JP3685147B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention records the ink applied to the surface layer by heating the recording medium on which the ink is applied to the surface layer using a print head that is driven and controlled by print data created from color image data. The present invention relates to an image forming apparatus for fixing on a fixing layer of a medium.
[0002]
[Prior art]
As a printing technique for applying a recording medium to a printing liquid such as ink to obtain a printed material, for example, a primary image is first formed on a thermal transfer sheet by an inkjet printer or the like, and then the thermal transfer sheet on which the image is formed is recorded on the recording sheet The image (ink) formed on the thermal transfer sheet is subjected to thermal sublimation transfer to the ink fixing layer of the thermal transfer sheet to form a secondary image on the thermal transfer sheet. A thermal transfer technique for obtaining a printed material is well known from JP-A-10-16188.
In JP-A-10-230589, a laminate material layer is provided in advance on an ink fixing layer of a recording sheet, an image is formed on the laminate material layer with an ink jet printer or the like, and then pressed through a heating roller. A heat fixing printing technique is disclosed in which a laminate material layer is made transparent by heating and an ink dye is fixed to a fixing layer to obtain a printed matter.
[0003]
[Problems to be solved by the invention]
In such an image forming apparatus, a technique for fixing an ink forming an image by heating is very important because it greatly affects the quality of a printed product as a final product. In particular, when heat is applied to a sheet-like recording medium to fix an image, color unevenness occurs when the temperature distribution on the sheet becomes uneven in the heating process, resulting in a reduction in quality of the final product.
[0004]
For this reason, it is conceivable to apply a radiant heat beam generating mechanism such as infrared rays or far infrared rays as a heating device to apply heat gently and evenly over a recording medium to which ink is applied, not instantaneously but over time. It has been. Such a heating method can provide a uniform temperature distribution compared to a heating method using a heating roller that has been widely used in the past, but the heat absorption rate (light absorption rate) of each basic color that creates a color image is the same. However, when a radiant heat beam such as infrared rays or far infrared rays is used, there is a problem that heat of a specific color is relatively difficult to absorb (normally, yellow is cyan or cyan, depending on the spectrum distribution of the radiant beam used). Heat absorption is considered worse than magenta). That is, such a radiant heat beam exhibits different heat absorption characteristics with respect to the color of the ink, and an ink of a color that has not absorbed much radiant heat compared to the other colors has an insufficient fixing process, and is in comparison with others. Color development is inferior and color unevenness occurs.
In view of the above situation, an object of the present invention is to provide an image forming apparatus of the type described above, in which the occurrence of color unevenness is suppressed even when a radiant heat beam having different heat absorption characteristics for ink colors is used in a heating device. Is to provide.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the recording medium provided with ink on the surface layer is heated by using a print head that is driven and controlled by print data created from color image data. In an image forming apparatus for fixing ink on a fixing layer of a recording medium, in the present invention, a heating apparatus that heats the recording medium using a radiant heat beam that exhibits different heat absorption characteristics with respect to the color of the ink, and a color A heat absorptivity compensation correction unit that performs correction for compensating for the difference in the heat absorption rate of the radiant heat beam depending on the color when creating print data from the image data is provided.
[0006]
In this configuration, image data corresponding to a color with a different heat absorption rate compared to other colors, that is, by adjusting the density value of a specific color component, fixing color development based on a different heat absorption rate for each basic color Color unevenness caused as a result of the variation in condition can be compensated in advance at the stage of image data.
[0007]
Such adjustment rate (correction rate) for heat absorption rate compensation may be obtained from actual measurement data obtained by testing, or calculated based on spectral data of each color component of ink and spectral data of radiant heat beam. In any case, the correction coefficient as the adjustment ratio obtained in any case is stored in a rewritable heat absorption rate compensation lookup table. This heat absorption rate compensation lookup table is preferably prepared not only for one type, but also for each type of ink, type of radiant heat beam, and each time-varying stage.
[0008]
As one specific example of the heat absorption rate compensation, when the heat absorption rate of a specific color component (the color component constituting the print basic color) with respect to the radiant heat beam is lower than that of other color components, this specification in the image data is performed. It is proposed to increase the density value of the color components. Further, as another specific example of the heat absorption rate compensation, when the heat absorption rate of a specific color component with respect to the radiant heat beam is higher than that of the other color components, and as a result, the image has a high density in the finished stage. It is proposed to reduce the density value of this particular color component in the data. These two heat absorption rate compensation methods may be selected, for example, from the relationship with the dynamic range of the image data each time.
[0009]
In one preferred embodiment of the present invention, a heat absorption rate compensation mode in which color image data is corrected by the heat absorption rate compensation correction unit and a heat absorption rate non-compensation mode in which this correction is not performed are selectively switched. A mode selection unit is provided. If the image to be printed is a monotone printed with black ink, or if a recording medium that does not require heat fixing is selected, there is little or no need for heat absorption rate compensation. It becomes. Providing a mode selection function for selecting a heat absorption rate compensation mode and a heat absorption rate non-compensation mode in which this correction is not performed for such a case increases the versatility of the image forming apparatus.
Other features and advantages of the present invention will become apparent from the following description of embodiments using the drawings.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
First, an example of a recording medium 1 handled by the image forming apparatus according to the present invention will be described with reference to FIG. In this recording medium 1, a fixing layer 11 for ink, that is, a dye is formed on a surface of a base material 10 made of a film sheet such as PET (polyethylene terephthalate) with urethane resin or the like, and the ink is further permeated thereon. A surface layer 12 is formed as a permeation layer. When the surface of the substrate 10 has a property capable of fixing the dye, the fixing layer 11 can be omitted. After an ink droplet is applied to the surface layer 12 of the recording medium 1 by an ink jet printer or the like to form an image, when the ink droplet is heated to an appropriate temperature, the applied ink droplet penetrates the surface layer and fixes the fixing layer 11. The dye is fixed. Furthermore, by peeling off the surface layer 12, a very glossy and vivid image-recorded sheet can be obtained as the final printed matter 100. In this recording medium 1, since it is necessary to finally peel off the surface layer 12 from the fixing layer 11 or the substrate 10, it is convenient to provide an easy-release agent between them.
[0011]
An example of an image forming apparatus for producing the final printed matter 100 using such a recording medium 1 will be described with reference to FIGS. As shown in FIG. 2, the image forming apparatus includes a print station PS and an operating station OS.
[0012]
The print station PS includes an inkjet print unit IU, a heat fixing unit HU mounted on the paper discharge side of the inkjet print unit IU, and a housing that covers these units.
[0013]
As is apparent from FIG. 3, in the print station PS, the surface layer 12 as the print surface comes to the ink discharge port side of the ink jet head 2 as the print head while rewinding the recording medium 1 wound in a roll shape. Thus, the recording medium 1 is conveyed by the sheet conveying mechanism 6. The inkjet head 2 is supported so as to be reciprocally movable by a head feeding mechanism 3 in a direction transverse to the conveyance direction of the recording medium 1, that is, in the main scanning direction, and ink is ejected from the ejection port to the surface layer 12 of the recording medium 1. Each time the ink-jet head 2 is moved in the main scanning direction while being ejected, the recording medium 1 is conveyed in the sub-scanning direction, whereby print images are sequentially formed. A plurality of discharge port modules capable of discharging different main colors to form a color print image are prepared in the inkjet head 2. For example, when a photographic quality color print image is required, in general, dark and light inks of the same color are used in addition to inks such as cyan, magenta, yellow, and black. Since the inkjet head 2 mounted on a general-purpose inkjet printer is used, further explanation is omitted here.
[0014]
The recording medium 1 on which a print image is formed on the surface layer 12 by the ink droplets 2a ejected from the ink jet head 2 passes through the ink jet print unit IU and is formed by the heat fixing unit HU for heat fixing to the fixing layer 11 of the ink. Sent to the heated fixing area. A heating device 4 is provided in the heat fixing region.
[0015]
In the recording medium 1 that has passed through the heat fixing region, the ink (dye) forming the print image is fixed on the fixing layer 11, so that the surface layer 12 is peeled off to have a cleanly colored image. A final printed product 100 is obtained. Although a series of conveyance of the recording medium 1 is performed by the conveyance mechanism 6 shown here by a roller method, other conveyance methods such as a belt method may be adopted.
[0016]
Since the recording medium 1 that is originally a long sheet needs to be cut according to the size of a print image formed thereon, a sheet cutter means 5 is provided. In this embodiment, the sheet cutter means 5 includes a first sheet cutter 5 </ b> A attached to the inkjet head 2 and a second sheet cutter 5 </ b> B provided in a rear region in the conveying direction of the heating device 4. The first sheet cutter 5A has the blade 51 attached to the ink jet head 2, so that the recording medium 1 can be cut by driving the head feed mechanism 3, whereas the second sheet cutter 5B has its blade. A dedicated feeding mechanism 53 for reciprocating the 52 is provided.
[0017]
Therefore, when a plurality of print images are continuously formed, the recording medium 1 is cut by the first sheet cutter 5A at the rear end of the entire length, and each print image unit is cut by the second sheet cutter. When a single print image is formed at 5B, the recording medium 1 is cut into a print image size by the first sheet cutter 5A and sent to the heat fixing unit HU.
[0018]
The heating device 4 includes an infrared heater (including a far-infrared heater) 41 disposed in a heating space formed by a wall body 40 made of a heat insulating material, and the heating space is generated by a radiant heat beam emitted from the infrared heater 41. The recording medium 1 passing through the inside is heated. A temperature sensor 42 is also provided for controlling the temperature in the heating space, and the recording medium 1 is heated to about 180 ° C. in the heating space to heat and fix the sublimation ink. In order for the recording medium 1 to pass through the heating space, the transport mechanism 6 is provided with a pressure-feed type transport roller unit composed of a driving roller and a driven roller at a position sandwiching the heating space.
[0019]
In the recording medium 1 described above, the sublimation ink used in this embodiment starts sublimation at about 80 ° C., and becomes an optimum sublimation fixing state by heating at 180 ° C. for about 2 minutes. This sublimable ink can be easily sublimated at a temperature of about 170 ° C. to 200 ° C., and the fixing layer 12 is required by heating for about 1 minute at 200 ° C. and heating for about 5 minutes at 170 ° C. Fixing and coloring of the ink pigments is realized.
[0020]
The inkjet head 2, the head feed mechanism 3, the heating device 4, the sheet cutter means 5, the transport mechanism 6, and the like are comprehensively controlled by a controller 7. In order to grasp the position of the recording medium 1 conveyed by the conveyance mechanism 6, a sheet detection sensor 60 is installed at a predetermined position on the conveyance line formed by the conveyance mechanism 6, and the detection signal is also sent to the controller 7. The controller 7 of the image forming apparatus includes a first controller 7A on the operating station OS side and a second controller 7B on the print station PS side, and is connected to each other via a communication cable so that data can be exchanged. It can function like
[0021]
As shown in FIG. 2, the operating station OS includes a general-purpose computer 80 that also functions as the first controller 7A, a monitor 81, a keyboard 82, a mouse 83, and a developed silver salt film F. Film scanner 85 that photoelectrically converts images into color image data, and data holding media (CD, CD-R, or MO, and communication that consists of data communication lines as well as semiconductor media such as compact flash and smart media) And an image acquisition unit 84 (which is built in the computer 80 in this case) for extracting color image data from the medium. In this image forming apparatus, the color image data transferred to the first controller 7A through the film scanner 85 and the image acquisition unit 84 is sent to the second controller 7B as print data after being subjected to various data processing and printed. A print image is formed on the recording medium 1 at the station PS.
[0022]
The controller 7 includes a first controller 7A and a second controller 7B, each having a microcomputer system including a CPU, a ROM, a RAM, an I / O interface circuit, and the like as core members. As shown in FIG. In the first controller 7A, peripheral devices such as an image acquisition unit 84 and a film scanner 85 for sending image data are connected via an I / O interface circuit. In the second controller 7B, a peripheral device such as an image acquisition unit 84 is connected via an I / O interface circuit. Peripheral devices incorporated in the print station PS such as the inkjet head 2, the head feeding mechanism 3, the heating device 4, and the transport mechanism 6 are connected. The first controller 7A and the second controller 7B can transmit data via respective communication modules, and the image data subjected to image processing and correction processing in the first controller 7A is finally print data. Is transmitted to the second controller 7B via the communication modules 74a and 74b, and is used for applying sublimation ink to the recording medium 1.
[0023]
Each function by the controller 7 is created by hardware and / or software. However, here, if only the functional elements related to the present invention are mentioned, the image data transferred from the image data input unit 9 will be described. Difference in heat absorption rate of the radiant heat beam depending on the ink color that characterizes the present invention in addition to the general image correction processing such as color correction and head shading correction, the image processing unit 72 that performs resolution change and trimming, etc. A correction unit 90 that performs a correction process for a specific color to compensate, a correction table storage unit 92 that stores a correction table 91 used in the correction unit 90, and a specific correction table 91 that is required and the correction table Correction mode selection unit 93 for loading 91 from the correction table storage unit 92 to the correction unit 90, corrected A print data generation unit 73 that generates print data for the ink jet head 2 from the image data using a binarization technique such as error diffusion, and the ejection head by driving the ink jet head 2 based on the transferred print data Print control unit 75 for discharging ink droplets from the head, head feed control unit 76 for moving the inkjet head 2 in the main scanning direction simultaneously with driving of the inkjet head 2, and recording every time the inkjet head 2 moves in the main scanning direction Typical examples include a conveyance control unit 77 that intermittently feeds the medium 1 and sends the recording medium 1 to the heating device 4, and a heating control unit 78 that drives and controls the infrared heater 41 of the heating device 4 based on a detection signal from the temperature sensor 42. Is something.
[0024]
Next, how a captured image is formed on the recording medium 1 using color image data of the captured image read from the color negative film F using the film scanner 85 will be described with reference to a schematic flowchart of FIG.
[0025]
When the color negative film F is read by the film scanner 85, the CCD output signal of the film scanner 85 is amplified and AD converted and transferred to the image data input unit 71 as 12-bit RGB color image data (# 01). The color image data is subjected to typical correction as scanner data such as gamma correction in the image data input unit 71 and then sent to the image processing unit 72 (# 02). The image processing unit 72 performs resolution conversion corresponding to the finished print size on the color image data and trimming as necessary, converts the 12-bit data into 8-bit data, and delivers it to the correction unit 90 (# 03). .
[0026]
The correction unit 90 performs color correction processing normally performed in digital photographic prints and heat absorption rate compensation correction processing for a specific color to compensate for the difference in the heat absorption rate of the radiant heat beam depending on the ink color. All of these are performed using the correction table (lookup table) 91 loaded from the correction table storage unit 92 to the correction unit 90 (# 05) by address designation by the correction mode selection unit 93 (# 04).
[0027]
Among the basic ink colors used in the ink jet head 2, an ink color that is relatively difficult to absorb the radiant heat beam emitted from the infrared heater 41 of the heating device 4 is experimentally investigated in advance, and the relative heat absorption rate is determined. A heat absorptivity compensation correction table having a correction coefficient obtained from a specific height or height is created and stored in the correction table storage unit 92. As one simple method of creating the heat absorption rate compensation correction table, each color component is obtained by simulation or the like from the spectrum data for each color component of the ink used and the spectrum data of the radiant heat beam emitted from the infrared heater 41 used. It is also proposed to obtain a relative heat absorption coefficient, calculate a correction factor from this, and create a correction table.
[0028]
For example, when the yellow ink has a poor absorption of the radiant heat beam from the infrared heater 41 as compared with the inks of other colors, only the yellow ink applied to the recording medium 1 is not sufficiently sublimated in the same heating time. As a result, sufficient fixing, that is, color development at a sufficient density cannot be performed, and color unevenness occurs in the finished print. In order to prevent such a phenomenon, the density value of the yellow component in the color image data is corrected in advance by an appropriate value. Alternatively, correction that lowers the density values of the other color components without changing the density value of the yellow component may be employed. In that case, it is necessary to take measures such as slightly increasing the heating time or slightly increasing the heating temperature. Since such correction may reduce the dynamic range of the color image data, it is also advantageous to employ a configuration that selects a measure that does not lower the dynamic range as much as possible.
[0029]
A correction table used for such correction is referred to herein as a heat absorption rate compensation correction table. Therefore, when the heat absorption rate compensation correction table is designated by the correction mode selection unit 93 and loaded into the correction unit 90, the correction unit 90 functions as a heat absorption rate compensation correction unit. Of course, when a normal inkjet recording paper that does not need to be heat-fixed is used as the recording medium 1, this heat absorption rate compensation correction is performed by a correction mode selection unit 93 that can be operated by an operator using the keyboard 82 or the like. Omitted.
[0030]
When all necessary color image data correction is completed in the correction unit 90, the color image data is sent to the print data generation unit 73 (# 6). Since the RGB color image data is converted into CMYK color image data at an appropriate stage before and after other corrections in the correction unit 90, the color image data sent to the print data generation unit 73 is CMYK color image data.
[0031]
The print data generation unit 73 performs binarization processing for performing gradation formation by area gradation by the inkjet head 2 from the received 8-bit CMYK color image data, and generates binary CMYK print data, and the print control unit 75 (# 07).
[0032]
The print control unit 75 generates a drive pulse signal for the inkjet head 2 from the transferred binary CMYK print data, thereby controlling the drive element of the inkjet head 2 and spraying ink droplets onto the recording medium 1. (# 08). At the same time, the head feed control unit 75 controls the head feed mechanism 3 and the transport control mechanism 77 controls the transport mechanism, whereby a photographic image is formed on the recording medium 1 (# 08). The recording medium 1 on which the photographed image is formed is heated and fixed through the heating device 4.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of a recording medium handled by an image forming apparatus according to the present invention. FIG. 2 is an external view illustrating an embodiment of an image forming apparatus according to the present invention. FIG. 4 is a functional block diagram for explaining the function of the controller. FIG. 5 is a diagram illustrating how the input image data is corrected and then sent to the inkjet head as print data. Schematic flow diagram showing how it is formed 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 Recording medium 2 Inkjet head 3 Head feed mechanism 4 Heating device 6 Conveyance mechanism 7 Controller 7A 1st controller 7B 2nd controller 41 (far) Infrared heater 72 Image processing part 73 Print data generation part 75 Print control part 90 Correction | amendment part ( Heat absorption rate compensation correction part)
91 Correction table (heat absorption rate compensation correction table)
92 Correction table storage unit 93 Correction mode selection unit

Claims (5)

Using a print head that is driven and controlled by print data created from color image data, the recording medium with the ink applied to the surface layer is heated to cause the ink applied to the surface layer to be fixed to the recording medium. In the image forming apparatus to be fixed to
A heating device that heats the recording medium using a radiant heat beam that exhibits different heat absorption characteristics with respect to the color of the ink, and a color-dependent radiant heat beam coverage when generating print data from the color image data. An image forming apparatus comprising: a heat absorption coefficient compensation correction unit that performs correction for compensating for a difference in heat absorption coefficient. The image forming apparatus according to claim 1, wherein the heat absorptivity compensation correction unit increases a density value of a color component whose heat absorptivity for the radiant heat beam is lower than other color components. 3. The image forming apparatus according to claim 1, wherein the heat absorptivity compensation correction unit reduces a density value of a color component having a heat absorptivity for the radiant heat beam higher than that of other color components. The heat absorption coefficient compensation correction unit has a rewritable heat absorption coefficient compensation lookup table that stores correction data calculated based on spectrum data of each color component of the ink and spectrum data of the radiant heat beam. The image forming apparatus according to any one of claims 1 to 3. A mode selection unit that selectively switches between a heat absorption rate compensation mode in which color image data correction is performed by the heat absorption rate compensation correction unit and a heat absorption rate non-compensation mode in which this correction is not performed is provided. The image forming apparatus according to claim 1.

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