JP2010076872A - Image forming device and method of detecting floating of recording medium - Google Patents

Abstract

An image forming apparatus capable of detecting a floating of a recording medium held by a transport mechanism with high accuracy and a recording medium floating detection method applied thereto.
A conveying means (126c) for conveying a recording medium (114), a recording head for forming an image on a recording medium (114) conveyed by the conveying means (126c), and a conveying means (more than the recording head) 126c) a light projecting means (512) for irradiating the inspection light passing through the entire width range of the recording medium (114) in the width direction of the recording medium (114) on the upstream side in the conveyance direction of the recording medium (114); A light receiving means (514) that receives the detection light emitted from the light projecting means (512) and outputs a signal corresponding to the amount of received light is provided on the opposite side of the light projecting means (512) across the medium (114). At least one of the light projecting means (512) and the light receiving means (514) is provided with a long slit in the transport direction that restricts the detection light passing range.
[Selection] Figure 6

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, a floating of a recording medium suitable for preventing contact between a recording head and a recording medium in an apparatus that performs drawing on the recording medium by relative movement of the recording head and the recording medium. Related to detection technology.

  An inkjet recording apparatus widely used as an image forming apparatus moves from each nozzle to a recording medium according to input image data while moving the recording medium relative to an inkjet head (recording head) having a plurality of nozzles. An image is recorded on a recording medium by ejecting ink droplets toward each other.

  In Patent Document 1, in order to prevent the recording paper and the nozzle from coming into contact with each other due to the floating of the recording paper wound around the platen drum, the recording paper is lifted by providing a light projecting element and a light receiving element in the circumferential direction of the drum. The structure which detects this is disclosed.

Japanese Patent Application Laid-Open No. 2004-228561 discloses the use of an optical sensor arranged in the width direction of the paper in order to detect the lifting of the paper adsorbed on the platen belt.
JP-A-63-438247 (especially FIG. 6) JP 2006-341474 A (particularly FIG. 7)

  However, the method described in Patent Document 1 can detect only one float (portion provided with the light projecting element) in the axial direction of the drum. Although it is conceivable to arrange light emitting / receiving sensor pairs at a plurality of locations in the drum axial direction, the number of sensors increases, the arrangement structure becomes complicated, and an intermediate location between the sensors cannot be detected. Therefore, in any case, the entire range of the paper width cannot be detected.

  In this respect, Patent Document 2 detects the floating of the paper from the platen belt by arranging the light emitting element and the light receiving element in the paper width direction to face each other. However, the minute paper floating is detected with high accuracy and stability. There is no disclosure about specific devices for detection.

  The present invention has been made in view of such circumstances, and an image forming apparatus capable of detecting with high accuracy the floating of a recording medium held by a transport mechanism (so-called sheet floating) and a recording medium applied thereto. It is an object of the present invention to provide a method for detecting the rising of an object.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a conveying unit that conveys a recording medium, a recording head that forms an image on the recording medium conveyed by the conveying unit, and the recording head. And a light projecting means for irradiating inspection light passing through the entire width region of the recording medium in the width direction of the recording medium orthogonal to the transport direction on the upstream side of the transport direction of the recording medium by the transport means, and the width A light receiving means disposed on the opposite side of the light projecting means across the recording medium in the direction, receiving the inspection light emitted from the light projecting means and outputting a signal corresponding to the amount of light received; And a slit that is provided in at least one of the light receiving means and the light receiving means and that is long in the transport direction for restricting a passage range of the inspection light.

  According to the present invention, the entire width region of the recording medium can be inspected by the pair of light projecting means and light receiving means arranged in the width direction of the recording medium, and at least one of the light projecting side and the light receiving side is By attaching a long slit in the same direction as the transport direction, the floating of the recording medium can be detected with high accuracy.

  In addition, this slit increases the stability of the detection signal against the optical axis misalignment of the inspection light (angle misalignment, height position misalignment, etc.). Even when this occurs, stable detection is possible.

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

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an overall configuration diagram showing a schematic configuration of an inkjet recording apparatus 100 according to an embodiment of the present invention. An ink-jet recording apparatus 100 (corresponding to an “image forming apparatus”) shown in FIG. 1 is an on-demand image recording apparatus (single-sided) that records a desired color image by ejecting ink of a plurality of colors onto one side of a recording medium 114. A two-liquid aggregation method that forms an image on a recording medium 114 made of a sheet of paper (sometimes referred to as “paper” for convenience) using ink and processing liquid (aggregation processing liquid). Recording device.

  The inkjet recording apparatus 100 includes a paper supply unit 102 that supplies a recording medium 114, a permeation suppression processing unit 104 that performs permeation suppression processing on the recording medium 114, and a processing liquid application unit that applies a processing liquid to the recording medium 114. 106, a printing unit (ink ejection unit) 108 that forms an image by applying color ink to the recording medium 114, and a transparent UV ink application unit 110 that applies transparent UV ink to the recording medium 114, and an image are formed. And a paper discharge unit 112 that conveys and discharges the recording medium 114.

  Although not shown in the drawings, the pressure drums 126a to 126d constituting the conveyance mechanism of the recording medium 114 and the transfer cylinders 124a to 124d provided adjacent to the pressure drums 126a to 126d respectively hold the tip of the recording medium 114. One or a plurality of claws (grippers) are formed, and the recording medium 114 is transferred between the holding claws of the impression cylinder and the transfer cylinder.

  The paper feed unit 102 is provided with a paper feed stand 120 on which the recording media 114 are stacked. A feeder board 122 is connected in front of the paper feed tray 120 (left side in FIG. 1), and the recording media 114 stacked on the paper feed tray 120 are sent to the feeder board 122 one by one in order from the top. The recording medium 114 delivered to the feeder board 122 is fed to the surface (peripheral surface) of the pressure drum 126a of the permeation suppression processing unit 104 via a transfer drum 124a configured to be rotatable in the clockwise direction in FIG. Is done.

(Penetration suppression processing part)
The permeation suppression processing unit 104 applies a permeation suppression agent that suppresses permeation of water and a hydrophilic organic solvent contained in the processing liquid and ink into the recording medium 114. As the permeation inhibitor, a resin in which a resin is dispersed in the form of an emulsion or a resin is dissolved is used. As the solvent, an organic solvent or water is used. As the organic solvent, methyl ethyl ketone, petroleum, and the like are preferably used. The temperature T _{1 of the} recording paper is set higher than the minimum film _forming temperature T _f1 of the resin. The difference between T _f1 and T ₁ is preferably about 10 to 20 ° C. As a result, a good film is immediately formed after the resin adheres to the recording medium 114, and the penetration of the ink applied to the recording medium 114 and the solvent of the treatment liquid into the recording medium 114 is suppressed well. Can do. Adjustment of the temperature of the recording medium 114 includes a method of installing a heating element such as a heater inside the pressure drum 126a, a method of applying hot air from the surface (upper surface) of the recording medium 114, heating using an infrared heater or the like. These may be combined.

  When the curling of the recording medium 114 is difficult to occur, the permeation suppression processing unit 104 can be omitted. For example, the application amount of the penetration inhibitor (including the case where the penetration inhibitor is not applied) may be controlled according to the type of the recording medium 114.

  The permeation suppression processing unit 104 includes a paper preheating unit 128 and a permeation suppression agent head 130 at positions facing the surface of the pressure drum 126a in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 1) of the pressure drum 126a. , And a permeation inhibitor drying unit 132 are provided.

  The paper preheating unit 128 and the permeation suppression agent drying unit 132 are each provided with a heater capable of controlling the temperature within a predetermined range. When the recording medium 114 held on the pressure drum 126a passes through a position facing the paper preheating unit 128 and the permeation suppression agent drying unit 132, it is heated by the heaters of these units.

  The permeation suppressor head 130 ejects a permeation suppressant onto the recording medium 114 held by the pressure drum 126a, and has the same configuration as each of the ink heads 140C, 140M, 140Y, and 140K of the printing unit 108 described later. Applies.

  In this example, an inkjet head is applied as means for performing the permeation suppression process on the surface of the recording medium 114, but the means for performing the permeation suppression process is not particularly limited to this example. For example, various methods such as a spray method and a coating method can be applied.

  In this example, a thermoplastic resin latex solution is suitably used as the penetration inhibitor. Of course, the penetration inhibitor is not limited to the thermoplastic resin latex solution, and for example, tabular grains (mica and the like), water repellent (fluorine coating agent) and the like can be applied.

(Processing liquid application part)
A treatment liquid application unit 106 is provided at the subsequent stage of the permeation suppression processing unit 104 (downstream in the conveyance direction of the recording medium 114). A transfer drum 124b is provided between the pressure drum 126a of the permeation suppression processing unit 104 and the pressure drum 126b of the treatment liquid application unit 106 so as to be in contact with them. With this structure, the recording medium 114 held on the pressure drum 126a of the permeation suppression processing unit 104 is transferred to the pressure drum 126b of the treatment liquid application unit 106 through the transfer drum 124b after the permeation suppression processing is performed. .

  In the treatment liquid application unit 106, a sheet preheating unit 134, a treatment liquid head 136, a position facing the surface of the pressure drum 126 b in order from the upstream side in the rotation direction of the pressure drum 126 b (counterclockwise direction in FIG. 1), And a treatment liquid drying unit 138 are provided.

  Regarding each part of the processing liquid application unit 106 (paper preheating unit 134, processing liquid head 136, and processing liquid drying unit 138), the paper preheating unit 128, the permeation suppression agent head 130, and the permeation suppression of the permeation suppression processing unit 104 described above. Since the same configuration as that of the agent drying unit 132 is applied, description thereof is omitted here. Of course, a configuration different from that of the permeation suppression processing unit 104 can be applied.

  The processing liquid used in this example has a function of aggregating the color materials contained in the ink ejected from the respective ink heads 140C, 140M, 140Y, and 140K disposed in the printing unit 108 in the subsequent stage toward the recording medium 114. It has an acidic liquid.

  The heating temperature of the heater of the processing liquid drying unit 138 is such that the processing liquid applied to the surface of the recording medium 114 is dried by the discharge operation of the processing liquid head 136 disposed on the upstream side in the rotation direction of the pressure drum 126b, and the recording medium is dried. The temperature is set such that a solid or semi-solid aggregation treatment agent layer (a thin film layer obtained by drying the treatment liquid) is formed on 114.

  As used herein, “solid or semi-solid aggregation treatment agent layer” refers to those having a moisture content in the range of 0 to 70% as defined below.

  The “aggregation treatment agent” is used not only in a solid or semi-solid solution but also in a broad concept including other liquids, and particularly in a liquid state with a solvent content of 70% or more. The aggregating agent thus obtained is referred to as “aggregating treatment liquid”.

  As a method for calculating the solvent content of the aggregating agent, a paper having a predetermined size (for example, 100 mm × 100 mm) is cut out, and the total weight after applying the treatment liquid (paper + pre-drying treatment liquid) and the total after the treatment liquid is dried. The weight (paper + post-drying treatment liquid) is measured, and the solvent reduction amount (solvent evaporation) due to drying is obtained from the difference between them. Moreover, what is necessary is just to use the calculated value calculated | required from the preparation prescription of a process liquid as the amount of solvents contained in the process liquid before drying. The solvent content can be obtained from these calculation results.

  Here, Table 1 shows the evaluation results on the movement of the color material when the solvent content of the treatment liquid (aggregation treatment agent layer) on the recording medium 114 is changed.

  As shown in Table 1, when the treatment liquid is not dried (Experiment 1), image degradation occurs due to color material movement.

  On the other hand, when the treatment liquid is dried (Experiments 2 to 5), when the treatment liquid is dried until the solvent content of the treatment liquid becomes 70% or less, the color material movement becomes inconspicuous, and further 50%. It was confirmed that when the treatment liquid was dried to the following level, the color material movement could not be confirmed by visual observation, and it was effective in preventing image deterioration.

  In this way, drying is performed until the solvent content of the treatment liquid on the recording medium 114 becomes 70% or less (preferably 50% or less), and a solid or semi-solid aggregation treatment agent layer is formed on the recording medium 114. By forming the image, it is possible to prevent image deterioration due to color material movement.

  As in this example, it is preferable that the recording medium 114 is preheated by the heater of the paper preheating unit 134 before the treatment liquid is applied onto the recording medium 114. In this case, the heating energy required for drying the treatment liquid can be kept low, and energy saving can be achieved.

[Printing section (ink droplet ejection section)]
A printing unit 108 is provided following the treatment liquid application unit 106. A transfer drum 124c is provided between the pressure drum 126b of the treatment liquid application unit 106 and the pressure drum 126c (corresponding to “conveying means” and “drum”) of the printing unit 108 so as to be in contact with them. Yes. With this structure, the recording medium 114 held on the pressure drum 126b of the treatment liquid application unit 106 is applied with the treatment liquid to form a solid or semi-solid aggregating treatment agent layer, and then passed through the transfer cylinder 124c. Then, it is delivered to the impression cylinder 126 c of the printing unit 108.

  Around the pressure drum 126c, in order from the upstream side with respect to the rotation direction (counterclockwise direction in FIG. 1) of the pressure drum 126c, a sheet pressure roller 502 (corresponding to “medium pressure suppression means”), a sheet floating sensor 504, A paper guide 506 is disposed. The sheet pressing roller 502 directs the recording medium 114 toward the surface of the pressure drum 126c in order to bring the recording medium 114 delivered from the transfer drum 124c into close contact with the peripheral surface of the pressure drum 126c (corresponding to a “medium holding surface”). It is a member to suppress. The sheet pressure roller 502 has a length that can contact the entire surface of the recording medium 114 wound around the impression cylinder 126c (for example, a length in the width direction equivalent to the medium holding area of the impression cylinder 126c).

  The sheet floating sensor 504 is a means for detecting the lifting of the recording medium 114 from the circumferential surface of the impression cylinder 126c. As will be described in detail later, a projector and a light receiver are arranged to face each other along the drum axial direction of the impression cylinder 126c. Consists of configuration.

  The paper guide 506 is a guide member that regulates the lifting of the recording medium 114 from the circumferential surface of the impression cylinder 126c, extends along the drum axial direction of the recording medium 114, and is disposed to face the circumferential surface of the impression cylinder 126c. The The lift of the recording medium 114 is regulated within the range of the clearance (clearance) between the sheet guide 506 and the peripheral surface of the impression cylinder 126c.

  Ink heads 140 </ b> C, 140 </ b> M, 140 </ b> Y, and 140 </ b> K corresponding to recording heads are disposed behind the paper guide 506 (downstream with respect to the rotation direction of the pressure drum 126 c). That is, the printing unit 108 includes C (cyan), M (magenta), M (magenta), and a position facing the surface of the impression cylinder 126c in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 1) of the impression cylinder 126c. Ink heads 140C, 140M, 140Y, and 140K corresponding to four colors of Y (yellow) and K (black), respectively, and solvent drying units 142a and 142b are provided.

  In each of the ink heads 140C, 140M, 140Y, and 140K, the perpendicular direction of the respective ink discharge surface coincides with the normal direction of the peripheral surface of the impression cylinder 126c, and the ink discharge surface of each head 140C, 140M, 140Y, and 140K has a pressure. The heads 140C, 140M, 140Y, and 140K are arranged so that the droplet ejection position and distance on the drum 126c (on the recording medium 114) are the same for the heads 140C, 140M, 140Y, and 140K. Thus, by arranging the heads 140C, 140M, 140Y, and 140K in an arc around the impression cylinder 126c, the landing position accuracy resulting from the droplet ejection distance is ensured, and a high-quality image can be formed.

  As each of the ink heads 140C, 140M, 140Y, and 140K, an ink jet recording head (ink jet head) is applied in the same manner as the above-described permeation suppressor head 130 and the treatment liquid head 136. That is, each of the ink heads 140C, 140M, 140Y, and 140K discharges the corresponding color ink droplets toward the recording medium 114 held by the pressure drum 126c.

  Each of the ink heads 140C, 140M, 140Y, and 140K has a length corresponding to the maximum width of the image forming area in the recording medium 114 held by the pressure drum 126c, and the entire width of the image forming area is formed on the ink discharge surface. A full-line head in which a plurality of nozzles for ink ejection (not shown in FIG. 1, not shown in FIG. 2 with reference numeral 161) is arranged. The ink heads 140C, 140M, 140Y, and 140K are fixedly installed so as to extend in a direction orthogonal to the rotation direction of the impression cylinder 126c (the conveyance direction of the recording medium 114).

  According to the configuration in which a full line head having a nozzle row covering the entire width of the image forming area of the recording medium 114 is provided for each ink color, the recording medium 114 and each ink in the transport direction (sub-scanning direction) of the recording medium 114 The primary image can be recorded in the image forming area of the recording medium 114 by performing the operation of relatively moving the heads 140C, 140M, 140Y, and 140K only once (that is, by one sub-scan). As a result, printing can be performed at a higher speed than when a serial (shuttle) type head that reciprocates in the direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium 114 is applied. Can be improved.

  In this example, the configuration of four colors of CMYK is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are added as necessary. May be omitted. For example, a configuration in which ink heads for ejecting light-colored inks such as light cyan and light magenta are added, and a seven-color configuration of CMYKRGB is possible, and the arrangement order of the color heads is not particularly limited.

  The solvent drying units 142a and 142b are configured to include a heater capable of controlling the temperature within a predetermined range, similar to the paper preheating units 128 and 134, the permeation suppression agent drying unit 132, and the treatment liquid drying unit 138 described above. As will be described later, when ink droplets are ejected onto the solid or semi-solid aggregation processing agent layer formed on the recording medium 114, an ink aggregate (coloring material aggregate) is formed on the recording medium 114. ) And the ink solvent separated from the color material spreads, and a liquid layer in which the aggregating agent is dissolved is formed. In this way, the solvent component (liquid component) remaining on the recording medium 114 causes not only curling of the recording medium 114 but also image degradation. Therefore, in this example, after the corresponding color inks are ejected onto the recording medium 114 from the respective ink heads 140C, 140M, 140Y, and 140K, the solvent components are heated by the heaters of the solvent drying units 142a and 142b. Evaporate and dry.

[Transparent UV ink application part]
A transparent UV ink application unit 110 is provided at the subsequent stage of the printing unit 108. A transfer drum 124d is provided between the pressure drum 126c of the printing unit 108 and the pressure drum 126d of the transparent UV ink applying unit 110 so as to be in contact with them. Accordingly, the recording medium 114 held on the pressure drum 126c of the printing unit 108 is delivered to the pressure drum 126d of the transparent UV ink application unit 110 via the transfer drum 124d after each color ink is applied.

  In the transparent UV ink application unit 110, printing that reads the printing result by the printing unit 108 at a position facing the surface of the pressure drum 126d in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 1) of the pressure drum 126d. A detection unit (inline sensor) 144, a transparent UV ink head 146, and first UV lamps 148a and 148b are provided.

  The print detection unit 144 includes an image sensor (line sensor or the like) for imaging the print results of the print unit 108 (droplet ejection results of the ink heads 140C, 140M, 140Y, and 140K). It functions as a means for checking clogging of nozzles and other ejection defects and droplet ejection image unevenness (density unevenness) from the droplet image.

  In this example, a test pattern is formed in the image recording area or non-image portion of the recording medium 114 (see FIG. 8), the test pattern is read by the print detection unit 144, and color information acquisition (measurement) is performed based on the read result. Color) and density unevenness, and in-line detection such as determination of the presence or absence of ejection abnormality for each nozzle.

  The print detection unit 144 applied to this example includes a line CCD in which a plurality of detection pixels (photoelectric conversion elements) are arranged in one or a plurality of rows along the width direction of the recording medium 114 (or two detection pixels are two in number). It is a configuration including a dimensionally arranged area sensor) and a lens arranged so that the width direction of the recording medium 114 can be collectively read by a line CCD (or area sensor). In addition, instead of a line sensor having an inspection visual field capable of collectively reading the recordable width, a sensor having a reading range narrower than this may be used to read while moving (scanning) the reading position.

  The transparent UV ink head 146 has the same configuration as the ink heads 140C, 140M, 140Y, and 140K of the printing unit 108, and the color ink that has been ejected onto the recording medium 114 by the ink heads 140C, 140M, 140Y, and 140K. The transparent UV ink is ejected so as to overlap with the ink. Of course, it is also possible to apply a different configuration from the ink heads 140C, 140M, 140Y, and 140K of the printing unit 108.

  The first UV lamps 148a and 148b are formed on the recording medium 114 when the recording medium 114 passes through a position facing the first UV lamp 148 after the transparent UV ink is deposited on the recording medium 114. The transparent UV ink is irradiated with UV light (ultraviolet light) to cure the transparent UV ink.

  In this example, the print control unit 182 (see FIG. 5), which will be described later, is transparent so that the layer thickness of the transparent UV ink after UV light irradiation is 5 μm or less (preferably 3 μm or less, more preferably 1 to 3 μm). Control of the amount of liquid droplets ejected from the nozzles of the UV ink head 146 (droplet amount of transparent UV ink) is performed. In FIG. 1, “layer thickness of transparent UV ink after UV light irradiation” is a layer thickness of transparent UV ink after UV light is irradiated by a second UV lamp 156 described later. That is, when a plurality of UV lamps are provided, the layer thickness of the transparent UV ink after the UV light irradiation is performed by the UV lamp on the most downstream side in the recording medium conveyance direction.

[Paper output section]
A paper discharge unit 112 is provided following the transparent UV ink application unit 110. The paper discharge unit 112 includes a paper discharge drum 150 that receives the recording medium 114 on which the transparent UV ink is ejected, a paper discharge tray 152 on which the recording medium 114 is loaded, and a sprocket provided on the paper discharge drum 150. A paper discharge chain 154 provided with a plurality of paper discharge grippers is provided between a sprocket provided above the paper board 152.

  Between these sprockets, a second UV lamp 156 is provided inside the paper discharge chain 154. The second UV lamp 156 is used until the recording medium 114 transferred from the pressure drum 126d of the transparent UV ink applying unit 110 to the paper discharge drum 150 is conveyed to the paper discharge tray 152 by the paper discharge chain 154. The transparent UV ink on the recording medium 114 is irradiated with UV light (ultraviolet light) to cure the transparent UV ink.

  FIG. 1 illustrates a three-component inkjet recording apparatus 100 including a permeation suppression processing unit 104 and a processing liquid application unit 106, but these processing blocks are appropriately changed and omitted according to the performance of the ink used. be able to.

[Example of head structure]
Next, the structure of the ink heads 140C, 140M, 140Y, and 140K arranged in the printing unit 108 will be described in detail. Since the structures of the ink heads 140C, 140M, 140Y, and 140K are the same, the ink head (hereinafter also simply referred to as “head”) is denoted by reference numeral 160 in the following.

  2A is a perspective plan view showing an example of the structure of the head 160, FIG. 2B is an enlarged view of a part thereof, and FIG. 2C is a plan view showing another example of the structure of the head 160. FIG. FIG. 3 is a cross-sectional view (FIGS. 2A and 2B) showing a three-dimensional configuration of a one-channel droplet discharge element (an ink chamber unit corresponding to one nozzle 161) serving as a recording element unit. 3 is a cross-sectional view taken along line 3-3).

  In order to increase the dot pitch formed on the recording medium 114, it is necessary to increase the nozzle pitch in the head 160. As shown in FIGS. 2A and 2B, the head 160 of this example includes a plurality of ink chamber units 163 including nozzles 161 serving as ink droplet ejection holes, pressure chambers 162 corresponding to the nozzles 161, and the like. Are arranged in a staggered matrix (two-dimensionally) so that they are arranged along the longitudinal direction of the head (main scanning direction perpendicular to the recording medium transport direction (sub-scanning direction)). High density of the substantial nozzle interval (projection nozzle pitch) to be projected is achieved.

  The configuration in which one or more nozzle rows are configured in a direction substantially orthogonal to the conveyance direction of the recording medium 114 over a length corresponding to the entire width of the recording medium 114 is not limited to this example. For example, instead of the configuration of FIG. 2A, as shown in FIG. 2C, short head blocks 160 ′ in which a plurality of nozzles 161 are two-dimensionally arranged are arranged in a staggered manner and connected. A line head having a nozzle row having a length corresponding to the entire width of the recording medium 114 may be configured. Although not shown, a line head may be configured by arranging short heads in a line.

  The pressure chamber 162 provided corresponding to each nozzle 161 has a substantially square planar shape, and the nozzle 161 and the supply port 164 are provided at both corners on the diagonal line. As shown in FIG. 3, each pressure chamber 162 communicates with a common flow path 165 through a supply port 164. The common flow path 165 communicates with an ink supply tank (not shown in FIG. 3; indicated by reference numeral 170 in FIG. 4) as an ink supply source, and the ink supplied from the ink supply tank passes through the common flow path 165. Distribution is supplied to each pressure chamber 162.

  As shown in FIG. 3, a piezoelectric element 168 having an individual electrode 167 is joined to a diaphragm 166 that constitutes a part of the pressure chamber 162 (the top surface in FIG. 3) and also serves as a common electrode. By applying a driving voltage to the individual electrode 167, the piezoelectric element 168 is deformed and ink is ejected from the nozzle 161. When ink is ejected, new ink is supplied from the common channel 165 to the pressure chamber 162 through the supply port 164.

  In this example, the piezoelectric element 168 is applied as an ejection force generation unit for ink ejected from the nozzles 161 provided in the head 160. However, a heater is provided in the pressure chamber 162, and the pressure of film boiling caused by heating of the heater is used. It is also possible to apply a thermal method that ejects ink.

  As shown in FIG. 2B, the ink chamber units 163 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle arrangement of this example is realized.

  That is, with the structure in which a plurality of ink chamber units 163 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 161 can be handled equivalently as a linear array with a constant pitch P.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied.

  Further, the scope of application of the present invention is not limited to the printing method using a line type head, and a short head that is less than the length in the width direction (main scanning direction) of the recording medium is scanned in the width direction of the recording medium to obtain the width. When printing in the width direction is completed, the print medium is moved by a predetermined amount in the direction (sub-scanning direction) perpendicular to the width direction of the recording medium, and printing in the width direction of the recording medium in the next printing area is performed. It is also possible to apply a serial method in which this operation is repeated and printing is performed over the entire printing area of the recording medium.

[Configuration of ink supply system]
FIG. 4 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 100. The ink supply tank 170 is a base tank that supplies ink to the head 160. The ink supply tank 170 includes a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink is low. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

  As shown in FIG. 4, a filter 171 is provided between the ink supply tank 170 and the head 160 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 4, a configuration in which a sub tank is provided in the vicinity of the head 160 or integrally with the head 160 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 100 is provided with a cap 172 as a means for preventing the nozzle 161 from drying or preventing an increase in ink viscosity near the nozzle 161 and a cleaning blade 173 as a means for cleaning the ink ejection surface of the head 160. ing. The cap 172 can be moved relative to the head 160 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the head 160 as necessary.

  The cap 172 is displaced up and down relatively with respect to the head 160 by an elevator mechanism (not shown). The cap 172 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the head 160, thereby covering the nozzle surface with the cap 172.

  During printing or standby, when the frequency of use of a specific nozzle 161 is low and ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. In such a state, ink cannot be ejected from the nozzle 161 even if the piezoelectric element 168 (see FIG. 3) operates.

  Before such a state is reached (within the range of viscosity that can be discharged by the operation of the piezoelectric element 168), the piezoelectric element 168 is operated, and a cap is formed to discharge the deteriorated ink (ink near the nozzle whose viscosity has increased). Preliminary ejection (purging, idle ejection, spit ejection, dummy ejection) is performed toward 172 (ink receiving).

  Further, when air bubbles are mixed in the ink in the head 160 (in the pressure chamber 162; see FIG. 3), the ink cannot be ejected from the nozzle even if the piezoelectric element 168 is operated. In such a case, the cap 172 is applied to the head 160, and the ink in the pressure chamber 162 (ink mixed with bubbles) is removed by suction with the suction pump 174, and the suctioned and removed ink is sent to the recovery tank 175.

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 162, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

  The head 160 is configured to perform maintenance after the head 160 is moved from an image forming position (printing position) immediately above the pressure drum 126c (sometimes referred to as “drum”) to a predetermined maintenance position. Has been.

[Main components of the printing unit]
FIG. 5 is a side view of a main part of the printing unit 108 in the inkjet recording apparatus 100 of the present example. FIG. 6 is a plan view showing the configuration of the paper floating sensor 504.

  As shown in FIG. 5, the sheet floating sensor 504 is disposed between the sheet pressing roller 502 and the sheet guide 506 with respect to the rotational direction of the impression cylinder 126c. With such an arrangement, it is possible to stably detect the floating of the sheet in the entire area from the front end to the rear end of the recording medium 114.

  The paper guide 506 is disposed in front (upstream side) of the ink head 140C. The distance from the surface of the impression cylinder 126c to the leading end of the paper guide 506 is such that the recording medium 114 does not contact the ink head 160 even when the recording medium 114 is stopped in a state of being in contact with the paper guide 506 due to the floating of the recording medium 114. In addition, it is managed at a predetermined distance (clearance). The height position of the paper guide 506 can be adjusted in the drum normal direction by a height adjustment mechanism (not shown), and the height position of the paper guide 506 is controlled in accordance with the thickness of the recording medium 114. As a result, the same clearance can be maintained for the recording media 114 having different thicknesses.

  Although the illustration of the configuration of the impression cylinder 126c is omitted, a number of suction holes are arranged on the peripheral surface of the impression cylinder 126c in accordance with a predetermined arrangement pattern, and the area where the plurality of suction holes are arranged sucks and holds the recording medium. Function as a recording medium holding area. The suction hole communicates with a suction channel provided inside the pressure drum 126c, and is connected to an external suction device (pump) through the suction channel. Instead of the negative pressure suction method described above, an electrostatic adsorption method in which the recording medium 114 is held in the recording medium holding area of the pressure drum 126c by static electricity may be applied. By holding the recording medium 114 by negative pressure adsorption or electrostatic adsorption, the conveyance becomes stable, so that conveyance defects can be reduced. However, the lift of the sheet occurs due to various factors such as poor adsorption and moisture absorption of the recording medium 114.

  As shown in FIG. 6, the paper floating sensor 504 includes a pair of a projector 512 and a light receiver 514. The light projector 512 and the light receiver 514 are arranged on the left and right sides of the impression cylinder 126c, and one side (left in the example of FIG. 6) is a light projector, and the other is a light receiver. In addition, the form which replaces the arrangement | positioning relationship of the light projector 512 and the light receiver 514 is also possible. Various light emitting elements such as an LED and a laser can be used for the projector 512. For the light receiver 514, photoelectric conversion electrons that output an electrical signal corresponding to the amount of received light can be used.

  The optical axis of the inspection light emitted from the light projector 512 is substantially parallel to the axial direction (drum axial direction) of the impression cylinder 126c, and the inspection light passes near the surface of the impression cylinder 126c on which the recording medium 114 (paper) is held. The luminous flux passes through.

  Since the recording medium 114 is lifted from the impression cylinder 126c, part of the inspection light is blocked and the amount of light incident on the light receiver (the amount of received light) is reduced. Therefore, the lift of the recording medium 114 is detected by a signal obtained from the light receiver. can do.

  In FIG. 6, reference numerals 520 and 522 denote support frames that rotatably support the impression cylinder 126c. The projector 512 and the light receiver 514 are attached to the support frame 520 (or 522) via position and angle adjustment mechanisms (reference numerals 530 in FIGS. 5 and 7), respectively.

  FIG. 7 is an enlarged perspective view of a mounting portion of the light receiver 514 (or the projector 512). Although only one side is shown in the figure, the same structure is provided on the opposite side to FIG.

  The adjusting mechanism 530 can adjust each position in the drum axial direction (X-axis direction), the drum tangential direction (Y-axis direction), and the drum normal direction (Z-axis direction), and the rotation angle around each axis. Provide mechanism.

<Ingenuity for high-precision detection>
In front of the light receiving surface of the light receiver 514 and the light emitting surface of the projector 512 in this example, as shown in FIG. 8, slits 540 for restricting the inspection light passing range are arranged. The slit 540 is a slit having a long and narrow opening in substantially the same direction as the drum tangential direction (Y direction in FIG. 7) at the inspection light passing position (light receiving position) in the circumferential direction of the impression cylinder 126c. In this manner, a form in which long slits are arranged in the drum tangential direction is referred to as “slit side” for convenience.

  For comparison, as shown in FIG. 9, a mode in which long slits 544 are arranged in the drum normal direction is referred to as “slit length”.

  It has been experimentally confirmed that the detection accuracy varies greatly depending on the direction (longitudinal direction) of the slit disposed in front of the light receiving surface of the light receiver 514 and the light emitting surface of the projector 512.

  The effect of the slit was examined using two indicators, a change in detection position due to an optical axis shift and a change in detection unstable region.

(First evaluation index: Change in detection position due to optical axis deviation)
When the angle between the light projector 512 and the light receiver 514 changes, the change in how much (how many millimeters) of the sheet float can actually be detected was examined. This is because, in the initial state, such as when the apparatus is assembled (shipment), the optical axis is adjusted so as to detect the sheet float of height Z0 from the surface of the impression cylinder 126c. This is an investigation of how much change occurs in the detected height due to a slight change in the angle of the outgoing optical axis of the projector and the angle of the light receiving surface of the light receiver due to changes after assembly of the device.

  In the experiment, slits having the same shape were provided in both the projector and the light receiver, and it was investigated how much the detection of the sheet floating is affected by the optical axis shift (here, the angle change from the reference optical axis). The experimental results are shown in FIGS. The projector side is denoted as “A” and the light receiver side is denoted as “B”, and the rotation angle around the Y axis and the rotation angle around the Z axis were examined. For example, “θYA” indicates an experimental result when the rotation angle of the projector around the Y axis is changed.

  As is clear from comparison of the graphs of the experimental results (FIGS. 10 and 11), regarding the direction of the slit, the lateral slit can detect very stably against the optical axis shift.

  In the case of a vertical slit, even if the optical axis of the sensor is slightly shifted, it is detected as a large positional shift.

  By making the light receiving slit sideways (in the drum tangential direction), even if the optical axes of the projector and the light receiver are slightly deviated, the change in the position for detecting the sheet floating can be reduced.

(Second evaluation index: change in detection unstable region)
FIG. 12 is a graph showing the relationship between the amount of floating paper and the amount of received light. The light receiver 514 outputs a detection signal corresponding to the amount of received light. As shown in the drawing, the amount of received light decreases when the amount of lifting of the paper exceeds the specified amount, and the amount of received light becomes “0” when the inspection light is completely blocked by the lifting of the paper.

From the amount of light received correlation with paper floating amount as shown, and is specified in the reference value S a (paper floating quantity corresponding to the threshold value T _H of the detected light intensity) as a boundary, it is judged whether the paper floating. Before and after the reference value S, detection becomes unstable.

  The extent to which the graph has a large slope (detection unstable region) was examined as an index related to detection stability or repeated stability.

  In determining the range (Ca to Cb) where the light reception amount (output) decreases by a% to b% with respect to the maximum light reception amount (maximum output value) as the unstable region, “a% ”And“ b% ”can be designed in various ways. In the experiment of this example, a% = 20% and b% = 80%. The slower the change in the amount of light received with respect to the change in the paper floating amount, the lower the detection stability. Conversely, the more the light amount changes with respect to the change in the paper floating amount, the more stable the detection. Can be evaluated to be high.

  FIG. 13 and FIG. 14 show the experimental results of examining changes in the detection unstable region due to the optical axis shift (angle). As is clear from the comparison of both figures, stable detection is possible on the side of the slit (FIG. 13).

  In this way, by making the slit of the light receiver sideways (in the drum tangential direction), even when there is an optical axis misalignment, it is possible to keep the unstable area when detecting paper floating small, and to improve the detection position accuracy. Can be increased.

  FIGS. 15 and 16 show changes in the unstable region when the height (position in the Z direction) of the projector and the light receiver is changed. It was confirmed that the lateral slits were more stable with respect to changes in the detected height.

<Support for multiple types of paper thickness>
The ink jet recording apparatus 100 of this example includes a head height adjustment mechanism (not shown) that can change the height of the head 160 (the height position in the drum normal direction) with respect to the surface of the impression cylinder 126c. The height of the head 160 is changed in accordance with the thickness of the recording medium 114 to be recorded. The head height may be controlled in conjunction with the selection of the paper type, or a measuring means for measuring the thickness of the medium is provided in the conveyance path of the recording medium 114 to actually measure the thickness of the recording medium 114. The height of the head may be controlled from the thickness information obtained in this way. Thereby, the interval (clearance) between the printing surface of the recording medium 114 and the nozzle surface of the head 160 can be kept constant regardless of the thickness of the recording medium 114.

Further, in order to be able to detect the same lifting amount for the recording media 114 having different thicknesses, the detected light amount (threshold value T _H described with reference to FIG. 12) is detected depending on the thickness of the recording medium used. To change.

  As a result, the detected lift amount can be kept constant for the recording media 114 having different thicknesses without changing the height position of the projector 512 and the light receiver 514.

  A mode in which a plurality of projectors and light receivers having different detection heights are installed instead of the mode in which the threshold value is changed according to the sheet thickness is also possible. That is, in the drum normal direction, a plurality of pairs of light projectors and light receivers having different detection heights are provided, and a sensor pair to be used is selected according to the thickness of the recording medium to be used. When the recording medium is thin, the lower sensor is used. When the recording medium is thick, the upper sensor is used. As a result, it is possible to detect the paper with different thicknesses with the same lifting amount.

<About the combination of slits>
In the above description, slits having the same shape are disposed on the light projecting surface of the light projector 512 and the light receiving surface of the light receiver 514, respectively, but a corresponding effect can be obtained even when the slits are provided on only one of them. Note that in the case where the slit is provided only in one of them, it is preferable that the slit is provided only in the light receiver 514 rather than the slit provided only in the projector 512.

<Description of structure of impression cylinder (conveyance drum)>
Next, an example of the structure of the impression cylinder 126c that functions as means for holding and transporting the recording medium 114 in the printing unit 108 will be described. Since the impression cylinders 126a to 126d shown in FIG. 1 have a common structure, the impression cylinders 126a to 126d will be collectively referred to as a conveyance drum 300 hereinafter.

  FIG. 17 is a perspective view of the transport drum 300 according to the embodiment of the present invention. As shown in the figure, the transport drum 300 has a cylindrical shape, and the rotating shaft 302 is supported by bearings 304 at both ends in the longitudinal direction. By rotating the rotating shaft 302, the outer peripheral surface 306 is formed. A held recording medium (not shown) is conveyed in a predetermined direction.

  The outer peripheral surface 306 of the transport drum 300 is provided with a plurality of recesses, and each recess is provided with an end holding portion that holds and fixes the leading end of the recording medium. FIG. 17 illustrates an example in which two concave portions 308 and 310 are provided at positions that are symmetrical with respect to the rotation axis of the transport drum 300. In addition, like the impression cylinder 126c of the printing unit 108 shown in FIG. 1, a mode in which three concave portions are provided at a position where the outer peripheral surface is equally divided (at a position where each concave portion is 120 °) is possible. is there. In the embodiment shown in FIG. 1, a mechanism for holding the tip of the recording medium 114 is provided at two locations of the transfer cylinders 124a to 124d, and the transfer structure for transferring the recording medium 114 from the upstream impression cylinder to the downstream impression cylinder. When the transfer drums 124a to 124d make one round, the pressure drums 126a, 126b, and 126d are halved and the pressure drum 126c is １ ／, and the recording medium 114 is sequentially transferred.

  The concave portion 308 (310) is provided with a paper front end guide 314 having an end fixing surface 312 to which the front end of the recording medium is fixed along the longitudinal direction of the transport drum 300, and further, an end of the paper front end guide 314. A plurality of grippers 316 sandwiching and sandwiching the leading end portion of the recording medium with the fixed surface 312 are provided at predetermined intervals (equal intervals in the example of FIG. 17) along the longitudinal direction of the transport drum 300.

  When the recording medium is transferred from the transfer cylinder 124c to the impression cylinder 126c, the gripper 316 is opened to guide the leading end portion of the recording medium between the gripper 316 and the end fixing surface 312, and the gripper 316 is closed to close the leading end of the recording medium. The portion is sandwiched between the paper front end guide 314.

  In this way, by sandwiching the leading end of the recording medium with the impression cylinder 126c, it is possible to prevent the leading end of the sheet from being removed, and it is possible to reliably detect the floating of the sheet.

<Description of vacuum flow path of impression cylinder (conveyance drum)>
Next, the vacuum flow path of the transport drum 300 will be described in detail. A plurality of suction holes are provided in a predetermined arrangement pattern in a recording medium holding area 414 (area shown by a dot hatch) for holding a recording medium on the outer peripheral surface 306 of the conveying drum 300 shown in FIG. Furthermore, a substantially central portion in the axial direction of the transport drum 300 is a non-opening portion 416 in which suction holes are not provided over the entire circumference in the circumferential direction. In FIG. 17, illustration of individual suction holes is omitted, and reference numeral 450 is assigned to FIG. 18 to show individual suction holes.

  The suction hole communicates with an adsorption pipe line (details are shown in FIGS. 18 and 19) inside the conveyance drum 300, and the adsorption pipe line communicates with a vacuum pipe line (not shown) inside the conveyance drum 300. The vacuum line communicates with a connecting portion 320 provided on the side surface portion of the transport drum 300, a suction hose 322, and a connecting portion 326 provided on the side surface of the manifold 324, and is connected to a pump (not shown in FIG. 17).

  The four suction hoses 322 (coupling portions 320 and 326) shown in FIG. 17 correspond to the four drum suction grooves 426 (only one is shown in FIG. 17) provided on the outer peripheral surface 356A of the main body portion 356. is doing.

  The pump is operated in a state where the recording medium is held in the recording medium holding area 414, and a vacuum (negative pressure) is generated in the suction hole of the outer peripheral surface 306 through the above-described vacuum flow path and suction pipe path in the transport drum 300. Thus, the recording medium can be vacuum-sucked to the recording medium holding area 414.

  As shown in FIG. 17, the transport drum 300 has a suction sheet 420 provided with a plurality of suction holes, and a plurality of suction grooves 422 (flow path forming portions having openings) communicating with the suction holes. And an intermediate sheet 424 provided in accordance with the arrangement pattern, and further, a drum suction groove 426 communicating with a throttle portion (not shown in FIG. 17 and indicated by reference numeral 434 in FIG. 18) provided in each suction groove 422. The main body 356 is provided.

  Furthermore, at the end of the drum suction groove 426 provided in the main body 356, a drum suction hole 428 (suction pipe) communicating with the suction hose 322 via a vacuum channel (not shown) provided in the main body 356 is provided. Road).

  The conveyance drum 300 is aligned with the drum suction groove 426 of the main body portion 356 and the throttle portion of the intermediate sheet 424, and the intermediate sheet 424 is wound around the outer peripheral surface of the main body portion 356 so as to be closely attached and fixed. The suction groove 422 of the intermediate sheet 424 and the suction hole of the suction sheet 420 are aligned so that the suction hole provided in the intermediate sheet 424 communicates with any suction groove 422 of the intermediate sheet 424, and the suction sheet is placed on the intermediate sheet 424. It has a structure in which 420 is wound and closely attached.

  The arrangement pattern of the suction holes provided in the suction sheet 420 preferably corresponds to the pattern of the suction grooves 422 of the intermediate sheet 424. Note that some of the suction holes may not communicate with the suction groove 422.

  18 and 19 show the arrangement relationship among the suction holes 450, the suction grooves 422, the drum suction grooves 426, and the drum suction holes 428 (suction conduits). 18 is a plan view seen from the outer peripheral surface side of the transport drum, and FIG. 19 is a cross-sectional view taken along line BB in FIG. However, FIG. 19 is enlarged in the depth direction for easy understanding.

  As shown in FIG. 18, the width of the suction groove 422 (the length in the vertical direction in FIG. 18) has a length corresponding to the plurality of suction holes. In FIG. 18, the width of the suction groove 422 is the suction hole. The aspect which becomes about 4 times the diameter (length in a major axis direction) of 450 is shown.

  The width of the drum suction groove 426 (the length in the left-right direction in FIG. 18) is shorter than the length of the throttle portion 434 (the length in the left-right direction in FIG. 18). A mode in which the width of the groove 426 is approximately ½ of the length of the throttle portion 434 is shown. Further, the throttle portion 434 has a length that reaches a position beyond the drum suction groove 426 (a structure in which there is a portion protruding on the left side of the drum suction groove 426 in FIG. 18).

  As shown in FIG. 18, the width of the throttle portion 434 (the vertical length in FIG. 18) is narrower than the width of the suction groove 422 (the horizontal length in FIG. 18). As shown, the depths of the throttle 434 and the suction groove 422 are substantially the same. That is, the cross-sectional area of the throttle portion 434 is smaller than the cross-sectional area of the suction groove 422, and the flow rate of the suction groove 422 is limited by the structure of the throttle portion 434.

  As shown in FIG. 19, the thickness of the suction sheet 420 is thicker than the thickness of the intermediate sheet 424. In FIG. 19, the thickness of the intermediate sheet 424 with respect to the thickness of the suction sheet 420 is approximately ½. Is illustrated.

[Description of system control system]
FIG. 20 is a principal block diagram showing the system configuration of the inkjet recording apparatus 100. The inkjet recording apparatus 100 includes a communication interface 176, a system controller 177, a memory 178, a motor driver 179, a heater driver 180, a fixing process control unit 181, a print control unit 182, an image buffer memory 183, a head driver 184, a pump driver 195, and maintenance. A processing control unit 197 and the like are provided.

  The communication interface 176 is an interface unit that receives image data sent from the host computer 186. As the communication interface 176, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 186 is taken into the inkjet recording apparatus 100 via the communication interface 176 and temporarily stored in the memory 178.

  The memory 178 is a storage unit that temporarily stores an image input via the communication interface 176, and data is read and written through the system controller 177. The memory 178 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 177 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 177 controls each part such as the communication interface 176, the memory 178, the motor driver 179, the heater driver 180, etc., performs communication control with the host computer 186, read / write control of the memory 178, etc. Control signals for controlling the motor 188, the heater 189, and the pump 196 are generated.

  The memory 178 stores programs executed by the CPU of the system controller 177 and various data necessary for control. Note that the memory 178 may be a non-rewritable storage unit, or may be a rewritable storage unit such as an EEPROM. The memory 178 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  Various control programs are stored in the program storage unit 190, and the control programs are read and executed in accordance with instructions from the system controller 177. The program storage unit 190 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media. The program storage unit 190 may also be used as a storage unit (not shown) for operating parameters.

  The motor driver 179 is a driver that drives the motor 188 in accordance with an instruction from the system controller 177. In FIG. 20, a motor (actuator) arranged in each part in the apparatus is represented by reference numeral 188. For example, the motor 188 shown in FIG. 20 includes the pressure drums 126a to 126d (the conveyance drum 300 in FIG. 17), the transfer drums 124a to 124d, the motor that drives the paper discharge drum 150, and the like.

  The heater driver 180 is a driver that drives the heater 189 in accordance with an instruction from the system controller 177. In FIG. 20, a plurality of heaters provided in the ink jet recording apparatus 100 are represented by reference numeral 189. For example, the heater 189 shown in FIG. 20 includes the paper preheating units 128 and 134, the permeation suppression agent drying unit 132, the treatment liquid drying unit 138, the solvent drying units 142a and 142b shown in FIG.

  The fixing processing unit 110 in FIG. 20 is illustrated as the transparent UV ink applying unit 110 in FIG. That is, FIG. 1 illustrates a mode in which a transparent UV ink layer is formed on the surface of an image as one mode of the fixing processing unit 110 in FIG. The fixing processing unit 110 is not limited to a mode in which a layer of transparent UV ink is formed, and a mode in which a recording medium after image formation is heated by a heating unit such as a heater, or a recording by a pressure unit such as a pressure roller. A mode in which an image formed on a medium is pressed, a mode in which heating and pressurization using a pressure roller with a built-in heater are used in combination may be applied.

  The fixing processing control unit 181 functions as a UV light irradiation control unit that controls the UV light irradiation amount and the UV light irradiation timing of the first UV lamps 148a and 148b in FIG. The optimum irradiation time, irradiation interval, and irradiation intensity of each UV lamp 148a, 148b, and 156 are obtained in advance for each type of recording medium 114 and transparent UV ink, and are converted into a data table and stored in a predetermined memory (for example, memory 178), the fixing process control unit 181 acquires the information of the recording medium 114 and the information of the ink used, and refers to the memory to determine the irradiation time, irradiation interval, and irradiation intensity of each UV lamp 148a, 148b, 156. Control appropriately.

  By controlling the irradiation time, irradiation interval, and irradiation intensity of each of the UV lamps 148a, 148b, and 156, the glossiness (surface shape) of the image can be controlled, and images with different glossiness can be realized. For example, the first UV lamps 148a and 148b increase the viscosity of the transparent UV ink in the vicinity of the interface with the recording medium 114 to suppress the penetration of the transparent UV ink into the recording medium 114, and are transparent by the second UV lamp 156. The UV ink can be cured from the inside to the surface. Instead of (or with these controls) controlling the irradiation time, irradiation interval, and irradiation intensity of each UV lamp 148a, 148b, 156, the speed at which the recording medium 114 is conveyed may be controlled. The positions of the UV lamps 148a, 148b, and 156 may be changed. In addition, a drying unit is added between the first UV lamps 148a and 148b and the second UV lamp 156, and after the transparent UV ink is deposited, the recording medium is recorded by the first UV lamps 148a and 148b. The transparent UV ink may be cured by the second UV lamp 156 after removing the solvent in the transparent UV ink by the drying unit while suppressing the permeation of the transparent UV ink to 114.

  Note that the fixing process control unit 181 appropriately determines a control target depending on the configuration of the fixing process unit 110.

  The pump driver 195 controls on / off of the pump 196 and generated pressure. The pump 196 in FIG. 20 includes pumps provided in each part of the apparatus, such as the suction pump 174 in FIG. 4 and the pump for suction adsorption in the impression cylinder 126c.

  For example, in the apparatus configuration shown in FIG. 1, when the recording medium 114 that has undergone predetermined processing is supplied to the pressure drum 126c of the printing unit 108, the pump connected to the vacuum flow path of the pressure drum 126c is operated, A vacuum (negative pressure) corresponding to the type and size of the recording medium 114 and the bending rigidity is generated.

  That is, when the system controller 177 acquires information on the type of the recording medium 114, the information on the recording medium 114 is sent to the pump driver 195 in FIG. The pump driver 195 sets the adsorption pressure according to the information of the recording medium 114, and controls the on / off of the pump 196 and the generated pressure according to the setting.

  When a recording medium 114 having a lower bending rigidity than the standard bending rigidity such as thin paper is used, the adsorption pressure is set lower than the standard, and a recording medium 114 having a higher bending rigidity than the standard bending rigidity such as cardboard is used. In this case, the adsorption pressure is set higher than the standard. Further, when a recording medium 114 thicker than the standard thickness is used according to the thickness of the recording medium 114, the suction pressure is set higher than the standard, and when the recording medium 114 thinner than the standard thickness is used, the standard is used. Set the adsorption pressure lower than. It should be noted that the type (thickness, bending rigidity) of the recording medium 114 and the adsorption pressure are associated with each other to form a data table and stored in a predetermined memory (for example, the memory 178 in FIG. 20).

  In the apparatus configuration shown in FIG. 1, each of the impression cylinders 126a to 126d and the transfer cylinders 124a to 124d may be provided with a pump for generating an adsorption force, and a switching means such as a control valve is provided in the middle of the vacuum flow path. It is also possible to selectively switch one pump to correspond to a plurality of impression cylinders 126a to 126d and a plurality of transfer cylinders 124a to 124d.

  The maintenance processing control unit 197 is a functional block that controls the maintenance processing unit 198 that performs maintenance of each part of the apparatus such as the head 160 and the impression cylinders 126a to 126d based on a control signal sent from the system controller 177.

  In FIG. 20, the maintenance processing unit 198 is illustrated as one functional block. However, like the maintenance processing unit of the head 160 and the maintenance processing units of the impression cylinders 126a to 126d, the maintenance processing unit 198 is separately provided for each maintenance target. Composed. Further, the maintenance processing control unit 197 is provided for each maintenance processing unit. 20 includes a motor 188, a pump 196, and the like.

  The print control unit 182 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 178 in accordance with the control of the system controller 177. The generated print data This is a control unit that supplies (dot data) to the head driver 184. The print control unit 182 performs necessary signal processing, and controls the ejection droplet amount (droplet ejection amount) and ejection timing of the head 160 via the head driver 184 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  In FIG. 20, a plurality of heads (inkjet heads) provided in the inkjet recording apparatus 100 are represented by reference numeral 160. For example, the head 160 shown in FIG. 20 includes the permeation inhibitor head 130, the treatment liquid head 136, the ink heads 140C, 140M, 140Y, and 140K, and the transparent UV ink head 146 shown in FIG.

  The print control unit 182 is provided with an image buffer memory 183, and image data, parameters, and other data are temporarily stored in the image buffer memory 183 when image data is processed in the print control unit 182. Also possible is an aspect in which the print controller 182 and the system controller 177 are integrated and configured with one processor.

  An outline of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 176 and stored in the memory 178. At this stage, for example, RGB multi-valued image data is stored in the memory 178. The original image (RGB) data stored in the memory 178 is sent to the print control unit 182 via the system controller 177, and the print control unit 182 uses the halftoning process using a threshold matrix, an error diffusion method, etc. It is converted into dot data (binary data or multi-value data including dot size information) for each color (K, C, M, Y).

  Thus, the dot data generated by the print control unit 182 is stored in the image buffer memory 183. The dot data for each color is converted into CMYK droplet ejection data for ejecting ink from the nozzles of the head 160, and the ink ejection data to be printed is determined.

  The head driver 184 generates a drive signal to be applied to the piezoelectric element 168 of the head 160 based on the image data (dot data) given from the print control unit 182, and applies the drive signal to the piezoelectric element 168 to apply piezoelectricity. A driving circuit for driving the element 168 is included. The head driver 184 shown in FIG. 20 may include a feedback control system for keeping the driving conditions of the head 160 constant.

  As described with reference to FIG. 1, the print detection unit 144 is a block including a line sensor. The print detection unit 144 reads an image printed on the recording medium 114, performs necessary signal processing, etc. And the detection result is provided to the print control unit 182.

  The print control unit 182 performs various corrections to the head 160 based on information obtained from the print detection unit 144 as necessary, and performs cleaning operations (nozzle recovery operation) such as preliminary ejection, suction, and wiping as necessary. Perform the controls to be implemented.

  In addition, a configuration (recording medium detection sensor) similar to the print detection unit 144 is provided in the front stage of the transfer drum 124a in FIG. 1, and the thickness and surface property of the recording medium 114 are read using the recording medium detection sensor. A mode in which the type of the recording medium 114 is determined based on the information is also preferable.

  A sensor 185 in FIG. 20 indicates various sensors provided in each unit in the apparatus. The sensor 185 includes a paper floating sensor 504, a temperature sensor, a position detection sensor, a pressure sensor, and the like. The output signal of the sensor 185 is sent to the system controller 177, and the system controller 177 sends a control signal to each part of the apparatus based on the output signal, thereby controlling each part of the apparatus.

<Image Forming Method Using Inkjet Recording Device>
Next, an image forming method using the inkjet recording apparatus 100 configured as described above will be described.

  The recording medium 114 is sent out from the paper feed tray 120 of the paper feed unit 102 shown in FIG. The recording medium 114 is held on the pressure drum 126a of the permeation suppression processing unit 104 via the transfer drum 124a, preheated by the paper preheating unit 128, and the permeation suppression agent is ejected by the permeation suppression agent head 130. Thereafter, the recording medium 114 held on the impression cylinder 126a is heated by the permeation suppression agent drying unit 132, and the solvent component (liquid component) of the permeation suppression agent is evaporated and dried.

  The recording medium 114 thus subjected to the permeation suppression process is transferred from the pressure drum 126a of the permeation suppression processing unit 104 to the pressure drum 126b of the treatment liquid application unit 106 via the transfer cylinder 124b. The recording medium 114 held on the impression cylinder 126 b is preheated by the paper preheating unit 134 and the processing liquid is ejected by the processing liquid head 136. Thereafter, the recording medium 114 held on the pressure drum 126b is heated by the treatment liquid drying unit 138, and the solvent component (liquid component) of the treatment liquid is evaporated and dried. Thereby, a solid or semi-solid aggregation treatment agent layer is formed on the recording medium 114.

  The recording medium 114 to which the treatment liquid has been applied to form a solid or semi-solid aggregation processing agent layer is transferred from the impression cylinder 126b of the treatment liquid application section 106 to the impression cylinder 126c of the printing section 108 via the transfer cylinder 124c. Is passed on. Corresponding color inks are ejected from the ink heads 140C, 140M, 140Y, and 140K to the recording medium 114 held on the impression cylinder 126c in accordance with the input image data.

  When the ink droplet lands on the aggregation treatment agent layer, the contact surface between the ink droplet and the aggregation treatment agent layer lands in a predetermined area due to the balance between the flight energy and the surface energy. The aggregation reaction starts immediately after the ink droplets land on the aggregation treatment agent, but the aggregation reaction starts from the contact surface between the ink droplets and the aggregation treatment agent layer. The agglomeration reaction occurs only in the vicinity of the contact surface, and the color material in the ink is agglomerated in a state where the adhesive force is obtained with a predetermined contact area at the time of ink landing, so that the color material movement is suppressed.

  Even if other ink droplets land adjacent to this ink droplet, the color material of the ink that has landed first is already agglomerated, so the color materials do not mix with the ink that landed later, Bleed is suppressed. Note that after the color material is aggregated, the separated ink solvent spreads, and a liquid layer in which the aggregation treatment agent is dissolved is formed on the recording medium 114.

  The recording medium 114 held on the impression cylinder 126c is heated by the solvent drying units 142a and 142b, and the solvent component (liquid component) separated from the ink aggregates on the recording medium 114 is evaporated and dried. As a result, curling of the recording medium 114 can be prevented and image quality deterioration due to the solvent component can be suppressed.

  The recording medium 114 to which the color ink is applied by the printing unit 108 is transferred from the impression cylinder 126c of the printing unit 108 to the impression cylinder 126d of the transparent UV ink application unit 110 via the transfer cylinder 124d. The recording medium 114 held on the impression cylinder 126d is subjected to the transparent UV ink so that the transparent UV ink head 146 overlaps the color ink on the recording medium 114 after the printing result of the printing unit 108 is read by the printing detection unit 144. Dropped.

  Subsequently, when the recording medium 114 held on the impression cylinder 126d passes through the position facing the first UV lamps 148a and 148b, the UV light is transparent on the recording medium 114 by the first UV lamps 148a and 148b. Irradiated to UV ink. Thereby, the transparent UV ink on the recording medium 114 has a high viscosity at the interface with the recording medium 114, and the penetration of the transparent UV ink into the recording medium 114 is suppressed.

  Further, after that, the recording medium 114 is transferred from the pressure drum 126 d to the paper discharge drum 150 and passes through a position facing the second UV lamp 156 when being conveyed to the paper discharge tray 152 by the paper discharge chain 154. At this time, the UV light is applied to the transparent UV ink on the recording medium 114 by the second UV lamp 156. As a result, the transparent UV ink on the recording medium 114 is cured from the surface to the inside.

  When the transparent UV ink is applied on the recording medium 114 in the transparent UV ink application unit 110, the layer thickness of the transparent UV ink after UV light irradiation is 5 μm or less (preferably 3 μm or less, more preferably 1 to 3 μm). Thus, the droplet ejection amount of the transparent UV ink head 146 is controlled. Therefore, a thin film layer (transparent UV coat layer) made of transparent UV ink is formed so as to cover the color ink on the recording medium 114 by the UV light irradiation by the first UV lamps 148a and 148b and the second UV lamp 156. A glossy image similar to offset printing is realized on the recording medium 114.

  The recording medium 114 on which the image has been formed in this manner is transported above the paper discharge table 152 by the paper discharge chain 154 and stacked on the paper discharge table 152.

<Operation control example when paper lift is detected>
FIG. 21 is a flowchart illustrating an example of control at the time of paper floating detection of the ink jet recording apparatus according to the present embodiment. In accordance with the conveyance of the recording medium 114 due to the start of the print job, monitoring of the sheet floating by the sheet floating sensor 504 is started (step S210). Based on the detection signal obtained from the light receiver 514, it is determined whether or not a sheet lift exceeding a specified amount has been detected (step S212).

  If sheet lift is detected and a YES determination is made in step S212, the drum (pressure drum 126c) is stopped (step S214). At this time, it is possible to reliably prevent the recording medium 114 from contacting the head 160 by stopping the impression cylinder 126c before the portion of the recording medium 114 in which the lifting exceeding the specified amount is detected passes through the paper guide 506. Can do. Further, in order to obtain such effects, the installation position of the paper guide 506 (the angular position in the drum circumferential direction from the most upstream ink head 140C) and the height of the paper guide 506 (the amount of clearance between the surface of the impression cylinder 126c). ) Is designed.

  For example, even if the rear end portion of the recording medium 114 is lifted from the impression cylinder 126c and stopped, the recording medium 114 comes into contact with the paper guide 506, and further lifting is restricted. Contact of the recording medium 114 can be prevented.

  In this way, the head 160 is retracted from the printing position (position facing the impression cylinder 126c) to a predetermined maintenance position outside the impression cylinder 126c in the axial direction of the impression cylinder 126c, while avoiding contact between the recording medium 114 and the head 160. (Step S216). Then, a warning for prompting the user to remove the jammed paper is notified (step S218). The warning means is not particularly limited, such as displaying a warning message on a display means such as a display of the host computer 186 or a display in a control device (not shown), outputting a warning sound by the voice output means, and outputting a warning message. There are aspects.

  After outputting the warning, the process proceeds to step S220, and it is determined whether or not the jammed paper removal operation is completed. When the completion of the work by the user (operator) is automatically detected by the sensor, or the user (operator) performs the work of removing the jammed paper and performs a predetermined operation (for example, operation of the work completion button) after the work is completed. Step S220 is YES, and the process proceeds to Step S222.

  In step S222, an operation of discharging another sheet (recording medium 114) that is stopped in the middle of conveyance in the apparatus is performed. That is, the ink jet recording apparatus 100 of the present example has a mode (forced paper discharge mode) in which the impression cylinders 126a to 126d and the transfer cylinders 124a to 124d are rotated even when the sheet floating is detected.

  Only when the head 160 is not at the print position (when the head 160 is retracted to the maintenance position), the forced discharge mode can be shifted to the above-described forced discharge mode even when the sheet lift is detected. This mode is entered in the jam clearing sequence, and the currently transported paper (recording medium 114) stopped in the apparatus can be forcibly discharged, and the return operation from the detection of paper floating can be performed quickly.

  In step S222, after all the paper that has been stopped in the middle of conveyance in the apparatus has been discharged, the head 160 is moved to the printing position (step S224). In this way, it returns to the printable state, and it is determined whether or not to resume printing (step S226). If the determination is YES in step S226 by the input of a restart instruction by the user (operator) or an automatic start program, printing is resumed and the process returns to step S212.

  On the other hand, in step S226, if NO is determined in step S226 by the input of a print end instruction by the user (operator) or an automatic end program, the process is ended (step S230).

  According to the ink jet recording apparatus 100 of this example, it is possible to avoid jamming of the recording medium 114 to the head 160 and quickly return to jam.

<Modification 1 of Embodiment>
In FIG. 1, the sheet pressing roller 502 is used as the sheet pressing unit. However, instead of or in combination with this, air is blown to the recording medium 114 so that the recording medium 114 adheres to the outer peripheral surface of the impression cylinder 126 c. You may let them. FIG. 22 shows a configuration provided with an air blowing device 562 having an air generating portion 562A and an ejection nozzle 562B as a sheet restraining means. 22, elements that are the same as or similar to those in FIG. 5 are given the same reference numerals, and descriptions thereof are omitted. The air generating unit 562A of this example is configured by arranging a plurality of fans (airflow generating means) along the drum axial direction of the impression cylinder 126c. An airflow is blown from the ejection nozzle 562B to the entire width region of the recording medium 114, and the recording medium 114 is pressed against the surface of the impression cylinder 126c by the force of the air.

<Modification 2 of Embodiment>
In FIG. 1, the inkjet recording apparatus 100 (single-sided machine) that performs printing on only one side of the recording medium 114 has been described. However, the present invention can also be applied to an apparatus for double-sided printing (double-sided machine).

  FIG. 23 is a configuration diagram of an inkjet recording apparatus 200 for double-sided printing. In FIG. 23, elements that are the same as or similar to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

  An inkjet recording apparatus 200 shown in FIG. 23 is a double-sided machine that can print on both sides of a recording medium 114. The inkjet recording apparatus 200 includes, in order from the upstream side in the conveyance direction of the recording medium 114 (the direction from right to left in FIG. 23), the paper feeding unit 102, the first permeation suppression processing unit 104A, and the first processing. Liquid applying unit 106A, first printing unit 108A, first transparent UV ink applying unit 110A, reversing unit 202 for reversing the recording surface (image forming surface) of recording medium 114, and second permeation suppression A processing unit 104B, a second processing liquid application unit 106B, a second printing unit 108B, a second transparent UV ink application unit 110B, and a paper discharge unit 112 are provided. That is, it corresponds to a configuration in which the permeation suppression processing unit 104, the treatment liquid application unit 106, the printing unit 108, and the transparent UV ink application unit 110 of the inkjet recording apparatus 100 shown in FIG. It is.

  In the ink jet recording apparatus 200 of this example, first, as in the ink jet recording apparatus 100 shown in FIG. 1, the first permeation suppression process is performed on one surface of the recording medium 114 fed from the paper feeding unit 102. 104A, first treatment liquid application unit 106A, first printing unit 108A, and first transparent UV ink application unit 110A, permeation suppression processing, treatment liquid droplet ejection, color ink droplet ejection, transparent UV ink The droplets are sequentially ejected.

  After an image is formed on one surface of the recording medium 114 in this way, the recording medium 114 is transferred from the impression cylinder 126d of the first transparent UV ink application unit 110A to the reversal cylinder 204 via the transfer cylinder 206. When recording is performed, the recording medium 114 is reversed. Note that since a known mechanism may be applied as the reversing mechanism of the recording medium 114, a detailed description thereof will be omitted. Further, a second UV lamp 156 is provided at a position facing the surface of the reversing cylinder 204, and on the recording medium 114 together with the first UV lamps 148a and 148b of the first transparent UV ink application unit 110A. It plays the role of curing the transparent UV ink applied to the.

  The inverted recording medium 114 is transferred from the reversing cylinder 204 via the transfer cylinder 208 to the impression cylinder 126a of the second permeation suppression processing unit 104B. Then, with respect to the other surface of the recording medium 114, the second permeation suppression processing unit 104B, the second treatment liquid application unit 106B, the second printing unit 108B, and the second transparent UV ink application unit 110B are used. A permeation suppression process, a droplet of a treatment liquid, a droplet of colored ink, a droplet of transparent UV ink, and the like are sequentially performed.

  After the images are formed on both sides of the recording medium 114 in this way, the recording medium 114 is conveyed above the paper discharge table 152 by the paper discharge chain 154 and stacked on the paper discharge table 152.

<Specific Examples of Permeation Inhibitor, Ink, and Treatment Liquid>
Specific examples of the penetration inhibitor, the treatment liquid, and the ink used in the embodiment of FIGS. 1 and 23 are shown below.

<Penetration inhibitor>
A mixed solution of 10 g of dispersion stabilizing resin [Q-1] having the following structure, 100 g of vinyl acetate, and 384 g of Isopar H (trade name of Exxon) was heated to a temperature of 70 ° C. while stirring in a nitrogen stream. As a polymerization initiator, 2,2′-azobis (isovaleronitrile) (abbreviation AIVN) 0.8 g was added and reacted for 3 hours. 20 minutes after the addition of the initiator, white turbidity occurred, and the reaction temperature rose to 88 ° C. Further, 0.5 g of the initiator was added and reacted for 2 hours, and then the temperature was raised to 100 ° C. and stirred for 2 hours to distill off unreacted vinyl acetate. After cooling, it was passed through a 200-mesh nylon cloth, and the resulting white dispersion was a latex with a good monodispersity having a polymerization rate of 90% and an average particle size of 0.23 μm. The particle size was measured with CAPA-500 (manufactured by Horiba, Ltd.).

A portion of the white dispersion is centrifuged (rotation speed: 1 × 10 ⁴ rpm, rotation time: 60 minutes) to collect and dry the settled resin particles, and the weight of the resin particles When the average molecular weight (Mw), glass transition point (Tg), and minimum film-forming temperature (MFT) were measured, Mw was 2 × 105 (polystyrene equivalent GPC value), Tg was 38 ° C., and MFT was 28 ° C.
The penetration inhibitor solution thus prepared was applied onto the recording paper. At the time of application, the recording paper was heated by a drum, and after application, hot air was blown to evaporate Isopar H.

<About ink>
The ink used in the practice of the present invention is a water-based pigment ink containing a pigment that is a coloring material (coloring agent) or polymer fine particles as a solvent-insoluble material.

The concentration of the solvent-insoluble material is preferably 1 wt% or more and 20 wt% or less considering a viscosity of 20 mPa · s or less suitable for ejection. More preferably, the pigment concentration is 4 wt% or more in order to obtain the optical density of the image.
The surface tension of the ink is preferably 20 mN / m or more and 40 mN / m or less in consideration of ejection stability.

  The color material used in the ink can be a pigment or a mixture of a dye and a pigment. From the viewpoint of aggregability at the time of contact with the treatment liquid, a pigment in a dispersed state in the ink is preferable because it aggregates more effectively. Among the pigments, a pigment dispersed by a dispersant, a self-dispersing pigment, a pigment whose surface is coated with a resin (microcapsule pigment), and a polymer graft pigment are particularly preferable. From the viewpoint of pigment aggregation, a form modified with a carboxyl group having a low dissociation degree is more preferable.

  The resin of the microcapsule pigment is not limited, but is preferably a high molecular compound having a self-dispersibility or solubility in water and an anionic group (acidic). This resin usually has a number average molecular weight of about 1,000 to 100,000, and particularly preferably about 3,000 to 50,000. Further, it is preferable that this resin is dissolved in an organic solvent to form a solution. When the number average molecular weight of the resin is within this range, the function as a coating film in the pigment or as a coating film in the ink composition can be sufficiently exhibited.

  The resin may be self-dispersible or soluble, or may have a function added by some means. For example, it may be a resin in which an anionic group such as a carboxyl group, a sulfonic acid group, or a phosphonic acid group is introduced by neutralization with an organic amine or an alkali metal. Further, it may be a resin into which one or two or more anionic groups of the same type or different types are introduced. In the present invention, a resin in which a carboxyl group is introduced by neutralization with a base is preferably used.

  Although it does not specifically limit as a pigment used for this invention, As a specific example, as a pigment for orange or yellow, C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185. Examples of red or magenta pigments include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  In the colored ink liquid according to the present invention, it is preferable to add polymer fine particles not containing a colorant as a component that reacts with the treatment liquid. The polymer fine particles can enhance the thickening action and aggregation action of the ink by reaction with the treatment liquid, and can improve the image quality. In particular, a highly safe ink can be obtained by incorporating anionic polymer fine particles into the ink.

  By using polymer fine particles that react with the treatment liquid and cause thickening and aggregating action in the ink, the quality of the image can be improved. At the same time, depending on the type of polymer fine particles, the polymer fine particles form a film on the recording medium. It also has the effect of improving the scratch resistance and water resistance of the image.

  The dispersion method in the polymer ink is not limited to emulsion, and it may be dissolved or exist in a colloidal dispersion state.

  The polymer fine particles may be obtained by dispersing the polymer fine particles using an emulsifier, or may be dispersed without using an emulsifier. As the emulsifier, a low molecular weight surfactant is usually used, but a high molecular weight surfactant can also be used as an emulsifier. It is also preferable to use capsule type polymer fine particles (core / shell type polymer fine particles having different compositions at the center and outer edge of the particle) whose outer shell is made of acrylic acid, methacrylic acid or the like.

  As a dispersion method, polymer fine particles not using a low molecular weight surfactant are called soap-free latex, including polymer fine particles using a high molecular weight surfactant and polymer fine particles not using an emulsifier. For example, a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group described above (a polymer in which a solubilizing group is graft-bonded, a monomer having a solubilizing group, and an insoluble portion) Polymer fine particles using a block polymer obtained from a monomer as an emulsifier are also included.

  In the present invention, it is particularly preferable to use this soap-free latex, and the soap-free latex inhibits the reaction aggregation and film formation of the polymer fine particles or releases the emulsifier compared to the polymer fine particles polymerized using a conventional emulsifier. However, it moves to the surface after the formation of the polymer fine particles, and there is no concern that the adhesiveness between the aggregate in which the pigment and the polymer fine particles are mixed and the recording medium is lowered.

  Examples of the resin component added to the ink as polymer fine particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, and the like.

  From the viewpoint of imparting high-speed cohesiveness to the polymer fine particles, those having a carboxylic acid group having a low dissociation degree are more preferable. Since the carboxylic acid group is easily affected by pH change, the dispersion state is easily changed and the cohesiveness is high.

  The change of the dispersion state with respect to the pH change of the polymer fine particles can be adjusted by the content ratio of the constituent component in the polymer fine particles having a carboxylic acid group such as an acrylate ester, and the like depending on the anionic surfactant used as the dispersant. Can also be adjusted.

  The resin component of the polymer fine particles is preferably a polymer having both a hydrophilic portion and a hydrophobic portion. By having the hydrophobic portion, the hydrophobic portion is oriented inside the polymer fine particle, the hydrophilic portion is efficiently oriented outside, and the effect of increasing the dispersion state with respect to the pH change of the liquid is greater, and aggregation is caused. Done more efficiently.

  Examples of commercially available polymer fine particles include Jonkrill 537, 7640 (styrene-acrylic resin emulsion, manufactured by Johnson Polymer Co., Ltd.), Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, Nippon Paint Co., Ltd.). Manufactured), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), SAE-1014 (styrene-acrylic resin) Emulsion, manufactured by Nippon Zeon Co., Ltd., Jurimer ET-410, FC-30 (acrylic resin emulsion, manufactured by Nippon Pure Chemicals Co., Ltd.), Aron HD-5, A-104 (acrylic resin emulsion, manufactured by Toagosei Co., Ltd.) ), Cybino Le SK-200 (acrylic resin emulsion, manufactured by Saiden Chemical Industry Co., Ltd.), Zaikthene L (acrylic resin emulsion, manufactured by Sumitomo Seika Chemicals Co., Ltd.) and the like, not limited to this.

  The weight ratio of the polymer fine particle addition amount to the pigment is preferably 2: 1 to 1:10, more preferably 1: 1 to 1: 3. If the weight ratio of the amount of polymer fine particles added to the pigment is less than 2: 1, the cohesive force of the aggregate due to resin fusion will not be improved effectively. Moreover, even if the addition amount is more than 1:10, the viscosity of the ink becomes too high, and the discharge properties and the like deteriorate.

  The molecular weight of the polymer fine particles added to the ink is preferably 5,000 or more in view of the adhesive force when fused. If it is less than 5,000, the effect of improving the internal cohesive force of the ink aggregate when aggregated, fixing the image on the recording medium, and the effect of improving the image quality are insufficient.

  The volume average particle diameter of the polymer fine particles is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 to 500 nm, still more preferably in the range of 20 to 200 nm, and particularly preferably in the range of 50 to 200 nm. If the thickness is 10 nm or less, the effect of improving the image quality and the improvement of transferability cannot be expected even if they are aggregated. When the thickness is 1 μm or more, there is a concern that the ejection property of the ink from the head and the storage stability are deteriorated. Moreover, there is no restriction | limiting in particular regarding the volume average particle diameter distribution of a polymer particle, What has a wide volume average particle diameter distribution or a thing with a monodispersed volume average particle diameter distribution may be sufficient.

  Further, two or more kinds of polymer fine particles may be mixed and used in the ink.

  As the pH adjuster added to the ink of the present invention, an organic base or an inorganic alkali base can be used as a neutralizing agent. The pH adjusting agent is preferably added so that the inkjet ink has a pH of 6 to 10 for the purpose of improving the storage stability of the inkjet ink.

  The ink of the present invention preferably contains a water-soluble organic solvent for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water-soluble organic solvents include wetting agents and penetrants.

  Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, sulfur-containing solvents and the like, as in the case of the treatment liquid. Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, and glycerin. Examples of polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and diglycerin. Examples include ethylene oxide adducts. Examples of nitrogen-containing solvents include pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, and triethanolamine. Examples of alcohols include alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like. In addition, propylene carbonate, ethylene carbonate, or the like can be used.

  The ink of the present invention can contain a surfactant.

  Examples of surfactants include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonate formalin condensates, Anionic surfactants such as oxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines Nonionic surfactants such as glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Further, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used. In addition, fluorine (fluorinated alkyl) and silicone surfactants as described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also used. Can do. These surface tension modifiers can also be used as antifoaming agents, and fluorine-based, silicone-based compounds, chelating agents represented by EDTA, and the like can also be used.

  The surface tension can be lowered to increase the wettability on the solid or semi-solid solution aggregation treatment agent layer, and the spreading rate can be increased.

  The surface tension of the ink of the present invention is preferably 10 to 50 mN / m, and from the viewpoint of compatibility between the permeability to the permeable recording medium, the formation of fine droplets, and the ejection property, 15 to 45 mN. More preferably, it is / m.

  The viscosity of the ink of the present invention is preferably 1.0 to 20.0 cP.

  In addition, a pH buffer, an antioxidant, a fungicide, a viscosity modifier, a conductive agent, an ultraviolet absorber, and the like can be added as necessary.

<About treatment liquid>
The treatment liquid (aggregation treatment liquid) used in the practice of the present invention is preferably a treatment liquid that causes aggregation of pigments and polymer fine particles contained in the ink by changing the pH of the ink.

  Treatment liquid components include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone It is preferably selected from carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof.

  A preferable example of the treatment liquid according to the present invention is a treatment liquid to which a polyvalent metal salt or polyallylamine is added. These compounds may be used alone or in combination of two or more.

  The treatment liquid according to the present invention preferably has a pH of 1 to 6, more preferably 2 to 5, and particularly preferably 3 to 5 from the viewpoint of pH aggregation performance with the ink. .

  In the treatment liquid according to the present invention, the addition amount of the component for aggregating the pigment and polymer fine particles of the ink is preferably 0.01% by weight or more and 20% by weight or less with respect to the total weight of the liquid. When the amount is 0.01% by weight or less, concentration dispersion does not proceed sufficiently when the treatment liquid and the ink are in contact with each other, and an agglomeration effect due to pH change may not occur sufficiently. On the other hand, if it is 20% by weight or more, the dischargeability from the ink jet head may deteriorate.

  The treatment liquid according to the present invention preferably contains water and other additive-soluble organic solvents for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water and other additive-soluble organic solvents include wetting agents and penetrants.

  These solvents can be used alone or in combination with water and other additives.

  The content of water and other additive-soluble organic solvents is preferably 60% by weight or less based on the total weight of the treatment liquid. When the amount is more than 60% by weight or more, the viscosity of the treatment liquid increases, and the dischargeability from the inkjet head may deteriorate.

  The treatment liquid may further contain a resin component in order to improve fixability and abrasion resistance. The resin component may be any resin component that does not impair the ejection properties from the head when the treatment liquid is ejected by the ink jet method and has storage stability, and water-soluble resins and resin emulsions can be used freely.

  Examples of the resin component include acrylic, urethane, polyester, vinyl, and styrene. In order to sufficiently develop the function of improving the fixing property, it is necessary to add a relatively high polymer to a high concentration of 1% by weight to 20% by weight. However, if it is attempted to dissolve the above material in a liquid and add it, the viscosity becomes high, and the discharge property is lowered. In order to add an appropriate material at a high concentration and suppress an increase in viscosity, a means of adding as a latex is effective. Latex materials include alkyl acrylate copolymers, carboxy-modified SBR (styrene-butadiene latex), SIR (styrene-isoprene) latex, MBR (methyl methacrylate-butadiene latex), NBR (acrylonitrile-butadiene latex), and the like. Conceivable. The glass transition point Tg of the latex is a value that has a strong influence upon fixing in the process, and is preferably 50 ° C. or higher and 120 ° C. or lower in order to achieve both stability at room temperature storage and transferability after heating. Further, the minimum film-forming temperature MFT is a value that has a strong influence upon fixing in the process, and is 100 ° C. or lower, more preferably 50 ° C. or lower in order to obtain sufficient fixing at a low temperature.

  The coagulability may be further enhanced by including polymer fine particles having a polarity opposite to that of the ink in the treatment liquid and coagulating with the pigment and the polymer fine particles in the ink.

  In addition, a curing agent corresponding to the polymer fine particle component contained in the ink is contained in the treatment liquid, and after the two liquids contact, the resin emulsion in the ink component aggregates and crosslinks or polymerizes to increase the cohesiveness. Also good.

  The treatment liquid according to the present invention can contain a surfactant.

  Examples of surfactants include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonate formalin condensates, Anionic surfactants such as oxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines Nonionic surfactants such as glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Further, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used. In addition, fluorine (fluorinated alkyl) and silicone surfactants as described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also used. Can do. These surface tension modifiers can also be used as antifoaming agents, and fluorine-based, silicone-based compounds, chelating agents represented by EDTA, and the like can also be used.

  This is effective in reducing the surface tension and increasing the wettability on the recording medium. Further, even when ink is ejected in advance, the wettability on the ink is enhanced, and the cohesive action is effectively promoted by increasing the contact area of the two liquids.

  The surface tension of the treatment liquid according to the present invention is preferably 10 to 50 mN / m. From the viewpoint of coexistence of penetrability into a permeable recording medium, fine droplet formation, and dischargeability, 15 More preferably, it is -45 mN / m.

  The viscosity of the treatment liquid according to the present invention is preferably 1.0 to 20.0 cP.

  In addition, pH buffering agents, antioxidants, fungicides, viscosity modifiers, conductive agents, ultraviolet rays, absorbents, and the like can be added as necessary.

[Example of application to other device configurations]
In the above embodiment, the inkjet recording apparatuses 100 and 200 have been described as examples of the image forming apparatus. However, the scope of application of the present invention is not limited to this, and not only the inkjet system but also other laser recording systems, electrophotographic systems, and the like. The present invention can also be applied to an image forming apparatus of this type. For example, a thermal transfer recording apparatus having a recording head with a thermal element as a recording element, an LED electrophotographic printer having a recording head with an LED element as a recording element, and a silver salt photographic printer having an LED line exposure head. The present invention can also be applied to an image forming apparatus.

  In addition, in the interpretation of the term "image forming apparatus", it is not limited to the use of so-called graphic printing such as photographic printing or poster printing, such as a resist printing apparatus, a wiring drawing apparatus for an electronic circuit board, a fine structure forming apparatus, etc. An industrial use apparatus capable of forming a pattern that can be grasped as an image is also included.

<Appendix>
As will be understood from the description of the embodiments of the invention described in detail above, the present specification includes disclosure of various technical ideas including the invention described below.

  (Invention 1): Conveying means for conveying a recording medium, a recording head for forming an image on the recording medium conveyed by the conveying means, and the conveying direction of the recording medium by the conveying means rather than the recording head Light projecting means for irradiating inspection light passing through the entire width region of the recording medium in the width direction of the recording medium orthogonal to the transport direction on the upstream side, and the light projecting means sandwiching the recording medium in the width direction A light receiving means for receiving the inspection light emitted from the light projecting means and outputting a signal corresponding to the amount of received light, and provided in at least one of the light projecting means and the light receiving means. An image forming apparatus comprising: a slit that is long in the transport direction for restricting a passage range of the inspection light.

  According to the present invention, the lifting of the entire area of the recording medium can be accurately detected.

  "Recording media" includes various types of papers such as continuous paper, cut paper, sealing paper, resin sheets such as OHP sheets, printed boards on which films, cloths, wiring patterns and the like are formed, intermediate transfer media, and other materials and shapes. Includes media.

  The form of the conveying means includes a form such as a conveying drum (conveying roller) having a cylindrical shape and configured to be rotatable around a predetermined rotation axis, a conveying belt, and the like.

  (Invention 2): In the image forming apparatus according to Invention 1, the conveying unit is a drum disposed to face the recording head, and the recording medium is wound around a peripheral surface of the drum, and the drum is rotated. The image forming apparatus, wherein the recording medium is conveyed by the apparatus.

  In the case where the recording medium is curved and held along the drum peripheral surface (curved surface), there is a problem that the sheet is lifted by the force of the recording medium returning to the original state. Can be detected with high accuracy.

  (Invention 3): In the image forming apparatus according to Invention 2, the light projecting unit and the light receiving unit are arranged to face each other in the axial direction of the drum, and the slit is a drum tangent at a position where the inspection light passes. An image forming apparatus characterized in that the slit is long in the transport direction substantially equal to the direction.

  When a drum (cylinder) is used as the conveying means, a mode in which the light projecting means and the light receiving means are arranged in the drum axial direction and a long slit is arranged in the substantially drum tangential direction is preferable.

  (Invention 4): In the image forming apparatus according to any one of Inventions 1 to 3, there is provided a medium restraining means for restraining the recording medium toward a medium holding surface of the conveying means. An image forming apparatus, wherein the image forming apparatus is disposed upstream of the position where the light projecting unit and the light receiving unit are disposed.

  After the recording medium is held on the medium holding surface by the medium holding unit, the sheet floating detection is performed by the light detecting unit including the light projecting unit and the light receiving unit, so that stable detection is possible. As the medium restraining means, a roller member, air blowing means, or the like can be applied.

  (Invention 5): In the image forming apparatus according to any one of Inventions 1 to 4, the first adjustment mechanism for adjusting the position of the light projecting unit and the optical axis of the emitted light, the position of the light receiving unit, and An image forming apparatus comprising: a second adjustment mechanism that adjusts a direction of the light receiving surface.

  It is preferable that each of the light projecting unit and the light receiving unit includes an adjustment mechanism for adjusting the optical axis.

  (Invention 6): In the image forming apparatus according to any one of Inventions 1 to 5, the image forming apparatus includes a determination unit that determines a floating amount of the recording medium from a comparison between a signal obtained from the light receiving unit and a predetermined threshold value. An image forming apparatus, wherein the threshold setting is changed according to the thickness of the recording medium.

  According to this aspect, it is possible to keep the lift amount detected by the thickness of the recording medium constant.

  (Invention 7): In the image forming apparatus according to any one of Inventions 1 to 5, the image forming apparatus is installed corresponding to a plurality of detection heights having different positions in the height direction from the medium holding surface of the conveying unit. An image forming apparatus comprising a plurality of light projecting means and a plurality of light receiving means.

  According to this aspect, it is possible to detect with the same lifting amount with respect to recording media having different thicknesses.

  (Invention 8): A method of detecting the floating of the recording medium in an image forming apparatus that conveys the recording medium to the recording head and performs drawing on the recording medium by the recording head, wherein the recording is performed more than the recording head. A light projecting unit and a light receiving unit are arranged opposite to each other across the recording medium in the width direction of the recording medium orthogonal to the transport direction on the upstream side of the medium transport direction, and the light projecting unit and the light receiving unit. At least one of the means is provided with a slit that is long in the transport direction for restricting the passage range of the inspection light, the inspection light that passes through the full width region of the recording medium is irradiated from the light projecting means, and the light passes through the slit. The inspection light is received by the light receiving means to obtain a signal corresponding to the amount of received light, and the recording medium transporter is obtained based on the signal obtained from the light receiving means. Lifting detection method of the recording medium, characterized in that lifting detecting the from.

  According to the present invention, the lifting of the entire area of the recording medium can be accurately detected.

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. Plane perspective view showing a configuration example of the head shown in FIG. Sectional view along line 3-3 in FIG. 1 is a schematic diagram showing the configuration of an ink supply system of the ink jet recording apparatus shown in FIG. It is a principal part side view of the printing part in the inkjet recording device of this example. Plan view showing the configuration of the paper float sensor The perspective view which expanded the attachment part of the light receiver (or projector) Diagram showing an example of the slit shape The figure which shows the other form (comparative example) of a slit 8 is a graph showing a change in detection position due to an optical axis shift when the slit of FIG. 8 is used. FIG. 9 is a graph showing a change in detection position due to an optical axis shift when the slit of FIG. 9 is used. Graph showing the relationship between the amount of paper lift and the amount of light received FIG. 8 is a graph showing changes in the unstable detection region due to optical axis misalignment when the slit of FIG. FIG. 9 is a graph showing a change in an unstable detection region due to an optical axis shift when the slit of FIG. FIG. 8 is a graph showing changes in the unstable detection region depending on the height position of the projector / receiver when the slit of FIG. 8 is used. 9 is a graph showing changes in the detection unstable region depending on the height position of the projector / receiver when the slit of FIG. 9 is used. A perspective view showing a schematic structure of an impression cylinder (conveying drum) A partially enlarged view of FIG. Sectional drawing which follows the BB line in FIG. 1 is a principal block diagram showing the system configuration of the inkjet image recording apparatus shown in FIG. 7 is a flowchart illustrating a control example at the time of detection of paper floating in the inkjet recording apparatus according to the present embodiment. The principal part block diagram which shows other embodiment of this invention. The block diagram of the inkjet recording device (double-sided machine) which concerns on other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100,200 ... Inkjet recording device, 140C, 140M, 140Y, 140K, ... Head, 114 ... Recording medium, 126a-126d ... Impression cylinder, 502 ... Paper suppression roller, 512 ... Light projector, 514 ... Light receiver, 530 ... Adjustment mechanism 540 ... Slit

Claims (8)

Conveying means for conveying the recording medium;
A recording head for forming an image on the recording medium conveyed by the conveying means;
Light projecting means for irradiating inspection light passing through the entire width range of the recording medium in the width direction of the recording medium orthogonal to the transport direction on the upstream side of the transport direction of the recording medium by the transport means from the recording head When,
A light receiving means disposed on the opposite side of the light projecting means across the recording medium in the width direction, receiving the inspection light emitted from the light projecting means, and outputting a signal according to the amount of received light;
A slit that is provided in at least one of the light projecting means and the light receiving means, and that is long in the transport direction for restricting a passage range of the inspection light;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The transporting means is a drum arranged to face the recording head, the recording medium is wound around a peripheral surface of the drum, and the recording medium is transported by rotation of the drum. apparatus. The image forming apparatus according to claim 2.
The light projecting means and the light receiving means are arranged to face each other in the axial direction of the drum,
The image forming apparatus according to claim 1, wherein the slit is a slit that is long in the transport direction substantially equal to a drum tangential direction at a position where the inspection light passes. The image forming apparatus according to any one of claims 1 to 3,
Medium holding means for holding down the recording medium toward the medium holding surface of the conveying means is provided,
The image forming apparatus according to claim 1, wherein the medium holding unit is disposed upstream of the position in which the light projecting unit and the light receiving unit are disposed. The image forming apparatus according to any one of claims 1 to 4, wherein:
A first adjustment mechanism for adjusting the position of the light projecting means and the optical axis of the emitted light;
A second adjustment mechanism for adjusting the position of the light receiving means and the orientation of the light receiving surface;
An image forming apparatus comprising: The image forming apparatus according to any one of claims 1 to 5,
A determination means for determining the amount of lifting of the recording medium from a comparison between a signal obtained from the light receiving means and a predetermined threshold;
An image forming apparatus, wherein the threshold value is changed according to the thickness of the recording medium. The image forming apparatus according to any one of claims 1 to 5,
An image forming apparatus comprising: a plurality of light projecting units and a plurality of light receiving units installed corresponding to a plurality of detection heights having different height positions from a medium holding surface of the transport unit. apparatus. A method for detecting the floating of the recording medium in an image forming apparatus that conveys the recording medium to the recording head and performs drawing on the recording medium by the recording head,
The light projecting means and the light receiving means are arranged opposite to each other across the recording medium in the width direction of the recording medium perpendicular to the transport direction on the upstream side of the transport direction of the recording medium from the recording head.
At least one of the light projecting unit and the light receiving unit is provided with a long slit in the transport direction that restricts the inspection light passing range;
Irradiating the inspection light passing through the full width range of the recording medium from the light projecting means,
The inspection light that has passed through the slit is received by the light receiving means to obtain a signal corresponding to the amount of received light,
A method for detecting a lift of a recording medium, comprising: detecting the lift of the recording medium from a transport means based on a signal obtained from the light receiving means.

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