reduce the density unevenness, the print duty in each pass is divided. FIGS. 13B and 14 show the case where the recording duty of each pass area is divided into two, and FIGS. 15A and 15B show normal areas where the divided areas e1 and e2 are formed with a uniform duty. An image recorded by multi-pass and an image formed by the two-divided duty are compared and shown. In FIG. 14, the print area of the head is divided into first to fourth print areas, and recording is performed by applying the random mask pattern as described in FIG.

  Here, in the image formed with the uniform duty shown in FIG. 15A, for example, when a uniform solid pattern is recorded, banding occurs at the paper feed pitch. The existence of the image is recognized, and the image quality is deteriorated. However, in this embodiment, banding occurs at half the paper feed pitch, so that the banding occurrence pitch falls within the perceived pitch in terms of visual characteristics and does not feel image quality degradation.

  According to the experiment by the present inventor, it has been confirmed that, with a pitch of 338 μm, density unevenness (banding) due to an implantation order difference or the like is hardly visually recognized. However, no significant effect was seen even if the number of divisions was increased further. As for the number of divisions, for example, in the case of 4-pass printing, when each pass area is divided into 4 parts, the effect of reducing the image deterioration appears significantly.

  As described above, when a certain area E is recorded in multi-pass recording, it can be said that it is more preferable for reciprocal recording to subdivide the recording duty setting area with a smaller number of passes.

  However, when the recording duty is set to be partially increased depending on the area as described above, the temperature rise of the recording head cannot be avoided. When the temperature of the recording head rises, the volume of ink droplets that are ejected tends to increase, and different inks mix with each other on the recording medium, which sometimes degrades image quality called beading.

  Therefore, in the present invention, when it is determined that the temperature of the print head or the value of the temperature rise is equal to or higher than a predetermined value, the mask pattern is selected so as to increase the thinning rate of the divided areas having a relatively high print duty. I tried to suppress the ding. This recording duty can be used to select and set the optimum values for the number of multi-passes and the number of divisions according to various media characteristics (absorbance, blurring, etc.). It may be stored in a table and read appropriately according to the above conditions.

  Moreover, one form in which the present invention is effectively used is a form in which bubbles are formed by causing film boiling in a liquid using thermal energy generated by an electrothermal transducer.

1 is a perspective view showing a schematic structure of an embodiment in which an image forming apparatus according to the present invention is applied to an ink jet printer. It is a perspective view showing the appearance of one example which applied the head cartridge by the present invention to the ink-jet printer shown in Drawing 1 in an exploded state. FIG. 3 is a perspective view of a print head portion in the head cartridge shown in FIG. 2. FIG. 4 is a cutaway perspective view illustrating a schematic structure of a main part of the print head illustrated in FIG. 3. It is a fracture | rupture top view showing the arrangement | sequence state of the discharge port of a liquid discharge head and an electrothermal conversion body. It is AA 'sectional drawing in FIG. It is a flowchart which shows operation | movement of embodiment of this invention. It is a block diagram which shows the image process part in the Example of this invention. FIG. 5 is an explanatory diagram illustrating a multi-pass printing operation and a mechanism of density unevenness due to a dot printing order difference. FIG. 4 is an explanatory longitudinal sectional side view showing a mechanism of ink permeation into a recording medium. It is a diagram which shows the surface coverage calculated for every pass in the case of 4 pass recording. It is a figure which shows recording duty in each pass in 4 pass recording. It is a figure which shows the recording duty in each pass. It is a schematic diagram of an image formed in 4-pass printing. It is a schematic diagram of an image formed in 4-pass printing. It is a figure explaining multipass recording. It is a figure explaining multipass recording. It is a figure explaining multipass recording. It is a figure explaining multipass recording. It is a schematic diagram of the random mask pattern which arranged the concentrated pixel group. FIG. 2 is a plan view schematically showing a recording head of the present invention. It is a figure which shows a random mask pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 18 Head cartridge 19 Print head 21 Tank holder 24 Ink tank 25 Ejection port 27 Print element board 28 Ink supply port 29 Electrothermal conversion body 30 Electrode terminal 31 Common ink chamber 33 Ink path 34 Partition wall 35 Ejection port surface 36 Electric wiring board

Claims (6)

Using a recording head in which a plurality of nozzle groups consisting of a plurality of nozzles are arranged, main scanning is performed a plurality of times by forward and backward movements of different nozzle groups with respect to the same main recording scanning area on a predetermined recording medium. In an ink jet recording apparatus that forms a thinned image according to a thinning mask pattern by scanning and completes the image,
Means for measuring the temperature or temperature rise of the recording head;
Means for determining whether a measurement value by the measurement means is a predetermined value or more;
Means for storing a plurality of types of the thinning mask patterns in which the same recording scanning area is divided at a predetermined pitch and the recording duty is set to a different value for each divided area;
An ink jet recording apparatus, wherein a mask pattern to be used is different depending on a temperature of the recording head or a temperature rise.   Of the same area formed by each main scanning, the recording duty of the divided areas located at both ends is set to a value lower than the recording duty of the divided area located at the inner central part thereof. The ink jet recording apparatus according to claim 1.   The mask pattern is selected so as to increase the thinning-out rate of the divided areas having a relatively high recording duty when the determination means determines that the temperature of the recording head or the value of the temperature increase is equal to or greater than a predetermined value. The ink jet recording apparatus according to claim 1 or 2.   The recording head is a recording head that discharges ink using thermal energy, and is an ink jet recording head that includes a thermal energy converter for generating thermal energy applied to the ink. 5. The image forming apparatus according to 1 or 4.   8. The ink jet according to claim 1, wherein the recording head is provided with a nozzle row corresponding to a plurality of colors of ink, and ejects ink to form a color image based on color recording data. Recording device.   9. The ink jet recording apparatus according to claim 1, wherein the recording head has an amount of recording liquid ejected from each nozzle by one ejection operation of 10 pl or less.

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