JP2014012381A - Ink jet recorder and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder which reduces color shading due to a difference of ink ejection order, and a recording method.SOLUTION: An ink jet recorder distributes recording data for each of a plurality of scans so that a dot formed position at which ink is ejected is the same for all dots which are formed by each color ink in the same scan. Thereby, based on the distributed recording data, recording is controlled.

Description

  The present invention relates to an ink jet recording apparatus that performs recording by ejecting ink onto a recording medium, and a recording method using the ink jet recording apparatus.

  An inkjet recording apparatus that forms an image on a recording medium by discharging minute ink droplets from a recording head is capable of high-density and high-speed recording, and can easily perform recording on various recording media. It is used for various image forming applications.

  In recording by an ink jet recording apparatus, it is difficult to form an image with high definition on a recording medium having low solvent absorbability such as printing coated paper. The reason for this is that a recording medium with low solvent absorption performance, such as printing coated paper, is slow in fixing ink droplets applied to the recording medium, and adjacent ink droplets are mixed together. As a result, there is a bleed in which ink droplets are spread and mixed at the boundary between adjacent different inks, or the density of the solid region is non-uniform because the same ink droplets are mixed and the ink fixing position deviates from the landing position. Unevenness (beading) may occur. Therefore, there is a possibility that the image quality of the recorded image is deteriorated.

  In particular, when recording is performed using pigment ink, it is known that the solvent component in the ink penetrates into the recording medium or evaporates, but the pigment remains on the surface of the recording medium. Further, when applying a plurality of colors of ink in one recording scan of the recording head, it is known that a pigment color material layer is formed on the surface of the recording medium in the order of ink application. Therefore, when recording is performed in both forward scanning and backward scanning while reciprocating the recording head, the order of ink application during the forward scanning of the recording head is different from the order of ink application during the backward scanning. The ink order of the pigment color material layer is also different. As a result, a difference occurs in the color developability of the recorded image, color unevenness occurs in the recorded image, and image quality in the recorded image may be deteriorated.

  As a technique for performing such high-quality recording by reducing such color unevenness, recording is performed so that the same number of dots of ink ejected from combinations of ejection port arrays having different application orders exist in the pixel or in the entire image. A method of performing this is disclosed in Patent Document 1. In Patent Document 1, there is provided a recording apparatus in which ejection port arrays for ejecting ink of each color are arranged in contrast, and ink can be ejected in the same ink order during both forward and backward recording scans. Used and recorded. Then, recording is performed so that the number of dots printed in the first ink application order and the number of dots printed in the second ink application order are the same in the pixel or in the entire image. Has been done. It is described that by performing recording in this manner, it is possible to reduce color unevenness caused by different ink application orders.

JP-A-2005-001336

  However, in the method described in Patent Document 1, the size of the recording head is increased and the size of the recording apparatus is also increased by arranging the ejection port arrays for ejecting ink of each color in contrast. In a printing apparatus that performs multi-pass printing, dots are not formed in the pixel or in the entire image depending on the application order of the first ink and the application order of the second ink, which are not arranged in contrast. Recording can be performed so that the same number exists. However, even when recording is performed with such a configuration, when ink is applied according to the application order of the first ink and then ink is applied according to the application order of the second ink, dots according to the respective application order There is a difference in fixing time between the two. For this reason, a difference in color developability occurs between the dots that are printed according to the respective application orders, and as a result, uneven color due to the different ink application order occurs.

  Therefore, in view of the above circumstances, an object of the present invention is to provide an ink jet recording apparatus and a recording method in which uneven color caused by different ink application orders is reduced.

  The present invention has a carriage on which a recording head capable of discharging a plurality of colors of ink can be mounted, and performs recording by discharging ink from the recording head to a recording medium while scanning the carriage. An ink jet recording apparatus that forms a recording image based on recording data by scanning the carriage a plurality of times with respect to a predetermined recording area of a recording medium. Is controlled by distributing the recording data for each of a plurality of scans performed to form a recorded image so that the positions of the dots formed by the inks of the respective colors are the same. It has the control means to do.

  According to the present invention, ink can be applied so that different inks are mixed before the ink is absorbed by the recording medium. Therefore, since the inks are mixed on the recording medium regardless of the ink application order, the occurrence of reciprocal unevenness due to the ink application order can be suppressed, and a high-quality image can be obtained.

1 is a perspective view schematically showing an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view showing a surface on which a discharge port is formed in a recording head mounted on the ink jet recording apparatus of FIG. 1. FIG. 2 is a block diagram illustrating a schematic configuration of a control system in the inkjet recording apparatus of FIG. 1 and a host apparatus connected to the inkjet recording apparatus. 3 is a flowchart illustrating a control flow when recording is performed by the ink jet recording apparatus of FIG. 1. FIG. 3 is a mask showing recording data at positions where dots are formed for each scan when ink is recorded by the ink jet recording apparatus of FIG. 1. FIG. It is the flowchart shown about the control flow at the time of recording by the inkjet recording device which concerns on 2nd embodiment of this invention. FIG. 7 is a mask showing recording data at positions where dots are formed when background data is adjacent to character / line drawing data in recording according to the flow of FIG. 6.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view schematically showing a main part of the ink jet recording apparatus 200 according to the first embodiment of the present invention. The ink jet recording apparatus 200 of the present embodiment is a serial scan method, and a carriage (not shown) reciprocates in the main scanning direction along the guide shaft 8. A recording head 5 and an ink tank 6 for supplying ink to the recording head 5 are mounted on the carriage. As described above, the ink jet recording apparatus of this embodiment has a carriage on which the recording head 5 can be mounted.

  The recording head 5 records an image by ejecting ink to the recording medium 1 from a plurality of arranged ejection openings. The recording head 5 includes four recording heads 5K, 5C, 5M, and 5Y that respectively eject black (K), cyan (C), magenta (M), and yellow (Y) color inks. The recording heads 5K, 5C, 5M, and 5Y each have 1280 ejection ports (also referred to as nozzles) arranged at a density of 1200 dpi, and the amount of ink ejected from each ejection port at a time is about 4 ng. . In the present embodiment, four recording heads 5 that eject inks of different colors are arranged. The number of recording heads is not limited to four, and may be three or less, or five or more, depending on the number of ink colors that can be ejected. One recording head capable of ejecting a plurality of colors of ink may be disposed in the ink jet recording apparatus. A plurality of different color inks may be ejected from the recording head.

  The ink tank 6 stores ink for supplying ink corresponding to each of the recording heads 5K, 5C, 5M, and 5Y, and includes four ink tanks 6K, 6C, 6M, and 6Y. The recording head and the ink tank constitute a head cartridge that can be integrated or separable, and the head cartridge is detachably mounted on the carriage. The recording head 5 and the ink tank 6 may be separately mounted on the carriage without constituting a head cartridge. The carriage on which the recording head 5 is mounted is moved in the main scanning direction (arrow X direction in the figure) by the carriage motor 2 via the belt 4. The recording medium 1 is transported by the transport roller 3 in the sub-scanning direction (in the direction of arrow Y in the figure) that intersects the main scanning direction (in the present example, orthogonal). The ink jet recording apparatus forms an image on the recording medium 1 by repeating recording scanning for ejecting ink from the recording head 5 and moving the recording medium 1 while moving the carriage. In particular, the ink jet recording apparatus 200 of the present embodiment performs so-called multi-pass recording in which an image is formed by performing a plurality of recording scans on a predetermined area of a recording medium.

  The cap 7 caps the ejection port surface on which the ejection ports of the four recording heads are formed, and includes four caps 7K, 7C, 7M, and 7Y. The carriage on which the recording head 5 and the ink tank 6 are mounted returns to the home position with the cap 7 when recording is not performed. In addition, when a predetermined time has elapsed after the carriage waits at the home position, the ejection port of the recording head 5 is not dried so that the ejection port surface of the recording head 5 does not dry or the ink is evaporated from the ejection port. A capping operation for bringing the cap 7 into contact with the formed surface is performed.

  FIG. 2 is a view as seen from the ejection port surface of the recording head 5 applicable to the present embodiment.

  The recording head 5 used in the present embodiment has one ejection port array for ejecting ink of each color. For example, the center of the ejection port of the recording head 5K that ejects black ink and the recording that ejects cyan ink. The discharge port center of the head 5C is 3.5 mm apart. Similarly, with respect to recording heads that discharge other colors, the discharge port centers of adjacent recording heads are 3.5 mm apart. That is, the ejection port center of the recording head 5k that ejects black ink and the ejection port center of the recording head 5Y that ejects yellow ink are 3.5 × 3 = 10.5 mm apart.

  FIG. 3 is a block diagram showing the configuration of the recording system of this embodiment.

  The recording system of FIG. 3 is a system that includes a host device 100 and an inkjet recording device 200. The host device 100 can be a personal computer or a digital camera having a function as an information processing device, and is a device connected to the ink jet recording apparatus (printer) 200. The host device 100 includes a CPU 10, a memory 11, an external storage unit 13, an input unit 12 such as a keyboard and a mouse, and an interface 14 for communicating with the printer 200. A user can create image data to be output from the inkjet recording apparatus 200 by executing a program (application) stored in the memory 11. The CPU 10 executes various processes in accordance with a program stored in the memory 11 and executes image processing such as color processing and quantization processing on image data created or photographed by the user. The recording data subjected to the image processing is transmitted to the ink jet recording apparatus 200 connected via the interface.

  The inkjet recording apparatus 200 includes a control unit 20 that includes a CPU 20a such as a microprocessor, a RAM 20b that is used as a work area for the CPU 20a, and stores various data such as recording data and registration adjustment values. The control unit 20 also includes a ROM 20c that stores a control program for the CPU 20a and various data. Further, the inkjet recording apparatus 200 includes an interface 21, an operation panel 22, and drivers 27 and 28. The driver 27 controls driving of the motor 23 for driving the carriage, the motor 24 for driving the paper feed roller, the motor 25 for driving the first transport roller pair, and the motor 26 for driving the second transport roller pair, and the driver 28 controls the drive of the recording head 5. The recording data transmitted from the host apparatus 100 and received via the interface 21 of the inkjet recording apparatus 200 is stored in the RAM 20 b of the control unit 20. In accordance with the recording data stored in the RAM 20b, the control unit 20 outputs ON and OFF signals for driving the motors 23 to 26 to the driver 27, and discharge signals and the like to the driver 28, respectively. Form.

Next, the ink applied in this embodiment will be described. In the following description, “part” and “%” are based on mass unless otherwise specified. The remaining part means that the ink is adjusted with ion-exchanged water so that the total amount of ink becomes 100 parts.
[Preparation of each color ink]
First, as described below, black (Bk), cyan (C), magenta (M), and yellow (Y) inks each containing a pigment were prepared.

(Preparation of ink Bk)
First, an anionic polymer P-1 [styrene / butyl acrylate / acrylic acid copolymer (polymerization ratio (weight ratio) = 30/40/30) acid value 202, weight average molecular weight 6,500, potassium hydroxide aqueous solution Neutralize with and dilute with ion exchange water to make a homogeneous 10% aqueous polymer solution. Next, 600 g of this polymer solution, 100 g of carbon black, and 300 g of ion-exchanged water are mixed and mechanically stirred for a predetermined time, and then a non-dispersed material containing coarse particles is removed by a centrifugal separation process to obtain a black dispersion. . The resulting black dispersion had a pigment concentration of 10% and a polymer concentration of 6%.

The black dispersion obtained by the above method is used, and the following components are added to obtain a predetermined concentration. Then, these components were sufficiently mixed and stirred, and then pressure-filtered with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm to prepare an ink containing a pigment. The ink Bk produced here is adjusted to have a pigment concentration of 3%. Moreover, the surface tension at this time was 21 mN / m.
-Black dispersion 30.0 parts-Glycerol 15.0 parts-Polyethylene glycol 1000 (molecular weight 1000) 1.5 parts-Acetylene glycol EO adduct (manufactured by Kawaken Fine Chemical Co., Ltd.) 0.5 parts-Zonyl FSO-100 (DuPont fluorosurfactant) 0.5 part, balance of ion-exchanged water

(Preparation of ink C)
First, using benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer having an acid value of 250 and a number average molecular weight of 3000 is prepared by a conventional method, neutralized with an aqueous potassium hydroxide solution, and diluted with ion-exchanged water to obtain a homogeneous 50 % Polymer aqueous solution was prepared. Next, 200 g of this polymer solution, C.I. I. 100 g of Pigment Blue 15: 3 and 700 g of ion-exchanged water are mixed and mechanically stirred for a predetermined time, and then a non-dispersed material including coarse particles is removed by a centrifugal separation process to obtain a cyan dispersion. The resulting cyan dispersion had a pigment concentration of 10% and a polymer concentration of 10%.

The cyan dispersion liquid obtained by the above method is used, and the following components are added thereto to obtain a predetermined concentration. Then, these components were sufficiently mixed and stirred, and then pressure-filtered with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm to prepare an ink containing a pigment. The ink C produced here is adjusted so that the pigment concentration is 3%. Moreover, the surface tension at this time was 21 mN / m.
-30.0 parts of the above cyan dispersion-15.0 parts of glycerin-1.5 parts of polyethylene glycol 1000 (molecular weight 1000)-0.5 part of acetylene glycol EO adduct (manufactured by Kawaken Fine Chemical Co., Ltd.)-Zonyl FSO-100 (DuPont fluorosurfactant) 0.5 part, balance of ion-exchanged water

(Preparation of ink M)
C. used in the preparation of ink C. I. Pigment Blue 15 is C.I. I. Ink M was prepared in place of Pigment Red 7 so that the pigment concentration would be 4%. Except for the type and concentration of the pigment to be used, the same adjustment as in ink C was performed. The surface tension at this time was 22 mN / m.

(Preparation of ink Y)
The carbon black used in preparing the ink Bk was C.I. I. Ink Y was adjusted so that the pigment concentration would be 4% instead of Pigment Yellow 74. Except for the type and concentration of the pigment to be used, the same adjustment as in the ink Bk was performed. The surface tension at this time was 21 mN / m.

(Other ingredients)
In addition to the above-mentioned pigment color materials, various aqueous organic solvents may be used in order to develop ink jet suitability of the ink. Specific examples of the aqueous organic solvent are shown below.

  Alkyl alcohols having 1 to 6 carbon atoms such as methanol, ethanol, propanol, propanediol, butanol, butanediol, pentanol, pentanediol, hexanol and hexanediol. Alkylene glycols having an alkylene group having 2 to 6 carbon atoms, such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol; Polyhydric alcohols such as glycerin and trimethylolpropane. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol. N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Urea and urea derivatives. Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether. Lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate. Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane.

  The content of the aqueous organic solvent in the ink is 3% to 50% based on the total amount of the ink. Among the above-mentioned aqueous organic solvents, if the content of high-boiling solvents such as polyhydric alcohols decreases, the fixing property due to drying of the ink will increase, causing problems such as clogging at the ejection port of the recording head, and stable use It becomes difficult to do. Further, when the amount of the water-based organic solvent is increased, problems such as an increase in ink viscosity and an ejection failure from the nozzles occur, and a recorded image is slow to dry and handleability of a recorded matter is deteriorated. The aqueous organic solvent to be used must be appropriately selected in consideration of these various characteristics.

  Along with the above aqueous organic solvent, as other components, in the ink, there are surfactant, aqueous resin, pH adjuster, antifoaming agent, rust preventive, antiseptic, antifungal agent, antioxidant, anti-reducing agent and Various additives such as an evaporation accelerator are included as necessary. Among these, the surfactant greatly affects the surface tension of the ink, and thus becomes an important material component for the ink used in the recording medium having a low solvent absorbability, which is the subject of the present invention. Ink with a high surface tension is difficult to spread on the surface of the recording medium, so that the ink overflows more remarkably on the recording medium with low absorption performance. When the surface tension is 35 (mN / m) or more as an ink used for a recording medium having low absorption performance such as printing coated paper, image formation is extremely difficult due to overflow. The preferred surface tension of the ink used in the present invention is 30 (mN / m) or less, more preferably 25 (mN / m) or less.

  As the surfactant to be used, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant and the like can be used. However, it is important to use the pigment ink in accordance with the ionicity of the pigment ink from the viewpoint of stability problems such as dispersion destruction and thickening of the pigment ink. Specifically, hydrocarbon surfactants such as acetylene glycol surfactants, silicone surfactants such as polyether-modified dimethylsiloxane, fluorine-based surfactants such as polyether-modified fluoroalkyl, and the like are used. In order to adjust the surface tension to 25 (mN / m) or less, silicone surfactants and fluorine surfactants are particularly preferable.

  Furthermore, an image recorded with pigment ink may peel off the pigment component on the recording medium by touching or rubbing an object, or the image may be damaged by movement, or the pigment component may touch the touched object. May stick. The fact that the image quality is likely to deteriorate due to such objects touching or rubbing is said to be poor in fastness or low in scratching. It is known that the fretting property is improved by adding a resin to such a low rubbing ink. For example, an acrylic silicone copolymer which is a transparent resin obtained by copolymerizing a commercially available polydimethylsiloxane component can be used. When a resin obtained by copolymerizing this polydimethylsiloxane component is used, even if an external force is applied to the image on the recording medium by a nail or the like, slipping occurs and the dynamic friction coefficient can be efficiently reduced. Therefore, the image is less likely to be scratched, and the scratching property can be improved. The resin for improving the scratch resistance is not limited to a transparent resin copolymerized with a polydimethylsiloxane component, and other resins may be used as long as they can improve the scratch resistance of recorded images. good.

  Here, a print coated paper, which is one of recording media with low solvent absorption performance, will be described. In the printing coated paper, a surface coating layer of several to several tens of microns is formed on the surface of a base paper mainly composed of pulp in order to improve the surface property of a recorded image and the fixing performance of printing ink. The surface coating layer is mainly composed of an inorganic pigment such as calcium carbonate or kaolin and a resin binder component for binding them. Since inorganic particles such as calcium carbonate and kaolin have pores, they have the property of absorbing the solvent component, but because the pore volume of the inorganic particles used is small compared to the ink receiving layer used in inkjet paper. The solvent absorption performance is not sufficient. As a result, when ink jet ink having a large amount of solvent component is applied to the recording medium in the same manner as recording on the ink jet recording medium, the ink overflows on the surface of the recording medium due to the solvent that is not absorbed by the recording medium. In this case, the density of the solid area becomes non-uniform, resulting in uneven density (beading) in the image, or in the boundary area where different inks are adjacent, the inks are mixed and bleeding occurs.

  As a method for evaluating the ink (solvent) absorption characteristics of the recording medium, the JAPAN TAPPI paper pulp test method No. 1 was used. 51, “Bristow method” described in “Method for testing liquid absorbency of paper and paperboard”. A detailed description is omitted because it is described in many commercial books, but the outline is as follows.

  A certain amount of ink (solvent) is poured into a holding container having an opening slit of a predetermined size, and is brought into contact with a recording medium processed into a strip shape and wound around a disk through the slit. Then, the disk is rotated while the position of the holding container is fixed, and the area (length) of the ink band transferred to the recording medium is measured. A transfer amount (ml / m 2) per unit area can be calculated from the area of the ink band, and this transfer amount (ml / m 2) indicates the ink capacity absorbed by the recording medium in a predetermined time. Here, the predetermined time is defined as a transition time. The transition time (millisecond ^ 1/2) corresponds to the contact time between the slit and the recording medium, and is converted from the speed of the disk and the width of the aperture slit.

  The transfer amount with respect to water-based ink was measured by Bristow's method for general printing coated paper. As a result, in the case of printing coated paper, the transfer amount at a transfer time of 1 second is smaller than 20 (ml / m 2), and in particular, 10 (for OK top coat + (made by Oji Paper Co., Ltd., basis weight 157.0 g / m 2)). A value slightly smaller than ml / m2) was obtained. It can be said that the recording method according to the present embodiment is more suitable for a recording medium having a low solvent absorption characteristic such as the printed coated paper. However, in many cases, the amount of transfer by the Bristow method of the ink jet paper is 30 (ml / m 2) or more, but some ink jet paper has a transfer amount lower than 20 (ml / m 2). For such a recording medium, although it is an inkjet paper, it can be said that the recording medium has a low solvent absorption characteristic. That is, it is considered that the present invention can be used for a general recording medium as long as the recording medium has low solvent absorption characteristics as well as printing coated paper. Accordingly, it is preferable that the present invention is applied when recording is performed on a recording medium having an ink transfer amount by ink of the Bristow method smaller than 20 ml / m 2 other than the printing coated paper.

  Further, as another method for evaluating the ink (solvent) absorption characteristics with respect to the recording medium, there is a method in which the droplet is actually landed on the recording medium and observed until the droplet is absorbed. For example, by using an automatic minimum contact angle meter (MCA series) manufactured by Kyowa Interface Chemical Co., Ltd., it is possible to impart a capacity close to that of ink droplets during actual recording to the recording medium. It is possible to measure the time from absorption to fixing. This automatic minimum contact angle meter can observe the landing surface of a recording medium and a droplet from the side when the droplet is ejected from the piezo head onto the recording medium. Furthermore, when the landing surface of the droplet is observed from the side, it is possible to observe the time from when the droplet diameter and contact angle change over time until the droplet is absorbed by the recording medium or evaporated into the air. .

  The result of observing the permeation time of the ink with this automatic minimum contact angle meter using the ink Bk shown in the present embodiment is shown below. In addition, as a recording medium, inkjet glossy paper is used as a recording medium suitable for inkjet, printing coated paper is used as a recording medium with low solvent absorption characteristics, and polyethylene sheet is used as a non-absorbing recording medium without solvent absorption characteristics. Three types were used. The time elapsed from when the droplets landed on the recording medium until they disappeared when approximately 7 pL of droplets were ejected onto each recording medium was measured as the ink penetration time. It was observed that ink droplets disappeared at 60 msec on glossy inkjet paper, disappeared at 380 msec on printed coated paper, and disappeared at 450 msec on polyethylene sheets. Since the polyethylene sheet is a recording medium that does not absorb the solvent, the disappearance of the ink droplets in 450 msec is considered to be due to the evaporation of the water in the ink droplets. In the glossy paper for inkjet, it is considered that the ink droplets are almost permeated before evaporating. Print coated paper takes longer to penetrate the ink droplets than the fast-penetrating inkjet glossy paper and faster than the non-penetrable polyethylene sheet. It is done. In the present embodiment, a recording medium with a low solvent absorption characteristic is defined as a time slower than 250 msec until the liquid droplet disappears by the automatic minimum contact angle meter.

  FIG. 4 shows a flowchart of the control flow during recording in the present embodiment.

  First, when a user issues an image data recording instruction from a program (application) of the host apparatus 100, a printer driver installed in the memory 11 of the host apparatus 100 acquires image data to be recorded. Examples of the image data include data created or acquired by a user using a program (application) of the host device 100, image data captured or acquired by an external device such as a Web screen displayed via a network, or a digital camera. and so on. Next, when the image data is RGB multi-value data generated in the RGB color space, the printer driver performs image processing for conversion into CMYK binary data corresponding to the ink used for recording (S400). Specifically, the RGB multi-value data is converted into respective multi-value data (CMYK multi-value data in the present embodiment) corresponding to the ink used for recording. Next, according to the binarization pattern stored in the memory 11 of the host device 100, the CMYK multi-value data corresponding to each ink is converted into CMYK binary data and developed into bitmap data. Then, the host apparatus 100 sends the CMYK binary bitmap data to the inkjet recording apparatus 200.

  The inkjet recording apparatus 200 stores the CMYK binary bitmap data received from the host apparatus 100 in the RAM 20b. Next, the CPU 20a analyzes the data with a CMYK binary bitmap stored in the RAM 20b. In the present embodiment, the inkjet recording apparatus 200 forms a recorded image based on recording data by causing a carriage to scan a predetermined recording area of a recording medium a plurality of times and ejecting ink. Therefore, the bitmap data is analyzed for each scan. In the data analysis, the CMYK bitmap data is calculated for each predetermined area, and the total ink application amount is calculated to determine whether the total ink amount exceeds 50% recording duty. Thereby, it is determined whether or not the round-trip unevenness occurs in the analyzed region (S410). In the print coated paper used in the present embodiment, when the recording duty obtained from the total ink application amount exceeds 50%, there is a possibility that the color developability is different due to the difference in the ink application order and uneven reciprocation occurs. In S410, it is determined whether or not the recording duty calculated from the total ink application amount of the bitmap data exceeds 50% for each predetermined area.

  Here, the recording duty is a ratio of dots per unit area by ink droplets in a predetermined recording area. When ink is applied a plurality of times at the same location, the recording duty at that portion may exceed 100%.

  When the recording duty obtained from the total ink application amount for each predetermined area exceeds 50%, it is determined that the area is a region where reciprocal unevenness can occur. On the other hand, if the recording duty obtained from the total ink application amount does not exceed 50%, it is determined that the region is a region where no round-trip unevenness occurs. Therefore, in that case, a normal mask is selected (S430). Here, it is determined whether or not the area where reciprocal unevenness can occur is determined by whether or not the recording duty obtained from the total ink application amount for each predetermined area exceeds 50%. However, the threshold value of the recording duty used for this determination can be changed according to the absorption characteristics of the recording medium and the degree of occurrence of reciprocal unevenness. It is preferable to set the threshold higher for recording media with higher solvent absorption characteristics, and to set the threshold lower for recording media with lower solvent absorption characteristics. Further, the predetermined area is a pixel group composed of a plurality of pixels, and a 2 × 2 pixel may be used as the small pixel group. By reducing the size of the predetermined area, the present invention can be applied to a complex image. Further, by increasing the size of the predetermined area, the load required for processing can be reduced, the recording speed can be improved, and the recording efficiency can be increased. The size of the predetermined area may be changed according to the image quality and the recording speed.

  Next, when it is determined in S410 that the corresponding region is a region where reciprocal unevenness can occur, in S420, when each of the CMYK inks is applied by a plurality of scans by the recording head, the data is distributed. A mask for reciprocal unevenness is selected as the mask. The mask will be described later.

  Next, the CMYK binary bitmap data corresponding to each CMYK ink is subjected to mask processing using the distribution mask selected in S420 and S430, thereby generating ink application data for each printing scan. (S440). The recording head 5 forms an image on the recording medium according to the ink data applied in one recording scan generated in S440 (S450).

  FIG. 5 shows a mask used for distributing image data for each scan. The mask is stored in the ROM 20c of the ink jet recording apparatus 200, and is used for distributing image data. When the print data is distributed for each print scan by the mask, the print data for each print scan is determined.

  5A to 5C are normal masks selected as masks for distributing data in S430 of FIG. FIG. 5A shows a mask for distributing data so that an image is completed by four recording scans with respect to a 4 × 4 dot pixel group. Mask for generating print data for the first print scan from the top of the 4 × 4 dot pixel group, mask for generating print data for the second print scan,... The masks for generating print data for the print scan are arranged. Black pixels indicate that ink is ejected, and when four 4 × 4 dot pixel groups are added, all pixels are set to be in a complementary relationship so that ink is ejected only once. Has been. By performing a logical product (AND) process of a part of CMYK binary data (size of 4 × 4 dots) and a mask corresponding to each printing scan (each pass), ink is applied in each printing scan. Record data can be generated. FIGS. 5B and 5C are masks for distributing data so that an image is completed by four printing scans, although the pattern is different from that in FIG. 5A. In particular, when looking at the masks for generating one recording data of each of FIGS. 5A to 5C, each of the masks of FIGS. 5A to 5C is applied with ink at different positions. It can be seen that they are arranged in such a way. For example, FIG. 5A is a mask used for ink C, FIG. 5B is a mask used for ink M and ink Y, and FIG. 5C is a mask used for ink Bk. (Or Y) K ink can be applied to different positions. In this way, by applying ink droplets to different positions as much as possible for each ink, it is possible to reduce the occurrence of beading in which adjacent ink droplets mix and bleed, and the graininess is conspicuous, resulting in a decrease in the quality of the recorded image. It is possible to suppress this.

  5D to 5F are masks for countermeasures against round-trip unevenness selected as masks for distributing data in S420 of FIG. Similarly to FIGS. 5A to 5C, FIGS. 5D to 5F are masks for distributing data to a pixel group of 4 × 4 dots so that an image is completed by four printing scans. It is. As shown in FIGS. 5D to 5F, it can be seen that FIGS. 5D to 5F are the same mask for forming dots at the same position. In this regard, the masks shown in FIGS. 5D to 5F are different from the masks shown in FIGS. 5A to 5C in which dots are formed at different positions in each mask.

  In this embodiment, when it is determined that the ink application amount in the predetermined area is large and the reciprocal unevenness occurs, the ink is applied so that different color inks overlap in the same recording scan. For example, FIG. 5D is a mask used for ink C, FIG. 5E is a mask used for ink M and ink Y, and FIG. 5F is a mask used for ink Bk. (Or Y) It is possible to apply K inks so as to overlap each other. In the case of a recording medium having a low solvent absorption characteristic, the latter ink is applied before the previous ink applied to the recording medium is absorbed in this manner, so that the ink is not absorbed by the recording medium. Ink is mixed with each other, and the mixed ink is absorbed by the recording medium. As a result, it is possible to reduce a difference in color developability caused by the order of ink application when performing reciprocal recording, that is, reciprocal unevenness.

  In the above-mentioned automatic minimum contact angle meter, it was described that the ink Bk disappeared in 380 msec on the printed coated paper, but this is the disappearance time of the ink Bk when one drop of 7 pL was applied. Actually, when ink with a printing duty of 30% was applied to the printing coated paper in one printing scan, the ink disappearance time was less than 1 second. For this reason, when inks of different colors are applied so as to overlap each other in one recording scan, other inks are applied before the previous ink permeates, and the inks are placed on the recording medium. It will be mixed. The present invention was conceived by paying attention to the fact that when ink was applied to a recording medium having a low solvent absorption characteristic such as a printing coated paper and having a low permeation rate, the ink was present as a droplet on the recording medium for a long time. Is.

  As described above, by applying the recording method of the present embodiment, when ink is applied to a recording medium having a low solvent absorption characteristic, different color inks overlap in the same recording scan in a region where the reciprocal unevenness occurs. Ink is applied to the surface. As a result, different inks are mixed before the ink is absorbed by the recording medium, and the mixed liquid is absorbed by the recording medium, so that the inks are mixed on the recording medium regardless of the order of ink application to the recording medium. Can be mixed. Therefore, it is possible to suppress the occurrence of back-and-forth unevenness due to the order of ink application. Thereby, the image quality of the recorded image can be improved.

  In FIG. 4 described above, whether or not the reciprocal unevenness occurs in the predetermined area is determined according to the recording duty obtained from the total ink application amount in the predetermined area. It does not have to be done only by. If the predetermined area is not an area recorded by applying different colors of ink but an area recorded only by single color ink, the area has a recording duty of 50% or more from the total ink application amount. However, it may be determined that the region does not cause round-trip unevenness. At this time, the normal mask of S430 may be used for the monochrome area.

  Further, in the masks of FIGS. 5D to 5F described above, the same dots are arranged in all the masks so that different color inks are applied to the same position on the recording medium. A mask that applies ink to the pixels to be used may be used. Even if the same 4 pL ink droplet is applied on the recording medium, the size of the dots formed on the recording medium differs between the recording medium having ink jetting suitability and the recording medium having low solvent absorption characteristics. The dot diameter on a recording medium suitable for inkjet is about 20 to 30 μm, but the dot diameter on a recording medium with low solvent absorption characteristics is about 40 to 50 μm, and the recording medium with lower solvent absorption characteristics is The dot diameter on the recording medium increases. Therefore, even when different inks are applied to adjacent positions on the recording medium, the inks of different colors can be sufficiently mixed, and the effects of the present invention can be obtained.

  Furthermore, in the present embodiment, the reciprocal unevenness countermeasure mask is used in a region where the recording duty obtained from the total ink application amount is 50% or more. However, in a region where the recording duty exceeds 120%, it is normal. The mask may be used. When the recording duty exceeds 120%, the amount of ink applied in one recording scan is large, so that a relatively long time is required for each ink to penetrate into the recording medium. For this reason, even if a normal mask is used without using a reciprocal unevenness mask configured to overlap different color inks, different color inks may overlap before penetrating into the recording medium. it can.

  Furthermore, the recording method of the present embodiment may be applied only when the recording medium is a medium such as print coated paper having a low solvent absorption characteristic. For example, when the type of the recording medium selected by the user on the printer driver is a recording medium having a low solvent absorbability, this can be realized by performing control so that the recording method of this embodiment is performed. When the user selects a recording medium having a high solvent absorption characteristic on the printer driver, the entire area may be recorded using a normal mask.

  Further, in the present embodiment, the host apparatus 100 generates and records the recording data in which the CMYK binary data is distributed to each recording scan until the image data is converted into CMYK binary data. did. However, a configuration may be adopted in which the recording apparatus 200 acquires RGB multi-value data and the subsequent image processing is performed by the CPU of the recording apparatus 200.

  Further, in FIG. 4 described above, a mask for reciprocal unevenness is selected in an area where it is determined that reciprocal unevenness can occur. However, such a mask is not used for all inks. Also good. For example, if the recorded image is an area formed by two colors of ink, only the two colors of ink used in the image need be changed. In addition, if there is ink that easily generates reciprocal unevenness depending on the type of ink or ink that is unlikely to occur, only the ink that easily generates reciprocal unevenness may be used. As the ink that easily generates reciprocal unevenness, it is possible to use ink that has significantly different penetration characteristics from other inks or ink that has large pigment particles. In this way, by configuring the mask to change only some of the plurality of inks, it is possible to reduce the processing load.

(Second embodiment)
Next, an ink jet recording apparatus according to a second embodiment of the present invention will be described. In the second embodiment, in addition to the recording method for reducing the back-and-forth unevenness of the first embodiment, a recording method for improving the character visibility of a character region with a background will be described.

  FIG. 6 shows a flowchart at the time of recording in the present embodiment. In the flowchart at the time of recording in FIG. 6, the same reference numerals as those in FIG. In this embodiment, the same ink set as that in the first embodiment is used.

  The ink jet recording apparatus 200 analyzes the CMYK binary data received from the host apparatus 100. There, the image data is analyzed for each predetermined area of bitmap data of each CMYK, and it is determined whether the area is an image area where round-trip unevenness can occur, a character area with a background color, or an area that is neither (S415). ). As a method of analyzing image data, there is a method of determining an attribute (object attribute) of an image in the image data. In some programs (applications) installed in the host apparatus 100, object attributes are set and stored for the generated image data (recording data) in a predetermined area. Object attributes set for image data in a predetermined area include whether the data is a character attribute such as text of a character / line drawing or an image image attribute such as a poster or a photograph. In addition, there is an attribute as a background of character / line drawing data. As described above, in the present embodiment, the attribute of the recording data is set for each predetermined area.

  In the case of image data generated by such a program (application), by acquiring this attribute information, the image area or the character area with the background color from the image characteristics for each predetermined area of the image data, It is possible to determine one of the areas that are neither. This object attribute is given when image data is generated by a program (application), and the way of assignment differs depending on the program (application). For example, object attribute information may be assigned to each predetermined area so as to indicate whether the image data of the predetermined area is image image data or character / line drawing image data (line drawing data). Here, the line drawing data includes character data and refers to recording data for recording an image composed of lines such as characters and ruled lines. Further, the image image data refers to recording data for recording an image other than characters such as a photograph. The background data refers to recording data for recording an image as a background of a line drawing. As another example of the object attribute information, the image data is divided into a character / line drawing image layer and an image image layer, and the object attribute is given to the image data from the area and the layer. Furthermore, an original object attribute may be given by the operating system based on the object attribute given by the program (application).

  In the present embodiment, image data is described as image data in a format in which object attribute information is given by dividing the image data into a character / line drawing image layer and an image image layer. In S415, if there is a portion where ink is applied in an area adjacent to the image of the character / line drawing image layer of the bitmap image data, this is an area where ink is applied around the character / line drawing, that is, a character / text with a background color. The line image area is determined (S425). In addition, in the image layer of the bitmap image data, if the area is a region where reciprocal unevenness can occur based on the recording duty obtained from the total ink application amount for each predetermined region, the reciprocal unevenness occurs in that region. It is determined that this is an image area. If the region is a region where round-trip unevenness does not occur, it is determined that the region is another region. Regarding the determination as to whether or not this round-trip unevenness occurs, the same determination criteria as in the first embodiment may be used. In the present embodiment, when both a character / line drawing image and an image image are included in a predetermined area, the area is an image image area in order to give priority to reducing the occurrence of round-trip unevenness. Judgment is made as.

  If it is determined in S415 that the character / line drawing image region has a background color, a mask for the character region is selected in the subsequent S425. If it is determined in S415 that the image area is a region where reciprocal unevenness occurs, a reciprocal unevenness countermeasure mask is selected in subsequent S420. If it is determined in S415 that there is a character / line drawing image area without a background or an image area in which round-trip unevenness does not occur, a normal mask is selected in subsequent S430. The mask shown in FIG. 5 is used as a reciprocal unevenness countermeasure mask and a normal mask, and the same processing as in the first embodiment is performed after S440.

  FIG. 7 shows a sorting mask used for sorting image data of a character / line drawing area having a background color.

  FIGS. 7A and 7B are masks selected as masks for distributing data in S425 of FIG. The portions that form the dots of each mask complement each other so that when four 4 × 4 dot pixel groups are added to the 4 × 4 dot pixel group, ink is ejected only once for all pixels. It is the same as the mask of FIG. 5 in that it is set so as to have a relationship. However, it is used in the first embodiment in that dots are formed by ejecting ink only in two recording scans out of four recording scans, and ink is not ejected in the other two recording scans. Different from the mask shown in FIG.

  FIG. 7A shows a mask used for the ink that forms the character / line drawing image out of the character / line drawing image region with the background color, and FIG. 7B shows the character / line drawing image region with the background color. Of these, the mask is used for ink forming a background adjacent to a character / line drawing image. Of the character / line drawing image area, for the character / line drawing image, the image is completed by the first two printing scans of the four printing scans, and the background area adjacent to the character / line drawing image is 4 The image is completed by the subsequent two recording scans of the recording scans. As described above, in a recording medium having a low solvent permeation characteristic, after the ink droplets applied in the previous recording scan have sufficiently penetrated and fixed in the recording medium, the background area adjacent to the character / line drawing image in the next recording scan Ink is applied to the surface. Accordingly, ink is not applied to the character / line drawing image area and the background area adjacent thereto in the same recording scan, and the ink for forming the character / line drawing image and the ink for forming the background are not mixed during recording. As a result, it is possible to obtain an image with less blur and improved character visibility.

  As described above, according to the present embodiment, by varying the method of applying ink to image data for each region, color unevenness caused by the difference in the ink application sequence in a portion where reciprocal unevenness may occur can be reduced. be able to. In the present embodiment, in the character / line drawing area, it is possible to reduce the bleeding that the ink forming the character / line drawing and the ink forming the background area adjacent to the ink mix. In the image image area, different inks are mixed before ink is absorbed by the recording medium, and the mixed liquid is absorbed by the recording medium. As a result, it is possible to obtain a high-quality image in both the character / line drawing area and the image area for a recording medium having a low solvent absorption characteristic. In addition to this, in this embodiment, it is possible to suppress the occurrence of blurring in the recorded image at the boundary between the character / line drawing area and the background thereof. Accordingly, the quality of the recorded image can be further improved when recording data including a character / line drawing area with a background.

  In the present embodiment, the image data generated by the program (application) includes an image image (a photographic image or a poster image), a character, a line drawing, and the like. Furthermore, not only image data generated by a program (application) by a user, but also data when recording from the inkjet recording apparatus 200, such as a Web screen displayed via a network or a photographic image taken by a camera, is used as image data. Be treated. The image data in this embodiment indicates image data such as photographs and paintings, and the line drawing indicates a graphics image drawn with lines such as ruled lines, figures, and CAD drawings. Yes. In the present embodiment, recording data for forming a character image and recording data for forming a line drawing image are collectively referred to as line drawing data. In addition, recording data for forming an image is referred to as image image data.

  In particular, in the character / line drawing image area, when the same color ink is used for both the character area and the background area adjacent thereto, recording to the edge portion of the character / line drawing image area and recording to the background portion adjacent thereto are performed. It is desirable to provide a recording scan between the ink and the ink. For example, in a character / line drawing image region, when the background color is yellow and the character is green, ink Y may be applied to the background region, and ink C and ink Y may be applied to the character region. In such a case, when the solvent absorption characteristics of the recording medium are particularly low, or when the ink permeability and fixability are particularly low, the same ink is used in the character area and the background area, so the character area and the background area In some cases, a beading phenomenon in which the ink is smeared may occur. In such a case, beading can be reduced by applying ink to the edge portion of the character / line drawing image region and the background portion adjacent to the edge portion with at least one recording scan. In the case of the mask shown in FIG. 7, ink may be applied to the edge portion of the character / line drawing area by the first recording scan, and ink may be applied to the adjacent background portion by the third or fourth recording scan. In this way, when a recording medium having a particularly low solvent absorption characteristic, or an ink having a particularly low permeability, or an ink having a low fixability is used, the ink permeates the previously ejected ink. This time can be secured sufficiently. For the edge processing, since a conventionally used method can be applied, description thereof is omitted here.

  Furthermore, in the present embodiment, a mask to which ink is applied at the beginning of a plurality of recording scans in FIG. 7A is applied to the character / line drawing image area, and ink is applied to the background area after FIG. 7B. Although a mask to be applied is used, the order in which the ink is applied may be reversed. For example, if the ink applied to the character / line drawing image area is easy to penetrate sideways (ink that spreads easily after landing), the background ink is applied first, and then the character / line drawing image area is applied later. The spread of the ink is smaller when the ink is applied. If ink that easily penetrates horizontally is applied first, the character / line drawing image may appear blurred and appear to be a thick font / line, resulting in a reduction in character quality. By applying the background ink that does not easily penetrate horizontally, the spread of the ink in the character / line drawing area can be suppressed, and the deterioration of the character quality can be reduced. For ink that tends to spread on the recording medium or ink that does not spread easily, measure the difference in diameter after landing and after fixing with the above-mentioned automatic minimum contact angle meter, or the dots of ink droplets actually landed on the recording medium This can be determined by measuring the diameter. In other words, it is difficult for bleeding to occur in the recorded image by applying the ink that easily penetrates the recording medium and does not easily increase the dot diameter first, and then applies the ink that does not easily penetrate the recording medium and easily increases the dot diameter. Therefore, the ink having the smaller dot diameter on the recording medium is first applied between the ink used for recording the character / line drawing data and the ink used for recording the background data adjacent to the character / line drawing data. Recording is preferably performed.

  Further, in the background area adjacent to the character / line drawing image area, color unevenness may occur due to the difference in the ink application order in an area where ink of different colors is applied. In such a case, the masks shown in FIGS. 5D to 5F may be used so that different color inks are applied to the non-edge portion of the background area in the same recording scan. By doing so, it is possible to suppress the occurrence of round-trip unevenness not only in the image area but also in the background area adjacent to the character / line drawing image area, and the image quality of the recorded image can be improved.

  In the present specification, “recording” is used not only for forming significant information such as characters and graphics but also for any case. It also represents the case where images, patterns, patterns, etc. are widely formed on a recording medium, or the recording medium is processed, regardless of whether it is manifested so that it can be perceived by human eyes. And

  The “recording device” includes a device having a printing function such as a printer, a printer multifunction device, a copying machine, and a facsimile device, and a manufacturing device that manufactures an article using an ink jet technique.

  “Recording medium” means not only paper used in general recording apparatuses but also a wide range of materials that can accept ink, such as cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. Shall.

5 Recording head 200 Inkjet recording apparatus

Claims (9)

A carriage capable of mounting a recording head capable of discharging a plurality of colors of ink;
Recording is performed by ejecting ink from the recording head to a recording medium while scanning the carriage, and by scanning the carriage a plurality of times with respect to a predetermined recording area of the recording medium. An inkjet recording apparatus for forming a recorded image,
For each of a plurality of scans performed to form a recorded image so that the positions where dots are formed by ejecting ink in the same scan are the same among the dots formed by the respective color inks. An ink jet recording apparatus comprising control means for controlling recording by distributing the recording data.   When the amount of ink applied per unit area of the recording area exceeds a predetermined threshold, the control means determines the positions where dots are formed in the same scan of the dots formed by the respective color inks. The inkjet recording apparatus according to claim 1, wherein the recording is controlled so as to be the same between the two. For the recording data on which dots are formed, there is a judging means for judging the attributes of the recording data set for each predetermined area,
The control means determines the position where the dots are formed in the same scanning with respect to the area where the recording data on which the dot formation is performed by the determination means is determined to be image image data by each color ink. The ink jet recording apparatus according to claim 1, wherein the recording is controlled so that the dots are the same among the formed dots.   The control means includes the line drawing data area and the background with respect to an area in which the recording data on which dot formation is performed is determined by the determining means to be adjacent to the line drawing data as background data as a background. 4. The ink jet recording according to claim 3, wherein recording is controlled by distributing the recording data so that dots are formed by applying ink in different scans by the recording head to and from a data area. apparatus.   The control unit first applies ink having a smaller dot diameter on the recording medium, out of ink used for recording the line drawing data and ink used for recording the background data adjacent to the line drawing data. The inkjet recording apparatus according to claim 4, wherein the recording data is distributed so as to control recording.   The control means forms dots in the same scan when recording is performed on a recording medium in which an ink transfer amount by the Bristow method for the plurality of inks in the recording medium on which recording is performed is smaller than 20 ml / m 2. 6. The ink jet recording apparatus according to claim 1, wherein the recording is controlled so that the positions are the same among the dots formed by the respective color inks.   When the recording medium on which the recording is performed is printing coated paper, the sorting unit is configured such that the positions where dots are formed in the same scanning are the same among the dots formed by the respective color inks. The inkjet recording apparatus according to claim 1, wherein recording is controlled.   8. The inkjet recording apparatus according to claim 1, wherein the control unit distributes the recording data for each of a plurality of scans using a mask to control the recording. A carriage capable of mounting a recording head capable of ejecting a plurality of colors of ink; performing recording by ejecting ink from the recording head to a recording medium while scanning the carriage; A recording method in which recording is performed using an ink jet recording apparatus that forms a recorded image based on recording data by scanning the carriage a plurality of times with respect to the recording area,
For each of a plurality of scans performed to form a recorded image so that the positions where dots are formed by ejecting ink in the same scan are the same among the dots formed by the respective color inks. And a recording step of controlling the recording by distributing the recording data.

Images