JP2008105268A - Inkjet image formation device with photocurable ink and inkjet image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet image formation device and an inkjet image forming method which can form a good image without a mottle and bleed and reduce the consumption of ink and reduce an UV irradiation energy for making an ink cured. <P>SOLUTION: In the inkjet image formation device 1 which is equipped with an inkjet recording head 11 for forming an ink pixel layer in a pixel domain on a recording medium 2 by ejecting the photocuring ink from a nozzle, an ink discharge control means for controlling the ink discharge, a movement means for moving the recording medium and/or the inkjet recording head relatively, a light irradiation means 9 for forming a pixel by curing the ink of the ink pixel layer with performing the irradiation, the ink discharge control means makes the ink pixel layer formed by adhering the ink to the two adjoining pixel domains in the longitudinal direction of the inkjet recording head 11 at a different timing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

 The present invention relates to a photocurable ink inkjet image forming apparatus that is cured by light irradiation, and an inkjet image forming method.

 Since the photocurable ink does not use a volatile solvent, it does not cause environmental pollution due to the discharge of the solvent. In addition, the ink can be instantly cured by irradiating the ink discharged onto the recording medium with light.

As an inkjet image forming apparatus using such a photocurable ink, for example, Patent Document 1 uses an ultraviolet curable ink, and applies light from a light irradiation means to ink ejected from a printer head to a printing substrate (recording medium). A technique for curing ink by ultraviolet rays to be irradiated is disclosed. In addition, as an inkjet image forming apparatus using similar photocurable ink, it controls the timing from ink ejection to UV irradiation, prevents ink dot image bleeding, character quality, dot granularity and image gradation Patent Document 2 and Patent Document 3 disclose techniques for improving the property.
JP 2001-310454 A JP 2004-291414 A JP 2004-42548 A

 In an ink jet image forming apparatus using such an ultraviolet curable ink, when an image is formed on a recording medium, the ink discharged from the ink jet recording head adheres to the recording medium and is cured by irradiation with ultraviolet light. Furthermore, the ink spreads on the surface of the recording medium. In particular, this phenomenon appears remarkably in the case of a recording medium with little ink absorption.

 In the following description of the present invention, a unit dot image constituting an image formed on a recording medium is referred to as “pixel”, and an interval between adjacent pixels is referred to as “pixel pitch”. Also, the process until the “pixel” is formed until the ink adheres to the recording medium and the ink is cured and fixed is called an “ink pixel layer” and depends on the resolution in the main scanning direction and the sub-scanning direction. The partitioned area is called a “pixel area”.

 Usually, when image formation is performed by an ink jet recording method, among the dot images formed on the recording medium, the inks of the ink pixel layers forming adjacent unit dot images come into contact with each other, and the inks of each other mix. So-called bleed may occur. In addition, this phenomenon is unlikely to occur when ink pixel layers that form adjacent unit dot images are formed at the same time or when adjacent unit dot images are formed while ink is not fixed to a recording medium. The phenomenon also causes dot image unevenness, so-called “motor”.

 Mottle refers to a state in which, when a solid image is recorded, the ink pixel layers forming adjacent unit dot images are not uniformly connected, and a gap is formed or the solid portion is non-uniform. Say.

  As a method for preventing such a bleed or mottle phenomenon, for example, in Patent Document 2, after the ink is ejected onto the recording medium, the timing of the ultraviolet irradiation and the dot diameter are adjusted to improve the mottle. However, since only the dot diameter of the unit dot image is increased, there is a problem that the amount of ink consumption increases and the image quality deteriorates.

 In Patent Document 3, ultraviolet rays are irradiated in accordance with the discharge timing of the ultraviolet curable ink discharged onto the recording medium to increase the viscosity of the ink so that the adjacent dots do not mix with each other, and thereafter, Furthermore, UV light is irradiated and cured to prevent the occurrence of mottle or bleed, thereby preventing image quality deterioration. However, this publication does not control the mixing of the ink between the dot images ejected from the adjacent nozzles of the same inkjet recording head or the size of the unit dot image of each color. In the case of forming, the cause of the occurrence of mottle has not been solved.

 The present invention provides an inkjet image forming apparatus and inkjet image recording capable of forming a good image free from the so-called mottle or bleed described above, further reducing ink consumption and UV irradiation energy for curing. It aims to provide a method.

  An ink jet recording head that ejects photocurable ink from a nozzle to form an ink pixel layer in a pixel region on the recording medium; ink ejection control means that controls ejection of the ink; and the recording medium and / or the ink jet recording. In the inkjet image forming apparatus, comprising: a moving unit that relatively moves the head; and a light irradiation unit that forms a pixel by irradiating light to cure the ink of the ink pixel layer. Ink pixel layers are formed by attaching ink to two adjacent pixel regions in the longitudinal direction of the ink jet recording head at different timings.

  A step of ejecting photocurable ink from nozzles of an ink jet recording head at a plurality of different timings to form an ink pixel layer in a pixel region on a recording medium; And a light irradiation step of curing the ink of the pixel layer to form pixels, and the ink is attached to the two adjacent pixel regions in the longitudinal direction of the inkjet recording head at different timings. After the pixel layer is formed and the shape change of one ink pixel layer is stopped, the other ink pixel layer is formed so that the area of the one ink pixel layer is larger than the area of the other ink pixel layer I tried to do it.

 According to the present invention, it is possible to form a high-quality dot image with less mottle and bleed, and it is possible to further reduce ink consumption.

 Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a diagram schematically showing each configuration of an inkjet image forming apparatus used in the practice of the present invention. The main part of the inkjet image forming apparatus 1 includes a recording medium conveying unit 3 that conveys the recording medium 2 and relatively moves the recording medium 2 and the inkjet recording heads 11 to 14, and the recording medium 2 to the recording medium conveying unit 3. Recording medium supply means 4 to be supplied; ink jet recording heads 11 to 14 that eject ink and form dot images on the recording medium 2; pre-light irradiation means 21 to 24; light irradiation means 9; And a recording medium stocker 5 for storing the recording medium 2 on which an image pattern is formed. The ink discharge control unit performs ink discharge control in accordance with the conveyance timing of the recording medium 2 by the ink jet recording head driving circuit 111. In the present embodiment, the recording medium transport unit 3 relatively moves the recording medium 2 and the ink jet recording heads 11 to 14 by the recording medium transport unit drive circuit 112.

  As the recording medium 2, a substrate made of SUS material and having a thickness of 100 μm was used. Although it will not specifically limit if it is a base material which can be printed, it selects suitably by the compatibility of a use and ink. For example, paper, wood, an OHP sheet, a resin film, metal, glass, ceramic, tile, and the like are used. Further, the shape is not limited to a planar shape, and may be a three-dimensional shape.

 A configuration of the inkjet image forming apparatus 1 that forms a pixel pattern will be described. As an ink jet recording head for ejecting ink to form an ink pixel layer on the recording medium 2, four line type ink jet recording heads 11 to 14 are arranged at predetermined intervals. The ink jet recording head 11 is shown in FIG. 2 (the same ink jet recording heads 11 to 14 are used in this embodiment). Nozzles 18 are provided at a predetermined pitch on the end surface 17 of the ink jet recording head main body 16. FIG. 3 is a cross-sectional view of the vicinity of the nozzles 18 arranged in the longitudinal direction of the ink jet recording head main body 16. An actuator 34 is provided at a position facing the nozzle 18 through the ink chamber 15. The actuator 34 includes a vibration plate 20 and a piezoelectric vibrator 19 that are attached to the tops of the partition walls 33 that partition the ink chambers 15. When a voltage is applied to the piezoelectric vibrator 19 by a drive signal, the vibration plate 20 is deformed, the pressure due to the volume change of the ink chamber 15 is transmitted to the ink in the ink chamber 15, and the ink is ejected from the nozzle 18. The arrangement pitch of the nozzles 18 is appropriately selected depending on the density of pixels to be printed. The “nozzle arrangement pitch” described below refers to “the nozzle arrangement pitch in the longitudinal direction of the inkjet recording head”.

  The recording medium conveyance unit 3 includes a conveyance belt 30, a driving roller 8, a driven roller 7, a platen roller 31, and a position detection unit 32. The drive roller 8 is driven and controlled in accordance with the ejection timing of the ink ejected from the nozzles 18 by the control signal from the recording medium transport means drive circuit 112 to transport the recording medium 2, and the inkjet recording heads 11 to 14 are recorded. The medium 2 is moved relatively. In the present embodiment, a metal endless belt having high heat resistance and low heat capacity is used as the conveying belt 30 and is arranged in a state where tension is applied between the driving roller 8 and the driven roller 7.

 The pre-light irradiation units 21 to 24 are provided behind the ink jet recording heads 11 to 14 in the conveyance direction of the recording medium 2. An acid is generated from the photoacid generator contained in the photocurable ink by light irradiated from the pre-light irradiation means to the ink pixel layer formed on the surface of the recording medium 2, and the acid is used as a catalyst for the ink component. Cross-linking polymerization is promoted to increase the viscosity of the ink, and the shape change of the ink pixel layer can be stopped early.

 The pre-irradiation can achieve the purpose as long as the change of the shape of the ink pixel layer formed on the recording medium is stopped without completely curing the ink pixel layer, and the irradiation energy may not be so large. . From the viewpoint of miniaturization of the apparatus, an ultraviolet LED lamp is preferable if the wavelength condition to be irradiated is satisfied. In this embodiment, UV-LED_NCCU33 manufactured by Nichia Corporation was used.

 In general, as the light source of the pre-light irradiation means, a light source having a wavelength capable of effectively generating an acid from a photoacid generator is selected. For example, mercury lamps such as low, medium and high pressure mercury lamps, tungsten lamps, xenon lamps, arc lamps, excimer lamps, excimer lasers, semiconductor lasers, YAG lasers, laser systems combining lasers and nonlinear optical crystals, high frequency induction An ultraviolet ray generator, an electron beam irradiation device, an X-ray irradiation device, an ultraviolet LED lamp, or the like is appropriately selected and used. In addition, when using a recording medium with large ink absorption, etc., the pre-irradiation means 21 to 24 may not necessarily be used because the ink shape change stops early.

The light irradiation means 9 is provided behind the ink jet recording heads 11 to 14 in the conveyance direction of the recording medium 2. After the ink curable ink is ejected from the ink jet recording heads 11 to 14 onto the recording medium 2 to form the ink pixel layer, the ink pixel layer is irradiated with light from the light source of the light irradiating means 9 and contained in the ink. An acid is generated from the photoacid generator, and the ink in the ink pixel layer is cured by crosslinking polymerization of the ink component using this acid as a catalyst. The irradiation light intensity at the position of the ink pixel layer surface varies depending on the wavelength of the light source used, but is usually in the range of several mW / cm ^{2 to} 10 W / cm ² . The irradiation light intensity is preferably in the range of about several tens of mW / cm ^{2 to 5} W / cm ² . The exposure amount to the ink layer is appropriately set according to the sensitivity of the ink and the conveyance speed of the recording medium 2 (relative movement speed between the light irradiation means 9 on the printing surface and the recording medium 2). In addition, the cross-linking polymerization reaction is also accelerated by heat generated with light irradiation.

 In the present embodiment, the UV irradiation system LH-6 (D bulb: peak wavelength 350 to 390 nm) manufactured by Fusion UV Systems Japan Co., Ltd. was used as the light irradiation means 9.

 As a light source for irradiating light, a light source having a wavelength capable of effectively generating an acid from a photoacid generator was selected as in the case of pre-curing. Generally, mercury lamps such as low, medium and high pressure mercury lamps, tungsten lamps, xenon lamps, arc lamps, excimer lamps, excimer lasers, semiconductor lasers, YAG lasers, lasers and nonlinear optical crystals are combined as light sources for light irradiation. A laser system, a high frequency induced ultraviolet ray generator, an electron beam irradiation device, an X-ray irradiation device, an ultraviolet LED lamp, or the like is appropriately selected and used.

 The heating unit 10 heats the ink pixel layer formed on the recording medium 2 to cure the uncured component of the ink. Even if light irradiation is performed, an uncured component may exist due to insufficient crosslinking reaction of the ink, and the heating means 10 is provided to further diffuse the acid generated in the ink by light irradiation.

 In the present embodiment, as the heating means 10, a far infrared ceramic heater PLC-32 series manufactured by Noritake Company Limited as shown in FIG. 1 is used. Usually, the heating time by the heating means 10 is 0. It is relatively short, from several seconds to several tens of seconds. Therefore, when the ink pixel layer is cured almost completely by the heating means 10, the heating is performed so that the maximum temperature reaches a relatively high temperature of, for example, about 200 ° C. or less, particularly about 80 ° C. to 200 ° C. It is. Or it is good also as a temperature range of about 60 degreeC-180 degreeC depending on the kind of ink.

 In general, an infrared lamp, a (far-infrared) halogen heater, a far-infrared ceramic heater, a roller (heat roller) incorporating a heating element, an IH heater, a blower that blows warm air or hot air, or the like is used as the heating means 10. In particular, when a metal recording medium such as stainless steel, aluminum, or copper is used in a high-speed printing apparatus with a printing speed of several tens of m / min, the surface temperature of the recording medium needs to be instantaneously heated. A non-contact type condensing halogen heater may be used. For example, as the condensing halogen heater 10a shown in FIG. 14, a halogen heater unit NIL series (condensing mirror surface gold plating) manufactured by Infridge Industry Co., Ltd. is suitable.

Further, the heating unit 10 is not limited to the case where the heating unit 10 is disposed on the downstream side of the light irradiation unit 9 in the conveyance path of the recording medium 2 as used in the embodiment of the present invention. When the heating means 10 is disposed in the transport path, the ink pixel layer must be heated within the passage time of the recording medium 2, so that it is necessary to supply a large amount of power in a short time. On the other hand, the recording medium after light irradiation can be accommodated using a heating stocker and heated in a batch manner. In this way, a plurality of recording media 2 can be heated at the same time, which is advantageous from the viewpoint of power consumption.
In addition, when the printing speed or the conveyance speed of the recording medium 2 is slow, the heating means 10 may have a heating tunnel type configuration such as an electric furnace in order to increase the heating time. When the ink component of the ink pixel layer is sufficiently cured by the light irradiation unit 9 described above, it is not necessary to provide the heating unit 10.

 The recording medium 2 on which pixels are formed through the series of pixel pattern forming steps described above is guided by the recording medium discharge guide 6 and stored in the recording medium stocker 5.

 FIG. 4 shows a block of a control device that drives and controls the inkjet image forming apparatus 1 described above. The control system includes a CPU (microprocessor) 101, a ROM (program memory) 102, a RAM (working memory) 104, a data memory 103, an operation panel 107, and the like.

 A CPU (microprocessor) 101 is an ink jet recording head drive circuit 111, a transport unit drive circuit 112, a pre-light irradiation unit control circuit 114, and a light irradiation unit control according to a preset operation program stored in the ROM 102 or the data memory 103. The circuit 115, the heating means control circuit 117, and the power supply circuit 110 are controlled. Under such control, the inkjet recording heads 11 to 14, the pre-light irradiation means 21 to 24, the light irradiation means 9, the heating means 10, the conveying means 3, and the power supply circuit 110 operate as follows.

  The operation of the inkjet image forming apparatus 1 of FIG. 1 will be described with reference to the circuit configuration of the control system of FIG. Print data and commands sent from the computer 109 via the interface 108 are transferred to a RAM (working memory) 104 and stored in an operation program stored in a ROM (program memory) 102 and command data stored in the data memory 103. Based on this, it is processed by the CPU 101. The processed print data is transferred to the inkjet recording head drive circuit 111, and a drive signal for printing is sent to each of the inkjet recording heads 11-14.

 At the same time, the drive signals of the respective parts processed by the CPU 101 are sent to the transport means drive circuit 112, the pre-light irradiation means control circuit 114, the light irradiation means control circuit 115, and the heating means control circuit 117, and these drive control circuits operate. It operates according to the program, and an image is formed on the recording medium 2.

 Driving voltage of the inkjet recording heads 11 to 14 from the power supply circuit 110, motor driving voltage for driving the conveying means 3, operating voltage of the pre-light irradiation means 21 to 24, operating voltage of the light irradiation means 9 and operation of the heating means 10 The voltage is also output at the same time.

 The operation panel 107 is provided for displaying detailed settings of the operating environment of the inkjet recording apparatus 1 or the operation status of the operation process. The operation panel 107 feeds back the operation signals from the drive control circuits of each unit to display or set. Do.

 A specific embodiment in which pixels are formed on a recording medium 2 using the inkjet image forming apparatus 1 shown in FIG. 1 will be described.

The photocurable ink used in this embodiment will be described. First, the epoxy compound A, which is the main component of the acid polymerizable compound shown in [Chemical Formula 1] A, and the oxetane compound B shown in [Chemical Formula 1] B are mixed at 1: 1 (weight ratio) as shown in Table 1, An acid polymerizable composition (epoxy composition) a was obtained. As the epoxy compound A, SR-NPG manufactured by Sakamoto Pharmaceutical Co., Ltd. was used, and as the oxetane compound B, OXT-221 manufactured by Toagosei Co., Ltd. was used.

 In the present embodiment, an epoxy compound is used as the main component of the acid-polymerizable compound. However, the ink that can be used in the present invention is not limited to this material. In addition to the epoxy compound, a vinyl ether compound and What is necessary is just to consist of at least 1 or more types of solvent selected from the group which consists of oxetane compounds.

 Carbon black pigment corresponding to 4% by weight (weight ratio with respect to the epoxy composition a) previously kneaded with the acrylic resin with respect to the acid polymerizable composition (epoxy composition) a, and 200 ppm nonionic surfactant What added the agent (made by Sumitomo 3M) was prepared. Thereafter, these mixtures were subjected to a dispersion treatment with a paint shaker for a whole day and night to obtain a black composition a (B) shown in Table 2.

These black compositions a (B) and a photoacid generator F described later were mixed at a ratio shown in Table 2 to obtain photosensitive ink [1].

As the above-mentioned photoacid generator F, the photoacid generator C shown in [Chemical Formula 2] C and the photoacid generator D shown in [Chemical Formula 2] D are dissolved in an equal amount of propylene carbonate at a ratio of 1: 1. A propylene carbonate solution containing a sulfonium salt having a concentration of 50% by weight: UVACURE 1590 (manufactured by Daicel UC Corporation) was used.

 For the purpose of increasing the photosensitivity of the photoacid generator F, the sensitizer E shown in [Chemical Formula 3] E was added to the photoacid generator F by 35% by weight.

As sensitizer E, ANTHRACURE_UVS-1331 manufactured by Kawasaki Kasei Kogyo Co., Ltd. was used.

After sufficiently stirring the above mixture, the mixture was filtered through a 5 μm PTFE filter to obtain a photocurable ink [2] shown in Table 3.

 Moreover, in the inkjet image forming apparatus 1 according to the embodiment of the present invention, the ink needs to be adjusted to a predetermined viscosity in order to stably eject the ink. For example, the viscosity at 25 ° C. is preferably 50 mPa · S or less, and more preferably 30 mPa · S or less. The ink viscosity is adjusted, for example, by selecting the type of the main agent (solvent). When a plurality of solvents are used, the viscosity of the ink is adjusted by the mixing ratio of these solvents.

 The photocurable ink according to the present invention is not limited to a photocurable ink composed of a cationic material that is polymerized and cured in the presence of an acid as described above, but an acryloyl group or a methacryloyl group. It may be a radical photocurable ink composed of an acrylic photocurable oligomer or a synthetic material of polymer.

Table 4 shows pixel patterns used in examples described below as pixel patterns for forming an image on the recording medium 2. In particular, the pixel pattern is a solid image in which a mottle or bleed phenomenon is likely to appear.

  FIG. 5 shows a pixel area 40 partitioned on the recording medium 2 with A as the pixel pitch in the main scanning direction (nozzle arrangement direction) and B as the pixel pitch in the sub-scanning direction (relative movement direction). In the embodiment of the present invention, first, a solid image composed of the pixel pattern A composed of pixels having the same area was formed in all the pixel regions 40. Further, a solid image composed of a pixel pattern B formed by combining the pixels having different areas by improving the pixel pattern A was formed. The resolution of the pixel region 40 was 300 dpi, 450 dpi, and 600 dpi, respectively, and the ink consumption and the image quality were compared and evaluated for the pixel patterns formed in the respective examples.

[Example 1A]
A solid image composed of the pixel pattern A is formed in the image area 40 with a resolution of 300 dpi on the recording medium 2, and the formed solid image is shown in FIG. The numbers in the figure indicate pixel 1 and pixel 2. In this embodiment, of the inkjet recording heads 11 to 14 mounted on the inkjet image forming apparatus 1, two of the inkjet recording head 11 and the inkjet recording head 12 are used, and of the pre-irradiation means 21 to 24. Pre-irradiation means 21 and 22 were used. The ink jet recording heads 11 and 12 are those having a nozzle arrangement pitch of 300 dpi. Details of the process of forming a solid image composed of the pixel pattern A will be described below with reference to FIGS.

 The recording medium 2 supplied by the recording medium supply unit 4 is conveyed from the right side to the left side in FIG. 1 by the conveyance unit 3, and the inkjet recording heads 11 to 14 and the recording medium 2 are relatively moved. The conveyance speed of the recording medium 2 was 25 m / min. When the leading end of the recording medium 2 is detected by the position detection means 32, the ink amount necessary to form a preset pixel area in the pixel area 40 on the recording medium 2 corresponding to the pixel 1 at a predetermined timing is obtained. An ink pixel layer is deposited every other nozzle by discharging from the nozzle 18 of the inkjet recording head 11. In the relative movement direction (sub-scanning direction), an ink pixel layer is attached every other pixel. The amount of ink discharged to form one pixel was adjusted by a preliminary experiment so that the area of the pixel region 40 could be almost filled.

 The ink discharge amount per nozzle of the ink jet recording head corresponding to each discharge pattern is shown in Table 14 to be described later. The ink jet recording heads 11 to 14 used in the present embodiment can control the amount of ink discharged from each nozzle in 15 stages, and can be appropriately selected according to the discharge pattern (af). The method for setting the ink discharge amount per nozzle of the ink jet recording head and the details of the ink discharge amount corresponding to each discharge pattern will be described later. In this example, the ink discharge amount corresponding to the pixel 1 was selected and set appropriately according to the discharge patterns (af) in Table 11 and the number of drops in 15 steps. The setting conditions are shown in the pixel 1 column of Example 1A in Table 5.

  After the ink is attached to the pixel region 40 corresponding to the pixel 1, the pre-light irradiation means 21 irradiates the light to such an extent that the viscosity of the ink is increased to eliminate the fluidity, and the change in the shape of the ink pixel layer is stopped. The ink pixel layer is fixed on the recording medium 2 to form an ink pixel layer corresponding to the pixel 1.

  Thereafter, the ink recording layer 12 is deposited on the recording medium 2 by ejecting the same amount of ink as the pixel 1 (the amount of ink for achieving the same pixel area) to the pixel region 40 corresponding to the pixel 2 by the inkjet recording head 12. The setting conditions are shown in the column of pixel 2 of Example 1A in Table 5. Further, light irradiation is performed by the pre-light irradiation unit 22 in the same manner as when the pixel 1 is formed, and the shape change of the ink pixel layer is stopped. In this case, the peripheral portions of the ink pixel layers corresponding to the pixel 1 and the pixel 2 overlap each other, and the pixel pattern formed by the pixel 1 and the pixel 2 as shown in FIG. Form.

 Thereafter, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1 and the pixel 2 is irradiated with light by the light irradiation means 9 to generate acid from the photoacid generator contained in the photocurable ink, The ink pixel layer is cured by cross-linking polymerization of a solvent that is polymerized in the presence of an acid, so that a solid image including a pixel pattern A having a resolution of 300 dpi and including pixels 1 and 2 is formed in the pixel region 40.

 Subsequently, the pixel formed on the recording medium 2 is heated by the heating unit 10 to further diffuse the photoacid generator in the pixel, thereby completely curing the uncured ink component in the pixel.

[Example 1B]
A solid image composed of the pixel pattern B is formed in the image region 40 having a resolution of 300 dpi by the same method as in Example 1A, and the formed solid image is shown in FIG. The numbers in the figure indicate pixel 1 and pixel 2. Hereinafter, a process for forming a solid image including the pixel pattern B will be described. Only the differences from the case of Example 1A will be described.

  The areas of the ink pixel layers of the pixel 1 and the pixel 2 of Example 1A described above are almost the same and are almost enough to make up the pixel region 40. However, Example 1B is different from the pixel 1 to be formed first. The area of the corresponding ink pixel layer was set to be larger than the area of the ink pixel layer corresponding to the pixel 2.

 The equivalent circular diameter X in the area of the ink pixel layer corresponding to the pixel 1 is set to A as the nozzle 18 arrangement pitch in the nozzle arrangement direction (main scanning direction) in the pixel region 40, and the recording medium 2 and the inkjet recording heads 11 and 12. When the pixel pitch in the relative movement direction (sub-scanning direction) is B, the relationship is set so as to satisfy Expression (1).

X ≧ (A ² + B ² ) ^1/2 ... Formula (1)
By preliminary experiments, the ink discharge amount per nozzle of the ink jet recording head is selected from the discharge patterns (af) and the number of drops in Table 14, and ink is discharged from the ink jet recording head 11 at the first timing. The pixel area was set to be formed.

The ink discharge amount corresponding to the pixel 1 performed in the present embodiment is described in the column of the pixel 1 of the embodiments 1B _{1 to} 1B ₄ in Table 5 described above.

  The pixel area corresponds to the pixel area after the change in shape of the ink pixel layer is stopped. Thus, by forming the ink pixel layer satisfying at least the formula (1), the ink pixels can be connected to each other without being separated from each other, and the gap can be eliminated when a solid image is formed.

Next, the area of the ink pixel layer corresponding to the pixel 2 was made large enough to fill the gap of the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1. The specific ink discharge amount corresponding to each embodiment is selected from the discharge patterns (af) and the number of drops shown in Table 14 by preliminary experiments, and the ink discharge amount corresponding to each embodiment is set as above. It shows in the column of the pixel 2 of Examples 1B _{1 to} 1B ₄ in Table 5. However, in this case, the pixel areas of the pixel 1 and the pixel 2 are not necessarily proportional to the ink discharge amount because the wettability between the recording medium 2 and the ink and the wettability between the inks are different.

 Similar to the method described in Example 1A, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1 and the ink pixel layer formed in the pixel region 40 corresponding to the pixel 2 are respectively subjected to pre-light irradiation. The shape change is stopped, and it is cured by subsequent light irradiation. Furthermore, a solid image composed of the pixel pattern B having a resolution of 300 dpi is formed on the recording medium 2 by completely curing the uncured portion by heating.

[Comparative Example 1]
In Example 1A and Example 1B described above, the pixel 1 and the pixel 2 were formed at different timings. However, in Comparative Example 1, a solid pixel pattern was formed by simultaneously ejecting from all the nozzles of the inkjet recording head 11. The ink discharge amount was adjusted so that the area of each pixel was the same as in Example 1A, and a solid image consisting of the pixel pattern A was formed. The ink discharge amount was the same as in Example 1A as shown in Table 5 above.

 For Example 1A, Example 1B, and Comparative Example 1 described above, the ink discharge amount and ink consumption amount per unit and the ink reduction rate relative to Example 1A are summarized in Table 6 described above.

 As shown in Table 6, it can be seen that the ink consumption for forming a solid image is smaller in Example 1B when Example 1A and Example 1B are compared. A cross-sectional view of the solid image of Example 1A is shown in FIG. 12, and a cross-sectional view of the solid image of Example 1B is shown in FIG. In Example 1B, since the pixel 1 can be formed large and the gap can be efficiently filled with the pixel 2, the thickness of the ink layer as a whole can be reduced.

 Note that “per unit” means two pixels including pixel 1 and pixel 2 for a solid image with a resolution of 300 dpi, and three pixels including pixel 1, pixel 2 and pixel 3 for a solid image with a resolution of 450 dpi. A solid image having a resolution of 600 dpi represents a total of four pixels including pixel 1, pixel 2, pixel 3, and pixel 4.

  In Example 1A, Example 1B, and Comparative Example 1, the image quality of the formed solid images was evaluated, and the results are shown in Table 7.

  The image quality was evaluated from the five viewpoints of mottle, solid image glossiness, solid image density, solid image uniformity, and graininess. As the judgment of the image quality, (1) For the motor, ○: good, Δ: a little, x: yes. (2) The solid image glossiness was determined as follows: ○: glossy, Δ: matte tone, x: bad. (3) Regarding the solid image density, ◯: good, Δ: normal, x: low. (4) Regarding the uniformity of the solid image, ○: good, Δ: somewhat bad, x: bad. (5) Regarding the graininess, ◯: None, Δ: Slight graininess, x: Yes.

 From the above, after forming the ink pixel layer 1 corresponding to the pixel 1 on the recording medium 2, the ink pixel layer 2 corresponding to the pixel 2 smaller than the ink pixel layer 1 so as to fill the gap of the ink pixel layer 1. By forming this, it is possible to form an overlapping portion between pixels, reduce the ink consumption, and reduce the amount of light irradiation because the ink pixel layer can be formed thin overall. it can. Further, in Comparative Example 1, since ink is simultaneously deposited on the recording medium from the nozzles adjacent in the longitudinal direction of the ink jet recording head, the inks of the adjacent ink pixel layers are mixed, but they are adjacent as shown in the example. By forming the ink pixel layers at different timings, the occurrence of the mottle phenomenon can be prevented, and the image quality can be improved as shown in Table 7.

[Example 2A]
Next, a solid image composed of the pixel pattern A is formed in the image area 40 with a resolution of 450 dpi on the recording medium 2 by the same method as in Example 1A, and the formed solid image is shown in FIG. The numbers in the figure indicate pixel 1, pixel 2, and pixel 3. For the inkjet recording heads 11 to 14, three line-type inkjet recording heads 11 to 13 having an arrangement pitch of nozzles of 450 dpi were used.

 Hereinafter, only the differences of Example 2A from Example 1A will be described. A process of forming a solid image composed of the pixel pattern A on the recording medium 2 will be described with reference to FIGS.

 An ink amount that forms a pixel area set in advance in the pixel area 40 corresponding to the pixel 1 is ejected from the nozzle 18 of the inkjet recording head 11 in the nozzle arrangement direction (main scanning direction) every two nozzles to form an ink pixel layer. Adhere. In the relative movement direction (sub-scanning direction), an ink pixel layer is attached every two pixels.

 Thereafter, in the pixel area 40 corresponding to the pixel 2, the same amount of ink as that of the pixel 1 (the amount of ink for obtaining the same pixel area) is placed in two nozzles from the nozzle 18 of the inkjet recording head 12 in the nozzle arrangement direction (main scanning direction). The ink pixel layer is deposited every two nozzles as in the pixel 1. In the relative movement direction (sub-scanning direction), the ink pixel layer is attached every two pixels as in the pixel 1.

 Further, in the pixel area 40 on the recording medium 2 corresponding to the pixel 3, the same ink amount as that of the pixel 1 and the pixel 2 (ink amount for achieving the same pixel area) is applied to the ink jet recording head in the nozzle arrangement direction (main scanning direction). 13 nozzles 18 are ejected every 2 nozzles, and the ink pixel layer is attached every 2 nozzles, like the pixels 1 and 2. In the relative movement direction (sub-scanning direction), the ink pixel layer is attached every two pixels as in the case of the pixels 1 and 2.

 Table 11 shows that the ink discharge amount for forming the ink pixel layer corresponding to the pixel 1, the pixel 2 and the pixel 3 described above is based on preliminary experiments so that the area of the ink region is substantially filled with the pixel region 40 as in Example 1A. Were selected from the ejection patterns (af) and the number of drops, and the ink ejection amount was appropriately set. The amount of ink ejected is shown in Example 2A in Table 8.

 Similar to the method described in Example 1A, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 2, and the pixel region corresponding to the pixel 3 Each of the ink pixel layers formed in 40 has its shape changed by sequential pre-light irradiation and then cured by subsequent light irradiation. Furthermore, a solid image composed of the pixel pattern A having a resolution of 450 dpi is formed on the recording medium 2 by completely curing the uncured portion by heating.

[Example 2B]
A solid image composed of the pixel pattern B is formed in the image area 40 with a resolution of 450 dpi on the recording medium 2 by the same method as in Example 2A, and the formed B pattern image is shown in FIG. The numbers in the figure indicate pixel 1, pixel 2, and pixel 3.

  A process for forming a solid image in which ink is ejected at three different timings will be described with reference to FIGS. For the inkjet recording heads 11 to 14, three line-type inkjet recording heads 11 to 13 having an arrangement pitch of nozzles of 450 dpi were used.

 Hereinafter, only a part different from Example 2A in Example 2B will be described. The areas of the ink pixel layers of the pixel 1, pixel 2 and pixel 3 of Example 2A described above are almost the same and are almost enough to fill the pixel region 40. However, Example 2B is similar to Example 1B. Similarly, the area of the ink pixel layer corresponding to the pixel 1 to be formed first is larger than the area of the ink pixel layer corresponding to the pixel 2, and further, the area of the ink pixel layer corresponding to the pixel 2 corresponds to the pixel 3. It was set to be larger than the area of the ink pixel layer.

 The equivalent circular diameter X in the area of the ink pixel layer corresponding to the pixel 1 is A, where the arrangement pitch of the nozzles 18 in the nozzle arrangement direction (main scanning direction) in the pixel region 40 is A, and the recording medium 2 and the inkjet recording heads 11, 12 and When the pixel pitch in the relative movement direction (sub-scanning direction) with respect to 13 is B, the relationship is set so as to satisfy the above equation (1). According to a preliminary experiment, an ink discharge amount was selected from the discharge patterns (af) and the number of drops in Table 14, and the pixel area of the pixel 1 discharged from the inkjet recording head 11 was set to be formed at the first timing. .

The ink ejection amount corresponding to the pixel 1 of the present embodiment is described in the column of the pixel 1 of the embodiments 2B _{1 to} 2B ₄ in Table 8 described above.

 The pixel area corresponds to the pixel area after the change in shape of the ink pixel layer is stopped. By forming the ink pixel layer satisfying at least the above-described formula (1) as described above, the ink pixels can be connected to each other without being separated from each other, and the gap can be eliminated when a solid image is formed. .

Next, for the pixel area of the ink pixel layer corresponding to the pixel 2 and the pixel 3, the ink discharge amount was set so as to form the solid image shown in FIG. The ink discharge amount corresponding to each specific example is selected based on the discharge pattern (af) in Table 14 and the number of drops by preliminary experiments, and the ink discharge amount corresponding to each example is determined. It shows in the column of the pixel 2 and the pixel 3 of Examples 2B _{1 to} 2B ₄ in Table 6 described above. However, in this case, as in Example 1B, the pixel areas of the pixels 1 to 3 are not necessarily proportional to the ink discharge amount because the wettability of the recording medium 2 and the ink and the wettability of the inks are different.

 Similar to the method described in Example 2A, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 2, and the pixel region corresponding to the pixel 3 Each of the ink pixel layers formed in 40 has its shape changed by pre-light irradiation and cured by subsequent light irradiation. Furthermore, a solid image composed of the pixel pattern B having a resolution of 450 dpi is formed on the recording medium 2 by completely curing the uncured portion by heating.

[Comparative Example 2]
In the above-described Example 2A and Example 2B, the pixel 1, the pixel 2 and the pixel 3 are formed at different timings. However, in this comparative example 2, a solid pixel pattern is formed by simultaneously ejecting from all the nozzles of the inkjet recording head 11. Formed. The ink discharge amount was adjusted so that the area of each pixel was the same as in Example 2A, and a solid image consisting of the pixel pattern A was formed. The ink discharge amount was the same as in Example 2A as shown in Table 8 above.

For Example 2A, Example 2B, and Comparative Example 2 described above, the ink discharge amount and ink consumption amount per unit and the ink reduction rate relative to Example 2A are summarized in Table 9 described above.

 As shown in Table 9, it can be seen that the ink consumption for forming the solid image is smaller in Example 2B than in Example 2A. In addition, regarding the solid images of Example 2A and Example 2B, Example 2B can form the pixel 1 large and efficiently fill the gap between the pixel 2 and the pixel 3. The thickness can be reduced.

  Further, for Example 2A, Example 2B, and Comparative Example 2, the image quality of the formed solid images was evaluated, and the results are shown in Table 10.

  The items of image quality evaluation were the same as in Example 1.

 From the above, as in the case of the first embodiment, the ink consumption of the second embodiment can be reduced more than that of the second embodiment, and the light irradiation amount can be reduced because the ink pixel layer can be made thinner. can do. Further, in Comparative Example 2, since the ink is simultaneously deposited on the recording medium from the nozzles in the longitudinal direction of the inkjet recording head, the inks of the adjacent ink pixel layers are mixed, but as shown in the examples. By forming the adjacent ink pixel layers at different timings, the occurrence of the mottle phenomenon can be prevented, and the image quality can be improved as shown in Table 10.

[Example 3A]
Next, a solid image composed of the pixel pattern A is formed in the image area 40 with a resolution of 600 dpi on the recording medium 2 by the same method as in Example 1A, and the formed solid image is shown in FIG. The numbers in the figure indicate pixel 1, pixel 2, pixel 3, and pixel 4. For the inkjet recording heads 11 to 14, four line-type inkjet recording heads 11 to 14 having an arrangement pitch of nozzles of 600 dpi were used.

 Hereinafter, only the part of Example 3A different from Example 1A and Example 2A will be described.

A process of forming a solid image composed of the pixel pattern A on the recording medium 2 will be described with reference to FIGS.

  An ink amount that forms a preset pixel area in the pixel region 40 corresponding to the pixel 1 is ejected from the nozzles 18 of the inkjet recording head 11 every three nozzles in the nozzle arrangement direction (main scanning direction) to form an ink pixel layer. Adhere. In the relative movement direction (sub-scanning direction), an ink pixel layer is attached every three pixels.

 Thereafter, in the pixel region 40 corresponding to the pixel 2, the same ink amount as that of the pixel 1 (ink amount for achieving the same pixel area) is arranged by three nozzles from the nozzles 18 of the inkjet recording head 12 in the nozzle arrangement direction (main scanning direction). Then, an ink pixel layer is attached every three nozzles as in the case of the pixel 1. In the relative movement direction (sub-scanning direction), the ink pixel layer is attached every three pixels as in the pixel 1.

  Further, the same ink amount as that of the pixel 1 and the pixel 2 (ink amount for achieving the same pixel area) is discharged from the nozzle 18 of the inkjet recording head 13 every three nozzles in the nozzle array direction to the pixel region 40 corresponding to the pixel 3. Thus, the ink pixel layer is attached every three nozzles as in the case of the pixel 1 and the pixel 2. In the relative movement direction (sub-scanning direction), the ink pixel layer is attached every three pixels as in the pixel 1 and the pixel 2.

  Further, in the pixel area 40 on the recording medium 2 corresponding to the pixel 4, the same ink amount as that of the pixel 1, the pixel 2, and the pixel 3 (the ink amount for obtaining the same pixel area) is arranged in the nozzle arrangement direction with 14 nozzles of the inkjet recording head Eighteen nozzles are ejected every three nozzles, and an ink pixel layer is deposited every three nozzles as in the case of pixel 1, pixel 2, and pixel 3. In the relative movement direction (sub-scanning direction), the ink pixel layer is attached every three pixels as in the case of the pixel 1, the pixel 2, and the pixel 3.

  The ink discharge amount for forming the ink pixel layer corresponding to the pixel 1, the pixel 2, the pixel 3, and the pixel 4 described above is an area that substantially fills the pixel region 40 as in the first and second embodiments. In the preliminary experiment, the ink ejection amount was appropriately set by selecting the ejection pattern (af) in Table 14 and the number of drops. The amount of ink ejected is shown in Example 3A in Table 11.

  Similar to the method described in Example 1A, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 2, and the pixel region corresponding to the pixel 3 The ink pixel layer formed in 40 and the ink pixel layer formed in the pixel region 40 corresponding to the pixel 4 are sequentially stopped by the pre-light irradiation, and cured by the subsequent light irradiation. Furthermore, a solid image composed of the pixel pattern A having a resolution of 600 dpi is formed on the recording medium 2 by completely curing the uncured portion by heating.

[Example 3B]
A solid image composed of the pixel pattern B is formed in the image area 40 with a resolution of 600 dpi on the recording medium 2 by the same method as in Example 3A, and the formed solid image is shown in FIG. The numbers in the figure indicate pixel 1, pixel 2, pixel 3, and pixel 4.

  A pixel formation process in which ink is ejected at four different timings will be described with reference to FIGS. For the inkjet recording heads 11 to 14, four line-type inkjet recording heads 11 to 14 having an arrangement pitch of nozzles of 600 dpi were used.

 Hereinafter, only the parts of Example 3B different from Example 3A will be described. The areas of the ink pixel layers of the pixel 1, the pixel 2, the pixel 3, and the pixel 4 in Example 3A described above are all the same and are approximately enough to fill the pixel region 40. However, in Example 3B, Similarly to Example 1B and Example 2B, the area of the ink pixel layer corresponding to the pixel 1 that is formed first is larger than the area of the ink pixel layer corresponding to the pixel 2, and further, the ink pixel layer corresponding to the pixel 2 Is larger than the area of the ink pixel layer corresponding to the pixel 3, and further, the area of the ink pixel layer corresponding to the pixel 3 is set to be larger than the area of the ink pixel layer corresponding to the pixel 4.

 The equivalent circular diameter X in the area of the ink pixel layer corresponding to the pixel 1 is A, where the arrangement pitch of the nozzles 18 in the nozzle arrangement direction (main scanning direction) in the pixel region 40 is A, and the recording medium 2 and the inkjet recording heads 11, 12, When the pixel pitch in the relative movement direction (sub-scanning direction) with respect to 13 and 14 is B, the relationship is set so as to satisfy the above equation (1). By preliminary experiments, the ink ejection amount was selected from the ejection patterns (af) and the number of drops in Table 11, and the pixel area of the pixel 1 ejected from the inkjet recording head 11 was set to be formed at the first timing. .

The ink discharge amount corresponding to the pixel 1 of the present embodiment is shown in the column of the pixel 1 of the embodiments 3B _{1 to} 3B ₄ in Table 11 described above.

 The pixel area corresponds to the pixel area after the change in shape of the ink pixel layer is stopped. By forming the ink pixel layer satisfying at least the above-described formula (1) in this way, the ink pixels can be connected to each other without being separated from each other, and the gap is eliminated when a solid image is formed. it can.

Next, for the pixel area of the ink pixel layer corresponding to the pixel 2, the pixel 3, and the pixel 4, the ink discharge amount was set so as to form the solid image shown in FIG. The ink discharge amount corresponding to each specific example is selected based on the discharge patterns (af) in Table 11 and the number of drops according to preliminary experiments, and the ink discharge amount corresponding to each example is set as above. These are shown in the columns of pixel 2, pixel 3 and pixel 4 of Examples 3B _{1 to} 3B ₄ in Table 7. However, in this case, the pixel areas of the pixels 1 to 4 are not necessarily proportional to the ink discharge amount because the wettability of the recording medium 2 and the ink and the wettability of the inks are different as in Example 1B.

 Similar to the method described in Example 3A, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 1, the ink pixel layer formed in the pixel region 40 corresponding to the pixel 2, and the pixel region corresponding to the pixel 3 The shape change of the ink pixel layer formed in 40 and the pixel region 40 formed in the pixel region 40 corresponding to the pixel 4 are stopped by pre-light irradiation, and cured by the subsequent light irradiation. Furthermore, a solid image composed of the pixel pattern B having a resolution of 600 dpi is formed on the recording medium 2 by completely curing the uncured portion by heating.

[Comparative Example 3]
In the above-described Example 3A and Example 3B, the pixels 1 to 4 in the main scanning direction are formed at different timings. However, in this comparative example 3, the solid pixel pattern is ejected simultaneously from all the nozzles of the inkjet recording head 11. Formed. The ink discharge amount was adjusted so that the area of each pixel was the same as in Example 3A, and a solid image consisting of the pixel pattern A was formed. The ink discharge amount was the same as that in Example 3A as shown in Table 7 above.

 For Example 3A, Example 3B, and Comparative Example 3 described above, the ink discharge amount and ink consumption per unit and the ink reduction rate of Example 3B relative to Example 3A are summarized in Table 12 above.

 As shown in Table 12, it can be seen that the ink consumption for forming a solid image is smaller in Example 3B than in Example 3A. In addition, regarding the solid images of Example 3A and Example 3B, Example 3B is formed so that the pixel 1 is formed large and the gap between the pixels 2 to 4 is efficiently filled. The thickness can be reduced.

  Further, for Example 3A, Example 3B and Comparative Example 3, the image quality of the formed solid images was evaluated, and the results are shown in Table 13.

The items of image quality evaluation were the same as in Example 1.

 From the above, as in the case of the first embodiment, the ink consumption of the third embodiment can be reduced more than that of the third embodiment, and the light irradiation amount can be reduced because the ink pixel layer can be made thinner. can do. Further, in Comparative Example 3, since the ink is simultaneously deposited on the recording medium from the nozzles in the longitudinal direction of the ink jet recording head, the inks of the adjacent ink pixel layers are mixed, as shown in the examples. By forming the adjacent ink pixel layers at different timings, the occurrence of the mottle phenomenon can be prevented, and the image quality can be improved as shown in Table 13.

  In addition, although the case where all the solid images which are likely to cause mottle and bleed are formed has been described above, even in a character region or a pixel diagram where there is no gap where at least two or more pixels are continuous. Needless to say, there is a similar effect.

 Here, a method for setting the ink discharge amount in each of the above-described embodiments will be described below. First, a calculation method (ink amount setting method) of the ink discharge amount (ink discharge volume) discharged from one nozzle of the ink jet recording head necessary for forming a unit dot image (pixel) will be described. The ink jet recording heads 11 to 14 discharge ink droplets by so-called multi-drop driving that divides the maximum ink discharge amount to be discharged from one nozzle for forming one pixel into 15 by the control of the ink jet recording head driving circuit 111, It is possible to change the ink discharge amount by selecting the number of ink droplet drops.

 Since it has been experimentally confirmed that the ink discharge amount in the multi-drop driving is proportional to the number of drops, if the ink discharge amount at the time of 15 drops is set, the ink discharge amount corresponding to each drop number is 15 drops It can be obtained by calculation based on the number of ink ejection amounts.

 Table 14 shows an example of the relationship between the number of drops and the ink discharge amount for the discharge patterns (af) corresponding to the maximum ink discharge amount (15 drop number). The ink discharge amount at the time of 15 drops is changed by, for example, the drive voltage applied to the ink jet recording head.

  As described above, the relationship between the ink jet recording head drive voltage condition and the ink discharge amount is previously grasped and stored in the data memory 103 or the like. The ink discharge amount that forms a desired pixel size can be read from the data memory 103 to control the ink discharge amount.

  Here, an example of a method for calculating the ink discharge amount per nozzle at the time of 15 drops will be described.

The amount of ink ejected once per nozzle at the time of 15 drops is calculated from the amount of ejected droplets per inkjet recording head, the number of ejections per nozzle, the number of nozzles per inkjet recording head, and the ink density. To do.
Discharge amount per nozzle (pl) = discharged droplet amount per ink jet recording head (g) / (ink density × number of discharges per nozzle × number of nozzles per ink jet recording head)

As a specific example, for example, the number of ejections per nozzle is 10,000, the number of nozzles per inkjet recording head is 500, the amount of ejected droplets per inkjet recording head: 0.225 g, and the ink density is 1 In the case of 0.0 g / cm ³ , the ink ejection amount (ejection volume) of ink droplets ejected once per nozzle can be calculated and expressed by the following calculation formula.

Ink ejection amount ejected once per nozzle at 15 drops = 1 ejection droplet amount per ink jet recording head / (ink density × number of ejection times × number of nozzles) = 0.225 / (1.0 × 10000 × 500 ) = 4.5 × 10 ⁻⁸ cm ³ = 4.5 × 10 ⁻⁸ cm ³ × 10 ⁹ = 45 pl.

  As described above, the relationship between the ink jet recording head drive voltage condition and the discharge amount is grasped in advance, the ink discharge amount per nozzle at the time of 15 drops of each of the a to f patterns is set, and discharge pattern correspondence table data is obtained.

  Regarding the present invention, Examples 1 to 3 have been disclosed in the case of an inkjet image forming apparatus using a so-called line-type head in which a plurality of nozzles are arranged in the longitudinal direction of the inkjet recording head as the inkjet recording head. The present invention can be similarly applied to a so-called serial type image forming apparatus that forms an image on a recording medium by moving the recording medium relative to the recording medium.

  In the case of using the line type ink jet recording heads 11 to 14 in the above-described embodiment, the moving means for relatively moving the ink jet recording head and the recording medium is configured only by the recording medium conveying means 3. However, the serial type ink jet image forming apparatus includes both a moving means for the ink jet recording head and a conveying means for the recording medium.

  Further, the present invention can be similarly applied to a flat bed type inkjet image forming apparatus. Hereinafter, an example of the flat bed type inkjet image forming apparatus 50 will be described with reference to FIG. In the flat-bed type inkjet image forming apparatus 50, an inkjet recording head unit 51 supported by first guide rails 61 and 62 and controlled to move in the A direction, the B direction, and further in the C direction is separately fixed. It is mounted on the upper surface of the medium 70.

  In the flat bed type inkjet image forming apparatus 50 described above, the moving means for relatively moving the recording medium 70 and the inkjet image forming apparatus 51 is constituted by a linear motor (not shown) or the like. The first guide rails 61 and 62 are moved in the A direction and the B direction, and the second guide rails 63 and 64 are relatively moved in the C direction.

  In the inkjet recording head unit 51, inkjet recording heads 52 to 55 are arranged in the moving direction (arrow B direction), and pre-light irradiation means 56 to 59 are arranged behind the moving directions of the respective inkjet recording heads 52 to 55, Furthermore, the light irradiation means 65 and the heating means 66 are arranged in order. The ink jet recording head unit 51 supported by the first guide rail is supported by the second guide rails 63 and 64 and is controlled to move in the C direction.

  In such a configuration, the inkjet recording head unit 51 is controlled to move the upper surface of the recording medium 70 in the A direction, the B direction, and the C direction, and forms an image on the recording medium 70. First, photocurable ink is ejected from the ink jet recording heads 52 to 55 mounted on the ink jet recording head unit 51 moving in the A direction, and an ink pixel layer is attached onto the recording medium 70. Next, the shape of the ink pixel layer on the recording medium 70 is sequentially stopped by the pre-light irradiation means 56 to 59, and is further cured and fixed by the light irradiation means 65 and the heating means 66. Are sequentially formed. After the ink jet recording head unit 51 arrives at the end of the pixel area on the recording medium 70 by this series of operations, the ink jet recording head unit 51 moves in the B direction and the C direction while moving to the next image on the recording medium 70. Prepare for formation. Further, this operation is repeated to sequentially form images on the recording medium 70.

  In such a flatbed type inkjet image forming apparatus 50, as in the above-described embodiment of the present invention, a good image that does not cause mottle or bleed is formed, and further, the ink consumption can be reduced and cured. The amount of light irradiation can be reduced.

  Further, the photo-curable ink is disclosed only for the case of a single color, but it can be similarly applied to the case of color printing, and the occurrence of bleeding similar to the mottle phenomenon can be reduced. In this case, the inkjet recording head mounted on the inkjet image forming apparatus 1 is mounted for each color.

  The ink jet image forming apparatus and the ink jet image forming method according to the present invention can be widely used as an industrial recording apparatus.

1 is a schematic diagram of an inkjet image forming apparatus according to an embodiment of the present invention. 1 is a perspective view of an ink jet recording head mounted on an ink jet image forming apparatus of the present invention. It is sectional drawing of the nozzle vicinity of the inkjet recording head main body used for implementation of this invention. 1 is a block diagram for controlling an inkjet image forming apparatus according to the present invention. FIG. It is a figure which shows the pixel area | region on a recording medium. It is the image pattern used for Example 1A of this invention. It is the image pattern used for Example 1B of this invention. It is the image pattern used for Example 2A of this invention. It is the image pattern used for Example 2B of this invention. It is an image pattern used for Example 3A of the present invention. It is the image pattern used for Example 3B of this invention. It is a figure which shows the cross section of the solid image of Example 1A of this invention. It is a figure which shows the cross section of the solid image of Example 1B of this invention. It is a schematic diagram of the modification of the inkjet image forming apparatus which concerns on one Embodiment of this invention. It is a schematic diagram of the other inkjet image forming apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet image forming apparatus 2 Recording medium 3 Conveying means 4 Recording medium supply means 5 Recording medium stocker 6 Recording medium discharge guide 7 Driven roller 8 Drive roller 9 Light irradiation means 10 Heating means 11-14 Inkjet recording head 15 Ink chamber 18 Nozzle 21 24 Pre-light irradiation means 30 Conveying belt 31 Platen roller 32 Position detection means 34 Actuator 40 Pixel area 101 CPU (microprocessor)
102 ROM (program memory),
103 Data memory 104 RAM (Working memory)
105 CPU Bus 106 Input Port 107 Operation Panel 108 Interface 109 Computer 110 Power Supply Circuit 111 Inkjet Recording Head Drive Circuit 112 Recording Medium Conveying Means Drive Circuit 114 Pre-Light Irradiation Means Control Circuit 115 Light Irradiation Means Control Circuit 117 Heating Means Control Circuit

Claims (8)

An ink jet recording head that ejects photocurable ink from a nozzle to form an ink pixel layer in a pixel region on the recording medium; ink ejection control means that controls ejection of the ink; and the recording medium and / or the ink jet recording. In an inkjet image forming apparatus comprising: a moving unit that relatively moves the head; and a light irradiation unit that forms a pixel by irradiating light to cure the ink of the ink pixel layer.
An ink jet image forming apparatus according to claim 1, wherein the ink discharge control means forms ink pixel layers by attaching ink to two adjacent pixel regions in the longitudinal direction of the ink jet recording head at different timings.   2. The inkjet image forming apparatus according to claim 1, wherein a nozzle arrangement pitch in a longitudinal direction of the inkjet recording head is equal to a pixel pitch. An ink jet recording head that forms an ink pixel layer in a pixel region on a recording medium by discharging photocurable ink from a nozzle at a plurality of different timings; an ink discharge control unit that controls the ink discharge; and the recording In an inkjet image forming apparatus comprising: a moving unit that relatively moves a medium and / or the inkjet recording head; and a light irradiation unit that forms a pixel by irradiating light to cure ink in the ink pixel layer.
The ink ejection control means forms an ink pixel layer by attaching ink to two adjacent pixel regions at different timings, and after the shape change of one ink pixel layer stops, forms the other ink pixel layer And controlling the area of the one ink pixel layer to be larger than the area of the other ink pixel layer. The nozzles are arranged at a predetermined pitch, the nozzle arrangement pitch is A, the pixel pitch in the relative movement direction is B, and the equivalent circle diameter of the ink pixel layer formed by ejecting ink at the first timing is X (1) Formula X ≧ (A ² + B ² ) ^1/2 ... (1) (However, the equivalent circle diameter is the same as the area of the ink pixel layer. Diameter of a circle with an area of
The inkjet image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to form an image satisfying the above condition.   5. The inkjet image according to claim 1, further comprising pre-light irradiation means for performing light irradiation for stopping a change in shape of the ink pixel layer formed on the recording medium. Forming equipment. Forming an ink pixel layer in a pixel region on a recording medium by ejecting photocurable ink from a nozzle of an inkjet recording head, and curing the ink by irradiating the ink pixel layer with light to form a pixel. And an inkjet image forming method comprising:
An ink jet image forming method, wherein an ink pixel layer is formed by attaching ink to two adjacent pixel regions in the longitudinal direction of the ink jet recording head at different timings.   The inkjet image forming method according to claim 6, wherein a nozzle arrangement pitch in a longitudinal direction of the inkjet recording head is equal to a pixel pitch. A step of ejecting photocurable ink from nozzles of an ink jet recording head at a plurality of different timings to form an ink pixel layer in a pixel region on a recording medium; and irradiating the ink pixel layer with light, and the ink pixel layer A light irradiation step of curing pixels of the ink to form pixels, and an inkjet image forming method comprising:
An ink pixel layer is formed by attaching ink to two adjacent pixel regions in the longitudinal direction of the ink jet recording head at different timings, and after the shape change of one ink pixel layer is stopped, the other ink pixel layer is An inkjet image forming method comprising: forming an ink pixel layer so that an area of the one ink pixel layer is larger than an area of the other ink pixel layer.

Images