Liquid discharge apparatus and control method thereof

Abstract

To provide a liquid discharge device capable of securing a fixing time of liquid.SOLUTION: A scanning unit that reciprocally scans the liquid discharge head in a scanning direction, a transport unit that transports the recording medium in a transport direction, and a control unit that causes the scanning unit to stand by at a first standby position for a first standby time after the backward scanning of the scanning unit is completed and before the forward scanning is started, and causes the scanning unit to stand by at a second standby position for a second standby time after the forward scanning of the scanning unit is completed and before the backward scanning is started. The control means controls the second standby time to be a first value when the first standby time is the first value, and controls the second standby time to be shorter than the first standby time when the first standby time is a second value larger than the first value.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection apparatus and a control method thereof. [Background technology]

[0002] In a liquid ejection apparatus that performs printing by ejecting liquid from nozzles onto a printing medium, a carriage standby time is sometimes provided during printing operation to ensure time for the liquid applied to the printing medium to set.

[0003] Patent Document 1 discloses a recording device (liquid ejection device) that can provide a predetermined wait time (standby time) when a carriage equipped with a liquid ejection head starts a main scan (when a forward scan starts) and when it reverses (when a backward scan starts). In the liquid ejection head of Patent Document 1, the carriage waits on the HP side before starting a forward scan, and waits on the BP side before starting a backward scan. According to the liquid ejection device of Patent Document 1, a waiting time is provided for the carriage at the start of a main scan and when it reverses, ensuring time for the liquid applied to the recording medium to fix. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-65753 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, while the carriage is on standby, liquid may be preliminarily ejected to prevent the nozzle surface from drying out. However, to avoid increasing the size of the device, a maintenance mechanism capable of receiving the preliminarily ejected liquid may be provided only on the home position side (HP side) and not on the back position (BP side). In this case, in the liquid ejection device of Patent Document 1, if the carriage is placed on standby on the BP side, where preliminarily ejection is not possible, to ensure time for the liquid to set, there is a risk that the nozzle surface will dry out.

[0006] Therefore, an object of the present disclosure is to provide a liquid ejection device that can ensure a sufficient time for the liquid to set. [Means for solving the problem]

[0007] The liquid ejection device disclosed herein comprises a scanning means for scanning a liquid ejection head, which ejects liquid and performs an ejection operation, back and forth in a scanning direction; a transport means for transporting a recording medium in a transport direction intersecting the scanning direction; and a control means for causing the scanning means to wait at a first standby position for a first standby time after the scanning means has completed its backward scan and before the scanning means has started its forward scan, and for causing the scanning means to wait at a second standby position for a second standby time after the scanning means has completed its forward scan and before the scanning means has started its backward scan, wherein the control means controls the second standby time to the first value when the first standby time is a first value, and controls the second standby time to be shorter than the first standby time when the first standby time is a second value greater than the first value. [Effects of the Invention]

[0008] According to the liquid ejection device of the present disclosure, it is possible to ensure a sufficient time for the liquid to settle. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams showing an example of the appearance of a liquid ejection device that can be applied to an embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view of a liquid ejection device that can be applied to an embodiment. [Figure 3] FIG. 10 is a diagram showing an example of a nozzle surface that can be applied to an embodiment. [Figure 4] FIG. 2 is a block diagram showing an example of a schematic configuration of a control system according to an embodiment. [Figure 5] FIG. 1 is a diagram for explaining a multi-pass printing method that can be applied to an embodiment. [Figure 6] FIG. 10 is a diagram showing an example of a mask pattern. [Figure 7]FIG. 2 is a schematic diagram illustrating a case where recording is performed on an area of ​​a recording medium. [Figure 8] FIG. 10 is a diagram showing an example of a table showing the time between each path in a multipath transmission; [Figure 9] FIG. 10 is a diagram illustrating an example of a table that can be stored in a memory according to an embodiment. [Figure 10] 1 is a flowchart illustrating a process that can be applied in one embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of a table that can be stored in a memory according to an embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of a table that can be stored in a memory according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this disclosure, "recording" does not only mean forming meaningful information (for example, characters or figures that are visible to humans). "Recording" also means forming insignificant information. Furthermore, in this disclosure, "recording" broadly means forming an image, a design, a pattern, a structure, or a combination thereof on a recording medium, or processing the medium.

[0011] The term "recording medium" includes not only paper used in general recording devices, but also cloth, plastic film, metal plate, glass, ceramics, resin, wood, leather, and other materials that can accept ink. The recording medium can be anything on which an image can be formed by applying ink droplets. For example, various materials and shapes can be used, such as paper, cloth, optical disc label surfaces, plastic sheets, overhead projector sheets, and envelopes.

[0012] [First embodiment] (1) Configuration of the liquid ejection device 100 FIG. 1 is a diagram showing the appearance of a liquid ejection device 100 that can be applied to this embodiment.

[0013] 1, in this embodiment, a so-called serial scanning inkjet recording device is used as the liquid ejection device 100. The liquid ejection device 100 includes a carriage unit 101 that scans back and forth in a scanning direction (X direction), and a platen 102 that supports a recording medium P. The liquid ejection device 100 also includes an encoder 103 that detects the position of the carriage unit 101, a guide shaft 104 that supports the carriage unit 101, and a flexible wiring board 105 that is flexible.

[0014] The liquid ejection device 100 includes a UI (user interface) screen 106 that allows input and output of instructions related to printing, and a maintenance mechanism 107 that maintains the performance of the carriage unit 101. The maintenance mechanism 107 includes a cap unit that receives preliminary ejection from the liquid ejection head 205 (see FIG. 2) and caps the nozzle surface, and a suction mechanism (e.g., a pump) that forcibly sucks liquid while the nozzle surface is capped. The maintenance mechanism 107 may also include a cleaning blade that wipes off dirt from the nozzle surface.

[0015] Hereinafter, in the scanning area in the X direction that the carriage unit 101 can scan, the position where the maintenance mechanism 107 is provided will be referred to as the HP (home position) side. Also, the side farther from the maintenance mechanism 107 and where the carriage unit 101 can wait will be referred to as the BP (back position) side. The liquid ejection device 100 is provided with a take-up spool 108 that takes up the recording medium P. The recording medium P is taken up by the take-up spool 108. As a result, a roll-shaped taken-up medium 109 is formed.

[0016] FIG. 2 is a schematic cross-sectional view of a liquid ejection device 100 that can be applied to this embodiment.

[0017] 2, the liquid ejection device 100 includes a holding spool 201 that holds the recording medium P, a pair of transport rollers 202 that transport the recording medium P, a heater 203 that fixes the liquid applied to the recording medium P, and a cover 204 that covers the heater 203. The pair of transport rollers 202 includes a transport roller 202a and a pinch roller 202b. The carriage unit 101 includes a liquid ejection head 205 that ejects liquid.

[0018] In the printing operation of this embodiment, the liquid ejection head 205 scans in a scanning direction (X direction in the drawing) that intersects with the conveyance direction (-Y direction in the drawing) of the printing medium P. An image is printed by applying a liquid (e.g., ink) to the printing medium P during the scan. The printing medium P is conveyed in the -Y direction from a holding spool 201 that holds the printing medium P by a pair of conveyance rollers 202 that are driven via gears by a conveyance motor 406 (see FIG. 4). Meanwhile, at a predetermined conveyance position, a carriage unit 101 is driven by a carriage motor 408 (see FIG. 4) to perform reciprocal scanning (reciprocal movement) along a guide shaft 104 that extends in the X direction.

[0019] During this scanning process, a discharge operation is performed in which ink is discharged from the nozzles of a liquid discharge head 205 that is detachable from the carriage unit 101 at a timing based on a position signal obtained from the encoder 103 (see FIG. 1). This makes it possible to record a certain bandwidth corresponding to the range in which the nozzles are arranged. The configuration of the liquid discharge head 205 will be described later. In this embodiment, the scanning speed is 30 inches per second, and the discharge operation is performed at a recording resolution of 1200 dpi (1 / 1200 inch intervals). This type of scanning of the carriage unit 101 accompanied by the discharge operation of the liquid discharge head 205 will hereinafter be referred to simply as a "scan" in this specification. After one scan is performed, the recording medium P is transported in the -Y direction by a distance corresponding to one band, and the next bandwidth is recorded.

[0020] Thereafter, by alternately repeating the scanning and conveying operations, images are recorded on the recording medium P in sequence.

[0021] A carriage belt (not shown) is used to transmit the driving force of the carriage motor 408 to the carriage unit 101. Instead of a carriage belt, it is also possible to use other driving methods, such as a unit that includes a lead screw that is rotationally driven by the carriage motor 408 and extends in the X direction, and an engagement portion that is provided on the carriage unit 101 and engages with the groove of the lead screw.

[0022] The conveyed recording medium P is sandwiched between a pair of conveying rollers 202 and guided to a recording position on the platen 102, i.e., into the scanning area of ​​the liquid ejection head 205. Normally, in a resting state, the nozzle surface of the liquid ejection head 205 is capped at the home position. Therefore, when a recording operation starts, the cap is opened before recording, and the carriage unit 101 is made ready to scan. Thereafter, when data for one scan of the carriage unit 101 is accumulated in a buffer, the carriage motor 408 is driven to scan the carriage unit 101, and the recording operation is performed. The recording medium P on which an image has been formed by the liquid ejection head 205 is taken up by a take-up spool 108, and a roll-shaped taken-up medium 109 is formed.

[0023] A flexible wiring board 105 (see FIG. 1) is attached to the liquid ejection head 205 for supplying drive pulses for ejection operations, head temperature adjustment signals, etc. The other end of the flexible wiring board 105 is connected to a control unit 400 (see FIG. 3) that includes control circuits such as a CPU 401 (see FIG. 3) that controls the liquid ejection device 100. The UI screen 106 (see FIG. 1) is configured to allow the user to input instructions to start and stop the recording operation, and to check information about the recording medium P, etc.

[0024] The heater 203 is located downstream in the transport direction from the position where the liquid ejection head 205 attached to the carriage unit 101 scans back and forth in the scanning direction. The heater 203 is supported by a frame (not shown) and applies heat to the liquid ink applied to the recording medium P to dry it. A sheath heater, a halogen heater, or the like is used as the heater 203. The heater 203 is covered by a cover 204. The cover 204 functions to efficiently irradiate heat from the heater 203 onto the recording medium P and to protect the heater 203.

[0025] The heating temperature of the heater 203 is set taking into consideration the film-forming properties and productivity of the water-soluble resin particles and the heat resistance of the recording medium P. Examples of methods for heating the recording medium P include a method of blowing warm air from above, or a method of heating the recording medium P from below using a contact-type heat conduction heater. In this embodiment, there is one heater 203, but two or more heaters 203 may be used in combination as long as the temperature measured by a radiation thermometer (not shown) on the recording medium P does not exceed the set value of the heating temperature.

[0026] The maintenance mechanism 107 (see FIG. 1) performs suction and wiping processes on the liquid ejection head 205, as well as functions to receive ejected droplets (eg, ink droplets) when the liquid ejection head 205 performs preliminary ejection.

[0027] The recording apparatus of this embodiment performs so-called multi-pass recording, in which an image is formed in a predetermined area (an area equivalent to 1 / n band) on the recording medium P by scanning the liquid ejection head 205 multiple times (n times). Note that the above-mentioned "n" is an integer equal to or greater than 2. Multi-pass recording will be described later.

[0028] (2) Configuration of the liquid ejection head 205 FIG. 3 is a diagram showing a nozzle surface 300 of a liquid ejection head 205 that can be applied to this embodiment.

[0029] As shown in FIG. 3, the nozzle surface 300 is provided with a first nozzle row 301 that ejects black ink (K) as a liquid (ink containing a colorant). The nozzle surface 300 is provided with a second nozzle row 302 that ejects cyan ink (C) as a liquid. The nozzle surface 300 is provided with a third nozzle row 303 that ejects magenta ink (M) as a liquid. The nozzle surface 300 is provided with a fourth nozzle row 304 that ejects yellow ink (Y) as a liquid. Because these inks contain colorant, they will also be referred to as color inks or color inks in the following description.

[0030] The liquid ejection head 205 also includes a fifth nozzle row 305 that ejects a reactive liquid ink (RCT) that does not contain a colorant. The reactive liquid ink does not contain a colorant, but contains a reactive component that reacts with the colorant contained in the colorant ink, and reacts with the colorant ink upon contact with the colorant ink on the recording medium P (see FIG. 1, etc.), thereby preventing the colorant ink from bleeding and spreading. Note that the preparation of a reactive liquid ink (RCT) is not an essential requirement in the present disclosure.

[0031] 3, a first nozzle row 301, a second nozzle row 302, a third nozzle row 303, a fourth nozzle row 304, and a fifth nozzle row 305 are arranged on the nozzle surface 300. Each of these five nozzle rows has 1280 nozzles 306 that eject ink arranged in the Y direction (arrangement direction) at a density of 1200 dpi. In this embodiment, the amount of ink droplets ejected (ejection amount) from one nozzle 306 is approximately 4.5 pl.

[0032] These five types of nozzle rows are connected to five types of ink tanks (not shown) that store ink corresponding to each nozzle row. Ink is supplied to each of the five types of nozzle rows from each of the five types of ink tanks. The liquid ejection head 205 and the ink tank may be configured as an integrated unit, or the liquid ejection head 205 and the ink tank may be configured as separable units. Furthermore, instead of or in addition to the reaction liquid ink, each of the five types of color ink described above may contain water-soluble resin particles that form a film when heated and improve the scratch resistance of the image recorded on the recording medium P.

[0033] (3) Recording system configuration FIG. 4 is a block diagram showing a schematic configuration of a control system of the liquid ejection device 100 according to this embodiment.

[0034] 4, the control unit 400 includes a CPU 401, a ROM 402 that stores control programs to be executed by the CPU 401, a RAM 403 used as a print data buffer, and an input / output port 404. The CPU 401 performs processing operations such as calculation, selection, determination, and control, as well as a print operation. The memory 405 stores a mask pattern (described later) and a table (see FIG. 9, etc.) in which the standby time of the carriage unit 101 (see FIG. 1) is set.

[0035] A first drive circuit 407 for driving a conveyance motor 406 is connected to the input / output port 404. A second drive circuit 409 for driving a carriage motor 408 is connected to the input / output port 404. A third drive circuit 410 for driving the liquid ejection head 205 is connected to the input / output port 404. A fourth drive circuit 411 for driving the heater 203 and the actuators in the cutting unit is connected to the input / output port 404.

[0036] The control unit 400 is connected to a host device 413 via an interface circuit 412 .

[0037] (4) Multi-pass printing method In this embodiment, the five types of ink described above are used to form an image by a so-called bidirectional multi-pass printing method, which forms an image by multiple reciprocating scans (also called passes) on a predetermined area on the printing medium P. This bidirectional multi-pass printing method (hereinafter simply referred to as the multi-pass printing method) will be described below.

[0038] FIG. 5 is a diagram for explaining a multi-pass printing method that can be applied to this embodiment.

[0039] In FIG. 5, the explanation will be given assuming that ink is ejected from each of six nozzle groups A1 to A6 formed by dividing each of the five types of nozzle arrays described above in the Y direction during each of six scans of a predetermined area. In the following explanation, since there is no need to particularly distinguish between the first nozzle array 301 to the fifth nozzle array 305 (see FIG. 3), each of the five types of nozzle arrays described above will be simply referred to as nozzle array 500. In addition, in reality, the recording medium P is transported in the -Y direction while the liquid ejection head 205 is scanning. However, for convenience of explanation, FIG. 5 will be explained using a diagram in which the liquid ejection head 205 is moved in the +Y direction relative to a predetermined area 501 of the recording medium P.

[0040] First, in the first scan (first pass), the liquid ejection head 205 scans a predetermined area 501 on the recording medium P in a positional relationship where the nozzle group A1 in the nozzle array 500 faces the predetermined area 501. Then, ink is ejected from the nozzle group A1 onto the predetermined area 501 in accordance with the print data corresponding to each type of ink corresponding to the first scan. After this first pass is completed, the recording medium P is transported in the -Y direction by a distance corresponding to one nozzle group.

[0041] Thereafter, a second scan (second pass) is performed, and ink is ejected using nozzle group A2 onto the predetermined area 501. Thereafter, conveyance of the recording medium P and ejection of ink from the liquid ejection head 205 are alternately performed, and ejection from nozzle groups A3 to A6 is performed onto the predetermined area 501 during the third to sixth scans. In this way, multi-pass printing onto the predetermined area 501 is completed.

[0042] FIG. 6 is a diagram showing an example of a mask pattern 600. As shown in FIG.

[0043] 6, the blackened areas represent pixels from which ink ejection is permitted when ink ejection is determined by the quantized data. Hereinafter, the blackened pixels will also be referred to as "print-permitted pixels."

[0044] 6, the white portions represent pixels where ink ejection is not permitted even when ink ejection is determined by the quantized data. Hereinafter, the white portions are also referred to as "non-printing permitted pixels."

[0045] 6 also shows six types of mask patterns 600, each having a size of 4 pixels by 8 pixels. By repeatedly applying these six mask patterns 600 in the X direction and the Y direction, distribution processing is performed on all of the quantized data corresponding to each predetermined region.

[0046] The number of pixels present in each of the six mask patterns 600 shown in Fig. 6 is 4 pixels x 8 pixels = 32 pixels, and the total number of printable pixels in the six mask patterns 600 is 48. If the ratio of the number of printable pixels to the total number of pixels in a mask pattern 600 is called the printable rate, then the total printable rate of the mask patterns 600 shown in Fig. 6 is 150 (= 48 / 32 x 100)%.

[0047] Looking at the mask patterns 600 corresponding to each scan, five print permitted pixels are arranged in each of the mask pattern 600 corresponding to the first scan (nozzle group A1) and the mask pattern 600 corresponding to the sixth scan (nozzle group A6). Therefore, the print permitted ratios of the mask patterns 600 corresponding to the first and sixth scans are approximately 15% (= 5 / 32 × 100).

[0048] Furthermore, eight printable pixels are arranged in each of the mask patterns 600 corresponding to the second scan (nozzle group A2) and the fifth scan (nozzle group A5). Therefore, the printable ratios of the mask patterns 600 corresponding to the second and fifth scans are approximately 25% (=8 / 32×100).

[0049] The mask pattern 600 corresponding to the third scan (nozzle group A3) and the mask pattern 600 corresponding to the fourth scan (nozzle group A4) each have 11 printable pixels. Therefore, the printable ratio of the mask patterns 600 corresponding to the third and fourth scans is approximately 34% (= 11 / 32 × 100). In other words, when the mask pattern 600 shown in FIG. 6 is used, the amount of ink ejected during the third and fourth passes is the greatest among the first to sixth passes. On the other hand, the amount of ink ejected during the first and sixth passes is the least.

[0050] (5) Ink composition (Ink composition overview) The inks constituting the ink set used in this embodiment will now be described in detail. Hereinafter, "parts" and "%" are by weight unless otherwise specified.

[0051] (5-1) Composition of each ink The composition of each ink will be described in detail below.

[0052] The color inks (C, M, Y, K) and the reactive liquid ink (RCT) used in this embodiment all contain a water-soluble organic solvent. The water-soluble organic solvent preferably has a boiling point of 150°C or higher and 300°C or lower for reasons of wettability and moisture retention of the nozzle surface 300 (see FIG. 3).

[0053] Furthermore, from the viewpoint of the function of the film-forming aid for the resin particles and the swelling solubility in the recording medium P on which the resin layer is formed, the water-soluble organic solvent is particularly preferably a ketone compound, an ethylene glycol derivative, or a heterocyclic compound. Ketone compounds include, for example, acetone and cyclohexanone. Ethylene glycol derivatives include, for example, tetraethylene glycol dimethyl ether. Heterocyclic compounds have a lactam structure, such as N-methylpyrrolidone and 2-pyrrolidone.

[0054] From the viewpoint of ejection performance, the content of the water-soluble organic solvent is preferably 3 wt% or more and 30 wt% or less. Specific examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and sec-butyl alcohol. Specific examples of other water-soluble organic solvents include alkyl alcohols having 1 to 4 carbon atoms, such as tert-butyl alcohol. Specific examples of other water-soluble organic solvents include amides, such as dimethylformamide and dimethylacetamide.

[0055] Other specific examples of the water-soluble organic solvent include ketones or ketoalcohols such as acetone and diacetone alcohol. Other specific examples of the water-soluble organic solvent include ethers such as tetrahydrofuran and dioxane. Other specific examples of the water-soluble organic solvent include polyalkylene glycols such as polyethylene glycol and polypropylene glycol. Other specific examples of the water-soluble organic solvent include ethylene glycol.

[0056] Other specific examples of water-soluble organic solvents include propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, and hexylene glycol. Other specific examples of water-soluble organic solvents include alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as diethylene glycol. Other specific examples of water-soluble organic solvents include lower alkyl ether acetates, such as polyethylene glycol monomethyl ether acetate.

[0057] Other specific examples of water-soluble organic solvents include glycerin. Other specific examples of water-soluble organic solvents include ethylene glycol monomethyl (or ethyl) ether and diethylene glycol methyl (or ethyl) ether. Other specific examples of water-soluble organic solvents include lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether.

[0058] Other specific examples of the water-soluble organic solvent include polyhydric alcohols such as trimethylolpropane and trimethylolethane. Other specific examples of the water-soluble organic solvent include N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, etc. The water-soluble organic solvents described above can be used alone or as a mixture.

[0059] Furthermore, it is preferable to use deionized water as the water. The content of the water-soluble organic solvent in the reaction liquid ink (RCT) is not particularly limited. In addition to the above-mentioned components, surfactants, antifoaming agents, preservatives, antifungal agents, etc. may be added appropriately to the colorant inks (C, M, Y, K) to impart desired physical properties as needed.

[0060] Furthermore, the colorant inks (C, M, Y, K) and the reaction liquid ink (RCT) used in this embodiment all contain surfactants. The surfactant is used as a penetrant to improve the ink's permeability into the inkjet recording medium P. The greater the amount of surfactant added, the stronger the ink's surface tension lowering property, improving the ink's wettability and permeability into the recording medium P.

[0061] In this embodiment, a small amount of acetylene glycol EO adduct or the like was added as a surfactant to adjust the surface tension of each ink to 30 dyn / cm or less, and further, the difference in surface tension between the inks was adjusted to within 2 dyn / cm. More specifically, the surface tension of each ink was adjusted to approximately 22 to 24 dyn / cm. The surface tension was measured using a fully automatic surface tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.). Note that the measuring device is not limited to the above example, as long as it can measure the surface tension of the ink.

[0062] Furthermore, the pH values ​​of the inks of this embodiment are stable on the alkaline side, ranging from 8.5 to 9.5. From the viewpoint of preventing elution and performance degradation of components in the liquid ejection device 100 and the liquid ejection head 205 that come into contact with the ink, and preventing a decrease in the solubility of the dispersed resin in the ink, it is preferable that the pH value of each ink be between 7.0 and 10.0. A pH meter model F-52 (manufactured by Horiba, Ltd.) was used to measure the pH value. The measuring device is not limited to the above-mentioned example, as long as it can measure the pH value of the ink.

[0063] (5-2) Reaction solution In this embodiment, in order to suppress bleeding, beading, and the like, a reaction liquid is used to insolubilize part or all of the solid components of the color ink.

[0064] Examples of reaction solutions capable of insolubilizing dissolved dyes or dispersed pigments and resins include solutions containing polyvalent metal ions. For example, these solutions contain magnesium nitrate, magnesium chloride, aluminum sulfate, or iron chloride. As one type of flocculation using such cations, low-molecular-weight cationic polymer flocculants can be used to neutralize the charge of water-soluble resin particles and to insolubilize anionic soluble substances.

[0065] Another example of a reaction system is an insolubilization system using a reaction liquid that utilizes differences in pH values. As mentioned above, colorant inks used in inkjet recording generally tend to be stable on the alkaline side due to their nature. The specific pH value is often around 7 to 10. Taking into consideration general industrial considerations and the influence of the external environment, the pH value is often set to approximately 8.5 to 9.5. To aggregate and solidify such colorant inks, an acidic solution is added, and the pH value is changed to disrupt the stable state and aggregate the dispersed components. For this purpose, an acidic solution can also be used as a reaction liquid.

[0066] (5-3) Water-soluble resin fine particles The color ink used in this embodiment contains water-soluble resin particles. The term "water-soluble resin particles" refers to polymer particles that exist in a dispersed state in water.

[0067] Specific examples of water-soluble resin microparticles include acrylic resin microparticles synthesized by emulsion polymerization of monomers such as (meth)acrylic acid alkyl esters and (meth)acrylic acid alkylamides; and (meth)acrylic acid alkyl esters. Another specific example of water-soluble resin microparticles includes styrene-acrylic resin microparticles synthesized by emulsion polymerization of monomers such as (meth)acrylic acid alkylamides and styrene. Another specific example of water-soluble resin microparticles includes polyethylene resin microparticles, polypropylene resin microparticles, polyurethane resin microparticles, and styrene-butadiene resin microparticles.

[0068] Furthermore, core-shell type resin microparticles, in which the polymer composition of the core and shell of the resin microparticles is different, may be used as the water-soluble resin microparticles. Furthermore, in order to control the particle size, resin microparticles obtained by emulsion polymerization around pre-synthesized acrylic microparticles may be used as seed particles. Furthermore, hybrid type resin microparticles in which acrylic resin microparticles and different resin microparticles such as urethane resin microparticles are chemically bonded may be used as the water-soluble resin microparticles.

[0069] (Composition of each ink) The inks constituting the ink set used in this embodiment will now be described in detail. Hereinafter, "parts" and "%" are by weight unless otherwise specified.

[0070] 1. Black ink (1) Preparation of dispersion First, an anionic polymer P-1 [styrene / butyl acrylate / acrylic acid copolymer (weight ratio = 30 / 40 / 30), acid value 202, weight average molecular weight 6500] was prepared. This was neutralized with an aqueous potassium hydroxide solution and diluted with ion-exchanged water to prepare a homogeneous 10% by mass water-soluble resin particle dispersion.

[0071] 600 g of the polymer solution, 100 g of carbon black, and 300 g of ion-exchanged water were mixed and mechanically stirred for a predetermined time, followed by centrifugal separation to remove undispersed material, including coarse particles, to obtain a black dispersion. The resulting black dispersion had a pigment concentration of 10% by mass.

[0072] (2) Ink preparation The ink was prepared by adding the following components to the black dispersion liquid described above to a predetermined concentration: After thoroughly mixing and stirring these components, the mixture was filtered under pressure using a microfilter with a pore size of 2.5 μm (manufactured by Fujifilm Corporation) to prepare a pigment ink with a pigment concentration of 2% by mass.

[0073] 20 parts of the above black dispersion 40 parts of the above water-soluble resin particle dispersion Zonyl FSO-100 (DuPont fluorine-based surfactant) 0.05 parts 2-methyl-1,3-propanediol 15 parts 2-pyrrolidone 5 parts Acetylene glycol EO adduct (Kawaken Fine Chemicals Co., Ltd.) 0.5 parts Ion-exchanged water Remaining

[0074] 2. Cyan ink (1) Preparation of dispersion First, an AB-type block polymer with an acid value of 250 and a number-average molecular weight of 3000 was prepared using benzyl acrylate and methacrylic acid as raw materials by a conventional method. The polymer was then neutralized with an aqueous potassium hydroxide solution and diluted with ion-exchanged water to prepare a homogeneous 50% by mass water-soluble resin microparticle dispersion.

[0075] 200 g of the polymer solution, 100 g of CI Pigment Blue 15:3, and 700 g of ion-exchanged water were mixed and mechanically stirred for a predetermined time, followed by centrifugal separation to remove non-dispersed material, including coarse particles, to obtain a cyan dispersion. The resulting cyan dispersion had a pigment concentration of 10% by mass.

[0076] (2) Ink preparation The ink was prepared by adding the following components to the cyan dispersion liquid to achieve the desired concentration: After thoroughly mixing and stirring these components, the mixture was filtered under pressure using a microfilter with a pore size of 2.5 μm (manufactured by Fujifilm Corporation) to prepare a pigment ink with a pigment concentration of 2% by mass.

[0077] 20 parts of the above cyan dispersion 40 parts of the above water-soluble resin particle dispersion Zonyl FSO-100 (DuPont fluorine-based surfactant) 0.05 parts 2-methyl-1,3-propanediol 15 parts 2-pyrrolidone 5 parts Acetylene glycol EO adduct (Kawaken Fine Chemicals Co., Ltd.) 0.5 parts Ion-exchanged water Remaining

[0078] 3. Magenta ink (1) Preparation of dispersion First, an AB-type block polymer with an acid value of 300 and a number-average molecular weight of 2500 was prepared using benzyl acrylate and methacrylic acid as raw materials by conventional methods. The polymer was then neutralized with an aqueous potassium hydroxide solution and diluted with ion-exchanged water to prepare a homogeneous 50% by mass water-soluble resin microparticle dispersion.

[0079] 100 g of the polymer solution, 100 g of CI Pigment Red 122, and 800 g of ion-exchanged water were mixed and mechanically stirred for a predetermined time, followed by centrifugal separation to remove non-dispersed material including coarse particles, to obtain a magenta dispersion. The resulting magenta dispersion had a pigment concentration of 10% by mass.

[0080] (2) Ink preparation The ink was prepared by adding the following components to the magenta dispersion liquid described above to a predetermined concentration: After thoroughly mixing and stirring these components, the mixture was filtered under pressure using a microfilter with a pore size of 2.5 μm (manufactured by Fujifilm Corporation) to prepare a pigment ink with a pigment concentration of 3% by mass.

[0081] 30 parts of the above magenta dispersion 40 parts of the above water-soluble resin particle dispersion Zonyl FSO-100 (DuPont fluorine-based surfactant) 0.05 parts 2-methyl-1,3-propanediol 15 parts 2-pyrrolidone 5 parts Acetylene glycol EO adduct (Kawaken Fine Chemicals Co., Ltd.) 0.5 parts Ion-exchanged water Remaining

[0082] 4. Yellow ink (1) Preparation of dispersion First, the anionic polymer P-1 was neutralized with an aqueous potassium hydroxide solution and diluted with ion-exchanged water to prepare a homogeneous 10% by mass dispersion of water-soluble resin particles.

[0083] 300 g of the polymer solution, 100 g of CI Pigment Yellow 74, and 600 g of ion-exchanged water were mixed and mechanically stirred for a predetermined time, followed by centrifugal separation to remove undispersed material including coarse particles, to obtain a yellow dispersion. The resulting yellow dispersion had a pigment concentration of 10% by mass.

[0084] (2) Ink preparation The following components were mixed and thoroughly stirred to dissolve and disperse, and then pressure filtered through a microfilter (manufactured by Fujifilm Corporation) with a pore size of 1.0 μm to prepare a pigment ink with a pigment concentration of 4% by mass.

[0085] 40 parts of the above yellow dispersion 40 parts of the above water-soluble resin particle dispersion Zonyl FSO-100 (DuPont fluorine-based surfactant) 0.025 parts 2-methyl-1,3-propanediol 15 parts 2-pyrrolidone 5 parts Acetylene glycol EO adduct (Kawaken Fine Chemicals Co., Ltd.) 1 part Ion-exchanged water Remaining

[0086] 5. Reaction Solution In this embodiment, a reaction liquid containing a reactive component that reacts with the pigment contained in the ink and causes the pigment to aggregate or gel. Specifically, this reactive component is a component that, when mixed on a recording medium P with an ink containing a pigment stably dispersed in an aqueous medium by the action of ionic groups, can destroy the dispersion stability of the ink. In this embodiment, glutaric acid was used.

[0087] It is not necessary to use glutaric acid. Various water-soluble organic acids or polyvalent metal salts can be used as reactive components in the reaction solution. The content of the organic acid and polyvalent metal salt is preferably 0.1% by mass or more and 90.0% by mass or less, and more preferably 1.0% by mass or more and 70.0% by mass or less, based on the total mass of the composition contained in the reaction solution.

[0088] (Preparation of reaction solution) In this embodiment, as described above, glutaric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used and the following components were mixed to prepare reaction solution 1.

[0089] Glutaric acid 2 parts 2-pyrrolidone 5 parts 2-methyl-1,3-propanediol 15 parts Acetylene glycol EO adduct 0.5 parts Ion-exchanged water (manufactured by Kawaken Fine Chemicals Co., Ltd.) Remaining

[0090] (6) Recording medium P (see Figure 1, etc.) In this embodiment, a low-permeability recording medium P is used, into which moisture does not easily penetrate. A low-permeability recording medium is a medium that has no or very little moisture absorption. Therefore, if an aqueous ink that does not contain organic solvents is used, the ink is repelled, making it difficult to form an image. On the other hand, low-permeability recording media have excellent water resistance and weather resistance, making them suitable for outdoor use. Typically, a recording medium P is used that has a water contact angle of 45° or more, preferably 60° or more, at 25°C.

[0091] Low-permeability recording media include media with a plastic layer formed on the outermost surface of a substrate, media without an ink-receiving layer formed on the substrate, sheets of glass, Yupo, plastic, etc., films, banners, etc. Examples of coated plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc. These low-permeability recording media have excellent water resistance, light resistance, and abrasion resistance, and are therefore generally used when recording materials for outdoor exhibitions.

[0092] An example of a method for evaluating the permeability of a recording medium P is the Bristow method described in JAPAN TAPPI Paper and Pulp Test Method No. 51, "Test Method for Liquid Absorbency of Paper and Paperboard." In the Bristow method, a predetermined amount of ink is first poured into a holding container with a predetermined-sized opening slit, and the ink is brought into contact with a recording medium P, which has been processed into a strip and wrapped around a disk, through the slit. Then, while keeping the position of the holding container fixed, the disk is rotated, and the area (length) of the ink band transferred to the recording medium P is measured. From this ink band area, the amount of ink transferred per unit area per second (ml m-2) can be calculated. In this embodiment, a recording medium P with an ink transfer amount (water absorption amount) of less than 10 ml m-2 in 30 msec1 / 2 using the Bristow method is considered to be a low-permeability recording medium. Therefore, it may also be a non-permeable recording medium.

[0093] In this embodiment, Scotchcal Graphics Film (IJ1220-10), an adhesive vinyl chloride film manufactured by 3M, was used as the low-permeability recording medium.

[0094] (7) Recording control (7-1) Standby for recording In this embodiment, a fixing device (for example, heater 203 (see FIG. 2)) is used to dry the ink droplets ejected onto the recording medium P, thereby fixing the ink to the recording medium P. When a normal recording operation is performed, the time it takes for the recording medium P to pass through the fixing device may be shorter than the time required for the ink to dry. Therefore, in this embodiment, to ensure an appropriate time for the recording medium P to pass through an area where the thermal effect of the heater 203 can be obtained, a predetermined waiting time is provided between a certain scan of the liquid ejection head and the scan following that scan.

[0095] During the standby time, the liquid ejection head 205 (see FIG. 2) does not need to be stationary. The liquid ejection head 205 may be moved, preliminary ejection may be performed, wiping may be performed, and so on, as needed.

[0096] (7-2) Recording standby issues As described above, when a relatively long standby time is set, it is necessary to perform preliminary ejection of ink droplets as needed during the standby period to prevent the nozzle surface 300 (see FIG. 3) from drying out. However, in this embodiment, the maintenance mechanism 107 (see FIG. 1) is provided only on the HP side.

[0097] Hereinafter, the side where the maintenance mechanism 107 is located will be referred to as the HP side, and the side where the maintenance mechanism 107 is not located will be referred to as the BP side. Furthermore, scanning from the HP side toward the BP side (scanning toward the -X direction) will be referred to as "forward scanning," and scanning from the BP side toward the HP side (scanning toward the +X direction) will be referred to as "return scanning."

[0098] In this case, because preliminary ejection is possible on the HP side, any waiting time can be set. However, if the waiting time on the BP side is set arbitrarily, the nozzle surface 300 (see Figure 3) may dry out, causing ejection problems and affecting image quality. For this reason, it is necessary to set a waiting time on the BP side within a range that will prevent the nozzle surface 300 from drying out.

[0099] As described above, in this embodiment, a waiting time is provided for the ink to be fixed (dried) using the fixing device. However, the waiting time required for the ink to be fixed varies depending on the ink drying efficiency. Therefore, if a sufficient waiting time cannot be provided on the BP side, the ink may not be sufficiently fixed, which may affect the abrasion resistance of the finished printed matter.

[0100] Another possible method is to have the liquid ejection head 205 wait only on the HP side. However, this method would result in a large difference between the wait time on the HP side and the wait time on the BP side, which could lead to unevenness in the time difference.

[0101] Here, time difference unevenness will be explained using Figures 7(A), 7(B), and 8. Time difference unevenness is a phenomenon in which, during the above-mentioned multi-pass printing, the color and gloss differ between an area where the first pass is performed in the forward scan and an area where the first pass is performed in the backward scan, resulting in an appearance of unevenness. Note that time difference unevenness tends to be particularly noticeable near the end on the BP side and the end on the HP side of the printing medium P.

[0102] FIG. 7 is an explanatory diagram of time difference unevenness.

[0103] 7A is a schematic diagram of the printing operation performed on a first area 701 in which the first pass is a forward scan. In FIG. 7A, the printing area on the BP side, where time difference unevenness is likely to be noticeable, is shown as the first area 701.

[0104] In the first region 701, the first pass is recorded by a forward scan, the liquid ejection head 205 turns back at the BP end, and the second pass is recorded by a backward scan. That is, in the first region 701, the second pass of the backward scan is performed relatively soon after the first pass of the forward scan. Further thereafter, the liquid ejection head 205 turns back at the HP end, and the third pass is recorded again by a forward scan. That is, in the first region 701, the third pass of the backward scan is performed a relatively long time after the second pass of the backward scan. Thereafter, forward scans and backward scans are alternately repeated.

[0105] FIG. 7B is a schematic diagram of the printing operation performed on the second area 702 in which the first pass is the backward scan.

[0106] The second region 702 is located downstream of the first region 701 (see FIG. 7A) in the transport direction (−Y direction) and is adjacent to the first region 701. In the second region 703, the second pass of forward scanning is performed a relatively long time after the first pass of backward scanning. Also, the third pass of backward scanning is performed relatively soon after the second pass of forward scanning.

[0107] FIG. 8 is a table showing the time between each path of the multipath in the first region 701 (see FIG. 7(A)) and the time between each path of the multipath in the second region 702 (see FIG. 7(B)).

[0108] First, we will explain the "1st-2nd pass time" (the time from the end of the first main scan to the start of the first return scan) in the first area 701. With regard to the 1st-2nd pass time in the first area 701, excluding the waiting time on the BP side, it is possible to turn back and start the second pass printing immediately after the end of the first pass printing. Therefore, the 1st-2nd pass time in the first area 701 essentially consists of only the waiting time on the BP side.

[0109] Next, during the subsequent 2nd and 3rd passes, after the 2nd pass is recorded, the liquid ejection head 205 performs a backward scan to the HP side, waits on the HP side, and then performs a forward scan back to the BP side before recording the 3rd pass. Therefore, the "time between 2nd and 3rd passes" is equal to "backward scan time + HP side wait time + forward scan time." This type of recording operation is repeated alternately between subsequent passes, resulting in the inter-pass time shown in FIG. 8.

[0110] Next, consider the second region 702 (see FIG. 7(B)).

[0111] As shown in Figure 7(B), the second region 702 is adjacent to the first region 701 (see Figure 7(A)), and has a length in the Y direction corresponding to the ejection hole groups A1 to A6. In the second region 702, the first pass is recorded by a backward scan, and the second pass is recorded by a forward scan. From the third pass onwards, forward scans and backward scans are alternately repeated, as in the first region 701.

[0112] The time difference between each path in this case is shown in the "Second Region" column in FIG.

[0113] As shown in FIG. 8, in the second region 702 (see FIG. 7(B)), the scanning direction of each pass is reversed from that of the first region 701 (see FIG. 7(A)). The time difference between passes is also reversed. Therefore, in the second region 702 (see FIG. 7(B)), the "time between passes 1 and 2" is the "return scan time + HP side wait time + forward scan time," and the "time between passes 2 and 3" is only the wait time on the BP side. Between subsequent passes, forward scans and return scans are alternately repeated in the second region 702.

[0114] Next, we will explain why this time difference between passes affects image quality. When ink droplets are applied to the recording medium P in each pass, they may interact with ink droplets already applied to the recording medium P at that time. It is known that the manner in which this interaction occurs changes depending on the penetration and drying state of the ink droplets already applied. The penetration and drying state of ink droplets are affected by the time between passes. Therefore, the time between passes affects the interaction between ink droplets. This changes the final fixation state of the ink droplets, affecting image quality such as color development and gloss. The first and second regions, which have opposite inter-pass time lengths, are alternately arranged in the Y direction, resulting in visible time difference unevenness. Here, we have focused on the BP side to explain time difference unevenness. However, the HP side is similar to the BP side, except that the inter-pass time length is reversed. On the other hand, time difference unevenness is difficult to detect in the central area where the inter-pass time is approximately equal.

[0115] Based on the above, we will explain why time difference unevenness increases when the standby time required for drying is ensured only on the HP side. When a standby time is provided only on the HP side (i.e., when the standby time on the BP side is set to zero), the standby time on the HP side must be twice as long as when a standby time is also provided on the BP side. In this case, in the first area 701 where the first pass is a forward scan, the "time between 1st and 2nd passes" is almost zero because it is only the standby time on the BP side.

[0116] On the other hand, the "time between passes 2 and 3" is even larger because the waiting time on the HP side is doubled in addition to the round-trip scanning time. As shown in the "first area" column in Figure 8, this type of printing operation is repeated between subsequent passes.

[0117] Next, in the second region 702 where the first pass is a backward scan, contrary to the first region 701, the "time between 1st and 2nd passes" becomes an even larger value, and the "time between 2nd and 3rd passes" becomes almost zero.

[0118] As shown in the column of "areas where the first pass is the backward scan" in FIG. 8, such a printing operation is repeated thereafter.

[0119] As described above, the image quality is affected by the length of the inter-pass time. Therefore, as the difference in inter-pass time between the first region 701, where the first pass is a forward scan, and the second region 702, where the first pass is a backward scan, increases, the difference in image quality, such as color development and gloss, between these regions increases, and time difference unevenness increases. Therefore, in this embodiment, the standby times on the HP side and BP side are set so that the difference in inter-pass time between regions is kept low enough to prevent noticeable time difference unevenness, while providing a standby time that ensures an appropriate fixing effect.

[0120] (7-3) Controlling waiting time 9 is a diagram showing an example of a table that can be stored in the memory 405 (see FIG. 4) of this embodiment. (s) in FIG. 9 means (seconds).

[0121] As shown in FIG. 9, the "Required Waiting Time (s)" column indicates the time that the carriage unit 101 must wait on the HP side or the BP side in order to fix the ink applied to the recording medium P (see FIG. 1, etc.). The "HP-side Waiting Time (s)" column indicates the HP-side waiting time out of the "Required Waiting Time." The "BP-side Waiting Time (s)" column indicates the BP-side waiting time out of the "Required Waiting Time." In other words, the "Required Waiting Time (s)" column indicates the total waiting time, which is the sum of the HP-side waiting time and the BP-side waiting time.

[0122] The more difficult it is for ink to penetrate into the recording medium P, the longer the waiting time required. For example, if a medium that is difficult for ink to penetrate is used as the recording medium P, a relatively long waiting time is required. In addition, a relatively long waiting time is required when the ambient temperature is low or the ambient humidity is high. The value of the "required waiting time" is set to an appropriate value depending on conditions such as the type of recording medium, ambient temperature, and ambient humidity. In other words, it is preferable that a table like the one shown in FIG. 9 be prepared for each combination of type of recording medium, ambient temperature, ambient humidity, and other conditions.

[0123] On the other hand, as described above, it is preferable that the standby time on the HP side and the standby time on the BP side are as equal as possible from the viewpoint of preventing unevenness in the time difference. Therefore, in this embodiment, when the standby time required to fix the ink applied to the recording medium P is long enough to allow the nozzle surface 300 to dry, the standby time on the HP side and the standby time on the BP side are set to be equal to each other.

[0124] For example, if the waiting time required to fix the ink applied to the recording medium P is 4.0 seconds or less, the waiting time on the HP side is set to 2.0 seconds, and the waiting time on the BP side is set to 2.0 seconds so that the waiting time is equal to the waiting time on the HP side.

[0125] However, if the liquid ejection head 205 (see FIG. 2) is left waiting for a long time on the BP side, which does not have the maintenance mechanism 107 (see FIG. 1, etc.), there is a risk that the nozzle surface 300 (see FIG. 3) will dry out. For this reason, the waiting time on the BP side is set to be no longer than 2.0 seconds.

[0126] Therefore, the CPU 401 (see FIG. 4) of this embodiment makes the liquid ejection head wait for a first waiting time at a first waiting position after the liquid ejection head has finished its backward scan and before starting its forward scan. Then, after the liquid ejection head has finished its forward scan and before starting its backward scan, it makes the liquid ejection head wait for a second waiting time at a second waiting position. If the first waiting time is equal to or less than a predetermined value, the first waiting time and the second waiting time are set to be equal. On the other hand, if the first waiting time exceeds the predetermined value, the second waiting time is fixed to a predetermined value, and the first waiting time is set to be longer than the second waiting time.

[0127] For example, if the "necessary waiting time (s)" exceeds 4.0 seconds, the waiting time on the BP side is fixed at 2.0 seconds, and the waiting time on the HP side is set to the waiting time on the HP side minus the fixed waiting time of 2.0 seconds on the BP side.

[0128] It has been found that time difference unevenness is more noticeable the greater the variation in the time difference between successive scans of a unit area (between the first and second areas), as explained in FIG. 8 . This variation in time difference is less noticeable in printing modes with a large number of multi-passes or in printing modes with sufficiently long standby times. In other words, time difference unevenness is more noticeable the shorter the "required standby time (s)" is, and less noticeable the longer the "required standby time (s)" is. For this reason, in this embodiment, when the "required standby time (s)" is 4.0 seconds or less, suppressing time difference unevenness is prioritized over suppressing drying of the nozzle surface, and the standby times on the HP side and the BP side are set to the same value. On the other hand, when the "required standby time (s)" is greater than 4.0 seconds, suppressing drying of the nozzle surface is prioritized over suppressing time difference unevenness, and standby times of 2.0 seconds or more are performed on the HP side where the cap is provided.

[0129] In this way, according to this embodiment, by appropriately controlling the standby time on the HP side and the standby time on the BP side, it is possible to suppress drying of the nozzle surface while achieving an appropriate fixing time in which time difference unevenness is not noticeable.

[0130] As explained above, in this embodiment, if the waiting time required to fix the ink on the recording medium P is equal to or less than a predetermined value, the waiting time required to fix the ink on the recording medium P is divided into two equal parts, that is, the HP side and the BP side. If the waiting time required to fix the ink on the recording medium P exceeds the predetermined value, the waiting time on the BP side is fixed to be shorter than the waiting time on the HP side. In this case, the waiting time on the HP side is set to a value obtained by subtracting the waiting time on the BP side, which is fixed to a predetermined time, from the waiting time required to fix the ink on the recording medium P.

[0131] With this configuration, even if a relatively long standby time is required to fix the ink on the recording medium P, the liquid ejection head does not have to wait for a long time on the BP side. The standby time on the BP side is completed in a relatively short time, and the long standby time is performed on the HP side where the maintenance mechanism is located.

[0132] Therefore, according to the liquid ejection device of this embodiment, it is possible to prevent the nozzle surface from drying out and ensure the time for the liquid to set.

[0133] [Modification of the first embodiment] In the first embodiment, an example was shown in which a table such as that shown in Fig. 9 is prepared in advance and stored in the device's memory 405. However, the standby time on the HP side and the standby time on the BP side may also be set by the CPU 401 depending on the conditions at the time.

[0134] Fig. 10 is a flowchart showing the process of setting the standby time on the HP side and the standby time on the BP side in this modified example. The series of processes shown in the flowchart in Fig. 10 are performed by the CPU 401 (see Fig. 4) by loading program code stored in the ROM 402 (see Fig. 4) into the RAM 403 (see Fig. 4) and executing it. Note that the symbol "S" in the explanation of each process refers to a step in the flowchart.

[0135] In S1001, the CPU 401 acquires the waiting time required for the ink to fix on the recording medium P that is the target of recording. Note that other information may also be acquired in S1001. For example, the CPU 401 references a table stored in the memory 405 (see FIG. 4) that associates the type of recording medium P with the drying time of the recording medium P to acquire the time required for the ink to fix on the recording medium P. Note that the type of recording medium P that is the target of recording may be input by the user via the input / output port 404, or may be acquired by a sensor provided in the device. After completing the processing of S1001, the CPU 401 performs the processing of S1002.

[0136] In S1002, the CPU 401 determines whether the time required to fix the ink on the recording medium P exceeds a predetermined value (for example, 4.0 seconds). If the time required to fix the ink on the recording medium P exceeds the predetermined value, the CPU 401 performs the process of S1003 (YES in S1002). If the time required to fix the ink on the recording medium P is equal to or less than the predetermined value, the CPU 401 performs the process of S1005 (NO in S1002).

[0137] In S1003, the CPU 401 fixes the waiting time on the BP side (for example, 2.0 seconds). After the process of S1003 ends, the CPU 401 performs the process of S1004.

[0138] In S1004, the CPU 401 sets the standby time on the HP side to a value obtained by subtracting the standby time on the BP side from the time required to fix the ink on the recording medium P (for example, 5.0 seconds - 2.0 seconds = 3.0 seconds). After the process of S1004 ends, the CPU 401 ends the setting of the standby time on the HP side and the setting of the standby time on the BP side.

[0139] In S1005, the CPU 401 divides the time required to fix the ink on the recording medium P in half and sets the waiting time on the HP side and the waiting time on the BP side (for example, 4.0 seconds ÷ 2 = 2.0 seconds). This makes it possible to suppress time difference unevenness as much as possible. After the processing of S1005 ends, the CPU 401 ends setting the waiting time on the HP side and the waiting time on the BP side.

[0140] The standby time on the HP side and the standby time on the BP side do not necessarily have to be the same value. There may be a slight difference in standby time between the HP side and the BP side due to structural differences, etc. Even if such a slight difference does occur, it is not a problem as long as the time difference unevenness is not noticeable. In other words, if the time required to fix the ink on the recording medium does not exceed a predetermined value, the difference between the standby time on the HP side and the standby time on the BP side should be smaller than when the time required exceeds the predetermined value.

[0141] As explained above, in this modified example, if the time required to fix the ink on the recording medium P exceeds a predetermined value, the standby time on the BP side is fixed to be shorter than the standby time on the HP side. Then, the standby time that is insufficient due to the standby time on the BP side being fixed is added to the standby time on the HP side.

[0142] In this way, the liquid ejection device of this modified example also makes it possible to prevent the nozzle surface from drying out and ensure the time for the liquid to set.

[0143] [Second embodiment] The present embodiment aims to provide a liquid ejection device that can more flexibly set the standby time on the HP side and the standby time on the BP side according to the length of the scanning time. In the following explanation, the same reference numerals are used for the same or corresponding configurations as in the first embodiment, and explanations are omitted, and differences will be mainly explained.

[0144] FIG. 11 is a diagram showing an example of a table that can be applied to this embodiment.

[0145] In this embodiment, the upper limit of the standby time on the BP side is set to correspond to the scanning time of the liquid ejection head 205 (see FIG. 2). The upper limit of the standby time on the BP side is set to decrease as the scanning time becomes longer. This is because the longer the scanning time, the more the nozzle surface dries during scanning, so it is necessary to reduce the standby time on the BP side, where preliminary ejection cannot be performed. For this reason, the standby time on the BP side is set to be equal to or less than this upper limit. The value obtained by subtracting the standby time on the BP side from the standby time required to fix the ink on the recording medium P is then set as the standby time on the HP side.

[0146] Generally, the scanning time varies depending on the width of the recording medium, the width of the image, the set recording mode, etc., but here we will explain assuming that the scanning time is appropriately adjusted depending on the width of the image.

[0147] 11 is a diagram showing an example of a table in which the image width "image width (inches)," the upper limit of the waiting time on the BP side "BP side waiting upper limit time (s)," the "BP side waiting time (s)," and the "HP side waiting time (s)" are stored in association with each other. Note that this example shows a case where the waiting time required to fix the ink on the recording medium P is 4.0 seconds.

[0148] For example, suppose the width of the image to be formed is between 20 inches and 30 inches, and the upper limit of the waiting time on the BP side is set to 1.6 seconds. From the perspective of time difference unevenness, it is preferable that the waiting time on the HP side and the waiting time on the BP side are equal. However, if the waiting time required to fix the ink on the recording medium P is 4.0 seconds, the waiting time on the BP side will be 2.0 seconds, exceeding the upper limit. For this reason, the waiting time on the BP side is set to the maximum of 1.6 seconds. Furthermore, 2.4 seconds, which is the time required to fix the ink on the recording medium P minus the BP side waiting time of 1.6 seconds, is set as the waiting time on the HP side.

[0149] On the other hand, if half of the waiting time required to fix the ink on the recording medium P is less than the upper limit of the waiting time on the BP side, the waiting time on the HP side and the waiting time on the BP side are set to a value obtained by dividing the waiting time required to fix the ink on the recording medium P in half.

[0150] For example, if the width of the image to be formed is less than 10 inches, the upper limit of the waiting time on the BP side is set to 2.4 seconds. If the waiting time required for the ink to fix on the recording medium P is 4.0 seconds, then 2.0 seconds, obtained by dividing this value in half, does not exceed the upper limit of 2.4 seconds. Therefore, 2.0 seconds, obtained by dividing 4.0 seconds in half, are set as the waiting time on the BP side and the waiting time on the HP side, respectively.

[0151] According to this configuration, by setting the standby times on the HP side and the BP side to appropriate values ​​according to the scanning time, it is possible to suppress drying of the nozzle surface while achieving an appropriate fixing time that does not make time difference unevenness noticeable. Furthermore, when the scanning time is relatively short, the standby times on the HP side and the BP side do not necessarily have to be the same, as long as the time required for fixing the ink on the recording medium P can be secured without exceeding the upper limit of the standby time on the BP side. In other words, the standby times on the HP side and the BP side may be slightly different, as long as the time difference unevenness is not noticeable.

[0152] As explained above, in the liquid ejection device of this embodiment, in order to ensure the wait time necessary for the ink to fix on the recording medium, the wait time on the HP side, where preliminary ejection can be performed, is set to a value longer than the wait time on the BP side, where preliminary ejection cannot be performed. By appropriately controlling the wait times on the HP side and the BP side based on the scanning time, it is possible to suppress drying of the nozzle surface while achieving an appropriate fixation time that does not cause noticeable time difference unevenness.

[0153] Therefore, with the liquid ejection device of this embodiment, it is possible to prevent the nozzle surface from drying out while ensuring time for the liquid to set. Furthermore, the standby time on the HP side and the standby time on the BP side can be set more flexibly according to the length of the scanning time.

[0154] In this embodiment, too, it is not essential to prepare a table such as that shown in Fig. 11. As explained in the first embodiment using Fig. 10, the CPU 401 may make a determination based on various conditions.

[0155] [Third embodiment] The purpose of this embodiment is to provide a liquid ejection device that can more flexibly set the standby time on the HP side and the standby time on the BP side depending on how easily the nozzle surface dries. In the following explanation, the same reference numerals are used for configurations that are similar to or correspond to those of the first and second embodiments, and explanations will be omitted, and differences will be mainly explained.

[0156] FIG. 12 is a diagram showing an example of a table that can be applied to this embodiment.

[0157] In the second embodiment, the upper limit of the waiting time on the BP side is set according to the length of the scanning time, whereas in this embodiment, the upper limit of the waiting time on the BP side is set according to the surrounding environment.

[0158] As shown in FIG. 12, in this embodiment, an upper limit on the waiting time on the BP side is set in accordance with how easily the nozzle surface 300 (see FIG. 3) dries. In this embodiment, the upper limit on the waiting time on the BP side is set to decrease as the environment becomes more susceptible to drying the nozzle surface. This is because the more easily the nozzle surface dries, the more it is necessary to reduce the waiting time on the BP side, where preliminary ejection cannot be performed. In this embodiment, as an example of a situation in which the nozzle surface dries more easily, a case in which the ambient temperature around the location where the liquid ejection device 100 (see FIG. 1) is installed will be described. However, examples in which the nozzle surface dries more easily are not limited to cases in which the ambient temperature is high. For example, the nozzle surface dries more easily as the ambient humidity decreases.

[0159] For example, when the ambient temperature is between 20°C and 30°C, the upper limit of the waiting time on the BP side is set to 1.0 second. Here, if the waiting time required for fixing the ink on the recording medium P is 4.0 seconds, from the perspective of time difference unevenness, it is preferable that the waiting time on the HP side and the waiting time on the BP side are each 2.0 seconds. However, this would cause the waiting time on the BP side to exceed the upper limit. For this reason, the waiting time on the BP side is set to the maximum upper limit of 1.0 second. Then, 3.0 seconds, calculated by subtracting the 1.0 second waiting time on the BP side from 4.0 seconds, is set as the waiting time on the HP side.

[0160] On the other hand, if half of the waiting time required to fix the ink on the recording medium P is less than the upper limit of the waiting time on the BP side, the waiting time on the HP side and the waiting time on the BP side are set to be equal to each other.

[0161] For example, when the ambient temperature is below 10°C, the upper limit of the waiting time on the BP side is set to 3.0 seconds. If the waiting time required for fixing the ink on the recording medium P is 4.0 seconds, then 2.0 seconds, obtained by dividing this value in half, does not exceed the upper limit of 3.0 seconds. Therefore, 2.0 seconds, obtained by dividing 4.0 seconds in half, is set as the waiting time on the BP side and the waiting time on the HP side, respectively.

[0162] With this configuration, by setting the standby time on the HP side and the standby time on the BP side to appropriate values ​​according to the surrounding environment, it is possible to suppress drying of the nozzle surface and achieve an appropriate fixing time that does not make time difference unevenness noticeable. Note that the standby time on the HP side and the standby time on the BP side may differ slightly, as long as the time difference unevenness is not noticeable.

[0163] As explained above, in the liquid ejection device of this embodiment, in order to ensure the wait time necessary for the ink to fix on the recording medium, the wait time on the HP side, where preliminary ejection can be performed, is set to a value longer than the wait time on the BP side, where preliminary ejection cannot be performed. By appropriately controlling the wait times on the HP side and the BP side based on the ambient environment, it is possible to suppress drying of the nozzle surface while achieving an appropriate fixation time that does not cause noticeable time difference unevenness.

[0164] Therefore, with the liquid ejection device of this embodiment, it is possible to ensure the time for the liquid to set while suppressing drying of the nozzle surface. Furthermore, the standby time on the HP side and the standby time on the BP side can be set more flexibly depending on how easily the nozzle surface dries.

[0165] [Other embodiments] In the first to third embodiments, an inkjet recording apparatus and a recording method using the inkjet recording apparatus are described. However, the technology of the present disclosure can also be applied to an image processing apparatus or an image processing method that generates data for performing the recording methods described in the first to third embodiments.

[0166] Furthermore, the technology of the present disclosure can also be applied to a configuration in which a program for performing the recording method described in the first to third embodiments is prepared separately from the liquid ejection apparatus.

[0167] Furthermore, the technology disclosed herein can be effectively applied to various liquid ejection devices, such as thermal jet inkjet recording devices, so-called piezo inkjet recording devices that eject ink using piezoelectric elements, as well as thermal jet inkjet recording devices.

[0168] In the first to third embodiments, the difference between the standby time on the HP side and the standby time on the BP side was considered as a factor in time difference unevenness. However, in addition to the difference between the standby time on the HP side and the standby time on the BP side, factors such as the type of recording medium, the distance from the recording surface of the recording medium to the nozzle surface of the liquid ejection head, the color of the image, and the amount of ink ejected can also affect the visibility of time difference unevenness. Therefore, taking these factors into consideration, the upper limit of the standby time on the BP side can be varied to ensure time for the liquid to set, prevent the nozzle surface from drying, and suppress time difference unevenness.

[0169] In the above embodiment, an appropriate waiting time is provided between each scan to ensure that the recording medium P has time to pass through an area where the heating effect of the heater 203 can be obtained. However, in this disclosure, the heater 203 is not an essential requirement. Even in a recording apparatus that does not have a fixing device to promote ink fixation, providing an appropriate waiting time between each scan of multi-pass recording may be necessary to obtain high-quality images. In other words, regardless of the presence or absence of the heater 203, by appropriately controlling the waiting time on the HP side and the waiting time on the BP side, it is possible to ensure an appropriate fixing time that prevents noticeable time-lag unevenness while suppressing drying of the nozzle surface.

[0170] In the second embodiment, the time required for one scan by the liquid ejection head was obtained based on the width of the image in the scanning direction. However, the time required for one scan by the liquid ejection head may also be obtained based on the scanning speed of the liquid ejection head. For example, the time required for one scan can be calculated based on the carriage scanning distance, which is based on the width of the recording medium or image, and the carriage speed, which is in accordance with the recording mode. The shorter the required time, the larger the "BP side standby upper limit time (s)" can be set to.

[0171] The technology of the present disclosure can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors of a computer in the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0172] The present disclosure includes the following configurations and methods.

[0173] [Configuration 1] a scanning means for reciprocatingly scanning a liquid ejection head in a scanning direction, the liquid ejection head performing an ejection operation by ejecting liquid; a conveying means for conveying the recording medium in a conveying direction intersecting the scanning direction; After the backward scanning of the scanning means is completed and before the forward scanning of the scanning means is started, the scanning means is made to wait at a first waiting position for a first waiting time; a control means for causing the scanning means to wait at a second waiting position for a second waiting time after the forward scanning of the scanning means has finished and before the backward scanning of the scanning means has started, The control means When the first waiting time is a first value, the second waiting time is controlled to the first value; When the first waiting time is a second value greater than the first value, the second waiting time is controlled to be shorter than the first waiting time. A liquid ejection device characterized by:

[0174] [Configuration 2] When the first waiting time is the second value, the control means controls the second waiting time to a predetermined value. 2. The liquid ejection device according to claim 1.

[0175] [Configuration 3] The control means a total waiting time of the first waiting time and the second waiting time required to fix the liquid ejected onto the recording medium is obtained; when the value obtained by dividing the total waiting time in half is the first value, setting each of the first waiting time and the second waiting time to the value obtained by dividing the total waiting time in half, If the value obtained by dividing the total waiting time in half is the second value, the first waiting time is set to be longer than the second waiting time. 3. The liquid ejection device according to claim 1 or 2.

[0176] [Configuration 4] Further provided is a drying means for drying the recording medium, the drying means is provided downstream of the liquid ejection head in the transport direction, the total waiting time is the time required for the liquid ejected onto the recording medium by the liquid ejection head to be dried by the drying means; 4. The liquid ejection device according to configuration 3.

[0177] [Configuration 5] In the scanning direction, the first standby position is a position where a maintenance mechanism is disposed that receives liquid preliminarily ejected by the liquid ejection head. The liquid ejection device according to any one of the first to fourth aspects.

[0178] [Configuration 6] further comprising a storage means for storing a table in which the first waiting time, the second waiting time, and the total waiting time are associated with each other; the control means sets the first waiting time and the second waiting time by referring to the table. The liquid ejection device according to any one of configurations 3 to 5.

[0179] [Configuration 7] The control means a total waiting time of the first waiting time and the second waiting time required to fix the liquid ejected onto the recording medium is obtained; the upper limit value of the second waiting time is set so that the shorter the time required for one scan by the liquid ejection head, the smaller the upper limit value of the second waiting time becomes; when a value obtained by dividing the total waiting time in half exceeds the upper limit value, the first waiting time and the second waiting time are set so that the second waiting time becomes the upper limit value and the first waiting time becomes a value obtained by subtracting the upper limit value from the total waiting time. 7. The liquid ejection device according to any one of the first to sixth aspects.

[0180] [Configuration 8] the control means acquires the required time based on a width in the scanning direction of an image recorded by the liquid ejection head; 8. The liquid ejection device according to configuration 7.

[0181] [Configuration 9] the control means acquires the required time based on a width in the scanning direction of a recording medium on which the liquid ejection head performs recording; The liquid ejection device according to configuration 7 or 8.

[0182] [Configuration 10] the control means acquires the required time based on the scanning speed of the scanning means; 10. The liquid ejection device according to configuration 9.

[0183] [Configuration 11] The control means a total waiting time of the first waiting time and the second waiting time required to fix the liquid ejected onto the recording medium is obtained; the upper limit value of the second waiting time is set so that the upper limit value becomes smaller as the nozzle surface of the liquid ejection head becomes more prone to dryness in the environment; When the value obtained by dividing the total waiting time in half exceeds the upper limit value, the second waiting time is set to the upper limit value, and the first waiting time is set to be longer than the second waiting time. 11. The liquid ejection device according to any one of the first to tenth aspects.

[0184] [Configuration 12] the control means sets the upper limit value of the second standby time so that the upper limit value decreases as the ambient temperature increases. 12. The liquid ejection device according to claim 11.

[0185] [Configuration 13] the control means sets the upper limit value of the second waiting time so that the lower the ambient humidity is, the smaller the upper limit value of the second waiting time becomes. 13. The liquid ejection device according to claim 11 or 12.

[0186] [Configuration 14] the liquid is ink or a reaction liquid that reacts with ink; 14. The liquid ejection device according to any one of configurations 1 to 13.

[0187] [Method 15] a scanning means for reciprocatingly scanning a liquid ejection head that performs an ejection operation of ejecting liquid in a scanning direction; a conveying means for conveying the recording medium in a conveying direction intersecting the scanning direction; A method for controlling a liquid ejection device comprising: a step of causing the scanning means to wait at a first waiting position for a first waiting time after the scanning means has finished its backward scanning and before the scanning means starts its forward scanning; a step of causing the scanning means to wait at a second waiting position for a second waiting time after the forward scanning of the scanning means is completed and before the backward scanning of the scanning means is started; and when the first waiting time is a first value, the second waiting time is the first value; When the first waiting time is a second value that is greater than the first value, the second waiting time is shorter than the first waiting time. A control method comprising: [Method 16] When the first waiting time is the second value, the second waiting time is a predetermined value. The control method according to method 15.

Claims

1. a scanning means for reciprocatingly scanning a liquid ejection head in a scanning direction, the liquid ejection head performing an ejection operation by ejecting liquid; a conveying means for conveying the recording medium in a conveying direction intersecting the scanning direction; After the backward scanning of the scanning means is completed and before the forward scanning of the scanning means is started, the scanning means is made to wait at a first waiting position for a first waiting time; a control means for causing the scanning means to wait at a second waiting position for a second waiting time after the scanning means has finished its forward scan and before the scanning means starts its backward scan, The control means When the first waiting time is a first value, the second waiting time is controlled to the first value; When the first waiting time is a second value greater than the first value, the second waiting time is controlled to be shorter than the first waiting time. A liquid ejection device characterized by:

2. When the first waiting time is the second value, the control means controls the second waiting time to a predetermined value. The liquid ejection device according to claim 1 .

3. The control means a total waiting time of the first waiting time and the second waiting time required to fix the liquid ejected onto the recording medium is obtained; when the value obtained by dividing the total waiting time in half is the first value, setting each of the first waiting time and the second waiting time to the value obtained by dividing the total waiting time in half, When the value obtained by dividing the total waiting time in half is the second value, the first waiting time is set to be longer than the second waiting time. The liquid ejection device according to claim 1 .

4. Further provided is a drying means for drying the recording medium, the drying means is provided downstream of the liquid ejection head in the transport direction, the total waiting time is the time required for the liquid ejected onto the recording medium by the liquid ejection head to be dried by the drying means; The liquid ejection device according to claim 3 .

5. In the scanning direction, the first standby position is a position where a maintenance mechanism that receives liquid preliminarily ejected by the liquid ejection head is disposed. The liquid ejection device according to claim 1 or 2.

6. a storage means for storing a table in which the first waiting time, the second waiting time, and the total waiting time are associated with each other; the control means sets the first waiting time and the second waiting time by referring to the table. The liquid ejection device according to claim 3 .

7. The control means a total waiting time of the first waiting time and the second waiting time required to fix the liquid ejected onto the recording medium is obtained; the upper limit value of the second waiting time is set so that the shorter the time required for one scan by the liquid ejection head, the smaller the upper limit value of the second waiting time becomes; when a value obtained by dividing the total waiting time in half exceeds the upper limit value, the first waiting time and the second waiting time are set so that the second waiting time becomes the upper limit value and the first waiting time becomes a value obtained by subtracting the upper limit value from the total waiting time. The liquid ejection device according to claim 1 or 2.

8. the control means acquires the required time based on a width in the scanning direction of an image recorded by the liquid ejection head; The liquid ejection device according to claim 7 .

9. the control means acquires the required time based on a width in the scanning direction of a recording medium on which the liquid ejection head performs recording; The liquid ejection device according to claim 7 .

10. the control means acquires the required time based on the scanning speed of the scanning means; The liquid ejection device according to claim 9 .

11. The control means a total waiting time of the first waiting time and the second waiting time required to fix the liquid ejected onto the recording medium is obtained; the upper limit value of the second waiting time is set so that the upper limit value becomes smaller as the nozzle surface of the liquid ejection head becomes more prone to dryness in the environment; When a value obtained by dividing the total waiting time in half exceeds the upper limit value, the second waiting time is set to the upper limit value, and the first waiting time is set to be longer than the second waiting time. The liquid ejection device according to claim 1 or 2.

12. the control means sets the upper limit value of the second standby time so that the upper limit value decreases as the ambient temperature increases. The liquid ejection device according to claim 11.

13. the control means sets the upper limit value of the second waiting time so that the lower the ambient humidity is, the smaller the upper limit value of the second waiting time becomes. The liquid ejection device according to claim 11.

14. the liquid is ink or a reaction liquid that reacts with ink; The liquid ejection device according to claim 1 or 2.

15. a scanning means for reciprocatingly scanning a liquid ejection head that performs an ejection operation of ejecting liquid in a scanning direction; a conveying means for conveying the recording medium in a conveying direction intersecting the scanning direction; A method for controlling a liquid ejection device comprising: a step of causing the scanning means to wait at a first waiting position for a first waiting time after the scanning means has finished its backward scanning and before the scanning means starts its forward scanning; a step of causing the scanning means to wait at a second waiting position for a second waiting time after the forward scanning of the scanning means has finished and before the backward scanning of the scanning means has started; and when the first waiting time is a first value, the second waiting time is the first value; When the first waiting time is a second value that is greater than the first value, the second waiting time is shorter than the first waiting time. A control method comprising:

16. When the first waiting time is the second value, the second waiting time is a predetermined value. The control method according to claim 15.

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