JP4353432B2 - Image processing method, program, image processing apparatus, image forming apparatus, and image forming system - Google Patents

Description

  The present invention relates to an image processing method, a program, an image forming apparatus, an image processing apparatus, an image forming apparatus, and an image forming system.

  2. Related Art As an image forming apparatus such as a printer, a facsimile machine, a copying machine, and a multifunction machine of these, for example, an ink jet recording apparatus using a liquid discharge head as a recording head is known. The ink jet recording apparatus means a sheet (not limited to paper but including OHP, which can be attached to ink droplets, other liquids, etc.) from a recording head, and is a recording medium or recording medium, recording paper, recording Ink is formed as a recording liquid onto a sheet of paper) to form an image (recording, printing, printing, and printing are also used synonymously).

  Such an ink jet recording apparatus is a serious type that forms an image by mounting a recording head on a carriage and moving the recording head intermittently in a direction perpendicular to the main scanning direction while moving in the main scanning direction. There is a line type that includes a line type recording head and forms an image by conveying a sheet in a direction orthogonal to the nozzle arrangement direction.

  In any type of inkjet recording apparatus, an image is formed by arranging dots in a matrix in the main scanning direction (or nozzle arrangement direction) and the paper feed direction.

  Therefore, especially when recording a character image, dots increase or decrease in a staircase pattern according to the resolution in the shaded portion of the character, so that the jaggedness of the dots (jaggy) is recognized and the image quality is improved. You may not get enough.

  Inkjet recording uses liquid ink, so when printing on plain paper, image color reproducibility, durability, light resistance, ink drying, character bleeding (feathering), color boundary There are image quality degradation problems peculiar to ink jet recording such as bleeding (color bleed). Furthermore, when trying to print on plain paper at high speed, it is extremely difficult to print satisfying all these characteristics. .

Regarding the former image quality deterioration due to jaggies, as a smoothing method for smoothing the contour of a jagged character image, there is a smoothing method called anti-aliasing as described in Patent Document 1.
Japanese Utility Model Laid-Open No. 03-113552

  However, since this method changes the dot with a very large number of gradations, high-accuracy smoothing is possible, but the processing is very complicated and requires processing time. Thus, it is not suitable for an image forming apparatus that requires high throughput.

  With respect to image deterioration due to character bleeding in the latter plain paper printing, a pigment-based ink using an organic pigment, carbon black or the like as a colorant is used for plain paper printing instead of a dye-based ink. Since pigments are not soluble in water unlike dyes, they are usually used as water-based inks in a state where pigments are mixed with a dispersing agent, dispersed and stably dispersed in water.

  By the way, when a document is created by application software and output by an image forming apparatus such as an ink jet recording apparatus that forms an image with dot arrangement, the font (generally TrueType font) specified by the application software is the application software. Or character data composed of dots for output by the image forming apparatus using a printer driver or the like.

  In this case, depending on the application software and printer driver, there is a problem that the output characters may be thin. This is considered to be because the outline of the character cannot be faithfully reproduced depending on the printing resolution when forming the outline portion of the TrueType font.

  Also, depending on the type of character, for example, the Gothic font is a relatively thick character, while the Mincho font is a thin font. Therefore, when a document is created in the Mincho style, it may be desired to output it with a slightly thicker character so that it is easier to read.

  In this case, there is a process of thickening a designated character by using a function called bold or bold of the application software. However, when thickening with such conventional processing, it usually becomes thicker than a few dots, so it becomes a character of a level clearly different from the thickness of the original character, and all characters are processed. If done, there is a problem that the document is rather difficult to read.

The present invention has been made in view of the above problems, an object of the Turkey to improve the images quality of an output image.

In order to solve the above problems, an image processing method according to the present invention includes:
A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In an image processing method for generating the image data of an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot . A size dot is added.

The program according to the present invention is:
A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In a program for causing a computer to execute processing for generating the image data of an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot. The computer is configured to execute processing for adding size dots .

An image processing apparatus according to the present invention includes:
A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In an image processing apparatus for generating the image data of an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot. A configuration is provided that includes means for executing processing for adding dots of size .

An image forming apparatus according to the present invention includes:
A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot. A configuration is provided that includes means for executing processing for adding dots of size .

An image forming system according to the present invention discharges a plurality of droplets of different colors and sizes based on image data with the image processing apparatus according to the present invention , wherein the first direction has a first resolution and the first The direction orthogonal to the direction is configured with an image forming apparatus capable of forming an image at a second resolution lower than the first resolution .

According to the image processing method, the program, the image processing apparatus, the image forming apparatus, and the image forming system according to the present invention, the image thickening is performed by adding the image dot to the blank dot adjacent to the image dot forming the image to thicken the image. In the first direction for forming the image at the first resolution, the first size dot is formed in the blank dot adjacent to the image dot, and the image is formed at the second resolution lower than the first resolution. In the second direction, since the second size dot smaller than the first size dot is added to the blank dot adjacent to the image dot, the image quality of the output image can be improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus that outputs image data generated by an image processing method according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining the overall structure of the mechanism section of the image forming apparatus, and FIG. 2 is a plan view for explaining the mechanism section.
In this image forming apparatus, a carriage 3 is slidably held in a main scanning direction by a guide rod 1 and a guide rail 2 which are guide members horizontally mounted on left and right side plates (not shown), and a driving pulley 6A is driven by a main scanning motor 4. 2 is moved and scanned in the direction indicated by the arrow (main scanning direction) in FIG. 2 via a timing belt 5 stretched between the roller and the driven pulley 6B.

  The carriage 3 includes, for example, four recording heads 7y, 7c, 7m, which are liquid ejection heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (K), respectively. A plurality of ink ejection openings are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward.

  The liquid discharge head constituting the recording head 7 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator using an electrostatic force, an electrostatic actuator using an electrostatic force, and the like provided as pressure generating means for generating a pressure for discharging a droplet can be used. In addition, the configuration is not limited to an independent head for each color, and may be configured with one or a plurality of liquid ejection heads having a nozzle row composed of a plurality of nozzles that eject droplets of a plurality of colors.

  The carriage 3 is also equipped with sub-tanks 8 for each color for supplying ink of each color to the recording head 7. Ink is supplied to the sub tank 8 from a main tank (ink cartridge) (not shown) via an ink supply tube 9.

  On the other hand, as a paper feeding unit for feeding paper 12 stacked on a paper stacking unit (pressure plate) 11 such as a paper feeding cassette 10, a half-moon roller (for separating and feeding the paper 12 one by one from the paper stacking unit 11) A separation pad 14 made of a material having a large friction coefficient is provided facing the sheet feeding roller 13 and the sheet feeding roller 13, and the separation pad 14 is urged toward the sheet feeding roller 13 side.

  In order to convey the sheet 12 fed from the sheet feeding unit below the recording head 7, a conveyance belt 21 for electrostatically attracting and conveying the sheet 12 and a guide 15 from the sheet feeding unit. A counter roller 22 for transporting the sheet 12 fed between the conveyor belt 21 and the conveyor belt 21, and for shifting the sheet 12 fed substantially vertically upward by approximately 90 ° to follow the conveyor belt 21. A conveyance guide 23 and a pressing roller 25 urged toward the conveyance belt 21 by a pressing member 24 are provided. In addition, a charging roller 26 as a charging unit for charging the surface of the transport belt 21 is provided.

  Here, the conveyance belt 21 is an endless belt, is stretched between the conveyance roller 27 and the tension roller 28, and the conveyance roller 27 rotates from the sub-scanning motor 31 via the timing belt 32 and the timing roller 33. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 29 is disposed on the back side of the conveying belt 21 corresponding to the image forming area by the recording head 7. The charging roller 26 is disposed so as to come into contact with the surface layer of the transport belt 21 and rotate following the rotation of the transport belt 21.

  Further, as shown in FIG. 2, a slit disk 34 is attached to the shaft of the transport roller 27, and a sensor 35 for detecting the slit of the slit disk 34 is provided. A rotary encoder 36 is configured.

  Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 7, a separation claw 51 for separating the paper 12 from the transport belt 21, a paper discharge roller 52 and a paper discharge roller 53, and a discharge And a paper discharge tray 54 for stocking the paper 12 to be printed.

  A double-sided paper feeding unit 55 is detachably mounted on the back. The double-sided paper feeding unit 55 takes in the paper 12 returned by the reverse rotation of the transport belt 21, reverses it, and feeds it again between the counter roller 22 and the transport belt 21.

  Further, as shown in FIG. 2, a maintenance / recovery mechanism 56 for maintaining and recovering the nozzle state of the recording head 7 is disposed in the non-printing area on one side of the carriage 3 in the scanning direction.

  The maintenance / recovery machine 56 is provided with caps 57 for capping each nozzle surface of the recording head 7, a wiper blade 58 as a blade member for wiping the nozzle surface, and for discharging the thickened recording liquid. An empty discharge receiver 59 for receiving droplets when performing empty discharge for discharging droplets that do not contribute to recording is provided.

  In the image forming apparatus configured as described above, the sheets 12 are separated and fed one by one from the sheet feeding unit, and the sheet 12 fed substantially vertically upward is guided by the guide 15, and includes the transport belt 21 and the counter roller 22. The leading end is guided by the conveying guide 23 and pressed against the conveying belt 21 by the pressing roller 25, and the conveying direction is changed by approximately 90 °.

  At this time, a control unit (not shown) applies an alternating voltage that alternately repeats positive and negative to the charging roller 26 from the AC bias supply unit, and a charging voltage pattern that alternates the conveying belt 21, that is, a sub-scanning direction that is a circumferential direction. In addition, charging is performed with a pattern in which plus and minus are alternately repeated with a predetermined width. When the paper 12 is fed onto the charged transport belt 21, the paper 12 is attracted to the transport belt 21 by electrostatic force, and the paper 12 is transported in the sub-scanning direction by the circular movement of the transport belt 21.

  Therefore, by driving the recording head 7 according to the image signal while moving the carriage 3 in the forward and backward directions, ink droplets are ejected onto the stopped paper 12 to record one line. After transporting a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 54.

  In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 12 is fed into the double-sided paper feeding unit 61 by rotating the conveyor belt 21 in the reverse direction. The paper 12 is reversed (with the back surface being the printing surface), fed again between the counter roller 22 and the transport belt 21, controlled in timing, and transported onto the transport bell 21 as described above. After recording on the back side, the sheet is discharged onto the discharge tray 54.

  During printing (recording) standby, the carriage 3 is moved to the maintenance / recovery mechanism 55 side, and the nozzle surface of the recording head 7 is capped by the cap 57, and the nozzles are kept in a wet state. To prevent. In addition, the recording liquid is sucked from the nozzle in a state where the recording head 7 is capped by the cap 57, and a recovery operation is performed to discharge the thickened recording liquid and bubbles, and the ink adhered to the nozzle surface of the recording head 7 by this recovery operation. Wiping is performed with a wiper blade 58 in order to remove the cleaning. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 7 is maintained.

  Next, an example of the liquid discharge head constituting the recording head 7 will be described with reference to FIGS. 3 is a cross-sectional explanatory diagram along the longitudinal direction of the liquid chamber of the head, and FIG. 4 is a cross-sectional explanatory diagram of the head along the lateral direction of the liquid chamber (nozzle arrangement direction).

  This liquid discharge head includes, for example, a flow path plate 101 formed by anisotropic etching of a single crystal silicon substrate, a vibration plate 102 formed by, for example, nickel electroforming bonded to the lower surface of the flow path plate 101, a flow path A nozzle plate 103 joined to the upper surface of the plate 101 is joined and laminated, and a nozzle communication path 105 that is a flow path through which a nozzle 104 that discharges droplets (ink droplets) communicates therewith and a liquid chamber that is a pressure generation chamber. 106, an ink supply port 109 communicating with a common liquid chamber 108 for supplying ink to the liquid chamber 106 through a fluid resistance portion (supply path) 107 is formed.

  In addition, two rows (only one row is shown in FIG. 6) of stacked piezoelectric elements as electromechanical conversion elements that are pressure generating means (actuator means) for pressurizing ink in the liquid chamber 106 by deforming the diaphragm 102. An element 121 and a base substrate 122 to which the piezoelectric element 121 is bonded and fixed are provided. Note that a column portion 123 is provided between the piezoelectric elements 121. This support portion 123 is a portion formed simultaneously with the piezoelectric element 121 by dividing and processing the piezoelectric element member. However, since the drive voltage is not applied, the support portion 123 becomes a simple support.

  Further, an FPC cable 126 equipped with a drive circuit (drive IC) (not shown) is connected to the piezoelectric element 121.

  The peripheral edge of the diaphragm 102 is joined to a frame member 130, and the frame member 130 serves as a through-hole 131 and a common liquid chamber 108 that house an actuator unit composed of the piezoelectric element 121 and the base substrate 122. A recess and an ink supply hole 132 for supplying ink from the outside to the common liquid chamber 108 are formed. The frame member 130 is formed by injection molding with a thermosetting resin such as an epoxy resin or polyphenylene sulfite, for example.

  Here, the flow path plate 101 is formed by, for example, subjecting the single crystal silicon substrate having a crystal plane orientation (110) to anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the nozzle communication path 105, Although a recess or a hole serving as the liquid chamber 106 is formed, the invention is not limited to a single crystal silicon substrate, and other stainless steel substrates, photosensitive resins, and the like can also be used.

  The vibration plate 102 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). Alternatively, a metal plate or a joining member between a metal and a resin plate may be used. it can. The piezoelectric element 121 and the support post 123 are bonded to the diaphragm 102 with an adhesive, and the frame member 130 is further bonded with an adhesive.

  The nozzle plate 103 forms a nozzle 104 having a diameter of 10 to 30 μm corresponding to each liquid chamber 106 and is bonded to the flow path plate 101 with an adhesive. The nozzle plate 103 is formed by forming a water repellent layer on the outermost surface of a nozzle forming member made of a metal member via a required layer.

  The piezoelectric element 121 is a stacked piezoelectric element (here, PZT) in which piezoelectric materials 151 and internal electrodes 152 are alternately stacked. An individual electrode 153 and a common electrode 154 are connected to each internal electrode 152 drawn out to different end faces of the piezoelectric element 121 alternately. In this embodiment, the ink in the liquid chamber 106 is pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element 121. However, the pressure in the d31 direction is used as the piezoelectric direction of the piezoelectric element 121. The ink in the liquid chamber 106 may be pressurized. Alternatively, a structure in which one row of piezoelectric elements 121 is provided on one substrate 122 may be employed.

  In the liquid discharge head having such a configuration, for example, by lowering the voltage applied to the piezoelectric element 121 from the reference potential, the piezoelectric element 121 contracts, and the diaphragm 102 descends to expand the volume of the liquid chamber 106. Then, the ink flows into the liquid chamber 106, and then the voltage applied to the piezoelectric element 121 is increased to extend the piezoelectric element 121 in the stacking direction, and the diaphragm 102 is deformed in the direction of the nozzle 104. By contracting the volume, the recording liquid in the liquid chamber 106 is pressurized, and droplets of the recording liquid are ejected (jetted) from the nozzle 104.

  Then, by returning the voltage applied to the piezoelectric element 121 to the reference potential, the diaphragm 102 is restored to the initial position, and the liquid chamber 106 expands to generate a negative pressure. The recording liquid is filled in 106. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (pulling-pushing), and it is also possible to perform striking or pushing depending on the direction to which the driving waveform is given.

Next, an outline of the control unit of the image forming apparatus will be described with reference to the block diagram of FIG.
In the control unit 200, the CPU 201 that controls the entire apparatus, the ROM 202 that stores programs executed by the CPU 211 and other fixed data, the RAM 203 that temporarily stores image data and the like, and the power supply of the apparatus are cut off. A rewritable non-volatile memory 204 for holding data in between, an image processing for performing various signal processing and rearrangement on image data, and an ASIC 205 for processing input / output signals for controlling the entire apparatus. ing.

  The control unit 200 also includes an I / F 206 for transmitting and receiving data and signals to and from the host, data transfer means for driving and controlling the recording head 7, and drive waveform generation means for generating a drive waveform. A print control unit 207; a head driver (driver IC) 208 for driving the recording head 7 provided on the carriage 3 side; a motor driving unit 210 for driving the main scanning motor 4 and the sub-scanning motor 31; An AC bias supply unit 212 that supplies an AC bias to the roller 34, I / O 213 for inputting detection signals from encoder sensors 43 and 35, detection signals from various sensors such as a temperature sensor that detects environmental temperature, and the like It has. The control unit 200 is connected to an operation panel 214 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 200 transmits image data from the host side such as an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, etc. via an I / F 206 via a cable or a network. Receive.

  Then, the CPU 201 of the control unit 200 reads and analyzes the print data in the reception buffer included in the I / F 206, performs necessary image processing, data rearrangement processing, and the like in the ASIC 205, and this image data is head-driven. The data is transferred from the control unit 207 to the head driver 208. Note that the generation of dot pattern data for outputting an image is performed by a printer driver on the host side as will be described later.

  The print control unit 207 transfers the above-described image data to the head driver 208 as serial data, and transmits a transfer clock, a latch signal, a droplet control signal (mask signal), and the like necessary for the transfer of the image data and confirmation of the transfer. In addition to the output to the head driver 208, a drive waveform generator and a head driver composed of a D / A converter, a voltage amplifier, a current amplifier, etc. for D / A converting the pattern data of the drive signal stored in the ROM Drive waveform selection means for generating a drive waveform composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal) and outputting the drive waveform to the head driver 208.

  The head driver 208 selectively selects droplets of the recording head 7 based on image data corresponding to one line of the recording head 7 input serially, and forms a driving signal provided from the print control unit 207. The recording head 7 is driven by applying it to a driving element (for example, a piezoelectric element as described above) that generates energy to be discharged. At this time, by selecting a driving pulse constituting the driving waveform, for example, dots having different sizes such as large droplets (large dots), medium droplets (medium dots), and small droplets (small dots) can be distinguished. it can.

  Further, the CPU 201 detects a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 43 constituting the linear encoder, and a speed target value and a position target value obtained from a previously stored speed / position profile. Based on this, a drive output value (control value) for the main scanning motor 4 is calculated, and the main scanning motor 4 is driven via the motor driving unit 210. Similarly, based on the speed detection value and position detection value obtained by sampling the detection pulse from the encoder sensor 35 constituting the rotary encoder, and the speed target value and position target value obtained from the previously stored speed / position profile. Then, a drive output value (control value) for the sub-scanning motor 31 is calculated, and the sub-scanning motor 31 is driven via the motor driver 210 and the motor driver.

Next, an example of the print control unit 207 and the head driver 208 will be described with reference to FIG.
As described above, the print control unit 207 generates a drive waveform (common drive waveform) composed of a plurality of drive pulses (drive signals) within one printing cycle, and outputs a print waveform. And a data transfer unit 302 that outputs a clock signal, a latch signal (LAT), and droplet control signals M0 to M3.

  The droplet control signal is a 2-bit signal that instructs each droplet to open and close an analog switch 317, which will be described later, of the head driver 208. The droplet control signal is a waveform to be selected according to the printing cycle of the common drive waveform. State transition is made to level (ON), and state transition is made to L level (OFF) when not selected.

  The head driver 208 receives a transfer clock (shift clock) and serial image data (gradation data: 2 bits / CH) from the data transfer unit 302, and each register value of the shift register 311 by a latch signal. A latch circuit 312 for latching, a decoder 313 that decodes gradation data and control signals M0 to M3 and outputs the result, and a logic level voltage signal of the decoder 313 is converted to a level at which the analog switch 315 can operate. Level shifter 314, and an analog switch 316 that is turned on / off (opened / closed) by the output of the decoder 313 provided via the level shifter 314.

  The analog switch 316 is connected to the selection electrode (individual electrode) 154 of each piezoelectric element 121, and the common drive waveform from the drive waveform generation unit 301 is input thereto. Accordingly, when the analog switch 316 is turned on in accordance with the result of decoding the serially transferred image data (gradation data) and the control signals MN0 to MN3 by the decoder 313, a required drive signal constituting the common drive waveform is obtained. Passing (selected) is applied to the piezoelectric element 121.

Here, ink that is a recording liquid used in the image forming apparatus will be described. The recording liquid has the following configurations (1) to (10).
(1) Pigment (self-dispersing pigment) 6 wt% or more (2) Wetting agent 1
(3) Wetting agent 2
(4) Water-soluble organic solvent (5) Anion or nonionic surfactant (6) Polyol or glycol ether having 8 or more carbon atoms (7) Emulsion (8) Preservative (9) pH adjuster (10) Pure water

  That is, a pigment is used as a colorant for printing (recording), and a solvent for decomposing and dispersing it is an essential component, and further additives are wetting agents, surfactants, emulsions, preservatives, pH. Contains a conditioning agent. The reason why the humectant 1 and the humectant 2 are mixed is to make use of the characteristics of the humectant and to easily adjust the viscosity.

Hereinafter, each of the ink components will be described more specifically.
Regarding the pigment of (1), inorganic pigments and organic pigments can be used without any particular limitation. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments). , Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like.

  According to a preferred embodiment of the ink, among these pigments, those having good affinity with water are preferably used. The particle diameter of the pigment is preferably 0.05 μm to 10 μm, more preferably 1 μm or less, and most preferably 0.16 μm or less. The amount of pigment added as a colorant in the ink is preferably about 6 to 20% by weight, more preferably about 8 to 12% by weight.

Specific examples of the pigment preferably used for the ink include the following.
For black, carbon black (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, channel black, or metals such as copper, iron (CI Pigment Black 11), titanium oxide, aniline black (CI And organic pigments such as CI Pigment Black 1).

  Further, for color use, CI pigment yellow 1 (fast yellow G), 3, 12 (disazo yellow AAA), 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55 81, 83 (Disazo Yellow HR), 95, 97, 98, 100, 101, 104, 408, 109, 110, 117, 120, 138, 153, CI Pigment Orange 5, 13, 16, 17, 36, 43 51, CI Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B ( Ca)), 48: 3 (permanent red 2B (Sr)), 48: 4 (permanent red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G Lake), 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, CI pigment violet 1 (rhodamine lake), 3 5: 1, 16, 19, 23, 38, CI pigment blue 1, 2, 15 (phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63, CI pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like.

  Other pigment pigments (eg carbon) treated with resin, etc., can be dispersed in water, and pigments (eg carbon) can be dispersed in water by adding functional groups such as sulfone groups and carboxyl groups to the surface. Processed pigments can be used.

  Further, a pigment may be included in a microcapsule so that the pigment can be dispersed in water.

  According to a preferred aspect of the ink, the pigment for black ink is preferably added to the ink as a pigment dispersion obtained by dispersing the pigment in an aqueous medium with a dispersant. As a preferable dispersing agent, a known dispersion used for preparing a conventionally known pigment dispersion can be used.

Examples of the dispersion include the following.
Polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Polymer, styrene-acrylic acid-alkyl acrylate ester copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic Acid copolymer-alkyl acrylate ester copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate -Maleate ester copolymer, vinyl acetate- Examples include crotonic acid copolymers and vinyl acetate-acrylic acid copolymers.

  According to a preferred embodiment of the ink, these copolymers preferably have a weight average molecular weight of 3,000 to 50,000, more preferably 5,000 to 30,000, most preferably 7,000 to 15. 1,000. The addition amount of the dispersant may be appropriately added as long as the pigment is stably dispersed and other effects are not lost. The dispersant is preferably in the range of 1: 0.06 to 1: 3, more preferably in the range of 1: 0.125 to 1: 3.

  The pigment used for the colorant is a particle having a particle size of 0.05 to 0.16 μm, containing 6 to 20% by weight based on the total weight of the recording ink, and is dispersed in water by a dispersant. The dispersant is a polymer dispersant having a molecular weight of 5,000 to 100,000. When at least one water-soluble organic solvent is a pyrrolidone derivative, particularly 2-pyrrolidone, the image quality is improved.

  Regarding the wetting agents 1 and 2 and the water-soluble organic solvent (2) to (4), in the case of ink, water is used as a liquid medium in the ink. For example, the following water-soluble organic solvents are used for the purpose of preventing the above-described problem and improving the dissolution stability. A plurality of these water-soluble organic solvents may be used in combination.

Specific examples of the wetting agent and the water-soluble organic solvent include the following.
Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerol, Polyhydric alcohols such as 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, petriol;

  Polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether;

  Polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether;

  Nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone;

  Amides such as formamide, N-methylformamide, N, N-dimethylformamide;

  Amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine;

Sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, thiodiethanol;
Propylene carbonate, ethylene carbonate and the like.

  Among these organic solvents, diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1,5-pentane Diol, 2-pyrrolidone and N-methyl-2-pyrrolidone are preferred. These are excellent in solubility and prevention of poor jetting characteristics due to water evaporation.

  The other wetting agent preferably contains sugar. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, Examples include lactose, sucrose, trehalose, and maltotriose. Here, the polysaccharide means a saccharide in a broad sense, and is used to mean a substance widely existing in nature such as α-cyclodextrin and cellulose.

  Examples of derivatives of these saccharides include reducing sugars of the saccharides described above (for example, sugar alcohols (represented by the general formula HOCH2 (CHOH) nCH2OH (where n is an integer of 2 to 5))). Oxidized sugars (for example, aldonic acid, uronic acid, etc.), amino acids, thioic acids, etc. Particularly preferred are sugar alcohols, and specific examples include maltitol, sorbit and the like.

  The content of these saccharides is suitably 0.1 to 40% by weight, preferably 0.5 to 30% by weight of the ink composition.

  The surfactant (5) is not particularly limited, but examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, and polyoxyethylene alkyl ether sulfate. Examples include salt.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, polyoxyethylene alkyl amides, and the like. Can be mentioned. The surfactants can be used alone or in combination of two or more.

  The surface tension in the ink is an index indicating the permeability to paper, and in particular shows the dynamic surface tension in a short time of 1 second or less after the surface is formed, and is different from the static surface tension measured by the saturation time. Any measuring method can be used as long as it can measure a dynamic surface tension of 1 second or less by a conventionally known method described in JP-A-63-31237 or the like. In the present invention, a Wilhelmy type suspension is used. It measured using the plate type surface tension meter. The surface tension value is preferably 40 mJ / m 2 or less, and more preferably 35 mJ / m 2 or less, whereby excellent fixing properties and drying properties can be obtained.

  For (6) polyols or glycol ethers having 8 or more carbon atoms, partially water-soluble polyols and / or glycol ethers having a solubility of less than 0.1 to 4.5% by weight in water at 25 ° C. By adding 0.1 to 10.0% by weight with respect to the total weight of the recording ink, the wettability of the ink to the thermal element is improved, and ejection stability and frequency stability can be obtained even with a small addition amount. I found out that (A) 2-ethyl-1,3-hexanediol Solubility: 4.2% (20 ° C.) (B) 2,2,4-trimethyl-1,3-pentanediol Solubility: 2.0% (25 ° C.) .

  A penetrant having a solubility of less than 0.1-4.5% by weight in water at 25 ° C. has the advantage of very high permeability instead of low solubility. Therefore, an ink having a very high permeability in a combination of a penetrant having a solubility of less than 0.1 to 4.5% by weight in water at 25 ° C. with another solvent or another surfactant. Can be produced.

  (7) It is preferable that a resin emulsion is added to the ink. The resin emulsion means an emulsion in which the continuous phase is water and the dispersed phase is the following resin component. Examples of the resin component in the dispersed phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, and styrene resins.

  According to a preferred embodiment of the ink, the resin is preferably a polymer having both a hydrophilic part and a hydrophobic part. The particle size of these resin components is not particularly limited as long as an emulsion is formed, but is preferably about 150 nm or less, more preferably about 5 to 100 nm.

  These resin emulsions can be obtained by mixing resin particles in water, optionally with a surfactant. For example, an acrylic resin or styrene-acrylic resin emulsion can be obtained by adding (meth) acrylic acid ester or styrene, (meth) acrylic acid ester, and optionally (meth) acrylic acid ester, and a surfactant to water. It can be obtained by mixing. The mixing ratio of the resin component and the surfactant is usually preferably about 10: 1 to 5: 1. When the amount of the surfactant used is less than the above range, it is difficult to form an emulsion, and when it exceeds the above range, the water resistance of the ink tends to be lowered or the penetrability tends to deteriorate.

  The ratio of the resin as the dispersed phase component of the emulsion and water is 60 to 400 parts by weight, preferably 100 to 200 parts by weight with respect to 100 parts by weight of the resin.

  Commercially available resin emulsions include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd .: both trade names), Boncoat 4001 (acrylic resin emulsion, Dainippon Ink & Chemicals, Inc.) Company: trade name), Boncoat 5454 (styrene-acrylic resin emulsion, Dainippon Ink and Chemicals Co., Ltd .: trade name), SAE-1014 (styrene-acrylic resin emulsion, made by Nippon Zeon Co., Ltd .: trade name) , Cybinol SK-200 (acrylic resin emulsion, manufactured by Syden Chemical Co., Ltd .: trade name), and the like.

  The ink preferably contains a resin emulsion such that the resin component is 0.1 to 40% by weight of the ink, more preferably 1 to 25% by weight.

  The resin emulsion has the property of thickening and aggregating, has the effect of suppressing the penetration of the coloring components, and further promoting the fixing to the recording material. Further, depending on the type of resin emulsion, a film is formed on the recording material, and the printed material has an effect of improving the abrasion resistance.

(8) to (10) In addition to the colorant, solvent and surfactant, conventionally known additives can be added to the ink.
For example, as a preservative and antifungal agent, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol and the like can be used.

  As the pH adjuster, any substance can be used as long as the pH can be adjusted to 7 or more without adversely affecting the ink to be prepared. Examples thereof include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium. Examples thereof include carbonates of alkali metals such as hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate.

  Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Thus, even when printing on plain paper by using an ink composition comprising at least a pigment, a water-soluble organic solvent, a polyol or glycol ether having 8 or more carbon atoms, and water, (1) good color tone ( (2) High image density, (3) Clear image quality without feathering or color bleeding on characters / images, (4) Ink back that can withstand double-sided printing It is possible to achieve an image with little missing phenomenon, (5) high image dryness (fixability) suitable for high-speed printing, and (6) high image quality with high fastness such as light resistance and water resistance. Density, color developability, color reproducibility, character bleeding, color boundary bleeding, double-sided printing property, fixing property, etc. can be greatly improved.

Next, an example of a drive waveform preferable when such ink is used will be described with reference to FIGS.
As shown in FIG. 7, the drive waveform generator 301 is fair within one printing cycle (one drive cycle), such as a waveform element that falls from the reference potential Ve and a waveform element that rises from the state after the fall. A drive signal (drive waveform) composed of eight drive pulses P1 to P8 is generated and output. On the other hand, the driving pulse to be used is selected by the droplet control signals M0 to M3 from the data transfer unit 302.

  Here, the waveform element in which the potential V of the drive pulse falls from the reference potential Ve is a drawing waveform element in which the piezoelectric element 121 contracts and the volume of the pressurized liquid chamber 106 expands. Further, the waveform element that rises from the state after the fall is a pressurizing waveform element that causes the piezoelectric element 121 to expand and the volume of the pressurized liquid chamber 106 to contract.

  Then, when forming a small droplet (small dot) by the droplet control signals M0 to M3 from the data transfer unit 302, the drive pulse P1 is selected as shown in FIG. 8A to form a medium droplet (medium dot). When driving, the driving pulses P4 to P6 are selected as shown in FIG. 8B, and when forming large droplets (large dots), the driving pulses P2 to P8 are selected as shown in FIG. When the meniscus is vibrated without droplet ejection, the fine drive pulse P2 is selected as shown in FIG. 8D and applied to the piezoelectric element 121 of the recording head 7 respectively.

  When forming a medium droplet, the first droplet is ejected by the drive pulse P4, the second droplet is ejected by the drive pulse P5, and the third droplet is ejected by the drive pulse P6. At this time, if the natural vibration period of the pressure chamber (liquid chamber 106) is Tc, the interval between the ejection timings of the drive pulses P4 and P5 is preferably 2Tc ± 0.5 μs. Since the drive pulses P4 and P5 are configured by simple strike waveform elements, if the drive pulse P6 is also set to the same simple strike waveform element, the ink droplet velocity becomes too large, and the landing positions of other droplet types are affected. There is a risk of shifting. Therefore, the drive pulse P6 reduces the pull-in voltage (decreasing the falling potential) to reduce the meniscus pull-in and suppress the ink drop speed of the third drop. However, the startup voltage is not reduced in order to increase the necessary ink droplet volume.

  That is, in the drawing waveform element of the final drive pulse among the plurality of drive pulses, by reducing the drawing voltage relatively, the droplet discharge speed by the final drive pulse is relatively reduced, and the landing position is set to other droplets. It can be combined with the seed as much as possible.

  The fine drive pulse P2 is a drive waveform that vibrates the meniscus without ejecting ink droplets in order to prevent drying of the meniscus of the nozzle. This fine driving pulse P2 is applied to the recording head 7 in the non-printing area. In addition, by using the drive pulse P2 which is the fine drive waveform as one of the drive pulses constituting the large droplet, it is possible to achieve a shortened (higher speed) drive cycle.

  Furthermore, by setting the interval between the ejection timings of the fine drive pulse P2 and the drive pulse P3 within the range of the natural vibration period Tc ± 0.5 μs, the volume of ink droplets ejected by the drive pulse P3 can be increased. In other words, by superimposing the expansion of the pressurized liquid chamber 6 by the drive pulse P3 on the pressure vibration of the pressurized liquid chamber 106 by the vibration cycle generated by the fine drive pulse P2, the droplet volume of the droplet that can be ejected by the drive pulse P3 is driven. It can be made larger than when applying P3 alone.

  Since the required drive waveform differs depending on the viscosity of the ink, in this image forming apparatus, as shown in FIG. 9, the drive waveform when the ink viscosity is 5 mPa · s, the same when the viscosity is 10 mPa · s. A drive waveform, similarly a drive waveform at 20 mPa · s, is prepared, and the ink viscosity is determined from the temperature detected by the temperature sensor, and the drive waveform to be used is selected.

  That is, when the ink viscosity is small, the voltage of the drive pulse is relatively small, and when the ink viscosity is large, the voltage of the drive pulse is relatively large. The volume can be discharged substantially constant. Further, the driving pulse 2 can vibrate the meniscus without ejecting ink droplets by selecting the peak value according to the ink viscosity.

  By using a drive waveform composed of such drive pulses, it is possible to control the time until each large, medium, and small droplet lands on the paper, and the ejection start time differs for each large, medium, and small droplet. In addition, each drop can be landed at substantially the same position.

  Next, an image forming method according to the present invention for outputting a print image by the above image forming apparatus and an image processing apparatus in which a program according to the present invention is installed in a computer and the image forming apparatus will be described below.

Next, an example of an image forming system according to the present invention constituted by the image processing apparatus according to the present invention and the above-described ink jet printer (ink jet recording apparatus) as the image forming apparatus will be described with reference to FIG.
This printing system (image forming system) is configured by connecting one or a plurality of image processing apparatuses 400 including a personal computer (PC) or the like and an inkjet printer 500 via a predetermined interface or network.

  As shown in FIG. 11, in the image processing apparatus 400, a CPU 401 and various ROMs 402 and RAM 403, which are memory means, are connected by a bus line. The bus line is connected to a storage device 406 using a magnetic storage device such as a hard disk, an input device 404 such as a mouse and a keyboard, a monitor 405 such as an LCD or a CRT, and the like via a predetermined interface. A storage medium reading device for reading a storage medium such as an optical disk is connected, and a predetermined interface (external I / F) 407 for communicating with a network such as the Internet or an external device such as a USB is connected.

  An image processing program including a program according to the present invention is stored in the storage device 406 of the image processing apparatus 400. This image processing program is installed in the storage device 406 by being read from a storage medium by a storage medium reader or downloaded from a network such as the Internet. With this installation, the image processing apparatus 400 becomes operable to perform the following image processing. Note that this image processing program may operate on a predetermined OS. Further, it may be a part of specific application software.

  The image processing method according to the present invention can also be performed on the ink jet printer side, but here, on the ink jet recording apparatus side, a dot pattern that is actually recorded upon receiving an image drawing or character print command in the apparatus. An example that does not have a function for generating the error will be described. That is, a print command from application software or the like executed by the image processing apparatus 400 serving as a host is subjected to image processing by the printer driver according to the present invention incorporated as software in the image processing apparatus 400 (host computer), and then an inkjet printer. An example in which multi-value dot pattern data (print image data) that can be output by 500 is generated, rasterized, transferred to the inkjet printer 500, and the inkjet printer 500 is printed out will be described.

  Specifically, in the image processing apparatus 400, an image drawing or character recording command from an application or operating system (for example, a description of the position and thickness and shape of a line to be recorded, a typeface of a character to be recorded, and the like) (Which describes the size, position, etc.) is temporarily stored in the drawing data memory. Note that these instructions are written in a specific print language.

  The command stored in the drawing data memory is interpreted by the rasterizer, and if it is a line recording command, it is converted into a recording dot pattern according to the designated position and thickness, etc. If there is image data, the outline information of the corresponding character is called from the font outline data stored in the image processing apparatus (host computer) 400 and converted into a recording dot pattern corresponding to the designated position and size. This is converted into a recording dot pattern as it is.

  Thereafter, these recorded dot patterns (image data) are subjected to image processing and stored in a raster data memory. At this time, the image processing apparatus 400 rasterizes the recording dot pattern data with the orthogonal grid as the basic recording position. Examples of the image processing include color management processing (CMM) for adjusting colors, γ correction processing, halftone processing such as dithering and error diffusion, further background removal processing, and total ink amount regulation processing. The recording dot pattern stored in the raster data memory is transferred to the ink jet recording apparatus 500 via the interface.

Therefore, thickening (boldening) that thickens an image (in the following, description will be made using characters as an example) will be described with reference to FIG.
First, an output example when the bolding process is not performed is shown in FIG. 12, and a partially enlarged view of the dot size is shown in FIG. In this embodiment, the case where the resolution is different between the main scanning direction and the sub scanning direction is shown, and the resolution of the image is formed at the same resolution as the nozzle pitch (300 dpi in this example) in the sub scanning direction. Are formed at a higher density than in the sub-scanning direction (in this example, 600 dpi which is twice the sub-scanning direction). In FIG. 13, since the main scanning direction has twice the resolution of the sub-scanning direction, two dots in the main scanning direction correspond to one dot in the sub-scanning direction. The direction is enlarged twice as much as the sub-scanning direction (the same applies hereinafter). In addition, the character image portion is indicated by a filled circle, and the background portion is indicated by a white circle (the same applies hereinafter).

  On the other hand, FIG. 14 shows a partially enlarged view of the dot size when the bolding process according to the present invention is performed. That is, as shown in FIG. 14, 1 dot in the sub-scanning direction, 1 dot in the main scanning direction, and a large (large) dot Dp are added to the dots in the blank area adjacent to the dots forming the image portion. Yes. As a result, the characters become thicker, the characters that are too thin can be made thicker, and characters with high visibility can be printed, improving the character quality.

  Further, FIG. 15 shows a partially enlarged view of another example dot size. In this example, a large (large) dot Dpl is added to a blank dot adjacent to a dot forming an image portion in the main scanning direction with a relatively high resolution (for example, 600 dpi), and the resolution is relatively In the low (for example, 300 dpi) sub-scanning direction, medium dots (relatively smaller than large drops) dots Dpm are added to the blank dots adjacent to the dots forming the image portion.

  Since the image forming apparatus can form large drops (large dots), medium drops (medium dots), and small drops (small dots), small drops can be added instead of medium drops.

  As in the example of FIG. 15, by changing the size (dot size) of the dot to be added according to the resolution, an appropriate weighting method is realized when the dot is added to the coarse resolution and the dot is overweight. be able to.

Therefore, a process for thickening characters will be specifically described.
As a method of adding large droplets beside or below the dots forming the characters, it is excellent in that pattern matching can be processed at high speed. FIG. 16 is an example of a window used for pattern matching. The window size is a size of horizontal m and vertical n (m × n). Here, m and n are the same value, and as shown in FIG. 17, an example performed in a window with m = 3 and n = 3 will be described.

  The font data is expanded into bitmap data by printer driver software. Bitmap data indicates the dots forming the font. For bit map data as font data, each bit is subjected to pattern matching in the aforementioned window unit.

An example of pattern matching processing (bold text processing) executed by the printer driver will be described with reference to FIG.
First, the target pixel is set at the head of the font data. Bitmap data of font data corresponding to the window is acquired with the pixel of interest at the center. In this case, the acquired bitmap data is 3 × 3 data for 9 dots. By pattern matching, the acquired data is compared with the data of a pattern (hereinafter referred to as “reference pattern”) to which an image dot set in advance is set. ) Is replaced with image dot data.

  In these processes, one pixel may be handled as 1-byte data or 1-bit data. When handling as 1-byte data, 9 bytes are required to represent 9-dot data, whereas when handling as 1-bit data, 2-byte data is required to represent 9-dot data. Since the amount is sufficient, it is preferable to handle the data as 1-bit data because the number of data to be processed is small, the memory can be saved, and the processing speed can be improved.

An example of this pattern matching will be specifically described with reference to FIGS.
An example of the reference pattern of Drawing 19 (a)-(c) is shown. When pattern matching is performed with the font data shown in FIG. 20A using this reference pattern, as shown in FIG. 20A, the pixel position (dot position) D45 of the font data is the target pixel. Since the state of the dots included in the window W matches the reference pattern shown in FIG. 19C, the target pixel D45 is replaced from blank data to image dot data as shown in FIG. 20B. .

  Similarly, when the window W moves to the right and the target pixel becomes D46, it matches the reference pattern in FIG. 19B, so that the target pixel D46 is replaced with the image dot data from the blank data. Further, when the window W further moves to the right and the target pixel becomes D47, it matches the reference pattern of FIG. 19A, so that the target pixel D47 is replaced from blank data to image dot data. .

  In the generation of image dot data, when the original font data is represented by 0 (blank) and 255 (print data) as the bitmap data, “0” indicating blank data is displayed as the image dot data. It is changed to “255” indicating dot data. In addition, when represented by binary values such as 0 (blank) and 1 (print data), “0” indicating blank data is changed to “1” indicating print data.

  Font data composed of data indicating large droplets generated by pattern matching (in the former case), or binary (0, 1) data for small droplets and original binary (0, 1) font data (in the latter case) ), Printing large droplets (or medium or small droplets) makes it possible to realize thick characters.

  In the above specific example, an example is described in which large dots are added in the sub-scanning direction as shown in FIG. 14, but medium drops (or small drops) are added in the sub-scanning direction shown in FIG. When adding dots and adding large droplets in the main scanning direction, the sub-scanning direction and the main scanning direction are separately created as reference patterns, and pattern matching is performed similarly. Image dots of different sizes can be added (replaced) in the main scanning direction and the sub-scanning direction.

Next, as a method for thickening, a method for thickening characters by thickening and further performing jaggy correction for the stepped change will be described.
As described above, pattern matching can be processed at high speed as a method of adding small droplets, medium droplets, or large droplets beside or below the dots forming the characters. As described above, the window size is a size of horizontal m and vertical n (m × n), but here, jaggy correction is performed on a diagonal line close to a line parallel to the main scanning direction and parallel to the sub-scanning direction. Since the jaggy correction is not performed on the oblique line close to the straight line, m and n have different values. That is, m is large so that a diagonal staircase change point close to the horizontal line and a blank dot in the vicinity thereof can be detected, and conversely, it is not necessary to detect the vicinity of the diagonal staircase change point close to the vertical line. Small value. Here, this is performed using a window with m = 9 and n = 3.

  The processing in this case will be described with reference to FIG. 21. When the pixel of interest is blank data, bitmap data of font data corresponding to the window is acquired around the pixel of interest. Therefore, the acquired bitmap data is 9 × 3 27 dot data. By pattern matching, the acquired data is compared with data of a reference pattern to which a small droplet set in advance is added or replaced, and when there is a match, the pixel of interest is replaced with data indicating a small droplet.

  In these processes, one pixel may be handled as 1-byte data or 1-bit data. When handling as 1-byte data, 27 bytes are required to represent 27-dot data, whereas when handling as 1-bit data, 4-byte data is required to represent 27-dot data. Since the amount is sufficient, it is preferable to handle the data as 1-bit data because the number of data to be processed is small, the memory can be saved, and the processing speed can be improved.

  An example of pattern matching in which only jaggy correction is performed will be described in detail with reference to FIGS. When pattern matching is performed with the pattern shown in FIG. 23 using the reference patterns shown in FIGS. 22A to 22E, as shown in FIG. 23A, when the dot D46 of the font data is the target pixel, Since the patterns of the two dots match, as shown in FIG. 23B, the position of the target pixel D46 is replaced from a blank dot to a small droplet image dot.

  Also in this case, as described above, in the generation of small droplet data, the data indicating the small droplet is when the original font data is represented by 0 (blank) and 255 (print data) like bitmap data. , Or 0 (blank), 1 (print data), and binary data, and once converted to 0 (blank) and 255 (print data), the blank data and the data forming the font It may be replaced with data representing small drops (eg 85 each). When processing with 0 and 1 as it is, another memory (small droplet data memory) having the same size as the font data is provided, and “1” representing the print data is generated at the position where the small droplet is placed. . Font data composed of data indicating small drops and large drops generated by pattern matching (in the former case), or binary (0, 1) data for small drops and original binary (0, 1) font data In the latter case, bold characters can be realized by printing small droplets and large droplets.

  In this way, by using a 9 × 3 window and a reference pattern, it becomes a small drop with respect to a space of 4 dots before and after the change point (blank and image dots when all dots are the target pixel). Whether or not to replace can be determined. The reason why it can be applied to the four dots before and after the change point is that, for example, the change point is outside the window when the position of the dot De in FIG. It is. In order to solve this problem and add a small droplet to the position of the dot De, it is possible to make the window and the reference pattern 11 × 3 in size.

  That is, by increasing the size of the window and the size of the reference pattern, it is possible to detect the change point of the diagonal line near horizontal or vertical, and it is possible to add small droplets according to the inclination, and to improve the quality of the diagonal line. It can be made even more optimal. In other words, as described above, the size of the window and the reference pattern is not limited to that used in the above example, but depends on how much replacement with a small drop needs to be performed and whether the processing time is in time for the printing speed. Determined. Furthermore, since the data for pattern matching increases as this size increases, time is required for pattern matching. Therefore, from the processing time, the size should be as small as possible. On the other hand, how many dots before and after the change point should be made into small droplets is determined by the character quality by jaggy correction, so it is necessary to determine an optimum size from the processing speed and the character quality.

  According to the experiments of the present inventor, when the ink as described above is used, the character quality is sufficiently improved even by adding a small drop of 4 dots, preferably 6 dots, because the unevenness with the adjacent dots is reduced due to the spread of the ink. It was found that the throughput could be achieved, and the processing speed was also able to achieve a throughput of 10 PPM or more. Therefore, as the window size, m ≦ 13 in which 6 dots can be detected in the main scanning direction and n = 3 in the sub scanning direction are suitable.

  Next, another example of bolding will be described with reference to FIGS. In these examples, small droplets and medium droplets are used as small droplets, and the number of added dots is different. In any of the drawings, the pitch of adjacent dots expressed at equal intervals is 600 dpi in the main scanning direction and 300 dpi in the sub-scanning direction on the actual paper surface.

  The example shown in FIG. 24 is an example in which small droplets (D61, D71) are added to the blank portion of 1 dot before the change point, and the example shown in FIG. 25 is the medium droplet (D61) in the blank portion of 2 dots before the change point. , D71) and small droplets (D60, D72), the example shown in FIG. 26 is a medium dot (D61, D71) and small droplets (D60, D59, D72, In the example shown in FIG. 27, medium drops (D61, D60, D71, D72) and small drops (D59, D58, D72, D73) were added to the blank area of 4 dots before the change point. It is an example.

  In addition, in the example shown in FIGS. 28 to 31, after adding small droplets (D61 to D58, D71 to D74) to the blank area of 4 dots before the change point, the example shown in FIG. In the example in which the 1-dot character portion is replaced with a medium drop (D62, D70), the example shown in FIG. 29 is the medium drop (D62, D70) and the small drop (D63, D69) in the 2-dot character portion after the change point. 30, the example shown in FIG. 30 is an example in which the 3-dot character portion after the change point is replaced with a medium drop (D62, D63, D70, D69) and a small drop (D64, D68), as shown in FIG. 31. In the example, the 4-dot character part after the change point is replaced with a medium drop (D62, D63, D70, D69) and a small drop (D64, D65, D68, D67).

  As described above, jaggy correction is performed on the step-like change portion, and a blank portion adjacent to other characters (for example, the portion of the dot De in FIG. 23) is changed to a thick character by the pattern of FIG. Was made to do.

  The inventors of the present invention created characters using these eight types of methods, and evaluated the improvement in visibility and the inconspicuousness of jaggies as a result of thickening. As a result, 4 dots were used for the blank dots before the change point. It has been found that it is preferable to correct 2 dots or more (that is, the example of FIGS. 29 to 31) for dots forming the character portion.

  On the other hand, when compared in terms of processing speed, the example of FIG. 24 is the fastest, and is slowed down in the order of the examples of FIG. 25, FIG. For example, in the example of FIGS. 24 to 27, the processing method may be executed only when the pixel of interest is blank in the example of FIGS. 24 to 27. In the example of FIGS. This is because it is necessary to perform pattern matching both in the case of image data and in the case of image dots (that is, all font data). In other words, font data with improved jaggies can be created at high speed by adding small droplets only to blanks. Moreover, by replacing only image dots with small drops, font data with improved jaggy can be created at high speed, but this is not desirable when bolding.

  Secondly, the number of necessary reference patterns increases in the order of the examples in FIGS. 24, 25,... This is because, in order to implement the example of FIG. 25, a reference pattern for determining the second blank dot is necessary in addition to the reference pattern of the example of FIG. 24, and in the example shown in FIG. This is because a reference pattern for determining the second dot is necessary, and in the example shown in FIG. 29, a reference pattern for determining the second dot is further required. Thus, as the example shown in FIG. 24 is followed from the example shown in FIG. 31, the number of reference patterns for determination increases, and the number of pattern matching increases.

Here, an example in which pattern matching is performed on a blank portion and an image portion will be described with reference to FIG.
For bit map data as font data, each bit is subjected to pattern matching in the aforementioned window unit. First, the target pixel is set at the head of the font data. Then, the bitmap data of the font data corresponding to the window is acquired around the target pixel. In this case, when the 9 × 3 size window described above is used, data for 27 dots is acquired. By pattern matching, the acquired data is compared with the preset reference pattern data to add or replace small droplets and medium droplets. If there is a match, the pixel of interest is converted into data indicating small or medium droplets. Replace.

  In these processes, one pixel may be handled as 1-byte data or 1-bit data. When handling as 1-byte data, 27 bytes are required to represent 27-dot data, whereas when handling as 1-bit data, 4-byte data is required to represent 27-dot data. Since the amount is sufficient, it is preferable to handle the data as 1-bit data because the number of data to be processed is small, the memory can be saved, and the processing speed can be improved.

  At this time, the data indicating small droplets and medium droplets are displayed when the original font data is represented by 0 (blank) and 255 (print data) like bitmap data, or 0 (blank), 1 (print data). ), And once converted to 0 (blank) and 255 (print data), the data forming the font itself is data representing small droplets and medium droplets (for example, They may be replaced with 85 and 170, respectively. In addition, when processing with 0 and 1, a plurality of different memories having the same size as the font data (here, two types of small droplets and medium droplets, two for small droplets and two for medium droplets) are provided, What is necessary is just to produce | generate "1" showing print data in the position which attaches a small drop and a middle drop in each. Font data composed of data indicating small droplets, medium droplets, and large droplets generated by pattern matching (in the former case), binary data for small droplets (0, 1), binary data for medium droplets (0, 1) By printing small droplets, medium droplets and large droplets with the data and the original font data (binary), diagonal lines with improved jaggy can be realized.

In this way, font data in which image dots were added to blank areas was actually printed on plain paper using an inkjet recording head under the following conditions, and the character quality was evaluated.
Head: 384 nozzles / color
Nozzle pitch = 84 μm (equivalent to 300 dpi)
Image resolution: main scanning direction 600 dpi, sub-scanning direction 300 dpi (= nozzle pitch)
Dot size: Large droplet 87μm, Small droplet 40μm, Medium droplet 60μm
Character: MS Mincho Font size = 6, 10, 12, 20, 30, 50, 80 points Jaggy correction method: Example of Figs. 24 to 33 Printing method: Number of passes (number of scans forming one line) = 1, interlace = None Paper: Ricoh Type 6200 (trade name)

  Table 1 shows the results of comparing the output results for the characters with the bolding process and the characters without the bolding process according to the present invention for each character size. In addition, the symbols in Table 1 indicate that xx: collapsed and inferior character quality, x: thin character, poor character quality, △: slightly thin character, ○: good character quality, and easy to read. .

  From the results shown in Table 1, it can be seen that by making the characters bold according to the present invention, the visibility of the characters is increased and the characters are easy to read, and the character quality is improved. Moreover, there was no feathering and characters with sufficient image density were obtained.

  Further, as can be seen from Table 1, it was found that the character quality deteriorates when the font size is too small. This is because, in a small-size character, the interval between the dots constituting the character is narrow, and the characters added due to the bold character are crushed. As for the size, it was found that when the size is 8 points or more, there is an extremely thickening effect.

  Here, an example of printing on plain paper is shown, but the same effect can be obtained by applying the present invention to printing on coated paper, glossy paper, OHP film, and the like. In addition, depending on the type of paper, it is possible to select whether or not to make bold fonts. This makes it possible to select the type of paper that is easy to bleed and that is difficult to bleed. It is possible to realize a large character thickness.

  Also, here, an example is shown in which characters are printed at a resolution of 600 dpi × 300 dpi, but the dot diameter constituting the characters is increased even for lower resolution characters of 400 dpi × 200 dpi, 300 dpi × 150 dpi, and the stairs Since the step of the shape is more conspicuous, the present invention can be suitably applied and the effect is great.

  On the other hand, when the resolution is high density, such as 600 dpi × 600 dpi, 600 dpi × 1200 dpi, 1200 dpi × 1200 dpi,... Therefore, in the case of an image forming apparatus having a plurality of print modes for printing at different resolutions, a mode for carrying out the present invention and a mode for not carrying out the present invention are provided depending on the resolution, and selection according to the resolution means improvement of throughput. It is preferable in terms.

An example of processing in the case of switching between a mode in which thickening processing is performed and a normal mode in which thickening processing is not performed according to the character size, character type, image resolution, and the like will be described with reference to FIG. .
In this process, when the character size is 8 points or more, the character type is Mincho, and the resolution of the image is 600 dpi × 300 dpi or less, the thickening process is performed. Note that the conditions for determining the character size, character type, and image resolution are not limited to these.

  As described above, the mode for performing the bolding process (the mode for adding dots) and the normal mode for not performing the bolding process (the mode without adding dots) are switched according to the character size, character type, and resolution. By doing so, it becomes possible to output high PPM without requiring unnecessary processing speed even in the case of high throughput.

  A plurality of types of reference patterns are prepared according to the inclination of the outline of the character, and the thickening process is changed according to the inclination of the outline of the character (position to add the image dot, size of the added dot By changing the size, it is possible to perform an optimal bolding and obtain a high-quality character.

  Furthermore, although the case where it is a character was demonstrated in the said embodiment, it can apply similarly when the image is a graphic.

  In addition, as described above, thickening is performed as part of jaggy correction, so that it is possible to cope with it simply by increasing the reference pattern, and making the characters thicker and easier to see without causing a significant decrease in processing speed. Can do. Here, FIG. 34 shows the difference in bolding using simple jaggy correction and jaggy correction. Since FIG. 34 (a) merely performs jaggy correction, only dot replacement is performed on the step-like change portion. In the present invention, as shown in FIG. 34 (b), the step-like change portion. In addition to adding dots by correcting jaggies for dots, dots can be added to non-change portions, and the characters can be fattened.

  In the image forming apparatus of the above embodiment, the recording head is described as an example of a piezoelectric head using a piezoelectric element, but as described above, a thermal type that discharges droplets by film boiling using an electrothermal conversion element. Of course, the head is also good. As described above, the piezoelectric head can eject droplets having different sizes depending on the driving waveform, and it is easy to form a gradation image. On the other hand, the thermal type head is advantageous in printing an image with high resolution at a high speed because it is easy to highly integrate nozzles.

Here, different examples of the thermal head will be described with reference to FIGS.
The head shown in FIG. 35 is an edge shooter type head, and an ejection energy generator 501 (electrodes for applying an ejection signal to the generator and a protective layer provided on the generator if necessary) is omitted. ) And a top plate 506 constituting a cover of the flow path 503 and a side wall of the flow path 503 and a wall material 505 constituting the nozzle 504. In this head, ink travels straight from the flow path 503 toward the nozzle 504 as indicated by a one-dot chain line 507.

  In this head, when a recording signal is applied to the ejection energy generator 501 through an electrode (not shown) in a state where the ink is stored in the flow path 503 from a liquid chamber (not shown) in which ink is stored, the generator 501 is applied. The discharge energy generated from the nozzles acts on the ink in the flow path 503 above the discharge energy generator 501 (discharge energy operation unit), and as a result, the ink is discharged from the nozzle 504 as droplets.

  Such an edge shooter type head has the advantage that it is extremely easy to miniaturize each part with precision, to make the nozzles multi-sized or to be miniaturized, and to increase mass productivity. On the other hand, there is a limit to the response frequency and droplet flying speed during droplet ejection. In addition, bubbles are generated in the ink due to the heat generated by the electrothermal conversion element. The bubbles contract due to a decrease in temperature, and the discharge energy generator 501 is gradually destroyed by an impact when the bubbles disappear in the vicinity of the discharge energy generator 501. The so-called cavitation phenomenon occurs, and there is a disadvantage that the lifetime is relatively short.

  The head shown in FIG. 36 is a side shooter type head, and an ejection energy generator 511 (an electrode for applying an ejection signal to the generator and a protective layer provided on the generator as needed) are omitted. ) And a nozzle plate 516 in which nozzles 514 are formed on the flow path forming member 515 are stacked. In this head, as indicated by a one-dot chain line 517, the direction of ink flow to the ejection energy operating portion in the flow path 513 is perpendicular to the opening center axis of the nozzle 514.

  With such a configuration, the energy from the ejection energy generator 511 can be more efficiently converted into the formation of ink droplets and the kinetic energy of the flight, and the meniscus can be quickly restored by supplying ink. This is advantageous and is particularly effective when a heating element is used as the discharge energy generator. In addition, a so-called cavitation phenomenon in which the discharge energy generating body is gradually destroyed by the impact when bubbles that are a problem in the edge shooter disappear can be avoided by the side shooter method. That is, in the side shooter system, when bubbles grow and reach the nozzle, the bubbles are brought into the atmosphere, and the bubbles do not contract due to a temperature drop, so the life of the head is relatively long.

  In the above embodiment, the image processing apparatus is configured such that the printer driver as the program according to the present invention causes the computer to execute the image processing method according to the present invention. Means for performing the method may also be provided. In addition, an application specific integrated circuit (ASIC) for executing the image processing method according to the present invention can be mounted on the image forming apparatus.

FIG. 3 is an explanatory side view illustrating an overall configuration of a mechanism unit of an image forming apparatus that outputs image data generated by the image processing method according to the present invention. It is principal part plane explanatory drawing of the mechanism part. FIG. 3 is an explanatory cross-sectional view along the longitudinal direction of the liquid chamber showing an example of the recording head of the apparatus. FIG. 4 is an explanatory cross-sectional view of the recording head along the lateral direction of the liquid chamber. It is a block diagram which shows the outline | summary of the control part of the apparatus. It is a block diagram which shows an example of the printing control part of the control part. It is explanatory drawing which shows an example of the drive waveform produced | generated and output by the drive waveform production | generation part of the same printing control part. It is explanatory drawing explaining each drive signal of the small droplet, medium droplet, large droplet, and fine drive selected from the same drive waveform. It is explanatory drawing explaining the drive waveform according to the recording liquid viscosity. 1 is a block diagram illustrating an example of an image forming system according to the present invention. It is a block explanatory view showing an example of an image processing device in the system. It is explanatory drawing which shows the example of an output of the character of a comparative example. It is a principal part expansion explanatory drawing in the dot size of the output example. It is principal part expansion explanatory drawing in the dot size of the example of an output of the character which performed the thickening process in this invention. It is explanatory drawing which similarly shows the other example of bolding. It is explanatory drawing of the window size used for pattern matching. It is explanatory drawing of the window size of 3x3 size. It is a flowchart with which it uses for description of a bolding process. It is explanatory drawing of the reference pattern of a 3x3 size window size with which it uses for description of the specific example of a bolding process. It is explanatory drawing with which it uses for the description at the time of similarly applying the reference pattern of FIG. It is a flowchart with which it uses for description of the other example of a bolding process. It is explanatory drawing of the reference pattern of the window size of 9x3 size similarly used for description of the specific example of a bolding process. It is explanatory drawing with which it uses for the description at the time of applying the reference pattern of FIG. 21 similarly. It is explanatory drawing with which it uses for description of the 1st example of the thickening by jaggy correction. It is explanatory drawing similarly provided to description of a 2nd example. It is explanatory drawing similarly provided to description of a 3rd example. It is explanatory drawing similarly provided to description of a 4th example. It is explanatory drawing similarly provided to description of a 5th example. It is explanatory drawing similarly provided to description of a 6th example. It is explanatory drawing similarly provided to description of a 7th example. It is explanatory drawing similarly provided to description of an 8th example. It is a flowchart with which it uses for description of the process of the 1st example thru | or 8th example of thickening by jaggy correction. It is a flowchart with which an example of a process in the case of switching the mode which performs a thickening process according to a character size, a character type, and a resolution and the mode which is not performed is provided. It is explanatory drawing with which comparison with the case where thickening by jaggy correction and jaggy correction is performed is provided. It is explanatory drawing with which it uses for description of the other example of a head. It is explanatory drawing with which it uses for description of the further another example of a head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Carriage 7 ... Recording head 207 ... Print control part 208 ... Head driver 400 ... Image processing apparatus 500 ... Inkjet printer

Claims (5)

A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. an image processing method for generating the image data of an image forming apparatus capable of forming an image at a resolution,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot . An image processing method characterized by adding dots of a size . A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In a program for causing a computer to execute processing for generating the image data of an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot. A program for causing a computer to execute processing for adding dots of size . A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In an image processing apparatus for generating the image data of an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot. An image processing apparatus comprising means for executing a process of adding a size dot . A plurality of droplets of different colors and sizes are ejected based on the image data, the first direction is the first resolution, and the direction orthogonal to the first direction is lower than the first resolution. In an image forming apparatus capable of forming an image with resolution ,
When performing image thickening processing to thicken the image by adding image dots to blank dots adjacent to the image dots forming the image,
In the first direction, a first size dot is placed on a blank dot adjacent to the image dot, and in the second direction, a second dot smaller than the first size dot is placed on a blank dot adjacent to the image dot. An image forming apparatus comprising: means for executing a process of adding a dot of a size . The image processing apparatus according to claim 3 , wherein a plurality of droplets having different colors and sizes are ejected based on image data, the first direction is a first resolution, and the direction orthogonal to the first direction is An image forming system comprising: an image forming apparatus capable of forming an image at a second resolution lower than the first resolution .